Method and system for preparing ethylene from acetylene and wastewater driven by renewable energy sources

Abstract

The invention relates to a system and a method for preparing ethylene from acetylene and wastewater driven by renewable energy sources. The system comprises a wastewater pretreatment module, a waste heat recovery module, a gas-liquid proportional mixing module, an acetylene-to-ethylene electrolytic cell module, a gas-liquid separation module, a washing and cooling module and a drying module which are connected in sequence, the device further comprises an alkali liquor filtering and circulating module and a rectification power supply module. According to the invention, the electro-catalytic reaction is driven by green electricity, low-carbon green production is realized, the rectification power supply module is directly connected with renewable electricity to drive the electro-catalytic reaction, extra hydrogen is not needed, a dual-carbon target is met, and a green solution is provided for ethylene production in a non-petroleum line. The industrial wastewater is used for replacing 100% fresh water to serve as an electro-catalysis proton source, consumption of the fresh water is reduced, meanwhile, wastewater reduction is achieved, and the concept of zero emission is met.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ethylene preparation, in particular, and especially relates to a method and system for preparing ethylene from renewable energy driven acetylene and wastewater. BACKGROUND

[0002] As a core chemical raw material, traditional petroleum cracking routes have the problems of strong dependence on petroleum and high carbon emissions; although the existing coal-based acetylene electrocatalytic preparation of ethylene technology breaks through the dependence on petroleum, it still relies on fresh water resources as the proton source of the electrolyte, and does not fully consider the power fluctuation characteristics of renewable energy (wind power and photovoltaic power), which easily leads to system load fluctuation when green power is unstable, reducing production efficiency; at the same time, the amount of industrial wastewater discharged is huge, if it can be used for electrocatalytic reaction, it can not only reduce the consumption of fresh water, but also realize wastewater reduction, which is in line with the concept of circular economy.

[0003] The existing patent document CN114163298A discloses a new process for producing chloroethylene from methanol, in which ethylene is derived from the dehydration of methanol to ethanol (i.e. dimethyl ether route / acetic acid hydrogenation route), and acetylene is only used to react with the hydrogen chloride byproduct of dichloroethane cracking to produce chloroethylene, without involving acetylene for ethylene production.

[0004] The existing patent document CN118079808A discloses a device and method for coupling wind power and / or solar power to produce hydrogen for coal-based ethylene production, in which acetylene is used for ethylene production by thermal catalytic hydrogenation: a palladium-silver alloy supported catalyst (TiO2 as the carrier) is used, and hydrogen gas from the hydrogen storage tank of the wind power / solar power hydrogen production system is used as the hydrogenation raw material to realize acetylene hydrogenation to ethylene in a slurry bed reactor. The renewable electricity in this technology is only used for hydrogen production, and the hydrogenation is a thermal catalyst that requires additional heating. The entire system is maintained at medium temperature (120-180℃) and medium pressure (1-6MPa), and a hydrogen storage tank is needed to store the hydrogen produced by wind power / solar power. The system is relatively complex. Although this technology uses green electricity, it is only used for hydrogen production and does not solve the problems of fluctuation adaptation and wastewater.

[0005] The existing patent document CN102358943A discloses a method for electrochemically synthesizing ethylene and oxalic acid from acetylene, which is an electrochemical route. A bipolar electrolytic cell is used, acetylene is in-situ reduced to ethylene at the cathode chamber with H atoms / H2 generated by electrolysis, and acetylene is in-situ oxidized to oxalic acid at the anode chamber with O atoms / O2. The electrolyte is an H2SO4 / Na2SO4 system, the current density is 40-140mA / cm 2 , and the operation is at room temperature. This technology only uses laboratory-level electrolytic cell reactions and does not involve green electricity and wastewater, so its practicality is limited. SUMMARY

[0006] The present application provides a method and system for preparing ethylene from acetylene and wastewater driven by renewable energy, which realizes the preparation of ethylene from acetylene and wastewater driven by renewable energy without heating and hydrogen storage, has a shorter energy conversion link, reduces energy consumption and carbon emissions.

[0007] The technical means adopted by the present application are as follows: The system for preparing ethylene from acetylene and wastewater driven by renewable energy comprises, in sequence, a wastewater pretreatment module, a waste heat recovery module, a gas-liquid proportioning module, an acetylene-to-ethylene electrolytic cell module, a gas-liquid separation module, a washing and cooling module and a drying module; and further comprises an alkali solution filtration and circulation module and a rectifier power supply module. The wastewater pretreatment module is used for filtering, conditioning and purifying industrial wastewater to obtain wastewater meeting standards as a proton source and electrolyte component for electrocatalytic reaction. The gas-liquid proportioning module is connected with a clean acetylene supply end and an electrolyte supply end, and is used for controlling the mass ratio of clean acetylene and electrolyte. The acetylene-to-ethylene electrolytic cell module is used for generating ethylene by electrocatalytic reaction of clean acetylene and water in electrolyte driven by direct current. The gas-liquid separation module is used for preliminarily separating the gas-liquid mixture after electrocatalytic reaction. The washing and cooling module is used for removing alkali mist from the separated gas and cooling the gas to normal temperature. The drying module is used for drying ethylene. The alkali solution filtration and circulation module is used for recycling the alkali solution separated by the gas-liquid separation module and conveying the alkali solution to the waste heat recovery module. The waste heat recovery module is used for recycling waste heat generated by the alkali solution, which is used as the electrolyte supply end of the gas-liquid proportioning module. The rectifier power supply module is electrically connected with the acetylene-to-ethylene electrolytic cell module, and is used for driving electrocatalytic reaction by rectified direct current.

[0008] Further, the wastewater pretreatment module comprises a wastewater supply module and a wastewater filtration module.

[0009] Further, the gas-liquid separation module comprises an oxygen side gas-liquid separation module and an ethylene side gas-liquid separation module, which respectively separate oxygen side products and ethylene side products; the oxygen side gas-liquid separation module is connected with the oxygen side washing and cooling module, and the ethylene side gas-liquid separation module is connected with the ethylene side washing and cooling module.

[0010] Further, the waste heat recovery module comprises a waste heat recovery low-temperature waste water evaporation module, an output end of the waste heat recovery low-temperature waste water evaporation module is connected with the condensation module, one output end of the condensation module is connected with the vacuum module, the other output end of the condensation module is connected with the buffer water tank, an output end of the buffer water tank is connected with the water supplement module, the water supplement module is connected with the ethylene side gas-liquid separation module, and the water supplement module is externally connected with a water outlet for supplying surplus fresh water.

[0011] Further, the acetylene electrolytic cell adopts a structure design of cathode, anode and anion diaphragm, and realizes an electrocatalytic reaction by taking water as a proton source.

[0012] The application further discloses a method for preparing ethylene from acetylene and waste water driven by renewable energy based on the system, and the method comprises the following steps. S1. Gas-liquid mixing and electrocatalysis: clean acetylene and electrolyte enter a gas-liquid proportional mixing module at a preset mass ratio, the gas-liquid mixture enters an acetylene electrolytic cell module after being uniformly mixed, and a rectifier power supply module supplies power, so that acetylene and water generate electrocatalytic reaction to generate ethylene. S2. Product separation and drying: the reaction product is treated by a gas-liquid separation module and a washing and cooling module, and then enters a drying module to dry ethylene.

[0013] Further, clean acetylene and electrolyte enter a gas-liquid proportional mixing module at a mass ratio of 1:(10-20).

[0014] Compared with the prior art, the application has the following advantages: 1. Industrial waste water is used to replace 100% fresh water as a proton source for electrocatalysis, fresh water consumption is reduced, waste water reduction is realized, and the concept of "zero emission" is met.

[0015] 2. The application improves the reaction rate by precise control of gas-liquid ratio and electrocatalytic reaction, and a selective gas-liquid proportional mixing module is used to precisely control the mass ratio of 1:(10-20), so that acetylene and electrolyte can fully react in the electrolytic cell after uniform contact, the reaction rate is stable, and the ethylene yield is significantly improved compared with a non-uniform mixing system.

[0016] 3. The application realizes low-carbon green production by driving electrocatalytic reaction with green electricity, directly connects a rectifier power supply module with renewable electricity to drive electrocatalytic reaction, does not need additional hydrogen, and uses water as a proton donor to participate in cathodic hydrogenation reaction, realizes recycling and regeneration through anode reaction, and completes OH -The conduction of the hydrogen ion ensures the continuous progress of the electrocatalytic reaction, without the need to additionally introduce hydrogen or other proton sources, realizing a green reaction path of water as a proton source and electrocatalytic ethylene production. The present application has low energy consumption, and the carbon emission per ton of ethylene is reduced by more than 80%, which meets the 'double carbon' target, provides a green solution for non-petroleum route ethylene production, and the waste heat recovery module can use renewable peak excess waste electricity, improving the utilization rate of electric energy. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0018] Figure 1 The system diagram of the present application.

[0019] Figure 2 The electrolytic cell reaction schematic diagram of the present application.

[0020] Figure 3 The system diagram of the present application which is extended to prepare clean acetylene in the front process. DETAILED DESCRIPTION

[0021] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the drawings and in combination with the embodiments.

[0022] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings of the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all. The description of the at least one exemplary embodiment is actually only illustrative, but not as any limitation on the present application and its application or use. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0023] It should be noted that the terms used herein are only for describing specific embodiments, and are not intended to limit the exemplary embodiments according to the present application. As used herein, the singular form is intended to include the plural form unless the context clearly indicates otherwise, and it should also be understood that when the terms "comprise" and / or "include" are used in the specification, there is a feature, step, operation, device, component and / or combination thereof.

[0024] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0025] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention. The directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0026] For ease of description, spatial relative terms such as "above," "over," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation besides the orientation of the device as described in the figures. For example, if the device in the figures is inverted, a device described as "above" or "above" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0027] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0028] likeFigure 1 As shown in the figure, this invention discloses a renewable energy-driven system for producing ethylene from acetylene and wastewater, comprising a wastewater pretreatment module, a waste heat recovery module, a gas-liquid proportioning mixing module, an acetylene-to-ethylene electrolytic cell module, a gas-liquid separation module, a washing and cooling module, and a drying module connected in sequence; it also includes an alkaline solution filtration and circulation module and a rectifier power supply module; The wastewater pretreatment module is used to filter, condition, and purify industrial wastewater to obtain wastewater that meets the standards, which can then be used as a proton source and electrolyte component for electrocatalytic reactions. The gas-liquid ratio mixing module is connected to the supply end of clean acetylene and the supply end of electrolyte, and is used to control the mass ratio of clean acetylene to electrolyte. The acetylene-to-ethylene electrolytic cell module is used to generate ethylene by electrocatalytic reaction between clean acetylene and water in the electrolyte under DC drive, and it is designed to achieve low-pressure conditions. The gas-liquid separation module is used to perform preliminary gas-liquid separation on the gas-liquid mixture after the electrocatalytic reaction; The washing and cooling module is used to remove alkaline mist from the separated gas and cool it to room temperature; The drying module is used to dry ethylene; The alkaline solution filtration and circulation module is used to recover the alkaline solution separated by the gas-liquid separation module and transport it to the waste heat recovery module. The waste heat recovery module is used to recover the waste heat generated by the alkali solution, and it serves as the supply end of the electrolyte for the gas-liquid proportioning mixing module. The rectifier power supply module is electrically connected to the acetylene-to-ethylene electrolytic cell module and is used to drive the electrocatalytic reaction with rectified DC power.

[0029] The rectifier module in this invention is a DC / DC module directly connected to the green electricity, primarily functioning as a current stabilizer. It further regulates and rectifies the green electricity to provide a stable current to the electrolytic cell.

[0030] Preferably, the present invention also includes a green electricity fluctuation adaptation module, comprising a power monitoring instrument, a PLC controller, a power distribution unit, an electric heating component, and a wastewater storage tank, which automatically switches the system operation mode according to the green electricity (wind power and / or photovoltaic) power, thereby realizing efficient utilization of green electricity in all scenarios.

[0031] Specifically, based on the green electricity power range, when the green electricity power is within the range of 30% to 110% of the electrolyzer's rated power, the system dynamically adapts to the green electricity power, and the electrolyzer's operating power fluctuates synchronously with the actual green electricity power, ensuring full utilization of the green electricity. Simultaneously, compliant wastewater is fed into the gas-liquid proportioning module at a ratio matching the real-time power of the electrolyzer; the higher the power, the closer the proportion is to 100%, avoiding waste of green electricity. When the green electricity power is ≥70% of the electrolyzer's rated power, i.e., in the high-power range of 30% to 110%, the system operates at full load, and 100% of the compliant wastewater is fed into the gas-liquid proportioning module, with the electrolyzer producing ethylene at its rated current density. When the green electricity power is 30% to 70% of the electrolyzer's rated power, i.e., in the medium-low power range of 30% to 110%, 70% of the compliant wastewater is used to produce electrolyte, and 30%... The qualified wastewater is preheated to 40-50℃ by the electric heating components and then temporarily stored in the wastewater storage tank. Once the power recovers to a higher range, it is sent to the gas-liquid proportioning mixing module along with newly added qualified wastewater to avoid electrolyte waste at low power. When the green electricity power is less than 30% of the electrolyzer's rated power, the electrolyzer stops operating, and the system switches to a low-power desalination mode. The electric heating components directly utilize the current low-power green electricity to drive the qualified wastewater in the wastewater storage tank to evaporate at low temperature. The desalination is reused for system replenishment or external supply, ensuring that the green electricity can still be effectively utilized even if it is below the electrolyzer's start-up threshold. When the green electricity power is greater than 110% of the electrolyzer's rated power, the electrolyzer operates at full load at its rated power. The excess green electricity exceeding 110% of the rated power is sent to the electric heating components of the waste heat recovery module through the power distribution unit as an additional heat source to combine with the alkaline waste heat, jointly driving the low-temperature evaporation of the qualified wastewater, increasing desalination production, and further improving energy efficiency.

[0032] That is, when renewable energy power is at its peak, the excess electricity can be used in the waste heat recovery module for heating to increase freshwater production; when renewable energy is at its trough and does not meet the operating requirements of the electrolyzer, the waste heat recovery module can be used to heat renewable energy power to produce freshwater; when the power is within the range of 30%-110% of the electrolyzer's rated power, it fluctuates according to the operating power of the electrolyzer.

[0033] Furthermore, the wastewater pretreatment module includes a wastewater supply module and a wastewater filtration module. In this embodiment, the wastewater pretreatment module can be specifically configured according to the water conditions of the plant area, such as seawater or factory wastewater, which require different treatment of impurities. However, in general, the wastewater supply module needs to be equipped with a water storage tank, a variable frequency water pump, and other devices. The wastewater filtration module needs to have at least a mechanical bar screen, a coagulation sedimentation unit, and a microfiltration membrane assembly to remove large suspended solids, remove colloidal impurities, and retain remaining small particles, so that the suspended solids in the effluent are below the water quality requirements for the electrocatalytic reaction. In some optional embodiments, a turbidity sensor can also be installed at the wastewater filtration module to provide real-time feedback on the filtration effect, and automatically trigger a backwashing procedure when the turbidity exceeds the standard.

[0034] Furthermore, the gas-liquid separation module includes an oxygen-side gas-liquid separation module and an ethylene-side gas-liquid separation module, which separate oxygen-side products and ethylene-side products, respectively; the oxygen-side gas-liquid separation module is connected to the oxygen-side washing and cooling module, and the ethylene-side gas-liquid separation module is connected to the ethylene-side washing and cooling module.

[0035] Furthermore, the waste heat recovery module includes a waste heat recovery low-temperature wastewater evaporation module, whose output end is also connected to a condensation module. One output end of the condensation module is connected to a vacuum module, and the other output end is connected to a buffer water tank. The output end of the buffer water tank is connected to a water replenishment module, which is connected to an ethylene-side gas-liquid separation module. The water replenishment module also has an external water outlet for supplying surplus fresh water. The waste heat recovery low-temperature wastewater evaporation module is connected to a wastewater filtration module to receive pretreated wastewater that meets standards, and to an alkali solution filtration and circulation module to receive recovered alkali solution. It can also recover waste heat generated during the operation of the electrolytic cell. Its output end is connected to a gas-liquid proportioning mixing module to mix the evaporated and concentrated alkali solution with the qualified wastewater in a proportion as the electrolyte for the electrocatalytic reaction. Its other output end is connected to the condensation module to send the steam generated by evaporation into the condensation module. When the green electricity power is greater than 110% of the rated power of the electrolyzer, the module also receives excess green electricity from the power distribution unit, which works synergistically with the waste heat from the alkaline solution to improve the evaporation efficiency of wastewater and increase the production of freshwater.

[0036] The waste heat recovery low-temperature wastewater evaporation module includes a waste heat exchanger, an evaporation chamber, and a heat medium circulation pump. Qualified wastewater and recovered alkaline solution enter the evaporation chamber in a certain proportion. Existing electrocatalytic systems cannot cope with power fluctuations in wind / solar power, resulting in high curtailment rates. This invention addresses this by setting up multiple green energy adaptation levels and combining them with the multi-heat source utilization of the waste heat recovery module, significantly improving green energy utilization. Even if the green energy output is lower than the electrolyzer's startup power, it can still be utilized through desalination. Even if the green energy output far exceeds the electrolyzer's needs, excess electricity can be converted into desalination resources, avoiding waste. Furthermore, it does not rely on waste heat from the electrolyzer; the module can be directly driven by green energy, ensuring wastewater resource recovery and basic system functionality. This completely solves the industry bottleneck of system shutdown due to insufficient green energy.

[0037] Furthermore, the waste heat from the electrolytic cell (when operating at 30%~110% capacity) and excess green electric heat energy (when >110% capacity) are used synergistically for wastewater evaporation, which not only produces freshwater for reuse but also achieves a cascade conversion of electricity, heat, and water, thus improving the system's energy utilization rate. The system not only uses wastewater as a proton source for electrocatalysis but also recovers freshwater through evaporation, while simultaneously concentrating and recycling the alkali solution, reducing raw material consumption.

[0038] In addition, traditional industrial wastewater is directly discharged, resulting in high treatment costs. This invention replaces 100% of fresh water with wastewater, has a high freshwater reuse rate, and the synergistic recovery of waste heat from the electrolytic cell and excess green electricity further reduces system energy consumption.

[0039] The water replenishment module is specifically a water replenishment tank. After water enters the tank, it is pumped into the system to replenish the water supply.

[0040] Furthermore, the acetylene-to-ethylene electrolyzer adopts a structure design with cathode and anode electrodes and an anion exchange membrane, using water as a proton source to achieve the electrocatalytic reaction.

[0041] like Figure 3 As shown, the gas-liquid proportioning mixing module and the supply end of clean acetylene in this invention can be directly purchased clean acetylene, or, as an optional implementation, a coal-based acetylene pretreatment unit can be set up to realize a series of processes after the crude acetylene generated from calcium carbide, thereby achieving a direct supply of clean acetylene. In this implementation, the coal-based acetylene pretreatment unit includes a water washing module, a cleaning module, an alkaline washing module, and a cooling and drying module connected in sequence. The cleaning module is connected to a sodium hypochlorite dosing unit. The water washing module is used to perform preliminary impurity removal by water washing on the crude acetylene generated from calcium carbide. The cleaning module is used to remove acidic impurities by cleaning with sodium hypochlorite. The alkaline washing module is used to neutralize residual acidity by alkaline washing. The cooling and drying module is used to achieve cooling and drying treatment. In this embodiment, a sodium hypochlorite solution of approximately 0.10% is used for cleaning. The cleaned acetylene enters the alkaline washing module and reacts with a 15% (w / w) sodium hydroxide solution. The water washing module can be a water washing tower, the cleaning module can be a cleaning tower, the alkaline washing module can be an alkaline washing tower, and the cooling and drying module can be a cooling and drying tower.

[0042] Specifically, crude acetylene enters from the bottom of the water washing tower, while deionized water is sprayed from the top to remove dust and some acidic gases from the acetylene, reducing its water content. The dosing unit dilutes concentrated sodium hypochlorite with industrial water to a 0.10% (mass fraction) sodium hypochlorite solution, which is then pumped into the purification tower. The oxidizing properties of sodium hypochlorite oxidize H2S and PH3 into acidic substances such as sulfate and phosphate. The preparation unit mixes concentrated sodium hydroxide with direct-flow water to prepare a 15% (mass fraction) sodium hydroxide solution, which is then fed into the tower to neutralize any remaining acidic substances and remove some organic impurities. The cooling dryer uses freeze drying to reduce the water content of the alkali-washed acetylene to below 0.5%, yielding clean acetylene with a purity ≥99.5%.

[0043] Furthermore, the input end of the coal-based acetylene pretreatment unit is connected to a crude acetylene preparation unit, which includes an acetylene generating module. This module prepares crude acetylene through a chemical reaction between calcium carbide and water. The reaction formula is CaC2 + 2H2O → C2H2↑ + Ca(OH)2. Specifically, calcium carbide is added to the reactor within the module, and water is introduced. The calcium carbide and water undergo an exothermic reaction in the reactor, generating crude acetylene gas containing impurities such as hydrogen sulfide, phosphine, and water vapor. This crude acetylene then enters a water washing module for preliminary impurity removal.

[0044] This invention also discloses a method for producing ethylene from acetylene and wastewater using renewable energy driven by the above system, comprising the following steps: S1. Gas-liquid mixing and electrocatalysis: Clean acetylene and electrolyte are introduced into the gas-liquid ratio mixing module at a preset mass ratio. After uniform mixing, the gas-liquid mixture enters the acetylene-to-ethylene electrolytic cell module, powered by the rectifier power supply module. Acetylene and water undergo an electrocatalytic reaction to produce ethylene. The operating power of the electrolytic cell is dynamically adjusted according to the actual power of the green electricity. When the green electricity is between 30% and 110% of the rated power, it operates accordingly; when it is less than 30%, it stops; and when it is greater than 110%, it operates at the rated power. S2. Product separation and drying: After being processed by the gas-liquid separation module and the washing and cooling module, the reaction products enter the drying module to dry ethylene.

[0045] Specifically, if the green electricity power is less than 30% of the rated power of the electrolyzer, the electrolyzer will be shut down and the electric heating component will be started. The low-power green electricity will be used to drive the low-temperature evaporation of the qualified wastewater in the wastewater storage tank. The steam will be condensed by the condensation module and stored in the buffer water tank. The fresh water will be used for system replenishment or external supply. If the green electricity power is greater than 110% of the electrolyzer's rated power, the electrolyzer will operate at full load. The excess green electricity will be transferred to the electric heating components of the waste heat recovery module, which will work in conjunction with the alkaline waste heat to drive the evaporation of qualified wastewater and increase freshwater production.

[0046] As an extended embodiment of the method for setting up a coal-based acetylene pretreatment unit, before S1, the method further includes the following steps: Crude acetylene washing: Crude acetylene generated from calcium carbide enters the washing module to initially remove water-soluble impurities; Cleaning treatment: After being washed with water, the acetylene enters the cleaning module and reacts with sodium hypochlorite solution to remove H2S and pH3, with residual impurities ≤0.001%; Alkali washing and neutralization: The purified acetylene enters the alkaline washing module and reacts with sodium hydroxide solution to adjust the pH to 7-8; Cooling and drying: The acetylene after alkali washing enters the cooling and drying module, where the temperature drops to 5~10℃ and the moisture content drops to below 0.5%, thus obtaining clean acetylene; Furthermore, clean acetylene and electrolyte are introduced into the gas-liquid ratio mixing module at a ratio of 1:(10~20).

[0047] Among them, such as Figure 2 As shown, the cathode-side reaction produces ethylene. Clean acetylene, after being uniformly distributed through a gas diffusion layer, undergoes an electrocatalytic reaction with water (acting as a proton source) on the cathode surface. The reaction equation is C2H2 + H2O + 2e- → 2OH- + C2H4. In this process, water provides the protons (H+) required for the reaction. + With the participation of electrons, it selectively hydrogenates with acetylene to produce ethylene, while simultaneously generating hydroxide ions (OH-).

[0048] The reaction on the anode side generates oxygen. The OH- generated at the cathode migrates to the anode through the anion separator and undergoes an oxidation reaction. The reaction formula is 2OH-→H2O+1 / 2O2+2e-, which generates oxygen and releases electrons. The electrons return to the cathode through the external circuit, forming a current loop.

[0049] In this process, water participates in the cathode hydrogenation reaction as a proton donor, and is also recycled through the anode reaction. Simultaneously, an anion exchange membrane facilitates the completion of OH- ion exchange. - The conduction of water ensures the continuous progress of the electrocatalytic reaction without the need for additional hydrogen or other proton sources, thus realizing a green reaction pathway for the electrocatalytic production of ethylene using water as a proton source.

[0050] As an optional implementation, this system can also be equipped with intelligent functions to intelligently complete the process of high-efficiency electrocatalytic production of ethylene from coal-based acetylene. Specifically, a turbidity sensor is installed at the outlet pipe of the water washing module's water washing tower to monitor the turbidity of the water after washing in real time. A flow sensor is installed at the inlet pipe of the water washing tower to monitor the spray water flow rate in real time. An online pH sensor is installed at the outlet pipe of the cleaning tower's washing liquid to indirectly reflect the residual amount of acidic impurities H2S and PH3. A flow sensor is installed at the outlet pipe of the sodium hypochlorite dosing unit's metering pump to monitor the sodium hypochlorite solution dosing flow rate in real time. An online pH sensor is installed at the outlet pipe of the alkaline washing tower's washing liquid to monitor the pH value after alkaline washing to determine the degree of neutralization of acidic substances. An online flow sensor is installed at the outlet pipe of the sodium hydroxide solution pump to monitor the sodium hydroxide solution dosing flow rate in real time.

[0051] Specifically, the water washing module control method is as follows: When the turbidity sensor detects that the turbidity of the water after washing exceeds the preset value, the PLC controller automatically increases the spray water flow rate of the water washing tower; when the turbidity is lower than the minimum preset value, the flow rate is automatically reduced to the initial value to ensure that the acetylene dust content after washing meets the requirements. During this process, the spray water flow rate and the crude acetylene feed flow rate are linked in real time to maintain the spray water flow rate. In this embodiment, the crude acetylene flow rate = 1.2:1 to avoid imbalance in the water washing effect due to feed fluctuations. The cleaning module control method is as follows: When the pH of the cleaning solution is < 5.5, the PLC controller automatically increases the flow rate of the sodium hypochlorite metering pump; when the pH is > 7.0, the flow rate is automatically reduced to the initial value to ensure that the removal rate of H2S and PH3 is ≥ 99.9% and the residual amount is ≤ 0.001%. The concentration of sodium hypochlorite solution is stabilized at a mass fraction of 0.10%, and the dosage is precisely adjusted through the pulse control of the metering pump, thereby controlling the dosing error. The control method for the alkaline washing module is as follows: When the pH of the washing solution after alkaline washing is <7.5, the PLC controller automatically increases the flow rate of the sodium hydroxide solution pump; when the pH is >8.5, the flow rate is automatically reduced to the initial value to ensure that the pH of the acetylene after alkaline washing is stable at 8.0~8.5. When the concentration of sodium hydroxide solution is detected to have decreased to a certain mass fraction due to consumption, the dosing unit is automatically triggered to replenish concentrated alkali to maintain a stable concentration.

[0052] Through the above intelligent settings, the purity of clean acetylene is stabilized at at least 99.7%, and the removal rates of H2S and PH3 are effectively controlled, providing extremely pure raw materials for subsequent electrocatalytic reactions.

[0053] The intelligent design of the gas-liquid proportioning mixing module is crucial. A high-precision mass flow meter is installed at the clean acetylene inlet, within the inlet pipe of the gas-liquid proportioning mixing module, to monitor the mass flow rate of clean acetylene in real time, ensuring accurate flow measurement. Similarly, a high-precision mass flow meter is installed at the electrolyte inlet, within the inlet pipe of the gas-liquid proportioning mixing module, to monitor the mass flow rate of the electrolyte in real time. The PLC controller incorporates a PID control algorithm to ensure the mass ratio of clean acetylene to electrolyte remains stable within the range of 1:(10~20). An electric regulating valve is used on the acetylene side, and the same model electric regulating valve is used on the electrolyte side. The valve opening is adjusted in real time according to the PID output signal to control the gas-liquid flow ratio. When water needs to be added to the electrolytic cell, the water replenishment action is automatically triggered, the water pump starts, and water from the water replenishment module is added to the electrolyte circulation system. Through these intelligent settings, the control accuracy of the gas-liquid mass ratio is stable, and the precise gas-liquid ratio enhances the selectivity of the acetylene reaction within the electrolytic cell. Furthermore, based on fluctuations in the clean acetylene flow rate, the gas-liquid ratio mixing module can quickly and adaptively adjust the flow ratio to ensure a stable gas-liquid ratio in the electrolyzer feed. The PLC system receives clean acetylene flow rate and purity data from the coal-based acetylene pretreatment unit, automatically optimizes the gas-liquid ratio settings, and appropriately adjusts the electrolyte ratio when the clean acetylene purity increases to maintain optimal reaction, achieving intelligent coordination throughout the entire process and further improving ethylene yield.

[0054] To achieve accurate monitoring of the electrolyzer under all operating conditions, the installed sensors need to cover all dimensions, including electrical parameters, liquid level, and product composition. When the current sensor detects that the current density is too low, the PLC sends a signal to the rectifier power supply, gradually increasing the output voltage from the current value until the current density returns to the preset value. Similarly, when the gas-liquid ratio is too high, causing the current density to be too high, the output voltage gradually decreases until it falls back to the preset value. The liquid level sensor acquires liquid level data in real time, and the water pump starts and stops accordingly. In addition, when liquid level fluctuations occur, it is linked with the gas-liquid ratio mixing module to start the water pump a certain period of time in advance when the electrolyte flow rate increases, preventing a sudden drop in liquid level.

[0055] In addition, the electrolyzer control PLC is also linked to product information. If the ethylene purity is <99.9% and the unreacted acetylene percentage is >0.5%, it indicates an improper gas-liquid ratio and excessive acetylene. In this case, the PLC sends a signal to the gas-liquid ratio mixing module to reduce the clean acetylene flow rate by at least 5%, while maintaining the electrolyte flow rate unchanged. After a few seconds, the purity is checked, and if it does not meet the standard, it is reduced by at least 3%. If the ethylene purity is <99.9% and the unreacted acetylene is normal, the current density is reduced, and the electrolyte circulation flow rate is increased until the purity recovers. If the oxygen purity is <95%, it indicates an abnormal anode reaction, and the electrolyzer shutdown check signal is immediately triggered to avoid electrolyte contamination.

[0056] Liquid level sensors, pressure sensors, and flow sensors are installed in the gas-liquid separation modules on both the oxygen and ethylene sides to monitor the liquid level, gas pressure, and gas-liquid mixture flow rate in the separation chamber in real time. A temperature sensor is installed in the washing and cooling module to monitor the temperature of the cooled gas. All sensor data is transmitted to the PLC control system in real time. When the liquid level sensor detects that the liquid level in the separation chamber exceeds a set threshold, the PLC automatically adjusts the opening of the drain valve to maintain a stable liquid level and prevent liquid entrainment or insufficient gas-liquid separation. When the pressure sensor detects that the gas pressure fluctuation exceeds a preset value, the PLC, in conjunction with the flow sensor data, automatically adjusts the feed flow rate of the gas-liquid mixture to ensure stable pressure in the separation chamber, resulting in a gas phase liquid content ≤0.1% after gas-liquid separation. The intelligent gas-liquid separation module can stably achieve efficient gas-liquid separation, resulting in extremely low liquid content in the gas entering the washing and cooling module, indirectly maintaining the final purity of ethylene stably above 99.9%. When the quality of calcium carbide changes, the intelligent gas-liquid separation module can automatically adapt and adjust to fluctuations in crude acetylene flow rate and impurity content, keeping ethylene yield fluctuations within an effective range. The PLC control system can also record real-time operating data of the gas-liquid separation module, and through big data analysis, predict the failure risk of separation components, reducing downtime.

[0057] The intelligent systems of each module achieve data communication through industrial Ethernet. The PLC central control system can automatically optimize the ratio of the gas-liquid proportioning module according to the acetylene purity and flow rate of the pretreatment unit. Combined with the current density and product composition data of the electrolytic cell, it dynamically adjusts the output parameters of the rectifier power supply to form a fully intelligent closed loop of pretreatment, reaction, separation, and recovery.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A system for producing ethylene from acetylene and wastewater using renewable energy, characterized in that, It includes a wastewater pretreatment module, a waste heat recovery module, a gas-liquid proportioning mixing module, an acetylene-to-ethylene electrolytic cell module, a gas-liquid separation module, a washing and cooling module, and a drying module connected in sequence; it also includes an alkaline solution filtration and circulation module and a rectifier power supply module. The wastewater pretreatment module is used to filter, condition, and purify industrial wastewater to obtain wastewater that meets the standards, which can then be used as a proton source and electrolyte component for electrocatalytic reactions. The gas-liquid ratio mixing module is connected to the supply end of clean acetylene and the supply end of electrolyte, and is used to control the mass ratio of clean acetylene to electrolyte. The acetylene-to-ethylene electrolytic cell module is used to enable clean acetylene to undergo an electrocatalytic reaction with water in the electrolyte to produce ethylene under DC drive. The gas-liquid separation module is used to perform preliminary gas-liquid separation on the gas-liquid mixture after the electrocatalytic reaction; The washing and cooling module is used to remove alkaline mist from the separated gas and cool it to room temperature; The drying module is used to dry ethylene; The alkaline solution filtration and circulation module is used to recover the alkaline solution separated by the gas-liquid separation module and transport it to the waste heat recovery module. The waste heat recovery module is used to recover the waste heat generated by the alkali solution, and it serves as the supply end of the electrolyte for the gas-liquid proportioning mixing module. The rectifier power supply module is electrically connected to the acetylene-to-ethylene electrolytic cell module and is used to drive the electrocatalytic reaction with rectified DC power.

2. The system for producing ethylene from acetylene and wastewater driven by renewable energy according to claim 1, characterized in that, The wastewater pretreatment module includes a wastewater supply module and a wastewater filtration module.

3. The system for producing ethylene from acetylene and wastewater driven by renewable energy according to claim 1, characterized in that, The gas-liquid separation module includes an oxygen-side gas-liquid separation module and an ethylene-side gas-liquid separation module, which separate oxygen-side products and ethylene-side products, respectively. The oxygen-side gas-liquid separation module is connected to the oxygen-side washing and cooling module, and the ethylene-side gas-liquid separation module is connected to the ethylene-side washing and cooling module.

4. The system for producing ethylene from acetylene and wastewater driven by renewable energy according to claim 1, characterized in that, The waste heat recovery module includes a waste heat recovery low-temperature wastewater evaporation module, the output of which is also connected to a condensation module. One output of the condensation module is connected to a vacuum module, and the other output is connected to a buffer water tank. The output of the buffer water tank is connected to a water replenishment module. The water replenishment module is connected to an ethylene-side gas-liquid separation module. The water replenishment module is also externally connected to a water outlet for supplying surplus fresh water.

5. The system for producing ethylene from acetylene and wastewater driven by renewable energy according to claim 1, characterized in that, The acetylene-to-ethylene electrolyzer adopts a structure design with cathode and anode electrodes and an anion exchange membrane, and uses water as a proton source to achieve electrocatalytic reaction.

6. A method for producing ethylene from acetylene and wastewater using a renewable energy-driven system based on any one of claims 1 to 5, characterized in that, Includes the following steps: S1. Gas-liquid mixing and electrocatalysis: Clean acetylene and electrolyte enter the gas-liquid ratio mixing module at a preset mass ratio. After being mixed evenly, the gas-liquid mixture enters the acetylene-to-ethylene electrolysis cell module. Power is supplied by the rectifier power supply module. Acetylene and water undergo an electrocatalytic reaction to produce ethylene. S2. Product separation and drying: After being processed by the gas-liquid separation module and the washing and cooling module, the reaction products enter the drying module to dry ethylene.

7. Based on the method of claim 6, clean acetylene and electrolyte are introduced into the gas-liquid ratio mixing module at a ratio of 1:(10~20).

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