Flue gas desulphurisation plants

Ferritic, austenitic, or ferritic-austenitic cast alloys are used in preference as materials for pumps in scrubber circuits of flue gas desulphurisation plants (FGD... 

Table 9 Essential parameters of scrubbing solutions in flue gas desulphurisation plants that operate with the calcium carbonate scrubbing process [29]...

The materials listed in Table 21 were investigated by simulating laboratory tests under operating conditions and exposure tests in waste water evaporator units of flue gas desulphurisation plants and waste incineration plants [64]. It was confirmed that only an approximate resistance can be estimated for the metallic materials in these plant sections. Precise material resistance data can only be determined for actual plants. The mass losses determined for alloy C-276 and alloy 59 after an exposure time of 9 months was only 0.053 mm/a (2.09 mpy) and 0.045 mm/a (1.77 mpy), respectively, with respect to the term of exposure. Therefore, they do not have technical significance. This results in the following proposal for materials for pipelines and tanks of waste water evaporator units of flue gas desulphurisation plants... 

Alloy 400 (NiCu30Fe, 2.4360) was used in three stages of the evaporator/crystallisa-tion unit for waste water from the absorption fluid of a flue gas desulphurisation plant at 364 K (91 °C) and a pH value of 8-10. A corrosion rate of 0.04 mm/a (1.57 mpy) was measured after an operating time of 4 years. The alloy was used because the previously fitted rubber-coated steel components required frequent repairs [74]. 

Altpeter, E. Wallis, E. Heubner, U. Erprobung verschiedener metallischer Legierungen fur die Abwasseraufbereitung hinter Rauchgasentschwefelimgsanlagen (Evaluation of different metal alloys for waste water treatment of flue gas desulphurisation plants) (in German) Werkst. Korros. 45 (1994) 10, p. 539-549... 

The ratio of limestone to fuel required for effective desulphurisation depends upon both the mineral and sulphur content of the coal. It may be possible to burn low sulphur (<0.8%) western coal directly with 90% sulphur retention thus avoiding the necessity for flue gas desulphurisation and still meeting environmental SO2 emission regulations (18). Fluidyne (19) have indicated that a 3.65% Illinois coal with 0.3 lbs. of dolomite added per pound of coal in a fluidised bed combustor can reduce SO2 emission to less than 1.2 lbs. of SO2 per million BTU thermal output thus meeting U.S. EPA limits for large plants. 

The potential of ammonia-based flue gas desulphurisation waste solution as a nitrogen fertiliser has been assessed by Gissel-Neilson and Bertelsen (1989) by field trials using barley and rye grass. The solution had the same fertiliser value as calcium-ammonium-nitrate. The toxic effects of sulphite were reduced by avoiding direct contact of the solution with the plants. 

The single furnace options incorporate flue gas desulphurisation (FGD) scrubbing whereas the two furnace options incorporate double contact sulphuric acid plants. 

Galos, K. A., Smakowski, T. S. Sc Szlugaj, J. (2003). Flue gas desulphurisation products from Polish coal-fired power-plants. Applied Energ)f, 75(3-4) 257-265. 

Another part of the integration is that the biological waste water treatment plant treats all the waste waters from the site as well as the municipal waste water. The off-gas treatment for the production of viscose is combined with a sulphuric acid production unit. Gases containing sulphur can also be used as combustion air in various combustion plants with flue-gas desulphurisation. Additionally, the supply networks for steam and process water are highly sophisticated. 

There are three basic stages to the process, shown in Figure 11.9, external to the electrolysis section. SO2 is absorbed and reacts with the bromine. The reactor product solution is then concentrated by evaporation using the sensible heat contained in the entering flue gas. All the HBr and the majority of the water are vaporised and an 80% to 85% sulphuric acid solution is produced. The desulphurised gas leaving the reactor is scrubbed with water to remove the HBr and the acid droplets. In the ISPRA plant the total electrode surface area is 64 m. The current density of operation is 2000 A m and at a temperature of 50°C the cell voltage is between 1.3-1.4 V and the current efficiency for bromine production is 90%. 

Up to now selective catalytic reduction has been the completely dominant method of flue gas NOx treatment. In this method ammonia is injected in the flue gas in the presence of a catalyst, commonly titanium oxide based, to reduce NO and NO2 to nitrogen and water. The catalyst can be placed in different positions in the flue gas flow, the important factor being that conditions such as the flue gas temperature are optimal (usually 300-400 C). The positions used for catalyst are high dust, where the catalyst is placed between the economiser and the air preheater low dust, with the catalyst situated after a hot gas precipitator and before the air pre-heater and tail end, with the catalyst situated after the desulphurisation plant (see Figure 1). The most widely used position worldwide is high dust, where untreated flue gas containing sulphur dioxide and particulates passes through the catalyst. 

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