Byproduct hydrogen

At present about 77% of the industrial hydrogen produced is from petrochemicals, 18% from coal, 4% by electrolysis of aqueous solutions and at most 1% from other sources. Thus, hydrogen is produced as a byproduct of the brine electrolysis process for the manufacture of chlorine and sodium hydroxide (p. 798). The ratio of H2 Cl2 NaOH is, of course, fixed by stoichiometry and this is an economic determinant since bulk transport of the byproduct hydrogen is expensive. To illustrate the scde of the problem the total world chlorine production capacity is about 38 million tonnes per year which corresponds to 105000 toimes of hydrogen (1.3 x I0 m ). Plants designed specifically for the electrolytic manufacture of hydrogen as the main product, use steel cells and aqueous potassium hydroxide as electrolyte. The cells may be operated at atmospheric pressure (Knowles cells) or at 30 atm (Lonza cells). 

Hydrogen could be a peaceful energy carrier for all countries. Hydrogen might be the next great fuel, as it is available worldwide and water is its only byproduct. Hydrogen has received increased attention as a renewable and environmentally friendly option to help meet today s energy needs. 

Byproduct Hydrogen. Large volumes of byproduct hydrogen are generated from a variety of production processes. Some of these processes are listed in Reference 40. Some of the processes that can be used to obtain purified hydrogen are summarized below. 

Kvaemer Oil Gas, Norway, has introduced a process for manufacturing carbon black that generates substantial quantities of byproduct hydrogen. In 1998 the process was installed in Montreal, Quebec (Canada) to produce 20,000 tonnes of carbon black and 50 million Nm3 per year (5.2 million standard cubic feet per day) of hydrogen. The process appears to be economic only when the carbon black can also be sold as an end product.40... 

Kvaerner Process Technology Ethyl acetate Ethanol Ethanol only process—no acetic acid required byproduct hydrogen can be used as feedstock or fuel 1 1998... 

Carolac Carolina Byproducts Hydrogenated tallow—prilled 98... 

The fuel oil is burned to provide flue gases for heating the reactor feed and the reactor. Some of the fuel requirements could be provided by using the byproduct hydrogen. Also, the exhaust flue gases could be used to generate steam. The economics of these possibilities need not be considered. 

Crude oil usually contains between 0.1% and 2.8% sulfur. A few individual crudes contain over 3% S 171]. Sulfur is largely removed during oil processing, resulting in substantial quantities of byproduct hydrogen sulfide and mercaptans. 

The byproduct hydrogen chloride is absorbed in water to give hydrochloric acid, which can be electrochemicalfy decomposed to give chlorine gas—to be recycled into the phosgene production — and hydrogen gas, which is used in the hydrogenation... 

Residual adsorbed byproduct hydrogen chloride is removed by high temperature steam calcination. The resultant silica has a hydrophilic surface with 2.5 to 3.5 hydroxyls (OH)/nm. Hydrophobic grades are produced by treating hydrophilic grades with hexamethyldisilazane, dimethyldichlorosilane, or with silicone fluids... 

Electrolysis. In some areas hydrogen is obtained by electrolysis, but normally this is not economical. Electric power must be available at a very low cost such as that from hydroelectric power. In some cases, byproduct hydrogen from the electrolysis of brine has been used to manufacture ammonia. 

The demand for larger vinyl chloride plants coincided with the development of hydrocarbon steam crackers. Ethylene reacts directly with chlorine forming ethylene dichloride, which was decomposed thermally to produce vinyl chloride. The byproduct hydrogen chloride could then be used to produce more viityl chloride as a feedstock for the acetylene process. This was described as the balanced ethylene-acetylene process ... 

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