THERMAL MATERIALS DESICCANT MATERIAL

Vietnam has a climate with high humidity that often affects the production and storage of goods. When the weather changes, changing the storage place from the production place to the consumers hands, the conditions in each place are different, causing the quality of the product to decrease, fermentation, mold, ... So the study found out the Materials with a hygroscopic ability are essential for businesses. In transportation, especially shipping containers by sea and the use of desiccant material is almost mandatory. Understanding that importance, the group decided to choose the topic desiccant for the subject report. Thereby, somewhat generalized physical and chemical properties as well as application of this material in production technology in general and in particular to heat and cold technology. This essay aims to address the above issues to better understand the desiccant materials and then use them properly to meet the requirements and bring economic efficiency. Since the information has been compiled from many different information sources, the main part is in the textbooks and the internet and has been thoroughly checked by the team members but there are no errors, group 10 looks forward to comment and evaluation. of the master.

HCM CITY UNIVERSITY OF TECHNOLOGY EDUCATION

FALCUTY OF HIGH QUALITY

SUBJECT: THERMAL MATERIALS TOPIC: DESICCANT MATERIAL

LECTURER:

Group 10

HCM City 11/2020

TEACHER’S ASSETMENT

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LECTURER’S SIGNATURE

2.2 Calcium sulfate (CaSO4)

2.3 Magnesium percolrate Mg(ClO4)2

3 Desiccant reacts chemically with water.

TABLE OF FIGURES

Figure 1: Silicagel

figure 2: Activated clay in real life

Figure 3: Zeolite structure

Figure 4: Crystal structure of CaCl2 10

Figure 5: Desiccant powder 11

Figure 6: Desiccant package CaCl2

Figure 7: Crystal structure of CaSO4

Figure 8: Calcium sulfate

Figure 9: Crystal structure of Mg(ClO4)2

Figure 10: Desiccant Mg(Clo4)2

Figure 11: Crystal structure of CaO

Figure 12: Chemical component of ethyleneglycol

Figure 13: Chemical components of C4H10O3

Figure 14: Activated aluminum particles

INTRODUCTION

1 Reason for picking this topic

Vietnam has a climate with high humidity that often affects the production andstorage of goods When the weather changes, changing the storage place from theproduction place to the consumers' hands, the conditions in each place are different,causing the quality of the product to decrease, fermentation, mold, So the study foundout the Materials with a hygroscopic ability are essential for businesses In transportation,especially shipping containers by sea and the use of desiccant material is almostmandatory

Understanding that importance, the group decided to choose the topic "desiccant"for the subject report Thereby, somewhat generalized physical and chemical properties

as well as application of this material in production technology in general and inparticular to heat and cold technology

This essay aims to address the above issues to better understand the desiccantmaterials and then use them properly to meet the requirements and bring economicefficiency Since the information has been compiled from many different informationsources, the main part is in the textbooks and the internet and has been thoroughlychecked by the team members but there are no errors, group 10 looks forward tocomment and evaluation of the master

2 Objective

Exploring and collecting information about the properties as well as features of thematerials with the ability to absorb moisture In the report, the group will focus onlearning about the most common materials Analyze the advantages and disadvantages itbrings, make our own objective judgment

3 Research subject and scope

Study subjects include fuel cells invented by scientists to improve moistureabsorption Scope of research on practical applications at home and abroad

4 Method of evaluation

In order to achieve the above objectives, the group will implement the followingresearch methods: Methods of collecting information - Synthesize scientific and objectivefactors to make some more suggestions

CHAPTER I DEFINITION AND CATEGORIZATION OF DESICCANT

Desiccant materials are classified based on the principle of hygroscopicity:

• Category 1: Create mechanical bonds with moisture

These are materials with tiny holes inside (the size of the hole is only a few Ao), so

it is able to retain water

+ Silicagel SiO2

+ Al2O3 activated clay

+ Zeolite

• Classification 2: Creates hydrated crystals and hydrates

Materials that have the ability to bind with water

+ Calcium Sulfate CaSO4

+ Calcium chloride CaCl2

+ Magnesium Peclorate Mg(ClO4)2

• Classification 3: Chemical reaction with water to form new substances

+ Lime CaO

+ Phosphorus Pentaoxit (P2O5)

• Class 4: Liquid desiccant

+ Ethylene glycol (MEG), Diethylene (DEG)

Nowadays, science and technology have been inventing a variety of new desiccantmaterials with higher ability to absorb moisture and improve economic efficiency.

3 Requirements for desiccant materials

 Has a high hygroscopic ability based on the amount of moisture absorbed per unit volume

 Ability to absorb harmful foreign acids and gases generated in the process

 Ability to regenerate easily through heat or chemicals

 Not as a catalyst for harmful reactions

 Relatively cheap, easy to find

 In refrigeration system

 Has a high hygroscopic capacity based on the amount of moisture absorbed perunit of volume even at low steam specific pressure

 Ability to absorb harmful foreign acids and gases generated during the operation

of the refrigeration system

 The ability to absorb moisture and harmful products does not depend on thetemperature within the operating temperature range

 Do not interact with refrigerants, lubricants, moisture and by-products as well asinorganic and organic machine building materials to create other harmfulchemicals

 Do not act as a catalyst for harmful reactions in refrigeration systems

 Has a fixed shape, does not fall apart by refrigerant, clogging the throttle andpipes

In practice there is no ideal desiccant material One must choose desiccantmaterials for each application case to take full advantage of their advantages and limittheir disadvantages

CHAPTER II STRUCTURE AND MAJOR PROPERTIES OF SOME

DESICCANT MATERIALS

1 Desiccant materials create mechanical bonds

1.1 Silicagel

1.1.1 General introduction of silicagel

Silicagel or silicic acid gel is a very naturally occurring substance, but is actuallysilicon dioxide Its simple chemical formula is SiO2.nH2O (n<2), it is produced fromsodium othosilicate (Na2SiO4) or Silicon TetraCloride (SiCl4) Nowadays, silicagel plays

a very important role in chemical technology from simple to complex

In everyday life, we often find silica gel in small packages placed in medicinebottles, in food packages, in electronic products There, the silicagel acts as a desiccant tokeep the above products from being damaged by moisture

1.1.2 Structure and Properties of Silicagel

a) Structure

Silicagel in nature is a solid, porous, and amorphous form of SiO2 In thelaboratory, the process of gelation of silica sol causes silicagel to form in the form ofsilica gel, dehydrating it, resulting in dry silicagen

Silicagel is a continuous, 3-dimensional lattice of colloidal silica particles Thesilicate solution is acidified to form silicic acid In this silicic acid system, the gel form isoften thought to be formed from the aggregation of Si (OH) 4 groups to form siloxanechains The initial state of Si (OH) 4 polymerization is related to the formation of SiO2

particles carried on the surface of silanol groups (≡SiOH) These individual particles arecalled micelles When these micelles collide with each other, the ≡SiOH groups on thesurface will gather to form Si-O-Si Thus, silicagen can be considered simply as a three-dimensional lattice of micelles linked together

The silanol groups (≡SiOH) have the ability to bind to form siloxane "bridges" (=Si-O-Si =) so the silicagel surface forms as an aggregate consisting of water (physicaladsorption), and silicon Oxides bound to hydroxyl groups

The melting point is about 1710oC

The grain diameter is about 3-10 mm

c) The ability to absorb moisture

Silica gel absorbs moisture through capillary phenomenon in its millions of tinyhollow cavities, steam is sucked in and cling to the void inside the particles Silica gel canabsorb as much water as 40% of its weight and can relatively reduce the relative humidity

in the sealed container by up to 40%

In addition, the ability of silicagel to absorb moisture depends on the relativehumidity of the environment, but it cannot absorb moisture in the air, but it follows thebalance rule:

+ When the air humidity is about 20%, it can absorb to about 12% humidity + If the air humidity is about 50%, it can absorb up to 23% humidity

+ When the air is about 90%, it can absorb up to 31% humidity

1.2 Activated clay

FIGURE 2: ACTIVATED CLAY IN REAL LIFE [2]

1.2.1 General introduction

Derived from natural minerals, dust-free, fiber-free, leak-proof, non-corrosive andnon-toxic Active hygroscopic clay is extremely safe and environmentally friendly due toits chemically inert properties and natural origin.

1.2.2 Stucture

Pelleted reactive hygroscopic clay is a biodegradable material capable ofabsorbing natural water up to 75% of its own weight Active hygroscopic clay combineswith polymers, mixed with calcium chloride to enhance its adsorption capacity Activedesiccant clay is used industrially as a desiccant material to protect goods and products incontainers and containers Active hygroscopic clay has a high hygroscopicity undernormal temperature and humidity conditions

Advantages

 Environmentally friendly, extremely safe, odorless, non-toxic, non-corrosive, andeasy to regenerate

 Great ability to absorb toxic gas

 High water absorption

 Produce from 100% natural clay mineral

 Long term product protection

1.3.2 Molecular structure

Assuming if the zeolite is purely SiO4, it is hydrophobic and its lattice iselectrically neutral However, because the zeolite is formed when aluminum displaces

some of the silicon atoms in the crystalline lattice of SiO, the zeolite crystal lattice has anegative charge To ensure charge neutrality, zeolites require positive ions (cations) tocompensate for residual negative charges In nature or in the initial synthetic form, thesecations are usually alkali metal cations (Na+, K+ ) or alkaline earth (Mg2+, Ca2+ ).

These cations are outside the zeolite crystal lattice and are easily involved in ionexchange processes with other cations It is through that property that it is possible todenature the zeolite and give it new properties and applications in adsorption andcatalytic processes The general formula of zeolic molecules is written as follows:

M2/mO.Al2O3nSiO2pH2O

In which: m valence metal M

n is the ratio of SiO2 / Al2O3

p number of molecules fills inside the void

1.3.3 Application

In recent years, molecular sieve materials play an increasingly important role inindustrial catalysis, especially zeolite It increasingly replaces the former catalysts, thusattracting the attention of many scientists around the world Zeolite is an inorganic typefound in nature (about 40 different zeolite structures and some are synthesized from avariety of materials such as individual Si, Al, kaolin (200 types of synthetic zeolites).They are widely used in many fields of science as well as industry as catalysts,adsorbents and ion exchangers.They are also used for gas separation and purification, andmagnetic radioactive ion separation radioactive wastes and especially catalysts for manyhydrocarbon metabolism thanks to its outstanding properties compared to other types ofcatalysts such as large specific surface, acid-force adjustable and Acid concentration,

F IGURE 3: Z EOLITE STRUCTURE [3]

porous crystal structure with uniform capillary size suitable for many types of moleculeswith sizes from 5AO - 12AO and good denaturing ability.

Therefore, zeolite is evaluated as a highly stable, active and selective catalyst Thediscovery of natural zeolites and their synthesis have made a big turning point in thechemical industry, especially in the oil and gas industry Zeolite application increasesboth quantity and quality of petroleum products It is used in most important stages suchas:

2 Desiccant material forms hydrated crystals and hydrates

Absorbents that wait for moisture through chemical bonding to form hydratedcrystals or carbohydrates such as calcium sulphate CaSO4, calcium chloride CaCl2 ormagnesium perchlorate Mg(ClO4)2 are of little significance in refrigeration Use of thesesorbents should be limited, especially calcium chloride is not suitable for refrigerants Ifused is not arranged on liquid lines

2.1 Calcium chloride

2.1.1 Concept

Calcium chloride or calcium chloride (CaCl2), which is the ionic compound ofcalcium and chlorine, acts as a typical halogen ion and is a solid at room temperature The density of the chemical calcium chloride – CaCl2 is 1.68 g/cm3

The melting point is 772oC

2.1.2 Chemical structure and preparation

The compound usually exists in crystalline form with 6 molecules of water with the chemical formula CaCl2.6H2O In addition we also have dihydrate calcium chloride CaCl2.2H2O and anhydrous calcium chloride CaCl2.

F IGURE 4: C RYSTAL STRUCTURE OF CALC2 [3]

In the laboratory, CaCl2 is created by:

CaCO3 + 2 HCl → CaCl2 + CO2 + H2O

In addition, when heating calcium chloride CaCl2, CaCl2.6H2O lost four molecules

of water converted to dihidrate, CaCl2.2H2O, which has white porous shape WhenCaCl2.2H2O is melted and dehydrated, it becomes anhydrous CaCl2 : a white, veryhydrophilic mass of crystals Partially decomposed, molten CaCl2 always contains somecalcium oxide calcium All calcium chloride CaCl2 chemicals are easily soluble in waterand ethanol, slightly soluble in acetone

2.1.3 Desiccant uses

Due to its strong hygroscopic properties, air or other gases can pass through pipescontaining calcium chloride to remove moisture

2H2O + CaCl2 → Ca(OH)2 + Cl2+ 2H2

Specifically, calcium chloride is commonly used to fill drying tubes to removemoisture from the air while allowing gas to pass It can also be added to certain liquidsolutions to remove mixed or suspended water The process of absorbing water isthermogenic and rapidly generates temperatures up to about 60°C (140°F) Because ofthis ability, it is known as a drying agent or desiccant.

This desiccant powder absorbs moisture by extracting water vapor in the air, thuspreventing the moisture inside the container from turning into mist and condensation Itthen begins to become a gel and continues to absorb moisture Absorbed water is retaineddue to the presence of a special binder encapsulated inside the tyvek layer (a special non-woven fabric that guarantees 1-way moisture absorption), thus preventing leakage

Powdered desiccant is capable of absorbing more than 150% - 200% of its ownweight (Example: 1kg bag to 2.5kg) and dehumidification time lasts up to 2 months,ensuring the safety of your goods during transportation While Silica gel or Clay (clay) isthe most commonly used desiccant on the market today, usually only up to 25-30% of itsweight Thus, for each container, it is only necessary to use less quantity while ensuringefficiency, as well as reducing most costs in storing goods

F IGURE 5: D ESICCANT POWDER [4]

F IGURE 6: D ESICCANT PACKAGE CACL2 [4]

They are often used for shipping, moisture-proof for containers, goods need to bestored when transported long distances With new formulations, calcium chloridedesiccants are mixed with several other ingredients, causing them to become cohesiveand limit water flow, although this reduces the hygroscopic ability of the calciumchloride desiccator but is necessary It is listed as an approved food additive in theEuropean Union as a isolator and thickener additive with E number E509 The anhydrousform has been approved as a packaging aid to ensure dryness In addition, it is the salt ofcalcium with strong force with H2O, CaCl2 has the ability to absorb water greater than>120% by weight, making the humidity outside the air drop to the maximum quickly,packaging powder packaging Calcium chloride is a two-layer packaging with backflowresistance

2.2 Calcium sulfate (CaSO 4 )

2.2.1 Concept

Calcium sulfate (or calcium sulphate) with chemical formula CaSO4 is a commonindustrial and industrial chemical However, it exists in the following three basic forms:anhydrous calcium sulfate (CaSO4), calcium sulfate hemihydrate (CaSO4.0,5H2O) alsoknown as gypsum mortar, Calcium sulphate dihydrate (CaSO4.2H2O) occurs in naturebelow plaster form In the γ-anhydride (almost anhydrous form), it is used as a desiccant

In nature, calcium sulphate is a translucent, white crystalline rock, a form sold under thename Drierite has a blue or pink color due to its infiltration with cobalt chloride salts,