Wellman-Lord sulfur dioxide

The adaptability of this sulfur dioxide reduction technology to a feed gas containing 100% sulfur dioxide (dry basis) will be demonstrated at the D. H. Mitchell Station of the Northern Indiana Public Service Co. (NIPSCO) at Gary, Indiana (8). In this application the process will be combined with the Wellman-Lord sulfur dioxide recovery process to provide a complete flue gas desulfurization system for a 115-MW coal-fired boiler in a project jointly funded by NIPSCO and the Environmental Protection Agency. 

Recent Experience of the Wellman-Lord Sulfur Dioxide Recovery Process... 

Figure I. Basic flow diagram of the Wellman-Lord sulfur dioxide recovery...

At Chiba, Japan, the Japan Synthetic Rubber Co. has two steam boilers with evaporation rates of 130 metric tons/hr, each equipped with Wellman-Lord sulfur dioxide recovery units. The load to each scrubber is essentially constant, but sulfur dioxide concentration varies from 400 to 2,000 ppm because of the varying quantities of waste process gas from the plant. 

The Wellman-Lord process can be a significant factor in helping domestic power plants to meet the air pollution abatement requirements of the Clean Air Act of 1970. To show its applicability to the utilities industry, Davy Powergas Inc. is building a demonstration installation at the Dean H. Mitchell Station of Northern Indiana Public Service Co. in Gary, Ind. When completed, it will consist of a Wellman—Lord sulfur dioxide recovery unit connected to an Allied Chemical Co. sulfur dioxide-to-sulfur reduction process to produce elemental sulfur. Davy Powergas guarantees emissions of 200 ppm by volume or less of sulfur dioxide at this facility. 

Regenerable absorption processes have also been developed. In these processes, the solvent releases the sulfur dioxide in a regenerator and then is reused in the absorber. The WelLman-Lord process is typical of a regenerable process. Figure 11 illustrates the process flow scheme. Sulfur dioxide removal efficiency is from 95—98%. The gas is prescmbbed with water, then contacts a sodium sulfite solution in an absorber. The sulfur dioxide is absorbed into solution by the following reaction ... 

Wellman-Lord The most widely used regenerable flue-gas desulfurization process. The sulfur dioxide is absorbed in sodium sulfite solution in a wet spray scrubber, forming sodium bisulfite ... 

In the Wellman-Lord process, sodium sulfite is used to capture the sulfur dioxide. The sodium bisulfite thus formed is later heated to evolve sulfur dioxide and regenerate the sulfite scrubbing material. The sulfur dioxide-rich product stream can be compressed or liquefied and oxidized to sulfuric acid, or reduced to sulfur. 

With the double contact process it is unnecessary to purify the tail gases to reduce their sulfur dioxide content still further, whereas tail gases from single contact plants have to be purified. This can be realized either by scrubbing with ammonia or with an aqueous solution of sodium sulfite and sodium hydrogen sulfite (Wellman-Lord process), absorption on activated charcoal (sulfacid process from Lurgi) or by oxidative gas purification such as in the peracidox process (oxidation of sulfur dioxide with hydrogen peroxide or peroxomonosulfuric acid). 

The Wellman-Lord process uses the effective sodium sulfite-sodium bisulfite equilibrium to capture sulfur dioxide from flue gases [40] (Eqs. 3.26 and 3.27). 

The third class of control systems may use any of the sulfur dioxide control systems among those used commercially are the Haldor Topsoe (5, 80), Wellman-Lord (27, 07), and Chiyoda (27, 07, 87) systems. The circumstances are generally highly favorable for recovery processes that produce a stream of concentrated sulfur dioxide, since this can be recycled to the Claus plant. The application of processes that produce sulfuric acid or solid wastes will be dictated only by peculiar local circumstances. 

The first commercial application of the Wellman-Lord process was at the Olin Corp. sulfuric acid regeneration plant in Paulsboro, N. J. This plant regenerates 700 tons of sulfuric acid/day and handles a variety of spent acids. The sulfur dioxide content of the tail gas varies as the blends of these acids change. 

The El Segundo installation immediately lowered the emissions from the SOCAL refinery Claus plants to within the Los Angeles area limits of 500 ppm or less of sulfur dioxide. At Richmond, regulations are even lower—300 ppm or less. The Wellman-Lord recovery units being installed there are guaranteed by Davy Powergas to meet those emission levels. 

Processes that have been successful in other industrial applications presently are being studied for inclusion in the Wellman-Lord process. This would allow the system to operate as a closed loop with total sodium and sulfur dioxide recovery and would eliminate eflluent streams requiring treatment. Further test work is necessary, however, before including another idea into the commercially proved process. 

Sulfur dioxide Wellman-Lord Sodium sulfite... 

I en percent of the regenerator offgas is purified in a Wellman-Lord unit, and the concentrated sulfur dioxide from this unit is added to the remaining 90% of the gas which is then processed in a BSRP system. The Wellman-Lord process is described in Chapter 7. The BSRP system consists of a Beavon Sulfur Removal (BSR) unit to convert all sulfur compounds to hydrogen sulfide (see Chapter 8) followed by a Stretford unit to convert the hydrogen sulHde to elemental sulfur (see Chapter 9). 

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