CYANIDE in WATER and SOIL: Chemistry, Risk, and Management - Chapter 4 pdf

54 Cyanide, a natural compound found in plants and animals, is believed to be a key component in the in the manufacture of a number of products including synthetic fibers and plastic, go

4 of Cyanide

George M Wong-Chong, David V Nakles, and

Richard G Luthy

CONTENTS

4.1 Production of Cyanide Compounds 42

4.1.1 Hydrogen Cyanide 42

4.1.2 Production of Sodium Cyanide 42

4.1.2.1 Global and U.S Production 42

4.1.2.2 Production Methods 44

4.1.3 Production of Ferrocyanides 48

4.1.4 Production of Acrylonitrile 49

4.1.4.1 Global and U.S Production 49

4.1.4.2 Production Methods 50

4.2 Incidental Industrial Production of Cyanide 51

4.2.1 Coking and Gasification of Coal 52

4.2.2 Blast Furnace Operations 52

4.2.3 Aluminum Production 52

4.2.4 Municipal Waste and Sludge Incineration 53

4.3 Summary and Conclusions 53

References 54

Cyanide, a natural compound found in plants and animals, is believed to be a key component in the

in the manufacture of a number of products including synthetic fibers and plastic, gold, agricul-tural herbicides, fumigants and insecticides, dyes and pigments, animal feed supplements, chelating breakdown of the overall industrial use of hydrogen cyanide, including as a feedstock chemical for that use cyanide compounds in the manufacturing process, along with the cyanide compounds employed

The cyanide industry traces its history to about 1710 with the discovery of Prussian Blue (or ferric ferrocyanide), an iron cyanide compound, which at that time was used almost exclusively in dye-ing [3,4] However, it was not until about 1885 that substantial commercialization of cyanide, specifically potassium cyanide, occurred with the development of the McArthur-Forest process, known today as the cyanidation process, for the extraction of gold from low-grade ores [3] This discovery represents a major sustaining factor in today’s cyanide commerce, with about 20%, or an estimated 0.6 million tons, of the worldwide production of cyanide used in mining [5,6]

This chapter discusses the manufacture of cyanide compounds, especially hydrogen cyanide, sodium cyanide, ferrocyanide, and acrylonitrile, as well as the uses of these compounds and their

41

agents for water treatment, and specialty chemicals and pharmaceuticals [1,2].Table 4.1presents a production of other cyanide compounds, as of 1991 Table 4.2presents a list of some industries origin of life (seeChapter 1) and plays a pivotal role in today’s commerce It is a basic component

TABLE 4.1

Use of Hydrogen Cyanide in Manufacturing in the United States

(1991 Estimate)

Cyanuric chloride for pesticides and agricultural products 9

Misc.: specialty chemicals and pharmaceuticals 3

Source: Data from Pesce, L.D., Kirk–Othmer Encyclopedia of Chemical Technology,

Vol 7, John Wiley & Sons, New York, 1993.

production rates The chapter also discusses those industries where cyanide production is an incidental occurrence, such as in coking and gasification of coal, metal ore reduction in blast furnaces, the reduction of alumina, and municipal waste and sludge incineration

4.1 PRODUCTION OF CYANIDE COMPOUNDS

In 2001, the worldwide production of hydrogen cyanide was approximately 2.6 million tons [6] The U.S production in the period 1983 through 2001 was 0.33 to 0.75 million tons per year, as shown in There are four commercial processes for the production of hydrogen cyanide Two of these are synthesis processes involving the reaction of ammonia, methane (natural gas), and air over a platinum catalyst: (1) the Andrussow process and (2) the Blausaure–Methan–Ammoniak (BMA) process

A third process, the Shawinigan process, uses a carbon fluid bed in an electrical fluohmic furnace

to react ammonia and propane The fourth process is the acrylonitrile production process where hydrogen cyanide is produced as a by-product and which accounts for about 30% of worldwide cyanide

The Andrussow process, which is by far the dominant manufacturing process, produces hydrogen cyanide via the following reaction [2]:

recovery/recycle of ammonia and waste heat-design features that improve the efficiency and economy

of the process Details of the process are available in the Kirk–Othmer Encyclopedia of Chemical Technology [2].

4.1.2.1 Global and U.S Production

The McArthur-Forest patent for gold extraction from ore with cyanide was issued in 1887 and the cyanidation process was first used in the Crown Mine in New Zealand and then elsewhere in the

Table 4.3

supply [2] Table 4.4 presents summary information about the synthesis processes for hydrogen

Figure 4.1presents a schematic flow diagram of the Andrussow process This diagram shows the

TABLE 4.2

Use of Cyanide Compounds in Manufacturing Industries

Primary cyanide compounds

Electroplating Potassium- or sodium-cyanide

(degreasing) Propionitrile (solvent, dielectric fluid) Nickel cyanide

Silver cyanide Barium cyanide Zinc cyanide Copper cyanide Hydrogen cyanide Cyanogen chloride (metal cleaner) Mercuric potassium cyanide (mirror manufacturing)

[14–18]

Fire retardant Potassium ferrocyanide [19,20]

Fumigant, poison gas,

pesticides,

insecticides,

parasiticide

Cyanogen Cyanogen chloride Cyanogen bromide Zinc cyanide Copper cyanide Calcium cyanide Hydrogen cyanide Ammonium thiocyanate (pesticides)

[14,15]

Malononitrile Cyanogen bromide Barium cyanide Calcium cyanide Ferrocyanide (used as a flotation agent for copper and lead/zinc separation)

[14–17]

Petroleum Malononitrile (lubricating oil additive)

Propionitrile (solvent)

[15]

Photography Ferricyanide bleach

Mercuric cyanide Hydrogen cyanide

[17,22–24]

Pharmaceuticals

(includes antibiotics,

steroids, prescription

and nonprescription

drugs)

Ferricyanide Ferrocyanide Propionitrile Ammonium thiocyanate (ingredient in antibiotic preparations)

[14,15,22,24]

(continued)

TABLE 4.2

Continued

Primary cyanide compounds

Pigments, paints,

dyes, ink, personal

care products

Ferricyanide Ferrocyanide Ferric ferrocyanide (Prussian blue,

Fe4(Fe(CN)6)3)

Malononitrile Mercuric cyanide (germicidal soap) Copper cyanide (marine paint)

[15,25–27]

Road salt Sodium ferrocyanide

Ferric ferrocyanide (Prussian blue,

Fe4(Fe(CN)6)3)

Potassium ferrocyanide

[17,28–30]

Rocket and missile

propellant

Cyanogen Ammonium thiocyanate

[14,15]

Synthetic fiber,

acrylic fiber, nylon,

synthetic rubber

Malononitrile Adiponitrile (intermediate in the manufacture of nylon) Cyanogen bromide Cyanogen chloride Hydrogen cyanide (production of nylon and other synthetic fibers and resins) Ammonium thiocyanate (improve the strength of silks)

[14–16,31]

Source: Data from MPI, Final Technical Memorandum: Summary of cyanide investiation at

SRWTP and preliminary conclusions and recommendations, report by Malcolm Pirnie, Inc.,

Emeryville, CA to the Sacramento Regional County Sanitation District, Sacramento Regional

Wastewater Treatment Plant, Regulatory Compliance Group, Sacramento, CA, 2004.

1890s This process started the new field of hydrometallurgy With the advent of this process, world production of potassium cyanide rose from 5,900 tons per year in 1899 to 21,000 tons per year in

1915 [2,3] Sodium cyanide eventually replaced the potassium salt for economic reasons, and has been the cyanide salt used in hydrometallurgical gold extraction solutions for many years

Production and use of sodium cyanide has been growing Global annual usage of sodium cyanide

in 1989 was about 340,000 tons In the early 1990s, the total world production of sodium cyanide was estimated to be in excess of 450,000 tons In 2001, the global production rate was about 600,000 tons per year [2,6]

4.1.2.2 Production Methods

In 1906, Robine and Lenglen [3] cited 79 processes for the production of potassium cyanide:

10 processes involving extraction from ferrocyanide; 13 processes involving extraction from thiocyanate; 28 processes involving synthesis from atmospheric nitrogen; 24 processes involving synthesis from ammonia; and four other processes In 1891 through 1899, the Beilby process — involving synthesis from ammonia, sodium and potassium carbonate, and powdered charcoal — accounted for about 50% of the total European production of alkali cyanide [2] In 1900, the Castner

TABLE 4.3 Production of Hydrogen Cyanide

in the United States, 1983–2001

Productiona ,

a Production estimates for 1983–1988;

Source: Data from Pesce, L.D., Kirk–Othmer Encyclopedia of Chemical Technology, Vol 7,

John Wiley & Sons, New York, 1993.

Production estimates for 1989–2001; Source:

Data from Myers, E., American Chemistry Council, Washington, DC, personal commu-nication, 2002.

TABLE 4.4

Synthesis Processes for Hydrogen Cyanide

Shawinigan Carbon fluid bed in a fluohmic furnace 1350–1650 NH3and C3H8 Acrylonitrile process By-product 400–510 NH3, air, and C3H6

Source: Data from Pesce, L.D., Kirk-Othmer Encyclopedia of Chemical Technology, Vol 7, John Wiley & Sons,

New York, 1993.

NH 3 Fractionator

NH3/ Water

NH3 Absorber Steam

Waste-water

NH 3 Stripper

Diammonium

Phosphate

Solution

Monoammonium Phosphate Solution

Waste-Heat Boiler Reactor

NH3 Feed Air Feed

Natural Gas Feed

NH 3 Recycle

HCN Fractionator

HCN Absorber Coolers

HCN Stripper Acid

HCN/Water Steam

SO2

Waste Water

HCN/Water

HCN with SO Inhibitor 2

Waste Gases to Boiler or Flare Off-Gas Minus NH3

FIGURE 4.1 Schematic flow diagram of the Andrussow hydrogen cyanide production process (Source:

Pesce, L.D., Kirk–Othmer Encyclopedia of Chemical Technology, Vol 7, John Wiley & Sons, New York, 1993.

Reprinted with Permission of John Wiley & Sons, Inc.)

process replaced the Beilby process and dominated production through 1960 for both potassium and sodium cyanide For the production of sodium cyanide, the Castner process employs elemental sodium and a reaction with ammonia and carbon as follows:

Low yields and elevated costs led to the obsolescence of the Castner process This process was replaced by the neutralization or wet processes that react hydrogen cyanide from the Andrussow

or BMA processes with a sodium hydroxide solution:

Most modern, high tonnage production plants use essentially purified anhydrous liquid hydrogen cyanide to react with sodium hydroxide to produce a product consisting of 99% sodium cyanide The manufacturing process includes the evaporation of water and crystallization of the sodium cyanide Control of the process is critical to maximize the average crystal size; to avoid hydrogen

system

Condenser

Crystallizer System Filter

Air Heater

Dehumidifier Scrubber

Waste

Mixing Conveyor

Briquetter

Screens

Separator

Dust Scrubber

Cyclone

Product to packaging and storage

50% Caustic

Hydrogen cyanide

Steam

FIGURE 4.2 Production process flow diagram for sodium cyanide (Source: Pesce, L.D., Kirk–Othmer

Encyclopedia of Chemical Technology, Vol 7, John Wiley & Sons, New York, 1993 Reprinted with permission

of John Wiley & Sons, Inc.)

cyanide polymer formation, which produces an off-white product; and to minimize sodium formate formation, which reduces product purity Figure 4.2 presents a process flow diagram for a typical sodium cyanide production plant

An occasionally used, alternative process is the direct absorption of crude hydrogen cyanide gas from the manufacturing operation into a sodium hydroxide solution However, the purity of the sodium cyanide product is lower, that is, approximately 96 to 97% [2] The primary impurities are sodium carbonate and sodium formate

The formation of larger crystals facilitates the dewatering in the filtration step In many plants, the moist salt from the filter is passed through a mixing conveyor to destroy the lumps Often, heated air (450◦C) is passed through the cake on the filter and through the mixing conveyor Drying is completed

in a hot-air conveyor-dryer This approach to drying avoids the overheating of the sodium cyanide crystals, thus minimizing the formation of sodium formate in the dried product A slight excess of sodium hydroxide must be maintained at all stages of processing to maintain an elevated pH, which

prevents the formation of a black or brown hydrogen cyanide polymer The product, as shipped, must also contain a slight excess of sodium hydroxide, to ensure that the product yields clear solutions following arrival at its destination

Inherently, the sodium cyanide forms a 50-µm diameter crystal, yielding a dusty solid of low bulk

density that must be compacted or fused into larger particles for safer handling Due to the expense associated with melting the product for casting it in molds, most processes employ mechanical compacting devices that produce either briquettes or granular products The compaction process occurs using heat and pressure Most sodium cyanide is sold in dry form to minimize transportation costs although appreciable tonnage is also sold as a 30% aqueous solution [2] About 90% of today’s sodium cyanide is used in gold extraction [5,6]

Plants for the production of sodium cyanide, using these processes, are operating in the United States, Italy, Japan, the United Kingdom, Australia, Germany, and China

Ferric ferrocyanide, also known as Prussian Blue (Fe4[Fe(CN)6]3), was the first cyanide compound put to commercial use The compound was discovered by a Berlin color maker in 1704 [3] This led

to a long history of ferrocyanide chemistry, which has resulted in the use of these compounds in a wide variety of industrially significant applications A treatise on the chemistry of ferrocyanides [7] describes some 22 applications, and these are listed in Table 4.5

In the late 1700s through the early 1900s, ferrocyanide salts were produced by (1) the synthetic fusion of nitrogenous organic residues (e.g., animal blood, hides, hornes, waste/scrap leather, etc.), potash, and iron, and (2) the direct extraction from illuminating-gas and from the by-product

TABLE 4.5

Uses of Ferrocyanides and their Derivatives in Industry

Analytical chemistry

Anticaking agent

Blueprints

Case hardening and heat treatment of steel

Chemical synthesis: catalysts, reaction intermediates, and reagents

Chemotherapy

Corrosion inhibitors

Desulfurization of coke oven gas

Detergents

Dying of textiles

Electrical equipment treatment: corrosion resistance; arc stabilization and lowering of grounding resistance Electroplating

Minerals dressing, beneficiation, and mining

Pesticides

Petroleum refining: trace metals removal

Photography

Pigments and dyes

Pickling of steel

Rubber: peptizing agent, stabilization agent, and accelerator

Separation and identification of organic bases

Trace metals removal in fermentation

Source: Data from ACC, The Chemistry of the Ferrocyanides, American Cyanamid Co., New York, NY,

1953.

of illuminating-gas clean-up (e.g., spent iron oxide boxes for gas purification) [3] It was estimated that about 1.8% of the nitrogen in coal reacted to form hydrogen cyanide during coal gasification

In the direct gas extraction processes, the illuminating gas was scrubbed with an alkaline iron salt solution Robine and Lenglen [3] discussed in detail nine processes for the direct extraction of cyanide from illuminating gas, three processes for extraction from ammoniacal liquor, and 11 processes for recovering ferrocyanide from spent iron oxide

In the synthesis from nitrogenous organic matter, the process chemistry for making potassium ferrocyanide was thought to be:

In the first reaction, hydrogen cyanide is produced by the thermal breakdown of the organic matter

in an oxygen controlled environment (Equation [4.4]) Subsequently, the hydrogen cyanide reacts with potassium to form potassium cyanide The potassium cyanide, in turn, reacts with the iron to form potassium ferrocyanide as shown in Equation (4.5)

Today, ferrocyanide production utilizes the crude sodium cyanide, produced as described in Section 4.1.2, and ferrous sulfate to form sodium ferrocyanide:

The sodium ferrocyanide is recovered by crystallization as the decahydrate salt The potassium salt

is produced by reacting sodium ferrocyanide with calcium hydroxide and potassium chloride and carbonate according to the following reactions:

In earlier times, ca 1900, Prussian Blue was produced in a two stage process The first stage reacted potassium ferrocyanide and ferrous sulfate to form a grayish-white precipitate of potassium ferric–ferrocyanide In the second stage, the potassium ferric–ferrocyanide is oxidized

to the tetrairon(III) tris(hexakiscyanoferrate), Fe4[Fe(CN)6]3[3] Today, the production of Prussian Blue is more direct, where ferrocyanide is reacted with excess iron(III) to produce the intense blue precipitate [2]

Acrylonitrile [C3H3N], also called vinyl cyanide, is among the top 50 chemicals produced in the United States as a result of the tremendous growth in its use as a starting material for a wide range of chemical and polymer products Acrylic fibers remain the largest use of acrylonitrile Other significant uses are resins and nitrile elastomers and as an intermediate in the production of adiponitrile and acrylamide

4.1.4.1 Global and U.S Production

Worldwide production of acrylonitrile was approximately 3.2 million tons in 1988 [8] As shown States In the United States, BP Chemicals dominated production, supplying more than one-third of domestic production Nearly one-half of the United States production was exported in 1988, with most going to Japan and the Far East [8] This export market grew steadily from the mid-1970s

inTable 4.6, more than one-half of that production was located in Western Europe and the United

TABLE 4.6 Worldwide Acrylonitrile Production, 1988

Source: From Brazdil, F., Kirk-Othmer Encylopedia of Chemical Technology, Vol 1, John Wiley & Sons, New

York, 1993.

TABLE 4.7 Worldwide Acrylonitrile Demand, 10 3 Tons per Year

Source: Data from Brazdil, F., Kirk–Othmer Encyclopedia of Chemical Technology, Vol 1, John Wiley & Sons, New York, 1993.

to 1988 During this period, it increased from 10% in the mid-1970s to 53% and 43% in 1987 and

1988, respectively The large exports to the Far East were the result of higher raw material costs (i.e., propylene costs) relative to the United States A more detailed breakdown of the world demand for acrylonitrile for the period between 1976 and 1988 is provided in Table 4.7 Growth in demand during this period averaged about 3.6% per year between 1984 and 1988 Projections beyond 1988 were 3% per year through 1993

4.1.4.2 Production Methods

Prior to 1960, processes based on either ethylene oxide and hydrogen cyanide or acetylene and hydrogen cyanide were used to produce acrylonitrile Growth in the demand for acrylic fibers around

1950 spurred improvements in process technology and resulted in the discovery of a heterogeneous vapor-phase catalytic process This process, which produced acrylonitrile using selective oxidation

of propylene and ammonia, is commonly referred to as the propylene ammoxidation process This process was introduced in 1960 and eventually displaced all other acrlyonitrile manufacturing pro-cesses As of 1988, over 90% of the approximately 3.2 million metric tons of acrylonitrile produced worldwide each year was manufactured using the propylene ammoxidation process [8]