Catalytic scrubbing

Catalytic Scrubbing Selective Catalytic Reduction 70%e 0.017d,e to 0.044 14d,e to 36... 

Can be combined with other technologies, such as catalytic scrubbing or partial burn regenerators, to achieve greater NO reduction. 

An alternate approach to catalytic scrubbing is the injection of ozone, chlorine, or hydrogen peroxide into the flue gas upstream of the scrubber. Ozone is the more powerful oxidizing agent, with chlorine just behind. Hydrogen peroxide is not always practical because of the long reaction times required. 

Ultimately, pollution can only be avoided by complete removal of SO2 from the effluent gases, but this council of perfection is both technologically and economically unattainable. Many processes are available to reduce the SO2 concentration to very low figures, but the vast scale of power generation and domestic heating by coal and oil still results in substantial emission. SO2 can be removed by scrubbing with a slurry of milk of lime , CafOH) . Alternatively, partial reduction to H2S using natural gas (CH4), naphtlia or coal, followed by catalytic conversion to elemental sulfur by the Claus process can be used ... 

Geminox A direct process for converting butane to 1,4-butanediol. The butane is first oxidized in the gas phase to maleic anhydride, using BP s fluidized bed technology. The maleic anhydride is scrubbed with water and then catalytically dehydrogenated to butanediol. Developed in 1994 by BP Chemicals and Lurgi. Modifications of the process can be used to make tetrahydrofiuan and y-butyrolactone. The first plant will probably be built on BP s site at Lima, OH, for completion in 2000. 

North Thames Gas Board A process for removing organic sulfur compounds from coal gas by catalytic oxidation over nickel sulfide at 380°C. The sulfur dioxide produced is removed by scrubbing with dilute aqueous sodium hydroxide. Operated by the gasworks of the North Thames Gas Board, London, between 1937 and 1953. 

SOLINOX SO,. Linde NO,] A process for removing both NOx and SOx from fluegases. The SOx is removed by scrubbing with tetra-ethylene glycol dimethyl ether, circulated in a packed tower (the Selexol process). The NOx is destroyed by Selective Catalytic Reduction ( SCR). The sorbent is regenerated with steam the SOx is recovered for conversion to sulfuric acid. Developed by Linde in 1985 and used in a lead smelter in Austria and several power stations in Germany. In 1990 it was announced that it would be used at the titanium pigment plant in The Netherlands operated by Sachtleben. 

Fig. 26.7 Catalytic hypochlorite decomposition integrated into the scrubbing process.

For continuous processes the catalytic reactor, or a hybrid process if satisfactory chemical dosing equipment is already installed, appear to be a near-optimum solution still for many installations. At moderate hypochlorite concentrations, economic benefit does accrue from using the catalyst in-loop rather than end-of-pipe, but these benefits may be offset by any required investment in heat-exchange capability. At concentrations above 10 wt% the integration of decomposition into the scrubbing process is beneficial to the overall cost base of hypochlorite treatment. 

The background for the development of VK69 was a need for reduction of S02 emissions from double-absorption plants by installing a more active catalyst at low temperature downstream from the intermediate absorption tower. Clearly, the catalytic solution should be more competitive than the alternatives, e.g. tail gas scrubbing or triple-absorption layout, in terms of capital and operating costs. In the following, the required technical performance of the catalyst with respect to S02 oxidation activity, mechanical strength and pressure drop is discussed, and input from the literature and from practical experience in the field is presented. Reviews of the extensive literature published on sulphuric acid catalysts can be found in [2-5],... 

Other applications of microparticles include spray drying, stack gas scrubbing, particle and droplet combustion, catalytic conversion of gases, fog formation, and nucleation. The removal of SO2 formed in the combustion of high-sulfur coal can be accomplished by adding limestone to coal in a fluidized bed combustor. The formation of CaO leads to the reaction... 

In the gasifiers the sulphur present in the coal is converted to H S which is scrubbed out, together with the C0 in the downstre Rectisol unit. The effluent stream from this unit (typically 1.5 % HpS in CO2) is treated in a homogeneous catalytic process in which tne H S is converted to high grade elemental sulphur. The catalytic liquor consists essentially of an alkaline vanadium solution. In the... 

VOCs and inorganic compounds, membrane separation, condensation, adsorption, wet scrubbing, biofiltration, bioscrubbing, biotrickling, thermal oxidation, catalytic oxidation, and flaring. 

Oxides of nitrogen, NO, can also form. These are generally at low levels and too low an oxidation state to consider water scrubbing. A basic reagent picks up the N02, but not the lower oxidation states the principal oxide is usually NO, not N02. Generally, control of NO, is achieved by control of the combustion process to minimize NO ie, avoidance of high temperatures in combination with high oxidant concentrations, and if abatement is required, various approaches specific to NO have been employed. Examples are NH3 injection and catalytic abatement (43). 

From the chemical manufacturing industry, catalytic cracking and catalytic hydrogenation, gas absorption or scrubbing processes in which desired or waste products are removed from a waste stream, the nitration of benzene and toluene where the reactants have limited mutual solubility, and carbonylation processes using carbon monoxide. 

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