Hydrolysis waste liquid zero discharge treatment system for denitration system of thermal power plant

Abstract

The utility model discloses a zero-discharge treatment system for hydrolysis waste liquid of a denitration system of a thermal power plant. The zero-discharge treatment system for the hydrolysis waste liquid of the denitration system of the thermal power plant comprises a drain tank, a hydrolysis waste liquid pit and an SNCR (Selective Non-Catalytic Reduction) spray gun, the drain tank is connected with the hydrolysis waste liquid pit, and the hydrolysis waste liquid pit is connected with the SNCR spray gun through a pipeline; the hydrolysis waste liquid in the hydrolysis waste liquid pit contains urea; a nozzle of the SNCR spray gun is arranged in a denitration area of the pulverized coal furnace or at the position of an inlet flue of a cyclone separator of the circulating fluidized bed boiler, waste liquid sprayed by the SNCR spray gun reacts with oxynitride in flue gas of the pulverized coal furnace or the circulating fluidized bed boiler, and harmless treatment of the flue gas is achieved.

Description

Technical Field

[0001] The utility model belongs to the technical field of environmental protection, and particularly relates to a zero-emission treatment system for hydrolysis waste liquid of a denitration system in a thermal power plant. Background Art

[0002] In the flue gas denitration process of a thermal power plant, urea is usually used to prepare the reducing agent ammonia by urea hydrolysis and urea pyrolysis processes. The process steps of the urea hydrolysis process are as follows: a urea solution with a mass concentration of 50% is sent to a hydrolysis reactor by a urea delivery pump, and under appropriate temperature and pressure, the urea solution decomposes into a mixed gas product containing ammonia, carbon dioxide and water vapor. Since by-products such as biuret are generated during the hydrolysis reaction process. Biuret itself can carry out a condensation reaction, and the isocyanate substances generated will form sediments if not hydrolyzed in time, thus blocking pipeline equipment. With the long-term operation, the impurity concentration becomes higher and higher, seriously affecting the normal operation of the urea hydrolysis system. Therefore, the hydrolysis reactor needs to be regularly drained to a waste water tank, generally once or twice a week, and the discharged waste liquid contains undecomposed urea, and the main impurities are biuret and the like. The urea hydrolysis waste liquid needs to be properly treated to meet the requirement of zero discharge of waste water from a thermal power plant.

[0003] At present, the traditional treatment process of urea hydrolysis waste liquid mainly sends the waste liquid to the total waste water treatment system of the power plant for treatment. The main treatment methods include evaporation and drying treatment, evaporation and centrifugation treatment, and boiler reuse, etc. The evaporation and drying treatment is to input the waste liquid into an evaporator for heating and concentration, and then discharge it into a dryer for drying; the evaporation and centrifugation treatment is to cool the concentrated liquid after concentration, and then discharge it into a centrifuge to separate the cooled and crystallized urea particles. For the waste liquid to meet the water quality standard of a low-pressure steam boiler, treatments such as iron removal, catalysis, deoxidation and dosing control are required. The process is cumbersome, the investment cost is high, and the equipment maintenance workload is large. The treated urea particles are a mixture of biuret and the like and cannot be reused.

[0004] In view of the current requirement of zero discharge of sewage from a thermal power plant, a new type of denitration system urea hydrolysis waste liquid treatment system is proposed, which has a simple process, low investment cost, small equipment maintenance workload, and can realize zero discharge and resource utilization of urea hydrolysis waste liquid. Summary of the Utility Model

[0005] The purpose of the utility model is: in order to overcome the problems of the prior art, a zero-emission treatment system for hydrolysis waste liquid of a denitration system in a thermal power plant is disclosed, which effectively utilizes the urea component in the waste liquid, reduces the sewage treatment cost of the thermal power plant, and finally realizes the true zero emission of urea hydrolysis waste liquid.

[0006] The purpose of the utility model is realized by the following technical solutions:

[0007] A zero-emission treatment system for hydrolysis waste liquid of a denitrification system in a thermal power plant, the zero-emission treatment system for hydrolysis waste liquid of the denitrification system in the thermal power plant comprising: a drain tank, a hydrolysis waste liquid pit and an SNCR spray gun;

[0008] The drain tank is connected to the hydrolysis waste liquid pit, and the hydrolysis waste liquid pit is connected to the SNCR spray gun through a pipeline; the hydrolysis waste liquid in the hydrolysis waste liquid pit contains urea;

[0009] The nozzle of the SNCR spray gun is arranged at the denitrification area of the pulverized coal furnace or at the inlet flue position of the cyclone separator of the circulating fluidized bed boiler. The waste liquid sprayed by the SNCR spray gun reacts with nitrogen oxides in the flue gas of the pulverized coal furnace or the circulating fluidized bed boiler to achieve harmless treatment of the flue gas.

[0010] According to a preferred embodiment, the denitrification reaction temperature in the furnace of the pulverized coal furnace is 850 - 1100 °C.

[0011] According to a preferred embodiment, the denitrification reaction temperature of the circulating fluidized bed boiler is 850 - 950 °C.

[0012] According to a preferred embodiment, the drain tank transports the drain water to the hydrolysis waste liquid pit through a drain pump to complete the dilution of the hydrolysis waste liquid in the hydrolysis waste liquid pit.

[0013] According to a preferred embodiment, a control valve is further provided on the pipeline from the drain tank to the hydrolysis waste liquid pit.

[0014] According to a preferred embodiment, a liquid level gauge is provided on the side wall of the hydrolysis waste liquid pit for monitoring the liquid level in the hydrolysis waste liquid pit.

[0015] According to a preferred embodiment, a waste liquid pump is provided on the pipeline between the hydrolysis waste liquid pit and the SNCR spray gun.

[0016] According to a preferred embodiment, the zero-emission treatment system for hydrolysis waste liquid of the denitrification system in the thermal power plant further includes a NO X monitoring device. The NO X monitoring device is arranged at the flue gas outlet of the pulverized coal furnace or the circulating fluidized bed boiler for monitoring the content of nitrogen oxides in the flue gas discharged.

[0017] According to a preferred embodiment, the waste liquid pump is configured to control the corresponding amount of waste liquid transported to the SNCR spray gun based on the monitoring result of the NO X monitoring device.

[0018] The main solution of the present utility model and its various further alternative solutions can be freely combined to form multiple solutions, all of which are solutions that can be adopted and claimed by the present utility model. Those skilled in the art can understand that there are various combinations according to the prior art and common general knowledge after understanding the solution of the present utility model, and all of them are the technical solutions to be protected by the present utility model, and will not be enumerated herein.

[0019] Advantages of the present utility model:

[0020] The present invention dilutes the urea hydrolysis waste liquid by using the original drain water of the denitration system, and then pumps it to the SNCR spray gun through a pump, and sprays it into the furnace of the pulverized coal boiler or the inlet of the cyclone separator of the circulating fluidized bed boiler. The biuret and the high-temperature decomposition products of biuret in the dilution liquid are completely decomposed at a high temperature above 800°C. Urea decomposes into ammonia and water at a suitable temperature, and ammonia reduces the nitrogen oxides in the flue gas to generate nitrogen and water. No additional chemicals need to be added during the process, the process system is simple, the equipment maintenance workload is small, the investment cost is low, zero discharge of the urea hydrolysis waste liquid and resource utilization of the useful components in the waste liquid are realized, the improvement of the environmental ecology is promoted, and remarkable effects are achieved both economically and environmentally. Description of the drawings

[0021] Figure 1 is a schematic structural diagram of an implementation of the zero-discharge treatment system for hydrolysis waste liquid of the denitration system in a thermal power plant of the present utility model;

[0022] Figure 2 is a schematic structural diagram of an implementation of the zero-discharge treatment system for hydrolysis waste liquid of the denitration system in a thermal power plant of the present utility model;

[0023] Among them, 1 - drain water tank, 2 - control valve, 3 - drain water pump, 4 - hydrolysis waste liquid pit, 5 - liquid level gauge, 6 - waste liquid pump, 7 - SNCR spray gun, 8 - pulverized coal boiler, 9 - circulating fluidized bed boiler, 10 - NO X monitoring device. Specific implementation manners

[0024] The following uses specific specific examples to illustrate the implementation manners of the present utility model. Those skilled in the art can easily understand other advantages and effects of the present utility model from the content disclosed in this specification. The present utility model can also be implemented or applied through other different specific implementation manners, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present utility model. It should be noted that, without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0025] It should be noted that: similar reference numerals and letters represent similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0026] In the description of the present utility model, it should be noted that the orientation or positional relationship indicated by terms such as "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the present utility model is usually placed during use. It is only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be construed as a limitation to the present utility model. In addition, terms such as "first", "second", "third", etc. are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance.

[0027] In addition, terms such as "horizontal", "vertical", "hanging", etc. do not mean that the components are required to be absolutely horizontal or hanging, but can be slightly inclined. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and does not mean that the structure must be completely horizontal, but can be slightly inclined.

[0028] In the description of the present utility model, it should also be noted that unless otherwise clearly specified and defined, the terms "set", "installed", "connected", "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present utility model can be understood according to specific circumstances.

[0029] In addition, it should be pointed out in the present utility model that in the present utility model, if the specifically involved structure, connection relationship, positional relationship, power source relationship, etc. are not specifically written, the structure, connection relationship, positional relationship, power source relationship, etc. involved in the present utility model are all known to those skilled in the art on the basis of the prior art without creative labor.

[0030] Refer to Figure 1 and Figure 2 As shown in

[0031] a zero-emission treatment system for hydrolysis waste liquid of a thermal power plant denitration system is shown in the figure. The zero-emission treatment system for hydrolysis waste liquid of the thermal power plant denitration system includes: a drain tank 1, a hydrolysis waste liquid pit 4, and an SNCR spray gun 7;

[0032] The nozzle of the SNCR spray gun 7 is arranged at the denitrification area of the pulverized coal furnace 8 or at the inlet flue of the cyclone separator of the circulating fluidized bed boiler 9. The waste liquid sprayed by the SNCR spray gun 7 reacts with nitrogen oxides in the flue gas of the pulverized coal furnace 8 or the circulating fluidized bed boiler 9 to achieve harmless treatment of the flue gas.

[0033] The denitrification reaction temperature in the furnace of the pulverized coal furnace 8 is 850 - 1100 °C. The denitrification reaction temperature of the circulating fluidized bed boiler 9 is 850 - 950 °C. The main impurity in the diluted waste liquid, biuret, starts to decompose at 193 °C. As the temperature rises, it is converted into melamine, and melamine starts to decompose into ammonia, cyanogen, and nitrogen at 330 - 360 °C. At the same time, urea in the diluted waste liquid decomposes at high temperature to generate NH3, and NH3 reacts with NO X in the flue gas to generate N2 and H2O.

[0034] Preferably, the drain tank 1 transports the drain water to the hydrolysis waste liquid pit 4 through the drain pump 3 to complete the dilution of the hydrolysis waste liquid in the hydrolysis waste liquid pit 4.

[0035] Preferably, a control valve 2 is also provided on the pipeline from the drain tank 1 to the hydrolysis waste liquid pit 4.

[0036] Preferably, a liquid level gauge 5 is provided on the side wall of the hydrolysis waste liquid pit 4 for monitoring the liquid level in the hydrolysis waste liquid pit 4.

[0037] Preferably, a waste liquid pump 6 is provided on the pipeline between the hydrolysis waste liquid pit 4 and the SNCR spray gun 7.

[0038] Preferably, the hydrolysis waste liquid zero - discharge treatment system of the thermal power plant denitrification system further includes a NO X monitoring device 10. The NO X monitoring device 10 is arranged at the flue gas outlet of the pulverized coal furnace 8 or the circulating fluidized bed boiler 9 for monitoring the content of nitrogen oxides in the discharged flue gas.

[0039] Preferably, the waste liquid pump 6 is configured to control the corresponding amount of waste liquid transported to the SNCR spray gun 7 based on the monitoring results of the NOX monitoring device 10.

[0040] In the hydrolysis waste liquid zero - discharge treatment system of the denitrification system of the thermal power plant of the present utility model, the hydrolysis waste liquid of the thermal power plant denitrification is discharged into the hydrolysis waste liquid pit 4. The drain pump 3 is controlled by the control valve 2 to transport the drain water from the drain tank 1 to dilute the waste liquid to a certain concentration. When the liquid level in the hydrolysis waste liquid pit 4 is high, according to the feedback data of the NO X concentration monitoring device 10, when the original SNCR denitrification efficiency is insufficient, the diluted waste liquid is sprayed into the denitrification area of the pulverized coal furnace or the inlet flue of the cyclone separator of the circulating fluidized bed boiler through the waste liquid pump 6 and the NCR spray gun 7.

[0041] Biuret and the high-temperature decomposition products of biuret in the diluent are completely decomposed at a high temperature above 800°C. Urea decomposes into ammonia and water at an appropriate temperature, and the ammonia reduces the nitrogen oxides in the flue gas to produce nitrogen and water. No additional chemicals need to be added during the process. All the urea hydrolysis waste liquid is sprayed into the SNCR denitration system, making full use of the urea in the waste liquid, not generating secondary waste, achieving true zero emissions, and at the same time realizing the resource utilization of the waste liquid. The process system is simple, the equipment maintenance workload is small, and the investment cost is low. The zero emissions of the urea hydrolysis waste liquid and the resource utilization of the useful components in the waste liquid are realized, promoting the improvement of the environmental ecology and achieving remarkable results in both economy and environmental protection.

[0042] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A zero-emission treatment system for hydrolysis waste liquid in a denitration system of a thermal power plant, characterized in that, The zero-emission treatment system for hydrolysis waste liquid of the denitration system in the thermal power plant includes: a drain tank (1), a hydrolysis waste liquid pit (4), and an SNCR spray gun (7); The drain tank (1) is connected to the hydrolysis waste liquid pit (4), and the hydrolysis waste liquid pit (4) is connected to the SNCR spray gun (7) through a pipeline; the hydrolysis waste liquid in the hydrolysis waste liquid pit (4) contains urea; The nozzle of the SNCR spray gun (7) is arranged at the denitration area of the pulverized coal furnace (8) or at the inlet flue position of the cyclone separator of the circulating fluidized bed boiler (9). The waste liquid sprayed by the SNCR spray gun (7) reacts with the nitrogen oxides in the flue gas of the pulverized coal furnace (8) or the circulating fluidized bed boiler (9) to achieve harmless treatment of the flue gas.

2. The zero-emission treatment system for hydrolysis waste liquid of the denitration system in a thermal power plant according to claim 1, characterized in that, The denitration reaction temperature in the furnace of the pulverized coal furnace (8) is 850 - 1100 °C.

3. The zero-emission treatment system for hydrolysis waste liquid of the denitration system in a thermal power plant according to claim 1, wherein, The denitration reaction temperature of the circulating fluidized bed boiler (9) is 850 - 950 °C.

4. The zero-emission treatment system for hydrolysis waste liquid of the denitration system in a thermal power plant according to claim 1, characterized in that, The drain tank (1) transports the drain water to the hydrolysis waste liquid pit (4) through a drain pump (3) to complete the dilution of the hydrolysis waste liquid in the hydrolysis waste liquid pit (4).

5. The zero-emission treatment system for hydrolysis waste liquid of the denitration system in a thermal power plant according to claim 4, characterized in that, A control valve (2) is also provided on the pipeline from the drain tank (1) to the hydrolysis waste liquid pit (4).

6. The zero-emission treatment system for hydrolysis waste liquid of the denitration system in a thermal power plant according to claim 1, characterized in that, A liquid level gauge (5) is provided on the side wall of the hydrolysis waste liquid pit (4) to complete the liquid level monitoring in the hydrolysis waste liquid pit (4).

7. The zero - discharge treatment system for hydrolysis waste liquid of the denitration system in a thermal power plant according to claim 1, characterized in that, A waste liquid pump (6) is provided on the pipeline between the hydrolysis waste liquid pit (4) and the SNCR spray gun (7).

8. The zero-emission treatment system for hydrolysis waste liquid of the denitration system in a thermal power plant according to claim 7, wherein, The hydrolysis waste liquid zero-discharge treatment system of the denitration system of the thermal power plant further includes NO X monitoring device (10). The NO X monitoring device (10) is arranged at the flue gas outlet of the pulverized coal furnace (8) or the circulating fluidized bed boiler (9) and is used to monitor the content of nitrogen oxides in the flue gas discharged outside.

9. The zero-emission treatment system for hydrolysis waste liquid of the denitration system in a thermal power plant according to claim 8, wherein, The waste liquid pump (6) is configured to control the conveyance of a corresponding amount of waste liquid to the SNCR spray gun (7) based on the monitoring result of the monitoring device (10). X ​

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