A multi-stage purification method and system of absorbent in carbon capture waste liquid

Abstract

This application relates to the field of carbon capture wastewater treatment technology, and in particular to a multi-stage purification method and system for absorbents in carbon capture wastewater. The method includes: performing wastewater pretreatment, multi-stage filtration, primary deweighting, distillation purification, and final deep purification steps; the system includes a pretreatment unit, a multi-stage filtration unit, a deweighting unit, a distillation unit, a deep purification unit, and a control unit. This application removes degradation products through the synergistic effect of chemical conditioning and physical filtration, achieves thorough separation of effective components through primary deweighting and distillation fractionation, and combines a vacuum environment to reduce operating temperature and slow down secondary degradation. This application can solve the problem that a single method cannot simultaneously achieve product purity and recovery rate, significantly improves the purity of the regenerated absorbent, realizes efficient resource regeneration of wastewater, reduces system energy consumption and operating costs, and has significant economic and environmental value.

Description

Technical Field

[0001] This invention relates to the field of carbon capture technology, and in particular to a multi-stage purification method and system for absorbents in carbon capture wastewater. Background Technology

[0002] In the chemical absorption carbon capture process, absorbents such as amines generate a certain amount of waste liquid after long-term recycling due to oxidation, thermal degradation, and impurity accumulation. This waste liquid typically contains a high proportion of effective absorbent components, making its recycling highly valuable both economically and environmentally. Currently, conventional distillation or neutralization precipitation processes are commonly used to treat this type of waste liquid. However, due to the diverse types of degradation products and impurities in the waste liquid, single treatment methods have limitations in improving the purity of the recovered products, and the energy consumption control and continuous operation levels in the process still need further optimization. These factors have a certain impact on the efficient resource-based recycling of absorbents. Summary of the Invention

[0003] This invention provides a multi-stage purification method and system for absorbents in carbon capture wastewater. The method and system use a combination of multi-stage physical separation and chemical conditioning to treat amine absorbent wastewater containing degradation products and impurities generated during carbon capture, and extract the effective absorbent components therein.

[0004] A multi-stage purification method for absorbent in carbon capture wastewater, the method comprising:

[0005] Waste liquid pretreatment steps: The carbon capture waste liquid to be treated is transported to the pretreatment reactor, a preset proportion of chemical conditioning agent is added to the pretreatment reactor, and the stirring device in the pretreatment reactor is started to mix, so that the thermal degradation products in the waste liquid undergo complexation or precipitation reaction with the chemical conditioning agent to obtain a pretreated mixture.

[0006] Perform a multi-stage filtration step: pass the pretreated mixture through a multi-stage filtration device with filter elements of different pore sizes in sequence. The multi-stage filtration device intercepts the suspended solids, particulate matter and complex precipitates in the pretreated mixture to obtain a pre-purified filtrate.

[0007] Perform the primary deweighting step: introduce the filtrate into the primary evaporator, adjust the flow rate of the heating heat carrier in the primary evaporator to maintain the material temperature in the primary evaporator within the first predetermined temperature range, and at the same time maintain the pressure in the primary evaporator within the first predetermined pressure range through the vacuum system, so that the light components and effective absorbent components in the filtrate are vaporized to generate the first gas phase component, and the remaining heavy component waste residue is discharged.

[0008] The distillation purification step is performed as follows: the first gaseous component is condensed and fed to the middle feed port of the distillation column. The heating power of the reboiler at the bottom of the distillation column is adjusted to maintain the bottom temperature in the second predetermined temperature range. The cooling medium flow rate of the condenser at the top of the column is adjusted to maintain the reflux ratio at the top of the column in the preset reflux ratio range. Multiple vapor-liquid equilibrium exchanges are performed in the distillation column. A high-purity absorbent gas phase is obtained from the top output end of the distillation column, and the absorbent product liquid is obtained after condensation.

[0009] Perform the end-of-pipe deep purification step: pump the finished absorbent liquid to a deep purification column filled with preset adsorption packing material, and use the adsorption packing material to remove the residual trace metal ions and pigment impurities in the finished absorbent liquid to produce regenerated absorbent.

[0010] Optionally, the above method includes the step of performing waste liquid pretreatment, which comprises:

[0011] The liquid level in the pretreatment reactor is monitored using a liquid level sensor.

[0012] When the liquid level reaches the preset liquid level threshold, the feed pump is stopped and the conditioning agent metering pump is turned on to inject conditioning agent into the reactor according to the preset mass percentage.

[0013] The drive motor of the stirring device is controlled to run at a preset speed and maintain a preset stirring cycle, so that the conditioner can fully contact and react with the impurities in the waste liquid.

[0014] Optionally, the multi-level filtering step in the above method includes:

[0015] The pressure difference value is monitored by pressure transmitters installed at both ends of the inlet and outlet of the multi-stage filtration device.

[0016] When the differential pressure value exceeds the preset differential pressure threshold, a backwashing command is executed, or the system switches to a parallel-connected backup filter branch to maintain the continuity of material flow.

[0017] Optionally, the above method may include performing the initial deweighting step, which includes:

[0018] The temperature signal of the material inside the primary evaporator is collected in real time using a temperature sensor;

[0019] The controller adjusts the opening of the electric regulating valve connected to the heating pipeline and changes the flow rate of the heat carrier based on the deviation between the material temperature signal and the first predetermined temperature range.

[0020] The pressure signal at the top of the primary evaporator is collected using a pressure sensor, and the frequency of the vacuum pump inverter is adjusted according to the pressure signal to maintain the evaporation pressure within the first predetermined pressure range.

[0021] Optionally, the above method includes the following step: performing distillation purification.

[0022] Multiple temperature sampling points are set on the trays or packing layers of the distillation column to obtain temperature gradient distribution data inside the column;

[0023] Based on the temperature gradient distribution data, the heat input of the reboiler and the reflux liquid flow rate at the top of the column are dynamically adjusted.

[0024] An electrical conductivity analyzer or a refractive index detector is installed at the top of the distillation column to monitor the purity of the product in real time.

[0025] If the purity index is lower than the preset purity threshold, increase the reflux ratio until the product meets the preset purity requirements.

[0026] Optionally, the above method includes performing the end-of-pipe deep purification step, which comprises:

[0027] The finished absorbent solution is passed through the depth purification column at a preset space velocity;

[0028] The adsorption packing material filled in the deep purification column includes at least one of ion exchange resin, activated carbon, and molecular sieve.

[0029] Samples are collected periodically from the outlet of the deep purification column. The saturation state of the adsorption packing is determined by analyzing the results. When the saturation state is reached, the process is switched to regeneration or the packing is replaced.

[0030] A multi-stage purification system for absorbent in carbon capture wastewater includes:

[0031] The pretreatment unit includes a pretreatment reactor. The top of the pretreatment reactor is provided with a waste liquid inlet and a conditioning agent inlet. The interior of the pretreatment reactor is provided with a stirring paddle, which is connected to a geared motor installed on the reactor cover via a coupling.

[0032] A multi-stage filtration unit, the inlet of which is connected to the bottom outlet of the pretreatment reactor via a first delivery pump and pipeline, the multi-stage filtration unit comprising at least two filters arranged in series, and a differential pressure gauge installed on the housing of each filter;

[0033] The deweight removal unit includes a primary evaporator, the feed end of which is connected to the outlet of the multi-stage filtration unit. The primary evaporator has a waste residue discharge port at the bottom and a first gas phase outlet at the top. The first gas phase outlet is connected to the distillation unit through a first condenser.

[0034] A distillation unit, comprising a distillation column, the column body of which is provided with a heat insulation layer, a reboiler connected to the bottom of the distillation column, a second condenser and a reflux distributor connected to the top of the distillation column, and a feed pipeline connected to the first condenser on the side of the distillation column.

[0035] A deep purification unit, comprising a deep purification column, wherein the inlet of the deep purification column is connected to the output end of the reflux distributor via a second delivery pump, and the outlet of the deep purification column is connected to the finished product storage tank.

[0036] The control unit is connected to the first delivery pump, the second delivery pump, the geared motor, the reboiler, the second condenser, and the sensors installed in each unit.

[0037] Optionally, the pretreatment reactor is provided with a heating jacket, which is connected to an external heat source via a pipe to maintain a preset reaction temperature inside the reactor.

[0038] Optionally, in the above system, the primary evaporator is a thin-film evaporator or a scraped evaporator. The primary evaporator is equipped with a rotating scraper, which is driven by a film-forming motor located at the top of the evaporator to form a uniform liquid film on the inner wall of the evaporator.

[0039] Optionally, in the above system, the distillation column is a packed column or a plate column, and the column is filled with amine-resistant structured metal packing or ceramic random packing to increase the contact area between the vapor and liquid phases.

[0040] Optionally, the system described above may also include a vacuum unit, which is connected to the primary evaporator and the distillation column via a vacuum buffer tank and vacuum pipelines, respectively, to provide the negative pressure environment required for each stage of the purification process.

[0041] Optionally, the system further includes a heat pump recovery unit, wherein the heat absorption end of the heat pump recovery unit is connected to the second condenser and the heat release end is connected to the reboiler, for transferring the latent heat of condensation of the gas phase at the top of the column to the reboiler at the bottom of the column.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] This invention provides a multi-stage purification method and system for absorbents in carbon capture wastewater. Through a multi-stage coupled process of pretreatment, multi-stage filtration, heavy evaporation, distillation purification, and deep purification, it solves the problem of traditional single-treatment methods struggling to balance product purity and recovery rate. Utilizing the synergistic effect of chemical conditioning and physical filtration, complex degradation products in the wastewater are removed first, reducing the risk of scaling during subsequent thermal separation. The staged setup of primary heavy evaporation and distillation achieves complete separation of heavy component impurities from effective components, significantly improving the purity of the regenerated absorbent. Furthermore, maintaining a vacuum environment in the system lowers the operating temperature, slowing down secondary degradation of the absorbent during purification. The control unit's automated adjustment of key parameters such as temperature, pressure, and reflux ratio replaces manual intervention, improving the stability of continuous operation and the consistency of product quality. The application of a heat pump recovery unit internally recycles the heat from the top of the tower, reducing the overall energy consumption of the system. This invention not only achieves efficient resource-based regeneration of waste absorbents and reduces hazardous waste emissions, but also reduces operating costs through process optimization, demonstrating significant economic benefits and environmental value. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the 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 based on these drawings without creative effort.

[0045] Figure 1 This is a flowchart of a multi-stage purification method for absorbent in carbon capture waste liquid, provided by an embodiment of the present invention.

[0046] Figure 2 This is a system structure diagram of a multi-stage purification system for absorbent in carbon capture waste liquid provided in an embodiment of the present invention;

[0047] Figure 3 A flowchart illustrating the reflux ratio adjustment logic in the distillation and purification step provided in this embodiment of the invention;

[0048] Figure 4 This is a structural block diagram of the pretreatment reactor provided in an embodiment of the present invention;

[0049] Figure 5 This is a hardware connection block diagram of the control unit of a multi-stage purification system provided in an embodiment of the present invention. Detailed Implementation

[0050] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative effort are all within the scope of protection of the present invention.

[0051] In this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. The terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0052] This invention can be used in a wide range of general-purpose or specialized industrial control environments or configurations. Examples include distributed control systems (DCS), programmable logic controllers (PLCs), host computer monitoring systems, industrial IoT platforms, and more.

[0053] This invention provides a multi-stage purification method for absorbent in carbon capture wastewater. The method is applied to a carbon capture wastewater purification system, and its flowchart is shown below. Figure 1 As shown, it specifically includes:

[0054] S1: Perform the waste liquid pretreatment step by adding a chemical conditioner into the pretreatment reactor and mixing it to obtain a pretreated mixture;

[0055] S2: Perform a multi-stage filtration process to intercept solid impurities in the pre-treated mixture through a multi-stage filtration device to obtain a pre-purified filtrate;

[0056] S3: Perform the primary deweighting step, adjust the process parameters of the primary evaporator to vaporize the effective absorbent components and generate the first gas phase component;

[0057] S4: Perform the distillation purification step, carry out vapor-liquid equilibrium exchange in the distillation column, and obtain a high-purity absorbent product liquid;

[0058] S5: Perform the final deep purification step, using a deep purification column to remove residual trace impurities and produce a regenerable absorbent.

[0059] Based on the steps S1-S5 above, the following specific explanations are provided:

[0060] S1: Perform waste liquid pretreatment steps.

[0061] It should be noted that the pretreatment reactor is a closed container with a corrosion-resistant lining, used to allow the thermal degradation products in the waste liquid to react fully with the chemical conditioning agent.

[0062] Feed control in the pretreatment unit can employ various logic methods, including level-linked control and proportional metering control. Level-linked control refers to the system automatically switching the feed state when the liquid level in the pretreatment reactor meets a set threshold. Proportional metering control refers to precisely adjusting the amount of conditioning agent added based on the initial component analysis data of the waste liquid.

[0063] In one optional implementation, the waste liquid pretreatment is performed via liquid level linkage as follows:

[0064] The liquid level L in the pretreatment reactor is collected in real time. When L reaches the first preset liquid level threshold Lmax, the feed pump is stopped and the conditioning agent metering pump is turned on to inject chemical conditioning agent into the reactor according to the preset mass percentage Wadd. The stirring device is started and the preset stirring cycle t1 is maintained to make the oxidation degradation products in the waste liquid undergo complexation reaction.

[0065] Understandably, carbon capture wastewater enters the reactor via a delivery pipeline. During the feeding process, a level sensor monitors the liquid level changes in real time. When the liquid level reaches Lmax, the control unit outputs an electrical signal to close the feed electric valve. Subsequently, the conditioning agent metering pump operates according to a preset proportioning instruction. The chemical conditioning agent may include reducing agents, complexing agents, or precipitants. Under the shearing action of the agitator, the conditioning agent comes into full contact with heavy metal ions or degraded organic acids in the wastewater, forming macromolecular complexes or insoluble precipitates, thereby altering the physicochemical properties of the wastewater and reducing the risk of scaling during subsequent evaporation.

[0066] S2: Perform multi-level filtering steps.

[0067] Multi-stage filtration devices are equipped with filter elements of different filtration precision to achieve graded retention.

[0068] In one alternative implementation, the multi-level filtering is performed as follows:

[0069] Real-time monitoring of the pressure difference ΔP between the inlet and outlet of the multi-stage filtration device; when ΔP exceeds the preset pressure difference threshold ΔPset, triggering a self-cleaning command or switching to a backup filtration branch; controlling the material flow rate to maintain in the first predetermined flow range Q1, so that the pretreated mixture passes through the coarse filter element and the fine filter element in sequence.

[0070] Understandably, the primary filtration stage mainly targets large particles with a diameter greater than 50 μm, while the secondary filtration stage targets fine suspended matter with a diameter between 1 and 5 μm. By installing pressure transmitters on the pipeline, the system can calculate ΔP in real time. If ΔP > ΔPset, it indicates that the filter element is clogged. At this time, the control unit activates the parallel redundant pipeline to ensure the continuity of the purification process and avoid production interruptions due to shutdown for cleaning.

[0071] S3: Perform the initial deweighting step.

[0072] The primary evaporator can be a falling film evaporator or a scraped evaporator, and its function is to separate the volatile effective absorbent from the non-volatile heavy component waste residue.

[0073] Specifically, the primary deweighting process is as follows: the material temperature T1 and evaporation pressure P1 inside the primary evaporator are collected; the flow rate of the heat transfer fluid is adjusted according to the deviation between T1 and the first predetermined temperature range [Ta, Tb]; and the operating frequency f1 of the vacuum pump is adjusted according to the deviation between P1 and the first predetermined pressure range [Pa, Pb].

[0074] It should be noted that maintaining a negative pressure environment in the system can effectively reduce the boiling point of the absorbent. For example, under operating conditions where P1 is -0.09 to -0.095 MPa, the effective components can vaporize at a lower T1, thereby avoiding secondary thermal degradation of the absorbent caused by high temperatures.

[0075] S4: Perform the distillation and purification step.

[0076] Distillation columns are the core equipment for achieving high-precision separation of components.

[0077] Furthermore, the specific method for performing distillation purification is as follows: acquire temperature sampling point data at different heights of the distillation column and construct a temperature gradient model within the column; based on the temperature gradient model, adjust the heat input power Wboil of the reboiler and the reflux ratio R at the top of the column; and monitor the refractive index or conductivity of the product at the top of the column online.

[0078] Specifically, the adjustment method is as follows: identify the purity index η of the product; when η is lower than the preset purity threshold ηmin, increase the reflux ratio R by adjusting the reflux distributor.

[0079] Inside the distillation column, the rising gas phase and the descending liquid phase undergo multiple mass and heat transfers on the packing surface. Lighter impurities with lower boiling points (such as water and small-molecule amines) accumulate at the top of the column, while the target absorbent components condense and gather in specific sections. By precisely controlling R, the separation accuracy of the products can be effectively adjusted.

[0080] S5: Perform the end-of-pipe deep purification step.

[0081] The deep purification column is filled with functionalized adsorption packing material.

[0082] Optionally, specific methods for deep purification include: controlling the finished liquid to pass through the deep purification column at a preset space velocity (SV); using adsorption packing to intercept residual pigment components and metal ions; and monitoring the material color index at the column outlet.

[0083] It should be noted that the adsorption packing material can be modified activated carbon or macroporous ion exchange resin. Although the absorbent after distillation has a high purity, it may still contain trace amounts of oxidative discoloration substances. Deep purification can restore the color and ion content of the regenerated absorbent to their original specifications.

[0084] By applying the methods provided in the above embodiments, the system can achieve fully automated purification of carbon capture waste liquid throughout the entire process. Compared with traditional processes, this invention, through the coupling of pretreatment and multi-stage thermal separation, not only improves the purity of the product but also significantly reduces the system's operating energy consumption.

[0085] Based on the above-described method applied to purification systems, embodiments of the present invention also provide a multi-stage purification system for absorbents in carbon capture wastewater, such as... Figure 2 As shown, the system includes:

[0086] The pretreatment unit 100 includes a pretreatment reactor, a stirring paddle, and a geared motor. The pretreatment reactor has a filling port at the top and a liquid level sensor inside. The stirring paddle is driven by the geared motor to achieve material homogenization.

[0087] The multi-stage filtration unit 200 has its inlet connected to the outlet of the pretreatment reactor via a first delivery pump. The multi-stage filtration unit 200 includes a first filter and a second filter connected in series, and each filter is equipped with a differential pressure gauge.

[0088] The deslagging unit 300 includes a primary evaporator. The feed end of the primary evaporator is connected to the multi-stage filtration unit 200, which has a first gas phase outlet at the top and a waste residue collection tank at the bottom.

[0089] The distillation unit 400 includes a distillation column, a reboiler, and a second condenser. The feed line of the distillation column is linked to the vapor outlet of the primary evaporator, and a reflux distribution device is installed at the top of the column.

[0090] The deep purification unit 500 includes a deep purification column, the inlet of which is connected to the output end of the distillation unit 400 via a second transfer pump.

[0091] The control unit 600 is electrically connected to the pump, motor, actuator valve and sensor in each of the above units.

[0092] like Figure 3 As shown, Figure 3This diagram illustrates the signal interaction between the control unit 600 and various hardware components. The control unit 600 can be an industrial computer or a PLC cluster, and it integrates a process parameter adjustment module.

[0093] In this embodiment of the invention, the primary evaporator is externally equipped with a high-efficiency heat-insulating jacket, and internally equipped with a rotating scraper device. The rotating scraper is driven by a film-forming motor, enabling the formation of a uniform liquid film with a thickness of 0.5~2mm on the inner wall of the evaporator. This structural design significantly increases the heating area, shortens the material heating time, and effectively solves the problems of high energy consumption and easy scaling mentioned in the background art.

[0094] Furthermore, the distillation column is filled with alkali-resistant 316L stainless steel structured packing with a specific surface area ranging from 250 to 500 m²·m⁻³. This configuration provides ample space for vapor-liquid contact, ensuring stable purification efficiency during continuous operation.

[0095] In addition, the system includes a heat pump recovery unit, whose heat absorption end exchanges heat with the second condenser, and whose heat release end is coupled to the reboiler. Through this thermally integrated design, the latent heat of condensation of the gas phase at the top of the column can be recovered and utilized, and the overall energy saving rate of the system can reach 20% to 35%.

[0096] The multi-stage purification system provided by this invention enables the resource utilization of carbon capture waste liquid and reduces the treatment cost of hazardous waste. The system has a clear architecture, with close coordination between units, and achieves continuous production from waste liquid to high-purity regenerated absorbent through automated control.

[0097] In the specific implementation process, the workflow of this system is as follows:

[0098] First, the amine absorbent waste liquid to be treated is pumped from the external storage tank into the pretreatment reactor via a first transfer pump. When the liquid level sensor in the pretreatment reactor detects that the liquid level has reached a preset height, it sends a signal to the control unit. The control unit then shuts off the first transfer pump and starts the conditioning agent metering pump. The conditioning agent metering pump adds chemical conditioning agent into the reactor according to a preset ratio. Subsequently, a geared motor drives the agitator to rotate, ensuring thorough mixing of the waste liquid and the conditioning agent within the pretreatment reactor. During this process, the oxidative degradation products and thermal degradation products in the waste liquid react with the conditioning agent to form large molecular complexes or solid precipitates.

[0099] After the mixing reaction is complete, the material is fed into a multi-stage filtration unit. The material first enters the first-stage coarse filter to remove larger diameter solid particles, and then enters the second-stage fine filter to intercept tiny precipitates and suspended solids. Differential pressure gauges installed at both ends of the filter monitor the filtration resistance in real time. When the value displayed on the differential pressure gauge exceeds a preset alarm threshold, the control unit switches the valve, directing the material to another set of filters connected in parallel, while simultaneously performing a cleaning operation on the current filter.

[0100] The filtrate after filtration enters the primary evaporator of the deweighting unit. In the primary evaporator, the material is heated under vacuum and negative pressure. Due to the significant difference in boiling points between the effective absorbent component and the heavy component impurities (such as polymers, inorganic salts, etc.), the effective absorbent component and water vaporize and are discharged from the first gas phase outlet at the top of the primary evaporator, while the heavy component impurities that cannot vaporize settle to the bottom and are periodically discharged through the waste discharge port.

[0101] The first gaseous component discharged from the primary evaporator enters the first condenser and is transformed into a liquid state, subsequently entering the distillation column. The distillation column is the core step in purification. The reboiler provides heat to vaporize the material in the bottom of the column and rises, while the second condenser provides cooling to condense and reflux the vaporous portion at the top of the column. On the surface of the trays or packing in the distillation column, the rising vapor and the descending liquid undergo multiple heat and mass exchanges. Lighter impurities with lower boiling points accumulate at the top of the column, while the more potent absorbent components with higher boiling points accumulate at the bottom of the column (or are drawn off from the side stream depending on their characteristics). By precisely adjusting the heat load of the reboiler and the reflux ratio at the top of the column, the mass fraction of the potent absorbent in the vapor produced at the top of the column reaches the preset purity standard.

[0102] Finally, the absorbent obtained from distillation enters the deep purification unit. The adsorption packing material within the deep purification column further captures trace amounts of discoloration components and metal ions remaining in the absorbent through physical adsorption or chemical exchange. Ultimately, the product exiting the deep purification column is a high-purity regenerated absorbent, with all its indicators restored to the preset recycling standards, ready for reuse in the carbon capture system.

[0103] The entire system operates under the monitoring of the control unit. The control unit receives data signals from various pressure transmitters, temperature sensors, flow meters, and online analyzers, and uses a preset control algorithm to output control commands to each pump, motor, and regulating valve to maintain the system's stable operation within the preset process parameter range.

[0104] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to mutually. The system embodiments described above are merely illustrative, and the units described as separate components may or may not be physically separate. Some or all of the modules can be selected to achieve the purpose of the solution in this embodiment according to actual needs.

Claims

1. A multi-stage purification method for absorbent in carbon capture wastewater, characterized in that, The method includes: Waste liquid pretreatment steps: The carbon capture waste liquid to be treated is transported to the pretreatment reactor, a preset proportion of chemical conditioning agent is added to the pretreatment reactor, and the stirring device in the pretreatment reactor is started to mix, so that the thermal degradation products in the waste liquid undergo complexation or precipitation reaction with the chemical conditioning agent to obtain a pretreated mixture. Perform a multi-stage filtration step: pass the pretreated mixture through a multi-stage filtration device with filter elements of different pore sizes in sequence. The multi-stage filtration device intercepts the suspended solids, particulate matter and complex precipitates in the pretreated mixture to obtain a pre-purified filtrate. Perform the primary deweighting step: introduce the filtrate into the primary evaporator, and maintain the material temperature in the primary evaporator within the first predetermined temperature range [Ta, Tb] by adjusting the flow rate of the heating heat carrier in the primary evaporator. At the same time, maintain the pressure in the primary evaporator within the first predetermined pressure range [Pa, Pb] by the vacuum system, so that the light components and effective absorbent components in the filtrate are vaporized to generate the first gas phase component, and the remaining heavy component waste residue is discharged. The distillation purification step is performed as follows: the first gaseous component is condensed and fed to the middle feed port of the distillation column. The temperature of the column bottom is maintained in the second predetermined temperature range by adjusting the heating power of the reboiler at the bottom of the distillation column, and the cooling medium flow rate of the condenser at the top of the column is adjusted to maintain the reflux ratio R at the top of the column in the preset reflux ratio range. Multiple vapor-liquid equilibrium exchanges are performed in the distillation column. The absorbent gas phase is obtained from the top output end of the distillation column, and the absorbent product liquid is obtained after condensation. Perform the end-of-pipe deep purification step: pump the finished absorbent liquid to a deep purification column filled with preset adsorption packing material, and use the adsorption packing material to remove residual metal ions and pigment impurities from the finished absorbent liquid to produce regenerated absorbent.

2. The multi-stage purification method for absorbent in carbon capture wastewater according to claim 1, characterized in that, The waste liquid pretreatment step includes: The liquid level L inside the pretreatment reactor is monitored by a liquid level sensor. When the liquid level L reaches the first preset liquid level threshold Lmax, the feed pump is stopped and the conditioner metering pump is turned on to inject conditioner into the reactor according to the preset mass percentage Wadd. The drive motor of the stirring device is controlled to run at a preset speed and maintain a preset stirring cycle t1, so that the conditioning agent can fully contact and react with the impurities in the waste liquid.

3. The multi-stage purification method for absorbent in carbon capture wastewater according to claim 1, characterized in that, The multi-level filtering steps include: The pressure difference value ΔP is monitored by pressure transmitters installed at both ends of the inlet and outlet of the multi-stage filtration device. When the differential pressure value ΔP exceeds the preset differential pressure threshold ΔPset, a backwashing command is executed, or the system switches to a parallel-connected backup filter branch to maintain the continuity of material flow, wherein the material flow rate is maintained in the first predetermined flow range Q1.

4. The multi-stage purification method for absorbent in carbon capture wastewater according to claim 1, characterized in that, The initial de-weighting step includes: The material temperature T1 signal inside the primary evaporator is collected in real time using a temperature sensor; The controller adjusts the opening of the electric regulating valve connected to the heating pipeline and changes the flow rate of the heat carrier based on the deviation between the material temperature T1 signal and the first predetermined temperature range [Ta, Tb]. The pressure signal P1 at the top of the primary evaporator is acquired using a pressure sensor, and the frequency f1 of the vacuum pump inverter is adjusted according to the pressure signal P1 to maintain the evaporation pressure within the first predetermined pressure range [Pa, Pb].

5. The multi-stage purification method for absorbent in carbon capture wastewater according to claim 1, characterized in that, The distillation and purification step includes: Multiple temperature sampling points are set on the trays or packing layers of the distillation column to obtain temperature gradient distribution data inside the column; Based on the temperature gradient distribution data, the heat input power Wreboil of the reboiler and the reflux liquid flow rate at the top of the column are dynamically adjusted. An electrical conductivity analyzer or a refractive index detector is installed at the top of the distillation column to monitor the purity index η of the product in real time. If the purity index η is lower than the preset purity threshold ηmin, increase the reflux ratio R until the product meets the preset purity requirements.

6. The multi-stage purification method for absorbent in carbon capture wastewater according to claim 1, characterized in that, The terminal deep purification step includes: The finished absorbent solution is passed through the depth purification column at a preset space velocity (SV). The adsorption packing material filled in the deep purification column includes at least one of ion exchange resin, activated carbon, and molecular sieve. Samples are collected periodically from the outlet of the deep purification column. The saturation state of the adsorption packing is determined by analyzing the results. When the saturation state is reached, the process is switched to regeneration or the packing is replaced.

7. A multi-stage purification system for absorbent in carbon capture wastewater, characterized in that, include: The pretreatment unit (100) includes a pretreatment reactor. The top of the pretreatment reactor is provided with a waste liquid inlet and a conditioning agent inlet. The interior of the pretreatment reactor is provided with a stirring paddle, which is connected to a geared motor installed on the reactor cover via a coupling. A multi-stage filtration unit (200) is provided, the inlet of which is connected to the bottom outlet of the pretreatment reactor via a first delivery pump and a pipeline. The multi-stage filtration unit includes at least two filters arranged in series, and a differential pressure gauge is installed on the housing of each filter. The deweight removal unit (300) includes a primary evaporator. The feed end of the primary evaporator is connected to the outlet of the multi-stage filtration unit (200). The bottom of the primary evaporator is provided with a waste residue discharge port, and the top is provided with a first gas phase outlet. The first gas phase outlet is connected to the distillation unit (400) through a first condenser. A distillation unit (400) includes a distillation column, the column body of which is provided with a heat insulation layer, a reboiler connected to the bottom of the distillation column, a second condenser and a reflux distributor connected to the top of the distillation column, and a feed pipeline connected to the first condenser on the side of the distillation column. A deep purification unit (500) includes a deep purification column. The inlet of the deep purification column is connected to the output end of the reflux distributor via a second delivery pump, and the outlet of the deep purification column is connected to the finished product storage tank. The control unit (600) is connected to the first delivery pump, the second delivery pump, the geared motor, the reboiler, the second condenser, and the sensors disposed in each unit.

8. A multi-stage purification system for absorbent in carbon capture wastewater according to claim 7, characterized in that: The pretreatment reactor is equipped with a heating jacket, which is connected to an external heat source via a pipe. The primary evaporator is a thin-film evaporator or a scraped evaporator. The primary evaporator is equipped with a rotating scraper inside, which is driven by a film-forming motor located at the top of the evaporator to form a liquid film with a thickness of 0.5~2mm on the inner wall of the evaporator.

9. A multi-stage purification system for absorbent in carbon capture wastewater according to claim 7, characterized in that: The distillation column is a packed column or a plate column, and is filled with amine-resistant structured metal packing or ceramic random packing. The specific surface area of ​​the structured metal packing is in the range of 250~500 m²·m⁻³.

10. A multi-stage purification system for absorbent in carbon capture wastewater according to claim 7, characterized in that: The system also includes a vacuum unit and a heat pump recovery unit. The vacuum unit is connected to the primary evaporator and the distillation column via a vacuum buffer tank and vacuum pipelines, respectively. The heat absorption end of the heat pump recovery unit is connected to the second condenser, and the heat release end is connected to the reboiler. It is used to transfer the latent heat of condensation of the gas phase at the top of the column to the reboiler at the bottom of the column. The heat pump recovery unit enables the overall energy saving rate of the system to be in the range of 20% to 35%.

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