MTO concentrated water treatment device and method

Abstract

The invention relates to an MTO concentrated water treatment device and method.The treatment device comprises a circulating liquid phase hydrogenation unit and a dehydration unit, aldehyde and ketone components in MTO concentrated water are converted into mixed alcohol through circulating liquid phase hydrogenation, then the mixed alcohol is subjected to flash evaporation degassing, azeotropic distillation and zeolite membrane dehydration treatment, most of water in the mixed alcohol is removed, and the MTO concentrated water is obtained. According to the MTO concentrated water treatment device and the MTO concentrated water treatment method, a mixed alcohol product with low water content (about 2wt%) and wastewater with low alcohol content (less than 0.2 wt%) are obtained, the technical index of the obtained mixed alcohol product is higher than the national standard of alcohol-based liquid fuel GB16663-1996, and ethanol, isopropanol and 2-butanol products can be obtained through further separation. The additional value is also improved, and the purposes of improving the quality and improving the efficiency are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical production, and in particular relates to a method for treating methanol to olefins (MTO) concentrated water, which is used for recycling the by-product concentrated water of the MTO device. Background Art

[0002] Driven by the characteristics of fossil resource endowment of "rich in coal, lack of oil and little gas" and the continued strong consumption of downstream petrochemical products, modern coal chemical technology has developed rapidly and has become an important supplement to petrochemical industry. As one of the important components of modern coal chemical industry, coal-to-olefins has seen rapid technology promotion and industrial development in recent years, and its product market share has continued to expand, becoming the branch with the best economic benefits and the fastest production capacity growth in modern coal chemical industry. Continuously promoting the technological progress of coal-to-olefins and the high-quality development of the industry is of great significance for saving precious oil resources, meeting the growing demand for petrochemical product consumption, and ensuring national energy security.

[0003] The process flow of coal-to-olefins is relatively long. First, coal is used as raw material to produce methanol through gasification, transformation, purification, synthesis and other processes. Methanol is then used to produce olefins (ethylene + propylene), and then downstream products such as polyolefins (polyethylene, polypropylene) are produced. Among them, coal-to-methanol and olefin polymerization to produce polyolefins are both traditional mature technologies, while methanol-to-olefins (MTO) is a new technology that has been successfully developed in the past decade, and is also the core technical link of coal-to-olefins.

[0004] The MTO process is a process in which methanol reacts with a catalyst to generate low-carbon olefins. During the reaction, low-carbon olefin products mainly composed of ethylene and propylene and water byproducts are generated. At the same time, due to side reactions or trace amounts of methanol not reacted, the products will contain a small amount of oxygen-containing compounds such as methanol, ethanol, butyraldehyde, acetone, butanone and isopropanol. A small part of the above oxygen-containing compounds enters the post-separation system with the product gas, and is removed by water washing in the post-system. These waters enter the sewage stripping tower after condensation and washing with the reaction gas. The process wastewater obtained by concentrating organic matter in the sewage stripping tower is called concentrated water. The concentrated water is mainly composed of organic matter, and its composition is very complex. The mass concentration of COD can reach more than 350,000 mg / L. It contains some difficult-to-biodegrade and toxic and harmful substances, which has become a bottleneck problem in the development of "green development" and "energy saving and consumption reduction" of MTO devices, and has brought huge pressure on enterprises in environmental protection and water consumption.

[0005] Some MTO plants use recycling to return the concentrated water containing high concentrations of organic matter to the MTO reactor for reaction. However, these organic matter containing unsaturated bonds are prone to coking during the recycling process, resulting in reduced MTO catalyst activity and conversion rate. Therefore, it is of great practical significance to seek an efficient method to treat concentrated water.

[0006] Wuhan Textile University proposed a method for treating ultra-high concentration organic wastewater in the methanol to olefins process (CN201310644977.2). After the treatment process and corresponding conditions of demulsification and initial oil removal, alcohol and ketone stripping separation, secondary demulsification and oil removal, and high-efficiency adsorption, the COD in the ultra-high organic content concentrated water can be reduced from more than 100,000 mg / L to less than 3,000 mg / L, with a removal rate of more than 97%, which greatly reduces the total amount of pollutants discharged into the environment by MTO production, and ensures that the treated wastewater can directly enter the biochemical pool without affecting the biochemical performance of activated sludge. However, the invention focuses on harmless treatment of concentrated water, and does not recycle the organic matter in the concentrated water.

[0007] Shenhua Group Co., Ltd. provides a sewage treatment device for methanol to olefins process (CN201620127475.1), the sewage treatment device includes: a settling tank, provided with a wash water inlet and a sewage outlet; a sewage stripping tower, provided with a sewage inlet and a steam outlet, and the sewage inlet is connected to the sewage outlet on the settling tank; a sewage stripping tower top cooling device, provided with a steam inlet and a condensate outlet, and the steam inlet is connected to the steam outlet; a sewage stripping tower reflux tank, provided with a condensate inlet and a reflux outlet, and the condensate inlet is connected to the condensate outlet; the sewage treatment device also includes an oxide distillation tower, provided with a first reflux inlet and an oxide gas phase outlet, and the first reflux inlet is connected to the reflux outlet. The above-mentioned sewage treatment device can reduce the content of oxides in sewage, thereby effectively suppressing the COD discharge of sewage from exceeding the standard and improving the environmental protection of the methanol to olefins process. The patent mentions a process for further concentrating the concentrated water produced by the sewage stripping tower, but the oxide composition after concentration is complex and cannot be sold as a product, which reduces its added value.

[0008] Inner Mongolia Zhongmei Mengda New Energy Chemical Co., Ltd. (CN202021451125.3) discloses an MTO concentrated water recovery system, which includes an extraction distillation system, a light oil removal system and a refining system connected in sequence through pipelines; the extraction distillation system is used to extract the methanol-water mixture in the concentrated water; the light oil removal system is used to extract the light oil in the concentrated water; the refining system is used to extract acetone in the concentrated water. The MTO concentrated water recovery system provided by the utility model can separate acetone and light oil in the concentrated water to obtain chemical products that can be put into industrial use, while eliminating the problem of difficult treatment of concentrated water and improving the yield of the main product of the device. The patent proposes to further distill the MTO concentrated water to obtain an acetone product, but the process flow is long, the investment is high, and it is very difficult to obtain an industrial acetone product that meets national standards. Summary of the invention

[0009] In order to solve the problem of MTO concentrated water treatment, the present invention provides a method for treating MTO concentrated water, wherein the concentrated water is subjected to liquid phase hydrogenation, distillation and zeolite membrane dehydration to prepare a mixed alcohol product, and the technical index of the prepared mixed alcohol product is higher than the national standard "Alcohol-based liquid fuel GB16663-1996", and ethanol, isopropanol and 2-butanol products can be further separated, which not only solves the problem of MTO concentrated water treatment, but also increases its added value, achieving the purpose of improving quality and efficiency. The specific scheme is as follows:

[0010] A device for treating MTO concentrated water comprises a circulating hydrogenation unit and a dehydration unit; the circulating hydrogenation unit is used for hydrogenating the concentrated water to convert aldehydes, ketones and other substances contained therein into alcohols; the dehydration unit is used for dehydrating the liquid phase product after hydrogenation to obtain wastewater with low alcohol content and mixed alcohol with high alcohol content.

[0011] The circulating hydrogenation unit comprises a hydrogenation reactor 5, preferably the hydrogenation reactor 5 is a trickle bed reactor filled with a loaded nickel catalyst, and preferably the loaded nickel catalyst is a loaded catalyst with a high nickel content (nickel content ≥ 50wt%) and an activity higher than that of Raney nickel; the top raw material inlet of the hydrogenation reactor 5 is connected to the outlet end of the mixer 4 through a hydrogen-soluble raw material pipeline, and the inlet end of the mixer 4 is respectively connected to a hydrogen pipeline and a mixed liquid pipeline to supply hydrogen 102 and a mixed liquid composed of MTO concentrated water 101 and hydrogenation circulating liquid, i.e., a reactor feed 103, to the mixer 4; the mixed liquid pipeline A feed heater 3 is provided on it, which is used to heat the feed liquid during the start-up phase so that the feed liquid reaches the required temperature for hydrogenation; the inlet ends of the mixed liquid pipeline are respectively connected to the concentrated water pipe and the circulating liquid pipe, and the concentrated water pipe is sequentially provided with a raw material tank 1 and a raw material pump 2 along the flow direction of the concentrated water; the inlet end of the circulating liquid pipe is connected to the liquid outlet at the bottom of the hydrogenation reactor 5 to draw out part of the hot circulating liquid 105, and the circulating liquid pipe is provided with a circulating pump 6 and a circulating cooler 7, and the circulating cooler 7 is used to cool the hot circulating liquid 105 to form a cold circulating liquid 106, thereby removing the excess reaction heat generated during the hydrogenation process and maintaining the temperature of the reaction system.

[0012] A buffer chamber is provided below the catalyst packing layer in the hydrogenation reactor 5, and the liquid outlet is provided at the bottom of the buffer chamber. Meanwhile, a hydrogenation purge gas outlet is provided at the upper side wall of the buffer chamber. The gas-liquid mixture formed after the gas-liquid-solid three-phase reaction in the hydrogenation reactor 5 is subjected to preliminary gas-liquid separation in the buffer chamber, and is discharged from the liquid outlet at the bottom and the hydrogenation purge gas outlet on the side wall of the buffer chamber, respectively.

[0013] The circulating hydrogenation unit also includes a flash tank 8, which includes a gas phase inlet, a liquid phase inlet, a gas phase outlet and a liquid phase outlet, wherein the liquid phase inlet is connected to the liquid outlet of the hydrogenation reactor to lead out the hydrogenated liquid phase other than the hot circulating liquid 105, that is, the reactor discharge 104, and the gas phase inlet is connected to the hydrogenation purge gas outlet to lead out the reactor purge gas 107; the gas and liquid two phases drawn out from the hydrogenation reactor 5 enter the flash tank 8 and undergo the steps of expansion, decompression, sedimentation, etc., so that the pressurized liquid phase The gas dissolved in the liquid phase fully escapes, and the droplets entrained in the reactor purge gas 107 during rough separation are fully settled, thereby improving the separation effect of the gas-liquid two-phase; wherein the gas phase after flashing is discharged from the gas phase outlet at the top of the flash tank 8 as flash purge gas 108, and the gas phase outlet at the top of the flash tank 8 is connected to a purge gas condenser 10 and / or an adsorption device for removing and collecting organic components in the flash purge gas 108, and the liquid phase after flashing is discharged from the bottom outlet of the flash tank 8 as a hydrogenation product.

[0014] The dehydration unit includes a dehydration tower 11 and a zeolite membrane dehydration system 18; the dehydration tower 11 is a distillation tower, and the feed inlet in the middle is connected to the bottom outlet of the flash tank 8 through a product pipeline to receive the hydrogenation product discharged from the flash tank 8; a product pump 9 is arranged on the product pipeline.

[0015] The dehydration tower 11 is provided with a reboiler 15 and a drainage pipeline at the bottom, and a wastewater pump 16 and a wastewater cooler 17 are provided on the drainage pipeline for discharging wastewater 113; a condenser 12, a reflux tank 13 and a reflux pump 14 are provided at the top of the tower, wherein the outlet end of the reflux pump 14 is connected to the top of the dehydration tower 11 through a reflux pipe, and is connected to the feed port of the zeolite membrane dehydration system 18 through a membrane separation feed pipe; the permeate side outlet of the zeolite membrane dehydration system 18 is connected to the middle part of the dehydration tower through a permeate water pipe, so as to circulate the permeate water 112 that passes through the zeolite membrane back to the dehydration tower 11; the retentate side outlet of the zeolite membrane dehydration system 18 is used to discharge the mixed alcohol product 111.

[0016] A liquid phase distributor (not shown in the figure) is provided inside the hydrogenation reactor 5 above the catalyst packing layer to promote uniform distribution of the reaction stream on the cross section of the catalyst packing layer.

[0017] The dehydration method of the zeolite membrane dehydration system 18 is liquid phase dehydration or vapor phase dehydration, preferably liquid phase dehydration; the membrane component used is an inorganic zeolite membrane, preferably NaA membrane and / or CHA membrane. The zeolite membrane dehydration system 18 includes a built-in pump, a heat exchanger, a vacuum system, a zeolite membrane component and other equipment.

[0018] The present invention also provides a method for treating MTO concentrated water, comprising a circulating liquid phase hydrogenation step and a dehydration step; the concentrated water is prepared into a mixed alcohol product by liquid phase hydrogenation, distillation and zeolite membrane dehydration process, specifically comprising the following steps:

[0019] (1) The MTO concentrated water 101 raw material is pressurized by the raw material pump 2 and mixed with the hydrogenation circulating liquid pressurized by the circulating pump 6 to form the reactor feed 103, which is then introduced into the mixer 4 together with the hydrogen 102 to obtain the hydrogen-dissolving reaction stream, which is then introduced into the hydrogenation reactor 5;

[0020] (2) The hydrogen-dissolving reaction stream is evenly distributed on the catalyst packing in the hydrogenation reactor 5 under the action of the liquid phase distributor, and contacts and reacts with the catalyst in the process of passing downward through the packing layer. Aldehydes, ketones and other substances in the stream are converted into alcohols under the action of catalytic hydrogenation to obtain a mixture of mixed alcohols, water and excess hydrogen. After the mixture runs to the buffer chamber below the catalyst layer, it undergoes preliminary vapor-liquid separation, wherein the gas phase is discharged from the upper side wall of the buffer chamber as hydrogenation purge gas 107 and is sent to the flash tank 8, and the liquid phase is discharged from the bottom of the buffer chamber;

[0021] (3) The liquid phase discharged from the bottom of the buffer chamber is divided into two streams: one part is sent to the flash tank 8 as the reactor discharge 104, and the other part is circulated as the hydrogenation circulating liquid and mixed with the MTO concentrated water 101 to dilute the raw material concentration to reduce the adiabatic temperature rise of the hydrogenation reactor 5;

[0022] (4) treating the hydrogenation purge gas 107 and the reactor discharge 104 by low-pressure flash evaporation in a flash tank 8, discharging the flash purge gas 108 from the top of the flash tank 8, and discharging the hydrogenation product 109 from the bottom; wherein the flash purge gas 108 is treated by a purge gas condenser 10 and / or an adsorption device to remove and collect entrained organic matter; and the hydrogenation product 109 is pressurized by a product pump 9 and then sent to a dehydration tower 11;

[0023] (5) In the dehydration tower 11, the mixed alcohol and water are azeotropically distilled, and waste water 113 with low alcohol content is discharged at the bottom of the tower, and a water-containing mixed alcohol (water content 10-20 wt%) is obtained at the top of the tower. A part of the water-containing mixed alcohol is refluxed to the top of the dehydration tower 11, and the other part is sent to the zeolite membrane dehydration system 18 for further concentration and dehydration;

[0024] (6) In the zeolite membrane dehydration system 18, the water-containing mixed alcohol is brought into contact with the zeolite membrane assembly, and most of the water and a trace amount of the mixed alcohol pass through the zeolite membrane assembly to form permeate water 112, thereby reducing the water content in the intercepted mixed alcohol from about 10 to 20 wt% to about 2 wt%, thereby obtaining a mixed alcohol product 111, i.e., a retentate; the permeate water containing a trace amount of mixed alcohol is returned to the dehydration tower 11 for circulation treatment to reduce wastewater discharge and increase the yield of the mixed alcohol.

[0025] During the start-up phase, the MTO concentrated water 101 needs to be heated by the feed heater 3 to raise the temperature to the temperature required for the reaction; since the hydrogenation reaction process releases a lot of heat, when the device runs smoothly, the heating process of the feed heater 3 can be terminated, and the heat carried by the hydrogenation circulating fluid can be used to increase the temperature of the MTO concentrated water 101.

[0026] It should be pointed out that in the liquid phase hydrogenation step, the circulation ratio (ratio of hydrogenation circulating liquid to MTO concentrated water) adopted by the present invention is a large circulation ratio, specifically, the circulation ratio is 3 to 30: 1, preferably 3 to 10: 1. By using the circulation ratio provided by the present invention, a very high hydrogenation conversion rate (related to the purity of the final mixed alcohol product) can be maintained at a lower catalyst loading (or lower loading height), because the large circulation ratio can increase the linear velocity of the liquid in the bed of the hydrogenation reactor, making the liquid distribution more uniform, and the three-phase contact of the hydrogenation feedstock, hydrogen and catalyst more sufficient, thereby improving the hydrogenation conversion rate.

[0027] Although, a large circulation ratio will lead to an increase in energy consumption due to the increase in circulation flow, which is also the key reason why the prior art prefers to adopt a small circulation ratio. However, the inventors found that the large circulation ratio operation has the following advantages: First, it can reduce the loading height; and the reduction in loading height can effectively avoid the "wall flow" effect of the hydrogenation raw material when passing through the catalyst bed, thereby ensuring the effective and uniform contact between the hydrogenation raw material and the catalyst bed; second, it can dilute the concentration of the components to be hydrogenated in the hydrogenation raw material, thereby reducing the reaction intensity and the heating rate of the reactor; and the reduction in the heating rate can reduce the difficulty of regulating the reaction temperature on the one hand, and on the other hand, it can effectively reduce the temperature difference of the catalyst at different heights (in the prior art, due to the excessive heating rate, the catalyst at different positions has a large temperature difference, which is not conducive to the catalytic process), effectively ensuring the effective utilization of the catalyst.

[0028] Based on this discovery, the inventors found after a large number of experiments that when the circulation ratio is 3 to 30:1, especially 3 to 10:1, the above advantages brought about by the large circulation ratio operation can offset or even exceed the disadvantage of increased energy consumption due to increased circulation flow.

[0029] The hydrogenation circulating liquid must be cooled by a circulating cooler 7 to remove the heat accumulated by the hydrogenation reaction and maintain the normal temperature in the hydrogenation reactor 5 .

[0030] The present invention controls the hydrogen concentration in the hydrogenation reactor 5 by controlling the purge gas flow rate of the reactor.

[0031] The operating conditions of the liquid phase hydrogenation reactor 5 are 60 to 180° C. and 0.5 to 6.0 MPaG, preferably 100 to 150° C. and 1.0 to 4.0 MPaG.

[0032] The hydrogen-to-agent ratio (molar ratio of actual hydrogen to hydrogen required for hydrogenation of raw materials) of the liquid phase hydrogenation reactor 5 is relatively low, preferably 1 to 1.5:1, more preferably 1 to 1.2:1.

[0033] The operating pressure of the dehydration tower 11 is 0-0.1 MPaG, and the reflux ratio of the dehydration tower 11 is 0.5-5, preferably 1-2.

[0034] The dehydration method of the zeolite membrane dehydration system 18 is liquid phase dehydration or vapor phase dehydration, preferably liquid phase dehydration; the membrane component used in the zeolite membrane dehydration system is an inorganic zeolite membrane, preferably NaA membrane and CHA membrane.

[0035] Compared with the prior art, the main points of the present invention are:

[0036] (1) It is the first time to propose the coupling of liquid phase hydrogenation, distillation and zeolite membrane dehydration processes for the treatment of MTO concentrate;

[0037] (2) Using liquid phase hydrogenation to completely convert the aldehydes and ketones in the complex MTO concentrated water into alcohols, simplifying the composition of the MTO concentrated water, converting the concentrated water into aqueous mixed alcohols, and improving the yield of alcohols;

[0038] (3) reducing the water content of the mixed alcohol after liquid phase hydrogenation to 10-20 wt% through a dehydration tower;

[0039] (4) The water content of the mixed alcohol is further reduced to about 2% through a zeolite membrane dehydration system, thereby improving the quality of the mixed alcohol product.

[0040] The technical indicators of the mixed alcohol product obtained through the above coupling process are higher than the national standard "Alcohol-based liquid fuel GB16663-1996", and it can be further separated to obtain ethanol, isopropanol and 2-butanol products. It not only solves the problem of MTO concentrated water treatment, but also increases its added value, thereby achieving the purpose of improving quality and efficiency.

[0041] The purpose of the present invention is described in detail below with reference to the accompanying drawings and specific embodiments, but the accompanying drawings and embodiments do not constitute a limitation to the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 A schematic diagram of a method for treating MTO concentrated water.

[0043] Equipment in the figure: 1 is a raw material tank, 2 is a raw material pump, 3 is a feed heater, 4 is a mixer, 5 is a liquid phase hydrogenation reactor, 6 is a circulation pump, 7 is a circulation cooler, 8 is a flash tank, 9 is a product pump, 10 is a purge gas condenser, 11 is a dehydration tower, 12 is a condenser, 13 is a reflux tank, 14 is a reflux pump, 15 is a reboiler, 16 is a wastewater pump, 17 is a wastewater cooler, and 18 is a zeolite membrane dehydration system.

[0044] Pipelines in the figure: 101 is MTO concentrated water, 102 is hydrogen, 103 is reactor feed, 104 is reactor discharge, 105 is hot circulating liquid, 106 is cold circulating liquid, 107 is reactor purge gas, 108 is flash purge gas, 109 is hydrogenation product, 110 is aqueous mixed alcohol, 111 is mixed alcohol product, 112 is permeate water, and 113 is waste water.

[0045] Simplified codes in the figure: LS is low-pressure steam, CWS is circulating cooling water, and CHWS is low-temperature water. Specific implementation plan

[0046] Example 1

[0047] like Figure 1 Using a device and method for treating MTO concentrated water of the present invention, taking a 600,000 tons / year coal-to-olefins project as an example, the treatment capacity of by-product MTO concentrated water is 4 t / h.

[0048] (1) MTO concentrated water 101 first enters the raw material tank 1 for buffering, and then is pressurized to 2.2 MPaG by the raw material pump 2, mixed with the cold circulating liquid 106, and sent to the feed heater 3. After being heated to 113°C (the heater 3 is turned on during the start-up phase and can be turned off as needed after the system is operating normally), it is mixed with hydrogen 102 in the mixer 4 and enters the hydrogenation reactor 5. The reactor inlet temperature is 111°C.

[0049] (2) A liquid distributor is provided on the top of the hydrogenation reactor 5, and the hydrogenation purge gas 107 is sent to the flash tank 8 for separation and recovery of organic matter therein. Through the liquid phase hydrogenation reaction, the components in the raw material that need to be hydrogenated are basically hydrogenated completely.

[0050] (3) The liquid product of the hydrogenation reactor 5 is divided into two streams: one part is sent to the flash tank 8 as the reactor discharge 104, and the other part is circulated as the hydrogenation circulating liquid to dilute the feed concentration and reduce the adiabatic temperature rise of the reactor. The hydrogenation circulating liquid is first pressurized to 2.2 MPaG by the circulation pump 6, then sent to the circulation cooler 7 to be cooled to the operating temperature of 118°C, and then mixed with the MTO concentrated water 101.

[0051] (4) In the flash tank 8, low-pressure flash treatment is adopted to obtain a flash purge gas 108 and a hydrogenation product 109, wherein the flash purge gas 108 is sent to the outside after the organic matter therein is recovered through the purge gas condenser 10 and / or the adsorption device, and the hydrogenation product 109 (see Table 1, the water content is 68.39 wt%) is pressurized by the product pump 9 and sent to the dehydration tower 11.

[0052] (5) In the dehydration tower 11, the mixed alcohol and wastewater are subjected to azeotropic distillation, and the wastewater 113 with low alcohol content (see Table 1, alcohol content <0.2 wt%) is discharged from the bottom of the tower, and then pressurized by the wastewater pump 16, sent to the wastewater cooler 17 to be cooled to 40°C and then sent to the outside; the azeotropic components of the mixed alcohol and water reach the top of the tower and are condensed to obtain a water-containing mixed alcohol 110 (see Table 1, the water content is 16.93 wt%); the concentrated water-containing mixed alcohol 110 is obtained at the top of the dehydration tower 11, and then sent to the zeolite membrane dehydration system 18 for further concentration and dehydration.

[0053] (6) In the zeolite membrane dehydration system 18, the water in the aqueous mixed alcohol 110 is removed from about 16.93 wt% to 2 wt% to improve the quality of the mixed alcohol product, thereby obtaining a mixed alcohol product 111 and permeate water 112. The permeate water 112 containing a trace amount of mixed alcohol (see Table 1, the alcohol content is 5 wt%) is returned to the dehydration tower 11 for treatment.

[0054] Among them, the operating conditions of the raw material tank 1 are 0.2MPaG and 100°C; the operating pressure of the hydrogenation reactor 5 is 2.0MPaG, the feed temperature is 111°C, the adiabatic temperature rise of the reactor is 22°C, and the reactor outlet temperature is 133°C.

[0055] The circulation ratio (the flow ratio of the circulating liquid 105 to the raw material 101) used in this embodiment is 3:1, the hydrogen agent ratio (the molar ratio of the actual hydrogen to the hydrogen required for the hydrogenation of the raw material) of the hydrogenation reactor 5 is 1.2:1, and the hydrogen flow rate is 529.8Nm 3 The hydrogenation circulating liquid 105 has a flow rate of 12 t / h and is cooled from 133°C to 118°C by the circulating cooler 7.

[0056] The hydrogenation reactor 5 uses a supported nickel catalyst with a nickel content of 55 wt %, and the conversion rate of raw material aldehydes and ketones is ≥99%, and the alcohol selectivity is ≥99%.

[0057] The operating conditions of the flash tank 8 are 88°C and 0.05MPaG. The flow rate of the hydrogenation product 109 at the bottom of the flash tank 8 is 4.03t / h. The flash purge gas 108 is cooled to 20°C by the purge gas cooler 10. The liquid phase produced by the condensation returns to the flash tank 8. The flow rate of the cooled flash purge gas 108 is 92.2Nm 3 / h.

[0058] The vapor phase at the top of the dehydration tower is sent to the condenser 12 for condensation, and the condensed liquid is buffered in the reflux tank 13 and then pressurized by the reflux pump 14. The direct reflux flow accounts for 50%, with a flow rate of 1.55 t / h, and the flow rate to the zeolite membrane dehydration system 18 is 1.55 t / h.

[0059] The operating pressure at the top of the dehydration tower is 0.02MPaG, the operating temperature at the top of the tower is 86°C, and the operating temperature at the bottom of the tower is 110°C. The reboiler 15 of the dehydration tower uses 0.5MPaG saturated steam as a heat source, and the bottom wastewater 113 is pressurized by the wastewater pump 16 and then sent to the wastewater cooler 17 for cooling and then sent out of the boundary. The flow rate of wastewater 113 is 2.73t / h.

[0060] The zeolite membrane dehydration system 18 adopts liquid phase pervaporation dehydration mode, the feed rate is 1.55 / h, the water content of the raw material is 16.93wt%, and the water content of the mixed alcohol product 111 is 2wt%. The zeolite membrane dehydration system 18 adopts 5 stages of DN250 membrane components in series, and an interstage heater is provided between each 2 stages. The first two stages adopt CHA water-resistant membrane tubes, and the last 3 stages adopt NaA ordinary membrane tubes. The operating conditions of the membrane component feed are 130℃, 0.5MPaG, and the permeate side pressure is 5kPaA.

[0061] Through the above treatment, a high-quality mixed alcohol product (alcohol content of 97.8wt%) can be obtained. The product grade is higher than the indicator of the national standard "Alcohol-based liquid fuel GB16663-1996" (alcohol content ≥70wt%). The annual output of mixed alcohol products is about 10,400 tons. The mixed alcohol product can also be further separated to obtain ethanol, isopropanol and 2-butanol products.

[0062] Table 1 is the logistics data table of Example 1.

[0063] Table 1 Logistics data table of Example 1

[0064]

[0065]

[0066] Example 2

[0067] This embodiment relies on the same processing device and method as that of Embodiment 1, except that the circulation ratio used in the hydrogenation step of this embodiment is 10:1; the hydrogen-to-agent ratio is 1.5:1. According to calculations, the inlet temperature of the hydrogenation reactor 5 is 121°C, and the outlet temperature rises to 129°C, and its adiabatic temperature rise is reduced from 22°C in Embodiment 1 to 8°C.

[0068] Due to the increase in the average reaction temperature of the hydrogenation reactor 5, the total amount of aldehydes and ketones in the reactor discharge 104 is reduced from 0.06 wt% in Example 1 to 0.01 wt%.

[0069] Compared with Example 1, the hydrogen-to-agent ratio was changed from 1.2 to 1.5:1, which increased the hydrogen consumption by 132 Nm 3 / h, and at the same time, the flash evaporation gas flow rate was increased from 92.2Nm 3 / h increased to 227.9Nm 3 / h.

[0070] Table 2 is the logistics data table of Example 2.

[0071] Table 2 Logistics data table of Example 2

[0072]

[0073]

[0074] Example 3

[0075] This embodiment relies on the same processing device and method as in Example 1, except that the circulation ratio used in the hydrogenation step in this embodiment is 30:1. According to calculations, the inlet temperature of the hydrogenation reactor 5 is 126°C, and the outlet temperature rises to 129°C, and the adiabatic temperature rise is reduced from 22°C in Example 1 to 3°C.

[0076] Due to the increase in the average reaction temperature of the hydrogenation reactor 5, the total amount of aldehydes and ketones in the reactor discharge 104 is reduced from 0.06 wt% in Example 1 to 0 (aldehydes and ketones are almost completely reacted).

[0077] Compared with Example 1, since the hydrogen-to-agent ratio does not change, the hydrogen consumption and the flash evaporation gas are equivalent to those in Example 1.

[0078] Table 3 is the logistics data table of Example 3.

[0079] Table 3 Logistics data table of Example 3

[0080]

[0081]

Claims

1. A method for treating MTO concentrated water, preparing the concentrated water into a mixed alcohol product by circulating liquid phase hydrogenation and dehydration, characterized in that: The specific steps include: (1) MTO concentrated water (101) is mixed with hydrogenation circulating liquid to form reactor feed (103), which is then mixed with hydrogen (102) to obtain a hydrogen-dissolving reaction stream, which is then introduced into a hydrogenation reactor (5); (2) The hydrogen dissolving reaction stream is evenly distributed on the catalyst packing in the hydrogenation reactor (5), and contacts and reacts with the catalyst in the process of passing downward through the packing layer. The aldehyde and ketone components in the stream are converted into alcohols through catalytic hydrogenation to obtain a mixture consisting of mixed alcohols, water, and excess hydrogen; the mixture is subjected to preliminary gas-liquid separation to obtain a hydrogenation purge gas (107) and a liquid phase component; the hydrogenation purge gas (107) is sent to a flash tank (8), and the liquid phase component is discharged from the bottom of the hydrogenation reactor (5); (3) the liquid phase components discharged in step (2) are divided into two streams: one stream is sent to the flash tank (8) as the reactor discharge (104), and the other stream is circulated as the hydrogenation circulating liquid and mixed with the MTO concentrated water (101) to dilute the raw material concentration; (4) treating the hydrogenation purge gas (107) and the reactor discharge material (104) by low-pressure flash evaporation in a flash tank (8), discharging the flash evaporation gas (108) from the top of the flash tank (8), and discharging the hydrogenation product (109) from the bottom; the hydrogenation product (109) is pressurized by a product pump (9) and then sent to a dehydration tower (11); (5) In the dehydration tower (11), the mixed alcohol and water are azeotropically distilled, and waste water (113) with a low alcohol content is discharged at the bottom of the tower, and a water-containing mixed alcohol (110) is obtained at the top of the tower. A part of the water-containing mixed alcohol is refluxed to the top of the dehydration tower (11), and the other part is sent to the zeolite membrane dehydration system (18) for further concentration and dehydration; (6) In the zeolite membrane dehydration system (18), the water-containing mixed alcohol (110) is brought into contact with the zeolite membrane assembly, and most of the water and a trace amount of the mixed alcohol pass through the zeolite membrane assembly to form permeate water (112), thereby reducing the water content in the intercepted mixed alcohol from about 10-20wt% to about 2wt%, thereby obtaining a mixed alcohol product (111); the permeate water (112) is returned to the dehydration tower (11) for circulation treatment to reduce wastewater discharge and increase the yield of the mixed alcohol.

2. The method for treating MTO concentrated water according to claim 1, characterized in that: During the start-up phase, the MTO concentrated water (101) in step (1) is heated to the required temperature using a feed heater (3); the hydrogenation circulating liquid is cooled to a cold circulating liquid (106) using a circulating cooler (7) and then mixed with the MTO concentrated water (101) to remove excess reaction heat; the flash purge gas (108) is condensed through a purge gas condenser (10) to remove and collect entrained organic matter; and the hydrogen concentration in the hydrogenation reactor (5) is controlled by controlling the flow rate of the hydrogenation purge gas (107).

3. The method for treating MTO concentrated water according to claim 2, characterized in that: The circulation ratio adopted in the cyclic hydrogenation step is 3 to 30:1, preferably 3 to 10:

1.

4. The method for treating MTO concentrated water according to claim 2, characterized in that: The operating conditions of the hydrogenation reactor (5) are 60 to 180°C and 0.5 to 6.0 MPaG, preferably 100 to 150°C and 1.0 to 4.0 MPaG.

5. The method for treating MTO concentrated water according to claim 2, characterized in that: The hydrogen-to-agent ratio of the hydrogenation reactor (5) is 1 to 1.5:1, preferably 1 to 1.2:

1.

6. The method for treating MTO concentrated water according to claim 2, characterized in that: The operating pressure of the dehydration tower (11) is 0-0.1 MPaG, and the reflux ratio is 0.5-5, preferably 1-2.

7. The method for treating MTO concentrated water according to claim 2, characterized in that: The dehydration method of the zeolite membrane dehydration system (18) is liquid phase dehydration or vapor phase dehydration, preferably liquid phase dehydration; the membrane component used is an inorganic zeolite membrane, preferably NaA membrane and / or CHA membrane.

8. An MTO concentrated water treatment device, used for executing the treatment method according to any one of claims 1 to 7, comprising a circulating hydrogenation unit and a dehydration unit; the circulating hydrogenation unit comprises a hydrogenation reactor (5), the raw material inlet at the top of which is connected to the outlet end of a mixer (4) through a hydrogen-soluble raw material pipeline, the inlet end of the mixer (4) is respectively connected to a hydrogen pipeline and a mixed liquid pipeline to supply hydrogen (102) and a reactor feed (103) composed of MTO concentrated water (101) and hydrogenation circulating liquid to the mixer (4); the mixing A feed heater (3) is provided on the combined liquid pipeline; the inlet end of the mixed liquid pipeline is respectively connected to a concentrated water pipe and a circulating liquid pipe, and the concentrated water pipe is provided with a raw material tank (1) and a raw material pump (2); the inlet end of the circulating liquid pipe is connected to the liquid outlet at the bottom of the hydrogenation reactor (5); the circulating liquid pipe is provided with a circulating pump (6) and a circulating cooler (7); a catalyst packing layer is provided in the hydrogenation reactor (5), a buffer cavity is provided below the catalyst packing layer, the liquid outlet is provided at the bottom of the buffer cavity, and a hydrogenation purge gas outlet is provided on the upper side wall of the buffer cavity; The circulating hydrogenation unit also includes a flash tank (8), the side walls of which are respectively provided with a gas phase inlet connected to the hydrogenation purge gas outlet and a liquid phase inlet connected to the liquid outlet of the hydrogenation reactor; a gas phase outlet for discharging the flash purge gas (108) is provided at the top; a liquid phase outlet for discharging the hydrogenation product (109) is provided at the bottom; the gas phase outlet is connected to a purge gas condenser (10); The dehydration unit comprises a dehydration tower (11) and a zeolite membrane dehydration system (18); the dehydration tower (11) is a distillation tower, the feed inlet in the middle of which is connected to the bottom outlet of the flash tank (8) through a product pipeline, and the product pipeline is provided with a product pump (9); The dehydration tower (11) is provided with a reboiler (15) and a drainage pipeline at the bottom, and a condenser (12), a reflux tank (14) and a reflux pump (14) at the top, wherein the outlet end of the reflux pump (14) is connected to the top of the dehydration tower (11) through a reflux pipe, and is connected to the feed port of the zeolite membrane dehydration system (18) through a membrane separation feed pipe.

9. The MTO concentrated water treatment device according to claim 8, characterized in that: The drainage pipeline is provided with a wastewater pump (16) and a wastewater cooler (17); a liquid phase distributor is provided inside the hydrogenation reactor (5) above the catalyst packing layer; the permeate side outlet of the zeolite membrane dehydration system (18) is connected to the middle of the dehydration tower (11) through a permeate water pipe; and the retentate side outlet is used to discharge the mixed alcohol product (111).

10. The MTO concentrated water treatment device according to claim 9, characterized in that: The zeolite membrane dehydration system (18) comprises a built-in pump, a heat exchanger, a vacuum system and a membrane assembly; the membrane assembly is an inorganic zeolite membrane; the hydrogenation reactor (5) is a trickle bed reactor filled with a loaded nickel catalyst, and the loaded nickel catalyst is a high nickel loaded catalyst with a nickel content of ≥50wt%.

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