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

Abstract

The present invention relates to the technical field of industrial exhaust VOCs recovery, and specifically to an organic carbon pump system for VOCs recovery, a circulation construction method and an evaluation method thereof. Industrial exhaust VOCs recovery is achieved by a single-stage organic carbon pump or a multi-stage organic carbon pump; the single-stage organic carbon pump includes an adsorption unit, a heating unit and a condensation unit; the multi-stage organic carbon pump is composed of multiple single-stage organic carbon pumps in series; by thermodynamic means, P ‑ q The VOCs adsorption-condensation recovery thermodynamic cycle is constructed in the Figure 1 and the Claperon diagram, and the energy efficiency of the organic carbon pump system is evaluated based on the first and second laws of thermodynamics. This application can flexibly select the appropriate organic carbon pump stage according to the concentration and boiling point of VOCs, improve the adaptability of VOCs recovery, and achieve more precise adsorption and desorption treatment of industrial exhaust VOCs. It can more effectively concentrate and recover low-concentration VOCs step by step, thereby improving the recovery effect.

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] With the acceleration of modern industrialization, the use of organic solvents in a wide range of industries, including coatings, inks, pharmaceuticals, and lithium batteries, has led to significant emissions of volatile organic compounds (VOCs). As high-value pollutants in industrial production, the recycling of VOCs offers significant economic and environmental benefits.

[0003] At present, the 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 model of "waste" not only wastes organic solvent resources but also exacerbates the problem of carbon emissions. Therefore, in order to improve the treatment and recovery performance of VOCs, 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 only improves the performance of various hardware in the VOCs treatment system and still lacks basic innovation at the thermodynamic level. There are problems such as low circulation efficiency and poor recovery effect.

[0004] At the same time, in the existing technology 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 for VOCs recovery, so as to solve the problems of the lack of basic innovation at the thermodynamic level in the existing technology, low circulation efficiency and poor recovery effect.

[0006] The present invention provides an organic carbon pump system for VOCs recovery, wherein the recovery of VOCs in industrial exhaust air is achieved by a single-stage organic carbon pump or a multi-stage organic carbon pump;

[0007] The primary organic carbon pump comprises at least an adsorption unit, a heating unit and a condensation unit;

[0008] The heating unit is used to adjust the working temperature of the adsorption unit to the preheating temperatureT 预热 or desorption temperature T 脱附 ;

[0009] 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 to adsorb the VOCs to be processed at the preheating temperature. T 预热 adsorption and desorption at the T 脱附 Desorption is performed under the condition that the first output end of the adsorption unit is used to output the transferred VOCs after desorption;

[0010] 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 liquid; the output end of the condensation unit serves as the output end of the primary organic carbon pump, and is used to output liquid VOCs;

[0011] 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 not in the first or last position in the multi-stage organic carbon pump, the first output end of the adsorption unit of the previous first-stage organic carbon pump is connected to the input end of the next first-stage organic carbon pump.

[0012] 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;

[0013] The direct heating utilizes a heating gas to perform convection purge heating on the adsorption unit, wherein the heating gas includes hot air, water vapor or hot nitrogen;

[0014] The indirect heating adopts a heating coil or a heating jacket, and the adsorption unit is heated by heat conduction through the heat medium flowing in the heating coil or the heating jacket.

[0015] According to the 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 air;

[0016] If the concentration of VOCs in the industrial exhaust air is greater than the first preset concentration or the boiling point of VOCs in the industrial exhaust air is greater than the first preset boiling point, the first-level organic carbon pump is selected;

[0017] If the concentration of VOCs in the industrial exhaust air is less than the first preset concentration or the boiling point of VOCs in the industrial exhaust air is less than the first preset boiling point, the multi-stage organic carbon pump is selected.

[0018] The present invention also provides a cycle construction method for VOCs recovery, which is implemented based on the above-mentioned organic carbon pump system. The cycle construction method includes:

[0019] The cycle process is recorded as point 1 to point 2 to point 3 to point 4 to point 5 to point 1, wherein point 1 is the state of the adsorption unit inside the organic carbon pump system after desorption and cooling. This point is the initial state of the adsorption process, and the adsorption capacity of the adsorption unit is q 0, which is at the adsorption temperature T 吸附 The equilibrium pressure under P 排放 ; Point 2 is the end state of the adsorption process, which is the adsorption pressure P 吸附 Under the saturated state, the adsorption capacity of the adsorption unit is q 2. At this time, the organic carbon pump system is turned to the desorption regeneration mode; the point 3 is the end state of the preheating process, and the adsorption unit temperature reaches the preheating temperature T 预热 , at which point the adsorption unit reaches the condensation pressure P 冷凝 The equilibrium adsorption state under the point 4 is the desorption end state, the adsorption unit temperature reaches the desorption temperature T 脱附 , at this time the adsorption unit has reached 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.

[0020] 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:

[0021] (1)

[0022] (2)

[0023] (3)

[0024] In formulas (1) to (3), P n for P The nth power, P The partial pressure of VOCs; is the equilibrium adsorption amount; q m ( T) is the temperature T The maximum adsorption capacity under b ( T ) is the temperature T The Sips model coefficients under q m0 , q m1 , b 0, b 1 and n are all fitting parameters;

[0025] The condensation process of VOCs in the organic carbon pump system satisfies the Claperon equation; the Claperon equation is as follows:

[0026] (4)

[0027] In formula (4), k , b These are all fitting parameters, and their values are related to the types of VOCs;

[0028] Convert formulas (1) to (3) into -1 / T ln P The logarithmic relationship form of , we get:

[0029] (5).

[0030] The present invention also provides a method for evaluating the energy efficiency of an organic carbon pump system, which evaluates the energy efficiency of the organic carbon pump system based on the first law of thermodynamics and the second law of thermodynamics;

[0031] The formula for the first law of thermodynamics is as follows:

[0032] (6)

[0033] In formula (6), E is the energy consumption for VOCs recovery per unit mass, in kJ / mol; Q H is the heat amount during 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 processes; is the VOCs desorption amount;

[0034] The formula for the second law of thermodynamics is as follows:

[0035] (7)

[0036] 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):

[0037] (8)

[0038] is the total outflow exergy, which is calculated by formula (9):

[0039] (9)

[0040] In formula (8) and formula (9), M is the mass of air or VOCs, in kg; ex is the specific exergy of air or VOCs relative to the reference state 0, where the reference state 0 is air saturated with VOCs at the exhaust temperature, in kJ / kg, and is calculated using formula (10):

[0041] (10)

[0042] In formula (10), h is the enthalpy of air or VOCs, in kJ / kg; h 0 is the enthalpy of air or VOCs at reference state 0, in kJ / kg; s is the entropy of air or VOCs, in kJ / (kg·K); s 0 is the entropy of air or VOCs at reference state 0, in kJ / (kg·K); T 0 is the temperature of reference state 0, which is equal to the exhaust temperature and is recorded in thermodynamic temperature in K; c p is the constant pressure specific heat capacity of air or VOCs, in kJ / (kg·K); R is the gas constant of air or VOCs, in kJ / (kg·K); P is the partial pressure of air or VOCs, in Pa; P 0 is the partial pressure of air or VOCs in reference state 0, in Pa.

[0043] Compared with the prior art, the organic carbon pump system for VOCs recovery provided by the present invention has the following advantages:

[0044] The recovery of VOCs in industrial exhaust air of the present invention is achieved 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, 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 VOCs to be processed, 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. The present application can flexibly select the appropriate number of organic carbon pump stages according to the concentration and boiling point of the VOCs, improve the adaptability to VOCs recovery, and enable VOCs of different concentrations and boiling points to be more accurately adsorbed and desorbed in organic carbon pumps of different levels, and can more effectively gradually concentrate and recover low-concentration VOCs, greatly improving the recovery effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 Schematic diagram of the structure of an organic carbon pump system for VOCs recovery in an embodiment of the present invention;

[0046] Figure 2 This is a schematic diagram of the reverse gradient transfer principle of the organic carbon pump system for VOCs recovery in an embodiment of the present invention;

[0047] Figure 3 It is the thermodynamic cycle of the organic carbon pump system for VOCs recovery in the embodiment of the present invention. P - q (Pressure-adsorption capacity) schematic diagram;

[0048] Figure 4 Schematic diagram of the Claperon (temperature-pressure) thermodynamic cycle of the organic carbon pump system for VOCs recovery in an embodiment of the present invention. DETAILED DESCRIPTION

[0049] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying 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 to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art. It should be noted that, unless there is a conflict, the embodiments of the present disclosure and the features in the embodiments can be combined with each other. The present disclosure will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0050] See also Figure 1 、 Figure 2 The low-concentration VOCs source of the organic carbon pump system of this application is the VOCs carried in industrial exhaust, and its concentration is C LThe energy input of the organic carbon pump includes the mechanical shaft power of the pressure source such as the fan and vacuum pump. W , as well as heat from heating and cooling equipment and other cold and hot sources Q The high concentration of VOCs in the organic carbon pump is converted into liquid organic solvent for phase change recovery, and its concentration is C H Therefore, the industrial waste gas entering the organic carbon pump is recycled through the enrichment phase change treatment of the organic carbon pump, leaving a very small amount of VOCs, the concentration of which is far lower than the emission limit specified by national and local emission standards, achieving the goal of near-zero emissions. Figure 2 Medium G 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, which continuously provides 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, which is responsible for receiving and dissipating or storing energy. The liquid VOCs sink in the present invention refers to the liquid organic solvent obtained after the gaseous VOCs are concentrated by adsorption-condensation.

[0051] The organic carbon pump system of the present application heats the working temperature of the adsorption unit 2 to the preheating temperature through the heating unit 1 T 预热 , so that the adsorption unit 2 can efficiently adsorb low concentrations of VOCs. This temperature-controlled adsorption process can ensure that the adsorption unit 2 works under optimal conditions and improve the adsorption efficiency. T 脱附 Under this condition, the adsorption unit 2 can desorb high-concentration VOCs. This dual-temperature-controlled adsorption and desorption process enables the organic carbon pump system to flexibly switch under different concentration conditions, thereby improving the overall processing efficiency. The high-concentration VOCs after desorption are condensed into liquid through the condensation unit 3, which not only reduces the emission 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 room temperature; high concentration generally refers to the high concentration of VOCs after concentration, which must be greater than the saturation concentration of VOCs at the condensation temperature.

[0052] In order to cope with VOCs of different concentrations and boiling points, the organic carbon pump system can adopt single-stage, double-stage and multi-stage system forms.

[0053] like Figure 1 As shown, this embodiment provides an organic carbon pump system for VOCs recovery, and the recovery of VOCs in industrial exhaust air is achieved by a single-stage organic carbon pump or a multi-stage organic carbon pump;

[0054] The first-stage organic carbon pump comprises at least an adsorption unit 2, a heating unit 1 and a condensation unit 3;

[0055] The heating unit 1 is used to adjust the working temperature of the adsorption unit 2 to the preheating temperature T 预热 or desorption temperature T 脱附 ;

[0056] The input end of the adsorption unit 2 is used as the input end of the first-stage organic carbon pump to receive the VOCs to be treated and to treat the VOCs at the preheating temperature. T 预热 Adsorption and desorption at T 脱附 Desorption is performed under the condition of: the first output end of the adsorption unit 2 is used to output the transferred VOCs after high concentration desorption;

[0057] 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 liquid; the output end of the condensation unit 3 serves as the output end of the first-stage organic carbon pump, and is used to output liquid VOCs;

[0058] Specifically, the primary organic carbon pump includes an "adsorption Desorption "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 matched 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.

[0059] 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 not in the first or 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.

[0060] Specifically, the multi-stage organic carbon pump includes multiple "adsorption After the VOCs are concentrated in each carbon pump, they enter the next carbon pump cycle to achieve step-by-step concentration, and the "adsorption" is completed in the last organic carbon pump. Desorption The system is suitable for the recovery of low-concentration and low-boiling-point VOCs. This multiple-cycle method can gradually increase the concentration of VOCs and ultimately achieve efficient recovery.

[0061] Compared with the prior art, the organic carbon pump system for VOCs recovery provided by the present invention has the following advantages:

[0062] The industrial exhaust VOCs recovery of the present invention is achieved by a single-stage organic carbon pump or a multi-stage organic carbon pump; the single-stage organic carbon pump comprises 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 VOCs to be processed, 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 a plurality of single-stage organic carbon pumps connected in series. The present application can flexibly select the appropriate number of organic carbon pump stages according to the concentration and boiling point of the VOCs, improve the adaptability to VOCs recovery, and enable VOCs of different concentrations and boiling points to be more accurately adsorbed and desorbed in organic carbon pumps of different levels, and can more effectively gradually concentrate and recover low-concentration VOCs, greatly improving the recovery effect.

[0063] In some embodiments of the present application, the heating unit 1 heats the adsorption unit 2 using direct heating or indirect heating;

[0064] Direct heating utilizes a heating gas to perform convection purge heating on the adsorption unit 2. The heating gas may include hot air, water vapor, hot nitrogen, etc., which are not limited here. When implemented, one of the heating gases is selected;

[0065] Indirect heating uses a heating coil or a heating jacket, and the adsorption unit 2 is heated by heat conduction through the heat medium flowing in the heating coil or the heating jacket.

[0066] Specifically, direct heating utilizes a heating gas (such as hot air, water vapor, or hot nitrogen) to perform convection purging and heating on the adsorption unit 2, which can quickly transfer heat to the surface and interior of the adsorbent, allowing the adsorbed VOCs to be rapidly desorbed. This convection heating method has high heat transfer efficiency, can quickly increase the temperature of the adsorption unit 2, and shorten the desorption time.

[0067] Indirect heating uses a heating coil or heating jacket to conduct heat to the adsorption unit 2 through the circulation of a 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.

[0068] In some embodiments of the present application, the organic carbon pump assists the adsorption unit 2 in desorption by vacuum desorption. The vacuum desorption adopts purge desorption or non-purge desorption. The preferred vacuum pressure range is 5-10 kPa, that is, the vacuum degree is 90-95 kPa.

[0069] Among them, the vacuum environment can significantly reduce the desorption temperature of VOCs, allowing the adsorption unit 2 to achieve efficient desorption at a lower temperature. Compared with traditional thermal desorption methods, vacuum desorption can enable the adsorption unit 2 to complete the desorption process in a shorter time, while reducing thermal damage to the adsorbent in the adsorption unit 2. Purge desorption introduces an inert gas (such as nitrogen) to purge the adsorbent surface, which can quickly remove the desorbed VOCs, prevent them from being re-adsorbed, and improve desorption efficiency. Non-purge desorption relies on the suction effect of the vacuum environment itself to achieve desorption. It is suitable for scenarios where gas flow requirements are not high, so as to further optimize the desorption process.

[0070] Optionally, the heat source of the organic carbon pump can be in the form of 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.

[0071] Specifically, the present application can flexibly adjust the mixed use of thermal desorption and vacuum desorption according to different VOCs characteristics and treatment requirements. For example, for low-boiling point VOCs, vacuum desorption is selected as the main method and thermal desorption is used as the auxiliary method, which has a better desorption effect; while for high-boiling point VOCs, thermal desorption is selected as the main method and vacuum desorption is used as the auxiliary method, which can provide the necessary heat to ensure the desorption efficiency.

[0072] In some embodiments of the present application, a single-stage organic carbon pump or a multi-stage organic carbon pump is selected based on the concentration and boiling point of VOCs in the industrial exhaust air; if the concentration of VOCs in the industrial exhaust air is greater than a first preset concentration or the boiling point of VOCs in the industrial exhaust air is greater than the first preset boiling point, a single-stage organic carbon pump is selected; if the concentration of VOCs in the industrial exhaust air is less than the first preset concentration or the boiling point of VOCs in the industrial exhaust air is less than the first preset boiling point, a multi-stage organic carbon pump is selected. The first preset concentration and the boiling point of VOCs in the industrial exhaust air are determined through a fixed-bed penetration adsorption pre-experiment, and the first preset concentration and the boiling point of VOCs in the industrial exhaust air are defined as the VOC concentration and boiling point that ensure that the fixed-bed adsorber does not penetrate within the specified adsorption time.

[0073] 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. For high-concentration or high-boiling-point VOCs, a single-stage organic carbon pump can meet the needs and avoid waste of resources; for low-concentration and low-boiling-point VOCs, a multi-stage organic carbon pump can achieve more efficient treatment.

[0074] In some embodiments of the present application, a cycle construction method for VOCs recovery is also disclosed, which is implemented by the above-mentioned organic carbon pump system for VOCs recovery.

[0075] The thermodynamic cycle of the organic carbon pump system of this application can be expressed as P -q Figure and Claperon diagram, P - q The figure represents the changes in the partial pressure of VOCs in the carbon pump and the adsorption amount of the adsorbent during the operation of the organic carbon pump. The adsorption amount of the adsorbent at different VOCs partial pressures and operating temperatures complies with the Sips adsorption isotherm model, as shown below:

[0076] (1)

[0077] (2)

[0078] (3)

[0079] in, P n for P The nth power, P is the partial pressure of VOCs, is the equilibrium adsorption capacity, q m ( T ) is the temperature T The maximum adsorption capacity under b ( T ) is the temperature T The Sips model coefficients under q m0 , q m1 , b 0, b 1 and n All of them are fitting parameters, which are determined by using a vapor adsorption instrument + water / oil bath to test the adsorption isotherms within the adsorption and desorption temperature / pressure range, and then performing binary nonlinear regression on the adsorption isotherms to obtain the above fitting parameters.

[0080] The Claperon diagram represents the heat transfer during the operation of the organic carbon pump, that is, the system's cooling / heating quality and usage. The VOCs condensation process follows the Claperon equation for the phase change process, as shown below:

[0081] (4)

[0082] in k , b All of them are fitting parameters. Their values are related to the types of VOCs and can be obtained by looking up the table according to the type of substance. The organic carbon pump thermodynamic cycle uses -1 / T with ln PIn the logarithmic coordinate system, the condensation behavior of VOCs in the organic carbon pump follows a linear relationship, and its adsorption behavior satisfies the Sips adsorption isotherm model. By log-linear transformation, formulas (1) to (3) are converted into -1 / T vs. ln P .

[0083] (5)

[0084] The state parameters of the nodes in the dynamic operation process of the organic carbon pump can be determined in the organic carbon pump thermodynamic cycle diagram according to the source conditions. The source conditions include the temperature of the cold and hot sources ( T 冷凝 , T 脱附 )、Organic carbon source( P 吸附 , T 吸附 ),in addition, T 冷凝 The VOCs pressure in the organic carbon pump condensation process can be determined by formula (4): P 冷凝 First, according to P 吸附 and T 吸附 Point 2 can be determined on the adsorption isotherm. P - q In the figure, draw a horizontal line from point 2 to P 冷凝 The intersection of the vertical isobaric line and the T desorption isotherm is determined at point 3. The intersection of the vertical isobaric line and the T desorption isotherm is determined at point 4. In the Claperon diagram, a vertical line isothermally descends from point 4 to the adsorption amount of q 0, which is point 5, P - q In the figure, draw a horizontal line from point 5 and T 吸附 The intersection of the adsorption isotherms is point 1, which corresponds to the pressure P 排放 .

[0085] This application constructs a thermodynamic cycle process using the temperature swing adsorption and condensation recovery process of a primary organic carbon pump as an example. Figure 3 and Figure 4 The cycle process is recorded as point 1 to point 2 to point 3 to point 4 to point 5 to point 1. Point 1 is the state after desorption and cooling of the adsorption unit 2 inside the carbon pump. This point is the initial state of the adsorption process, and its adsorption capacity is q 0, according to the adsorption isotherm, at the adsorption temperature T 吸附 The equilibrium pressure under P 排放; Point 2 is the end state of the adsorption process, and this point is the adsorption pressure P 吸附 (can be converted by emission concentration) under saturated state, the adsorption capacity is q 2. At this time, the adsorbent cannot continue to process VOCs, and the carbon pump needs to be switched to desorption regeneration mode; Point 3 is the end of the preheating process, and the adsorbent temperature reaches the preheating temperature. T 预热 , at which point the adsorbent reaches the condensation pressure P 冷凝 (can be converted to condensation concentration) under equilibrium adsorption state; point 4 is the end of desorption state, the adsorbent temperature reaches the desorption temperature T 脱附 , at which point the adsorbent reaches P 冷凝 Equilibrium adsorption state q 1; point 5 is the end state of the transfer process, where the adsorption amount drops to q 0.

[0086] Among them, point 1 Point 2 is the isothermal adsorption process, which adopts the cascade adsorption mode to achieve the adsorption of the adsorbent near static activity; Point 2 Point 3 is the equal (adsorption) amount preheating process, in which the adsorbent state point changes from ( T 吸附 , P 吸附 ) equilibrium point to ( T 预热 , P 冷凝 ) The equilibrium point moves; 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 the 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 take over 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 sieve, the cooling process only needs to ensure that the outlet concentration meets the standard when switching back to the adsorption mode.

[0087] The thermodynamic cycle method proposed in the present invention converts low-concentration VOCs in industrial exhaust air into high concentrations through an adsorption process in a multi-stage carbon pump system. The low-concentration VOCs are then desorbed at a high concentration after absorbing the heat provided by the heating unit 1, and are recovered as liquid organic solvents 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.

[0088] 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: During the adsorption phase, VOC-containing waste gas is introduced into the room-temperature adsorption bed, where the activated carbon material captures and concentrates the VOCs. After switching to the regeneration phase, the carbon pump activates the heating unit to increase the temperature for desorption. The desorbed high-concentration VOCs are pumped along with the hot carrier gas to the condensation unit for recovery as a liquid organic solvent, and the remaining gas is cooled and discharged. If a two-bed alternating or multi-bed parallel design is adopted, one bed can be regenerated while another is adsorbing, thereby achieving continuous and uninterrupted operation of waste gas treatment and VOC recovery.

[0089] In some embodiments of the present application, a method for evaluating the energy efficiency of an organic carbon pump system is also disclosed, wherein the energy efficiency of the organic carbon pump system is evaluated based on the first law of thermodynamics and the second law of thermodynamics;

[0090] The formula for the first law of thermodynamics is as follows:

[0091] (6)

[0092] In formula (6), E is the energy consumption for VOCs recovery per unit mass, in kJ / mol; Q H is the heat amount during 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 processes; is the VOCs desorption amount;

[0093] The formula for the second law of thermodynamics is as follows:

[0094] (7)

[0095] 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):

[0096] (8)

[0097] is the total outflow exergy, which is calculated by formula (9):

[0098] (9)

[0099] In formula (8) and formula (9), M is the mass of air or VOCs phase, in kg; ex is the specific exergy of air or VOCs relative to the reference state 0. The reference state 0 is generally selected as air saturated with VOCs at the exhaust temperature. The unit is kJ / kg and is calculated by formula (10):

[0100] (10)

[0101] In formula (10), h is the enthalpy of air or VOCs, in kJ / kg; h 0 is the enthalpy of air or VOCs at reference state 0, in kJ / kg; s is the entropy of air or VOCs, in kJ / (kg·K); s 0 is the entropy of air or VOCs at reference state 0, in kJ / (kg·K); T 0 is the temperature of reference state 0, which is equal to the exhaust temperature and is recorded in thermodynamic temperature in K; c p is the constant pressure specific heat capacity of air or VOCs, in kJ / (kg·K); R is the gas constant of air or VOCs, in kJ / (kg·K); P is the partial pressure of air or VOCs, in Pa; P 0 is the partial pressure of air or VOCs in reference state 0, in Pa.

[0102] The difficulty of VOCs recovery varies in treatment scenarios with different industrial exhaust concentrations. The organic carbon pump exergy efficiency based on the second law of thermodynamics can effectively cope with the horizontal comparison of system efficiency under different treatment conditions, and provide a strict quantitative basis for system cycle design and operation parameter setting.

[0103] It can be seen that the comprehensive evaluation system of organic carbon pumps proposed in this application based on the first law of thermodynamics and the second law of thermodynamics from the two aspects of energy consumption and energy quality can significantly improve the VOCs treatment efficiency, reduce the energy consumption and carbon emissions of the treatment process, and achieve low-carbon treatment and near-zero emissions of VOCs in industrial exhaust.

[0104] The following takes the treatment of organic waste gas from a panel spraying plant as an example to illustrate the process of constructing the thermal 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 from the spraying plant is xylene, and the industrial exhaust collection side air volume is 30,000m 3 / h, xylene concentration 2000mg / m 3 , the exhaust temperature is 35℃, the internal material of the organic carbon pump is coal-based granular activated carbon, and the adsorption isotherm of xylene on the 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=2755, n =0.5338. The operating status of the organic carbon pump at each stage is: the VOCs partial pressure at the adsorption starting point 1 is 0.19Pa, the carbon pump temperature is 35℃, and the adsorption amount is 0.37mol / kg; the VOCs partial pressure at the adsorption end point 2 is 47.73Pa, the carbon pump temperature is 35℃, and the adsorption amount is 2.33mol / kg; the VOCs partial pressure at the preheating end point 3 is 171.24Pa, the carbon pump temperature is 107℃, and the adsorption amount is 2.33mol / kg; the VOCs partial pressure at the desorption end point 4 is 171.24Pa, the carbon pump temperature is 200℃, and the adsorption amount is 1.12mol / kg; the VOCs partial pressure at the transfer end point 5 is 84.57Pa, the carbon pump temperature is 35℃, and the adsorption amount is 0.37mol / kg. After treatment by the organic carbon pump, the concentration of organic waste gas is reduced from 2000mg / m 3 Reduced to 8.38 mg / m 3 The organic carbon pump has a theoretical recovery rate of 99.58%, a first-law of thermodynamics recovery efficiency of 3.8 kWh / kg, and a second-law of thermodynamics exergy efficiency of 53.22%. Therefore, based on actual scenario data, it can be calculated that the organic carbon pump system can theoretically achieve low-carbon recovery and near-zero emissions of VOCs in industrial exhaust air.

[0105] 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 it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of protection of the claims of the present invention.

Claims

1. A circular construction method for VOCs recovery, characterized in that: It is realized by using an organic carbon pump system for VOCs recovery. The recovery of VOCs in industrial exhaust air is realized by a single-stage organic carbon pump or a multi-stage organic carbon pump; The primary organic carbon pump comprises at least 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 adsorption temperature T 吸附 or preheat temperature T 预热 ; 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 to adsorb the VOCs to be treated at the adsorption temperature. T 吸附 Adsorption begins at the preheating temperature T 预热 Desorption begins; 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 liquid; the output end of the condensation unit serves as the output end of the primary organic carbon pump, and is used to output liquid VOCs; The multi-stage organic carbon pump is composed of a plurality of the first-stage organic carbon pumps connected in series; for the plurality of the first-stage organic carbon pumps that are not in the first or last position in the multi-stage organic carbon pump, the first output end of the adsorption unit of the first-stage organic carbon pump is connected to the input end of the next-stage organic carbon pump; The cycle construction method includes: recording the cycle process as point 1 to point 2 to point 3 to point 4 to point 5 to point 1, wherein point 1 is the state of the adsorption unit inside the organic carbon pump system after desorption and cooling, and this point is the initial state of the adsorption process. The adsorption amount of the adsorption unit is q 0, which is at the adsorption temperature T 吸附 The equilibrium pressure under P 排放 ; Point 2 is the end state of the adsorption process, which is close to the adsorption pressure P 吸附 Under the saturated state, the adsorption capacity of the adsorption unit is q 2. At this time, the organic carbon pump system is turned to the desorption regeneration mode; the point 3 is the end state of the preheating process, and the adsorption unit temperature reaches the preheating temperature T 预热 , at which point the adsorption unit reaches the condensation pressure P 冷凝 The equilibrium adsorption state under the point 4 is the desorption end state, the adsorption unit temperature reaches the desorption temperature T 脱附 , at this time the adsorption unit has reached 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; The adsorption process of the VOCs to be treated 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 for P The nth power, P The partial pressure of VOCs; q * is the equilibrium adsorption capacity; q m ( T ) is the temperature T The maximum adsorption capacity under b ( T ) is the temperature T The Sips model coefficients under q m0 , q m1 , b 0, b 1 and n are all fitting parameters; The condensation process of the transferred VOCs in the organic carbon pump system satisfies the Claperon equation; the Claperon equation is as follows: (4) In formula (4), k , b These are all fitting parameters, and their values are related to the types of VOCs; Convert formulas (1) to (3) into -1 / T with ln P The logarithmic relationship form of , we get: (5)。 2. A circular construction method 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 utilizes a heating gas to perform convection purge heating on the adsorption unit, wherein the heating gas includes hot air, water vapor or hot nitrogen; The indirect heating adopts a heating coil or a heating jacket, and the adsorption unit is heated by heat conduction through the heat medium flowing in the heating coil or the heating jacket.

3. A circular construction method for VOCs recovery according to claim 1, characterized in that: Selecting the primary organic carbon pump or the multi-stage organic carbon pump according to the concentration and boiling point of VOCs in the industrial exhaust air; If the concentration of VOCs in the industrial exhaust air is greater than the first preset concentration or the boiling point of VOCs in the industrial exhaust air is greater than the first preset boiling point, the first-level organic carbon pump is selected; If the concentration of VOCs in the industrial exhaust air is less than the first preset concentration or the boiling point of VOCs in the industrial exhaust air is less than the first preset boiling point, the multi-stage organic carbon pump is selected.

4. A method for evaluating the energy efficiency of an organic carbon pump system, characterized in that: Evaluating the energy efficiency of the organic carbon pump system according to any one of claims 1 to 3 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 heat amount during 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 processes; is the VOCs desorption amount; The formula for 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 formula (8) and formula (9), M is the mass of air or VOCs, in kg; ex is the specific exergy of air or VOCs relative to the reference state 0, where the reference state 0 is air saturated with VOCs at the exhaust temperature, in kJ / kg, and is calculated using formula (10): (10) In formula (10), h is the enthalpy of air or VOCs, in kJ / kg; h 0 is the enthalpy of air or VOCs at reference state 0, in kJ / kg; s is the entropy of air or VOCs, in kJ / (kg·K); s 0 is the entropy of air or VOCs at reference state 0, in kJ / (kg·K); T 0 is the temperature of reference state 0, which is equal to the exhaust temperature and is recorded in thermodynamic temperature in K; c p is the constant pressure specific heat capacity of air or VOCs, in kJ / (kg·K); R is the gas constant of air or VOCs, in kJ / (kg·K); P is the partial pressure of air or VOCs, in Pa; P 0 is the partial pressure of air or VOCs in reference state 0, in Pa.

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