Giáo trình tiếng anh trong kỹ thuật hóa học phần 2

The specific properties of petroleum products are decided by the predominance of some or other group of hydrocarbons in crude petroleum and by the presence of compounds containing sullur

UNIT 23 ADSORPTION

Adsorption is a separation process in which certain components of a fluid phase are transferred to the surface of a solid adsorbent Usually the small particles of adsorbent are held in a fixed bed, and fluid is passed continuously through the bed until the solid is nearly saturated and the desired separation can no longer be achieved The flow is then switched to a second bed until the saturated adsorbent can be replaced or regenerated Ion exhange is another process that is usually carried out in this semibatch fashion in a fixed bed Water that

is to be softened or deionized is passed over beads of ion-exchange resin in a column until the resin becomes nearly saturated The removal of trace impurities by reaction with solids can also be carried out in fixed beds, and the removal of H2S from synthesis gas with ZnO pellets

is a well-known example For all these processes, the performance depends on solid-fluid equilibria and on mass-transfer rates In this chapter the emphasis is on adsorption, but the general methods of analysis and design are applicable to other fixed-bed processes

ADSORBENTS AND ADSORPTION PROCESSES Most adsorbents are highly porous materials, and adsorption takes place primarily on the walls of the pores or at specific sites inside the particle Because the pores are generally very small, the internal surface area is orders of magnitude greater than the external area and may be as large as 2000 m2/g- Separation occurs because differences in molecular weight, shape, or polarity cause some molecules to be held more strongly on the surface than others or because the pores are too small to admit the larger molecules In many cases, the adsorbing components (or adsorbate)

is held strongly enough to permit complete removal of that component from the fluid with very little adsorption of other components Regeneration of the adsorbent can then be carried out to obtain the adsorbate in concentrated or nearly pure form

Applications of vapor-phase adsorption include the recovery of organic solvents used

in paints, printing inks, and solutions for film casting or fabric coating The solvent-laden air may first be sent to a water-cooled or refrigerated condenser to collect some of the solvent, but it is generally impractical to cool the gas far below ambient temperature in an attempt to eliminate solvent losses The air with a small amount of solvent is passed through a bed of carbon adsorbent particles, which can reduce the solvent concentration to less than 1 ppm The concentration may be set by government emission standards rather than by the economics

of solvent recovery Adsorption on carbon is also used to remove pollutants such as H2S, CS2

and other odorous compounds from air circulating in ventilation systems, and canisters of carbon are placed in most new automobiles to prevent gasoline vapors from being vented to the air

Drying of gases is often carried out by adsorbing the water on silica gel, alumina, or other inorganic porous solids The zeolites, or molecular sieves, which are natural or synthetic aluminosilicates with a very regular, fine pore structure, are especially effective in preparing gases with low dew points ( — 75°C) Adsorption on molecular sieves can also be used to separate oxygen and nitrogen, to prepare pure hydrogen for synthesis gas, and to separate normal paraffins from branched paraffins and aromatics

Adsorption from the liquid phase is used to remove organic components from aqueous wastes, colored impurities from sugar solutions and vegetable oils, and water from organic liquids Adsorption can also be used to recover reaction products that are not easily separated

by distillation or crystallization Some of the same types of solids are used for both phase and liquid-phase adsorption, though often adsorbents with larger pores are preferred for use with liquids

vapor-Exercises 23.1 Translate into Vietnamese

Adsorption, adsorbent, switched, regenerate, regeneration, achieve, exchange, soften, deionize, bead, column, trace, emphasis, applicable, fixed bed, ink, printing ink, paint, casting, fabric, laden, refrigerate, impractical, attempt, concentration, emission, circulating, ventilation, canister, vent, porous, zeolite, sieve, aluminosilicate, regular, pore, effective, dew point, crystallization

23.2 Translate the following sentences paying attention to the words in bold type

1 Unvulcanized rubber is both plastic and elastic

2 Rubber either in the form of latex or solid sheet, when stored for considerable periods

develops increased hardness

3 The generation of oxygenated groups in secondary reactions is consistent with our

present knowledge of polyisoprene biosynthesis

4 It has been suggested that the carbonyl groups (in storage hardening) are incorporated at

intervals along the “hydrocarbon chain”

5 As a result of Goodyear’s work, along with improvements by Hancock, rubber goods of

wide utility and durability could be made

6 Modern industry could no longer function properly without reinforced rubber

7 Polystyrene has been used commercially long before the high styrene resins

23.3 Find (in the list given below) synonyms to the following words Translate these words in to Vietnamese

23.4 What do you know about

23.5 Translate the following sentences paying attention to the words in bold type

1 When parts of the long molecules of the natural rubber arrange themselves in an ordered

state crystallizing they are assumed to exhibit a first - order transition

2 There is a rubber like state, which many substances made from long molecules may

assume under suitable conditions

3 Mendeleyev’s theoretically assumed value of 240 for the atomic weight of uranium was

confirmed by the scientists

4 Synthetic rubber produced from isoprene was presumed to a long chain structure built up

from isoprene units by 1-2, 1-4 linkages

23.5 Give a summary of the text

UNIT 24 EVAPORATION

The objective of evaporation is to concentrate a solution consisting of a nonvolatile solute and a volatile solvent In the overwhelming majority of evaporations the solvent is water Evaporation is conducted by vaporizing a portion of the solvent to produce a concentrated solution of thick liquor Evaporation differs from drying in that the residue is a liquid—sometimes a highly viscous one—rather than a solid; it differs from distillation in that the vapor usually is a single component, and even when the vapor is a mixture, no attempt is made in the evaporation step to separate the vapor into fractions; it differs from crystallization

in that emphasis is placed on concentrating a solution rather than forming and building crystals In certain situations, e.g., in the evaporation of brine to produce common salt, the line between evaporation and crystallization is far from sharp Evaporation sometimes produces a slurry of crystals in a saturated mother liquor

Normally, in evaporation the thick liquor is the valuable product and the vapor is condensed and discarded In one specific situation, however, the reverse is true Mineral-bearing water often is evaporated to give a solid-free product for boiler feed, for special

process requirements, or for human consumption This technique is often called water

distillation, but technically it is evaporation Large-scale evaporation processes have been

developed and used for recovering potable water from seawater Here the condensed water is the desired product Only a fraction of the total water in the feed is recovered, and the remainder is returned to the sea

LIQUID CHARACTERISTICS The practical solution of an evaporation problem is profoundly affected by the character of the liquor to be concentrated It is the wide variation

in liquor characteristics (which demands judgment and experience in designing and operating evaporators) that broadens this operation from simple heat transfer to a separate art Some of the most important properties of evaporating liquids are as follows

Concentration Although the thin liquor fed to an evaporator may be sufficiently dilute

to have many of the physical properties of water, as the concentration increases, the solution becomes more and more individualistic The density and viscosity increase with solid content until either the solution becomes saturated or the liquor becomes too viscous for adequate heat transfer Continued boiling of a saturated solution causes crystals to form; these must be removed or the tubes clog The boiling point of the solution may also rise considerably as the solid content increases, so that the boiling temperature of a concentrated solution may be much higher than that of water at the same pressure

Foaming Some materials, especially organic substances, foam during vaporization A stable foam accompanies the vapor out of the evaporator, causing heavy entrainment In extreme cases the entire mass of liquid may boil over into the vapor outlet and be lost

Temperature sensitivity Many fine chemicals, pharmaceutical products, and foods are damanged when heated to moderate temperatures for relatively short times In concentrating such materials special techniques are needed to reduce both the temperature of the liquid and the time of heating

Scale Some solutions deposit scale on the heating surface The overall coefficient then steadily diminishes, until the evaporator must be shut down and the tubes cleaned When the scale is hard and insoluble, the cleaning is difficult and expensive

Materials of construction Whenever possible, evaporators are made of some kind of steel Many solutions, however, attack ferrous metals or are contaminated by them Special materials such as copper, nickel, stainless steel, aluminum, impervious graphite, and lead are then used Since these materials are expensive, high heat-transfer rates become especially desirable to minimize the first cost of the equipment

Many other liquid characteristics must be considered by the designer of an evaporator Some of these are specific heat, heat of concentration, freezing point, gas liberation on boiling, toxicity, explosion hazards, radioactivity, and necessity for sterile operation Because

of the variation in liquor properties, many different evaporator designs have been developed The choice for any specific problem depends primarily on the characteristics of the liquid

SINGLE- AND MULTIPLE-EFFECT OPERATION Most evaporators are heated by steam condensing on metal tubes Nearly always the material to be evaporated flows inside the tubes Usually the steam is at a low pressure, below 3 atm abs; often the boiling liquid is under moderate vacuum, at pressures down to about 0.05 atm abs Reducing the boiling temperature of the liquid increases the temperature difference between the steam and the boiling liquid and thus increases the heat-transfer rate in the evaporator

When a single evaporator is used, the vapor from the boiling liquid is condensed and

discarded This method is called single-effect evaporation, and although it is simple, it utilizes

steam ineffectively To evaporate 1 kg of water from a solution calls for from 1 to 1.3 kg of steam If the vapor from one evaporator is fed into the steam chest of a second evaporator and the vapor from the second is then sent to a condenser, the operation becomes double-effect The heat in the original steam is reused in the second effect, and the evaporation achieved by

a unit mass of steam fed to the first effect is approximately doubled Additional effects can be added in the same manner The general method of increasing the evaporation per kilogram of steam by using a series of evaporators between the steam supply and the condenser is called

multiple-effect evaporation

Exercise 24.1 Translate into Vietnamese

Objective, evaporation, nonvolatile, overwhelming, vaporize, evaporate, evaporator, crystal, brine, slurry, liquor, recover, portable, profoundly, judgment, boaden, dilute, sufficient, individualistic, tube, clog, foam, entrainment, outlet, inlet, sensitive, pharmaceutical, moderate, coefficient, steady, diminish, ferrous steel, impervious, graphite, liberate, radioactivity, sterile, discard, single-effect operation, multi-effect operation, ineffectively, approximately

24.2 Translate the following sentences paying attention to the function of the verb to do

1 Monosaccharides do not hydrolyze to simpler substances

2 An organic chemist has much to do with different reactions

3 It is known that most fibers when suspended in an alkaline aqueous medium have a

negative charge as do the particles in alkaline latex

4 Upon what structural arrangement does the colour of an organic compound depend?

5 Some grades of synthetic material have lower cis- content than do natural rubber

6 The results of the experiment show that adhesion does increase for a time after curing, at

least when measured at room temperature

7 On the basis of oxidizability, the zinc salt had the effect, as did mercaptobenzimidazole

itself

24.3 Translate the following sentences paying attention to the “Complex Object”

1 We consider the natural rubber to be isomerized

2 Investigators find the infra-red spectrum to be closely similar to that of natural rubber

3 One might expect the increase in hardness to be a result of intra- particle crosslinking

4 Researchers dealing with latex know biologically induced oxidation to proceed in the vicinity of the tapping cut

24.4 Form nouns from the following adjectives

unaffected undesirable unduly unusable

24.6 Translate into Vietnamese paying attention to the prefix re-

heat - reheat

soften - resoften

form - reform

melt - remelt construct - reconstruct

24.7 Translate the following derivative into Vietnamese

resist, resistant, resistance apply, application

viscous, viscosity use, useful, useless process, processing

24.8 Translate into Vietnamese paying attention to the words in bold type

1 The name ABS, based on the first letters of each of the monomeric components has been

adopted for this family

2 By introducing acrylonitrile monomer into a similar system, a significant improvement in

all these properties is obtained, as well as outstanding toughness and resistance

3 Various combinations of properties are possible, thus making these polymers most attractive for a larger number of current and newly developed applications

4 ABS plastics are extremely useful and versatile, since ease of processing and forming allows them to be used for a great number of applications

5 The strength of a fabricated item produced from ABS plastic is dependent on a number

of variables

24.9 Give a summary of the text

UNIT 25 CHROMATOGRAPHY

Chromatography is a versatile separation technique in chemistry and chemical engineering In any chromatographic separation there are two phases (solid, liquid, or gas); these move relative to each other while maintaining intimate contact There are several forms

of chromatography such as gas chromatography, gas-liquid chromatography, liquid-solid chromatography, high performance liquid chromatography, e.g

Gas chromatography

Gas chromatography is a method for separating components of mixtures of volatile compounds In most applications, the separations are made to identify and determine the quantity of each component of a sample of the mixture, and analytical gas chromatographic apparatus includes additional devices for this purpose In some applications, separations are made for preparative purposes, but the scale is not generally greater than that required for quantities of the order of 100g

The central item in the apparatus for gas chromatography is the chromatographic column, a long tube packed permeably with some adsorbent In the commonest technique of gas chromatography, the elution technique, a stream of inert gas, the carrier gas, passes continuously through the column, and the mixture to be separated is introduced at the beginning of the column as a sample either of a gas or a volatile liquid Let us suppose that the sample consists of one pure component After introduction, it is swept by the carrier gas

on to the column, first evaporating to form a vapor if it is introduced as a liquid When it reaches the column, it is largely adsorbed, but the equilibrium is set up between the column and the gas in the interstices of the column so that a proportion of the sample always remains

in the gas phase This portion moves a little further along the column in the carrier gas stream, where it again equilibrates with the column At the same time, material already adsorbed in the column re - enters the gas phase so as to restore equilibrium with the clean carrier gas which follows up the zone of vapor

The speed at which the zone moves depends on two factors, the rate of flow of the carrier gas and the extent to which the vapor is adsorbed The faster the flow of carrier gas, the faster the zone moves; and the more strongly the vapor is adsorbed on the column, the more slowly the zone moves When two or more components are present in the sample, each usually behaves, independently of the others so that for a given carrier gas flow rate, the speed

of the zone of each component will depend on the extent to which it is adsorbed Since different substances differ in their adsorption, they may therefore be separated by making use

of their different speeds of progress through the column If they are eluted to the far end of the column, they will appear one after the other in the gas stream, the fastest first and the lowest last

Adsorbents such as carbon, alumina, or silica gel are used as the packing material for columns, but in more than 90% of applications, the column material is the liquid held in place

on the column by being adsorbed on an inert solid support Gas chromatography with this kind of column is called Gas Liquid Chromatography (GLC) This method is used for separating solutes from mixed solutions

Exercises 25.1 Read and translate into Vietnamese

Chromatography, chromatographic, exceptional, exceptionally, versatile, intimate, stationary, mobile, analogy, conveyor, belt, lag, introduce, detect, device, apparatus, column, elute, inert, carrier, sweep, interstice, equilibrate, restore, differ, pack, packing material

25.2 Answer the following questions

1 What does gas chromatography mean?

2 What is the central item in the apparatus for gas chromatography?

3 What gas passes through the column?

4 How does the process of chromatography pass?

5 What are adsorbents such as carbon, alumina, or silica gel used for?

6 What method is used for separating solutes from mixed solutions?

25.3 Read and translate the following derivative

1 analytical, analysis, analyze;

2 scheme, schematic, schematically;

3 compress, compression;

4 identify, identification;

5 include, inclusion, inclusive;

6 prepare, preparation, preparative;

7 adsorb, adsorbent, adsorption;

8 technique, technical, technician;

9 evaporation, vapor;

10 equilibrium, equilibrate, equilibration;

11 behavior, behave;

12 solute, solution, solvent, soluble, dissolve;

25.4 Translate into Vietnamese paying attention to the words in bold type

1 The mixture is introduced as a sample either of a gas or a volatile liquid

2 The material already adsorbed in the column re-enters the gas phase so as to restore

equilibrium with the clean carrier gas

3 The speed at which the zone moves depends on the rate of flow of the carrier gas and the

extent to which the vapor is adsorbed

4 The faster the flow of the carrier gas, the faster the zone moves

5 The more strongly the vapor is adsorbed on the column, the more slowly the zone moves

6 The speed of the zone of each component will depend on the extent to which it is adsorbed 25.5 Translate into English

1 Sắc kí khí là phương pháp tách các cấu tử của hỗn hợp các chất dễ bay hơi

2 Việc tách được tiến hành để định lượng mỗi cấu tử trong hỗn hợp

3 Bộ phận chính của thiết bị sắc kí khí là cột sắc kí (là một ống dài được nhồi một chất có khả năng hấp phụ)

4 Khí mang liên tục đi qua cột sắc kí Hỗn hợp cần tách được cho vào cột hoặc ở dạng khí hoặc ở dạng lỏng dễ bay hơi

25.6 Write a short summary of the text

UNIT 26 LIQUIS-SOLID CHROMATOGHRAPHY

The next chromatographic technique to be considered is liquid-solid chromatography The stationary phase is made up of very small particles of solid packed in a column (hence, the common name column chromatography), and the mobile phase is a liquid that percolates through the column and past the surfaces of the solid particles

Solid surfaces adsorb thin layers of foreign molecules as a result of electrostatic and van der Waals forces Since adsorption strengths differ with the character of the solid surface,

a properly chosen solid may adsorb selectively one component of a mixture An important example of selective adsorption employed in the previous chapter is the use of charcoal in crystallization to remove large, polar (usually colored) impurities The ideal limiting law governing adsorption from a dilute solution is

amount of solute A adsorbed per unit surface areaconcentration of solute A in solution = KAThe structural features that determine the extent of adsorption of a molecule on a solid surface are pretty much the same as those considered when solubility was discussed A complication in thinking about adsorption is that the solvent and the solute are competing for the same active sites on the surface For molecules with polar functional groups, the value of

K A (the adsorption coefficient) is determined principally by the relative polarities of the group

and the solvent If the solvent is more polar than the solute, the solute will have a low K A (i.e.,

be poorly adsorbed) and move along rapidly with the mobile phase For molecules containing hydroxyl groups, their relative abilities to form hydrogen bonds to the solid or the solvent are also significant

Two solutes with different adsorption coefficients for a certain solid can, at least in principle, be separated by liquid-solid chromatography The traditional method is to prepare a cylindrical column of the solid (with a height about 5 to 10 times the diameter) and place a concentrated solution of the sample at the top of the column As the solution penetrates the column, the solutes are adsorbed As soon as the solution has completely penetrated the column, fresh solvent is added at the top The solvent flows down the column under the force

of gravity and capillary attraction, and redissolves the solutes in amounts determined by the adsorption law and carries them to lower clean sections of the column, where they are readsorbed (always in amounts governed by the adsorption law) As more solvent percolates through the column, the cycle of adsorption-solution continues, and the solutes gradually

move down the column in concentrated bands (development) With solutes having different

adsorption coefficients, the least tightly adsorbed material moves faster If the adsorption coefficients are sufficiently different or the column is sufficiently long, the faster-moving component will form a separate band below the slower- moving one At the bottom of the

column the solutes are forced off (elution) and can be collected separately in successive

fractions

For satisfactory separation by liquid-solid column chromatography, it is essential to choose an appropriate combination of solid adsorbent and eluent that is compatible with the compounds to be separated Compounds that are adsorbed very tightly require an excessive

volume of solvent (eluent) for development Compound adsorbed weakly may move too

rapidly to give separation before being eluted Table 2 gives some generalizations that are useful as a guide in selecting appropriate solid-solvent combinations

A common variation of liquid-solid chromatography is the use of a thin film of solid (mixed with a binder such as plaster of pans) on a sheet of glass or plastic The solution is added as a spot at the bottom of the plate and the plate is dipped vertically into a shallow layer of solvent, which ascends (against gravity) by capillary action and moves the solutes with it The particular advantage of this technique is that the solutes are exposed and can be isolated readily or treated on the plate at any moment The method is widely used for qualitative identification of mixture components because it is fast and has exceptionally good resolution For a fixed combination of solid, binder, and solvent, each substance will travel along the thin-layer plate a characteristic fraction of the distance traveled by the solvent It is

customary to report thin-layer chromatography data as R F values (retardation or retention

factor), defined as the distance of the spot from the starting point divided by the distance of

the solvent front from the starting point

Thin-layer chromatography is restricted to very small samples Larger samples can be separated by using thick layers of plaster of paris, but there is a practical upper limit of a few tenths of a gram A method known as “flash”

When all components of a mixture are held tightly, as happens frequently, it is

necessary to percolate dilute acid through the column to move the components (displacement

development)

Table 1 Adsorbents and Solvents for Liquid - Solid Chromatography

Chromatographic solids in

order of decreasing adsorption

strength far polar molecules

Solvents in order of increasing

eluting ability

Activated alumina Activated magnesium sulfate

Activated silicic acid Inorganic carbonates Starch, cellulose

Saturated hydrocarbons Aromatic hydrocarbons Partially hydrogenated hydrocarbons

Ethers Ketones Alcohols

Basic columns also are available (such as Dowex 3, a resin of polystyrene beads containing free amino groups); these accept protons and can be used to separate mixtures of organic acids of different acid strengths Special column materials that form ionic complexes with various inorganic cations or anions are useful, as are columns containing ions that form complexes with certain organic molecules

Exercise 26.1 Read and translate into Vietnamese

Stationary phase, mobile phase, percolate, adsorb, electrostatic, selectivity, employ, dilute, govern, active, site, polar, functional, coefficient, traditional, cylindrical, penetrate, solute, gravity, capillary, redissolve, readsorb, compatible, generalization, shallow, capillary, exceptional, resolution, thin-layer plate, customary, charcoal, resin, polystyrene

26.2 Answer the following questions

1 What are the two phases of gas-liquid chromatography?

2 What are the essential properties of two solutes those can be separated by solid liquid chromatography?

3 What is an eluent?

4 What is thin layer chromatography used for?

26.3 Read and translate the following derivative

1 chromatography, chromatographic;

2 separate, separation, separator;

3 volatile, volatility, volatilization, volatilize;

4 detector, detect, detection;

5 concentrate, concentration;

6 solid, solidity, solidify;

7 quality, qualitative, qualitatively;

8 quantity, quantitative, quantitatively;

9 particular, particularly;

26.4 Read and translate the following sentences paying attention to the functions of the Infinitive

1 Carrier gas from the tank of compressed gas first passes to a controller, the usual purpose

of which is to maintain a constant flow of gas

2 In the inlet to the column there is a simple injector through which the sample to be analyzed can be introduced

3 The purpose of the detector is to detect the separate components of the mixture as they

emerge one by one

4 A further piece of apparatus not always incorporated is a flow meter to measure the rate of

the flow of gas

5 Almost any high boiling liquid may be used

6 Sample injectors aim to inject a temperature control of the column

7 In the years to come many new synthetic products will appear

8 It has taken centuries of scientific research and invention to develop the civilization of the

11 The second use of the chromatogram is to enable one to identify the individual

components of a mixture qualitatively

12 For the preparation of an aerosol, the substance to be dispersed is first evaporated, and

the vapor is then quickly cooled

26.5 Translate into Vietnamese paying attention to the words in bold type

1 Not a single property, but rather the combination of the properties has made this substance

4 When no vapor is passing through, the recorder gives a straight line

5 No traces of water have been obtained during the test

6 A quantitative analysis of the mixture is provided by the detector rather than the column

7 Gas chromatography is mainly used for quantitative analysis, for the method is suitable for the routine analysis of industrial samples, the interpretation of the data is simple, and the

apparatus does not require skilled personnel

26.6 Translate into English

1 Thiết bị được sử dụng trong sắc kí khí rất đơn giản

2 Nhiệm vụ của detector là để phát hiện các cấu tử riêng rẽ của hỗn hợp khi chúng lần lượt

đi ra khỏi cột

3 Detector sử dụng một số tính chất hóa học và vật lý của các hợp chất, mà nhờ chúng các cấu tử được phát hiện và nếu cần thì được xác định

4 Sắc ký lớp mỏng thường được dùng để phân tích lượng chất rất nhỏ

26.7 Make up an outline of the text and retell the text

PART 3 THE PETROCHEMICAL INDUSTRY AND

REFINERY UNITS

III.1 TYPICAL UNITS

UNIT 27 ON OIL AND GAS INDUSTRY

Petroleum is the name mineral oil Oil comes from under the ground Crude oil comes from the well or bore-holes Boreholes are often very deep The steel framework over the well

is the derrick From the derrick the machinery drills holes through rock, earth or sand Oil usually flows freely but man control its natural flow The natural flow of oil is the result of the pressure of the natural gas in oil or the result of the pressure between the petroleum and the roof of the rock above it

Crude oil contains various materials, liquids By the process of refining we obtain petrol, paraffin, and other products from crude oil We obtain various fuels from it too Fuel drive ships, planes, buses, and so on Diesel engines burn oil fuel Many tractors burn diesel oil Jet engines burn kerosene (paraffin oil)

The growth of the manufacture of engines and machines and of the petrochemical industry increase rapidly Today, the oil industry is an advanced, highly mechanized and reliable sector of the economy It has highly productive rigs that can drill down to oil and gas deposits lying at depth of more than six kilometers Today, more than 2,000 products are made from oil: fuel for aircraft and for internal combustion engines, fuel for boilers and furnaces, lubricants, bitumen for the manufacture of asphalt, lacquers, solvents, and so on Oil by-products are used in making plastics and synthetic substances

Exercises 27.1 Read and translate into Vietnamese

Petroleum, crude oil, mineral oil, bore-holes, framework, derrick, drill, roof, petrol, engine, fuel, diesel oil, kerosene, mechanize, rig, internal combustion engine, boiler, furnace, lubricant, bitumen, asphalt, lacquer, plastic

27.2 Answer the following questions

1 What is the result of the pressure of the natural gas in oil?

2 Where does the oil come from?

3 From where does the machinery drill hole?

4 What does fuel drive?

5 What does the crude oil contain?

6 By what process do we obtain petrol, paraffin and other products from crude oil?

7 How many product we make from oil today?

27.3 Fill in the blanks with the proper words from those given below

1 …knows that crude oil contains various materials

2 …saw your friend in the laboratory some minutes ago

3 Was there … in the boot of your car?

4 He told me … new about oil extraction?

5 Does … control the natural flow of oil?

6 It is possible to find these tubes

Somebody, something, anybody, everybody, everyone, anything, everywhere

27.4 Rewrite the following sentences according to the model

Model: I don’t know anything about this liquid

I know nothing about this liquid

1 We did not meet anybody in the laboratory yesterday

2 My fried did not go anywhere last year

3 He did not see any tube on the desk

4 We did not see anybody in the shop

5 We did not find anything in our compartment

27.5 Translate into English

1 Rất nhiều sản phẩm được tạo ra từ quá trình chế biến dầu mỏ

2 Quá trình chưng cất dầu mỏ được phát minh từ năm 1913 do nhà bác học Burton để tinh chế dầu mỏ

3 Giàn khoan là khung bằng thép mà từ đó máy khoan các lỗ khoan qua lớp đất đá hoặc cát

4 Ngành công nghiệp dầu mỏ là một trong những bộ phận quan trọng của nền kinh tế

27.6 Write a short summary of the text

UNIT 28 COMPOSITION OF PETROLEUM

Petroleum is a natural mixture of various hydrocarbons and their derivatives containing sulfur, nitrogen, oxygen, metals, etc

a Hydrocarbons

The main constituents of petroleum - hydrocarbons - may differ in the number of carbon and hydrogen atoms in the molecule and in the molecular structure Petroleum hydrocarbons may relate to the following groups or series: paraffins (saturated or stable hydrocarbons, alkanes), naphthenes (cycloalkanes), and benzene hydrocarbons (arenes) In most grades of petroleum, paraffins and naphthenes prevail During processing of petroleum, unsaturated hydrocarbons (olefins and diolefins) may also form The specific properties of petroleum products are decided by the predominance of some or other group of hydrocarbons

in crude petroleum and by the presence of compounds containing sullur, nitrogen or oxygen

b Oxygen- containing compounds

These include naphthenic acids, phenols and tar- asphaltene compounds

Naphthenic acids are compounds containing a carboxyl group-COOH Their density

is from 0.96 to 1.05 g/cm3 and the general formula, CnH2n-zO2 Naphthenic acids strongly smell oily liquids They may be present in kerosene, diesel- fuel and light oil distillates of petroleum and are corrosion- aggressive; they are removed from petroleum fractions by leaching Naphthenic acids and their salts are widely used in industry as components of greases, for impregnation of fabrics and footwear, etc

Phenols are contained only in some grades of petroleum and are liberated together

with naphthenic acids during leaching of distillates

Tar- asphaltene compounds may be present in petroleum in considerable quantities

(from traces to 25% and even more) They are complex high-molecular compounds containing carbon (82-87.4%), hydrogen (10.3-12.5%), oxygen (up to 2.5%), sulfur (0.8-7%), and nitrogen (up to 1%) Low molecular tar compounds can partially be distilled off together with petroleum distillates, while high molecular ones remain in fuel-oil fractions and especially in oil residue (goudron) The presence of tar in these products makes them dark and promotes carbonization in cylinders of internal combustion engines Tar- asphaltene products are harmful is white petroleum products and oils, but are desirable constituents in such products as bitumen, coke, insulating and impregnating materials

All tar-asphaltene products are usually classed into neutral resins soluble in light gasoline; asphaltenes (the products of polymerization of neutral resins and oxyacids) which are insoluble in light gasoline, but soluble in benzene, chloroform and carbon bisulfide; asphaltogenous acids and their anhydrides of acid nature which are insoluble in light gasoline, but soluble in alcohol

All the three types of tar-asphaltene compounds are high-molecular compounds of unsaturated nature containing oxygen and sulfur At normal temperature they are very thick and viscous liquids or are solid and have a density above 1.0 g/cm3 The content of tar-asphaltene compounds is greater in petroleum grades of higher density and in those high in sulfur

c Sulfur compounds

Sulfur is present in petroleum and petroleum products mostly in combined state, i.e in the form of organic sulfur compounds Sulfur compounds of the following types may be found in petroleum products: mercaptans RSH (where R is a hydrocarbon radical); sulfides

RS, disulfides RS-SR, thiophene C4H4S and its derivatives, and sometimes hydrogen sulfide and elemental sulfur Hydrogen sulfide and mercaptans which have acid properties, and elemental sulfur form a group of active sulfur compounds which can cause strong corrosion of equipment and pipelines

Another group includes sulfides and disulfides which are neutral at low temperatures, but are thermally unstable; at 130-160oC they decompose (with breaking of C-S bonds) and form hydrocarbons, mercaptans and hydrogen sulfide A third group includes thiophane and thiophene and their derivatives, such as benzothiophene

Like benzene hydrocarbons, they have low reactivity and are relatively stable at elevated temperatures

High- molecular sulfur compounds are unstable and can be oxidized under relatively soft conditions; the products of oxidation increase the content of tar in petroleum products In the atmosphere of hydrogen, they are reduced to corresponding hydrocarbons and hydrogen sulfide; this is the basis of the processes of hydrogen refining (hydrofining) of petroleum and petroleum products

In straight distillation of petroleum (without destruction) the content of sulfur increases from lighter fraction to heavier ones, with the residue having the highest concentration of sulfur When higher temperatures and pressures are applied, however, organic sulfur compounds are destroyed together with high - molecular hydrocarbons to form hydrogen sulfide and mercaptans which are corrosive and toxic Corrosion is enhanced in the presence of water vapors and hydrochloric acid which forms by decomposition of calcium and magnesium chlorides contained in undesalted petroleum

In order to diminish corrosion and improve labor conditions, petroleum before distillation might be desalted and dehydrated The content of sulfurous compounds in petroleum products can be lowered by various methods of refining, mainly by hydrogen refining

d Nitrogen Compounds

The content of nitrogen compounds is usually greater in heavier grades of petroleum

Nitrogen compounds are divided into basic, which contain nuclei of pyridine and quinoline, and neutral, which contain pyrrole and indole homologues

In petroleum processing, nitrogen compounds are distributed between fractions much like sulfur compounds, i.e., their concentration increases from lighter fractions to heavier ones, and the largest amount (65-75%) is concentrated in the residue

Among nitrogen compounds, porphyrins occupy a special place They may be present

in petroleum either in free state (four pyrrol rings) or as complexes containing organic nitrogen compounds and organic derivatives of vanadium and nickel Notwithstanding the high thermal stability of nitrous compounds in the technological processes, they decompose partially, which is detected by the formation of ammonia Certain refining processes (for instance, hydrogen refining) can remove an appreciable portion of sulfurous compounds (as hydrogen sulfide) and a part of nitrogen compounds (as ammonia) and oxygen compounds (as water vapors)

e Mineral Substances

Mineral substances are found in petroleum only in very small concentrations (provided that crude petroleum has been refined properly from mechanical impurities at the oil well) As has been established by combustion of many samples of petroleum, the elements found in the ash form (in the decreasing order) the following row: S-O-N-V-P-K-Ni-I-Si-Ca-Fe-Mg-Na-Al-Mn-Pb-As-Cu-Ti-V-Sn-As The total amount of ash in various grades of petroleum may vary from a few thousandths of a percent to 0.8 percent

Exercises 28.1 Read and translate into Vietnamese

Sulfur, metal, constituent, predominance, extreme, satisfy, isomer, isomeric, possess, deposit, antiknock, butylene, amylene, propylene, butylene, constitute, appreciable, polypropylene, propylene, oxide, butadiene, isoprene, tar, asphaltene, naphtenic acid, oily, considerable, partial, partially, promote, carbonization, cylinder, internal combustion, bitumen, insulating, impregnate, resin, polymerization, oxyacid, asphaltogeneuous acid, anhydride, mercaptane, sulfide, disulfide, thiophene, corrosion, pipeline, thiophene, benzothiophene, soft conditions, refining, hydrofining, straight distillation, enhance, desalt, diminish, dehydrate, pyridine, quinoline, pyrrol, indol homologue, distribute, porphyrin, vanadium, notwithstanding, decompose, detect, provided that, ash, properly

28.2 Answer the following questions

1 What is the elemental composition of petroleum?

2 What are the main constituents of petroleum?

3 Which series of hydrocarbon are present in petroleum?

4 Which series of hydrocarbon are formed during processing of petroleum?

5 What can you say about the chemical properties of paraffin hydrocarbons?

6 What are the physical properties of paraffin hydrocarbons?

7 Which compounds are called isomers?

8 What can you say about the chemical and physical properties of isomers?

9 What are the difference and the similarity in structure and properties between paraffinic and naphthenic hydrocarbons?

10 What are the difference and the similarity in structure and properties between naphthenic and benzene hydrocarbons?

11 What are the applications of benzene hydrocarbons?

12 What can you say about the properties of olefins and diolefins?

13 What are the applications of olefins and diolefins?

14 What are the applications of naphthenic acids?

15 What is the elemental composition of tar-asphaltene compounds?

16 How can you classify tar-asphaltene products?

17 Which types of sulfurous compounds are present in petroleum products?

18 How can the content of sulfurous compounds in petroleum products be lowered?

19 How are the nitrogen compounds distributed in petroleum products?

28.3 Translate into English

1 Thành phần chính của dầu mỏ là các hydrocacbon và phi hydrocacbon từ C5 đến C60

2 Các hydrocacbon trong dầu mỏ gồm có paraffin, naphthen và aromatic Các hydrocacbon không no không tồn tại trong dầu mỏ

3 Ngoài hydrocacbon, trong dầu mỏ còn có các hợp chất chứa oxi, nito, lưu huỳnh, kim loại…

4 Trong các hợp chất chứa dị tố (O, N, S) thì các hợp chất chứa S là ít mong muốn nhất vì chúng gây ô nhiễm môi trường và ảnh hưởng xấu tới hệ sinh thái

28.4 Write a short summary of the text

UNIT 29 BASIC PHYSICO-CHEMICAL PROPERTIES OF

PETROLEUM AND PETROLEUM PRODUCTS

a Density

The density of petroleum and petroleum products can be expressed in either absolute

or relative values The relative density is the ratio of the density of a petroleum product at temperature t2 to the density of distilled water at temperature t1 The density of petroleum products is normally measured at 20oC and that of water, at 4oC Since the latter is taken as unity, the numerical values of the relative and absolute density coincide

To find the absolute density  (kg/m3 or g/cm3) the mass of a product is divided by its volume, i e.,  = m/V

The density of petroleum and petroleum products depends on the content and composition of light low-boiling (which have a low density) and heavy high-boiling constituents (fractions) Indeed, among the components having roughly the same boiling point, paraffin hydrocarbons have the lowest density, and benzene hydrocarbons have the highest value, with that of naphthalenes being in the middle This is why density is one of the principal characteristics of petroleum and petroleum products

The density of petroleum and petroleum products decreases with the increasing temperature, and their volume respectively increases The temperature relationship for density can be expressed by Mendeleev's formula:

M = 60 + 0.3t + 0.001t2

where t is the average temperature of boiling of a petroleum fraction, oC; it is calculated as the arithmetic mean of the temperatures at which equal volumes of the liquid, say, 10% fraction, is distilled off

The relationship between the molecular mass and relative density of petroleum fractions is determined by the following empirical formula:

M = 44.29d1515/1.03- d1515

Using this formula, it is also possible to find (with a certain approximation) the molecular mass of all classes of hydrocarbons

c Boiling Point Fractional Composition

The boiling point of a liquid is the temperature at which the pressure of vapors is equal to the external pressure; on reaching this point, vaporization, which up to that moment occurred from the surface only, begins in bulk of the liquid (at the bottom and walls of the vessel being heated), where vapor bubbles are formed; this is what is called the boiling proper If vapors are not removed off the liquid surface during heating, equilibrium is established between the liquid and vapor phase Vapors in equilibrium with the liquid are

called saturated At a higher temperature of heating of a liquid, vaporization occurs more

intensively, more vapors are formed above the liquid, and the pressure of saturated vapors is higher

The boiling point of a liquid depends on the external pressure For instance, water at a pressure of 0.1 MPa boils at 100oC At a higher pressure, say 0.4 MPa, boiling begins only at

144oC Thus, the boiling point is higher at a higher external pressure and at a lower external pressure or in vacuum, water boils at a lower temperature The same effect of pressure is found in other liquids This phenomenon is utilized in vacuum distillation of fuel oil

Petroleum and petroleum products can be separated into individual hydrocarbons only with certain difficulties Usually, separation is carried out by distillation which gives simpler

mixtures of hydrocarbons than the original mixture These mixtures are called fractions They

boil not at a constant temperature, but in a temperature range between the point of the beginning of boiling and that of its end Depending on the boiling points and contents of various hydrocarbons, a product may have different boiling ranges; i e., may have a different

fractional composition

All petroleum products obtained from crude petroleum by distillation are essentially fractions that can boil off within particular temperature ranges For instance, gasoline fractions boil off within 35-205oC, kerosene fraction within 150-315oC, diesel-fuel fractions within 180-350oC, light oil distillates within 350-420oC, heavy oil distillates within 420-

490oC, and oil residues at temperatures above 490oC

d Thermal Properties of Petroleum and Petroleum products

These properties are of high practical importance for calculating the heat balance of all processes associated with heating or cooling

Specific heat is the quantity of heat needed to heat up 1 kg of a substance by 1oC The approximate values of specific heat, kJ/kg K, are as follows: petroleum 2.1, petroleum vapors 2.1, water 4.19

With the specific heat of a petroleum product being known, it is possible to calculate the quantity of heat for heating For this, the specific heat is multiplied by the mass of the product (kg) and by the difference between the final and initial temperature (oC) The specific heat of petroleum products increases with increasing temperature and is higher for products of lower density

Specific latent heat of evaporation is the quantity of heat spent to vaporize 1 kg of a

liquid at its boiling point (this characteristic is called latent, since the heat is spent for evaporation and the temperature of the product remains constant during heating) Thus, the latent heat of evaporation decreases with increasing density and molecular mass of petroleum products, and also with increasing temperature and pressure

The heat of condensation is the quantity of heat liberated by vapors during their

condensation and is numerically equal to the latent heat of evaporation

The latent heat of fusion is the quantity of heat absorbed during fusion of 1 kg of a

solid at the melting point

The heat of combustion (calorific value) of fuel is the quantity of heat liberated by the

fuel on full combustion A distinction is made between the high and low heat of combustion: the former (Qh) takes into account the heat of condensation of the water present in the fuel and formed during combustion (it is taken conditionally that the combustion products contain liquid water rather than water vapors) The low heat of combustion, Ql, implies that the water

of the fuel and the water formed by combustion is removed as vapors with combustion gases (i.e it is lower than the high heat of combustion by the quantity of heat spent for evaporation

of the moisture of the fuel and of the water formed through combustion of hydrogen in the fuel)

e Distillation curves

Fractional distillation is a process that separates a mixture of liquids based on their volatility, or tendency, to vaporize In a mixture of two liquids, the temperature will remain constant as one distills and shoots up abruptly to a different temperature where the other liquid will distill A distillation curve plots temperature versus the amount of distillate collected A distillation curve will clearly show the boiling point of each liquid in the mixture and their respective volumes There are several types of Distillation Curve: True Boiling point (TBP) Distillation, ASTM Distillation, Semi-fractionating Distillation, and Equilibrium Flash Vaporization (EFV)

- TBP: This type of distillation is commonly used due to the accuracy of the results obtained by this method which is very close to that obtained via real distillation or industrial distillation In this distillation, there is a fractionation column located between the condenser and the flask In general, this type of distillation is carried out by two steps: firstly, under atmospheric pressure until 300°C (1% distilled very 2 min), secondly under vacuum pressure (to prevent cracking process and to reduce the boiling point) at 40mmHg (1% distilled every 3-5 min)

- ASTM: In this type of distillation there is on fractionation column located between the condenser and the flask On the other hand, the raised vapor will not be fractionated in this process This distillation is used with fractions having a short range of the boiling point

- Semi-fractionating distillation: In this type of distillation, there will be some fractionating process on the raised vapor via package located between the condenser and the flask

- Equilibrium Flash Vaporization (EFV): Is a single stage separation technique A liquid mixture feed is pumped through a heater to raise the temperature and enthalpy of the mixture It then flows through a valve and the pressure is reduced, causing the liquid to partially vaporize Because the vapor and liquid are in such close contact up until the "flash" occurs, the product liquid and vapor phases approach equilibrium

Exercises 29.1 Read and translate into Vietnamese

Physico-chemical, express, absolute, relative value, relative density, measure, coincide, roughly, fraction, external, essential, gasoline, kerosene, multiply, specific latent heat of evaporation, liberate, numerically equal, latent heat of fusion, distinction, tendency,

shoot, abruptly, versus, accuracy, flash, equilibrium

29.2 Answer the following questions

1 How can they express the density of petroleum and petroleum products?

2 What is the relative density of a petroleum product?

3 How can you calculate the absolute density?

4 Is there any relationship between the density of petroleum products and their boiling points? What is it?

5 What are the relationship between the density of petroleum products and their temperature and volume?

6 What is the boiling point of a liquid?

7 What is the relationship between the boiling point and the external pressure?

8 What are fractions of petroleum?

9 What is specific heat?

10 How can you calculate the quantity of heat for heating?

11 What is the specific latent heat of evaporation?

12 How can you understand the term "latent"?

13 How can you distinguish the high and low heat of combustion?

29.3 Translate into English

1 Khối lượng riêng là một thông số quan trọng để đánh giá dầu mỏ

2 Nhiệt độ sôi của một phân đoạn dầu mỏ phụ thuộc vào thành phần định tính và định lượng của nó

3 An toàn cháy nổ của một phân đoạn dầu mỏ phụ thuộc vào nhiệt độ chớp cháy và nhiệt độ

tự bắt cháy của nó

4 Cần phải chú ý tới giới hạn cháy nổ của một phân đoạn dầu mỏ khi chế biến nó

29.4 Write a short summary of the text

UNIT 30 BASIC PHYSICO-CHEMICAL PROPERTIES OF

PETROLEUM AND PETROLEUM PRODUCTS (CONTINUED)

f Viscosity (internal friction)

Viscosity is the ability of a liquid (or gas) to resist the motion of a layer relative to

other layers As regards petroleum products, a distinction is made between dynamic, kinematic and relative viscosity

Dynamic viscosity  is measured in pascal-second (Pa s) An inverse value of

dynamic viscosity is called fluidity

In process calculations and for testing the quality of many petroleum products, use is

made of kinematic viscosity, which is the ratio of the dynamic viscosity  to the relative density of a liquid, d, at the same temperature, i.e

 = /d Kinematic viscosity  is measured in square meter (square millimeter) per second (m2/s, mm2/s)

In practical calculations, especially for quality control of petroleum products, use is

often made of relative viscosity which is the time of efflux of 200 ml of a petroleum product

at the testing temperature related to the time of efflux of the same volume of distilled water at

20oC (the time of efflux of 200 ml of water at 20oC is what is called the water number of a viscometer)

Viscosity-temperature relationships Viscosity becomes lower with increasing

temperature and vice versa The pattern of variation of viscosity with temperature is an important characteristic of petroleum products, especially of lubricating oils These variations can be determined by various methods, for instance, by the ratio of the viscosity at 50oC to that at 100oC, which is now specified for many lubricating oils, or by the viscosity index; the latter is found from monograms for the known values of viscosity at 50oC and 100oC With a higher ratio of viscosities, the temperature curve of viscosity is steeper and on the contrary with a lower ratio, the curve is less steep and the quality of the oil is better

g The Setting and Fusion points

When being cooled, petroleum and petroleum products gradually loss mobility and

can set (solidify) notwithstanding the fact that they contain some substances that might be liquid at the temperature considered

The setting (solidification) point of a petroleum product is the temperature at which

the product loses mobility under strictly specified testing conditions The loss of mobility and

freezing of petroleum and petroleum products depend mainly on the content of hydrocarbons

which are solid (at the normal temperature) The higher the content of such hydrocarbons (in

dissolved or crystalline state), the more quickly the product loses its mobility during cooling, i.e., the products have a relatively high setting point Tarry products and asphaltenes can retard somewhat the crystallization of solid hydrocarbons that is why the setting point of detarred products is always higher than that of the distillates from which they have been obtained

During cooling to their setting point, white petroleum products pass through a number

of intermediate stages- the stage of turbidity (blushing) and that of the beginning of crystallization The highest temperature at which crystals (say, of benzene, etc.) can be

detected in the cooled fuel by naked eye is called the temperature of the beginning of crystallization, or the chilling temperature (point) The temperature at which crystals of

hydrocarbons (mainly of paraffins) start to precipitate and make the product turbid is called

the blushing temperature (point) Along with the temperature of chilling of liquid petroleum

products, the temperature of fusion of some products which are solid at normal temperature (paraffin and ceresin) is also practical importance

The fusion point is the temperature at which a solid product becomes liquid under strictly specified testing conditions

With these constants being known it is possible to select properly the method of petroleum processing and take the required measures to ensure pipeline transportation, especially in winter time, and also to choose the methods of storage and transportation of solid products having a high chilling point

h Flash and Ignition Points Self- ignition temperature Explosibility

The fire hazard of petroleum products is judged by their flash, ignition and self-

ignition temperatures (point) At lower values of these characteristics, a product is more fire- hazardous

The flash point is the temperature, at which a mixture of air and vapors of a product

being heated under standard conditions ignites on contact with an ignition source, but the product proper is not ignited and the flame is damped For light petroleum products (with the flash point not above 50oC) the flash point is measured in a closed apparatus and that of heavier products (with the flash point above 70oC) can be determined in an open vessel The product to be tested is poured into the apparatus and a thermometer is put inside With light products, the apparatus is covered by a lid with a window which can be closed by a gate During the test, the window is opened periodically and a burner is brought close to it In an open apparatus, the burner is moved close to the liquid surface Tests in an open apparatus give a higher value of a flash point, since the vapor formed are partially dissipated to the surroundings

In further heating, a petroleum product can ignite at a certain temperature This

temperature is called the ignition point

There is a certain relationship between the fractional composition of a product and its flash and ignition points: lighter hydrocarbons in its composition lower these points For instance, gasoline has the flash point below – 50oC, whereas the flash point of fuel oil is above 110oC

According to international recommendations, easily igniting liquids include those flash point is below 61oC (in a closed vessel) or 66oC (in an open vessel) These liquids can

be ignited by a short action or even a small ignition source (say, a spark) and without preliminary heating

The temperature of self- ignition of a petroleum product is lower at a higher content

of heavy hydrocarbons This is the temperature at which a product ignites spontaneously on contact with the air, i.e., in the absence of flame or spark Some products, such as fuel oils, goudron, soot and coke, self- ignite quite easily at a temperature slightly above 300 0C Self- ignition usually occurs in untight pipelines and apparatus in which petroleum products are at a temperature above their ignition point It is therefore essential to check the equipment for tightness to prevent self- ignition and fires

Explosibility In petroleum processing plants, mixtures of vapors of some products

with air may be explosive Such mixtures may form in open air, in closed premises, and inside processing equipment A mixture of vapors of a product with air becomes explosive when the concentration of the vapors in mixture exceeds a definite limit At lower concentrations, the mixture is not explosion hazardous, since the greatest portion of the heat evolved in the ignition zone is spent to heat up the air A mixture cannot explode, too, if it contains little air and therefore there is not enough oxygen to sustain combustion

The lowest concentration of vapors of a petroleum product (or other substance) in the

air at which explosion is probable is called the lower explosive limit, and the highest concentration of vapors at which explosion is still possible is respectively the upper explosive limit The concentration range between the two limits in which an explosion can take place on

contact with open fire (or spark) is called the explosibility range

The upper and lower explosive limits and the explosibility are different for various vapors and gases The highest permissible concentration of vapors of a product in working

premises depends on the composition of that product

Exercises 30.1 Read and translate into Vietnamese

Viscosity, friction, resist, dynamic, kinematic, inverse, fluidity, efflux, viscometer, variation, lubricate, monogram, steeper, setting point, fusion point, mobility, solidify, retard, detar, turbidity, blushing, naked eye, chilling point, precipitate, ceresin, transportation, flash point, ignition point, self-ignition point, explosibility, judg, damp, ignite, lid, periodical, dissipate, preliminary, spontaneous, spark, goudron, soot, coke, tightness, explosive, explode, premise, sustain, lower explosive limit, upper explosive limit, explosibility range

30.2 Answer the following questions

1 What is the viscosity of a liquid?

2 How many types of viscosity of liquid do you know?

3 What is the relationship between the viscosity index and the quality of oil?

4 What is the setting point of a petroleum product?

5 Why do the setting points of distillates decrease after detaring?

6 What is fusion point?

7 What is flash point?

8 How can you measure the flash point?

9 What is ignition point?

10 What is temperature of self-ignition?

11 When does the explosibility happen?

30.3 Translate into English

1 Độ nhớt phụ thuộc vào thành phần định tính và định lượng của phân đoạn và nhiệt độ của môi trường

2 Các thông số nhiệt độ chớp cháy, nhiệt độ tự bắt cháy và giới hạn cháy nổ đặc trưng cho mức độ an toàn cháy nổ của sản phẩm

3 Giới hạn nổ dưới là nồng độ thấp nhất của hơi của một sản phẩm dầu mỏ trong không khí

mà sự nổ có thể xảy ra

30.4 Write a short summary of the text

UNIT 31 DISTILLATION OF PETROLEUM

The property that differentiates most petroleum products from each other is

"volatility", or tendency to vaporize More volatile products are called "lighter", less volatile products, "heavier" The volatility of a product is determined, of course, by the boiling points

of its components Inasmuch as distillation separates liquid by boiling points, distillation is the principal separation process

Basic components of distillation

There are varieties of configuration for distillation columns, each designed to perform specific types of separations A simplified way of classifying distillation column is to look at how they are operated In this manner, the two major types are batch and continuous columns

In the batch operation, the feed to the column is introduced bath-wise That is, the column is charged with a ‘batch’ and then the distillation process is conducted When the designed separation is achieved, a next batch of feed is introduced In contrast, continuous column posses a continuous feed stream No interruptions occur unless there is a problem or upsets with the column or surrounding process units They are capable of handling high throughputs and are the more common of the two types

Continuous column can be further classified according to: (1) the nature of the feed that they are processing (binary column feed contains only two components, and multicomponent column – feed contains more than two components; (2) the number of product streams they have (multiproduct column – column has more than two product streams); (3) where the extra feed exists when it is used to help with the separation (extractive distillation- where the extra feed appears in the bottom product stream, and azeotropic distillation- where the extra feed appears at the top product stream); (4) the type of column internals (tray column – where trays of various designs are used to hold up the liquid to provide better contact between vapor and liquid, and hence achieve better separation, and the packed column- where instead of trays, packings are employed to effect contact between vapor and liquid)

There are several important components in a distillation column, each of which is used either to transfer heat energy or enhance mass transfer The major components in typical distillation are:

- A vertical shell where the separation of liquid components is carried out,

- Column internals such as trays/plates and/or packings, which are used to enhance component separation,

- A reboiler to provide the necessary vaporization for the distillation process,

- A condenser to cool and condense the vapor leaving the top of the column

- A reflux drum to hold the condensed vapor from the top of the column The liquid (reflux) is recycled back to the column

The column internals are housed within a vertical shell, and together with the condenser and reboiler, constitute a distillation column A schematic of typical distillation unit with a single feed and two product streams is shown in figure 12

The liquid mixture that is to be processed is called the feed The feed is introduced usually somewhere near the middle of the column to the tray known as the feed tray The feed tray divides the column into a top (enriching or rectification) section and a bottom (stripping) section The feed flows down the column where it is collected at the bottom in the reboiler Heat is supplied to the reboiler to generate vapor The source of heat input can be any suitable fluid, although in most chemical plants this is normally steam In refineries, the heat source may be the output streams of other columns The vapor raised in the reboiler is re-introduced into the unit at the bottom of the column The liquid removed from the reboiler is known as the bottom product or simply, the bottoms The vapor travels up the column, and as it exits the top of the unit, it is cooled by the condenser The condensed liquid is stored in a holding vessel known as the reflux drum Some of this liquid is recycled back to the top of the column and this is called the reflux The condensed liquid that is removed from the system is known

as the distillate or top product

Extractive and Azeotropic Distillation

Because distillation separates by virtue of differences in volatility, distillation cannot normally be used to separate close- boiling materials However, when the materials to be separated are chemically dissimilar, modified distillation procedures can be used Examples are the separation of butenes from butanes and of toluene from isooctane In such cases; an extraneous liquid can be added which has an affinity for one of the components in the charge;

as a result, the relative volatilities of the original components change, and separation becomes possible If the added material is less volatile than the original components, it is added at the top of the column and withdrawn from the bottom, and the operation is called extractive distillation If the added material is more volatile than the original components, it is added at the top of the column or with the feed and is withdrawn in the overhead product; the operation

is then called azeotropic distillation

Figure 12 Basic component of distillation

Solvents and Entrainers In extractive distillation, the extraneous liquid is called a

solvent; in azeotropic distillation, it is called entrainer In either case, its effectiveness is determined by its concentration in the liquid phase Consequently, the boiling point of an entrainer is limited; it must be about as volatile as the lighter feed components so that it will pass overhead, but it must not be so volatile that it will disappear from the downflowing liquid stream much above the bottom of the tower An entrainer must be separable, of course, from the overhead product- by distillation or by some other technique Similarly, a solvent in extractive distillation must be separable from the bottoms product How the entrainer or the solvent is separated from the overhead or bottoms product is an important consideration, because large volumes must be used To be effective in changing the relative volatilities of the original components, an entrainer or a solvent must constitute at least 40% of the liquid phase (60), and its concentration is usually much higher

Effects of Reflux In extractive distillation, reflux has two opposing effects By

increasing the counterflow of liquid and vapor, increasing the reflux promotes the separation However, increasing the reflux lowers the concentration of the solvent in the liquid streams; this lessens its effect in spreading the volatilities of the original feed components and thus retards their separation Because of these conflicting effects, there is apt to be sharp optimum

in the reflux rate for an extractive distillation operation

Feed Preparation Only narrow-boiling materials are charged to extractive or

azeotropic distillation The reason may be seen most readily from an example Consider extractive distillation for the separation of toluene from a mixture with isooctane, which

normally boils very closely to toluene Lower- boiling materials (like hexane and benzene) and higher - boiling materials (like isononanes) are first separated by ordinary distillation The sharpness of removing the light ends affects only the amount of material charged to extractive distillation On the other hand, the purity of the toluene product will depend upon the sharpness of prefractionating the heavy ends out of the feed

How poor removal of heavy ends affects product purity may be seen by considering the normal volatilities of the feed components and how they are affected by the presence of a solvent Toluene and isooctane boil together, and isononanes are about half as volatile In the concentration usually employed, a solvent approximately doubles the volatilities of the paraffins relative to toluene In the presence of the solvent, then, the isononanes have about the same volatility as toluene, and their separation is very difficult, and sometimes impossible

Even when heavy materials can be taken overhead in extractive distillation, they may

be very undesirable in the feed When phenol is used as the solvent, for example, volatility relationships are such that heavy paraffins in the overhead tend to carry some phenol with them Phenol is expensive, and only small losses can be tolerated

Exercises 31.1 Read and translate into Vietnamese

Differentiate, volatility, tendency, inasmuch, simplify, batchwise, conduct, interruption, throughput, binary, tray, tray column, enhance, vertical, horizontal, plate, packing, reboiler, reflux, recycle, schematic, feed tray, enriching, rectification, stripping, generate, refinery, bottom product, bottoms, distillate, extraneous liquid, affinity, charge, extractive distillation, azeotropic, entrainer, extraneous, consequently, overhead, disappear, downflowing, oppose, opposing, counterflow, lessen, spread, conflict, apt, narrow-boiling materials, sharpness, fractionate, prefractionate, overhead, tolerate

31.2 Answer the following questions

1 What are the major components in a typical distillationn unit?

2 What are the distilling towers?

3 Where can they withdraw product of distillation?

4 What is reflux?

5 What are the rectifying section and stripping section?

6 What are the purposes of the rectifying section and stripping section?

7 When must they add the extraneous liquid in distillation?

8 What is the extractive distillation?

9 What is the azeotropic distillation?

10 What is a solvent or an entrainer?

11 What can you say about the boiling point of entrainer?

12 What are the important characteristics of solvent or a entrainer?

13 Which materials are used in extractive or azeotropic distillation?

31.3 Translate into English

1 Chưng cất là quá trình tách một hỗn hợp của hai hay nhiều chất thành các phân đoạn chứa các cấu tử của nó

2 Bộ phận chính của một hệ chưng cất là tháp chưng cất Nó bao gồm bình chưng, bộ phận ngưng tụ và thiết bị bay hơi

3 Nếu hỗn hợp cần tách là các chất có nhiệt độ sôi gần nhau thì phương pháp chưng cất đẳng phí hoặc chưng cất chiết được sử dụng

4 Phần cột phía trên đĩa nạp liệu gọi là phần chưng và phần nằm dưới đĩa nạp liệu gọi là phần cất

31.4 Write a short summary of the text