ACETYLENE INDUSTRIAL MANUFACTURING PROCESS

ACETYLENE INDUSTRIAL MANUFACTURING PROCESS

Reaction

RAW MATERIAL REQUIREMENT TO MAKE 1 METRIC TON OF ACETYLENE

Calcium Carbide (85%)                   : 3490 kg

Water                                                   : 28,825 kg

Calcium Carbide is formed when Lime (essentially free of phosphates and Magnesium Carbonate) and Coke (with low ash content), mixed in a ratio of 60:40 are heated to a temperature of 2000 to 2100 degree C in an electric furnace. The Carbon Monoxide may be recovered and used as a fuel in lime kilns or as a raw material for chemical synthesis. The liquid Calcium Carbide is allowed to cool and solidify for 24 to 48 hours and is then crushed and screened for size. The grinding operation are carried out in an atmosphere of Nitrogen to prevent explosion from Acetylene Generated by moisture in the air. The approximate requirements per metric ton of Carbide are:

Lime – 991 kg, Coke – 683 kg, Electrode Paste – 17 to 20 kg, Electricity – 3200 kWh, and labor – 5 man hours.

The Carbide so produced is about 80% Calcium Carbide; 1 kg of Carbide yields about 0.29 cubic meter of Acetylene.

These are two standard methods for the production of Acetylene from Calcium Carbide and water: the wet process and the dry process. The wet process consists of adding the carbide to a relatively large quantity of water, releasing Acetylene gas while the calcium Hydrate residue is discharged in the form of a Lime slurry containing approximately 90% water.

In order to eliminate the waste of Calcium Hydrate, the dry process was originated in which a limited amount of water (1:1 by weight) is added to Calcium Carbide in a generator. The heat of reaction (1475 kcal/cubic meter) Acetylene generated) is employed to vaporized the excess water over the chemical equivalent, leaving a substantially dry Calcium Hydrate suitable for reuse as a Lime source. The temperature must be carefully controlled, since Acetylene Polymerized to from Benzene at 600 degree C and violently decomposes at 780 degree C, and Air mixtures may explode at 480 degree C. Generators of both types are usually designed to operate below 150 degree C and 15 psi (100 kPa).

The crude gas (containing traces of Hydrogen Sulfide, Ammonia, and Phosphine) from the generator is either scrubbed with water and Caustic Soda solution or Led to purifier where the impurities are absorbed by the use of Iron oxide or active Chlorine compounds. The dry gas is fed to cylinders to manufacturing units.

PROPERTIES

Colorless, Flammable gas, odorless when pure but ordinarily has a Garlic like order because of impurities.

Molecular Weight            : 26.04

Specific Gravity                 : 0.618, 20 degree C/4

Freezing Point                   : -80.8 degree C

Boiling Point                       : -84 degree C

Flash Point (open cup)   : Gas

Ignition Temperature     : 644 degree C

Vapor Density (air = 1)   : 0.91

Explosive Limits % by volume in air           : Lower 2.5 and Upper 82

Threshold Limit value in ppm      : 1000

One pound of Acetylene is equivalent to 14.5 cubic ft (1 kg = 0.9 cubic meter). Soluble in Acetone (2500 ml gas/100 g, 3000 ml gas/100 g at 12 atm), ethanol (600 ml/100 g), water (100 ml/100 g), and liquid a

Ammonia at room temperature.

Containers & Regulations – Steel pressure cylinder containing from 60 to 300 cubic ft of Acetylene (1.7 to 8.5 cubic meter). Mixtures of Air and acetylene, as well as liquid Acetylene are highly explosive. The cylinder must therefore contain a suitable solvent (such as Acetone) and generally a porous material (such as Asbestos, kapok, or diatomaceous earth) on which the solution is impregnated. The cylinder pressure must not exceed 250 psi (1.7 MPa) at 21 degree C, and requires a Red DOT shipping label.

ECONOMIC ASPECTS

Acetylene is produced on the post where needed by means of portable generators utilizing Calcium Carbide.

Economic Ascepts

Acetylene, Once used primarily in the metal industry for cutting and welding, is now used chiefly in the manufacture of chemicals. In this field economics problems of Acetylene manufacturer and use are of dual nature: whether to use Acetylene at all in a given process and, if so, whether to make it from Calcium Carbide or from Hydrocarbon gases.

The major chemicals presently manufactured, at last in part, from acetylene are Vinyl Chloride monomer, Vinyl Acetate, Acrylates, and tri and perchloroethylenes. Many of these can be made alternatively from ethylene and other petroleum hydrocarbons, so ultimate costs by the two routes becomes an important factor. Currently, ethylene is favored for vinyl acetate and chloride; propylene is preferred for the manufacture of Acrylates. Manufacturing routes to Acetaldehyde, Acetic acid, and Acrylonitrile, formerly held by acetylene, have been taken over by Ethylene and Propylene.

Increased use of Acetylene has developed through Rappe chemicals. Some of these are propargyl Alcohol, Butyrolactone, Vinyl pyrrolidone, Polyvinylpyrrolidone, 1,4 – butanediol, 2 – butyne – 1,4 – diol, and Tetrahydrofuran.