[0030] For a coal-fired power plant boiler unit, the present invention will be further described in detail with reference to the accompanying drawings:
[0031] The wet ammonia flue gas cleaning system for simultaneous desulfurization and denitration shown in the figure includes a pre-dust removal device 2 arranged on the outlet flue of the coal-fired boiler unit 1 and a desulfurization and denitrification tower 5 for the main flue gas reaction device. The pre-dust removal device 2 adopts an electrostatic precipitator with a wire-plate four-stage electric field structure, which can collect more than 99.5% of dust particles in the flue gas. A hydrogen peroxide or ozone spray device 3 is provided on the flue between the pre-dust removal device 2 and the desulfurization and denitrification tower 5. The device can be an atomization sprayer with a grid structure. This atomization sprayer generally includes 1 to 5 A mother pipe, 4-10 branch pipes are arranged at equal intervals on each mother pipe, 5-10 atomizing nozzles are arranged at equal intervals on each branch pipe, and each branch pipe is arranged at equal intervals on the flue. The specific number of mother pipes and branch pipes The number of atomizing nozzles on each branch pipe is determined by the size of the flue section. The oxidant after atomization spray can cover the entire flue section to ensure rapid and full oxidation of the flue gas.
[0032] The desulfurization and denitrification tower 5 has a cylindrical structure, and it is sequentially provided with a bottom slurry pool area, a lower flue gas input area, a middle spray area, and an upper flue gas defogging area from bottom to top. Wherein, the bottom slurry tank area of the desulfurization and denitrification tower 5 is connected with an ammonia water supply device 20 and an air feed device 21. The lower flue gas input area of the desulfurization and denitrification tower 5 is provided with a flue gas inlet 4 connected with the hydrogen peroxide or ozone injection device 3. The central spray area of the desulfurization and denitrification tower 5 is arranged with multiple ammonia spray layers 6. The number of ammonia spray layers 6 mainly depends on the parameters such as the amount of flue gas to be treated, and a good gas can be achieved by arranging 3 to 5 channels. Liquid mass transfer. The upper flue gas defogging area of the desulfurization and denitrification tower 5 is equipped with a mist eliminator 7. The mist eliminator 7 adopts a combined defogging device, which consists of upper and lower defogging filters and a cleaning spray located between the upper and lower defogging filters. The shower part is constructed to completely effectively separate the moisture contained in the flue gas. The slurry pool area at the bottom of the desulfurization and denitrification tower 5 and the ammonia spray layer 6 are connected by an external slurry circulation pump 18 to ensure uninterrupted circulation of the ammonia desulfurizer.
[0033] The bottom of the desulfurization and denitrification tower 5 is provided with a slurry outlet 19, the slurry outlet 19 is connected to the inlet of the cyclone separator 12 through a slurry pump 17, and the underflow port of the cyclone separator 12 is connected to the inlet of the dehydrator 13, The solid outlet of the dehydrator 13 is connected to the dryer 14, the upper overflow port of the cyclone separator 12 and the liquid outlet of the dehydrator 13 are both connected to the inlet of the intermediate tank 15, and the outlet of the intermediate tank 15 is connected to the desulfurization through the recycling pump 16 The bottom slurry tank area of the denitrification tower 5 is connected to form a desulfurization and denitration by-product processing system. The slurry pump 17 pumps the slurry in the slurry pond area at the bottom of the desulfurization and denitrification tower 5 to the desulfurization and denitration by-product processing system. After separation and dehydration, ammonium sulfate and ammonium nitrate crystals are obtained, and then the desulfurization by-products ammonium sulfate and ammonium nitrate are obtained by drying. fertilizer. The separated waste liquid is pumped into the bottom slurry tank area of the desulfurization and denitrification tower 6 by the recovery circulation pump 16 to recirculate.
[0034] The top of the desulfurization and denitrification tower 5 is provided with a flue gas outlet 8, and the flue gas outlet 8 is connected to the chimney 11 through the flue gas reheater 9 and the induced draft fan 10 in sequence.
[0035] The wet ammonia flue gas cleaning process for simultaneous desulfurization and denitration of the present invention is as follows:
[0036] First, the flue gas discharged from the coal-fired boiler unit 1 enters the pre-dust removal device 2, and after the pre-dust removal treatment, more than 90% of the fly ash in the flue gas can be removed. Then the flue gas passes through the hydrogen peroxide or ozone injection device 3, and the injection volume of hydrogen peroxide or ozone is determined according to the following ratio: the molar ratio of hydrogen peroxide or ozone to nitric oxide in the flue gas is 1.0 to 1.2, and the reaction of nitric oxide and hydrogen peroxide or ozone The temperature is controlled within the range of 110~130℃, preferably 115~125℃, so that the nitric oxide NO in the flue gas can fully oxidize with the hydrogen peroxide or ozone carried by the atomizing air to generate nitrogen dioxide NO 2.
[0037] Then, the oxidized flue gas is fed into the desulfurization and denitrification tower 5 from the flue gas inlet 4, and is in reverse contact with the 28% ammonia water sprayed from the ammonia spray layer 6 to cause a gas-liquid two-phase reaction to remove the flue gas. Sulfur Dioxide SO in the Gas 2 And nitrogen dioxide NO 2 , At the same time generate a mixture of ammonium sulfite, ammonium nitrate and ammonium nitrite. Among them: the supply of ammonia for desulfurization and denitrification is determined in the following proportion: the molar ratio of ammonia required for desulfurization to sulfur dioxide in the flue gas is 2.1 to 2.3 to ensure that the sulfur dioxide in the flue gas fully reacts with the desulfurization absorbent, and the desulfurization efficiency is 95% or more; the molar ratio of ammonia required for denitration to nitrogen dioxide in the flue gas is 1.1-1.3 to ensure that the flue gas denitrification efficiency is above 90%.
[0038] Then, the generated ammonium sulfite, ammonium nitrate, and ammonium nitrite mixture slurry falls into the bottom slurry tank area of the desulfurization and denitrification tower 5, and oxidizes with the air introduced from the air feed device 21 to make the ammonium sulfite and Ammonium nitrite is converted into ammonium sulfate and ammonium nitrate slurry. The ammonium sulfate and ammonium nitrate slurry is then sent to the cyclone separator 12 through the slurry outlet 19 and the slurry pump 17, where the slurry is separated in the cyclone separator 12, the upper overflow returns to the intermediate tank 15, and the lower overflow enters the dehydration器13. The ammonium sulfate and ammonium nitrate crystals output from the solid outlet of the dehydrator 13 then enter the dryer 14, after being dried, they are sent to a warehouse or squeezed into a cake to obtain by-product ammonium sulfate and ammonium nitrate fertilizer, which are output from the liquid outlet of the dehydrator 13 The waste liquid also flows into the intermediate tank 15, and the waste liquid in the intermediate tank 15 enters the desulfurization and denitrification tower 5 through the circulation pump 16 for recycling.
[0039] Finally, the flue gas after the desulfurization and denitrification reaction passes through the mist eliminator 7, after removing the liquid droplets carried, enters the flue gas reheater 9 from the flue gas outlet 8 and raises the temperature of the flue gas to about 80°C. The induced draft fan 10 is discharged into the chimney 11. Properly increasing the temperature of the flue gas can effectively prevent the flue gas from corroding the flue and chimney.
