Organic wastewater normal pressure evaporation and catalytic digestion purification coupling process and system

Abstract

The application discloses a kind of organic wastewater atmospheric and vacuum evaporation and catalytic digestion purification coupling system, including wastewater preheater, n-stage wastewater evaporation and catalytic digestion purification system, wastewater preheater is connected with the import of wastewater evaporator of first-stage wastewater evaporation and catalytic digestion purification system;In each wastewater evaporation and catalytic digestion purification system, the gas outlet of wastewater evaporator is connected with the import of catalytic purification reactor via steam heat exchanger;In first-stage to n-1-stage wastewater evaporation and catalytic digestion purification system, the outlet of catalytic purification reactor is connected with the wastewater evaporator of next-stage wastewater evaporation and catalytic digestion purification system via steam heat exchanger;The outlet of catalytic purification reactor of n-stage wastewater evaporation and catalytic digestion purification system is connected with wastewater preheater via steam heat exchanger.The application realizes the standard discharge of wastewater under the condition of energy saving.

Description

TECHNICAL FIELD

[0001] The present application relates to an organic wastewater evaporation purification process and system, in particular to an organic wastewater atmospheric and vacuum evaporation and catalytic digestion purification coupling process and system. BACKGROUND

[0002] Organic wastewater is wastewater discharged by chemical, pharmaceutical, pesticide, papermaking, leather, food and other industries, and the content of organic matter in the wastewater varies. The COD in the organic wastewater is usually above 2000 mg / L, and the COD in some wastewater is as high as tens of thousands or even hundreds of thousands of mg / L. These organic wastewater often has complex composition, high color and odor, which can cause adverse effects on the surrounding environment. Some organic wastewater cannot be treated by conventional methods due to its difficulty in biodegradation, which brings great environmental pressure to enterprises.

[0003] At present, the treatment method of organic wastewater mostly adopts multi-effect evaporation method. For example, patent CN104150668A discloses a multi-effect evaporation treatment method for chemical mother liquor wastewater. At least two evaporators are arranged in series to form a multi-effect evaporation treatment. The mother liquor wastewater and steam flow countercurrently, and the wastewater is continuously evaporated. The treated chemical mother liquor wastewater enters the first evaporator at the low temperature end and flows to the high temperature end along the series of evaporators, while the starting heating steam and the secondary steam generated by the evaporation of the treated chemical mother liquor wastewater flow countercurrently, thereby forming a countercurrent evaporation treatment. The chemical mother liquor realizes multi-effect evaporation in the flow direction of stripping and fractionation separation. The condensed liquid obtained by evaporation is used for process chemical feed liquid. The multi-effect evaporation technology only performs a phase change process on the chemical mother liquor wastewater, and the condensed liquid cannot be directly discharged up to standard, but can only be used for process water recycling. In addition, the multi-effect evaporation technology has the characteristics that the mother liquor wastewater and steam are countercurrently contacted, that is, the multi-stage evaporator can only treat one stream of mother liquor wastewater at the same time, which greatly limits the evaporation efficiency of each evaporator. SUMMARY

[0004] The purpose of the present application is to provide an organic wastewater atmospheric and vacuum evaporation and catalytic digestion purification coupling process, which can realize high-efficiency evaporation of wastewater by each evaporator, and purify the organic matter in the wastewater, so that the wastewater can be discharged up to standard.

[0005] The purpose of the present application is achieved by the following technical solutions:

[0006] The organic wastewater normal pressure evaporation and catalytic digestion purification coupling system comprises a wastewater preheater, n-stage wastewater evaporation and catalytic digestion purification systems, and each stage of the wastewater evaporation and catalytic digestion purification systems comprises a wastewater evaporator, a steam heat exchanger and a catalytic purification reactor; the wastewater preheater is connected with the inlet of the wastewater evaporator of the first-stage wastewater evaporation and catalytic digestion purification system; in each stage of the wastewater evaporation and catalytic digestion purification systems, the gas outlet of the wastewater evaporator is connected with the inlet of the catalytic purification reactor through the steam heat exchanger; in the first-stage to the (n-1)-stage wastewater evaporation and catalytic digestion purification systems, the outlet of the catalytic purification reactor is connected with the heat medium inlet of the jacket layer of the wastewater evaporator of the next-stage wastewater evaporation and catalytic digestion purification system through the steam heat exchanger to heat the wastewater as a heat source; in the n-stage wastewater evaporation and catalytic digestion purification system, the outlet of the catalytic purification reactor is connected with the heat medium inlet of the wastewater preheater through the steam heat exchanger.

[0007] n is an integer from 3 to 6, that is, the organic wastewater normal pressure evaporation and catalytic digestion purification coupling system comprises 3 to 6 stages of wastewater evaporation and catalytic digestion purification systems, the number of the wastewater evaporators is 3 to 6, the number of the steam heat exchangers is the same as that of the wastewater evaporators, and the number of the catalytic purification reactors is the same as that of the wastewater evaporators.

[0008] The wastewater evaporator is a wastewater evaporator provided with a jacket layer, and the jacket layer is provided with a heat medium inlet and a heat medium outlet.

[0009] The catalytic purification reactor is an adiabatic reactor without heat exchange with the outside.

[0010] An organic wastewater normal pressure evaporation and catalytic digestion purification coupling process comprises the following steps:

[0011] After being preheated by the wastewater preheater, the wastewater enters the first-stage wastewater evaporator of the first-stage wastewater evaporation and catalytic digestion purification system, the first-stage wastewater evaporator uses live steam as a heat source to heat the wastewater, the wastewater (including organic matters in the wastewater) is completely vaporized to obtain steam, the steam is exchanged with secondary steam discharged from the first-stage catalytic purification reactor in the first-stage steam heat exchanger, and then enters the first-stage catalytic purification reactor while oxygen-containing gas is introduced, the organic matters in the steam are catalytically oxidized under the action of a catalyst, secondary steam is discharged from the top of the first-stage catalytic purification reactor, the secondary steam is exchanged with the steam to be introduced into the first-stage catalytic purification reactor in the first-stage steam heat exchanger, and then enters the second-stage steam heat exchanger of the second-stage wastewater evaporation and catalytic digestion purification system as a heat source to exchange heat and obtain purified water;

[0012] The wastewater enters the wastewater evaporator of the first-stage wastewater evaporation and catalytic digestion and purification system, the secondary steam discharged from the catalytic purification reactor of the previous-stage wastewater evaporation and catalytic digestion and purification system is used as a heat source, the wastewater is vaporized to form steam, the steam enters the steam heat exchanger of the same-stage wastewater evaporation and catalytic digestion and purification system to exchange heat with the secondary steam discharged from the catalytic purification reactor of the same stage, then enters the catalytic purification reactor of the same stage, and the oxygen-containing gas is introduced, the organic matters in the steam are catalytically oxidized under the action of the catalyst to form secondary steam, the secondary steam exchanges heat with the steam to be introduced into the catalytic purification reactor of the same stage, then enters the steam heat exchanger of the next-stage wastewater evaporation and catalytic digestion and purification system to exchange heat as a heat source, and purified water is obtained;

[0013] The wastewater enters the wastewater evaporator of the first-stage wastewater evaporation and catalytic digestion and purification system, the secondary steam discharged from the catalytic purification reactor of the previous-stage wastewater evaporation and catalytic digestion and purification system is used as a heat source, the wastewater is vaporized to form steam, the steam enters the steam heat exchanger of the same-stage wastewater evaporation and catalytic digestion and purification system to exchange heat with the secondary steam discharged from the catalytic purification reactor of the same stage, then enters the catalytic purification reactor of the same stage, and the oxygen-containing gas is introduced, the organic matters in the steam are catalytically oxidized under the action of the catalyst to form secondary steam, the secondary steam exchanges heat with the steam to be introduced into the catalytic purification reactor of the same stage, then enters the steam heat exchanger of the next-stage wastewater evaporation and catalytic digestion and purification system to exchange heat as a heat source, and purified water is obtained;

[0014] The organic wastewater atmospheric evaporation and catalytic digestion and purification coupling process specifically comprises the following steps:

[0015] The wastewater is preheated by the wastewater preheater and then enters the first-stage wastewater evaporator of the first-stage wastewater evaporation and catalytic digestion and purification system, the first-stage wastewater evaporator uses live steam as a heat source to heat the wastewater, the wastewater is completely vaporized to obtain steam, the steam exchanges heat with the secondary steam discharged from the first-stage catalytic purification reactor in the first-stage steam heat exchanger to be heated, then enters the first-stage catalytic purification reactor, and the oxygen-containing gas is introduced, the organic matters in the steam are catalytically oxidized into inorganic small molecular substances such as carbon dioxide and water under the action of the catalyst, and the water vapor together forms secondary steam, and the secondary steam is discharged from the top of the first-stage catalytic purification reactor;

[0016] The secondary steam discharged from the first stage catalytic purification reactor enters the first stage steam heat exchanger, exchanges heat with the steam to be introduced into the first stage catalytic purification reactor, and then enters the second stage wastewater evaporation and catalytic digestion purification system as a heat source to heat wastewater in the second stage wastewater evaporator. The secondary steam is condensed to obtain purified water, and the wastewater in the second stage wastewater evaporator is vaporized to form steam. The pressure of the obtained steam is lower than that of the steam formed by the first stage wastewater evaporator. The steam enters the second stage steam heat exchanger, exchanges heat with the secondary steam discharged from the second stage catalytic purification reactor, and is heated. Then, the steam enters the second stage catalytic purification reactor, and an oxygen-containing gas is introduced. The organic matter in the steam is catalytically oxidized into inorganic small molecular substances such as carbon dioxide and water under the action of the catalyst, and forms secondary steam together with water vapor. The secondary steam is discharged from the top of the second stage catalytic purification reactor.

[0017] The secondary steam discharged from the first stage catalytic purification reactor enters the first stage steam heat exchanger, exchanges heat with the steam to be introduced into the first stage catalytic purification reactor, and then enters the second stage wastewater evaporation and catalytic digestion purification system as a heat source to heat wastewater in the second stage wastewater evaporator. The secondary steam is condensed to obtain purified water, and the wastewater in the second stage wastewater evaporator is vaporized to form steam. The pressure of the obtained steam is lower than that of the steam formed by the first stage wastewater evaporator. The steam enters the second stage steam heat exchanger, exchanges heat with the secondary steam discharged from the second stage catalytic purification reactor, and is heated. Then, the steam enters the second stage catalytic purification reactor, and an oxygen-containing gas is introduced. The organic matter in the steam is catalytically oxidized into inorganic small molecular substances such as carbon dioxide and water under the action of the catalyst, and forms secondary steam together with water vapor. The secondary steam is discharged from the top of the second stage catalytic purification reactor.

[0018] By analogy, the wastewater enters the wastewater evaporator of the second stage wastewater evaporation and catalytic digestion purification system to the wastewater evaporator of the (n-1) stage wastewater evaporation and catalytic digestion purification system. The secondary steam discharged from the catalytic purification reactor of the previous stage wastewater evaporation and catalytic digestion purification system is used as a heat source. The wastewater is vaporized to form steam. The steam enters the same stage steam heat exchanger and exchanges heat with the secondary steam discharged from the same stage catalytic purification reactor. Then, the steam enters the same stage catalytic purification reactor, and an oxygen-containing gas is introduced. The organic matter in the steam is catalytically oxidized to form secondary steam under the action of the catalyst. The secondary steam exchanges heat with the steam to be introduced into the same stage catalytic purification reactor, and then enters the next stage steam heat exchanger as a heat source. The secondary steam is condensed to obtain purified water. Until the secondary steam obtained by catalytic oxidation in the catalytic purification reactor of the n stage wastewater evaporation and catalytic digestion purification system exchanges heat with the steam formed by the n stage steam heat exchanger, and is used as a heat source for the wastewater preheater 1 to exchange heat with the wastewater to be introduced into the first stage wastewater evaporator 2. The secondary steam is condensed to obtain purified water, and is directly discharged.

[0019] The waste water fed into the waste water evaporator of each stage of the waste water evaporation and catalytic digestion purification system can be the same or different. The COD value of the waste water is 2000-55000 mg O2 / L, and the COD value of the purified water obtained after treatment is below 30 mg O2 / L.

[0020] The pressure in the waste water evaporator of the first stage of the waste water evaporation and catalytic digestion purification system to the waste water evaporator of the nth stage of the waste water evaporation and catalytic digestion purification system is gradually reduced in steps.

[0021] Preferably, the pressure in the waste water evaporator of the first stage of the waste water evaporation and catalytic digestion purification system to the waste water evaporator of the nth stage of the waste water evaporation and catalytic digestion purification system is gradually reduced in steps, the absolute pressure in the waste water evaporator of the first stage of the waste water evaporation and catalytic digestion purification system is 2-4 atm, and the pressure difference between the pressure in the waste water evaporator of each stage of the waste water evaporation and catalytic digestion purification system and the pressure in the waste water evaporator of the next stage of the waste water evaporation and catalytic digestion purification system is 0.5-1.8 atm.

[0022] Or the pressure in the waste water evaporator of the first stage of the waste water evaporation and catalytic digestion purification system to the waste water evaporator of the nth stage of the waste water evaporation and catalytic digestion purification system is gradually reduced in steps, the absolute pressure in the waste water evaporator of the first stage of the waste water evaporation and catalytic digestion purification system is 0.95-1 atm, and the step pressure difference between the pressure in the waste water evaporator of each stage of the waste water evaporation and catalytic digestion purification system and the pressure in the waste water evaporator of the next stage of the waste water evaporation and catalytic digestion purification system is 0.2-0.4 atm.

[0023] The catalyst is a CeO2-CuO / Y molecular sieve catalyst, the loading amount of CeO2 in the catalyst is 5-15 wt%, and the loading amount of CuO is 5-20 wt%.

[0024] The oxygen-containing gas is oxygen or air, and the catalytic digestion reaction of the organic matter in the steam with the oxygen-containing gas in the presence of the catalyst occurs after the oxygen-containing gas is fed in. Since the purpose of the present application is to fully utilize the latent heat of water vapor, the prerequisite for fully utilizing the latent heat of water vapor is that the inert gas content in the obtained water vapor stream cannot be too high, otherwise the condensation amount of water vapor will be greatly reduced due to the presence of inert gas, and the utilization rate of the latent heat of water vapor will be reduced. Therefore, the amount of the oxygen-containing gas fed in is 1.005-1.05 times the stoichiometric oxygen consumption (COD) required for the oxidation reaction of the organic matter in the steam, based on pure oxygen.

[0025] The molar fraction of non-condensable gas in the secondary steam generated in the catalytic purification reaction of each stage of the waste water evaporation and catalytic digestion purification system is 0.1-3 mol%.

[0026] The non-condensable gas refers to oxygen, nitrogen and carbon dioxide.

[0027] The reaction temperature in the catalytic purification reactor is 350-450 DEG C, and the reaction pressure is determined by the evaporation pressure.

[0028] The reaction pressure in the catalytic purification reactor of the same stage wastewater evaporation and catalytic digestion and purification system is the same as the evaporation pressure in the wastewater evaporator; the pressure difference of the reaction pressure in the catalytic purification reactor of the adjacent two-stage wastewater evaporation and catalytic digestion and purification system is the same as the pressure difference of the evaporation pressure in the wastewater evaporator of the corresponding adjacent two-stage wastewater evaporation and catalytic digestion and purification system.

[0029] Specifically, in the first-stage wastewater evaporation and catalytic digestion and purification system, the reaction pressure in the catalytic purification reactor is the same as the pressure in the wastewater evaporator, and the pressure difference of the reaction pressure in the catalytic purification reactor of the first-stage wastewater evaporation and catalytic digestion and purification system and the reaction pressure in the catalytic purification reactor of the second-stage wastewater evaporation and catalytic digestion and purification system is the same as the pressure difference of the evaporation pressure in the wastewater evaporator of the first-stage wastewater evaporation and catalytic digestion and purification system and the evaporation pressure in the wastewater evaporator of the second-stage wastewater evaporation and catalytic digestion and purification system; in the second-stage wastewater evaporation and catalytic digestion and purification system, the reaction pressure in the catalytic purification reactor is the same as the pressure in the wastewater evaporator, and the pressure difference of the reaction pressure in the catalytic purification reactor of the second-stage wastewater evaporation and catalytic digestion and purification system and the reaction pressure in the catalytic purification reactor of the third-stage wastewater evaporation and catalytic digestion and purification system is the same as the pressure difference of the evaporation pressure in the wastewater evaporator of the second-stage wastewater evaporation and catalytic digestion and purification system and the evaporation pressure in the wastewater evaporator of the third-stage wastewater evaporation and catalytic digestion and purification system. By analogy, in the n-1-stage wastewater evaporation and catalytic digestion and purification system, the reaction pressure in the catalytic purification reactor is the same as the pressure in the wastewater evaporator, and the pressure difference of the reaction pressure in the catalytic purification reactor of the n-1-stage wastewater evaporation and catalytic digestion and purification system and the reaction pressure in the catalytic purification reactor of the n-stage wastewater evaporation and catalytic digestion and purification system is the same as the pressure difference of the evaporation pressure in the wastewater evaporator of the n-1-stage wastewater evaporation and catalytic digestion and purification system and the evaporation pressure in the wastewater evaporator of the n-stage wastewater evaporation and catalytic digestion and purification system. In the n-stage wastewater evaporation and catalytic digestion and purification system, the reaction pressure in the catalytic purification reactor is the same as the pressure in the wastewater evaporator.

[0030] The heat of the first-stage wastewater evaporation comes from the external live steam, the heat of the second-stage wastewater evaporation comes from the secondary steam generated by the first-stage catalytic digestion and purification device, and the heat of the n-stage wastewater evaporation comes from the secondary steam generated by the n-1-stage catalytic digestion and purification device, so that the heat of the adjacent two-stage wastewater evaporators is coupled, and the heat is fully utilized.

[0031] The beneficial effects of the present application are as follows:

[0032] (1), the present application adopts atmospheric and vacuum evaporation technology, through the change of step evaporation pressure, the pressure in the evaporator is gradually reduced, so that the wastewater can be evaporated at low energy consumption, the wastewater can be connected in series or in parallel into the step evaporation system, when connected in series, it can be downstream or upstream, so that the system has flexible operability.

[0033] (2), the present application couples catalytic digestion and evaporation together, after the evaporation of wastewater, the steam contacts with the catalyst in the catalytic purification reactor, whether the catalytic digestion is carried out at atmospheric pressure or under reduced pressure, both show good purification effect, compared with the gas-liquid contact used in wet oxidation, the transfer rate of gas-solid contact is two orders of magnitude higher or even faster. The present application can completely purify the organic matter in waste gas in the catalytic purification reactor while evaporating wastewater, so that the wastewater can be discharged in an energy-saving way.

[0034] (3), the organic wastewater atmospheric and vacuum evaporation and catalytic digestion purification coupling process of the present application can fully utilize the latent heat of water vapor, realize the treatment effect of 1 ton of live steam evaporating 2.5-4.5 tons of wastewater, and purify the organic pollutants in wastewater, so as to obtain purified water which can be directly discharged. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 It is a structure schematic diagram of an organic wastewater atmospheric and vacuum evaporation and catalytic digestion purification coupling system in example 1.

[0036] Figure 1 In the figure, 1 is a wastewater preheater, 2 is a first-stage wastewater evaporator, 3 is a first-stage steam heat exchanger, 4 is a first-stage catalytic purification reactor, 5 is a second-stage wastewater evaporator, 6 is a second-stage steam heat exchanger, 7 is a second-stage catalytic purification reactor, 8 is a third-stage wastewater evaporator, 9 is a third-stage steam heat exchanger, and 10 is a third-stage catalytic purification reactor.

[0037] Figure 2 It is a structure schematic diagram of an organic wastewater atmospheric and vacuum evaporation and catalytic digestion purification coupling system in example 3.

[0038] Figure 2 In the figure, 1 is a wastewater preheater, 2 is a first-stage wastewater evaporator, 3 is a first-stage steam heat exchanger, 4 is a first-stage catalytic purification reactor, 5 is a second-stage wastewater evaporator, 6 is a second-stage steam heat exchanger, 7 is a second-stage catalytic purification reactor, 8 is a third-stage wastewater evaporator, 9 is a third-stage steam heat exchanger, and 10 is a third-stage catalytic purification reactor. SPECIFIC IMPLEMENTATION METHOD

[0039] The technical solution of the present invention will be further described below through embodiments.

[0040] Example 1

[0041] like Figure 1 As shown, an organic wastewater atmospheric and vacuum evaporation and catalytic digestion purification coupled system includes a wastewater preheater 1, four identical wastewater evaporators, four identical steam heat exchangers, and four identical catalytic purification reactors; the four wastewater evaporators are designated as first-stage wastewater evaporator 2, second-stage wastewater evaporator 5, third-stage wastewater evaporator 8, and fourth-stage wastewater evaporator 11; the four steam heat exchangers are designated as first-stage steam heat exchanger 3, second-stage steam heat exchanger 6, third-stage steam heat exchanger 9, and fourth-stage steam heat exchanger 12; and the four catalytic digestion and purification reactors... The reactors are designated as the first-stage catalytic purification reactor 4, the second-stage catalytic purification reactor 7, the third-stage catalytic purification reactor 10, and the fourth-stage catalytic purification reactor 13. A wastewater evaporator, a steam heat exchanger, and a catalytic purification reactor constitute a single-stage wastewater evaporation and catalytic digestion purification system. The system comprises four stages of wastewater evaporation and catalytic digestion purification systems: the first-stage wastewater evaporation and catalytic digestion purification system, the second-stage wastewater evaporation and catalytic digestion purification system, the third-stage wastewater evaporation and catalytic digestion purification system, and the fourth-stage wastewater evaporation and catalytic digestion purification system.

[0042] All four wastewater evaporators are equipped with jacketed layers, which have heating medium inlets and outlets.

[0043] All four catalytic purification reactors are adiabatic reactors with no heat exchange with the outside environment. The catalysts packed in the four catalytic purification reactors are all CeO2-CuO / Y molecular sieve catalysts, with a CeO2 loading of 10 wt% and a CuO loading of 15 wt%.

[0044] The wastewater preheater 1 is provided with a water inlet and a water outlet. The water outlet of the wastewater preheater 1 is connected with the water inlet of the first-stage wastewater evaporator 2 in the first-stage wastewater evaporation and catalytic digestion purification system. The heat medium inlet of the wastewater preheater 1 is connected with the heat medium outlet of the fourth-stage steam heat exchanger 12 in the fourth-stage wastewater evaporation and catalytic digestion purification system. The heat medium outlet of the wastewater preheater 1 is used for discharging purified water. The wastewater is preheated by the wastewater preheater 1 and then enters the first-stage wastewater evaporator 2. The live steam is introduced into the heat medium inlet of the first-stage wastewater evaporator 2 to heat and vaporize the wastewater. The live steam is condensed by heat exchange and discharged from the heat medium outlet. The gas outlet at the top of the first-stage wastewater evaporator 2 is connected with the inlet at the bottom of the first-stage catalytic purification reactor 4 through the first-stage steam heat exchanger 3. The outlet at the top of the first-stage catalytic purification reactor 4 is connected with the heat medium inlet of the second-stage wastewater evaporator 5 through the first-stage steam heat exchanger 3. The gas outlet at the top of the second-stage wastewater evaporator 5 is connected with the inlet of the second-stage catalytic purification reactor 7 through the second-stage steam heat exchanger 6. The outlet at the top of the second-stage catalytic purification reactor 7 is connected with the heat medium inlet of the third-stage wastewater evaporator 8 through the second-stage steam heat exchanger 6. The gas outlet at the top of the third-stage wastewater evaporator 8 is connected with the inlet of the third-stage catalytic purification reactor 10 through the third-stage steam heat exchanger 9. The outlet at the top of the third-stage catalytic purification reactor 10 is connected with the heat medium inlet of the fourth-stage wastewater evaporator 11 through the third-stage steam heat exchanger 9. The gas outlet at the top of the fourth-stage wastewater evaporator 11 is connected with the inlet of the fourth-stage catalytic purification reactor 13 through the fourth-stage steam heat exchanger 12. The outlet at the top of the fourth-stage catalytic purification reactor 13 is connected with the heat medium inlet of the wastewater preheater 1 through the fourth-stage steam heat exchanger 12.

[0045] An organic wastewater atmospheric and vacuum evaporation and catalytic digestion purification coupling process based on the system of the embodiment, comprising:

[0046] The first waste water (COD 50809 mgO2 / L) enters the waste water preheater 1 under a pressure of 0.99 atm and a flow rate of 1000 kg / h, is preheated to 80°C, and then enters the first stage waste water evaporator 2. The first stage waste water evaporator 2 is heated by live steam. The live steam (0.2 MPa) is introduced into the jacket layer of the first stage waste water evaporator 2 at a flow rate of 1070 kg / h. After heat exchange between the live steam and the waste water, the live steam is condensed to form purified water. The waste water (including the organic matter in the waste water) is completely vaporized in the first stage waste water evaporator 2 to obtain steam at a pressure of 0.99 atm. The steam enters the first stage steam heat exchanger 3 to exchange heat with the secondary steam (temperature 400°C) discharged from the first stage catalytic purification reactor 4. The steam (temperature 280°C) after heat exchange and temperature rise enters the first stage catalytic purification reactor (loaded with catalyst) 4. Oxygen is introduced into the first stage negative pressure catalytic digestion and purification reactor 4 at a flow rate of 53.34 kg / h. In the first stage catalytic purification reactor 4, the organic matter in the steam is oxidized to inorganic small molecular substances such as carbon dioxide and water under the action of the catalyst at a reaction temperature of 400°C to form secondary steam (temperature 400°C, total amount of non-condensable gas in the secondary steam about 2.9 mol%).

[0047] The secondary steam obtained by catalytic digestion in the first stage catalytic purification reactor 4 enters the first stage steam heat exchanger 3 to exchange heat with the steam, and the temperature of the secondary steam is reduced to 229.7°C. The secondary steam enters the second stage waste water evaporator 5 as a heat source to exchange heat with the waste water in the second stage waste water evaporator 5. The secondary steam is condensed to form purified water (COD about 27 mgO2 / L) which is directly discharged. The second waste water (COD 50809 mgO2 / L) enters the second stage waste water evaporator 5 at a flow rate of 1032 kg / h, and is vaporized to form steam. The steam enters the second stage steam heat exchanger 6 to exchange heat with the secondary steam discharged from the second stage catalytic purification reactor 7, and the temperature of the steam is raised to 280°C. The steam then enters the second stage catalytic purification reactor (loaded with catalyst) 7. Oxygen is introduced into the second stage catalytic purification reactor 7 at a flow rate of 53.35 kg / h. In the second stage catalytic purification reactor 7, the organic matter in the steam is oxidized to inorganic small molecular substances such as carbon dioxide and water under the action of the catalyst at a reaction temperature of 400°C to form secondary steam (temperature 400°C, total amount of non-condensable gas in the secondary steam about 2.8 mol%).

[0048] The secondary steam from the catalytic digestion in the second stage catalytic purification reactor 7 enters the second stage steam heat exchanger 6, and after heat exchange with steam, the temperature is reduced to 217.6°C. The secondary steam enters the third stage wastewater evaporator 8 as a heat source, and after heat exchange with the wastewater in the third stage wastewater evaporator 8, the secondary steam is condensed to form purified water (COD is about 23 mg O2 / L) which is directly discharged. The third wastewater (COD is 50809 mg O2 / L) enters the third stage wastewater evaporator 8 at a flow rate of 1007 kg / h, and is vaporized to form steam. The steam enters the third stage steam heat exchanger 9, and after heat exchange with the secondary steam discharged from the third stage catalytic purification reactor 10, the temperature is increased to 280°C. The steam then enters the third stage catalytic purification reactor (loaded with catalyst) 10, and oxygen is introduced into the third stage catalytic purification reactor 10 at a flow rate of 53.35 kg / h. At a reaction temperature of 400°C, the organic matter in the steam is oxidized to inorganic small molecular substances such as carbon dioxide and water under the action of the catalyst to form secondary steam (temperature is 400°C, and the total amount of non-condensable gas in the secondary steam is about 2.98 mol%).

[0049] The secondary steam from the catalytic digestion in the third stage catalytic purification reactor 10 enters the third stage steam heat exchanger 9, and after heat exchange with steam, the temperature is reduced to 207.4°C. The secondary steam enters the fourth stage wastewater evaporator 11 as a heat source, and after heat exchange with the wastewater in the fourth stage wastewater evaporator 11, the secondary steam is condensed to form purified water (COD is about 25 mg O2 / L) which is directly discharged. The fourth wastewater (COD is 50809 mg O2 / L) enters the fourth stage wastewater evaporator 11 at a flow rate of 1040 kg / h, and is vaporized to form steam. The steam enters the fourth stage wastewater steam heat exchanger 12, and after heat exchange with the secondary steam discharged from the fourth stage catalytic purification reactor 13, the temperature is increased to 280°C. The steam then enters the fourth stage catalytic purification reactor (loaded with catalyst) 13, and oxygen is introduced into the fourth stage catalytic purification reactor 13 at a flow rate of 53.35 kg / h. At a reaction temperature of 400°C, the organic matter in the steam is oxidized to inorganic small molecular substances such as carbon dioxide and water under the action of the catalyst to form secondary steam (temperature is 400°C, and the total amount of non-condensable gas in the secondary steam is about 2.9 mol%).

[0050] The secondary steam from the catalytic digestion in the fourth stage catalytic purification reactor 13 enters the fourth stage steam heat exchanger 12, and after heat exchange with the steam discharged from the fourth stage wastewater evaporator 11, the temperature is reduced to 180.7°C. The secondary steam enters the wastewater preheater 1 as a heat source for preheating the first wastewater, and after heat exchange with the wastewater, purified water (COD is about 21 mg O2 / L) is formed which is directly discharged.

[0051] The absolute pressure of the first-stage wastewater evaporator 2 is 0.99 atm, the absolute pressure of the second-stage wastewater evaporator 5 is 0.75 atm, the evaporation absolute pressure of the third-stage wastewater evaporator 8 is 0.5 atm, and the absolute pressure of the fourth-stage wastewater evaporator 11 is 0.15 atm.

[0052] The reaction pressure in the first-stage catalytic purification reactor 4 is the same as the pressure in the first-stage wastewater evaporator, the pressure difference between the reaction pressure in the first-stage catalytic purification reactor 4 and the reaction pressure in the second-stage catalytic purification reactor 7 is the same as the pressure difference between the evaporation pressure in the first-stage wastewater evaporator 2 and the evaporation pressure in the second-stage wastewater evaporator; the reaction pressure in the second-stage catalytic purification reactor 7 is the same as the pressure in the second-stage wastewater evaporator 5, and the pressure difference between the reaction pressure in the second-stage catalytic purification reactor 7 and the reaction pressure in the third-stage catalytic purification reactor 10 is the same as the pressure difference between the evaporation pressure in the second-stage wastewater evaporator 5 and the evaporation pressure in the third-stage wastewater evaporator. The reaction pressure in the third-stage catalytic purification reactor 9 is the same as the pressure in the third-stage wastewater evaporator 9, and the pressure difference between the reaction pressure in the third-stage catalytic purification reactor 9 and the reaction pressure in the fourth-stage catalytic purification reactor 13 is the same as the pressure difference between the pressure in the third-stage wastewater evaporator 8 and the pressure in the fourth-stage wastewater evaporator 11. The reaction pressure in the fourth-stage catalytic purification reactor 13 is the same as the pressure in the fourth-stage wastewater evaporator 11.

[0053] The heat for the wastewater evaporation in the first-stage wastewater evaporator 2 comes from the external live steam, the heat for the wastewater evaporation in the second-stage wastewater evaporator 5 comes from the secondary steam generated by the first-stage catalytic purification reactor 4, the heat for the wastewater evaporation in the third-stage wastewater evaporator 8 comes from the secondary steam generated by the second-stage catalytic purification reactor 7, and the heat for the wastewater evaporation in the fourth-stage wastewater evaporator 11 comes from the secondary steam generated by the third-stage catalytic purification reactor 10. The ratio of the total amount of the evaporated wastewater to the amount of the consumed live steam is 4.07, i.e., 1 ton of live steam (fresh steam) can evaporate about 4.07 tons of wastewater, and the energy saving reaches 75.4%.

[0054] Example 2

[0055] An organic wastewater atmospheric and vacuum evaporation and catalytic digestion and purification coupling process based on the system described in Example 1, comprising:

[0056] The first waste water (COD 3500 mgO2 / L) enters the waste water preheater 1 at a pressure of 0.99 atm and a flow rate of 1000 kg / h, is preheated to 80°C, enters the first stage waste water evaporator 2, which is heated by live steam, the live steam (0.2 MPa) is introduced into the jacket of the first stage waste water evaporator at a flow rate of 1065 kg / h, and the waste water (including the organic matter in the waste water) is completely vaporized in the first stage waste water evaporator to obtain steam at a pressure of 0.99 atm, which enters the first stage steam heat exchanger 3 to exchange heat with the secondary steam (temperature 380°C) discharged from the first stage catalytic purification reactor 4, the steam (temperature 280°C) after heat exchange is introduced into the first stage catalytic purification reactor (loaded with catalyst) 4, and oxygen is introduced into the first stage catalytic purification reactor 4 at a flow rate of 3.52 kg / h, at a reaction temperature of 380°C, the organic matter in the steam is oxidized to inorganic small molecular substances such as carbon dioxide and water under the action of the catalyst to form secondary steam (temperature 380°C, total amount of non-condensable gas in the secondary steam about 0.2 mol%).

[0057] The secondary steam obtained by catalytic digestion in the first stage catalytic digestion purification reactor 4 enters the first stage steam heat exchanger 3, and the temperature is reduced to 198.6°C after heat exchange with steam, and is introduced into the second stage waste water evaporator 5 as a heat source to exchange heat with the waste water of the second stage waste water evaporator, the secondary steam is condensed to form purified water (COD about 18 mgO2 / L), which is directly discharged. The second waste water (COD 3500 mgO2 / L) enters the second stage waste water evaporator 17 at a flow rate of 1064 kg / h, is vaporized to form steam, which enters the second stage steam heat exchanger 6 to exchange heat with the secondary steam discharged from the second stage catalytic purification reactor 7, and the temperature is raised to 280°C, then enters the second stage catalytic purification reactor (loaded with catalyst) 7, and oxygen is introduced into the second stage catalytic purification reactor 22 at a flow rate of 3.8 kg / h, at a reaction temperature of 380°C, the organic matter in the steam is oxidized to inorganic small molecular substances such as carbon dioxide and water under the action of the catalyst to form secondary steam (temperature 380°C, total amount of non-condensable gas in the secondary steam about 0.2 mol%).

[0058] The secondary steam from the catalytic digestion in the second stage catalytic purification reactor 7 enters the second stage steam heat exchanger 6, and after heat exchange with steam, the temperature is reduced to 192.6°C, and the secondary steam enters the third stage wastewater evaporator 8 as a heat source to exchange heat with the wastewater in the third stage evaporator, and the secondary steam is condensed to form purified water (COD is about 16 mg O2 / L) which is directly discharged. The third wastewater (COD is 3500 mg O2 / L) enters the third stage wastewater evaporator 8 at a flow rate of 1138 kg / h, and is vaporized to form steam, which enters the third stage steam heat exchanger 9 to exchange heat with the secondary steam discharged from the third stage catalytic purification reactor 10, and the temperature of the steam is increased to 280°C, and then the steam enters the third stage catalytic purification reactor (loaded with catalyst) 10, and oxygen is introduced into the third stage catalytic purification reactor at a flow rate of 4.14 kg / h, and at a reaction temperature of 380°C, the organic matter in the steam is oxidized to inorganic small molecular substances such as carbon dioxide and water under the action of the catalyst to form secondary steam (the temperature is 380°C, and the total amount of non-condensable gas in the secondary steam is about 0.2 mol%).

[0059] The secondary steam from the catalytic digestion in the third stage catalytic purification reactor 10 enters the third stage steam heat exchanger 9, and after heat exchange with steam, the temperature is reduced to 184°C, and the secondary steam enters the fourth stage wastewater evaporator 11 as a heat source to exchange heat with the wastewater in the fourth stage wastewater evaporator, and the secondary steam is condensed to form purified water (COD is about 20 mg O2 / L) which is directly discharged. The fourth wastewater (COD is 3500 mg O2 / L) enters the fourth stage wastewater evaporator at a flow rate of 1230 kg / h, and is vaporized to form steam, which enters the fourth stage steam heat exchanger 12 to exchange heat with the secondary steam discharged from the fourth stage catalytic purification reactor, and the temperature of the steam is increased to 280°C, and then the steam enters the fourth stage catalytic purification reactor (loaded with catalyst) 13, and oxygen is introduced into the fourth stage catalytic purification reactor 13 at a flow rate of 4.4 kg / h, and at a reaction temperature of 380°C, the organic matter in the steam is oxidized to inorganic small molecular substances such as carbon dioxide and water under the action of the catalyst to form secondary steam (the temperature is 380°C, and the total amount of non-condensable gas in the secondary steam is about 0.2 mol%).

[0060] The secondary steam from the catalytic digestion in the fourth stage catalytic purification reactor 13 enters the fourth stage steam heat exchanger 12, and after heat exchange with steam, the temperature is reduced to 160.8°C, and the secondary steam enters the jacket of the wastewater preheater 1 as a heat source for the first wastewater preheating, and after heat exchange with the wastewater, purified water (COD is about 14 mg O2 / L) is formed which is directly discharged.

[0061] The absolute pressure in the first stage wastewater evaporator is 0.99 atm, the absolute pressure in the second stage wastewater evaporator is 0.77 atm, the absolute pressure in the third stage wastewater evaporator is 0.55 atm, and the absolute pressure in the fourth stage wastewater evaporator is 0.2 atm.

[0062] The catalytic purification reactor is an adiabatic reactor without heat exchange with the outside. The reaction pressure in the first-stage catalytic purification reactor is the same as the pressure in the first-stage wastewater evaporator, and the pressure difference between the reaction pressure in the first-stage catalytic purification reactor and the reaction pressure in the second-stage catalytic purification reactor is the same as the pressure difference between the pressure in the first-stage wastewater evaporator and the pressure in the second-stage wastewater evaporator; the reaction pressure in the second-stage catalytic purification reactor is the same as the pressure in the second-stage wastewater evaporator, and the pressure difference between the reaction pressure in the second-stage catalytic purification reactor and the reaction pressure in the third-stage catalytic purification reactor is the same as the pressure difference between the pressure in the second-stage wastewater evaporator and the pressure in the third-stage wastewater evaporator; the reaction pressure in the third-stage catalytic purification reactor is the same as the pressure in the third-stage wastewater evaporator, and the pressure difference between the reaction pressure in the third-stage catalytic purification reactor and the reaction pressure in the fourth-stage catalytic purification reactor is the same as the pressure difference between the pressure in the third-stage wastewater evaporator and the pressure in the fourth-stage wastewater evaporator; the reaction pressure in the fourth-stage catalytic purification reactor is the same as the pressure in the fourth-stage wastewater evaporator. The catalysts loaded in the four catalytic digestion and purification reactors are CeO2-CuO / Y molecular sieve catalysts, the loading amount of CeO2 in the catalyst is 10 wt%, and the loading amount of CuO is 15 wt%.

[0063] The heat for evaporating wastewater in the first-stage wastewater evaporator is from the outside live steam, the heat for evaporating wastewater in the second-stage wastewater evaporator is from the secondary steam generated by the first-stage catalytic purification reactor, the heat for evaporating wastewater in the third-stage wastewater evaporator is from the secondary steam generated by the second-stage catalytic purification reactor, and the heat for evaporating wastewater in the fourth-stage wastewater evaporator is from the secondary steam generated by the third-stage catalytic purification reactor. The ratio of the total amount of evaporated wastewater to the amount of consumed live steam is 4.16, that is, 1 ton of live steam (fresh steam) can evaporate about 4.16 tons of wastewater, and the energy saving reaches 76%.

[0064] Example 3

[0065] As shown in Figure 2 An organic wastewater atmospheric evaporation and catalytic digestion and purification coupling system includes one wastewater preheater, three identical wastewater evaporators, three identical steam heat exchangers, and three identical catalytic purification reactors. The three wastewater evaporators are a first-stage wastewater evaporator 2, a second-stage wastewater evaporator 5, and a third-stage wastewater evaporator 8; the three steam heat exchangers are a first-stage steam heat exchanger 3, a second-stage steam heat exchanger 6, and a third-stage steam heat exchanger 9; and the three catalytic digestion and purification reactors are a first-stage catalytic purification reactor 4, a second-stage catalytic purification reactor 7, and a third-stage catalytic purification reactor 10. There are three-stage wastewater evaporation and catalytic digestion and purification systems: a first-stage wastewater evaporation and catalytic digestion and purification system, a second-stage wastewater evaporation and catalytic digestion and purification system, and a third-stage wastewater evaporation and catalytic digestion and purification system.

[0066] The three wastewater evaporators are all wastewater evaporators with jacket layers, and the jacket layers are provided with heat medium inlets and heat medium outlets.

[0067] The three catalytic purification reactors are all adiabatic reactors without heat exchange with the outside. The catalyst filled in the catalytic purification reactors is CeO2-CuO / Y molecular sieve catalyst, and the loading amount of CeO2 in the catalyst is 10wt%, and the loading amount of CuO is 15wt%.

[0068] The wastewater preheater 1 is provided with a water inlet and a water outlet, the water outlet of the wastewater preheater 1 is connected with the water inlet of the first-stage wastewater evaporator 2, the heat medium inlet of the wastewater preheater 1 is connected with the heat medium outlet of the third-stage water vapor heat exchanger 10, the heat medium outlet of the wastewater preheater 1 is used for discharging purified water, and the wastewater is preheated by the wastewater preheater 1 and then enters the first-stage wastewater evaporator 2; the jacket of the first-stage wastewater evaporator 2 is provided with a heat medium inlet and a heat medium outlet, live steam enters the heat medium inlet to heat and vaporize the wastewater, and the live steam is condensed after heat exchange and is discharged from the heat medium outlet; the outlet of the first-stage wastewater evaporator 2 is connected with the inlet of the first-stage catalytic purification reactor 4 through the first-stage water vapor heat exchanger 3, the outlet of the first-stage catalytic purification reactor 4 is connected with the heat medium inlet of the second-stage wastewater evaporator 5 through the first-stage water vapor heat exchanger 3, the outlet of the second-stage wastewater evaporator 5 is connected with the inlet of the second-stage catalytic purification reactor 7 through the second-stage water vapor heat exchanger 6, the outlet of the second-stage catalytic purification reactor 7 is connected with the heat medium inlet of the third-stage wastewater evaporator 8 through the second-stage water vapor heat exchanger 6, the outlet of the third-stage wastewater evaporator 8 is connected with the inlet of the third-stage catalytic purification reactor 10 through the third-stage water vapor heat exchanger 9, and the outlet of the third-stage catalytic purification reactor 10 is connected with the heat medium inlet of the wastewater preheater 1 through the third-stage water vapor heat exchanger 9.

[0069] An organic wastewater atmospheric and vacuum evaporation and catalytic digestion and purification coupling process based on the system of the embodiment, comprising:

[0070] The first wastewater (COD 25000 mgO2 / L) is preheated in the wastewater preheater 1 at a flow rate of 1100 kg / h and then enters the first-stage wastewater evaporator 2, which is heated by live steam. The live steam (0.6 MPa) is introduced into the jacket of the first-stage wastewater evaporator 2 at a flow rate of 1140 kg / h. After heat exchange between the live steam and the wastewater, the live steam is condensed to form purified water. The wastewater (including the organic matter in the wastewater) in the first-stage wastewater evaporator 2 is completely vaporized to obtain steam. The wastewater steam enters the first-stage wastewater steam heat exchanger 3 and exchanges heat with the secondary steam (temperature 400°C) discharged from the first-stage catalytic digestion reactor 4, so that the temperature of the wastewater steam is increased to 280°C. Then, the wastewater steam enters the first-stage catalytic purification reactor 4 (loaded with catalyst). At the same time, oxygen is introduced into the first-stage catalytic purification reactor 4 at a flow rate of 28.8 kg / h. At a reaction temperature of 400°C, the organic matter in the wastewater steam is oxidized to inorganic small molecular substances such as carbon dioxide and water under the action of the catalyst to form secondary steam (temperature increased to 400°C, and the total amount of non-condensable gas in the secondary steam is about 1.47 mol%).

[0071] The secondary steam obtained by catalytic digestion in the first-stage catalytic digestion and purification reactor enters the first-stage water steam heat exchanger 3 and exchanges heat with the steam, so that the temperature of the secondary steam is decreased to 121.8°C. The secondary steam is used as a heat source to enter the second-stage wastewater evaporator 5 and exchanges heat with the wastewater in the second-stage wastewater evaporator. After condensation, the secondary steam forms purified water (COD about 16 mgO2 / L) and is discharged. The second wastewater (COD 25000 mgO2 / L) enters the second-stage wastewater evaporator 5 at a flow rate of 1125 kg / h and is vaporized to form wastewater steam. The obtained wastewater steam enters the second-stage water steam heat exchanger 6 and exchanges heat with the secondary steam stream discharged from the second-stage catalytic purification reactor 7, so that the temperature of the wastewater steam is increased to 300°C. Then, the wastewater steam enters the second-stage catalytic purification reactor 7 (loaded with catalyst). At the same time, oxygen is introduced into the second-stage catalytic purification reactor at a flow rate of 28.8 kg / h. At a reaction temperature of 400°C, the organic matter in the wastewater steam is oxidized to inorganic small molecular substances such as carbon dioxide and water under the action of the catalyst to form secondary steam (temperature increased to 400°C, and the total amount of non-condensable gas in the secondary steam is about 1.44 mol%).

[0072] The secondary steam from the catalytic digestion in the second stage catalytic purification reactor 7 enters the second stage water steam heat exchanger 6, exchanges heat with the waste water steam, and its temperature is reduced to 190.8°C, and then enters the third stage waste water evaporator 8 as a heat source. After exchanging heat with the waste water in the third stage evaporator, the secondary steam is condensed to form purified water (COD is about 23 mgO2 / L) which is discharged. The third waste water (COD is 25000 mgO2 / L) enters the third stage waste water evaporator 8 at a flow rate of 1230 kg / h, and is vaporized to form waste water steam. The waste water steam from the third stage waste water evaporator 8 enters the third stage water steam heat exchanger 9, exchanges heat with the secondary steam from the third stage catalytic purification reactor, and its temperature is increased to 300°C. Then the waste water steam enters the third stage catalytic purification reactor (loaded with catalyst) 10, and oxygen is introduced into the third stage catalytic purification reactor at a flow rate of 31 kg / h. At a reaction temperature of 400°C, the organic substances in the waste water steam are oxidized to inorganic small molecular substances such as carbon dioxide and water under the action of the catalyst to form secondary steam (the temperature is increased to 400°C, and the total amount of non-condensable gas in the secondary steam is about 1.41 mol%).

[0073] The secondary steam from the catalytic digestion in the third stage catalytic purification reactor enters the third stage water steam heat exchanger 9, exchanges heat with the waste water steam, and its temperature is reduced to 175.7°C. Then the secondary steam enters the waste water preheater 1 as a heat source to preheat the first waste water. After exchanging heat with the waste water, the secondary steam is condensed to form purified water (COD is about 28 mgO2 / L) which is directly discharged.

[0074] The absolute pressure in the first stage waste water evaporator is 2.03 atm, the absolute pressure in the second stage waste water evaporator is 1.21 atm, and the absolute pressure in the third stage waste water evaporator is 0.709 atm.

[0075] The reaction pressure in the first stage catalytic purification reactor is the same as the pressure in the first stage waste water evaporator, and the pressure difference between the reaction pressure in the first stage catalytic purification reactor and the reaction pressure in the second stage catalytic purification reactor is the same as the pressure difference between the evaporation pressure in the first stage waste water evaporator and the evaporation pressure in the second stage waste water evaporator. The reaction pressure in the second stage catalytic purification reactor is the same as the pressure in the second stage waste water evaporator, and the pressure difference between the reaction pressure in the second stage catalytic purification reactor and the reaction pressure in the third stage catalytic purification reactor is the same as the pressure difference between the evaporation pressure in the second stage waste water evaporator and the evaporation pressure in the third stage waste water evaporator. The reaction pressure in the third stage catalytic purification reactor is the same as the pressure in the third stage waste water evaporator.

[0076] The heat for the first wastewater evaporation in the first-stage wastewater evaporator is from the external live steam, the heat for the second wastewater evaporation in the second-stage wastewater evaporator is from the secondary steam generated by the first-stage catalytic purification reactor, and the heat for the third wastewater evaporation in the third-stage wastewater evaporator is from the secondary steam generated by the second-stage catalytic purification reactor; the heat for the first wastewater preheating in the first-stage wastewater evaporator is from the secondary steam generated by the third-stage catalytic purification reactor. The ratio of the total amount of the evaporated wastewater to the amount of the consumed live steam is 3.03, i.e., 1 ton of steam can evaporate about 3 tons of wastewater, and the energy saving reaches 67%.

[0077] Example 4

[0078] An organic wastewater atmospheric and vacuum evaporation and catalytic digestion and purification coupling process based on the system described in Example 3, comprising:

[0079] The first wastewater (COD is 48500 mgO2 / L) enters the wastewater preheater 1 at a flow rate of 1100 kg / h, is preheated, and then enters the first-stage wastewater evaporator 2. The first-stage wastewater evaporator is heated by live steam, the live steam introduced into the jacket of the first-stage wastewater evaporator is at an absolute pressure of 0.8 MPa, and the flow rate of the introduced live steam is 1186 kg / h. The wastewater (including the organic matter in the wastewater) in the first-stage wastewater evaporator is completely vaporized to obtain steam, the steam enters the first-stage steam heat exchanger 3, exchanges heat with the secondary steam (temperature is 400℃) discharged from the first-stage catalytic purification reactor 4, and the temperature of the steam is increased to 280℃, and then enters the first-stage catalytic purification reactor (loaded with a catalyst) 4. Oxygen is introduced into the first catalytic purification reactor at a flow rate of 54.95 kg / h. At a reaction temperature of 400℃, the organic matter in the steam is oxidized into inorganic small molecular substances such as carbon dioxide and water to form secondary steam (temperature is 400℃, and the total amount of non-condensable gas in the secondary steam is about 2.8 mol%) under the action of the catalyst.

[0080] The secondary steam from the catalytic digestion in the first catalytic purification reactor 4 enters the first steam heat exchanger 3, exchanges heat with the waste water steam, and its temperature is reduced to 147.9°C, and then enters the second waste water evaporator 6 as a heat source. After exchanging heat with the waste water in the second waste water evaporator, the secondary steam is condensed to form purified water (COD is about 11 mgO2 / L) and is discharged. The second waste water (COD is 25000 mgO2 / L) enters the second waste water evaporator 5 at a flow rate of 1137 kg / h, and is vaporized to form steam. The steam enters the second steam heat exchanger 6, exchanges heat with the secondary steam discharged from the second catalytic purification reactor 7, and its temperature is increased to 300°C, and then enters the second catalytic purification reactor 7 (loaded with catalyst). Oxygen is introduced into the second catalytic purification reactor 7 at a flow rate of 28.8 kg / h. At a reaction temperature of 400°C, the organic matters in the steam are oxidized into inorganic small molecular substances such as carbon dioxide and water under the action of the catalyst to form secondary steam (the temperature is 400°C, and the total amount of non-condensable gas in the secondary steam is about 1.42 mol%).

[0081] The secondary steam from the catalytic digestion in the second catalytic purification reactor 7 enters the second steam heat exchanger, exchanges heat with the waste water steam, and its temperature is reduced to 190.8°C, and then enters the third waste water evaporator 8 as a heat source. After exchanging heat with the waste water in the third evaporator 8, the secondary steam is condensed to form purified water (COD is about 23 mgO2 / L) and is discharged. The third waste water (COD is 25000 mgO2 / L) enters the third waste water evaporator 8 at a flow rate of 1230 kg / h, and is vaporized to form steam. The obtained steam enters the third steam heat exchanger 9, exchanges heat with the secondary waste water steam discharged from the third catalytic purification reactor 10, and its temperature is increased to 300°C, and then enters the third catalytic digestion purification reactor 10 (loaded with catalyst). Oxygen is introduced into the third catalytic purification reactor at a flow rate of 31.4 kg / h. At a reaction temperature of 400°C, the organic matters in the steam are oxidized into inorganic small molecular substances such as carbon dioxide and water under the action of the catalyst to form secondary steam (the temperature is increased to 400°C, and the total amount of non-condensable gas in the secondary steam is about 1.44 mol%).

[0082] The secondary steam from the catalytic digestion in the third catalytic purification reactor 10 enters the third steam heat exchanger 9, exchanges heat with the waste water steam, and its temperature is reduced to 208.2°C, and then enters the waste water preheater 1 as a heat source for preheating the first waste water. After exchanging heat with the first waste water, purified water (COD is about 19 mgO2 / L) is formed and is directly discharged.

[0083] The evaporation absolute pressure in the first waste water evaporator is 3.8 atm, the evaporation absolute pressure in the second waste water evaporator is 2 atm, and the evaporation absolute pressure in the third waste water evaporator is 1 atm.

[0084] The catalytic purification reactor is an adiabatic reactor without heat exchange with the outside. The reaction pressure in the first catalytic purification reactor is the same as the pressure in the first wastewater evaporator, and the pressure difference between the reaction pressure in the first catalytic purification reactor and the reaction pressure in the second catalytic purification reactor is the same as the pressure difference between the evaporation pressure in the first wastewater evaporator and the evaporation pressure in the second wastewater evaporator; the reaction pressure in the second catalytic purification reactor is the same as the pressure in the second wastewater evaporator, and the pressure difference between the reaction pressure in the second catalytic purification reactor and the reaction pressure in the third catalytic purification reactor is the same as the pressure difference between the evaporation pressure in the second wastewater evaporator and the evaporation pressure in the third wastewater evaporator. The reaction pressure in the third catalytic purification reactor is the same as the pressure in the third wastewater evaporator. The catalyst filled in the catalytic purification reactor is CeO2-CuO / Y molecular sieve catalyst, the loading amount of CeO2 in the catalyst is 10 wt%, and the loading amount of CuO is 15 wt%.

[0085] The heat for the first wastewater evaporation in the first wastewater evaporator comes from the live steam from the outside, the heat for the second wastewater evaporation in the second wastewater evaporator comes from the secondary steam generated by the first catalytic purification reactor, and the heat for the third wastewater evaporation in the third wastewater evaporator comes from the secondary steam generated by the second catalytic purification reactor; the heat for the first wastewater preheating in the first wastewater evaporator comes from the secondary steam generated by the third catalytic purification reactor. The ratio between the total amount of the evaporated wastewater and the amount of the consumed live steam is 2.94, that is, 1 ton of steam can evaporate about 2.94 tons of wastewater, and the energy saving reaches 66%.

Claims

1. A coupled process for purifying organic wastewater by atmospheric and vacuum evaporation and catalytic digestion, characterized in that: The system includes a coupled system for atmospheric and vacuum evaporation and catalytic digestion purification of organic wastewater. The system comprises a wastewater preheater and n-stage wastewater evaporation and catalytic digestion purification systems. Each stage of the wastewater evaporation and catalytic digestion purification system includes a wastewater evaporator, a steam heat exchanger, and a catalytic purification reactor. The wastewater preheater is connected to the inlet of the wastewater evaporator in the first-stage system. In each stage, the outlet of the wastewater evaporator is connected to the inlet of the catalytic purification reactor via a steam heat exchanger. From the first stage to the (n-1)th stage, the outlet of the catalytic purification reactor is connected to the wastewater evaporator of the next stage via a steam heat exchanger to serve as a heat source for heating the wastewater. The outlet of the catalytic purification reactor in the n-stage system is connected to the wastewater preheater via a steam heat exchanger. The process includes: After being preheated by the wastewater preheater, the wastewater enters the first-stage wastewater evaporator of the first-stage wastewater evaporation and catalytic digestion purification system. The first-stage wastewater evaporator uses live steam as a heat source. The wastewater is vaporized to obtain steam, which enters the first-stage steam heat exchanger to exchange heat with the secondary steam discharged from the first-stage catalytic purification reactor. Then, it enters the first-stage catalytic purification reactor. At the same time, oxygen-containing gas is introduced. The organic matter in the steam is catalytically oxidized under the action of the catalyst. Secondary steam is discharged from the top of the first-stage catalytic purification reactor. The secondary steam exchanges heat with the steam to be entered into the first-stage catalytic purification reactor in the first-stage steam heat exchanger and then enters the second-stage steam heat exchanger of the second-stage wastewater evaporation and catalytic digestion purification system as a heat source to exchange heat, thus obtaining purified water. Wastewater enters the first-stage wastewater evaporation and catalytic digestion purification system and then the wastewater evaporator of the (n-1)th-stage wastewater evaporation and catalytic digestion purification system. Using the secondary steam discharged from the first-stage system as a heat source, the wastewater vaporizes to form steam. This steam then enters the steam heat exchanger of the same-stage system and exchanges heat with the secondary steam discharged from the same-stage catalytic purification reactor. It then enters the same-stage reactor while oxygen-containing gas is introduced. The organic matter in the steam undergoes catalytic oxidation under the action of a catalyst to form secondary steam. This secondary steam exchanges heat with the steam awaiting entry into the same-stage catalytic purification reactor before entering the steam heat exchanger of the next-stage system as a heat source, resulting in purified water. Wastewater enters the wastewater evaporator of the nth-stage wastewater evaporation and catalytic digestion purification system, using the secondary steam discharged from the (n-1)th-stage wastewater evaporation and catalytic digestion purification system as a heat source. The wastewater vaporizes to form steam, which enters the steam heat exchanger of the nth-stage wastewater evaporation and catalytic digestion purification system to exchange heat with the secondary steam discharged from the catalytic purification reactor of the nth-stage wastewater evaporation and catalytic digestion purification system. It then enters the same-stage catalytic purification reactor, while oxygen-containing gas is introduced. The organic matter in the steam undergoes catalytic oxidation under the action of a catalyst to form secondary steam. The secondary steam exchanges heat with the steam to be entered into the nth-stage catalytic purification reactor in the nth-stage steam heat exchanger and then serves as the heat source for the wastewater preheater. It then exchanges heat with the wastewater to be entered into the first-stage wastewater evaporation and catalytic digestion purification system to obtain purified water. n is an integer from 3 to 6; The pressure in the wastewater evaporator of the first-stage wastewater evaporation and catalytic digestion purification system gradually decreases from the pressure in the nth-stage wastewater evaporation and catalytic digestion purification system.

2. The coupled process of atmospheric and vacuum evaporation and catalytic digestion purification of organic wastewater according to claim 1, characterized in that: The wastewater evaporator is a wastewater evaporator with a jacket layer; the catalytic purification reactor is an adiabatic reactor that does not exchange heat with the outside environment.

3. The coupled process of atmospheric and vacuum evaporation and catalytic digestion purification of organic wastewater according to claim 1, characterized in that: The absolute pressure in the wastewater evaporator of the first-stage wastewater evaporation and catalytic digestion purification system is 2–4 atm, and the pressure difference between the wastewater evaporator in each stage of the wastewater evaporation and catalytic digestion purification system and the wastewater evaporator in the next stage is 0.5–1.8 atm; or the absolute pressure in the wastewater evaporator of the first-stage wastewater evaporation and catalytic digestion purification system is 0.95–1 atm, and the pressure difference between the wastewater evaporator in each stage of the wastewater evaporation and catalytic digestion purification system and the wastewater evaporator in the next stage is 0.2–0.4 atm.

4. The coupled process of atmospheric and vacuum evaporation and catalytic digestion purification of organic wastewater according to claim 1, characterized in that: The catalyst is a CeO2-CuO / Y molecular sieve catalyst, in which the loading of CeO2 is 5-15 wt% and the loading of CuO is 5-20 wt%.

5. The coupled process of atmospheric and vacuum evaporation and catalytic digestion purification of organic wastewater according to claim 1, characterized in that: The oxygen-containing gas is oxygen or air; the amount of oxygen introduced into the gas, expressed as pure oxygen, is 1.005 to 1.05 times the stoichiometric oxygen consumption required for the oxidation reaction of organic matter in the steam. The molar fraction of non-condensable gas in the secondary steam generated during the catalytic purifier reaction of each stage of wastewater evaporation and catalytic digestion purification system is 0.1–3 mol.

6. The coupled process of atmospheric and vacuum evaporation and catalytic digestion purification of organic wastewater according to claim 1, characterized in that: The reaction temperature in the catalytic purification reactor is 350–450℃.

7. The coupled process of atmospheric and vacuum evaporation and catalytic digestion purification of organic wastewater according to claim 1, characterized in that: The wastewater flowing into each stage of the wastewater evaporator in the wastewater evaporation and catalytic digestion purification system may be the same or different; the COD value of the wastewater is 2000-55000 mgO2 / L; and the COD value of the purified water is below 30 mgO2 / L.

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