MTO concentrated water treatment device

Abstract

The utility model relates to an MTO (Methanol To Olefins) concentrated water treatment device, which 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, and most of water in the mixed alcohol is removed through flash evaporation degassing, azeotropic distillation and zeolite membrane dehydration treatment. According to the MTO concentrated water treatment device, a mixed alcohol product with low water content (about 2wt%) and waste water 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 utility model belongs to the technical field of chemical production, and in particular relates to a methanol to olefins (MTO) concentrated water treatment device, which is used for recycling the by-product concentrated water of the MTO device. Background Art

[0002] Driven by the country's abundant fossil resource endowment ("coal abundance, oil scarcity, and limited gas") and the continued strong consumption of downstream petrochemical products, modern coal chemical technology has developed rapidly, becoming a vital complement to the petrochemical industry. As a key component of modern coal chemical industry, coal-to-olefins (CTO) has seen rapid technological advancement and industrial development in recent years, expanding its market share and becoming the most economically profitable and fastest-growing branch of modern coal chemical industry. Continuously advancing CTO technology and high-quality industrial development is crucial for conserving precious petroleum resources, meeting growing demand for petrochemical products, and ensuring national energy security.

[0003] The process 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 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 involves the reaction of methanol with a catalyst to produce light olefins. This reaction produces light olefins, primarily ethylene and propylene, and water as a byproduct. Due to side reactions or trace amounts of unreacted methanol, the product also contains small amounts of oxygenates such as methanol, ethanol, butyraldehyde, acetone, butanone, and isopropanol. A small portion of these oxygenates enters the post-separation system with the product gas, where they are removed by water scrubbing. This water, after condensation and scrubbing with the reaction gas, enters the wastewater stripping tower, where organic matter is concentrated to create process wastewater known as concentrated water. This concentrated water, primarily composed of organic matter, is highly complex, with COD concentrations exceeding 350,000 mg / L. It also contains some persistently biodegradable and toxic substances, presenting a bottleneck in the "green development" and energy conservation efforts of MTO plants, placing significant pressure on companies in terms of environmental protection and water consumption.

[0005] Some MTO plants use recycling to process this concentrated water, which contains high concentrations of organic matter, back into the MTO reactor for further reaction. However, these organics containing unsaturated bonds are prone to coking during the recycling process, leading to reduced MTO catalyst activity and conversion rate. Therefore, finding an efficient method to treat this concentrated water is of great practical significance.

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

[0007] Shenhua Group Co., Ltd. provides a wastewater treatment device for a methanol-to-olefins (MTO) process (CN201620127475.1). The wastewater treatment device includes: a settling tank equipped with a wash water inlet and a wastewater outlet; a wastewater stripping tower equipped with a wastewater inlet and a steam outlet, the wastewater inlet communicating with the wastewater outlet on the settling tank; a wastewater stripping tower overhead cooling device equipped with a steam inlet and a condensate outlet, the steam inlet communicating with the steam outlet; a wastewater stripping tower reflux tank equipped with a condensate inlet and a reflux outlet, the condensate inlet communicating with the condensate outlet; and an oxide fractionation tower equipped with a first reflux inlet and an oxide vapor phase outlet, the first reflux inlet communicating with the reflux outlet. The wastewater treatment device can reduce the oxide content in wastewater, effectively suppressing excessive COD emissions from wastewater and improving the environmental performance of the MTO process. The patent mentions a process for further concentrating the concentrated water produced by the wastewater stripping tower. However, the oxide composition after concentration is complex and cannot be sold as a product, reducing 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 by 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; and 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 the 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 concentrated water treatment and improving the yield of the main product of the device. The patent proposes further distilling 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] To address the treatment issues of MTO concentrated water, this utility model provides a method for treating MTO concentrated water. This method uses liquid-phase hydrogenation, distillation, and zeolite membrane dehydration to produce a mixed alcohol product. The technical specifications of the prepared mixed alcohol product exceed those of the national standard "Alcohol-based Liquid Fuels GB16663-1996," and the product can be further separated to produce ethanol, isopropanol, and 2-butanol. This method not only addresses the treatment challenges of MTO concentrated water but also increases its added value, achieving the goal of improving quality and efficiency. The specific solution 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 to hydrogenate the concentrated water to convert aldehydes, ketones and other substances contained therein into alcohols; the dehydration unit is used to dehydrate the liquid phase product after hydrogenation to obtain wastewater with a low alcohol content and mixed alcohol with a high alcohol content.

[0011] The circulating hydrogenation unit includes a hydrogenation reactor 5, preferably a trickle bed reactor filled with a loaded nickel catalyst, preferably a loaded nickel catalyst having a high nickel content (nickel content ≥ 50 wt%) with 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 connected to a hydrogen pipeline and a mixed liquid pipeline respectively to supply hydrogen 102 and a mixed liquid composed of MTO concentrated water 101 and hydrogenation circulating liquid, i.e., 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 end of the mixed liquid pipeline is connected to the concentrated water pipe and the circulating liquid pipe respectively, and the concentrated water pipe is provided with a raw material tank 1 and a raw material pump 2 in sequence 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 by the hydrogenation process and maintaining the temperature of the reaction system.

[0012] A buffer chamber is provided in the hydrogenation reactor 5 below the catalyst packing layer, and the liquid outlet is provided at the bottom of the buffer chamber. At the same time, 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 undergoes 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 draw 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 draw 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 flash evaporation 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 the organic components in the flash purge gas 108, and the liquid phase after flash evaporation 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 port in the middle thereof 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 provided on the product pipeline.

[0015] The bottom of the dehydration tower 11 is provided with a reboiler 15 and a drainage pipeline, and the drainage pipeline is provided with a wastewater pump 16 and a wastewater cooler 17 for discharging wastewater 113; the top of the tower is provided with a condenser 12, a reflux tank 13 and a reflux pump 14, wherein the outlet end of the reflux pump 14 is connected to the top of the dehydration tower 11 through a reflux pipe and 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 of the dehydration tower through a permeate water pipe 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 zeolite membrane dehydration system 18 utilizes either liquid-phase or vapor-phase dehydration, preferably liquid-phase dehydration. The membrane components employed are inorganic zeolite membranes, preferably NaA and / or CHA membranes. The zeolite membrane dehydration system 18 includes a built-in pump, heat exchanger, vacuum system, and zeolite membrane components.

[0018] The utility model 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 through liquid phase hydrogenation, distillation and zeolite membrane dehydration processes, 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 circulation pump 6 to form the reactor feed 103, which is then introduced into the mixer 4 together with hydrogen 102 to obtain the hydrogen-dissolved 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. Substances such as aldehydes and ketones 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 subjected to azeotropic distillation, and wastewater 113 with a low alcohol content is discharged at the bottom of the tower. A hydrous mixed alcohol (water content 10-20 wt%) is obtained at the top of the tower. A portion of the hydrous mixed alcohol is refluxed to the top of the dehydration tower 11, and the other portion is sent to the zeolite membrane dehydration system 18 for further concentration and dehydration;

[0024] (6) In the zeolite membrane dehydration system 18, the aqueous 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 recycling treatment to reduce wastewater discharge and increase the yield of the mixed alcohol.

[0025] During the startup phase, the MTO concentrated water 101 needs to be heated by the feed heater 3 to reach 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 is important to note that in the liquid-phase hydrogenation step, the present invention employs a high circulation ratio (ratio of hydrogenation circulating liquid to MTO concentrated water), specifically a ratio of 3 to 30:1, preferably 3 to 10:1. This circulation ratio, as provided by the present invention, allows for maintaining an extremely high hydrogenation conversion rate (which is related to the purity of the final mixed alcohol product) at a relatively low catalyst loading (or relatively low loading height). This is because a high circulation ratio increases the linear velocity of the liquid in the hydrogenation reactor bed, resulting in more uniform liquid distribution and more complete three-phase contact between the hydrogenation feedstock, hydrogen, and catalyst, 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 a small circulation ratio is preferred in the prior art, the inventors have found that the large circulation ratio operation has the following advantages: First, it can reduce the filling height; and the reduction in the filling height can effectively avoid the "wall flow" effect of the hydrogenation feedstock when passing through the catalyst bed, thereby ensuring effective and uniform contact between the hydrogenation feedstock and the catalyst bed; second, it can dilute the concentration of the components to be hydrogenated in the hydrogenation feedstock, thereby reducing the reaction intensity and the heating rate of the reactor; and the reduction in the heating rate can, on the one hand, reduce the difficulty of regulating the reaction temperature, and on the other hand, 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-mentioned advantages brought by the large circulation ratio operation can offset or even exceed the disadvantage of increased energy consumption due to the increase in circulation flow.

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

[0030] The utility model 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 60-180° C. and 0.5-6.0 MPaG, preferably 100-150° C. and 1.0-4.0 MPaG.

[0032] The hydrogen-to-agent ratio (the molar ratio of actual hydrogen to hydrogen required for hydrogenation of the raw material) 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 mode 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 utility model are:

[0036] (1) For the first time, the coupling of liquid phase hydrogenation, distillation and zeolite membrane dehydration processes was proposed for the treatment of MTO concentrate water;

[0037] (2) Liquid-phase hydrogenation is used 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-mentioned 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 will be described in detail below with reference to the accompanying drawings and specific embodiments, but the accompanying drawings and embodiments do not limit the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[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 the MTO concentrated water treatment device and method of the utility model, taking a 600,000 tons / year coal-to-olefins project as an example, the by-product MTO concentrated water treatment capacity is 4t / h.

[0048] (1) MTO concentrated water 101 first enters the raw material tank 1 for buffering, is then 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 the 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 from hydrogenation reactor 5 is split into two streams: one portion is sent to flash tank 8 as reactor discharge 104, and the other portion is circulated as 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 circulation pump 6, then sent to circulation cooler 7 to be cooled to the operating temperature of 118°C, and then mixed with MTO concentrated water 101.

[0051] (4) In the flash tank 8, low-pressure flash evaporation is performed to obtain a flash purge gas 108 and a hydrogenation product 109. 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, with a water content of 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 a low alcohol content (see Table 1, alcohol content <0.2 wt%) is discharged from the bottom of the tower, pressurized by the wastewater pump 16, sent to the wastewater cooler 17 for cooling to 40°C, and then sent out of the tower; the azeotropic components of the mixed alcohol and water reach the top of the tower and are condensed to obtain a hydrous mixed alcohol 110 (see Table 1, water content is 16.93 wt%); the concentrated hydrous mixed alcohol 110 is obtained at the top of the dehydration tower 11 and 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 0.2 MPaG and 100°C; the operating pressure of the hydrogenation reactor 5 is 2.0 MPaG, the feed temperature is 111°C, the reactor adiabatic temperature rise 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 0.05 MPaG. The flow rate of the hydrogenated product 109 at the bottom of the flash tank 8 is 4.03 t / h. The flash vent gas 108 is cooled to 20°C by the vent gas cooler 10. The condensed liquid phase returns to the flash tank 8. The flow rate of the cooled flash vent gas 108 is 92.2 Nm 3 / h.

[0058] The vapor phase from 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 dehydration tower's top operating pressure is 0.02 MPaG, the top operating temperature is 86°C, and the bottom operating temperature is 110°C. The dehydration tower's reboiler 15 uses 0.5 MPaG saturated steam as its heat source. The bottom wastewater 113 is pressurized by wastewater pump 16 and then sent to wastewater cooler 17 for cooling before being discharged. The wastewater 113 flow rate is 2.73 t / h.

[0060] Zeolite membrane dehydration system 18 utilizes liquid-phase pervaporation dehydration, with a feed rate of 1.55 mL / h. The feedstock has a moisture content of 16.93 wt%, and the mixed alcohol product 111 has a moisture content of 2 wt%. Zeolite membrane dehydration system 18 utilizes five DN250 membrane modules connected in series, with interstage heaters installed between each two stages. The first two stages utilize CHA water-resistant membrane tubes, while the last three stages utilize NaA standard membrane tubes. The membrane module feed operating conditions are 130°C, 0.5 MPaG, and a permeate pressure of 5 kPaA.

[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 the mixed alcohol product 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 example utilizes the same processing apparatus and method as Example 1, differing in that the hydrogenation step utilizes a recycle ratio of 10:1 and a hydrogen-to-agent ratio of 1.5:1. Calculations show that the inlet temperature of hydrogenation reactor 5 is 121°C, while the outlet temperature rises to 129°C, reducing the adiabatic temperature rise from 22°C in Example 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, while 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 example utilizes the same processing apparatus and method as Example 1, except that a 30:1 recycle ratio is used in the hydrogenation step. Calculations show that the inlet temperature of hydrogenation reactor 5 is 126°C, while the outlet temperature rises to 129°C, reducing the adiabatic temperature rise 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. An MTO concentrated water treatment device, characterized in that: The invention comprises 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 the hydrogenation reactor is connected to the outlet of the mixer (4) through a hydrogen-soluble raw material pipeline, the inlet 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); a feed heater (3) is provided on the mixed liquid pipeline; the inlet of the mixed liquid pipeline is respectively connected to a concentrated water pipe and a circulating liquid pipe, the concentrated water pipe is provided with a raw material tank (1) and a raw material pump (2); the inlet 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 chamber is provided below the catalyst packing layer, the liquid outlet is provided at the bottom of the buffer chamber, and a hydrogenation purge gas outlet is provided on the upper side wall of the buffer chamber; The circulating hydrogenation unit further comprises 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 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 (13) 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.

2. The MTO concentrated water treatment device according to claim 1, characterized in that: 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 ≥50 wt%.

3. The MTO concentrated water treatment device according to claim 2, characterized in that: A liquid phase distributor is provided inside the hydrogenation reactor (5) above the catalyst packing layer.

4. The MTO concentrated water treatment device according to claim 3, characterized in that: The drainage pipeline is provided with a wastewater pump (16) and a wastewater cooler (17).

5. The MTO concentrated water treatment device according to claim 4, characterized in that: 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; the retentate side outlet is used to discharge the mixed alcohol product (111).

6. The MTO concentrated water treatment device according to claim 5, characterized in that: The zeolite membrane dehydration system (18) comprises a built-in pump, a heat exchanger, a vacuum system and a membrane component; the membrane component is an inorganic zeolite membrane.

Images