Organic carbon pump system for VOCs recovery, cycle construction method and evaluation method thereof

Abstract

The invention relates to the technical field of industrial exhaust air VOCs recovery, in particular to an organic carbon pump system for VOCs recovery, a circulation construction method and an evaluation method thereof, and industrial exhaust air VOCs recovery is achieved through a first-stage organic carbon pump or a multi-stage organic carbon pump; the primary organic carbon pump comprises an adsorption unit, a heating unit and a condensation unit; the multi-stage organic carbon pump is formed by connecting a plurality of first-stage organic carbon pumps in series; a VOCs adsorption condensation recovery thermodynamic cycle is constructed in a P-q diagram and a Claperon diagram through a thermodynamic means, and the energy efficiency of the organic carbon pump system is evaluated based on a first law of thermodynamics and a second law of thermodynamics. According to the method, the proper organic carbon pump stage number can be flexibly selected according to the concentration and boiling point of the VOCs, the adaptability of VOCs recovery is improved, industrial exhaust VOCs can be more accurately adsorbed and desorbed, the low-concentration VOCs can be more effectively concentrated and recovered step by step, and the recovery effect is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of industrial exhaust VOCs recovery, and in particular to an organic carbon pump system for VOCs recovery, a circulation construction method and an evaluation method thereof. Background Art

[0002] In the context of accelerated modern industrialization, the amount of organic solvents used in many industries such as coatings, inks, pharmaceuticals, and lithium batteries is large, and the emission of volatile organic compounds (VOCs) is prominent. As a high-value pollutant with high value in industrial production, the recycling of VOCs has significant economic and environmental benefits.

[0003] At present, mainstream VOCs treatment technologies mainly include destructive treatment methods such as regenerative thermal oxidation (RTO) and regenerative catalytic oxidation (RCO). These technologies decompose VOCs into CO2 and H2O through oxidation and dominate the market. manufacture The linear economic form of "waste" not only causes a waste of organic solvent resources, but also aggravates the problem of carbon emissions. Therefore, in order to improve the VOCs treatment and recovery performance, it is proposed to adopt a cascade adsorption mode such as CN111013318A and a two-stage condensation mode such as CN221825639U for VOCs recovery. However, the existing technology is only an improvement on the performance of various hardware in the VOCs treatment system, and still lacks basic innovation at the thermodynamic level, and has the problems of low cycle efficiency and poor recovery effect.

[0004] At the same time, in the existing technology of thermodynamic carbon pumps for CO2 recovery, such as CN107042053A, the carbon dioxide carbon pump needs to be compressed and stored for the treatment of the enriched product, and then sent to the downstream factory for secondary conversion. Therefore, under the premise of different recovery principles and purposes, it cannot be applied to the recovery of industrial exhaust VOCs. Summary of the invention

[0005] The purpose of the present invention is to provide an organic carbon pump system, a circulation construction method and an evaluation method thereof for VOCs recovery, so as to solve the problems of lack of basic innovation at the thermodynamic level in the prior art, low circulation efficiency and poor recovery effect.

[0006] The present invention provides an organic carbon pump system for VOCs recovery, wherein the VOCs recovery in the industrial exhaust air is achieved by a primary organic carbon pump or a multi-stage organic carbon pump; The primary organic carbon pump at least includes an adsorption unit, a heating unit and a condensation unit; The heating unit is used to adjust the working temperature of the adsorption unit to the preheating temperature T 预热Or the desorption temperature T 脱附 ; The input end of the adsorption unit serves as the input end of the primary organic carbon pump, and is used to receive the VOCs to be treated, and adsorb the VOCs to be treated at the preheating temperature T 预热 and desorb at the desorption temperature T 脱附 ; The first output end of the adsorption unit is used to output the transferred VOCs after desorption; The input end of the condensation unit is connected to the first output end of the adsorption unit, and is used to condense the transferred VOCs into a liquid state; the output end of the condensation unit serves as the output end of the primary organic carbon pump, and is used to output the liquid VOCs; The multi-stage organic carbon pump is composed of a plurality of the primary organic carbon pumps connected in series; for the plurality of the primary organic carbon pumps that are neither the first nor the last in the multi-stage organic carbon pump, the first output end of the adsorption unit of the previous primary organic carbon pump is connected to the input end of the next primary organic carbon pump.

[0007] According to an organic carbon pump system for VOCs recovery provided by the present invention, the heating unit heats the adsorption unit by direct heating or indirect heating; The direct heating uses a heating gas to perform convective purge heating on the adsorption unit, and the heating gas includes hot air, water vapor or hot nitrogen; The indirect heating uses a heating coil or a heating jacket, and the heat medium flowing through the heating coil or the heating jacket is used to perform heat conduction heating on the adsorption unit.

[0008] According to an organic carbon pump system for VOCs recovery provided by the present invention, the primary organic carbon pump or the multi-stage organic carbon pump is selected according to the concentration and boiling point of VOCs in industrial exhaust gas; If the concentration of VOCs in industrial exhaust gas is greater than a first preset concentration or the boiling point of VOCs in industrial exhaust gas is greater than a first preset boiling point, the primary organic carbon pump is selected; If the concentration of VOCs in industrial exhaust gas is less than a first preset concentration or the boiling point of VOCs in industrial exhaust gas is less than a first preset boiling point, the multi-stage organic carbon pump is selected.

[0009] The present invention also provides a method for constructing a cycle for VOCs recovery, which is implemented based on the above organic carbon pump system, and the method for constructing the cycle includes: The cyclic process is denoted as point 1 to point 2 to point 3 to point 4 to point 5 to point 1. Among them, point 1 is the state after the adsorption unit inside the organic carbon pump system is desorbed and cooled, which is the initial state of the adsorption process. The adsorption capacity of the adsorption unit is q 0, and its equilibrium pressure at the adsorption temperature T 吸附 is P 排放 ; point 2 is the end state of the adsorption process, which is the saturated state at the adsorption pressure P 吸附 . The adsorption capacity of the adsorption unit is q 2. At this time, the organic carbon pump system is switched to the desorption and regeneration mode; point 3 is the end state of the preheating process, and the temperature of the adsorption unit reaches the preheating temperature T 预热 . At this time, the adsorption unit reaches the equilibrium adsorption state at the condensation pressure P 冷凝 ; point 4 is the end state of desorption, and the temperature of the adsorption unit reaches the desorption temperature T 脱附 . At this time, the adsorption unit reaches the P 冷凝 equilibrium adsorption state q 1; point 5 is the end state of the transfer process, and the adsorption capacity of the adsorption unit drops to q 0.

[0010] According to a cyclic construction method for VOCs recovery provided by the present invention, the adsorption process of VOCs in the organic carbon pump system satisfies the Sips adsorption isotherm model; the formula of the Sips adsorption isotherm model is as follows: (1) (2) (3) In formulas (1) to (3), P n is the nth power of P , P is the partial pressure of VOCs; is the equilibrium adsorption capacity; q m ( T ) is the maximum adsorption capacity at the temperature T , b ( T ) is the Sips model coefficient at the temperature T , q m0 ,q m1 , b 0, b 1, and n are all fitting parameters; The condensation process of VOCs in the organic carbon pump system satisfies the Claperon equation; the Claperon equation is as follows: (4) In formula (4), k , b are all fitting parameters, and their values are related to the types of VOCs; By logarithmic linear transformation, formulas (1) to (3) are converted into the logarithmic relationship form of -1 / T being ln P to obtain: (5).

[0011] The present invention also provides an evaluation method for the energy efficiency of the organic carbon pump system, and evaluates the energy efficiency of the organic carbon pump system based on the first law of thermodynamics and the second law of thermodynamics; The formula of the first law of thermodynamics is as follows: (6) In formula (6), E is the energy consumption for VOCs recovery per unit amount of substance, with the unit of kJ / mol; Q H is the heating amount during the desorption process, with the unit of kJ; Q C is the cooling capacity of the chiller during the condensation process, with the unit of kJ; COP is the performance coefficient of the chiller; W S is the shaft work consumed during the adsorption and desorption processes; is the amount of VOCs desorbed; The formula of the second law of thermodynamics is as follows: (7) In formula (7), η is the exergy efficiency of the organic carbon pump system; is the total inflow exergy, which is calculated by formula (8): (8) is the total outflow exergy, which is calculated by formula (9): (9) In formulas (8) and (9), M is the mass of air or VOCs, with the unit of kg;ex is the specific exergy of air or VOCs relative to the reference state 0, where the reference state 0 is air containing saturated VOCs at the exhaust air temperature, in units of kJ / kg, and is calculated by formula (10): (10) In formula (10), h is the enthalpy of air or VOCs, in units of kJ / kg; h 0 is the enthalpy of air or VOCs under the reference state 0, in units of kJ / kg; s is the entropy of air or VOCs, in units of kJ / (kg·K); s 0 is the entropy of air or VOCs under the reference state 0, in units of kJ / (kg·K); T 0 is the temperature of the reference state 0, which is equal to the exhaust air temperature, recorded in thermodynamic temperature, in units of K; c p is the specific heat capacity at constant pressure of air or VOCs, in units of kJ / (kg·K); R is the gas constant of air or VOCs, in units of kJ / (kg·K); P is the partial pressure of air or VOCs, in units of Pa; P 0 is the partial pressure of air or VOCs under the reference state 0, in units of Pa.

[0012] Compared with the prior art, the beneficial effects of an organic carbon pump system for VOCs recovery provided by the present invention are as follows: The recovery of VOCs in the industrial exhaust air of the present invention is realized by a single-stage organic carbon pump or a multi-stage organic carbon pump; the single-stage organic carbon pump at least includes an adsorption unit, a heating unit, and a condensation unit; the heating unit is used to adjust the working temperature of the adsorption unit; the adsorption unit is used to receive the VOCs to be treated, and its first output end is used to output the transferred VOCs after high-concentration desorption; the condensation unit is used to condense the transferred VOCs into a liquid state; the multi-stage organic carbon pump is composed of a plurality of the single-stage organic carbon pumps connected in series. This application can flexibly select the appropriate number of organic carbon pump stages according to the concentration and boiling point of VOCs, improve the adaptability to VOCs recovery, enable more accurate adsorption and desorption treatment of VOCs with different concentrations and boiling points in organic carbon pumps at different levels, and can more effectively concentrate and recover low-concentration VOCs step by step, greatly improving the recovery effect. Description of the Drawings

[0013] Figure 1 is a schematic structural composition diagram of an organic carbon pump system for VOCs recovery in an embodiment of the present invention; Figure 2 is a schematic diagram of the reverse gradient transfer principle of an organic carbon pump system for VOCs recovery in an embodiment of the present invention; Figure 3 is the P - q (pressure - adsorption capacity) schematic diagram of the thermodynamic cycle of the organic carbon pump system for VOCs recovery in the embodiments of the present invention; Figure 4 is the Claperon (temperature - pressure) schematic diagram of the thermodynamic cycle of the organic carbon pump system for VOCs recovery in the embodiments of the present invention. Specific embodiments

[0014] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present disclosure can be more thoroughly understood and the scope of the present disclosure can be fully conveyed to those skilled in the art. It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the drawings and in conjunction with the embodiments.

[0015] See Figure 1 、 Figure 2 , the low - concentration VOCs source of the organic carbon pump system of the present application is the VOCs carried in industrial exhaust gas, and its concentration is C L . The energy input of the organic carbon pump includes the mechanical shaft work of pressure sources such as fans and vacuum pumps W , and the heat from cold and heat sources such as heating and refrigeration equipment Q . The high - concentration VOCs sink of the organic carbon pump is the liquid organic solvent recovered by phase change, and its concentration is C H . Therefore, the industrial waste gas entering the organic carbon pump undergoes enrichment and phase - change recovery treatment by the organic carbon pump, and there is a very small amount of remaining VOCs, whose concentration is far lower than the emission limit specified by national and local emission standards, achieving the near - zero emission goal. Among them, Figure 2 G in L is the Gibbs free energy of the gaseous VOCs source; G H is the Gibbs free energy of the liquid VOCs sink; the VOCs source is similar to the energy source in thermodynamics, continuously providing energy to the system. The gaseous VOCs source in the present invention refers to the continuously emitted industrial organic waste gas containing gaseous VOCs; the VOCs sink is similar to the energy sink in thermodynamics, responsible for receiving and dissipating or storing energy. The liquid VOCs sink in the present invention refers to the liquid organic solvent obtained by adsorbing - condensing and concentrating gaseous VOCs.

[0016] The organic carbon pump system of the present application heats the working temperature of the adsorption unit 2 to the pre - heating temperature through the heating unit 1 T预热 , enabling the adsorption unit 2 to efficiently adsorb low-concentration VOCs. This adsorption process under temperature control can ensure that the adsorption unit 2 operates under optimal conditions and improve the adsorption efficiency. At the desorption temperature T 脱附 , the adsorption unit 2 can desorb high-concentration VOCs. This adsorption and desorption process with dual temperature control enables the organic carbon pump system to flexibly switch under different concentration conditions and improve the overall treatment efficiency. The high-concentration VOCs after desorption are condensed into a liquid state by the condensation unit 3, which not only reduces the emissions of VOCs but also realizes the recycling of VOCs and reduces resource waste. At the same time, the low concentration in this application generally refers to the concentration of VOCs in general industrial organic waste gas, which is often less than 10,000 ppm or lower than the saturation concentration of VOCs at normal temperature; the high concentration generally refers to the high concentration after VOCs are concentrated and needs to be greater than the saturation concentration at the condensation temperature of VOCs.

[0017] To cope with VOCs with different concentrations and boiling points, the organic carbon pump system can adopt single-stage, two-stage, and multi-stage system forms.

[0018] As Figure 1 shown, this embodiment provides an organic carbon pump system for VOCs recovery, and the recovery of VOCs in industrial exhaust gas is realized by a single-stage organic carbon pump or a multi-stage organic carbon pump; The single-stage organic carbon pump includes at least an adsorption unit 2, a heating unit 1, and a condensation unit 3; The heating unit 1 is used to adjust the operating temperature of the adsorption unit 2 to the preheating temperature T 预热 or the desorption temperature T 脱附 ; The input end of the adsorption unit 2 serves as the input end of the single-stage organic carbon pump, which is used to receive the VOCs to be treated and adsorb the VOCs to be treated at the preheating temperature T 预热 and desorb at the desorption temperature T 脱附 ; the first output end of the adsorption unit 2 is used to output the transferred VOCs after high-concentration desorption; The input end of the condensation unit 3 is connected to the first output end of the adsorption unit 2 and is used to condense the transferred VOCs into a liquid state; the output end of the condensation unit 3 serves as the output end of the single-stage organic carbon pump and is used to output the liquid VOCs; Specifically, the single-stage organic carbon pump includes one "adsorption desorption The "condensation" cycle; the adsorption unit 2 in the organic carbon pump can adopt a fixed-bed adsorption unit 2 or a rotary adsorption unit 2, and the adsorbent in the adsorption unit 2 can be optionally equipped with activated carbon or molecular sieve. During the adsorption process, the concentration at the outlet of the adsorption unit 2 is lower than the emission limit specified by the national and local emission standards.

[0019] The multi-stage organic carbon pump is composed of multiple first-stage organic carbon pumps connected in series; for the multiple first-stage organic carbon pumps that are neither at the first nor at the last position in the multi-stage organic carbon pump, the first output end of the adsorption unit 2 of the previous first-stage organic carbon pump is connected to the input end of the next first-stage organic carbon pump.

[0020] Specifically, the multi-stage organic carbon pump includes multiple "adsorption desorption" cycles. The VOCs enter the next-stage carbon pump for circulation after being concentrated in each stage of the carbon pump to achieve step-by-step concentration, and complete the "adsorption desorption condensation" cycle in the last-stage organic carbon pump to complete the phase change recovery of the VOCs. This system form is suitable for the recovery of low-concentration and low-boiling-point VOCs. This multi-cycle method can gradually increase the concentration of the VOCs and finally achieve efficient recovery.

[0021] Compared with the prior art, the beneficial effects of an organic carbon pump system for VOCs recovery provided by the present invention are as follows: The industrial exhaust VOCs recovery of the present invention is realized by a first-stage organic carbon pump or a multi-stage organic carbon pump; the first-stage organic carbon pump includes at least an adsorption unit 2, a heating unit 1, and a condensation unit 3; the heating unit 1 is used to adjust the working temperature of the adsorption unit 2; the adsorption unit 2 is used to receive the VOCs to be treated, and its first output end is used to output the transferred VOCs after high-concentration desorption; the condensation unit 3 is used to condense the transferred VOCs into a liquid state; the multi-stage organic carbon pump is composed of multiple first-stage organic carbon pumps connected in series. This application can flexibly select the appropriate number of stages of the organic carbon pump according to the concentration and boiling point of the VOCs, improve the adaptability to the VOCs recovery, enable more accurate adsorption and desorption treatment of VOCs with different concentrations and boiling points in different stages of the organic carbon pump, and can more effectively gradually concentrate and recover the low-concentration VOCs, greatly improving the recovery effect.

[0022] In some embodiments of the present application, the heating unit 1 heats the adsorption unit 2 by direct heating or indirect heating; Direct heating uses heating gas to perform convective purge heating on the adsorption unit 2. The heating gas can include gases such as hot air, water vapor, or hot nitrogen, which are not limited here. During implementation, one of the heating gases is selected; Indirect heating adopts a heating coil or a heating jacket, and conducts heat conduction heating on the adsorption unit 2 through the heat medium flowing in the heating coil or the heating jacket.

[0023] Specifically, in direct heating, heating gases (such as hot air, steam, hot nitrogen) are used to conduct convective purge heating on the adsorption unit 2, which can quickly transfer heat to the surface and interior of the adsorbent, causing the adsorbed VOCs to desorb rapidly. This convective heating method has a high heat transfer efficiency and can quickly increase the temperature of the adsorption unit 2, shortening the desorption time.

[0024] In indirect heating, heating coils or heating jackets are used, and heat conduction heating is carried out on the adsorption unit 2 through the circulating flow of the heat medium. This heating method can evenly transfer heat to all parts of the adsorption unit 2, avoiding local overheating and ensuring the uniformity and stability of the desorption process.

[0025] In some embodiments of the present application, the organic carbon pump assists the adsorption unit 2 in desorption by means of vacuum desorption. Vacuum desorption uses purge desorption or non-purge desorption, and the preferred vacuum pressure range is 5 - 10 kPa, that is, the vacuum degree is 90 - 95 kPa.

[0026] Among them, the vacuum environment can significantly reduce the desorption temperature of VOCs, enabling the adsorption unit 2 to achieve efficient desorption at a lower temperature. Compared with the traditional thermal desorption method, the vacuum desorption method can enable the adsorption unit 2 to complete the desorption process in a shorter time, while reducing the thermal damage to the adsorbent in the adsorption unit 2. Purge desorption introduces an inert gas (such as nitrogen) to purge the surface of the adsorbent, which can quickly carry away the desorbed VOCs and prevent them from re-adsorbing, improving the desorption efficiency. Non-purge desorption relies on the suction effect of the vacuum environment itself to achieve desorption and is suitable for scenarios with low requirements for gas flow to further optimize the desorption process.

[0027] Optionally, the heat source of the organic carbon pump can use forms such as electric heating, gas heating, high-temperature heat pump, etc. to provide driving force for the desorption process, and industrial waste heat should be fully utilized.

[0028] Specifically, the present application can flexibly adjust the mixed use of thermal desorption and vacuum desorption according to different VOC characteristics and treatment requirements. For example, for low-boiling VOCs, vacuum desorption is selected as the main method and thermal desorption as the auxiliary method, and the desorption effect is better; while for high-boiling VOCs, thermal desorption is selected as the main method and vacuum desorption as the auxiliary method, which can provide the necessary heat to ensure the desorption efficiency.

[0029] In some embodiments of the present application, a primary organic carbon pump or a multi-stage organic carbon pump is selected according to the concentration and boiling point of VOCs in industrial exhaust air; if the concentration of VOCs in industrial exhaust air is greater than a first preset concentration or the boiling point of VOCs in industrial exhaust air is greater than a first preset boiling point, a primary organic carbon pump is selected; if the concentration of VOCs in industrial exhaust air is less than the first preset concentration or the boiling point of VOCs in industrial exhaust air is less than the first preset boiling point, a multi-stage organic carbon pump is selected. Among them, the first preset concentration and the boiling point of VOCs in industrial exhaust air are determined through a fixed-bed breakthrough adsorption pre-experiment, and the definitions of the first preset concentration and the boiling point of VOCs in industrial exhaust air are the VOCs concentration and boiling point that ensure that the fixed-bed adsorber just does not break through within a specified adsorption time.

[0030] Specifically, by selecting the system form of the organic carbon pump according to the concentration and boiling point of VOCs, it can flexibly adapt to different types of industrial exhaust air. For high-concentration or high-boiling-point VOCs, using a primary organic carbon pump can meet the requirements and avoid waste of resources; while for low-concentration and low-boiling-point VOCs, using a multi-stage organic carbon pump can achieve more efficient treatment.

[0031] In some embodiments of the present application, a method for constructing a cycle for VOCs recovery is also disclosed, which is realized through the above-mentioned organic carbon pump system for VOCs recovery.

[0032] The thermodynamic cycle of the organic carbon pump system of the present application can be expressed on P - q a graph and a Clapeyron diagram, P - q The graph represents the change in the partial pressure of VOCs and the adsorbent adsorption capacity in the carbon pump during the operation of the organic carbon pump. The adsorption capacity of the adsorbent at different partial pressures of VOCs and operating temperatures follows the Sips adsorption isotherm model, as follows: (1) (2) (3) Among them, P n is P the nth power of P the partial pressure of VOCs, is the equilibrium adsorption capacity, q m ( T ) is the temperature T at which the maximum adsorption capacity occurs, b ( T ) is the Sips model coefficient at temperature T q m0 m0 ​q m1 , b 0, b 1 and n are all fitting parameters, and their determination method is as follows: adopt the method of steam adsorption instrument + water / oil bath to test the adsorption isotherm within the adsorption and desorption temperature / pressure range, and then perform binary non-linear regression on the adsorption isotherm to obtain the above-mentioned fitting parameters.

[0033] The Claperon diagram represents the heat transfer situation during the operation of the organic carbon pump, that is, the heat grade and consumption of the system's cold / heat. The VOCs condensation process follows the Claperon equation of the phase change process, as shown below: (4) Where k , b are all fitting parameters, and their values are related to the types of VOCs and can be obtained by looking up the table according to the substance types. The organic carbon pump thermodynamic cycle uses a logarithmic coordinate system of -1 / T and ln P . The condensation behavior of VOCs in the organic carbon pump follows a linear relationship, and its adsorption behavior satisfies the Sips adsorption isotherm model. Through logarithmic linear transformation, convert formulas (1) to (3) to -1 / T vs. ln P .

[0034] (5) The node state parameters of the organic carbon pump during dynamic operation can be determined in the organic carbon pump thermodynamic cycle diagram according to the source conditions. The source conditions include the cold and heat source temperatures ( T 冷凝 , T 脱附 ), the organic carbon source ( P 吸附 , T 吸附 ). In addition, T 冷凝 and formula (4) can determine the VOCs pressure P 冷凝 during the condensation process of the organic carbon pump. First, according to P 吸附 and T 吸附 , point 2 can be determined on the adsorption isotherm. On the P - q diagram, draw a horizontal line from point 2 to intersect with P 冷凝 to determine point 3. Then continue to draw a vertical isobar from point 3, and the intersection point with the T desorption isotherm is point 4. In the Claperon diagram, draw a vertical line from point 4 to isothermally decrease to the adsorption amount ofq The position of 0, which is point 5, is at P - q On the graph, draw a horizontal line from point 5 to intersect with T 吸附 The intersection point of the adsorption isotherm is point 1, and the pressure corresponding to point 1 is P 排放 .

[0035] Taking the temperature-variable adsorption and condensation recovery process of a primary organic carbon pump as an example, the thermodynamic cycle process of this application is constructed. Refer to Figure 3 and Figure 4 , the cycle process is denoted as point 1 to point 2 to point 3 to point 4 to point 5 to point 1. Point 1 is the state after the desorption and cooling of the internal adsorption unit 2 of the carbon pump, which is the initial state of the adsorption process, and its adsorption capacity is q 0. According to the adsorption isotherm, its equilibrium pressure at the adsorption temperature T 吸附 is P 排放 ; Point 2 is the end state of the adsorption process, which is the saturated state at the adsorption pressure P 吸附 (which can be converted through the emission concentration), and its adsorption capacity is q 2. At this time, the adsorbent can no longer treat VOCs, and the carbon pump needs to be switched to the desorption and regeneration mode; Point 3 is the end state of the preheating process, and the temperature of the adsorbent reaches the preheating temperature T 预热 , and at this time, the adsorbent reaches the equilibrium adsorption state at the condensation pressure P 冷凝 (which can be converted through the condensation concentration); Point 4 is the end state of the desorption, and the temperature of the adsorbent reaches the desorption temperature T 脱附 , and at this time, the adsorbent reaches the P 冷凝 equilibrium adsorption state q 1; Point 5 is the end state of the transfer process, and the adsorption capacity at this point drops to q 0.

[0036] Among them, from point 1 to point 2 is the isothermal adsorption process, adopting a cascade adsorption mode to achieve near-static active adsorption of the adsorbent; from point 2 to point 3 is the equal (adsorption) amount preheating process. During this process, the state point of the adsorbent moves from the ( T 吸附 , P 吸附 ) equilibrium point to the ( T 预热 , P 冷凝 ) equilibrium point; from point 3 Point 4 is the isobaric desorption process, where the desorbed high-concentration VOCs are rapidly condensed and maintained at the saturated concentration point at the VOCs condensation temperature. P 冷凝 ; Point 4 Point 5 is an isothermal transfer process, in which the remaining VOCs are desorbed and transferred to a spare carbon pump or a secondary carbon pump is set up to receive the transferred VOCs; Point 5 Point 1 is the cooling process of equal (adsorption) amount. For combustible materials such as activated carbon and honeycomb carbon, the cooling process needs to be cooled to near room temperature. For non-combustible materials such as silica gel and molecular sieves, the cooling process only needs to ensure that the outlet concentration meets the standard when switching back to the adsorption mode.

[0037] According to the thermodynamic cycle method proposed in the present invention, in a multi-stage carbon pump system, low-concentration VOCs in industrial exhaust air are converted into high-concentration through an adsorption process, and then desorbed at a high concentration after absorbing the heat provided by the heating unit 1, and recovered into a liquid organic solvent through a phase change through the condensation unit 3, thereby completing the recycling of the organic solvent. It can be seen that the VOCs recovery method constructed by the thermodynamic cycle greatly improves the recovery efficiency of the carbon pump system.

[0038] Specifically, the adsorption unit of the carbon pump system of the present invention adopts an intermittent operation mode to achieve efficient capture and concentrated recovery of VOCs: in the adsorption stage, the VOCs-containing waste gas is introduced into the normal temperature adsorption bed, and the activated carbon material captures and concentrates the VOCs; after switching to the regeneration stage, the carbon pump starts the heating unit to increase the temperature for desorption, and the desorbed high-concentration VOCs are pumped to the condensation unit with the hot carrier gas to be recovered as a liquid organic solvent, and the remaining gas is discharged after cooling. If a two-bed alternating or multi-bed parallel design is adopted, one bed can be regenerated while the other bed is adsorbing, thereby achieving continuous and uninterrupted operation of waste gas treatment and VOCs recovery.

[0039] In some embodiments of the present application, a method for evaluating the energy efficiency of an organic carbon pump system is also disclosed, and the energy efficiency of the organic carbon pump system is evaluated based on the first law of thermodynamics and the second law of thermodynamics; The formula for the first law of thermodynamics is as follows: (6) In formula (6), E is the energy consumption for VOCs recovery per unit mass, in kJ / mol; Q H is the heating amount of the desorption process, in kJ; Q C is the cooling capacity of the chiller during the condensing process, in kJ; COP is the coefficient of performance of the chiller; W S The axial work consumed in the adsorption and desorption process; is the VOCs desorption amount; The formula of the second law of thermodynamics is as follows: (7) In formula (7), η is the exergy efficiency of the organic carbon pump system; is the total inflow exergy, which is calculated by formula (8): (8) is the total outflow exergy, which is calculated by formula (9): (9) In formulas (8) and (9), M is the mass of the air or VOCs phase, with the unit of kg; ex is the specific exergy of the air or VOCs relative to the reference state 0. The reference state 0 is generally selected as the air containing saturated VOCs at the exhaust air temperature, with the unit of kJ / kg, and is calculated by formula (10): (10) In formula (10), h is the enthalpy of the air or VOCs, with the unit of kJ / kg; h 0 is the enthalpy of the air or VOCs under the reference state 0, with the unit of kJ / kg; s is the entropy of the air or VOCs, with the unit of kJ / (kg·K); s 0 is the entropy of the air or VOCs under the reference state 0, with the unit of kJ / (kg·K); T 0 is the temperature of the reference state 0, which is equal to the exhaust air temperature, recorded in thermodynamic temperature, with the unit of K; c p is the specific heat capacity at constant pressure of the air or VOCs, with the unit of kJ / (kg·K); R is the gas constant of the air or VOCs, with the unit of kJ / (kg·K); P is the partial pressure of the air or VOCs, with the unit of Pa; P 0 is the partial pressure of the air or VOCs under the reference state 0, with the unit of Pa.

[0040] In the treatment scenarios with different industrial exhaust air concentrations, the difficulty of VOCs recovery varies. Based on the exergy efficiency of the organic carbon pump of the second law of thermodynamics, it can effectively handle the horizontal comparison of the system efficiency under different treatment conditions, providing a strict quantitative basis for the system cycle design and operation parameter setting.

[0041] It can be seen that based on the first law of thermodynamics and the second law of thermodynamics, the comprehensive evaluation system of the organic carbon pump proposed from the two aspects of energy consumption and energy quality can significantly improve the VOCs treatment efficiency, reduce the energy consumption and carbon emissions in the treatment process, and achieve low-carbon treatment and near-zero emission of VOCs in industrial exhaust air.

[0042] The following takes the treatment of organic waste gas in a panel spraying factory as an example to illustrate the process of constructing the thermodynamic cycle of the organic carbon pump system of the present invention and evaluating the recovery performance of the organic carbon pump system: The main component of the organic waste gas in the spraying factory is xylene. The air volume on the industrial exhaust gas collection side is 30,000 m 3 / h, the xylene concentration is 2,000 mg / m 3 , the exhaust air temperature is 35 °C, the internal material of the organic carbon pump is coal-based granular activated carbon, and the adsorption isotherm of xylene on this activated carbon conforms to the Sips model of formula (1). In this patent, the model parameters q m0 = 2.318, q m1 = 44.46, b 0 = 7.354×10-5, b 1 = 2,755, n = 0.5338. The operating states of each stage of the organic carbon pump are as follows: the partial pressure of VOCs at the adsorption starting point 1 is 0.19 Pa, the carbon pump temperature is 35 °C, and the adsorption capacity is 0.37 mol / kg; the partial pressure of VOCs at the adsorption end point 2 is 47.73 Pa, the carbon pump temperature is 35 °C, and the adsorption capacity is 2.33 mol / kg; the partial pressure of VOCs at the preheating end point 3 is 171.24 Pa, the carbon pump temperature is 107 °C, and the adsorption capacity is 2.33 mol / kg; the partial pressure of VOCs at the desorption end point 4 is 171.24 Pa, the carbon pump temperature is 200 °C, and the adsorption capacity is 1.12 mol / kg; the partial pressure of VOCs at the transfer end point 5 is 84.57 Pa, the carbon pump temperature is 35 °C, and the adsorption capacity is 0.37 mol / kg. After being treated by the organic carbon pump, the concentration of the organic waste gas is reduced from 2,000 mg / m 3 to 8.38 mg / m 3 , the theoretical recovery rate of the organic carbon pump is 99.58%, the recovery energy efficiency of the first law of thermodynamics is 3.8 kWh / kg, and the exergy efficiency of the second law of thermodynamics is 53.22%. Therefore, according to the actual scenario data, it can be calculated that the organic carbon pump system can theoretically achieve low-carbon recovery and near-zero emission of VOCs in industrial exhaust air.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications or equivalent substitutions can still be made to the specific embodiments of the present invention, and any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention shall be covered by the protection scope of the claims of the present invention.

Claims

1. An organic carbon pump system for VOCs recovery, characterized in that, The recovery of VOCs in industrial exhaust gas is achieved by a single-stage organic carbon pump or a multi-stage organic carbon pump; The single-stage organic carbon pump at least includes an adsorption unit, a heating unit, and a condensation unit; The heating unit is used to adjust the working temperature of the adsorption unit to the preheating temperature T 预热 or the desorption temperature T 脱附 ; The input end of the adsorption unit serves as the input end of the primary organic carbon pump, and is used to receive the VOCs to be processed, and adsorb the VOCs to be processed at the preheating temperature T 预热 and desorb at the desorption temperature T 脱附 ; the first output end of the adsorption unit is used to output the transferred VOCs after desorption; The input end of the condensation unit is connected to the first output end of the adsorption unit, and is used to condense the transferred VOCs into a liquid state; the output end of the condensation unit serves as the output end of the single-stage organic carbon pump, and is used to output liquid VOCs; The multi-stage organic carbon pump is composed of a plurality of the single-stage organic carbon pumps connected in series; for the plurality of single-stage organic carbon pumps that are neither the first nor the last in the multi-stage organic carbon pump, the first output end of the adsorption unit of the previous single-stage organic carbon pump is connected to the input end of the next single-stage organic carbon pump.

2. The organic carbon pump system for VOCs recovery according to claim 1, characterized in that, The heating unit heats the adsorption unit by direct heating or indirect heating; The direct heating uses a heating gas to perform convective purge heating on the adsorption unit, and the heating gas includes hot air, water vapor, or hot nitrogen; The indirect heating uses a heating coil or a heating jacket, and conducts heat conduction heating on the adsorption unit through the heat medium flowing in the heating coil or the heating jacket.

3. The organic carbon pump system for VOCs recovery according to claim 1, characterized in that, Select the single-stage organic carbon pump or the multi-stage organic carbon pump according to the concentration and boiling point of VOCs in industrial exhaust gas; If the concentration of VOCs in industrial exhaust gas is greater than a first preset concentration or the boiling point of VOCs in industrial exhaust gas is greater than a first preset boiling point, select the single-stage organic carbon pump; If the concentration of VOCs in industrial exhaust gas is less than a first preset concentration or the boiling point of VOCs in industrial exhaust gas is less than a first preset boiling point, select the multi-stage organic carbon pump.

4. A method for constructing a cycle for VOCs recovery, characterized in that, Implemented based on the organic carbon pump system according to any one of claims 1-3, the method for constructing the cycle includes: Record the cyclic process as point 1 to point 2 to point 3 to point 4 to point 5 to point 1, where point 1 is the state after the adsorption unit inside the organic carbon pump system is desorbed and cooled, which is the initial state of the adsorption process, and the adsorption capacity of the adsorption unit is q 0, and its equilibrium pressure at the adsorption temperature T 吸附 is P 排放 ; point 2 is the end state of the adsorption process, which is the saturated state at the adsorption pressure P 吸附 , and the adsorption capacity of the adsorption unit is q 2. At this time, switch the organic carbon pump system to the desorption and regeneration mode; point 3 is the end state of the preheating process, and the temperature of the adsorption unit reaches the preheating temperature T 预热 , and at this time the adsorption unit reaches the equilibrium adsorption state at the condensation pressure P 冷凝 ; point 4 is the end state of desorption, and the temperature of the adsorption unit reaches the desorption temperature T 脱附 , and at this time the adsorption unit reaches the P 冷凝 equilibrium adsorption state q 1; point 5 is the end state of the transfer process, and the adsorption capacity of the adsorption unit drops to q 0.

5. The cycle construction method according to claim 4, characterized in that, The adsorption process of VOCs in the organic carbon pump system satisfies the Sips adsorption isotherm model; the formula of the Sips adsorption isotherm model is as follows: (1) (2) (3) In formulas (1) to (3), P n is P to the nth power, P is the partial pressure of VOCs; is the equilibrium adsorption capacity; q m ( T ) is the temperature T at which the maximum adsorption capacity occurs, b ( T ) is the Sips model coefficient at the temperature T ; q m0 , q m1 , b 0, b 1, and n are all fitting parameters; The condensation process of VOCs in the organic carbon pump system satisfies the Claperon equation; the Claperon equation is as follows: (4) In formula (4), k , b are all fitting parameters, and their values are related to the types of VOCs; Convert formulas (1) to (3) into a logarithmic relationship form of -1 / T and ln P to obtain: (5)。 6. A method for evaluating the energy efficiency of an organic carbon pump system, characterized in that, Evaluate the energy efficiency of the organic carbon pump system according to any one of claims 1-3 based on the first law of thermodynamics and the second law of thermodynamics; The formula of the first law of thermodynamics is as follows: (6) In Equation (6), E is the energy consumption for VOCs recovery per unit amount of substance, with the unit of kJ / mol; Q H is the heating quantity during the desorption process, with the unit of kJ; Q C is the refrigerating capacity of the chiller during the condensation process, with the unit of kJ; COP is the performance coefficient of the chiller; W S is the shaft work consumed during the adsorption and desorption processes; is the VOCs desorption amount; The formula of the second law of thermodynamics is as follows: (7) In Equation (7), η is the exergy efficiency of the organic carbon pump system; is the total inflow exergy, which is calculated by Equation (8): (8) is the total out-flow exergy, which is calculated by Equation (9): (9) In formulas (8) and (9), M is the mass of air or VOCs, with the unit of kg; ex is the specific exergy of air or VOCs relative to the reference state 0, where the reference state 0 is air containing saturated VOCs at the exhaust air temperature, with the unit of kJ / kg and is calculated by formula (10): (10) In Equation (10), h is the enthalpy of air or VOCs, with the unit of kJ / kg; h 0 is the enthalpy of air or VOCs under the reference state 0, with the unit of kJ / kg; s is the entropy of air or VOCs, with the unit of kJ / (kg·K); s 0 is the entropy of air or VOCs under the reference state 0, with the unit of kJ / (kg·K); T 0 is the temperature of the reference state 0, which is equal to the exhaust air temperature, recorded in thermodynamic temperature, with the unit of K; c p is the specific heat capacity at constant pressure of air or VOCs, with the unit of kJ / (kg·K); R is the gas constant of air or VOCs, with the unit of kJ / (kg·K); P is the partial pressure of air or VOCs, with the unit of Pa; P 0 is the partial pressure of air or VOCs under the reference state 0, with the unit of Pa.

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