Sulfur compressive

Large underground deposits are the principal source of elemental sulfur. The Frasch process, illustrated in Figure 22.23 A, is used to obtain the element from these deposits. The method is based on the low melting point and low density of sulfur. Superheated water is forced into the deposit, where it melts the sulfur. Compressed air then forces the molten sulfur up a pipe to the surface above, where the sulfur cools and solidifies. 

By-product water formed in the methanation reactions is condensed by either refrigeration or compression and cooling. The remaining product gas, principally methane, is compressed to desired pipeline pressures of 3.4—6.9 MPa (500—1000 psi). Einal traces of water are absorbed on siHca gel or molecular sieves, or removed by a drying agent such as sulfuric acid, H2SO4. Other desiccants maybe used, such as activated alumina, diethylene glycol, or concentrated solutions of calcium chloride (see Desiccants). 

Several types of fluids are used as refrigerants in mechanical compression systems ammonia, halocarbon compounds, hydrocarbons, carbon dioxide, sulfur dioxide, and cryogenic fluids. A wide temperature range therefore is afforded. These fluids boil and condense isotherm ally. The optimum temperature or pressure at which each can be used can be deterrnined from the economics of the system. The optimum refrigerant can be deterrnined only... 

Sulfur and Chlorine Pipelines. Underground sulfur is melted by superheated water and then piped as Hquid to the surface with compressed air. At the surface, molten sulfur is transported by heated pipeline to a storage or shipping terminal. One such pipeline, located under 15 m of water in the Gulf of Mexico, is insulated and surrounded by steel casing to which are strapped two 130-mm dia pipelines that carry return water from the deposit. The superheated water is carried from shore to the deposit in a 63.5-mm dia pipe inside the pipeline that carries the molten sulfur (21). 

Eig. 1. The Erasch process (a) initial heating (b) movement of Hquid sulfur and (c) result of pumping compressed air. The thinner arrows indicate the... 

Chemica.1 Properties. Reviews of carbonyl sulfide chemistry are available (18,23,24). Carbonyl sulfide is a stable compound and can be stored under pressure ia steel cylinders as compressed gas ia equiUbrium with Hquid. At ca 600°C carbonyl sulfide disproportionates to carbon dioxide and carbon disulfide at ca 900°C it dissociates to carbon monoxide and sulfur. It bums with a blue flame to carbon dioxide and sulfur dioxide. Carbonyl sulfide reacts... 

Production and Economic Aspects. Thallium is obtained commercially as a by-product in the roasting of zinc, copper, and lead ores. The thallium is collected in the flue dust in the form of oxide or sulfate with other by-product metals, eg, cadmium, indium, germanium, selenium, and tellurium. The thallium content of the flue dust is low and further enrichment steps are required. If the thallium compounds present are soluble, ie, as oxides or sulfates, direct leaching with water or dilute acid separates them from the other insoluble metals. Otherwise, the thallium compound is solubilized with oxidizing roasts, by sulfatization, or by treatment with alkaU. The thallium precipitates from these solutions as thaUium(I) chloride [7791 -12-0]. Electrolysis of the thaUium(I) sulfate [7446-18-6] solution affords thallium metal in high purity (5,6). The sulfate solution must be acidified with sulfuric acid to avoid cathodic separation of zinc and anodic deposition of thaUium(III) oxide [1314-32-5]. The metal deposited on the cathode is removed, kneaded into lumps, and dried. It is then compressed into blocks, melted under hydrogen, and cast into sticks. 

The largest use for calcium carbide is in the production of acetylene for oxyacetylene welding and cutting. Companies producing compressed acetylene gas are located neat user plants to minimize freight costs on the gas cylinders. Some acetylene from carbide continues to compete with acetylene from petrochemical sources on a small scale. In Canada and other countries the production of calcium cyanamide from calcium carbide continues. More recentiy calcium carbide has found increased use as a desulfurizing reagent of blast-furnace metal for the production of steel and low sulfur nodular cast iron. 

The Inco flash smelting process produces a very high strength sulfur dioxide gas by using pure oxygen for smelting. Liquid sulfur dioxide is obtained upon compression. 

The crystalliza tion resistance of vulcaniza tes can be measured by following hardness or compression set at low temperature over a period of time. The stress in a compression set test accelerates crystallization. Often the curve of compression set with time has an S shape, exhibiting a period of nucleation followed by rapid crystallization (Fig. 3). The mercaptan modified homopolymer, Du Pont Type W, is the fastest crystallizing, a sulfur modified homopolymer, GN, somewhat slower, and a sulfur modified low 2,3-dichlorobutadiene copolymer, GRT, and a mercaptan modified high dichlorobutadiene copolymer, WRT, are the slowest. The test is often mn near the temperature of maximum crystallization rate of —12° C (99). Crystallization is accelerated by polyester plasticizers and delayed with hydrocarbon oil plasticizers. Blending with hydrocarbon diene mbbers may retard crystallization and improve low temperature britdeness (100). 

Both Watts and sulfamate baths are used for engineering appHcation. The principal difference in the deposits is in the much lower internal stress obtained, without additives, from the sulfamate solution. Tensile stress can be reduced through zero to a high compressive stress with the addition of proprietary sulfur-bearing organic chemicals which may also contain saccharin or the sodium salt of naphthalene-1,3,6-trisulfonic acid. These materials can be very effective in small amounts, and difficult to remove if overadded, eg, about 100 mg/L of saccharin reduced stress of a Watts bath from 240 MPa (34,800 psi) tensile to about 10 MPa (1450 psi) compressive. Internal stress value vary with many factors (22,71) and numbers should only be compared when derived under the same conditions. 

Na or Li and ammonia, excellent yields. " A dissolving metal reduction can be effected without cleavage of a sulfur-carbon bond. Note also the unusual selectivity in the cleavage illustrated below. This was attributed to steric compression. ... 

In a typical gas oil design, the lighter products overhead from the quench tower/primary fractionator are compressed to 210 psi, and cooled to about 100°F. Some Q plus material is recovered from the compressor knockout drums. The gases are ethanolamine and caustic washed to remove acid gases sulfur compounds and carbon dioxide, and then desiccant dried to remove last traces of water. This is to prevent ice and hydrate formation in the low temperamre section downstream. 

Many suppliers of sulfuric acid recommend that it is stored in pressure vessels designed to withstand a gauge pressure of 30 psi (2 bar). The acid is usually discharged from tank trucks by compressed air, and if the vent is ehoked the vessel could be subjected to the full pressure of the compressed air. 

Sulfur Dioxide, Paniplilet G-3, 3 ed.. Compressed Gas Association, New York, 1964. 

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