Power stations, cleaning processes

For clean gaseous effluents, such as those from nitric acid plants, the preferred catalyst is mordenite. For flue-gases containing fly ash, the preferred catalyst is titania-vanadia. The process was developed in Japan in the mid-1970s by a consortium of Hitachi, Babcock-Hitachi, and the Mitsubishi Chemical Company, and by the Sakai Chemical Industry Company. It is widely used in power stations in Japan and Germany. See also SNCR. 

Liquid waste is generated in numerous places with activities <0.1 GBq/ m. Such waste is classified as low level. Some of these liquids may be clean enough to be released directly into the environment. Others are cleaned by flocculation, ion exchange, sorption, and similar processes. The general philosophy for liquid wastes is to concentrate all radioactivity to the next higher level because the waste volumes decrease in the order LLLW > MLLW > HLLW. Thus, in principle, the three kinds of wastes are reduced to two (HLLW and MLLW) and cleaned aqueous effluent. The MLLW and residues from LLLW cleaning are treated as the wastes of the nuclear power stations, i.e. concentrated and put into a disposal matrix such as concrete or bitumen (see 20.4.3). At some coastal sites it has been the practice to release the LLLW to the sea, with official permission. The nuclides of main concern are H, °Sr, Cs, Ru, and the actinides. 

Such membranes have been applied in the separation of heavy metals from acids and highly alkaline solutions, and in the recovery of alkaline solutions used in cleaning processes. Desal nanofiltration membranes commercialized by GE Osmonics can also work at very low pH levels. They have been used to recover heavy metals and clarify 35% sulfuric acid feed streams or 25% phosphoric acid streams. They have also been applied to permeate boric acid and reject radionuclides at a nuclear power station. Somicon/Nitto Denko announces nanofiltration membranes (NTR-7410, 7430 and 7450 HG) for pH range 1-12, temperatures up to 90 °C and a maximum pressure of 50 bar [37]. 

There are a number of processes that are being used in coal-fired power stations that improve the efficiency and environmental acceptability of coal extraction, preparation and use, and many more are under development (Bris et al., 2007). These processes are collectively known as clean coal technologies. Designation of a technology as a clean coal technology does not imply that it reduces emissions to zero or near zero. For this reason, the term has been criticized as being... 

Any continuing use of fossil fuels should use clean and efficient technology. Power-stations generating electricity from coal and oil (fossil fuel) release a lot of CO2 in the generating process. New-build power-stations must now be fitted with carbon capture filters to reduce the bad environmental effects. 

An example of post-CMP clean process sequence design for defect reduction is the hybrid clean process as illustrated in Figure 17.25. In this approach, an acidic chemical is used in the roller bmsh steps in sequence to dissolve the metal oxide PR/FM while an alkaline clean chemical is plumbed to the megasonic tank without power to clean off the remaining PR/FM and passivate the Cu surface. In other words, the megasonic clean station is adopted only as a rinse tank with an alkaline chemical solution. The use of acidic clean chemical solution in the bmshes to dissolve metal oxide is the key to the reduction of PR/FM and the ehmination of circular ring defects. The application of a basic chemical rinse step provides further reduction in surface defects and passivation of the Cu surface to prevent the formation of HM and DE defects. 

Flue gas desulphurization (FGD) gypsum is a waste generated at coal burning power stations where FGD clean coal combustion and scrubbing processes are installed to remove SO2 from the flue gases. In this chapter, the possibility of FGD gypsum as an admixture in cement-based materials, such as Portland cement, concrete, and geopolymer was explored. 

Furken, H., 1970, The Reinluft (Clean Air) Process for the Purification of Flue Gas from Power Stations, Proceedings of the American Power Conference, Vol. 32, No. 673. 

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. 

There might be additional chemical or technical restrictions that have to be taken into account for pipeline transport planning such as the interruptibility of pipeline operation. E.g. if a product remains too long in a pipeline without movement, chemical reactions may take place which may cause corrosion or polymerization processes. This would lead to a failure and cause expensive maintenance and/or cleaning operations. However, the most obvious technical restriction is probably the pump rate of a pipeline. The pump rate measures the transport speed on a volume-per-time basis. Typically, there is an upper bound for the tolerable pressure inside a pipeline determining the maximum pump rate (say p ). The realized pump rate might be smaller and depends on the power of pumps at the pumping stations. ... 

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