A method and device for treating ethylene waste alkali liquor

Abstract

The present invention relates to a method and a treatment device for treating ethylene waste alkali liquid. An appropriate amount of oil refining waste alkali liquid is added to the ethylene waste alkali liquid, and the alkali liquid is transported to a flotation unit for treatment. After treatment, the alkali liquid is transported to a first heat exchanger of a heat exchange unit, and after heat extraction, the waste alkali liquid enters a wet oxidation reactor for wet oxidation reaction. The treated waste alkali liquid enters a second heat exchanger of the heat exchange unit, and after heat exchange, the waste alkali liquid enters a gas-liquid separation unit, and the separated gas phase returns to the flotation unit as flotation gas. The first heat exchanger and the second heat exchanger use the same heat exchange medium. The present invention aims at the water quality characteristics of ethylene waste alkali liquid, and while ensuring the treatment effect and making full use of the reaction heat, it can avoid the blockage and scaling of the heat exchange equipment caused by long-term operation, as well as the local overheating of the wet oxidation reactor.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental protection water pollution control, and specifically relates to a method and a treatment device for treating ethylene waste alkali liquid. Background Art

[0002] In the process of ethylene production, alkali washing is currently widely used to remove acidic gases such as CO2 and H2S in cracked gas. The alkali washing process produces a large amount of waste alkali liquid, which contains not only residual NaOH but also inorganic salts such as Na2S and Na2CO3 generated during the alkali washing process. On the other hand, the condensation of heavy components in the cracked gas and the polymerization of dienes and aldehydes during the alkali washing process cause a large amount of organic matter to enter the waste alkali liquid. Since ethylene waste alkali liquid contains high concentrations of COD and sulfides and has poor biodegradability, most of the treatment plans for ethylene waste alkali liquid at home and abroad are to pre-treat it to remove sulfides and organic matter in it to prevent impact on the biochemical system of the sewage treatment plant.

[0003] According to the water quality characteristics of ethylene waste alkali liquor, some patents have proposed treatment methods. CN98121081.3 discloses a method for treating waste alkali liquor of oil product alkali refining in the petroleum refining industry, wherein the waste alkali liquor mainly containing inorganic sulfide, organic sulfide, phenol and cyclohexane acid discharged from the oil product alkali refining unit in the petroleum refining process is subjected to wet liquid phase oxidation, and the waste alkali liquor is contacted with oxygen-containing gas exceeding the theoretical oxygen demand at 100-190°C and a pressure that keeps the waste alkali liquor in liquid phase, and the inorganic sulfide and organic sulfide in the waste alkali liquor are oxidized by molecular oxygen to convert the sulfur therein into sulfate and / or thiosulfate, and then the oxidized waste alkali liquor is depressurized and cooled, and acidified to recover the phenol and cyclohexane acid therein, and the waste water obtained is treated by intermittent activated sludge process (SBR), and the salt content in the waste water entering the SBR biological reaction tank is controlled below 30g / L. This method does not produce air pollution, has light corrosion to the device, and can achieve desulfurization and deodorization of waste alkali liquid, but it is necessary to add a large amount of steam to the reactor to maintain the reaction temperature, so the device has high operating energy consumption. CN201310537921.7 discloses a method for treating ethylene waste alkali liquid, which adopts a combined process of flotation oil removal-high temperature wet oxidation-evaporation concentration-adjusting alkali concentration, can efficiently remove COD and sulfide in ethylene waste alkali liquid, and can also recover sodium salt and reuse the treated sodium hydroxide solution to achieve zero discharge of ethylene waste alkali liquid. However, due to its high operating temperature, its operating energy consumption is high.

[0004] In order to reduce operating energy consumption and achieve effective use of heat, researchers proposed to set up a heat exchanger in front of the wet oxidation reactor to preheat the imported waste alkali liquid with the wet oxidation material to reduce the steam consumption of the reaction device. However, this will cause some organic matter in the feed waste alkali liquid to have the conditions to undergo a certain degree of thermal polymerization, which will cause the heat exchanger to be blocked during long-term operation, which is not conducive to long-term stable operation.

[0005] US20050171390A1 discloses a wet oxidation treatment process and system, which is to wet oxidize wastewater containing one or more compounds with carbon-heteroatom bonds under high temperature and high pressure to destroy the carbon-heteroatom bonds of at least one of the compounds, and the treated wastewater enters the subsequent advanced oxidation system. This technology uses waste alkali liquid and oxidation air to mix and preheat the feed, which can easily cause some diolefin organic matter to undergo thermal polymerization and block the heat exchanger, and because the air contains oxygen, the oxygen will participate in the formation of peroxide self-polymers, leading to further generation of polymers, aggravating the blockage of the heat exchanger. In addition, the polymer-containing waste alkali liquid enters the subsequent wet oxidation reactor, and long-term operation will also cause the reactor to be blocked.

[0006] In summary, the various methods currently used to treat waste alkali liquor all have problems such as being inappropriate, insufficient in treatment effect, large investment and high operating costs. With the large-scale and intensive production of ethylene, the output of ethylene waste alkali liquor has also increased significantly, so the development of efficient, energy-saving and stable treatment technology is the focus of current research. Summary of the invention

[0007] In view of the shortcomings of the prior art, the present invention provides a method and a device for treating ethylene waste alkali liquor. The present invention aims at the water quality characteristics of ethylene waste alkali liquor, and can avoid the blockage and scaling of heat exchange equipment caused by long-term operation, as well as the local overheating of wet oxidation reactors, while ensuring the treatment effect and making full use of the reaction heat.

[0008] The present invention provides a method for treating ethylene waste alkali liquor, comprising the following contents:

[0009] An appropriate amount of waste alkali liquid from oil refining is added to the waste alkali liquid of ethylene, and the waste alkali liquid is transported to the flotation unit for treatment; after treatment, the waste alkali liquid is transported to the first heat exchanger of the heat exchange unit, and after heat extraction, the waste alkali liquid enters the wet oxidation reactor, and contacts with oxygen-containing gas under the pressure condition that ensures that the waste alkali liquid is in the liquid phase, and performs wet oxidation reaction; the waste alkali liquid after treatment enters the second heat exchanger of the heat exchange unit, and after heat exchange, the waste alkali liquid enters the gas-liquid separation unit, and the separated gas phase returns to the flotation unit as flotation gas; the first heat exchanger and the second heat exchanger use the same heat exchange medium.

[0010] In the method of the present invention, the ethylene waste alkali liquid is a waste alkali liquid containing sulfide and COD produced in the ethylene cracking gas alkali refining process, wherein the COD concentration is 6000-100000 mg / L, S 2- The concentration is 2000-50000 mg / L, petroleum 600-1600 mg / L, and contains substances that are prone to thermal polymerization, such as diene substances, etc. The diene substance is at least one of butadiene, isoprene, etc.

[0011] In the method of the present invention, the waste alkali liquid from oil refining is at least one of the waste alkali liquid from dry gas desulfurization, the waste alkali liquid from liquefied gas desulfurization, the waste alkali liquid from catalytic gasoline, etc., wherein the COD is 30000-70000 mg / L, the S 2- The concentration is 10000-25000 mg / L. It also contains pollutants such as thiols and phenols, with a phenol concentration of 1000-1500 mg / L.

[0012] In the method of the present invention, the flotation unit can adopt a conventional flotation reactor, the flotation gas used in the startup phase can be any one of air, nitrogen, etc., and the gas phase generated by the gas-liquid separation unit is used in the stable operation phase. The residual heat of the gas helps to remove the easily polymerizable substances in the waste alkali liquid.

[0013] Furthermore, adding a certain amount of diethylhydroxylamine to the flotation unit, the amount of which is 0.01%-1% of the mass of the ethylene waste alkali liquid, helps to remove the easily polymerizable substances through the flotation unit, prevents them from polymerizing to form high polymers, and avoids clogging of the heat exchanger.

[0014] In the method of the present invention, the temperature of the waste alkali solution after heat exchange in the first heat exchanger is controlled to be 80-170°C, preferably 100-150°C.

[0015] In the method of the present invention, the wet oxidation reactor used in the wet oxidation unit can be various reactors conventionally used in the art, preferably a sleeve-type internal circulation reactor, and direct introduction of gas into the reactor can achieve full mixing. The reaction temperature of the wet oxidation is 170-230°C, preferably 180-210°C, the reaction pressure is 2.5-4.5MPa, preferably 3.0-4.0MPa, and the reaction time is 0.5-3.0h, preferably 1.0-2.0h.

[0016] In the method of the present invention, the oxygen-containing gas introduced into the wet oxidation unit can be at least one of air, oxygen, etc., and the ventilation volume is 100%-300% of the gas volume required for complete oxidation of COD in the waste alkali liquid, preferably 110%-200%.

[0017] In the present invention, if the COD concentration in the waste alkali liquid is low, resulting in insufficient heat release in the oxidation reaction, superheated steam can be introduced into the reactor to supplement heat.

[0018] In the present invention, the material after wet oxidation treatment enters the second heat exchanger, and the temperature of the waste alkali solution after heat exchange is controlled to be 110-170°C.

[0019] In the present invention, a heat exchange medium storage tank is provided between the first heat exchanger and the second heat exchanger, and the two use the same heat exchange medium, which is used as a heat medium in the first heat exchanger and as a coolant in the second heat exchanger. The heat exchange medium enters the heat exchange medium storage tank, enters the second heat exchanger through a heat exchange medium circulation pump, and returns to the first heat exchanger after heat exchange with the material at the outlet of the wet oxidation reactor, exchanges heat with the waste alkali liquid after flotation treatment in the first heat exchanger, and returns to the heat exchange medium storage tank after cooling.

[0020] In the present invention, the first and second heat exchangers may be any one of a shell-and-tube heat exchanger, a double-tube heat exchanger, a shell-and-tube heat exchanger or a U-tube heat exchanger.

[0021] In the present invention, the heat exchange medium may be at least one of fresh water, circulating water, desalted water, deoxygenated water, etc., preferably deoxygenated water.

[0022] In the present invention, the waste alkali liquid after heat exchange in the second heat exchanger is transported to the gas-liquid separation unit for decompression separation. After the pressure is reduced to 0.2-0.5MPa, the temperature of the separated gas phase is 90-140°C, and it is transported to the flotation unit as flotation gas; the separated liquid phase is cooled to 40-50°C and then enters the sewage treatment plant. Since the sulfide is effectively treated, it will not affect the sewage treatment.

[0023] On the other hand, the present invention also provides a treatment device for the above-mentioned method for treating ethylene waste alkali liquid, which mainly includes a flotation unit, a heat exchange unit, a wet oxidation unit, and a gas-liquid separation unit, wherein the flotation unit mainly includes a flotation device, which is used to remove floating oil and some easily polymerizable organic matter in the ethylene waste alkali liquid; the heat exchange unit includes a first heat exchanger, a heat exchange medium storage tank and a second heat exchanger, which are used for heat exchange between the wet oxidation unit discharge material, the heat exchange working medium and the feed waste alkali liquid; the wet oxidation unit mainly includes a wet oxidation reactor, which is used to remove sulfide and some organic matter in the waste alkali liquid, and the oxidized material enters the second heat exchanger for heat exchange, and the material after heat exchange is separated by reduced pressure and then enters the gas-liquid separation unit.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) In order to realize heat utilization when treating ethylene waste alkali liquor by wet oxidation, researchers proposed to install a heat exchanger in front of the reactor and use the hot materials discharged from the wet oxidation reactor to directly heat the imported waste alkali liquor. However, the inventors of this application found in the experiment that with the long-term operation of the treatment device, the heat exchanger would be blocked and scaled. After analysis, it was found that some polymeric substances caused it. Based on this discovery, the inventors of this application installed flotation treatment in front of the heat exchanger, using flotation to remove oily substances and some easily polymerizable organic substances, and combined with indirect heat exchange to exchange heat for the imported waste alkali liquor of wet oxidation, thereby avoiding blockage of the heat exchanger on the basis of realizing full utilization of heat, ensuring long-term stable operation of the device, and reducing the energy consumption of the device.

[0026] (2) In view of the blockage and scaling problems of the heat exchanger and the water quality characteristics of ethylene waste alkali liquid and oil refinery waste alkali liquid, a proper amount of oil refinery waste alkali liquid is added to the ethylene waste alkali liquid. The oil refinery waste alkali liquid is used to inhibit the thermal polymerization of some dienes in the ethylene waste alkali liquid, thereby avoiding blockage and scaling of the heat exchanger; at the same time, effective treatment of part of the oil refinery waste alkali liquid can be achieved, which is more economical.

[0027] (3) In view of the problem of organic polymerization when ethylene waste alkali liquid enters the heat exchanger, flotation treatment is set up before the heat exchanger, and the high-temperature tail gas after gas-liquid separation is used as flotation gas, which can simultaneously remove the easily polymerizable substances and oil substances in the waste alkali liquid. In addition, the waste alkali liquid can also be preheated to make full use of the reaction heat.

[0028] (4) The first heat exchanger and the second heat exchanger are provided and use the same heat exchange medium to avoid blockage and scaling of the heat exchanger caused by the wet oxidation discharge material being directly used as a heat medium, thereby ensuring long-term operation of the device.

[0029] (5) The use of diethylhydroxylamine in the flotation unit helps to further remove the easily polymerizable diolefin substances and can also play an inhibitory role in the heat exchanger, further reducing the risk of blockage. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a process flow diagram of the present invention;

[0031] Among them: 101-1-ethylene waste alkali liquor, 101-2-oil refining waste alkali liquor, 102-compressed air, 103-steam, 104-gas phase tail gas, 105-treated waste alkali liquor; 201-flotation tank, 202-feed pump, 203-heat exchange medium circulation pump, 204-heat exchange medium storage tank, 205-first heat exchanger, 206-second heat exchanger, 207-wet oxidation reactor, 208-gas-liquid separator, 209-cooler. DETAILED DESCRIPTION

[0032] The following examples further illustrate the treatment method, device and effect of the present invention. The examples are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operation processes, but the protection scope of the present invention is not limited to the following examples.

[0033] The experimental methods in the following examples, unless otherwise specified, are all conventional methods in the art. The experimental materials used in the following examples, unless otherwise specified, were purchased from conventional biochemical reagent stores.

[0034] The processing device used in the embodiment of the present invention is as shown in the attached Figure 1 As shown, it mainly includes an air flotation unit, a heat exchange unit, a wet oxidation unit, and a gas-liquid separation unit, wherein the air flotation unit includes an air flotation tank 201, the heat exchange unit includes a first heat exchanger 205, a heat exchange medium storage tank 204, and a second heat exchanger 206, the wet oxidation unit mainly includes a wet oxidation reactor 207, and the gas-liquid separation unit includes a gas-liquid separator 208 and a cooler 209. The ethylene waste alkali liquid and the oil refining waste alkali liquid are respectively fed into the air flotation tank 201 to remove the The material is transported to the first heat exchanger 205 through the feed pump 202 after treatment. After heat extraction, the waste alkali liquid enters the wet oxidation reactor 207, and contacts with the oxygen-containing gas under the condition that the solution remains in the liquid phase, converting the sulfide in the waste alkali liquid into sulfate and thiosulfate. The oxidized material enters the second heat exchanger 206 for heat exchange with the discharge of the wet oxidation reactor. After heat exchange, the material enters the gas-liquid separator 208. After separation, the gas phase returns to the flotation tank 201, and the liquid phase is cooled by the cooler 209 and enters the sewage treatment plant. The first heat exchanger 205 and the second heat exchanger 206 use the same heat exchange medium, and a heat exchange medium storage tank 204 is set between the two. The heat exchange medium enters the heat exchange medium storage tank, enters the second heat exchanger through the heat exchange medium circulation pump, and exchanges heat with the material at the outlet of the wet oxidation reactor. After the heat exchange medium is heated, it enters the first heat exchanger, exchanges heat with the waste alkali liquid after the flotation unit treatment, and returns to the heat exchange medium storage tank after cooling.

[0035] In the present invention, the detection method of COD is the method specified in HJ 828-2017 (Determination of Chemical Oxygen Demand of Water Quality - Dichromate Method); S 2- The detection method is the method specified in HJ-T 60-2000 (Determination of sulfide in water quality - iodine titration method).

[0036] Example 1

[0037] The ethylene waste alkali liquid comes from the waste alkali liquid discharged during the alkali washing process of ethylene cracking gas in a certain factory, with a COD concentration of 35000mg / L and S 2- The concentration is 15200 mg / L, and that of petroleum is 1320 mg / L, including butadiene, isoprene and other substances.

[0038] The waste alkali liquid from oil refining comes from the waste alkali liquid discharged from the desulfurization process of a certain liquefied gas, with a COD concentration of 40000mg / L and S 2- The concentration is 12000mg / L and the phenol concentration is 1200mg / L.

[0039] Use attached Figure 1 The treatment process and device shown are used to treat the ethylene waste alkali liquid and the refinery waste alkali liquid in a mass ratio of 10:1, and then transported to the flotation tank for flotation treatment to remove substances such as diolefins in the waste alkali liquid.

[0040] Deoxygenated water is used as the heat exchange medium to enter the heat exchange medium storage tank, and is lifted to the second heat exchanger by the heat exchange medium circulation pump. The deoxygenated water is used as a refrigerant to exchange heat with the reactor discharge. After the deoxygenated water is heated, it enters the first heat exchanger as a heat medium. The first and second heat exchangers use shell-and-tube heat exchangers.

[0041] After the mixed waste alkali liquid is treated by flotation, it is transported to the first heat exchanger through the feed pump, and after heat exchange to 110°C, it enters the wet oxidation reactor to react with the compressed air introduced. The wet oxidation reactor adopts a sleeve-type internal circulation reactor. The air volume is 150% of the gas volume required for complete oxidation of COD in the waste alkali liquid. The reaction temperature is 190°C, the reaction pressure is 3.0MPa, and the reaction time is 2.0 hours. In the wet oxidation reactor, the sulfide in the waste alkali liquid is oxidized to sulfate and thiosulfate, and the organic matter is oxidized to low molecular organic acid.

[0042] The ethylene waste alkali liquid after wet oxidation treatment enters the second heat exchanger for heat exchange to 150°C, and then enters the gas-liquid separator for gas-liquid separation after the pressure is reduced to 0.4MPa. The separated gas phase is returned to the flotation tank for flotation treatment of the mixed waste alkali liquid. The separated liquid phase can be directly discharged into the sewage treatment plant after cooling.

[0043] Using the treatment process of the present invention, after 2000 hours of operation, the heat exchanger did not experience blockage. 2- The concentration is less than 1.0 mg / L, and the COD is less than 1000 mg / L. If the flotation unit is not set, the waste alkali solution can only be heated to 104°C after the same operation time, and steam needs to be added to the reactor to maintain the reaction temperature. The effluent COD is 2000 mg / L.

[0044] Example 2

[0045] The ethylene waste alkali liquid comes from the waste alkali liquid discharged during the alkali washing process of ethylene cracking gas in a certain factory, with a COD concentration of 35000mg / L and S 2- The concentration is 15200 mg / L, and that of petroleum is 1320 mg / L, including butadiene, isoprene and other substances.

[0046] The waste alkali liquid from oil refining comes from the waste alkali liquid discharged from the desulfurization process of a certain liquefied gas, with a COD concentration of 40000mg / L and S 2- The concentration is 12000mg / L and the phenol concentration is 1200mg / L.

[0047] Use attached Figure 1 The treatment process and device shown are used to treat the ethylene waste alkali liquid and the refinery waste alkali liquid in a mass ratio of 10:1, and then transported to the flotation tank for flotation treatment to remove substances such as diolefins in the waste alkali liquid.

[0048] Deoxygenated water is used as the heat exchange medium to enter the heat exchange medium storage tank, and is lifted to the second heat exchanger by the heat exchange medium circulation pump. The deoxygenated water is used as a refrigerant to exchange heat with the reactor discharge. After the deoxygenated water is heated, it enters the first heat exchanger as a heat medium. The first and second heat exchangers use shell-and-tube heat exchangers.

[0049] After the mixed waste alkali liquid is treated by flotation, it is transported to the first heat exchanger through the feed pump, and after heat exchange to 100°C, it enters the wet oxidation reactor to react with the compressed air introduced. The wet oxidation reactor adopts a sleeve-type internal circulation reactor. The air volume is 110% of the gas volume required for complete oxidation of COD in the waste alkali liquid. The reaction temperature is 150°C, the reaction pressure is 3.0MPa, and the reaction time is 2.0 hours. In the wet oxidation reactor, the sulfide in the waste alkali liquid is oxidized into sulfate and thiosulfate, and the organic matter is oxidized into low-molecular organic acid.

[0050] The ethylene waste alkali liquid after wet oxidation treatment enters the second heat exchanger for heat exchange to 140°C, and then enters the gas-liquid separator for gas-liquid separation after the pressure is reduced to 0.4MPa. The separated gas phase is returned to the flotation tank for flotation treatment of the feed waste alkali liquid. The separated liquid phase can be directly discharged into the sewage treatment plant after cooling.

[0051] Using the treatment process of the present invention, after 2000 hours of operation, the heat exchanger did not experience blockage. 2- The concentration is less than 20mg / L, and the COD is less than 3000mg / L. If the flotation unit is not set, the waste alkali solution can only be heated to 96℃ after the same operation time, and steam needs to be added to the reactor to maintain the reaction temperature. The effluent COD is 4500mg / L.

[0052] Example 3

[0053] The ethylene waste alkali liquid comes from the waste alkali liquid discharged during the alkali washing process of ethylene cracking gas in a certain factory, with a COD concentration of 35000mg / L and S 2- The concentration is 15200 mg / L, and that of petroleum is 1320 mg / L, including butadiene, isoprene and other substances.

[0054] The waste alkali liquid from oil refining comes from the waste alkali liquid discharged from the desulfurization process of a certain liquefied gas, with a COD concentration of 40000mg / L and S 2- The concentration is 12000mg / L and the phenol concentration is 1200mg / L.

[0055] Use attached Figure 1 The treatment process and device shown are used to treat the ethylene waste alkali liquid and the refinery waste alkali liquid in a mass ratio of 10:1, and then transported to the flotation tank for flotation treatment to remove substances such as diolefins in the waste alkali liquid.

[0056] Deoxygenated water is used as the heat exchange medium to enter the heat exchange medium storage tank, and is lifted to the second heat exchanger by the heat exchange medium circulation pump. The deoxygenated water is used as a refrigerant to exchange heat with the reactor discharge. After the deoxygenated water is heated, it enters the first heat exchanger as a heat medium. The first and second heat exchangers use shell-and-tube heat exchangers.

[0057] After the mixed waste alkali liquid is treated by flotation, it is transported to the first heat exchanger through the feed pump, and then enters the wet oxidation reactor after heat exchange to 170°C to react with the compressed air introduced. The wet oxidation reactor adopts a sleeve-type internal circulation reactor. The air volume is 200% of the gas volume required for complete oxidation of COD in the waste alkali liquid. The reaction temperature is 220°C, the reaction pressure is 4.5MPa, and the reaction time is 2.0 hours. In the wet oxidation reactor, the sulfide in the waste alkali liquid is oxidized into sulfate and thiosulfate, and the organic matter is oxidized into low-molecular organic acid.

[0058] The ethylene waste alkali liquid after wet oxidation treatment enters the second heat exchanger for heat exchange to 140°C, and then enters the gas-liquid separator for gas-liquid separation after the pressure is reduced to 0.4MPa. The separated gas phase is returned to the flotation tank for flotation treatment of the feed waste alkali liquid. The separated liquid phase can be directly discharged into the sewage treatment plant after cooling.

[0059] Using the treatment process of the present invention, after 2000 hours of operation, the heat exchanger did not experience blockage. 2- The concentration is less than 1.0mg / L and the COD is less than 800mg / L. If the flotation unit is not set, the waste alkali solution can only be heated to 178℃ after the same operation time, and steam needs to be added to the reactor to maintain the reaction temperature. The effluent COD is 2000mg / L.

[0060] Example 4

[0061] Same as Example 1, except that the ethylene waste alkali liquor and the oil refining waste alkali liquor were mixed in a mass ratio of 5:1. The device was operated for 1500 hours, and the heat exchanger was not blocked. 2- The concentration is less than 1.0mg / L and the COD is 1300mg / L.

[0062] Example 5

[0063] Same as Example 1, except that fresh water is used as the heat exchange medium. The device was operated for 2000 hours, and the heat exchanger was not blocked. 2- The concentration is less than 1.0mg / L and the COD is 1200mg / L.

[0064] Example 6

[0065] Same as Example 1, except that the first and second heat exchangers are double-tube heat exchangers. The device was operated for 2000 hours, and the heat exchanger was not blocked. 2- The concentration is less than 1.0mg / L and COD is less than 1000mg / L.

[0066] Example 7

[0067] Same as Example 1, except that a certain amount of diethylhydroxylamine was added during the deoxygenation treatment, and the amount added was 0.5% of the mass of the ethylene waste alkali liquid. The device was operated for 2000 hours, and the heat exchanger was not blocked. 2- The concentration is less than 1.0mg / L and the COD is less than 800mg / L.

[0068] Comparative Example 1

[0069] Same as Example 1, except that the heat exchanger uses direct heat exchange instead of heat exchange medium. The device ran for 2000 hours and there were blockage and scaling phenomena. 2- The concentration is less than 1.0mg / L and COD is less than 2000mg / L.

Claims

1. A method for treating ethylene waste alkali liquor, characterized in that The method includes the following steps: adding an appropriate amount of waste alkali liquid from oil refinery to waste alkali liquid from ethylene, and conveying the mixture to a flotation unit for treatment; After treatment, the waste alkali liquid is transported to the first heat exchanger of the heat exchange unit. After heat removal, the waste alkali liquid enters the wet oxidation unit, contacts with oxygen-containing gas under pressure conditions to ensure that the waste alkali liquid is in liquid phase, and performs wet oxidation reaction. The treated waste alkali liquid enters the second heat exchanger of the heat exchange unit. After heat exchange, the waste alkali liquid enters the gas-liquid separation unit, and the separated gas phase returns to the flotation unit as flotation gas. The first heat exchanger and the second heat exchanger use the same heat exchange medium. The ethylene waste alkali liquid is a waste alkali liquid containing sulfide and COD produced in the ethylene cracking gas alkali refining process, wherein the COD concentration is 6000-100000mg / L, S 2- The concentration is 2000-50000 mg / L, petroleum 600-1600 mg / L, which contains diolefins that are prone to thermal polymerization; the waste alkali liquid from oil refining is at least one of dry gas sweetening waste alkali liquid, liquefied gas sweetening waste alkali liquid, and catalytic gasoline waste alkali liquid, wherein the COD is 30000-70000 mg / L, S 2- The concentration is 10000-25000 mg / L, and it also contains mercaptan and phenol pollutants, among which the phenol concentration is 1000-1500 mg / L; diethylhydroxylamine is added to the flotation unit, and the added amount is 0.01%-1% of the mass of the ethylene waste alkali liquid; the waste alkali liquid after heat exchange in the second heat exchanger is transported to the gas-liquid separation unit for decompression separation. After the pressure is reduced to 0.2-0.5MPa, the temperature of the separated gas phase is 90-140℃, and it is transported to the flotation unit as flotation gas.

2. The method according to claim 1, characterized in that: In the ethylene waste alkali liquid, the diene substance is at least one of butadiene and isoprene.

3. The method according to claim 1, characterized in that: The flotation unit adopts a flotation reactor. The flotation gas used in the startup phase is any one of air and nitrogen. The gas phase generated by the gas-liquid separation unit is used in the stable operation phase.

4. The method according to claim 1, characterized in that: The temperature of the waste alkali liquid after heat exchange in the first heat exchanger is controlled to be 80-170°C.

5. The method according to claim 4, characterized in that: The temperature of the waste alkali solution after heat exchange in the first heat exchanger is controlled to be 100-150°C.

6. The method according to claim 1, characterized in that: The wet oxidation reactor used in the wet oxidation unit is a sleeve-type internal circulation reactor.

7. The method according to claim 1 or 6, characterized in that: The reaction temperature of the wet oxidation is 170-230° C., the reaction pressure is 2.5-4.5 MPa, and the reaction time is 0.5-3.0 h.

8. The method according to claim 7, characterized in that: The reaction temperature of the wet oxidation is 180-210° C., the reaction pressure is 3.0-4.0 MPa, and the reaction time is 1.0-2.0 h.

9. The method according to claim 1, characterized in that: The oxygen-containing gas introduced into the wet oxidation unit is at least one of air and oxygen, and the ventilation volume is 100%-300% of the gas volume required for complete oxidation of COD in the waste alkali liquid.

10. The method according to claim 9, characterized in that: The ventilation volume is 110%-200% of the volume required for complete oxidation of COD in the waste alkali liquid.

11. The method according to claim 1, characterized in that: If the COD concentration in the waste alkali liquid is low, resulting in insufficient heat release in the oxidation reaction, superheated steam is introduced into the reactor to supplement heat.

12. The method according to claim 1, characterized in that: After wet oxidation treatment, the material enters the second heat exchanger, and the temperature of the waste alkali liquid after heat exchange is controlled to be 110-170℃.

13. The method according to claim 1, characterized in that: A heat exchange medium storage tank is provided between the first heat exchanger and the second heat exchanger. The heat exchange medium enters the heat exchange medium storage tank, enters the second heat exchanger through a heat exchange medium circulation pump, returns to the first heat exchanger after heat exchange with the outlet material of the wet oxidation reactor, exchanges heat with the waste alkali liquid after flotation treatment in the first heat exchanger, and returns to the heat exchange medium storage tank after cooling.

14. The method according to claim 1, characterized in that: The first and second heat exchangers are any one of a shell-and-tube heat exchanger, a sleeve-and-tube heat exchanger, a shell-and-tube heat exchanger or a U-tube heat exchanger.

15. The method according to claim 1, characterized in that: The heat exchange medium is at least one of fresh water, circulating water, desalted water, and deoxygenated water.

16. The method according to claim 15, characterized in that: The heat exchange medium is deoxygenated water.

17. The method according to claim 1, characterized in that: The liquid phase separated by the gas-liquid separation unit is cooled to 40-50°C and then enters the sewage treatment plant.

18. A treatment device for the method for treating ethylene waste alkali liquor according to any one of claims 1 to 17, characterized in that It mainly includes a flotation unit, a heat exchange unit, a wet oxidation unit, and a gas-liquid separation unit, wherein the flotation unit mainly includes a flotation device for removing floating oil and some easily polymerizable organic matter in the ethylene waste alkali liquid; the heat exchange unit includes a first heat exchanger, a heat exchange medium storage tank and a second heat exchanger for heat exchange between the wet oxidation unit discharge material, the heat exchange working medium and the feed waste alkali liquid; the wet oxidation unit mainly includes a wet oxidation reactor for removing sulfide and some organic matter in the waste alkali liquid, and the oxidized material enters the second heat exchanger for heat exchange, and the material after heat exchange is separated by reduced pressure and then enters the gas-liquid separation unit.

Images