CN111943424A - Desulfurization wastewater zero discharge system and method - Google Patents
Desulfurization wastewater zero discharge system and method Download PDFInfo
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Abstract
The invention provides a desulfurization wastewater zero discharge system and a method, wherein the discharge system comprises: a pretreatment unit and an evaporation unit; the pretreatment unit is used for reducing the hardness and impurity content of the wastewater to be treated to obtain pretreated wastewater; the evaporation unit comprises a heat source system, a flash evaporation system and a flue evaporation system, an air outlet of the heat source system is communicated with an air inlet of the flash evaporation system, a liquid inlet of the flash evaporation system is communicated with a liquid outlet of the pretreatment unit, an air outlet of the flash evaporation system is communicated with an inlet of the flue evaporation system, pretreated wastewater enters the flash evaporation system, contacts with a heat source provided by the heat source system to carry out countercurrent evaporation, and then secondary evaporation is carried out in the flue evaporation system. The system can utilize the waste heat in the active carbon analysis process, reduce the operation cost and the investment cost and ensure the stable operation of the system.
Description
Technical Field
The invention belongs to the technical field of wastewater treatment, and particularly relates to a desulfurization wastewater zero-discharge system and a desulfurization wastewater zero-discharge method.
Background
With the continuous improvement of the national environmental protection requirement, the control of the atmospheric pollutants represented by sulfur dioxide directly influences the quality of the atmospheric environment of China, and a series of desulfurization waste water can be generated in the current flue gas treatment and the resource recovery of rich gas. Because the desulfurization wastewater has high suspended matter content and fine particles, and contains two pollutants such as copper, zinc, fluoride, sulfide and the like, and heavy metal ions such as cadmium, mercury, chromium, lead, nickel and the like, the desulfurization wastewater has strong pollution to the environment.
The desulfurization wastewater treatment method mainly adopts a chemical precipitation method to remove pollutants in the desulfurization wastewater at present, but the method has high operation cost and limited removal rate of soluble salts such as chlorine salt and heavy metal ions such as selenium, suspended particulate matters, COD (chemical oxygen demand) and the like in effluent can not be stably discharged up to the standard, secondary pollution is easily caused, automatic control is difficult, and the operation result is not ideal. The treatment method has the problems of large floor area, high investment cost, complex process flow, large amount of chemical sludge generation, high energy consumption, incapability of removing chloride ions and the like, and the chloride ions have high corrosivity in a slightly acidic water environment, the treated wastewater cannot be recycled, and the application of the method is limited along with the improvement of environmental protection requirements.
The ultrafiltration reverse osmosis membrane method and the evaporation system are widely concerned by the proposal of the concept of zero discharge of wastewater. The concentrated wastewater produced by ultrafiltration reverse osmosis passes through an evaporation system to produce standard soft water external drainage, and the external drainage can be recycled, but the equipment investment cost is high, the consumed steam amount is large, the investment and operation cost is high, and the overall economy of a wastewater treatment system is poor; in order to achieve zero emission of waste water, flue evaporation is applied to engineering, waste water is sprayed into a pipeline between an air preheater and an electric dust collector through a nozzle, waste water is evaporated by utilizing waste heat of flue gas, particulate matters in the waste water are collected by a dust collector, when low-load operation is carried out, the spraying of the waste water causes the temperature of the flue gas to be reduced, when the temperature of the flue gas is insufficient, the waste water is not completely evaporated to dryness, liquid drops are enriched on the flue or the dust collector, corrosion and equipment failure are easily caused, and the operation risk of the whole system is increased.
At present, an effective desulfurization wastewater treatment mode which can reduce investment cost and comprehensively utilize waste heat does not exist.
Therefore, there is a need to provide an improved solution to the above-mentioned deficiencies of the prior art.
Disclosure of Invention
The invention aims to provide a desulfurization wastewater zero-discharge system and a desulfurization wastewater zero-discharge method, which at least solve the problems of high investment and operation cost and high system operation risk of the conventional desulfurization wastewater.
In order to achieve the above purpose, the invention provides the following technical scheme:
a desulfurization waste water zero discharge system, the discharge system comprising: a pretreatment unit and an evaporation unit;
the pretreatment unit is used for reducing the hardness and impurity content of the wastewater to be treated to obtain pretreated wastewater;
the evaporation unit comprises a heat source system, a flash evaporation system and a flue evaporation system, an air outlet of the heat source system is communicated with an air inlet of the flash evaporation system, a liquid inlet of the flash evaporation system is communicated with a liquid outlet of the pretreatment unit, an air outlet of the flash evaporation system is communicated with an inlet of the flue evaporation system, pretreated wastewater enters the flash evaporation system, contacts with a heat source provided by the heat source system to carry out countercurrent evaporation, and then secondary evaporation is carried out in the flue evaporation system.
In the desulfurization wastewater zero discharge system, preferably, the pretreatment unit comprises a PH back-adjusting tank, a flocculation reaction tank and a clarification tank, an outlet of the PH back-adjusting tank is communicated with an inlet of the flocculation reaction tank, and an outlet of the flocculation reaction tank is communicated with an inlet of the clarification tank;
preferably, the pretreatment unit further comprises a buffer tank, and the buffer tank is communicated with the PH callback tank;
preferably, the raw materials added into the flocculation reaction tank comprise sodium carbonate;
preferably, the raw materials added into the flocculation reaction tank also comprise a flocculating agent and a coagulant aid;
still more preferably, the flocculating agent and coagulant aid are polyaluminium chloride and polyacrylamide, respectively.
In the desulfurization wastewater zero discharge system, preferably, the pretreatment unit further comprises a plate-and-frame filter press, and an inlet of the plate-and-frame filter press is communicated with the bottom of the clarification tank and is used for filter pressing sludge at the bottom of the clarification tank;
preferably, the liquid outlet of the plate-and-frame filter press is communicated with the inlet of the clarification tank and used for circularly precipitating the clear liquid again.
In the desulfurization wastewater zero-discharge system, preferably, the heat source system comprises an analysis tower and a hot blast stove, an air outlet of the hot blast stove is communicated with an inlet of the analysis tower and is used for introducing hot air into the analysis tower, and an air outlet of the heat source in the analysis tower is communicated with an air inlet of the flash evaporation system;
preferably, an induced draft fan is arranged on a pipeline between the desorption tower and the flash evaporation system and used for introducing a heat source subjected to heat exchange in the desorption tower into the flash evaporation system.
In the desulfurization wastewater zero discharge system, preferably, the flash evaporation system comprises a flash evaporator, and an atomizing nozzle is arranged in the flash evaporator;
preferably, a plurality of atomizing nozzles are uniformly distributed on the cross section of the flash evaporator, and the distance between two adjacent atomizing nozzles is 0.15-0.2 m;
still preferably, the atomizing nozzle is located at a distance 1/4-1/3 from the liquid inlet of the flash evaporator.
In the desulfurization wastewater zero discharge system, preferably, a wastewater delivery pump is arranged on a pipeline between the clarification tank and the flash evaporator, and the wastewater delivery pump delivers wastewater into the atomizing nozzle through an atomizing pipeline;
preferably, the pretreatment unit further comprises a compressed air tank, the compressed air tank is communicated with the atomizing nozzle, and compressed air inside the compressed air tank and wastewater are mixed in an atomizing pipeline and then are conveyed into the atomizing nozzle.
In the desulfurization wastewater zero discharge system, preferably, the flue evaporation system comprises a sintering flue, an inlet of the sintering flue is communicated with an air outlet of the flash evaporator, and flue gas discharged by the flash evaporator enters the sintering flue and is secondarily evaporated by using waste heat of the sintering flue gas.
In the desulfurization wastewater zero discharge system, preferably, the wastewater zero discharge system further comprises a gas-solid separation device, and the gas-solid separation device is communicated with the flue evaporation system;
preferably, the gas-solid separation device is a dust remover;
preferably, the wastewater to be treated is wastewater discharged after pre-washing the rich gas discharged from the activated carbon flue gas desulfurization and denitrification desorption tower.
A desulfurization wastewater zero-discharge method comprises the following steps:
carrying out flocculation and clarification on the desulfurization and denitrification wastewater after the PH is adjusted, wherein the clarified supernatant is the pretreated wastewater;
the pretreated wastewater and a heat source from the desorption tower are mixed in a countercurrent mode to carry out countercurrent evaporation, gas subjected to countercurrent evaporation is secondarily evaporated through sintering flue gas in a sintering flue to obtain a gas-solid mixture, the gas-solid mixture is subjected to gas-solid separation, and the flue gas subjected to gas-solid separation is introduced into a flue gas desulfurization system.
In the desulfurization wastewater zero-discharge method, preferably, the pretreated wastewater is mixed with compressed air to form atomized liquid drops, and the atomized liquid drops are in countercurrent contact with a heat source to perform countercurrent evaporation;
preferably, the particle size of the atomized droplets is 80-100 μm;
preferably, the method is performed using the above-described drainage system.
Compared with the closest prior art, the technical scheme provided by the invention has the following excellent effects:
compared with the existing desulfurization wastewater treatment technology, the desulfurization wastewater zero-discharge system provided by the invention evaporates wastewater by adopting the waste heat analyzed by the heating section in the analyzing tower, realizes desulfurization wastewater zero discharge, effectively utilizes the waste heat in the active carbon analyzing process, reduces the use amount of steam and electricity, reduces the operation cost, and realizes effective recycling of available resources.
After the wastewater is pretreated, the requirement on the nozzle can be reduced by removing most suspended matters and hardness, and the blockage rate of the nozzle is reduced.
The waste water evaporation system of this system, equipment is small in quantity, and inner structure is simple, and the mixed back flue gas temperature is high simultaneously, and the system does not scale deposit, not block up, has reduced area, has reduced the investment cost, has reduced the maintenance cost of later stage system simultaneously.
The use of the two-stage evaporation system can effectively improve the processing load of the system and ensure the continuous and stable operation of the system.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. Wherein:
fig. 1 is a schematic structural diagram of a desulfurization wastewater zero-discharge system according to an embodiment of the present invention.
In the figure: 1. a PH call-back box; 2. a flocculation reaction tank; 3. a clarification tank; 4. a plate-and-frame filter press; 5. a wastewater delivery pump; 6. a flash evaporator; 7. an atomizing nozzle; 8. a resolution tower; 9. a hot blast stove; 10. an induced draft fan; 11. sintering the flue; 12. a dust remover; 13. a compressed air tank; 14. a buffer tank; 15. an atomizing pipe.
Detailed Description
The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings. It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.
In the description of the present invention, the terms "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, which are for convenience of description of the present invention only and do not require that the present invention must be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention. The terms "connected" and "connected" used herein should be interpreted broadly, and may include, for example, a fixed connection or a detachable connection; they may be directly connected or indirectly connected through intermediate members, and specific meanings of the above terms will be understood by those skilled in the art as appropriate.
According to the invention, after the desulfurization wastewater is pretreated, the wastewater is preheated and evaporated by the high-temperature flue gas subjected to heat exchange in the desorption tower, and the preheated and evaporated wastewater enters the sintering flue along with the high-temperature flue gas, so that zero discharge of the desulfurization wastewater is finally realized, the desulfurization waste heat is effectively utilized, the use amount of steam and electricity is reduced, the investment cost and the operation cost are reduced, and the effective recycling of available resources is realized.
At present, the most advanced activated carbon flue gas desulfurization and denitration process in the world is realized, the flue gas is adsorbed and purified by activated carbon and then is discharged after reaching the standard, and the activated carbon adsorbing pollutants can be recycled after being analyzed by an analysis tower. The active carbon with adsorbed pollutant enters an analytic tower which mainly comprises a heating section and a cooling section and consists of a multi-tube heat exchanger, and the analytic tower is used for removing SO in the active carbon2And adsorbed other impurities. The activated carbon is heated to 390-450 ℃ in the heating section of the desorption tower, and adsorbed pollutants are released or decomposed, so that the purpose of activated carbon regeneration is achieved, and the adjustment of the heating section is realized by changing the temperature of a heating air inlet entering a heat exchanger. The temperature of the heated air is as high as about 500 ℃, the activated carbon in the desorption tower is subjected to heat exchange to ensure that the activated carbon is completely desorbed, the temperature of hot gas entering the desorption tower is reduced to 280-320 ℃ after the heat exchange, the hot gas is discharged through a flue, and the part of flue gas can be subjected to waste heat utilization.
In order to obtain salt with high purity, rich gas (gas with high sulfur dioxide content) discharged from the desorption tower is pre-washed by process water, and then a certain amount of wastewater is discharged periodically, so that the quality of the rich gas is ensured, and the precision of salt preparation from the rich gas in the desorption tower is improved. The wastewater discharged periodically is the activated coke desulfurization and denitrification wastewater to be treated in the invention.
The quality of the wastewater is shown in table 1 below.
TABLE 1 wastewater parameters
As shown in fig. 1, according to an embodiment of the present invention, there is provided a desulfurization waste water zero discharge system, including: a pretreatment unit and an evaporation unit.
The pretreatment unit comprises a PH back-adjusting box 1, a flocculation reaction tank 2 and a clarification tank 3, wherein an outlet of the PH back-adjusting box 1 is communicated with an inlet of the flocculation reaction tank 2, an outlet of the flocculation reaction tank 2 is communicated with an inlet of the clarification tank 3, and the pretreatment unit is used for reducing the hardness and the organic impurity content of the desulfurization wastewater to obtain pretreated wastewater. The pretreatment unit primarily removes harmful F-Ions and a large amount of suspended matters reduce the total hardness of the original wastewater.
The evaporation unit comprises a heat source system, a flash evaporation system and a flue evaporation system, an air outlet of the heat source system is communicated with an air inlet of the flash evaporation system, a liquid inlet of the flash evaporation system is also communicated with a liquid outlet of the clarification tank 3, an air outlet of the flash evaporation system is communicated with an inlet of the flue evaporation system, pretreated wastewater enters the flash evaporation system, is contacted with a high-temperature heat source provided by the heat source system to carry out countercurrent evaporation, and is subjected to secondary evaporation in the flue evaporation system.
The PH adjusting box 1 is used for adjusting the PH value of the wastewater, limestone slurry is added into the PH adjusting box 1 to adjust the PH value of the wastewater to 9-10, and after the PH adjustment of the wastewater, part of acid radicals and halogen ions are neutralized into corresponding inorganic salt on one hand, and part of light and heavy metal ions react to generate hydroxide so as to be precipitated and separated out on the other hand. Meanwhile, the alkalescent atmosphere after the neutralization of the wastewater is favorable for further complexing and crystallizing and precipitating heavy metal ions.
In the specific embodiment of the invention, the raw materials added in the flocculation reaction tank 2 comprise sodium carbonate; preferably, the raw materials added into the flocculation reaction tank 2 also comprise a flocculating agent and a coagulant aid; still more preferably, the flocculating and flocculating aid is polyaluminium chloride and polyacrylamide, respectively. Most suspended matters and hardness in the wastewater can be removed after flocculation reaction and clarification treatment, the burden on a subsequent evaporation system is reduced, and the risk of blockage is reduced. The primary flocculation reaction tank 2 and the clarification tank 3 are adopted, so that the investment cost and the later-stage dosing cost in a running room can be reduced.
The wastewater in the PH readjustment box 1 automatically flows to a flocculation reaction tank 2 after completely reacting, and is combined with calcium and magnesium ions in water into calcium carbonate and magnesium carbonate by adding sodium carbonate; PAC (polyaluminium chloride) and PAM (polyacrylamide) flocculating agents and coagulant aids are also added into the flocculation reaction tank 2 to coagulate small particles such as calcium carbonate, magnesium carbonate and the like into large particles. The wastewater in the flocculation reaction tank 2 enters a clarification tank 3, and is subjected to mud-water separation and coagulating sedimentation by the clarification tank 3, so that a part of organic matters can be removed. Clear water clarified by the clarification tank 3 enters the evaporation unit.
In the specific embodiment of the invention, the pretreatment unit further comprises a plate-and-frame filter press 4, the bottom of the clarification tank 3 is communicated with the inlet of the plate-and-frame filter press 4 and is used for filter pressing the sludge at the bottom of the clarification tank 3; sludge at the bottom of the clarification tank 3 is pressed out of a sludge cake through a plate-and-frame filter press 4.
Preferably, the liquid outlet of the plate-and-frame filter press 4 is communicated with the inlet of the clarification tank 3, so that the liquid in the plate-and-frame filter press 4 is further precipitated to form a circulating process.
Further preferably, the pretreatment unit further comprises a buffer tank 14, and the buffer tank 14 is communicated with the PH back-off box 1. The wastewater is discharged discontinuously, the water quality fluctuation is large, and the buffer tank 14 can be used for adjusting the water quality, stabilizing the water quality and the water quantity and facilitating the quantitative discharge of the wastewater into the PH regulation box 1.
The purpose of the pretreatment unit is to ensure that the nozzle is not easy to block when the wastewater passes through the nozzle of the evaporation unit, thereby reducing the maintenance amount of the system.
The wastewater after passing through the pretreatment unit can reach the water quality standard in the following table 2:
TABLE 2 parameters of pretreated wastewater
| Serial number | Item | Index of water discharge |
| 1 | COD(mg/L) | 800-1000 |
| 2 | Total hardness (mg/L) | 100-150 |
| 3 | Chloride ion (mg/L) | 20000-40000 |
| 4 | Ammonia nitrogen (mg/L) | 300-400 |
| 5 | Turbidity (NTU) | 100-200 |
| 6 | F- | 30-40 |
| 7 | pH value | 7-8.5 |
In the specific embodiment of the invention, the heat source system comprises a desorption tower 8 (i.e. an activated carbon desorption tower in the activated carbon flue gas desulfurization and denitrification process) and a hot blast stove 9, an air outlet of the hot blast stove 9 is communicated with an inlet of the desorption tower 8 and is used for introducing hot air into the desorption tower 8, and an air outlet of the heat source of the desorption tower 8 is communicated with an air inlet of the flash evaporation system. The hot air after heat exchange in the desorption tower 8 enters a flash evaporation system, and the heat source after heat exchange is the hot air with the temperature of 280-320 ℃ for reutilization.
Preferably, an induced draft fan 10 is arranged on a pipeline between the desorption tower 8 and the flash evaporation system, and is used for introducing a heat source subjected to heat exchange in the desorption tower 8 into the flash evaporation system.
In the specific embodiment of the invention, the flash evaporation system comprises a flash evaporator 6, and an atomizing nozzle 7 is arranged in the flash evaporator 6; the atomizing nozzle 7 is arranged at a position which is far away from the liquid inlet 1/4-1/3 of the flash evaporator 6, so that the pretreated wastewater is sprayed out from the atomizing nozzle 7 to obtain the optimal contact time and space with a heat source, and the evaporation efficiency is improved; preferably, a plurality of atomizing nozzles 7 are uniformly distributed on the cross section of the flash evaporator 6, and the distance between two adjacent atomizing nozzles 7 is 0.15-0.2 m; still preferably, the atomizing nozzle 7 atomizes the droplets to form droplets having a diameter of 80 to 100. mu.m.
In the embodiment of the present invention, preferably, the pretreatment unit further includes a compressed air tank 13, the compressed air tank 13 is communicated with the atomizing nozzle 7, and the compressed air inside the compressed air tank 13 and the wastewater are mixed in the atomizing pipe 15 and then are conveyed into the atomizing nozzle 7. After the pretreated wastewater is mixed with compressed air, atomized liquid drops are formed and then are in countercurrent contact with a heat source for countercurrent evaporation.
In the embodiment of the invention, a waste water delivery pump 5 is arranged on a pipeline between the clarification tank 3 and the flash evaporator 6, and the waste water delivery pump 5 delivers waste water into the atomizing nozzle 7 through an atomizing pipeline 15.
The waste water enters a pipeline through a waste water delivery pump 5, and enters an atomizing nozzle 7 after being mixed with compressed air, the number of the atomizing nozzles 7 depends on the cross section area of a mixer (namely a flash evaporator 6), and the grain diameter of atomized liquid drops is 80-100 mu m. The fog drops can be rapidly heated and evaporated to dryness, and meanwhile, the fog drops are prevented from being enriched on the inner wall of the flash evaporation mixer, so that the flash evaporation mixer is prevented from being corroded and scaled.
The temperature of the mixed flue gas at the outlet of the flash evaporator 6 is slightly changed according to the difference of water inlet amount, and the temperature of the flue gas is higher than the acid dew point, so that the corrosion of equipment can not be caused.
In the specific embodiment of the invention, the flue evaporation system comprises a sintering flue 11, the flue evaporation system comprises the sintering flue 11, an inlet of the sintering flue 11 is communicated with an air outlet of the flash evaporator 6, and flue gas discharged by the flash evaporator 6 enters the sintering flue 11 to be secondarily evaporated by using the waste heat of the sintering flue gas from the sintering machine. The sintering flue 11 contains high-temperature sintering flue gas. The temperature of the sintering flue gas is 150-160 ℃.
In the specific embodiment of the invention, the wastewater discharge system also comprises a gas-solid separation device which is communicated with the flue evaporation system; preferably, the gas-solid separation device is a dust separator 12. The sintering flue gas in the sintering flue 11 is mixed with the water-solid-gas mixture from the flash evaporator 6 to realize heat exchange, and then enters the dust remover 12 to perform gas-solid separation, and the separated gas enters the sintering flue gas desulfurization and denitrification system.
The heat source and the atomized wastewater are mixed in a countercurrent manner, the contact area is increased, the evaporation area is increased, the atomized wastewater and the heat source with the temperature of 280 and 320 ℃ led out from the desorption tower 8 are fully mixed in the flash evaporator 6, and the atomized desulfurization wastewater is evaporated into steam and solid particles by the heat source. Because the amount of the heat source generated by the desorption tower 8 is limited, the waste water is not completely evaporated, the waste water directly enters the sintering flue 11 after passing through the flash evaporator 6 to be secondarily evaporated by using the waste heat of the sintering flue gas, suspended matters and related salt-containing substances in the waste water are evaporated to dryness after the secondary evaporation to form solid particles, and the solid particles enter the dust remover 12 along with the flue gas to complete gas-solid separation. The use of the two-stage evaporation system can effectively improve the processing load of the system and ensure the continuous and stable operation of the system.
In order to further understand the desulfurization wastewater zero-discharge system, the invention also provides a desulfurization wastewater zero-discharge method, which comprises the following steps:
the method comprises the following steps of firstly discharging the activated carbon desulfurization wastewater into a buffer tank 14, discharging the wastewater in the buffer tank 14 to a PH (potential of Hydrogen) callback box 1, neutralizing and precipitating part of metal ions under the regulation action of limestone slurry, and keeping the weakly alkaline atmosphere; after the PH is adjusted, the supernatant is the pretreated wastewater, such as a flocculation reaction tank 2 and a clarification tank 3, and at the moment, large particles and a part of organic matters are filtered and precipitated, so that the hardness of the wastewater is reduced. And the slurry at the bottom of the clarification tank 3 enters a plate-and-frame filter press 4 to filter out mud cakes by pressing, and meanwhile, the clear liquid of the plate-and-frame filter press 4 enters the clarification tank 3 again to precipitate and filter solid particles.
The pretreated wastewater is conveyed by a wastewater conveying pump 5, mixed with compressed air and then enters a nozzle of a flash evaporator 6, liquid drops are atomized by the nozzle and then sprayed out, the particle size of the atomized liquid drops is 80-100 mu m, the atomized liquid drops and an air heat source after heat exchange from an analytical tower 8 are mixed in a countercurrent mode to carry out countercurrent evaporation, gas after countercurrent evaporation is subjected to secondary evaporation in a sintering flue 11 to obtain a gas mixture, the gas mixture enters a dust remover 12 for gas-solid separation, the flue gas after gas-solid separation is introduced into a flue gas desulfurization system, and the flue gas after desulfurization can be discharged from a chimney.
In conclusion, the system adopts the waste heat analyzed by the heating section in the analyzing tower to evaporate the waste water, so that zero emission of the desulfurization waste water is realized, the desulfurization waste heat is effectively utilized, the use amount of steam and electricity is reduced, the operation cost is reduced, and effective recycling of available resources is realized.
After the wastewater is pretreated, the requirement on the nozzle can be reduced by removing most suspended matters and hardness, and the blockage rate of the nozzle is reduced.
The waste water evaporation system of this system, equipment is small in quantity, and inner structure is simple, and the mixed back flue gas temperature is high simultaneously, and the system does not scale deposit, not block up, has reduced area, has reduced the investment cost, has reduced the maintenance cost of later stage system simultaneously.
The use of the two-stage evaporation system can effectively improve the processing load of the system and ensure the continuous and stable operation of the system.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A desulfurization waste water zero discharge system, characterized in that the discharge system comprises: a pretreatment unit and an evaporation unit;
the pretreatment unit is used for reducing the hardness and impurity content of the wastewater to be treated to obtain pretreated wastewater;
the evaporation unit comprises a heat source system, a flash evaporation system and a flue evaporation system, an air outlet of the heat source system is communicated with an air inlet of the flash evaporation system, a liquid inlet of the flash evaporation system is communicated with a liquid outlet of the pretreatment unit, an air outlet of the flash evaporation system is communicated with an inlet of the flue evaporation system, pretreated wastewater enters the flash evaporation system, contacts with a heat source provided by the heat source system to carry out countercurrent evaporation, and then secondary evaporation is carried out in the flue evaporation system.
2. The desulfurization waste water zero discharge system of claim 1,
the pretreatment unit comprises a PH (potential of hydrogen) back-adjusting box, a flocculation reaction tank and a clarification tank, wherein an outlet of the PH back-adjusting box is communicated with an inlet of the flocculation reaction tank, and an outlet of the flocculation reaction tank is communicated with an inlet of the clarification tank;
preferably, the pretreatment unit further comprises a buffer tank, and the buffer tank is communicated with the PH callback tank;
preferably, the raw materials added into the flocculation reaction tank comprise sodium carbonate;
preferably, the raw materials added into the flocculation reaction tank also comprise a flocculating agent and a coagulant aid;
still more preferably, the flocculating agent and coagulant aid are polyaluminium chloride and polyacrylamide, respectively.
3. The desulfurization wastewater zero-discharge system of claim 2, wherein the pretreatment unit further comprises a plate-and-frame filter press, and an inlet of the plate-and-frame filter press is communicated with the bottom of the clarification tank and is used for filter pressing sludge at the bottom of the clarification tank;
preferably, the liquid outlet of the plate-and-frame filter press is communicated with the inlet of the clarification tank and used for circularly precipitating the clear liquid again.
4. The desulfurization wastewater zero-emission system of claim 1, wherein the heat source system comprises a desorption tower and a hot-blast stove, an air outlet of the hot-blast stove is communicated with an inlet of the desorption tower and is used for introducing hot air into the desorption tower, and an air outlet of the heat source in the desorption tower is communicated with an air inlet of the flash evaporation system;
preferably, an induced draft fan is arranged on a pipeline between the desorption tower and the flash evaporation system and used for introducing a heat source subjected to heat exchange in the desorption tower into the flash evaporation system.
5. The desulfurization waste water zero discharge system of claim 2, wherein the flash evaporation system comprises a flash evaporator, and an atomizing nozzle is arranged in the flash evaporator;
preferably, a plurality of atomizing nozzles are uniformly distributed on the cross section of the flash evaporator, and the distance between two adjacent atomizing nozzles is 0.15-0.2 m;
still preferably, the atomizing nozzle is located at a distance 1/4-1/3 from the liquid inlet of the flash evaporator.
6. The desulfurization waste water zero discharge system of claim 5, wherein a waste water delivery pump is arranged on a pipeline between the clarification tank and the flash evaporator, and the waste water delivery pump delivers waste water into the atomizing nozzle through an atomizing pipeline;
preferably, the pretreatment unit further comprises a compressed air tank, the compressed air tank is communicated with the atomizing nozzle, and compressed air inside the compressed air tank and wastewater are mixed in an atomizing pipeline and then are conveyed into the atomizing nozzle.
7. The desulfurization wastewater zero-emission system of claim 6, wherein the flue evaporation system comprises a sintering flue, an inlet of the sintering flue is communicated with an air outlet of the flash evaporator, and flue gas discharged by the flash evaporator enters the sintering flue to be secondarily evaporated by using waste heat of the sintering flue gas.
8. The desulfurization wastewater zero-discharge system of any one of claims 1 to 7, further comprising a gas-solid separation device, wherein the gas-solid separation device is communicated with the flue evaporation system;
preferably, the gas-solid separation device is a dust remover;
preferably, the wastewater to be treated is wastewater discharged after pre-washing the rich gas discharged from the activated carbon flue gas desulfurization and denitrification desorption tower.
9. A desulfurization wastewater zero discharge method is characterized by comprising the following steps:
carrying out flocculation and clarification on the desulfurization and denitrification wastewater after the PH is adjusted, wherein the clarified supernatant is the pretreated wastewater;
the pretreated wastewater and a heat source from the desorption tower are mixed in a countercurrent mode to carry out countercurrent evaporation, gas subjected to countercurrent evaporation is secondarily evaporated through sintering flue gas in a sintering flue to obtain a gas-solid mixture, the gas-solid mixture is subjected to gas-solid separation, and the flue gas subjected to gas-solid separation is introduced into a flue gas desulfurization system.
10. The desulfurization wastewater zero-discharge method according to claim 9, wherein the pretreated wastewater is mixed with compressed air to form atomized liquid droplets, and the atomized liquid droplets are subjected to countercurrent contact with a heat source to perform countercurrent evaporation;
preferably, the particle size of the atomized droplets is 80-100 μm;
preferably, the method is performed using the discharge system of any one of claims 1 to 8.
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