Dry goods! CFB boiler best desulfurization method full resolution

"The published air quality monitoring results are up to standard and why are gray and blue skies not visible?" This widespread question not only reflects the worsening haze problem, but also shows the deviation between environmental governance and actual results. And this problem, with a large number of thermal power units flue gas desulfurization process using electric field less than the number of ESP + wet desulfurization (without GGH) is not unrelated.

The circulating fluidized bed (CFB) boiler technology is a highly efficient and low-pollution clean combustion technique developed rapidly in recent ten years. As an environment-friendly boiler, CFB boiler can inject some limestone to achieve certain efficiency of dry desulfurization in the furnace. Desulfurization efficiency in the furnace is generally 60% ~ 90% (depending on the Ca / S and boiler structure) between. Due to the fuel characteristics of CFB boilers, however, further flue gas desulfurization must be carried out behind the furnace in some CFB boilers that burn high-sulfur fuels or where SO2 emission standards are stringent.

The author compares the traditional wet desulfurization process (calcium method, magnesium method, ammonia method) and circulating fluidized bed dry desulfurization process, in order to obtain the most suitable CFB boiler flue gas desulfurization methods.

CFB boiler flue gas desulfurization efficiency of the traditional route, the general is the flue gas through the bag filter (or electrostatic precipitator) after the dust, and then by-pass into the wet FGD flue gas desulfurization.

Due to the high concentration of dust in CFB boiler flue gas and the high specific resistance of soot after desulfurization in the furnace, Therefore, the traditional CFB boiler flue gas dust removal generally take the package bag filter program. After the traditional dust removal desulfurization process, what are the problems?

① incomplete reaction of the boiler discharge soot CaO can not be comprehensive utilization, resulting in waste of resources. Free CaO also seriously affected the comprehensive utilization of CFB boiler ash, resulting in greater waste.

② serious corrosion.

③ wet FGD chimney overall costly. In recent years, the wet desulfurization plant tends to adopt wet chimney direct discharge technology, chimney barrel special anti-corrosion treatment, using more titanium-steel composite plate inner tube process, resulting in the overall cost of the chimney greatly increased.

④ serious scaling.

⑤ cancel the bypass, the use of tandem wet FGD process program, will host unit operating rate to bring a severe test.

Relevant regulations have been promulgated by the state environmental protection department, which require that the flue gas desulfurization unit of the newly-built unit should no longer be provided with a bypass flue. The built unit has already set up a desulfurization device by-pass, and a lead seal must be installed by-pass. Therefore, when the wet FGD device outages, the crew must be out of service. Due to corrosion and scaling and other reasons, the high failure rate of the wet desulfurization process (calcium method, magnesium method, ammonia method) means that the unit adopting the wet desulfurization process should often be stopped due to the failure of the desulfurization device, the loss will be very much serious.

⑥ desulfurization system can not respond quickly to changes in boiler load operation.

Limestone - gypsum wet desulfurization process start and stop more troublesome, longer time, the corresponding boiler load can not be quickly changed, but also in the system is not put into operation must be maintained.

⑦ wet FGD chimney discharge of "gypsum rain," seriously affecting the quality of the surrounding environment.

⑧ desulfurization process produces fine particulate concentration, wastewater "double" by-product contamination, especially the adsorption of fine particles of heavy metals Hg, will have greater harm to human health.

CFB boiler supporting the use of circulating fluidized bed dry desulfurization + bag filter flue gas desulfurization dust integrated new technology program, the direct use of CFB boiler "calcium-rich ash," "after the first desulfurization dust" The desulfurization dust integrated process program has the following advantages.

(1) The use of a large amount of incompletely reacted CaO contained in the soot discharged from the boiler as an absorbent significantly reduces the operating costs and meets the requirements of circular economy.

② flue gas circulating fluidized bed dry desulfurization of the chimney without corrosion.

Circulating fluidized bed dry desulfurization tower fierce turbulent high-density particle bed formed by the huge adsorption surface area, 100% removal of SO3, HCl, HF and all other acid gases. Therefore, the entire desulfurization system and the subsequent chimney without any corrosion. Not only greatly saving the investment of the anti-corrosion of the chimney, but also avoids the loss of boiler unit outage caused by the problems of anticorrosive implementation of the chimney.

③ After the first desulfurization dust, smoke temperature decreases, flue gas chemical abuse ability greatly weakened, filter bag life is substantially extended. In addition, the use of filter cake layer also helps to improve the desulfurization efficiency. CFB boiler supporting flue gas circulating fluidized bed dry desulfurization + bag filter, the comprehensive desulfurization efficiency is very easy to reach more than 95%.

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