Sulfur continued methods

Other Techniques Continuous methods for monitoring sulfur dioxide include electrochemical cells and infrared techniques. Sulfur trioxide can be measured by FTIR techniques. The main components of the reduced-sulfur compounds emitted, for example, from the pulp and paper industry, are hydrogen sulfide, methyl mercaptane, dimethyl sulfide and dimethyl disulfide. These can be determined separately using FTIR and gas chromatographic techniques. 

Tetryl. In the manufacture of Tetryl, it is usual not to nitrate dime thy laniline directly, but to dissolve it first in coned sulfuric acid and then to nitrate the dimethylaniline sulfate so obtained. Direct nitration of dimethylaniline proceeds so violently that it can be carried out only under specialized conditions. Many years experience of Tetryl manufacture has shown that the ratio of sulfuric acid to dimethylaniline should not be lower than 3 1, since a smaller amount of sulfuric acid may be detrimental to the nitration process. However, the ratio of sulfuric acid to dimethylaniline must not be too high, otherwise Tetryl yield is decreased. Temp must be maintained between 20-45° to avoid sulfonation of the benzene ring. Care must be exercised not to leave any unreacted dimethylaniline prior to introduction of nitric acid, because of the potential violence of the dimethyl-aniline-nitric acid reaction. Consequently, continuous methods of prepn are to be preferred as they inherently minimize accumulation of unreacted dimethylaniline... 

Continuous methods using the same installations as for manuf of NG are used now in Europe. Two of these installations, Schmid-Meissner and Biazzi, are described in Vol 3 of Encyci, pp C502—C504. We also know that continuous method of Schmid-Meissner is installed in Argentina at the Naval Explosives Plant. The same plant employs Bofors Continuous Method for manuf of TNT. Accdg to Ref 24, nearly 100% conversion of Gc to NGc is achieved by mixed acid nitration in liquid sulfur dioxide... 

The steady-state permeability results obtained for the 1000 pm thick 80, 60 and 53wt% alloys under flowing 1000 ppm H2S/H2 were compared to the transient 1000 ppm H2S/H2 permeability reported previously. Nearly identical trends in permeability were found for these three alloys using these two measurement methods. This agreement reinforces the suggested correlation between the alloy crystal structure and H2S tolerance. The results of these steady-state permeability experiments indicated that when the Pd-Cu alloys had an fee structure, H2S had little impact on permeability but when die structure was bcc, H2S had a moderate to severe impact However, because of the extreme 1000 pm thickness of the membranes used in this test series which could potentially mask effects arising from sulfur interactions, methods were sought to enable continuous H2S exposure of 100 pm and thinner membranes. 

Under optimum conditions, the reaction time for this process has been calculated at 1.5 hr at 180 C, using a seven-stage reactor and employing 10 moles of benzene per mole of sulfuric acid. In contrast, the same process operated in batches (see pp. 311 and 371) at 160-180°C ould require 14 hr and 6-8 moles of benzene per mole reacted. Thus, the continuous method increases by nearly ten times the capacity of the batch method. It is further estimated that the ratio of benzene used to benzene reacted could be reduced as low as 3 1 by doubling the time of reaction. The efficiency of the process can be further increased by using 10 per cent oleum instead of sulfuric acid, thereby reducing the required water removal without substantially raising by-prosulfone formation. This type of process has been used commercially in the United States. ... 

The prime Ordn use for sulfuric acid is in the mixed nitiic-sulfiiric acid used in the mixed add nitration of raw materials to form expls and proplnts. The techniques and procedures are presented in Vol 2, ClOl-R to C103-L under Preparation of NC s in Vol 3, C501-L to C510-L under Continuous Methods for Manufacturing Explosives in Vol 6, G98-R to G103-R. under Glycerol Trinitrate or Nitroglycerin (NG) and in Vol 8, N40-R to N88-R under Nitration ... 

Automated analyzers may be used for continuous monitoring of ambient poUutants and EPA has developed continuous procedures (23) as alternatives to the referenced methods. Eor source sampling, EPA has specified extractive sampling trains and analytical methods for poUutants such as SO2 and SO [7446-11-9] sulfuric acid [7664-93-9] mists, NO, mercury [7439-97-6], beryUium [7440-41-7], vinyl chloride, and VOCs (volatile organic compounds). Some EPA New Source Performance Standards requite continuous monitors on specified sources. 

Nickel sulfate also is made by the reaction of black nickel oxide and hot dilute sulfuric acid, or of dilute sulfuric acid and nickel carbonate. The reaction of nickel oxide and sulfuric acid has been studied and a reaction induction temperature of 49°C deterrnined (39). High purity nickel sulfate is made from the reaction of nickel carbonyl, sulfur dioxide, and oxygen in the gas phase at 100°C (40). Another method for the continuous manufacture of nickel sulfate is the gas-phase reaction of nickel carbonyl and nitric acid, recovering the soHd product in sulfuric acid, and continuously removing the soHd nickel sulfate from the acid mixture (41). In this last method, nickel carbonyl and sulfuric acid are fed into a closed-loop reactor. Nickel sulfate and carbon monoxide are produced the CO is thus recycled to form nickel carbonyl. 

Sulfamic acid [5329-14-6] (amidosulfuric acid), HSO2NH2, molecular weight 97.09, is a monobasic, inorganic, dry acid and the monoamide of sulfuric acid. Sulfamic acid is produced and sold in the form of water-soluble crystals. This acid was known and prepared in laboratories for nearly a hundred years before it became a commercially available product. The first preparation of this acid occurred around 1836 (1). Later work resulted in identification and preparation of sulfamic acid in its pure form (2). In 1936, a practical process which became the basis for commercial preparation was developed (3,4). This process, involving the reaction of urea with sulfur trioxide and sulfuric acid, continues to be the main method for production of sulfamic acid. 

Agriculture is the largest industry for sulfur consumption. Historically, the production of phosphate fertilizers has driven the sulfur market. Phosphate fertilizers account for approximately 60% of the sulfur consumed globally. Thus, although sulfur is an important plant nutrient in itself, its greatest use in the fertilizer industry is as sulfuric acid, which is needed to break down the chemical and physical stmcture of phosphate rock to make the phosphate content more available to plant life. Other mineral acids, as well as high temperatures, also have the abiUty to achieve this result. Because of market price and availabiUty, sulfuric acid is the most economic method. About 90% of sulfur used in the fertilizer industry is for the production of phosphate fertilizers. Based on this technology, the phosphate fertilizer industry is expected to continue to depend on sulfur and sulfuric acid as a raw material. 

The Reich test is used to estimate sulfur dioxide content of a gas by measuring the volume of gas required to decolorize a standard iodine solution (274). Equipment has been developed commercially for continuous monitoring of stack gas by measuring the near-ultraviolet absorption bands of sulfur dioxide (275—277). The deterrnination of sulfur dioxide in food is conducted by distilling the sulfur dioxide from the acidulated sample into a solution of hydrogen peroxide, foUowed by acidimetric titration of the sulfuric acid thus produced (278). Analytical methods for sulfur dioxide have been reviewed (279). 

Continuous dyeing of piece goods by pad—steam methods is one of the principal outiets for sulfur dyes, mostiy in prereduced Hquid form. 

Sulfur can be produced direcdy via Frasch mining or conventional mining methods, or it can be recovered as a by-product from sulfur removal and recovery processes. Production of recovered sulfur has become more significant as increasingly sour feedstocks are utilized and environmental regulations concerning emissions and waste streams have continued to tighten worldwide. Whereas recovered sulfur represented only 5% of the total sulfur production ia 1950, as of 1996 recovered sulfur represented approximately two-thirds of total sulfur production (1). Recovered sulfur could completely replace native sulfur production ia the twenty-first century (2). 

The earliest method for manufacturiag carbon disulfide involved synthesis from the elements by reaction of sulfur and carbon as hardwood charcoal in externally heated retorts. Safety concerns, short Hves of the retorts, and low production capacities led to the development of an electric furnace process, also based on reaction of sulfur and charcoal. The commercial use of hydrocarbons as the source of carbon was developed in the 1950s, and it was still the predominate process worldwide in 1991. That route, using methane and sulfur as the feedstock, provides high capacity in an economical, continuous unit. Retort and electric furnace processes are stiU used in locations where methane is unavailable or where small plants are economically viable, for example in certain parts of Africa, China, India, Russia, Eastern Europe, South America, and the Middle East. Other technologies for synthesis of carbon disulfide have been advocated, but none has reached commercial significance. 

Carbon Disulfide Chlorination. The chlorination of carbon disulfide [75-15-0] is a very old method of producing carbon tetrachloride that is still practiced commercially in the United States. In this process CS2 reacts continuously with chlorine in an annular reactor at 105—130°C. Product CCl is separated by distillation to a CS2 content of 0—5 ppm. By-product S2CI2 is reduced in a reactor at 450°C with hydrogen without a catalyst to give sulfur of 99.985% purity (32). Other processes use ferric chloride as a catalyst (33,34). 

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