CN210814730U

CN210814730U - Urea ammonia production decomposer of low-temperature SCR system

Info

Publication number: CN210814730U
Application number: CN201921674370.8U
Authority: CN
Inventors: 叶燕仙
Original assignee: Zhejiang Agricultural Business College
Current assignee: Zhejiang Agricultural Business College
Priority date: 2019-10-09
Filing date: 2019-10-09
Publication date: 2020-06-23
Anticipated expiration: 2029-10-09

Abstract

The utility model provides a urea ammonia production decomposer of low temperature SCR system relates to denitration technical field, including back flow, high temperature draught fan, air heater, urea pyrolyzer, the entrance point and the exit end of back flow all are linked together with the tobacco pipe, high temperature draught fan, air heater, urea pyrolyzer set gradually on the back flow, be provided with the extravagant urea energy-saving mechanism of reducible urea on the urea feed liquor pipe of urea pyrolyzer. This urea system ammonia decomposes ware of low temperature SCR system extracts original part flue gas through the high temperature draught fan and is sent into the urea pyrolyzer after being heated by the air heater and carries out the system ammonia, on the basis of energy saving, the pyrolysis urea of hydrolysising as far as complete, and then reach high ammonia yield, provide an economic solution for the high denitration rate of low temperature SCR system.

Description

Urea ammonia production decomposer of low-temperature SCR system

Technical Field

The utility model relates to a denitration technology field specifically is a urea system ammonia decomposer of low temperature SCR system.

Background

Nitrogen Oxides (NO)_X) Is the main reason of acid rain, and is also the main reason of the formation of near-formation atmospheric ozone, secondary fine particle pollution, surface water eutrophication and photochemical smog. The nitrogen oxides which currently cause atmospheric pollution are mainly Nitric Oxide (NO) and dioxideNitrogen (NO)₂) The main sources are mobile sources (motor vehicles, about 49%) and stationary sources (thermal power plants, industrial boilers, about 46%). With country to NO_XThe emission is increasingly regarded, and NO is firstly put into consideration from the national environmental protection 'twelve five' program_XThe emission reduction is required to be 10% by incorporating a constraint system, and the NOx emission amount of China is reduced by 15% on the basis of 2015 in 2020 of the national environmental protection plan. The removal and emission reduction of nitrogen oxides are increasingly on the routine of environmental protection departments and production units.

The existing widely applied nitrogen oxide removal technologies include a low-nitrogen combustion technology and a flue gas denitration technology, wherein the SCR flue gas denitration technology is widely applied in China due to the characteristics of high denitration efficiency, low ammonia escape rate and the like. In the SCR denitration system, the reducing agent is a large consumable, and the consumption cost of the reducing agent directly influences the overall economic index of the denitration system. Currently, the most common reducing agents in the denitration system in the world are 3: liquid ammonia, ammonia water and urea. According to the regulations of 'identification of serious dangerous source of dangerous chemicals' GB 18218-2009, the liquid ammonia is stored for more than 10t, namely, the liquid ammonia constitutes a serious dangerous source, and the liquid ammonia also has a safety problem. As a non-hazardous ammonia-making raw material, the urea has the same denitration performance as liquid ammonia, is a green fertilizer, has no toxicity, is completely used, has no regulation limitation, and is convenient to transport, store and use. In the technical policy of nitrogen oxide control in thermal power plants and the design specification of thermal power plants, urea is preferably used as a reducing agent in power plants (denitration facilities in dense population areas) in major and middle cities and suburbs.

There are generally two methods for producing the reducing agent ammonia from urea: pyrolysis and hydrolysis. The hydrolysis means that urea is decomposed in the form of aqueous solution, the method needs high-pressure steam equipment and a complex wastewater treatment system, the investment cost is high, byproducts which are easy to adhere to fly ash are generated after hydrolysis, and the active ingredients of the SCR catalyst are easy to damage and cause catalyst blockage; the pyrolysis is to rapidly heat the atomized urea solution to obtain NH₃The latter method gradually becomes a method of removing the polymer with the advantages of less investment, complete reaction, no generation of intermediate polymer and the likeThe mainstream method for preparing ammonia by using nitrate is.

NO in low temperature flue gas_XThe removal of the organic pollutants is one of important development directions for treating the air pollutants, and the organic pollutants must become a research hotspot in the environmental protection field in a period of time in the future.

The active temperature window of a common vanadium titanium-based catalyst of a Selective Catalytic Reduction (SCR) denitration technology widely applied to the power industry at present is generally 300-450 ℃. However, the flue gas temperature in the non-electric power industry is generally lower than 300 ℃, and the urea aqueous solution cannot be completely pyrolyzed and hydrolyzed by the heat of tail gas, so that the denitration effect is influenced.

SUMMERY OF THE UTILITY MODEL

Technical problem to be solved

To the not enough of prior art, the utility model provides an energy-conserving urea ammonia preparation decomposer of low temperature SCR system.

(II) technical scheme

In order to achieve the above purpose, the utility model discloses a following technical scheme realizes: the utility model provides a urea ammonia production decomposer of low temperature SCR system sets up on the tobacco pipe, including back flow, high temperature draught fan, air heater, urea pyrolyzer, the entrance point and the exit end of back flow all are linked together with the tobacco pipe, high temperature draught fan, air heater, urea pyrolyzer set gradually on the back flow, be provided with the urea energy-saving mechanism of reducible urea waste on the urea feed liquor pipe of urea pyrolyzer.

Preferably, the urea energy-saving mechanism comprises a liquid inlet main pipe, a water pump set, a negative-pressure-free tank, a branch pump and a liquid outlet main pipe connected with the urea pyrolyzer, wherein the liquid inlet main pipe is connected with a urea source through a main pump, the liquid inlet main pipe, the water pump set and the liquid outlet main pipe are connected in sequence, and the liquid inlet main pipe, the negative-pressure-free tank, the branch pump and the liquid outlet main pipe are connected in sequence.

Preferably, a vacuum suppressor is arranged on the non-negative pressure tank.

Preferably, the water pump set comprises a first branch pump, a second branch pump and a third branch pump, and the water inlet end and the water outlet end of the first branch pump, the second branch pump and the third branch pump are respectively connected with the liquid inlet main liquid pipe and the liquid outlet main liquid pipe in parallel.

Preferably, check valves are arranged at the liquid outlet ends of the branch pump I, the branch pump II, the branch pump III and the branch pump IV which are connected with the liquid outlet main pipe.

Preferably, the liquid inlet ends of the first branch pump, the second branch pump, the third branch pump and the negative pressure-free tank connected with the liquid inlet main pipe are all provided with electromagnetic valves.

(III) advantageous effects

The utility model provides a urea ammonia production decomposer of low temperature SCR system. The method has the following beneficial effects:

1. this urea system ammonia decomposes ware of low temperature SCR system extracts original part flue gas through the high temperature draught fan and is sent into the urea pyrolyzer after being heated by the air heater and carries out the system ammonia, on the basis of energy saving, the pyrolysis urea of hydrolysising as far as complete, and then reach high ammonia yield, provide an economic solution for the high denitration rate of low temperature SCR system.

2. This urea ammonia production decomposer of low temperature SCR system sets up urea energy-saving mechanism through the urea feed liquor end at urea pyrolyzer, makes its discharge that can the flue gas adjust the feed liquor volume of urea, reduces the waste that causes because the flue gas is unstable, and is green energy-conserving.

Drawings

FIG. 1 is a side view of the shaft of the present invention;

FIG. 2 is a top view of the structure of the present invention;

fig. 3 is a schematic diagram of the urea energy-saving mechanism of the present invention.

In the figure: the device comprises a smoke pipe 1, a return pipe 2, a high-temperature induced draft fan 3, an air heater 4, a urea pyrolyzer 5, a urea energy-saving mechanism 6, a liquid inlet header pipe 61, a master cylinder 62, branch pipes 63, branch pumps 64, branch pumps 65, branch pumps 66, branch pumps 67, a negative pressure-free tank 68, a liquid outlet header pipe 69, a vacuum suppressor 7, an electromagnetic valve 8 and a check valve 9.

Detailed Description

The embodiment of the utility model provides a urea ammonia production decomposer of low temperature SCR system, as shown in fig. 1-3, set up on the tobacco pipe 1 that the temperature is less than 300 ℃, including back flow 2, high temperature draught fan 3, air heater 4, urea pyrolyzer 5.

As shown in fig. 1, the return pipe 2 is a U-shaped pipe, the inlet end and the outlet end of the return pipe 2 are both communicated with the smoke pipe 1, and the high-temperature induced draft fan 3, the air heater 4 and the urea pyrolyzer 5 are sequentially arranged on the return pipe 2.

The urea pyrolyzer 5 is prior art and is a commercially available product.

The urea pyrolysis ammonia preparation process is to atomize urea solution with the mass concentration of about 50 percent and generate ammonia NH by pyrolysis at the high temperature of 350-650 DEG C₃Water H₂O and carbon dioxide CO₂And the ammonia is the reducing agent required by the SCR denitration system. The mixed gas containing ammonia from the pyrolysis furnace enters an ammonia injection grid of an inlet flue of the SCR reactor through a specific pipeline and a distribution module, is sprayed into the flue gas and is fully mixed with the flue gas, and when the mixed flue gas flows across the surface of a catalyst in the reactor, the ammonia is used for converting NO into NO_XReduction to N₂And H₂O, to remove nitrogen oxide NO in the flue gas_XThe purpose of (1).

The high-temperature draught fan 3 extracts low-temperature flue gas and heats the low-temperature flue gas by the air heater 4, so that the temperature of the flue gas reaches more than 350 ℃. The high-temperature flue gas enters the urea pyrolyzer 5 and then is mixed with the urea solution.

Urea, also known as urea, has a molecular formula of CO (NH2)2 and a melting point of 132.7 ℃. Since urea is unstable to heat, thermal decomposition reaction occurs when it is heated, and when the reaction temperature is lower than 360 ℃, these intermediate reaction products and side reaction products are generated in large quantities, which is not favorable for complete decomposition of urea. When the reaction temperature is higher than 360 ℃, the decomposition reaction of urea is mainly as follows: CO (NH)₂)₂→NH₃+ HNCO Urea → Ammonia + Isocyanic acid, HNCO + H₂O→NH₃+CO₂Isocyanic acid + water → ammonia + carbon dioxide.

Urea (CO (NH)₂)₂) Decomposed to ammonia (NH) when heated₃) And isocyanic acid (HNCO) which is hydrolyzed to generate ammonia (NH3) and carbon dioxide (CO) when meeting water vapor₂). The above reaction is completed in an extremely short time, and therefore, can be synthesized as follows: CO (NH)₂)₂+H₂O→2NH₃+CO₂Urea+ water → ammonia + carbon dioxide.

Because the emission of flue gas is different on each node according to actual energy consumption, but the power of the urea solution pump is rated, when the emission of flue gas is rated, the urea solution pump can be economically supplied, when the emission of flue gas is suddenly increased, the urea solution pump can not be completely supplied, so that the denitration is insufficient, when the emission of flue gas is less than the rated, the supply of the urea solution pump becomes excessive, so that the waste of urea solution is caused, and a urea energy-saving mechanism 6 capable of reducing the waste of urea is arranged on a urea liquid inlet pipe of the urea pyrolyzer 5.

The urea energy-saving mechanism 6 is arranged at the urea liquid inlet end of the urea pyrolyzer 5, so that the urea liquid inlet amount can be adjusted by the emission amount of the flue gas, the waste caused by unstable flue gas is reduced, and the urea liquid inlet device is green and energy-saving.

The urea energy-saving mechanism 6 comprises a liquid inlet main pipe 61, a water pump set, a non-negative pressure tank 68 for temporarily storing urea solution, a branch pump four 67 and a liquid outlet main pipe 69 connected with the urea pyrolyzer 5, wherein the liquid inlet main pipe 61 is connected with a urea source through a main pump 62, and the power of the main pump 62 is rated. The liquid inlet header pipe 61, the water pump set and the liquid outlet header pipe 69 are connected in sequence, and the liquid inlet header pipe 61, the non-negative pressure tank 68, the branch pump IV 67 and the liquid outlet header pipe 69 are connected in sequence.

The non-negative pressure tank 68 is provided with a vacuum suppressor 7. The vacuum suppressor 7 is used to eliminate the negative pressure in the no-negative-pressure tank 68, and prevent the pressure of the no-negative-pressure tank 68 from being excessively high due to the pressure of the master pump 62.

The water pump group comprises a first branch pump 64, a second branch pump 65 and a third branch pump 66, wherein the water inlet end and the water outlet end of the first branch pump 64, the second branch pump 65 and the third branch pump 66 are respectively connected with the liquid inlet main liquid header pipe 61 and the liquid outlet main liquid pipe 69 in parallel.

The liquid outlet ends of the first branch pump 64, the second branch pump 65, the third branch pump 66 and the fourth branch pump 67 which are connected with the liquid outlet main pipe 69 are all provided with check valves 9.

The liquid inlet ends of the first branch pump 64, the second branch pump 65, the third branch pump 66 and the non-negative pressure tank 68 which are connected with the liquid inlet header pipe 61 are all provided with electromagnetic valves 8.

The total power of the water pump group is the same as the power of the master pump 62. The amount of the urea solution supplied by the water supply pressure of the water pump set is the same as the amount of the ammonia solution required by the rated smoke emission, the non-negative pressure tank 68 and the water pump set are arranged in parallel, when the smoke emission is less than the rated amount, the ammonia solution of the liquid inlet main pipe 61 can be directly supplied by the water pump set, the number of the branch pumps which need to be started according to the actual water consumption is also used, and meanwhile, the redundant water of the liquid inlet main pipe 61 is conveyed into the non-negative pressure tank 68 by utilizing the redundant water pressure of the main pump 62 for storage; when the discharge amount of the flue gas is larger than the rated amount, the water pressure of the main pump 62 cannot meet the flue gas reaction, the branch pump four 67 is started to supplement the ammonia water stored in the non-negative pressure tank 68 into the liquid outlet main pipe 69, so that the water pressure of the liquid outlet main pipe 69 can meet the flue gas, and the hidden danger that the water pump set empties the pump is effectively eliminated. Energy conservation and environmental protection.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims

1. The utility model provides a urea ammonia production decomposer of low temperature SCR system, sets up on tobacco pipe (1), its characterized in that: including back flow (2), high temperature draught fan (3), air heater (4), urea pyrolyzer (5), the entrance point and the exit end of back flow (2) all are linked together with tobacco pipe (1), high temperature draught fan (3), air heater (4), urea pyrolyzer (5) set gradually on back flow (2), be provided with the urea energy-saving mechanism (6) of reducible urea waste on the urea feed liquor pipe of urea pyrolyzer (5).

2. The urea-to-ammonia decomposer of the low-temperature SCR system of claim 1, wherein: urea energy-saving mechanism (6) include inlet manifold (61), water pump package, no negative pressure jar (68), divide four (67) of pump and go out liquid header pipe (69) continuous with urea pyrolyzer (5), inlet manifold (61) link to each other with the urea source through master cylinder (62), inlet manifold (61), water pump package, play liquid header pipe (69) link to each other in proper order, inlet manifold (61), no negative pressure jar (68), divide four (67) of pump, play liquid header pipe (69) link to each other in proper order.

3. The urea-to-ammonia decomposer of the low-temperature SCR system of claim 2, wherein: the non-negative pressure tank (68) is provided with a vacuum suppressor (7).

4. The urea-to-ammonia decomposer of the low-temperature SCR system of claim 2, wherein: the water pump set comprises a first branch pump (64), a second branch pump (65) and a third branch pump (66), wherein the water inlet end and the water outlet end of the first branch pump (64), the second branch pump (65) and the third branch pump (66) are respectively connected with the liquid inlet main pipe (61) and the liquid outlet main pipe (69) in parallel.

5. The urea-to-ammonia decomposer of the low-temperature SCR system of claim 4, wherein: and the liquid outlet ends of the branch pump I (64), the branch pump II (65), the branch pump III (66) and the branch pump IV (67) which are connected with the liquid outlet main pipe (69) are provided with check valves (9).

6. The urea-to-ammonia decomposer of the low-temperature SCR system of claim 4, wherein: and the liquid inlet ends of the branch pump I (64), the branch pump II (65), the branch pump III (66), the non-negative pressure tank (68) and the liquid inlet header pipe (61) are all provided with electromagnetic valves (8).