Tail gas cleanup

These redox processes are usually appHcable for small sulfur capacities. The sulfur is typically produced as a slurry, and can be upgraded to cake or molten sulfur. At low pressures, the redox processes can replace the amine Claus and tail gas cleanup processes with a single step, yet obtain sulfur recoveries of 99%. At higher pressures, the redox processes experience sulfur plugging and foaming problems. 

Tail gas cleanup is required because a well-designed Claus plant with three catalytic stages and fresh catalyst will recover only 95-97% of its feed sulfur (8), which is not generally sufficient to meet current emission standards. In addition, feed impurities and catalyst aging will reduce overall recovery in some plants to about 92% just before catalyst changeout. Therefore, tail-gas cleanup is required. Tail-gas treating processes are generally classified as follows ... 

Tail Gas Cleanup Process Efficiency - Required process efficiency depends on applicable emission regulations. Low-efficiency processes result in up to 99.0-99.5% overall sulfur recovery when combined with the Claus plant and include the Sulfreen, SNPA/Haldor-Topsoe, CBA, IFP, and Beavon Mark II processes. High-efficiency tail-gas treating processes can achieve overall sulfur recoveries of 99.8% and above under ideal conditions. These include the Beavon Mark I, SCOT, Trencor, and Wellman-Lord processes. 

Laengrich, A.R. and Cameron, W.L. "Tail-Gas Cleanup Addition May Solve Sulfur-Plant Compliance Problem," The Oil and Gas Journal, March 27, 1978. 

FIGURE 11.8 One ennission control system for nitric acid plant tail gas cleanup via catalytic reduction. 

Fate of impurities in feed gas has implications on emissions, tail-gas cleanup, and purity of the H2 product. 

GTI has envisioned a process (Figure 3) comprising the superadiabatic H2S decomposition reactor, product/byproduct separation schemes, hydrogen purification, and tail gas cleanup. Work has so far concentrated mainly on the superadiabatic reactor, and has comprised computational modeling and experimental studies to demonstrate the technical and economical feasibility of the superadiabatic H2S decomposition concept, using H2S-nitrogen (N2)-02 gas mixtures. 

UCARSOL HS Iff Sohrent vs. DIPA in Claus Tail Gas Cleanup Unit ... 

The hydrogenation step is an extension of the technology of the Beavon Sulfur Recovery (BSR) process used for Claus plant tail gas cleanup (see Chapter 8). However, because of the more dilute sulfur dioxide concentration in boiler plant flue gas and the presence of oxygen... 

Use of an aqueous methyldiethanolamine (MDEA) solution as a selective solvent (see Chapter 2) for hydrogen sulfide removal in tail gas cleanup has been described by Meissner (1983). With this solvent an overall conversion, including the Claus unit, of 99.9% of the H2S fed to the Claus unit is attainable. However, the treated gas contains some residual H2S, which may require incineration before discharge to the atmosphere. 

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