A method and system for treating organic wastewater from ethanol dehydration to ethylene production.

Abstract

This invention relates to the field of chemical process treatment technology, and discloses a method and system for treating organic wastewater from ethanol dehydration to ethylene production. The invention first hydrogenates a mixed solution containing ethanol, diethyl ether, and acetaldehyde, converting acetaldehyde in the mixed solution into ethanol, effectively avoiding the impact of acetaldehyde accumulation on the dehydration catalyst. Then, the overhead gas from the stripping tower is collected to recover ethanol and diethyl ether from the aqueous phase, with recovery rates reaching over 99 wt%. This invention employs a "hydrogenation reaction + stripping" technology, effectively recovering and reusing ethanol and diethyl ether from the aqueous phase. It solves the problems of difficulty in separating the ternary azeotrope of diethyl ether, acetaldehyde, and water through distillation, acetaldehyde in the recovered product causing deactivation of the dehydration catalyst, and the high energy consumption caused by the need for condensation followed by vaporization of the recovered product.

Description

Technical Field

[0001] This invention relates to the field of chemical process treatment technology, specifically to a method and system for treating organic wastewater from ethanol dehydration to ethylene production. Background Technology

[0002] Ethylene is an important basic raw material for petrochemicals, mainly used to produce various organic chemical products such as polyethylene, polyvinyl chloride, ethylene oxide and ethylene glycol, ethylbenzene and styrene, and vinyl acetate. Currently, the most common ethylene production process involves naphtha steam cracking. With the increasing depletion of petroleum resources and the resulting environmental problems, the production of ethylene from ethanol dehydration has attracted widespread attention due to its renewable feedstock and low emissions.

[0003] The reaction products for the dehydration of ethanol to produce ethylene contain ethanol, diethyl ether, and acetaldehyde. If these products are directly introduced into the wastewater treatment plant outside the system without treatment, on the one hand, the organic matter in the wastewater, especially ethanol and diethyl ether, will not be utilized as a resource, leading to increased ethanol consumption. On the other hand, the high concentration of organic matter in the wastewater increases the difficulty of wastewater treatment and the corresponding increase in treatment costs. Existing technology discloses a method for treating organic wastewater from ethanol dehydration to ethylene production. This method involves feeding the organic wastewater into a distillation column, where a gaseous stream containing ethanol, diethyl ether, ethylene, and C3 and higher hydrocarbons is separated at the top of the column. This gaseous stream then enters a condenser, and after condensation, it enters a gas-liquid separator. A portion of the resulting liquid phase is returned to the distillation column, while the remainder is collected. The organic matter content of the aqueous stream discharged from the bottom of the column is ≤20 ppm. This method is simple and requires low investment, reducing the organic matter concentration in the wastewater from 0.265% to below 20 ppm. However, the stream collected at the top of the column returning to the reactor is prone to coking, clogging the catalyst pores and reducing catalyst activity. Furthermore, since this stream is liquid, it requires pump pressurization and regasification before returning to the reactor, consuming additional steam. Additionally, the condenser at the top of the column consumes circulating water, resulting in high energy consumption.

[0004] Therefore, how to adjust and optimize the treatment method for organic wastewater from ethanol dehydration to ethylene production in order to avoid reactor coking and reduce energy consumption is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] In view of this, the present invention provides a method for treating organic wastewater from ethanol dehydration to ethylene production, in order to solve the problems of reactor coking and high energy consumption in the prior art.

[0006] In a first aspect, the present invention provides a method for treating organic wastewater from ethanol dehydration to ethylene production, comprising the following steps: (1) Ethylene is prepared from ethanol under the action of a catalyst, and a mixture containing ethanol, diethyl ether and acetaldehyde is collected after separation. (2) The mixture containing ethanol, ether, and acetaldehyde is hydrogenated, and the resulting hydrogenated product is stripped and the overhead gas is collected and returned to step (1) as raw material.

[0007] In one optional embodiment, the hydrogenation product includes a gas-phase hydrogenation product and a liquid-phase hydrogenation product, and further includes absorption treatment of the gas-phase hydrogenation product, followed by pressurization and stripping treatment of the absorbed gas-phase hydrogenation product and the liquid-phase hydrogenation product.

[0008] It should be noted that the present invention can recover diethyl ether in the hydrogenation tail gas by absorbing the gas-phase hydrogenation products, thereby reducing its loss.

[0009] In one optional embodiment, the absorption treatment temperature is 10°C-25°C.

[0010] In one alternative embodiment, the absorbent in the absorption treatment includes ethanol.

[0011] In an optional embodiment, the gas at the top of the column is pressurized to 1.0 MPaG-1.5 MPaG and then heat-exchanged with liquid ethanol before being separated into gas and liquid phases. The resulting gas phase is then returned to step (1).

[0012] It should be noted that the heat exchange between the pressurized gas at the top of the column and the ethanol is a direct heat exchange.

[0013] In one optional embodiment, the stripping unit has 15-50 theoretical plates; the top temperature is 100℃-156℃, and the pressure is 0.05MPaG-0.5MPaG; the bottom temperature is 110℃-162℃, and the pressure is 0.06MPaG-0.55MPaG.

[0014] In one alternative embodiment, the mixture containing ethanol, diethyl ether, and acetaldehyde further includes a cooling step before hydrogenation treatment.

[0015] In one optional embodiment, the hydrogenation treatment is carried out at a temperature of 20°C-60°C and a pressure of 0.1 MPaG-1 MPaG.

[0016] In a second aspect, the present invention provides a system for treating organic wastewater from the ethanol dehydration to ethylene production method described in the first aspect, comprising: a reaction device, a separation device, a hydrogenation device, and a stripping device connected in sequence, wherein the top outlet of the stripping device is connected to the inlet of the reaction device.

[0017] In an alternative embodiment, an absorption device is also included, the inlet of which is connected to the gas phase outlet of the hydrogenation device. The collection device has its inlet connected to the outlet of the absorption device and the liquid phase outlet of the hydrogenation device, respectively. The first compression device has its inlet connected to the outlet of the collection device, and its outlet connected to the inlet of the stripping device.

[0018] In an alternative embodiment, a second compression device is further included, the inlet of which is connected to the top outlet of the stripping device. The heat exchanger has its inlet connected to the outlet of the second compression unit and the outlet of the ethanol storage tank, respectively. The gas-liquid separation device has its inlet connected to the outlet of the heat exchange device, and its gas phase outlet connected to the inlet of the reaction device.

[0019] In one alternative embodiment, a cooling device is provided, the inlet of which is connected to the outlet of the separation device, and the outlet of which is connected to the inlet of the hydrogenation device.

[0020] Compared with the prior art, the technical solution of the present invention has the following advantages: 1. The present invention provides an organic wastewater treatment method for ethanol dehydration to produce ethylene, comprising the following steps: (1) ethylene is prepared from ethanol as raw material under the action of a catalyst, and a mixture containing ethanol, ether, and acetaldehyde is collected after separation; (2) the mixture containing ethanol, ether, and acetaldehyde is hydrogenated, and the hydrogenated product is stripped and the overhead gas is collected as raw material and returned to step (1).

[0021] The inventors discovered that the aforementioned mixture contains acetaldehyde, which readily polymerizes into coke particles at high temperatures, clogging the pores and active sites of the dehydration catalyst. Therefore, this invention first hydrogenates the mixture containing ethanol, diethyl ether, and acetaldehyde, converting the acetaldehyde into ethanol, effectively preventing the accumulation of acetaldehyde from affecting the dehydration catalyst. Then, the overhead gas from the stripping tower is collected to recover ethanol and diethyl ether from the aqueous phase, achieving a recovery rate of over 99 wt%. This invention employs a "hydrogenation reaction + stripping" technology to effectively recover and reuse ethanol and diethyl ether from the aqueous phase, solving the problems of acetaldehyde in the recovered product causing catalyst deactivation and the high energy consumption resulting from the need for condensation followed by vaporization of the recovered product. Attached Figure Description

[0022] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0023] Figure 1 This is the organic wastewater treatment system for ethanol dehydration to ethylene production in this embodiment of the invention; Figure 2 This is the organic wastewater treatment system for ethanol dehydration to ethylene production in Comparative Example 1 of the present invention; Explanation of reference numerals in the attached figures: 1. Reaction apparatus; 2. Separation apparatus; 3. Acetaldehyde cooler; 4. Mixing apparatus; 5. Acetaldehyde hydrogenation reactor; 6. Acetaldehyde hydrogenation collection tank; 7. Absorption apparatus; 8. Collection pump; 9. Recovery tower; 10. Compressor; 11. Heat exchanger; 12. Gas-liquid separator; 13. Ethanol storage tank; 14. Distillation tower; 15. Top condenser; 16. Top reflux tank; 17. Reflux pump. Detailed Implementation

[0024] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0025] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0026] To address the problems existing in the aforementioned related technologies, according to a first aspect of the present invention, a method for treating organic wastewater from ethanol dehydration to ethylene production is provided, comprising the following steps: (1) Ethylene is prepared from ethanol under the action of a catalyst, and a mixture containing ethanol, diethyl ether and acetaldehyde is collected after separation. (2) The mixture containing ethanol, ether, and acetaldehyde is hydrogenated, and the resulting hydrogenated product is stripped and the overhead gas is collected and returned to step (1) as raw material.

[0027] In one optional embodiment, the hydrogenation product includes a gas-phase hydrogenation product and a liquid-phase hydrogenation product, and further includes absorption treatment of the gas-phase hydrogenation product, followed by pressurization and stripping treatment of the absorbed gas-phase hydrogenation product and the liquid-phase hydrogenation product.

[0028] In one optional embodiment, the absorption treatment temperature is 10°C-25°C.

[0029] In one alternative embodiment, the absorbent in the absorption treatment includes ethanol.

[0030] In an optional embodiment, the gas at the top of the column is pressurized to 1.0 MPaG-1.5 MPaG and then heat-exchanged with liquid ethanol before being separated into gas and liquid phases. The resulting gas phase is then returned to step (1).

[0031] In one optional embodiment, the stripping unit has 15-50 theoretical plates; the top temperature is 100℃-156℃, and the pressure is 0.05MPaG-0.5MPaG; the bottom temperature is 110℃-162℃, and the pressure is 0.06MPaG-0.55MPaG.

[0032] In one alternative embodiment, the mixture containing ethanol, diethyl ether, and acetaldehyde further includes a cooling step before hydrogenation treatment.

[0033] It should be noted that circulating water is used for cooling, and the temperature of the circulating water is 18℃-23℃.

[0034] In one optional embodiment, the hydrogenation treatment is carried out at a temperature of 20°C-60°C and a pressure of 0.1 MPaG-1 MPaG.

[0035] In a second aspect, the present invention provides a system for treating organic wastewater from the ethanol dehydration to ethylene production method described in the first aspect, comprising: a reaction unit, a separation unit, a hydrogenation unit, and a stripping unit connected in sequence, wherein the top outlet of the stripping unit is connected to the inlet of the reaction unit.

[0036] In an alternative embodiment, an absorption device is also included, the inlet of which is connected to the gas phase outlet of the hydrogenation device. The collection device has its inlet connected to the outlet of the absorption device and the liquid phase outlet of the hydrogenation device, respectively. The first compression device has its inlet connected to the outlet of the collection device, and its outlet connected to the inlet of the stripping device.

[0037] In an alternative embodiment, a second compression device is further included, the inlet of which is connected to the top outlet of the stripping device. The heat exchanger has its inlet connected to the outlet of the second compression unit and the outlet of the ethanol storage tank, respectively. The gas-liquid separation device has its inlet connected to the outlet of the heat exchange device, and its gas phase outlet connected to the inlet of the reaction device.

[0038] In one alternative embodiment, a cooling device is provided, the inlet of which is connected to the outlet of the separation device, and the outlet of which is connected to the inlet of the hydrogenation device.

[0039] It should be noted that in step (1) of this invention, the hydrogenation catalyst is a nickel-based catalyst with alumina support, a nickel content of 52 wt%, and a bulk density of 600 kg / m³. 3 The particle diameter is 2mm.

[0040] The present invention will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed by the present invention.

[0041] Example 1 like Figure 1 As shown, this embodiment provides an organic wastewater treatment system for ethanol dehydration to ethylene production, including: a reaction device 1, a separation device 2, an acetaldehyde cooler 3, a mixing device 4, an acetaldehyde hydrogenation reactor 5, an acetaldehyde hydrogenation collection tank 6, a collection pump 8, a recovery tower 9, a compressor 10, a heat exchanger 11, and a gas-liquid separator 12 connected in sequence, with the outlet of the gas-liquid separator 12 connected to the inlet of the reaction device 1. The inlet of the acetaldehyde hydrogenation collection tank 6 is connected to the liquid phase outlet of the acetaldehyde hydrogenation reactor 5; The absorption device 7 has its inlet connected to the gas phase outlet of the acetaldehyde hydrogenation reactor 5 and its liquid phase outlet connected to the inlet of the acetaldehyde hydrogenation collection tank 6. The outlet of the ethanol storage tank 13 is connected to the inlet of the heat exchanger 11 and the gas-liquid separator 12, respectively.

[0042] Example 2 like Figure 1 As shown in the figure, this embodiment provides a method for treating organic wastewater from ethanol dehydration to ethylene production, including the following steps: (1) Under the action of a dehydration catalyst, ethanol is used as raw material to prepare ethylene-containing reaction gas by dehydration. After gas-liquid separation, ethylene-containing gas product and a mixed solution containing ethanol, diethyl ether and acetaldehyde are obtained (the contents of acetaldehyde, ethanol and diethyl ether are 0.28wt%, 6.10wt% and 12.38wt%, respectively). (2) The mixed solution is transported to an acetaldehyde cooler for cooling to obtain a gas-liquid mixed product. The flow rate of the mixed solution is 102110 kg / h, the temperature is 111℃, and the pressure is 0.76 MPaG. Then, in the presence of a nickel-based catalyst, it is mixed with 181 kg / h of hydrogen and enters the acetaldehyde hydrogenation reactor. The reaction temperature is 40℃, the pressure is 0.7 MPaG, and the allowable pressure drop is 30 kPa. The liquid phase reaction product is then stored in an acetaldehyde hydrogenation collection tank. The temperature of the acetaldehyde hydrogenation collection tank is 40℃ and the pressure is 0.63 MPaG. The gas phase hydrogenation product is absorbed and treated in the acetaldehyde hydrogenation tail gas condenser to recover ethanol and diethyl ether in the gas phase and then stored in the acetaldehyde hydrogenation collection tank. The unabsorbed gas is discharged. The absorbent is ethanol, the absorption temperature is 20℃, and the heat load of the acetaldehyde hydrogenation tail gas condenser is 132 kW. (3) Then, a collection pump is used to send the mixture in the acetaldehyde hydrogenation collection tank to the ethanol / ether recovery tower for stripping. The theoretical number of trays in the ethanol / ether recovery tower is 20, the top operating temperature is 108℃, the pressure is 0.05MPaG, and the bottom operating temperature is 118℃, the pressure is 0.08MPaG. The top gas and bottom liquid are obtained. The top gas is a mixture of 78450kg / h ethanol, ether and water, and the bottom liquid is 29056kg / h wastewater without ethanol and ether. The top gas is pressurized to 1.3MPaG and sent to the heat exchanger to react with the acetaldehyde hydrogenation collection tank. Liquid ethanol undergoes direct heat exchange, vaporizing it into gaseous ethanol. This gaseous ethanol, along with the liquid ethanol vaporized by the medium-pressure steam in the feed evaporator, enters the feed gas-liquid separator and is then used as raw material in the reactor of step (1). In this embodiment, the ethanol and diethyl ether recovery rates are 99.38 wt%. No condenser is installed at the top of the recovery tower, eliminating the need for circulating water. The feed evaporator (not shown in the figure) provides 5.7214 MW of heat using medium-pressure steam. The ethanol / diethyl ether recovery tower operates at a lower pressure, requiring no medium-pressure steam and relying solely on the mixture for heat. The process is simple, easy to control, and consumes little energy.

[0043] Example 3 This embodiment provides a method for treating organic wastewater from ethanol dehydration to ethylene production, comprising the following steps: (1) Under the action of a dehydration catalyst, ethanol is used as raw material to prepare ethylene-containing reaction gas by dehydration. After gas-liquid separation, ethylene-containing gas product and a mixed solution containing ethanol, diethyl ether and acetaldehyde are obtained (the contents of acetaldehyde, ethanol and diethyl ether are 0.29wt%, 6.21wt% and 12.28wt%, respectively). (2) The mixed solution is transported to an acetaldehyde cooler for cooling to obtain a gas-liquid mixed product. The flow rate of the mixed solution is 102056 kg / h, the temperature is 123.6℃, ​​and the pressure is 1.08 MPaG. Then, in the presence of a nickel-based catalyst, it is mixed with 181 kg / h of hydrogen and enters the acetaldehyde hydrogenation reactor. The reaction temperature is 30℃, the pressure is 1 MPaG, and the allowable pressure drop is 50 kPa. The liquid phase reaction product is then stored in an acetaldehyde hydrogenation collection tank. The temperature of the acetaldehyde hydrogenation collection tank is 30.3℃ and the pressure is 0.87 MPaG. The gas phase hydrogenation product is absorbed and treated in the acetaldehyde hydrogenation tail gas condenser to recover ethanol and diethyl ether in the gas phase and then stored in the acetaldehyde hydrogenation collection tank. The unabsorbed gas is discharged. The absorbent is ethanol, the absorption temperature is 10℃, and the heat load of the acetaldehyde hydrogenation tail gas condenser is 63.7 kW. (3) Then, the mixture in the acetaldehyde hydrogenation collection tank is sent to the ethanol / ether recovery tower for stripping using a collection pump. The theoretical number of trays in the ethanol / ether recovery tower is 30, the top operating temperature is 134.6℃, the pressure is 0.25MPaG, and the bottom operating temperature is 142.7℃, the pressure is 0.29MPaG. The top gas and bottom liquid are obtained. The top gas is a mixture of 78450kg / h of ethanol, ether and water, and the bottom liquid is 29016kg / h of wastewater without ethanol and ether. The top gas is pressurized to 1.5MPaG. aG is fed into a heat exchanger to directly exchange heat with liquid ethanol, vaporizing the liquid ethanol into gaseous ethanol. Then, together with the liquid ethanol vaporized by medium-pressure steam, it enters the feed gas-liquid separator as raw material and enters the reactor in step (1). In this embodiment, the recovery rate of ethanol and diethyl ether is 99.70 wt%. The top of the recovery tower is not equipped with a condenser and does not require the consumption of circulating water. The feed evaporator uses medium-pressure steam to provide heat of 7.8374 MW, and the reboiler of the ethanol / diethyl ether recovery tower requires medium-pressure steam to provide heat of 18.6084 MW.

[0044] Example 4 This embodiment provides a method for treating organic wastewater from ethanol dehydration to ethylene production, comprising the following steps: (1) Under the action of a dehydration catalyst, ethanol is used as raw material to prepare ethylene-containing reaction gas by dehydration. After gas-liquid separation, ethylene-containing gas product and a mixed solution containing ethanol, diethyl ether and acetaldehyde are obtained (the contents of acetaldehyde, ethanol and diethyl ether are 0.31wt%, 6.48wt% and 13.14wt%, respectively). (2) The mixed solution is transported to an acetaldehyde cooler for cooling to obtain a gas-liquid mixed product. The flow rate of the mixed solution is 96261 kg / h, the temperature is 108.4℃, and the pressure is 0.644 MPaG. Then, under the action of a nickel-based catalyst, it is mixed with 181 kg / h of hydrogen and enters the acetaldehyde hydrogenation reactor. The reaction temperature is 50℃, the pressure is 0.1 MPaG, and the allowable pressure drop is 50 kPa. The liquid phase reaction product is then stored in an acetaldehyde hydrogenation collection tank. The temperature of the acetaldehyde hydrogenation collection tank is 34.6℃ and the pressure is 0.02 MPaG. The gas phase hydrogenation product is absorbed and treated in the acetaldehyde hydrogenation tail gas condenser to recover ethanol and diethyl ether in the gas phase and then stored in the acetaldehyde hydrogenation collection tank. The unabsorbed gas is discharged. The absorbent is ethanol, the absorption temperature is 25℃, and the heat load of the acetaldehyde hydrogenation tail gas condenser is 2406 kW. (3) Then, the mixture in the acetaldehyde hydrogenation collection tank is sent to the ethanol / ether recovery tower for stripping using a collection pump. The theoretical number of plates in the ethanol / ether recovery tower is 50, the top operating temperature is 154.1℃, the pressure is 0.5MPaG, and the bottom operating temperature is 161.4℃, the pressure is 0.55MPaG. The top gas and bottom liquid are obtained. The top gas is a mixture of 70450kg / h ethanol, ether and water, and the bottom liquid is 28350kg / h wastewater without ethanol and ether. The top gas is pressurized to 1MPa. G is fed into a heat exchanger to directly exchange heat with liquid ethanol, vaporizing the liquid ethanol into gaseous ethanol. Then, together with the liquid ethanol vaporized by medium-pressure steam, it enters the feed gas-liquid separator and is then used as raw material to enter the reactor in step (1). In this embodiment, the recovery rate of ethanol and diethyl ether is 84.32%. The top of the recovery tower is not equipped with a condenser and does not require the consumption of circulating water. The feed evaporator uses medium-pressure steam to provide 12.7994MW of heat, and the reboiler of the ethanol / diethyl ether recovery tower requires medium-pressure steam to provide 43.7805MW of heat.

[0045] Example 5 This embodiment provides a method for treating organic wastewater from ethanol dehydration to ethylene, which is basically the same as the steps in Example 4, except that the absorption treatment of the acetaldehyde hydrogenation tail gas condenser is omitted; in this comparative example, the recovery rate of ethanol and diethyl ether is 76.82%.

[0046] Comparative Example 1 like Figure 2 As shown, this comparative example provides an organic wastewater treatment system for ethanol dehydration to ethylene production, comprising: a reaction device 1, a separation device 2, a distillation column 14, and a gas-liquid separation device 12 connected in sequence. The top condenser 15 is connected at its inlet to the top outlet of the distillation column 14; The top reflux tank 16 has its inlet connected to the outlet of the top condenser 15. The reflux pump 17 has its inlet connected to the outlet of the top reflux tank 16, and its outlet connected to the inlet of the distillation column 14 and the inlet of the gas-liquid separator 12, respectively. The inlet of the ethanol storage tank 13 is connected to the inlet of the gas-liquid separation device 12.

[0047] This comparative example provides a method for treating organic wastewater from ethanol dehydration to ethylene production, comprising the following steps: (1) Under the action of a dehydration catalyst, ethanol is used as raw material to prepare ethylene-containing reaction gas by dehydration. After gas-liquid separation, ethylene-containing gas product and a mixed solution containing ethanol, diethyl ether and acetaldehyde are obtained (the contents of acetaldehyde, ethanol and diethyl ether are 0.26wt%, 6.29wt% and 12.15wt%, respectively). (2) The mixed solution is fed to a distillation column. The resulting overhead gas is cooled in the overhead condenser and then enters the overhead reflux tank. The liquid phase at the bottom of the reflux tank is pressurized by a pump, with a portion returning to the top of the column and the remainder sent to a gas-liquid separator. The liquid ethanol is vaporized in the feed evaporator, and then the vaporized mixed gas is sent to the reactor. In this comparative example, the recovery rate of ethanol and diethyl ether is 99.9%; the feed evaporator provides 58.2744 MW of heat, and the reboiler of the ethanol / diethyl ether recovery column requires 46.5336 MW of heat from medium-pressure steam.

[0048] Experimental Example The consumption per ton of mixed solution containing ethanol and diethyl ether in each of the above embodiments and comparative examples was tested, including the consumption of circulating water, steam, and dehydration reaction cycle. The results are shown in Table 1 below.

[0049] Table 1. Consumption per ton of mixed solution containing ethanol, diethyl ether, and acetaldehyde for treatment

[0050] As shown in Table 1, the organic wastewater treatment method of this invention has low energy consumption, enables continuous operation of the dehydration reaction unit, and saves production costs. Compared with Example 4, Example 5 omits the absorption process, resulting in an 8.80% decrease in the recovery rate of ethanol and diethyl ether, and a significant loss of valuable materials. In Comparative Example 1, the overhead condenser consumes 3502 t / h of circulating water, an increase of 348% compared to Example 2, and consumes 188.7 t / h of medium-pressure steam, an increase of 1732% compared to Example 2. Furthermore, although Comparative Example 1 has a high recovery rate of diethyl ether and ethanol, the lack of acetaldehyde removal causes coking in the reactor, shortening the operating cycle to only 30 days.

[0051] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for treating organic wastewater from ethanol dehydration to ethylene production, characterized in that, Includes the following steps: (1) Ethylene is prepared from ethanol under the action of a catalyst, and a mixture containing ethanol, diethyl ether and acetaldehyde is collected after separation. (2) The mixture containing ethanol, ether, and acetaldehyde is hydrogenated, and the resulting hydrogenated product is stripped and the overhead gas is collected and returned to step (1) as raw material.

2. The method for treating organic wastewater from ethanol dehydration to ethylene production according to claim 1, characterized in that, The hydrogenation products include gas-phase hydrogenation products and liquid-phase hydrogenation products. The process also includes absorption treatment of the gas-phase hydrogenation products, followed by pressurization and stripping of the absorbed gas-phase hydrogenation products and liquid-phase hydrogenation products.

3. The method for treating organic wastewater from ethanol dehydration to ethylene production according to claim 2, characterized in that, The absorption treatment temperature is 10℃-25℃; And / or, the absorbent in the absorption treatment includes ethanol.

4. The method for treating organic wastewater from ethanol dehydration to ethylene production according to claim 1, characterized in that, It also includes pressurizing the top gas of the tower to 1.0MPaG-1.5MPaG, exchanging heat with liquid ethanol, and then separating the gas and liquid phases. The resulting gas phase is returned to step (1).

5. The method for treating organic wastewater from ethanol dehydration to ethylene production according to claim 1, characterized in that, The theoretical number of trays in the stripping unit is 15-50; the top temperature is 100℃-156℃, and the pressure is 0.05MPaG-0.5MPaG; the bottom temperature is 110℃-162℃, and the pressure is 0.06MPaG-0.55MPaG.

6. The method for treating organic wastewater from ethanol dehydration to ethylene production according to claim 1, characterized in that, The mixture containing ethanol, diethyl ether, and acetaldehyde also includes a cooling step before hydrogenation treatment.

7. The method for treating organic wastewater from ethanol dehydration to ethylene production according to claim 1, characterized in that, The hydrogenation treatment is carried out at a temperature of 20°C to 60°C and a pressure of 0.1 MPaG to 1 MPaG.

8. A system for treating organic wastewater from the ethanol dehydration to ethylene production method according to any one of claims 1-7, characterized in that, include: The reaction unit, separation unit, hydrogenation unit, and stripping unit are connected in sequence, with the top outlet of the stripping unit connected to the inlet of the reaction unit.

9. The organic wastewater treatment system for ethanol dehydration to ethylene production according to claim 8, characterized in that, It also includes an absorption device, the inlet of which is connected to the gas phase outlet of the hydrogenation device; The collection device has its inlet connected to the outlet of the absorption device and the liquid phase outlet of the hydrogenation device, respectively. The first compression device has its inlet connected to the outlet of the collection device, and its outlet connected to the inlet of the stripping device.

10. The organic wastewater treatment system for ethanol dehydration to ethylene production according to claim 8, characterized in that, It also includes a second compression unit, the inlet of which is connected to the top outlet of the stripping unit; The heat exchanger has its inlet connected to the outlet of the second compression unit and the outlet of the ethanol storage tank, respectively. A gas-liquid separation device, the inlet of which is connected to the outlet of the heat exchange device, and the gas phase outlet of which is connected to the inlet of the reaction device; And / or, a cooling device, the inlet of which is connected to the outlet of the separation device, and the outlet of which is connected to the inlet of the hydrogenation device.

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