Sulfur burning plant types

In drying towers of sulfur-burning plants, mesh pads or inertial impaction-type mist eliminators are usually adequate. High efficiency mist eliminators are usually used in drying towers of spent acid or metallurgical plants. 

Commercial sulfur is usually 99,9% or higher in purity. Dark" sulfur contains hydrocarbon impurities up to about 0,5% bright sulfur contains less than about 0.1% (measured as carbon). Dark sulfur causes difficulties in some types of sulfur-burning plants. However, methods for uar dark sulfur without difficulty have been developed. Another quality factor is the ash content, riiich should be quite low to avoid dust that will accumulate in the catalyst bed. Solid impurities can be removed from mdten sulfur by filtration 41. Alternatively, by using a hot gas filter, dust arising from ash in the sulfur can be removed from the hot gas leaving the sulfur burner. 

The investment costs in this chapter focus on sulfur burning and metallurgical type acid plants. Costs for spent acid regeneration acid plants are expected to be slightly higher than sulfur burning acid plants due to their increased furnace complexity and additional gas cleaning equipment. 

Figure 31.2 Expected total investment costs for sulfur burning acid plants based on their capacity. The costs are representative of a modem 3 1 double contact type sulfur burning acid plant constructed mostly of stainless steel. A steam turbine generator is included in the costs along with the associated infrastructure required to support the operation.

This chapter has provided study estimate level investment and production cost estimates for sulfur burning and metallurgical type sulfuric acid plants. Spent acid regeneration type acid plants are expected to have slightly higher investment costs than sulfur burning type acid plants. 

The capital investment for any FBC plant depends upon several factors, including the cost of capital, size of unit, geographic location, and coal type. EPRI has completed several economic evaluations and projects the following costs, in 1994 US dollars, for plants located in Kenosha, Wisconsin, burning Illinois No. 6 bituminous coal contain-ing 4 percent sulfur 200-MWe circulating AFBC, 1520/kW 350-MWe bubbling PFBC, 1220/kW 350-MWe circulating PFBC, 1040/kW 320-MWe advanced PFBC, 1110/kW. The advanced PFBC has the most potential for cost reduction, and capital investment could be reduced to below 1000/kW. 

The quality of the oil burned by electric utilities in 1969, compared plant-by-plant and state-by-state with the preliminary state implementation programs, shows that 59 million bbl of oil burned in about 310 units could meet the standards and that 199 million bbl of oil burned in 735 units would require some type of control measures to meet the proposed sulfur limitations. 

The major source of sulfur oxides in the atmosphere is the burning of sulfur-containing coal in power plants. As this type of coal burns in a furnace, sulfur dioxide gas, SO2, is produced. The SO2 escapes into the atmosphere, where it reacts with more oxygen to form sulfur trioxide, SO3. 

As usual in the conventional copper or lead smelter, none of the El Paso smelter gas streams has a sulfur dioxide concentration as high as 12%. In the pilot plant, then, the 12% sulfur dioxide gas stream is generated by burning molten sulfur in a spray-type sulfur burner to produce a gas stream containing 18% sulfur dioxide. This hot gas stream, at 1350°C (1623 K), is cooled to about 360°C (633 K) in a waste heat boiler. When the pilot plant is operating with this 18% gas, process tail gases are recycled to dilute the 18% head gas stream to 12%. In an alternate mode of operation, liquid sulfur dioxide is vaporized to generate the pure gas. 

The sulfide-rich gas is then processed for sulfur as indicated in Fig. 20-19 which is a somewhat package-type plant.In the presence of bauxite (and many surface active materials) hydrogen sulfide burns directly to sulfur and water. However, this reaction is so highly exothermic that sulfur is usually produced in two steps as follows ... 

Man-made sources The burning of coal and oil accounted for virtually all the sulfur oxides emitted from man-made sources in the eastern U.S., about 30.6 million tonnes (calculated as sulfate) in 1980. (Table 2). (Emissions are estimated from the sulfur content of each type of fuel and the amount of fuel consumed.) Electric utilities contributed 71% of the total SO2, with the majority of emissions coming from coal-fired power plants. The remainder came chiefly from industrial, commercial and residential combustion transportation smelters and industrial processes. An additional 2.1 million tonnes entered the U.S. from Canada, principally emissions from metal smelters,- and 1.2 million tonnes entered the region from the western U.S. ... 

Trace element analysis Trace element analysis is an indirect technique that seeks to infer the sources of sulfur pollution by measuring other chemical elements emitted along with the sulfur. The technique is based on the fact that different pollution sources emit characteristic chemical "signatures" (characteristic amounts and types of chemical elements) that depend on the type of fuel burned. For example, the pollution from coal-fired plants is relatively high in selenium, an element chemically similar to sulfur pollution from oil-fired plants is relatively low in selenium. By measuring the levels of such elements in polluted air, it is in principle possible to infer whether the pollution came predominantly from coal-fired sources (and therefore predominantly from the Midwest) or from oil-fired sources (and therefore chiefly from the Northeast). (A similar technique has been used to trace oil spills, based on the fact that the oil in each ship s hold is a chemically unique mixture). 

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