Coal chemical wastewater treatment system and treatment method thereofTechnical Field
The invention relates to a coal chemical wastewater treatment system and a treatment method thereof, belonging to the technical field of wastewater treatment.
Background
Because of the characteristics of rich coal resources and complete coal types in China, the coal chemical industry in China has unique development advantages, and develops rapidly under the support of national policies, however, the wastewater discharged by the coal chemical industry mainly comprises high-concentration gas washing wastewater, contains a large amount of toxic and harmful substances such as phenol, cyanogen, oil, ammonia nitrogen and the like, the COD in the comprehensive wastewater is generally about 5000mg/L, the ammonia nitrogen is 200-500 mg/L, and the organic pollutants contained in the wastewater comprise phenols, polycyclic aromatic compounds, heterocyclic compounds containing nitrogen, oxygen and sulfur and the like, so that the wastewater is typical industrial wastewater containing organic compounds difficult to degrade. The easily degradable organic in the wastewater is mainly phenolic compounds and benzene compounds; arsenic, naphthalene, furan and amidinzole belong to degradable organic matters; the organic matter difficult to degrade mainly comprises pyridine, carbazole, biphenyl, terphenyl and the like. The high-pollution coal chemical wastewater also promotes the rapid development of the wastewater treatment field, and the technology for treating the coal chemical wastewater at home at present mainly comprises a biochemical method, a wet oxidation method and the like, wherein the biochemical method has poor treatment effect on some refractory organic matters such as quinolines, indoles, pyridines, carbazoles and the like, while the wet oxidation method has obvious treatment effect on COD (chemical oxygen demand), but has high treatment cost, so that in order to fully exert the advantages of the wet oxidation technology on the COD treatment, new technology is urgently needed to be developed to reduce the wet oxidation treatment cost.
Disclosure of Invention
In order to make up for the defects of the prior art, the invention provides a coal chemical wastewater treatment system and a treatment method thereof, which are mainly used for wastewater treatment. The treatment system consists of two parts, namely wastewater pre-concentration and wastewater concentration crystallization. The wastewater after passing through the triple-effect evaporator is pre-concentrated, so that the oxidation treatment efficiency is improved, and the treatment cost is reduced. The high-salt wastewater subjected to flash evaporation passes through a pre-concentrated horizontal tube evaporator and a two-effect vertical tube evaporator for evaporation and crystallization, so that zero emission is realized, and the pollution to the environment is reduced.
The invention adopts the following technical scheme: the utility model provides a coal industry effluent disposal system, it includes wet-type oxidizer, it still includes waste water preconcentration subsystem and crystallization subsystem, waste water preconcentration subsystem includes flash tank, low temperature multiple effect evaporator, condenser and vacuum pump, the charge pump that supplies coal industry waste water is through the tube side import connection of pipeline with the condenser, the tube side export of condenser is through the each import shower of low temperature multiple effect evaporator side by side connection, the second steam pipe of low temperature multiple effect evaporator former effect is connected next effective steam chamber, each effect export of low temperature multiple effect evaporator adopts the pipeline to connect wet-type oxidizer and flash tank in proper order through the delivery pump, the upper portion of flash tank is through the steam inlet of steam pipe connection low temperature multiple effect evaporator, the shell side export of condenser is through pipeline connection condensate pump and vacuum pump, the comdenstion water in the steam chamber is also through pipeline connection condensate pump; the crystallization subsystem comprises a horizontal tube evaporator, a second effect vertical tube evaporator, a first effect vertical tube evaporator and a centrifugal crystallization device, wherein a medium-pressure steam pipeline is connected with a shell side steam inlet of the first effect vertical tube evaporator, a shell side steam outlet of the first effect vertical tube evaporator and a secondary steam pipeline at the top of the first effect vertical tube evaporator are connected with a shell side steam inlet of the second effect vertical tube evaporator, and a shell side steam outlet of the second effect vertical tube evaporator and a secondary steam pipeline at the top of the second effect vertical tube evaporator are connected with a tube side steam inlet of the horizontal tube evaporator; the lower part of the flash tank is connected with a shell side inlet of a horizontal tube evaporator through a high-salt waste water pipeline, and a shell side outlet of the horizontal tube evaporator is sequentially connected with a tube side of a second effect standpipe evaporator, a tube side of a first effect standpipe evaporator and a centrifugal crystallization device in series by adopting a pipeline; the tube side steam outlet and the shell side steam outlet of the horizontal tube evaporator are connected to the shell side inlet of the condenser through a tube; and the horizontal tube evaporator tube side condensed water, the second effect vertical tube evaporator and the shell side condensed water of the first effect vertical tube evaporator are connected with a condensed water tank.
The treatment method of the coal chemical wastewater comprises the following steps:
(a) The coal chemical wastewater is pumped into a tube side in a condenser by a feed pump, steam is supplied to a shell side of the condenser with vacuum degree by the end effect of a low-temperature multi-effect evaporator to preheat the wastewater, and the temperature of the wastewater is increased from 20 ℃ to 25 ℃ to 40 ℃ to 50 ℃;
(b) Spraying preheated coal chemical wastewater into each effect evaporator through a spray pipe in the low-temperature multi-effect evaporator to heat and evaporate, taking secondary steam generated in the former effect evaporator as a heat source of the next effect evaporator to finish pre-concentration, increasing the salinity of the wastewater from 1% -3% to 5% -6%, and conveying the pre-concentrated wastewater to a wet oxidation reactor through a conveying pump; the COD of the wastewater at the outlet of the wet oxidation reactor is reduced to 1500-2000mg/L, high-temperature high-pressure wastewater at 250-300 ℃ is flashed in a flash tank, low-temperature steam at 55-65 ℃ generated by flash evaporation is used as a heating source of a low-temperature multi-effect evaporator, and the salinity of the flashed wastewater is increased from 5-6% to 7-8%;
(c) The medium-pressure steam is used as a heat source of the first-effect vertical pipe evaporator, the second-effect vertical pipe evaporator and the horizontal pipe evaporator, the secondary steam generated by the first-effect vertical pipe evaporator is also used as a heat source of the second-effect vertical pipe evaporator, and the secondary steam generated by the second-effect vertical pipe evaporator is also used as a heat source of the horizontal pipe evaporator;
(d) Concentrating the flashed coal chemical wastewater in a horizontal tube evaporator again, wherein the salinity of the wastewater is improved from 7% -8% to 8% -9%, heating and evaporating the concentrated wastewater in a series-connected two-effect vertical tube evaporator to generate saturated solution, and completing crystallization in a centrifugal crystallization device to realize zero discharge of the wastewater;
(e) And recovering the steam condensate in the low-temperature multi-effect evaporator, the condenser, the horizontal pipe evaporator, the second effect vertical pipe evaporator and the first effect vertical pipe evaporator into a condensate water tank.
The beneficial effects of the invention are as follows: the coal chemical industry wastewater treatment system comprises a wet-type oxidizer, a wastewater preconcentration subsystem and a crystallization subsystem. Before the coal chemical wastewater enters the wet oxidation reactor, the coal chemical wastewater is heated and evaporated in a low-temperature multi-effect evaporator to be pre-concentrated, so that the amount of the coal chemical wastewater entering the wet oxidation reactor is greatly reduced, the energy consumption of the wet oxidation reactor is reduced, and the cost for treating the wastewater by the wet oxidation reaction is obviously reduced. The steam generated by flash evaporation of the high-temperature high-pressure wastewater at the outlet of the wet oxidation reactor is used as a heat source of the low-temperature multi-effect evaporator, so that the concentration of the coal chemical wastewater can be completed without an external heat source. In the evaporation and crystallization process of the high-salt wastewater after wet oxidation treatment, the low-temperature secondary steam of the final-effect standpipe evaporator in the horizontal-standpipe evaporation system is used as a heat source of the horizontal-tube evaporator to concentrate the wastewater, so that the energy consumption of zero emission of the wastewater can be obviously reduced.
Drawings
FIG. 1 is a diagram of a coal chemical wastewater treatment system.
In the figure: 1. the device comprises a wet oxidation reactor 2, a flash tank 3, a low-temperature multi-effect evaporator 3a, a spray pipe 3b, a steam cavity 4, a condenser 5, a vacuum pump 6, a feed pump 7, a horizontal pipe concentration evaporator 8, a second-effect vertical pipe evaporator 9, a first-effect vertical pipe evaporator 10, a delivery pump 11, a condensate pump 12, a centrifugal crystallization device 13 and a condensate water tank.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments.
FIG. 1 shows a diagram of a coal chemical wastewater treatment system. In the figure, the coal chemical industry wastewater treatment system comprises a wet type oxidizer 1, a wastewater preconcentration subsystem and a crystallization subsystem. The wastewater preconcentration subsystem comprises a flash tank 2, a low-temperature multi-effect evaporator 3, a condenser 4 and a vacuum pump 5, a feed pump 6 for feeding wastewater in coal chemical industry is connected with a tube side inlet of the condenser 4 through a pipeline, a tube side outlet of the condenser 4 is connected with each effect inlet spray pipe 3a of the low-temperature multi-effect evaporator 3 in parallel through a pipeline, and a secondary steam pipeline of the previous effect of the low-temperature multi-effect evaporator 3 is connected with a steam cavity 3b of the next effect. The low-temperature multi-effect evaporator 3 is sequentially connected with the wet-type oxidizer 1 and the flash tank 2 through a conveying pump 10 by adopting pipelines at each effect outlet, the upper part of the flash tank 2 is connected with a steam inlet of the low-temperature multi-effect evaporator 3 through a steam pipeline, a steam outlet of the low-temperature multi-effect evaporator 3 is connected with a shell side inlet of a condenser 4, a shell side outlet of the condenser 4 is connected with a condensate pump 11 and a vacuum pump 5 through pipelines, and condensate water in a steam cavity 3b is also connected with the condensate pump 11 through a pipeline. The crystallization subsystem comprises a horizontal tube evaporator 7, a second effect vertical tube evaporator 8, a first effect vertical tube evaporator 9 and a centrifugal crystallization device 12, wherein a medium-pressure steam pipeline is connected with a shell side steam inlet of the first effect vertical tube evaporator 9, a shell side steam outlet of the first effect vertical tube evaporator 9 and a secondary steam pipeline at the top of the first effect vertical tube evaporator 9 are connected with a shell side steam inlet of the second effect vertical tube evaporator 8, and a shell side steam outlet of the second effect vertical tube evaporator 8 and a secondary steam pipeline at the top of the second effect vertical tube evaporator 8 are connected with a tube side steam inlet of the horizontal tube evaporator 7. The lower part of the flash tank 2 is connected with the shell side inlet of the horizontal tube evaporator 7 through a high-salt waste water pipeline, and the shell side outlet of the horizontal tube evaporator 7 is sequentially connected with the tube side of the second effect standpipe evaporator 8, the tube side of the first effect standpipe evaporator 9 and the centrifugal crystallization device 12 in series by adopting a pipeline. The tube side steam outlet and the shell side steam outlet of the horizontal tube evaporator 7 are connected to the shell side inlet of the condenser 4 via tubes. The horizontal tube evaporator 7 tube side condensed water, the second effect vertical tube evaporator 8 and the first effect vertical tube evaporator 9 shell side condensed water and the condensed water pump 11 are connected with the condensed water tank 13.
The method for treating the coal chemical wastewater comprises the following steps:
(a) The coal chemical wastewater is sent into a tube side in a condenser 4 by a feed pump 6, steam preheating wastewater is supplied to a shell side of the condenser 4 with vacuum degree by the end effect of a low-temperature multi-effect evaporator 3, and the temperature of the wastewater is increased from 20 ℃ to 25 ℃ to 40 ℃ to 50 ℃;
(b) The preheated coal chemical wastewater is sprayed into each effect evaporator through a spray pipe 3a in the low-temperature multi-effect evaporator 3 to be heated and evaporated, the secondary steam generated in the former effect evaporator is also used as a heat source of the next effect evaporator to finish pre-concentration, the salinity of the wastewater is increased from 1% -3% to 5% -6%, and the pre-concentrated wastewater is conveyed to the wet oxidation reactor 1 through a conveying pump 10; the COD of the wastewater at the outlet of the wet oxidation reactor 1 is reduced to 1500-2000mg/L, high-temperature high-pressure wastewater at 250-300 ℃ is flashed in a flash tank 2, low-temperature steam at 55-65 ℃ generated by flash evaporation is used as a heating source of a low-temperature multi-effect evaporator 3, and the salinity of the flashed wastewater is increased from 5-6% to 7-8%;
(c) The medium-pressure steam is used as a heat source of the first-effect vertical pipe evaporator 9, the second-effect vertical pipe evaporator 8 and the horizontal pipe evaporator 7, the secondary steam generated by the first-effect vertical pipe evaporator 9 is also used as a heat source of the second-effect vertical pipe evaporator 8, and the secondary steam generated by the second-effect vertical pipe evaporator 8 is also used as a heat source of the horizontal pipe evaporator 7;
(d) Concentrating the flashed coal chemical wastewater in a horizontal tube evaporator 7 again, increasing the salinity of the wastewater from 7% -8% to 8% -9%, heating and evaporating the concentrated wastewater in a series-connected two-effect vertical tube evaporator to generate saturated solution, and completing crystallization in a centrifugal crystallization device 12 to realize zero emission of the wastewater;
(e) The steam condensate in the low temperature multi-effect evaporator 3, condenser 4, horizontal tube evaporator 7, second effect standpipe evaporator 8 and first effect standpipe evaporator 9 is recovered into condensate tank 13.
By adopting the technical scheme, the coal chemical wastewater is pressurized by the feed pump and enters the condenser for preheating, and exchanges heat with the last-effect steam entering the low-temperature multi-effect evaporator of the condenser, the temperature of the coal chemical wastewater is increased to 50 ℃ from 20 ℃, and the steam is condensed into liquid and flows out. The preheated coal chemical wastewater flows to a low-temperature multi-effect evaporator, is heated and evaporated in the low-temperature multi-effect evaporator, the salinity of the wastewater is improved from 3% to 5%, and then is pressurized and conveyed to a wet oxidation reactor and a flash tank by a conveying pump; the pressurized wastewater enters a high-temperature high-pressure wet oxidation reactor, and most of COD in the wastewater can be removed under the actions of high temperature, high pressure and a catalyst. The wastewater treated by the wet-type oxidizer at about 300 ℃ enters a flash tank for flash evaporation, saturated steam obtained by flash evaporation is used as a heat source of a first-effect evaporator of the low-temperature multi-effect evaporator, the wastewater which is not evaporated in the flash tank flows to a horizontal tube evaporator for concentration again, and the salinity of the wastewater is improved from about 5% to about 6.7%. The horizontal tube evaporator takes medium-pressure steam and steam discharged by the vertical tube evaporators connected in series in two effects as heat sources, high-salt wastewater flowing out of the flash tank is evaporated and concentrated, the generated steam is condensed into condensed water by the condenser, and the salinity of the high-salt wastewater is concentrated from 6.7% to about 9% after evaporation. The concentrated high-salt wastewater flows to a two-effect standpipe evaporator, the two-effect standpipe evaporator mainly takes external high-temperature medium-pressure steam as a heat source, 9% of the salt-containing wastewater is evaporated and concentrated to generate saturated wastewater, and the saturated wastewater is crystallized in a centrifugal crystallization device, so that zero emission of pollutants is realized.
The above embodiments are only for illustrating the technical solution of the present invention, and are not limiting. Although the invention has been described in detail with reference to the foregoing embodiments, those skilled in the art may still make modifications to the technical solutions described in the foregoing embodiments, or may make equivalent substitutions for some or all of the technical features thereof; such modifications and substitutions do not depart from the spirit of the invention.