Low-concentration VOC treatment method and system based on multistage adsorption technology

Abstract

The invention relates to the technical field of low-concentration VOC treatment, in particular to a low-concentration VOC treatment method and system based on a multi-stage adsorption technology, and the method comprises the steps: obtaining the adsorption temperature, the adsorption pressure and the VOC concentration in an adsorption tower, and respectively constructing an adsorption promotion characteristic value and an adsorption inhibition characteristic value at each sampling moment to obtain an adsorption gain coefficient; in combination with the correlation between the adsorption pressure and the VOC concentration and the change condition of the VOC concentration, obtaining an adsorption stable state value, analyzing the dispersion degree of the adsorption stable state value, obtaining the adsorption and desorption balance degree of the adsorbent in the adsorption tower, comparing the adsorption and desorption balance degree with a preset desorption balance threshold value, and judging the regeneration time of the adsorbent in the adsorption tower. The adsorption efficiency of the adsorbent in the low-concentration VOC organic waste gas treatment process is improved.

Description

Technical Field

[0001] The present application relates to the technical field of low-concentration VOC treatment, and specifically to a low-concentration VOC treatment method and system based on multi-stage adsorption technology. Background Art

[0002] Volatile Organic Compound (VOC) is a type of organic pollutant with a wide range of sources and great harm, such as harmful gases such as styrene, vinyl acetate, butyl acrylate, etc., and is also an important component of the formation of secondary particulate organic matter in the atmosphere. At present, the method of treating VOC organic waste gas by a single condensation process or a single adsorption process is difficult to meet the existing national emission standards in actual operation. With the development of VOC organic waste gas treatment technology, the method of treating VOC organic waste gas by "energy storage condensation + multi-stage adsorption" can not only recover the organic matter in VOC organic waste gas and turn waste into treasure, but also make the treated exhaust gas meet the exhaust emission standards, thereby avoiding serious threats to people's health and environmental safety.

[0003] In the process of the adsorbent in the adsorption tower adsorbing the low-concentration VOC organic waste gas discharged from the condensation unit, when the adsorbent adsorbs a certain amount of VOC organic waste gas, its adsorption capacity is greatly limited, and the adsorbed organic matter accumulates in the micropores of the adsorbent. When the adsorption amount of the adsorbent reaches saturation, its adsorption capacity decreases and the adsorption function will stop. The adsorbent needs to be regenerated to remove the organic matter and restore its adsorption performance to ensure that the adsorbent is always in the best working state. However, since the low-concentration VOC organic waste gas discharged from the condensation unit has a certain concentration change, the current process cannot accurately judge the regeneration time of the adsorbent in the adsorption tower, and it is easy to frequently regenerate the adsorbent in the adsorption tower, which will lead to low adsorption efficiency of the adsorbent during the treatment of low-concentration VOC organic waste gas. Summary of the invention

[0004] In order to solve the above technical problems, the purpose of this application is to provide a low-concentration VOC treatment method and system based on multi-stage adsorption technology. The technical solutions adopted are as follows: The present application embodiment provides a low-concentration VOC treatment method based on multi-stage adsorption technology, comprising the following steps: Obtain the adsorption temperature, adsorption pressure and VOC concentration at each sampling time during the physical adsorption of low-concentration VOC organic waste gas in the adsorption tower; The changes in adsorption pressure and adsorption temperature at each sampling time and its adjacent sampling time were analyzed, and the adsorption promotion characteristic value and adsorption inhibition characteristic value at each sampling time were constructed respectively. The adsorption gain coefficient of the adsorption environment in the adsorption tower at each sampling time was obtained by combining the adsorption promotion characteristic value and the adsorption inhibition characteristic value. According to the correlation between the adsorption pressure and the VOC concentration at each sampling moment and its neighboring sampling moments, and in combination with the adsorption gain coefficient and the change of the VOC concentration, the adsorption stable state value of the adsorbent in the adsorption tower at each sampling moment is obtained, and the preset time length is used as the measurement period. The discrete degree of the adsorption stable state value at all sampling moments in each measurement period is analyzed to obtain the adsorption-desorption equilibrium degree of the adsorbent in the adsorption tower in each measurement period; The comparison result between the adsorption-desorption equilibrium degree and the preset desorption equilibrium threshold is analyzed to judge the regeneration time of the adsorbent in the adsorption tower.

[0005] Preferably, the neighboring sampling moments of each sampling moment are a plurality of sampling moments with the shortest time intervals between the sampling moments.

[0006] Preferably, the construction of the adsorption promotion characteristic value at each sampling moment includes: The adsorption pressures at the sub-sampling moments and their neighboring sampling moments are combined into an adsorption pressure change vector at each sampling moment in chronological order; the difference between each element in the adsorption pressure change vector except the first element and its previous element is calculated, and the cumulative sum of all the differences in the adsorption pressure change vector at each sampling moment is taken as the adsorption promotion characteristic value at each sampling moment; For the adsorption temperature at each sampling time and its neighboring sampling time, the adsorption inhibition characteristic value at each sampling time is obtained accordingly.

[0007] Preferably, the expression of the adsorption gain coefficient of the adsorption environment in the adsorption tower at each sampling time is: , where is the adsorption gain coefficient of the adsorption environment in the adsorption tower at the tth sampling moment, is an exponential function with a natural constant as base, is the adsorption inhibition characteristic value at the t-th sampling moment, is the adsorption promotion characteristic value at the t-th sampling moment, To avoid constants with denominators equal to 0.

[0008] Preferably, the expression of the adsorption steady state value of the adsorbent in the adsorption tower at each sampling time is: , where is the adsorption steady state value of the adsorbent in the adsorption tower at the tth sampling moment, is the adsorption gain coefficient of the adsorption environment in the adsorption tower at the tth sampling moment, is the number of elements in the VOC concentration change vector at the i-th sampling moment, and are the rth and r-1th elements in the VOC concentration change vector at the i-th sampling moment, is the interaction strength at the t-th sampling moment, wherein the interaction strength at each sampling moment is calculated according to the correlation between the adsorption pressure and the VOC concentration at each sampling moment and its neighboring sampling moments.

[0009] Preferably, the VOC concentration change vector is composed of VOC concentrations at each sampling moment and its neighboring sampling moments arranged in chronological order.

[0010] Preferably, the acquisition of the interaction strength further includes: calculating the Pearson correlation coefficient between the adsorption pressure change vector and the VOC concentration change vector at each sampling moment, and using the calculation result of an exponential function with a natural constant as the base and the inverse of the Pearson correlation coefficient as the exponent as the interaction strength at each sampling moment; wherein the adsorption pressure at each sampling moment and its neighboring sampling moments constitutes the adsorption pressure change vector at each sampling moment.

[0011] Preferably, the expression of the adsorption-desorption equilibrium of the adsorbent in the adsorption tower in each measurement period is: , where is the adsorption-desorption equilibrium of the adsorbent in the adsorption tower in the uth measurement period, is the normalization function, is the number of sampling moments in the uth measurement period, is the adsorption steady state value at the i-th sampling moment in the u-th measurement period, is the mean of the adsorption steady-state values ​​at all sampling moments in the u-th measurement period, To avoid constants with denominators equal to 0.

[0012] Preferably, the determining of the regeneration time of the adsorbent in the adsorption tower comprises: If the adsorption-desorption equilibrium degree corresponding to the previous measurement period at the current moment exceeds the preset desorption equilibrium threshold, the current moment is the regeneration moment of the adsorbent in the adsorption tower, and the composite adsorbent in the adsorption tower is regenerated.

[0013] An embodiment of the present application also provides a low-concentration VOC treatment system based on multi-stage adsorption technology, including a memory, a processor, and a computer program stored in the memory and running on the processor, and when the processor executes the computer program, the steps of any one of the above methods are implemented.

[0014] From the above, it can be seen that the low-concentration VOC treatment method and system based on multi-stage adsorption technology provided by the present application have at least the following beneficial effects: The present application constructs an adsorption promotion characteristic value and an adsorption inhibition characteristic value based on the specific change characteristics of the adsorption pressure and the adsorption temperature, wherein the adsorption promotion characteristic value reflects the promotion effect of the change of the adsorption pressure on the adsorption of low-concentration VOC organic waste gas by the composite adsorbent, and the adsorption inhibition characteristic value reflects the inhibitory effect of the change of the adsorption temperature on the adsorption of low-concentration VOC organic waste gas by the composite adsorbent. Both reflect the influence of the change of the adsorption environment in the adsorption tower on the composite adsorbent. Based on the adsorption promotion characteristic value and the adsorption inhibition characteristic value, an adsorption gain coefficient is constructed to improve the accuracy of the subsequent adsorption stability analysis of the composite adsorbent during the adsorption process; Based on the adsorption gain coefficient and combined with the interaction between the adsorption pressure change and the VOC concentration change in the actual adsorption process and the VOC concentration change characteristics, the adsorption steady state value is constructed. The adsorption steady state value reflects the adsorption steady state characteristics of the composite adsorbent in the adsorption tower, which is used to accurately measure the adsorption-desorption equilibrium characteristics of the composite adsorbent in the subsequent process, thereby effectively adjusting the regeneration time of the adsorbent in the adsorption tower. Based on the adsorption steady-state value and its changing characteristics, the adsorption-desorption equilibrium is constructed. The adsorption-desorption equilibrium reflects the equilibrium relationship between the adsorption rate and the desorption rate of the composite adsorbent in the adsorption tower. The present application takes into account the equilibrium relationship between the adsorption rate and the desorption rate of the composite adsorbent, and utilizes the comparison result between the adsorption-desorption equilibrium and the adsorption-desorption equilibrium threshold to more accurately and effectively judge the regeneration time of the adsorbent in the adsorption tower, avoid the phenomenon of frequent regeneration of the adsorbent in the adsorption tower, and improve the adsorption efficiency of the adsorbent in the process of low-concentration VOC organic waste gas treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present application or the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0016] Figure 1 A flowchart of the steps of the low-concentration VOC treatment method based on multi-stage adsorption technology provided in this application; Figure 2 A schematic diagram of the data collection layout in the adsorption tower provided in this application; Figure 3 A schematic diagram of the adsorption temperature change provided for this application; Figure 4Schematic diagram of adsorption pressure change provided in this application. DETAILED DESCRIPTION

[0017] In order to further explain the technical means and effects adopted by the present application to achieve the predetermined invention purpose, the following is a detailed description of the low-concentration VOC treatment method and system based on multi-stage adsorption technology proposed in the present application, its specific implementation method, structure, characteristics and effects, in combination with the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "another embodiment" does not necessarily refer to the same embodiment. In addition, specific features, structures or characteristics in one or more embodiments may be combined in any suitable form.

[0018] Unless otherwise specified and limited, terms such as "comprises", "comprising" or any other variants thereof are intended to cover non-exclusive inclusion, so that a circuit structure, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such articles or devices. In the absence of further restrictions, an element defined by the sentence "comprising a ..." does not exclude the presence of other identical elements in the article or device including the element. In addition, the term "and\or" used herein includes any and all combinations of one or more related listed items. All technical and scientific terms used herein have the same meaning as those commonly understood by technicians in the technical field of this application.

[0019] The specific scheme of the low-concentration VOC treatment method and system based on multi-stage adsorption technology provided by the present application is described in detail below with reference to the accompanying drawings.

[0020] See also Figure 1 , which shows a flow chart of the steps of a low-concentration VOC treatment method based on multi-stage adsorption technology provided by an embodiment of the present application, including the following steps: Step 1: Obtain the adsorption temperature, adsorption pressure and VOC concentration at each sampling time during the physical adsorption of low-concentration VOC organic waste gas in the adsorption tower.

[0021] The purpose of this embodiment is to more accurately judge the regeneration time of the adsorbent in the adsorption tower by analyzing the actual adsorption capacity of the adsorbent during the adsorption process, avoid frequent regeneration of the adsorbent in the adsorption tower, and improve the adsorption efficiency of the adsorbent during the treatment of low-concentration VOC organic waste gas.

[0022] This embodiment uses a combination of a condensation process and an adsorption process to treat VOC organic waste gas, thereby improving the effect of purifying the VOC organic waste gas.

[0023] The VOC organic waste gas generated in the liquid chemical station enters the buffer tank, and the buffer tank also receives the desorption gas from the adsorption unit. After the VOC organic waste gas passes through the buffer tank, the VOC organic waste gas in the buffer tank is sent to the condensation unit through the fan for condensation treatment, so that most of the organic matter in the VOC organic waste gas is condensed in the condensation unit, thereby improving the purification degree of the VOC organic waste gas.

[0024] The condensing unit includes an energy storage device, a precooler, and a condenser, wherein the energy storage device is used to provide energy for the condensing unit and realize heat exchange treatment of the condensing unit; the precooler is used to precool the VOC organic waste gas sent from the buffer tank to reduce the energy consumption of the condensation section; the condenser is used to condense the VOC organic waste gas after precooling treatment, so that most of the organic matter in the VOC organic waste gas is condensed and separated in this condensing unit, and the condensate flows into the condensate tank and is regularly sent to the designated location through the condensate pump.

[0025] The low-concentration VOC organic waste gas discharged from the condensation unit enters an adsorption tower containing a composite adsorbent. A temperature sensor and a pressure sensor are provided at the composite adsorbent position in the adsorption tower, and a VOC concentration detection device is provided inside the adsorption tower. The adsorption temperature, adsorption pressure and VOC concentration in the adsorption tower can be monitored online through the temperature sensor, pressure sensor and VOC concentration detection device.

[0026] Specifically, the schematic diagram of data collection layout in the adsorption tower in this embodiment is as follows Figure 2 As shown, Figure 2 In the figure, numbers 1, 2, and 4 represent a temperature sensor, a VOC concentration detector device, and a pressure sensor, respectively, and number 3 represents an adsorption tower.

[0027] In the process of multi-stage adsorption of low-concentration VOC organic waste gas by the composite adsorbent in the adsorption tower, in order to accurately judge the regeneration time of the adsorbent in the adsorption tower and avoid frequent regeneration of the adsorbent in the adsorption tower, the adsorption temperature, adsorption pressure and VOC concentration are sampled in real time through the temperature sensor, pressure sensor and VOC concentration detector in the adsorption tower. The sampling time interval is 2s to obtain the actual adsorption temperature, adsorption pressure and VOC concentration in the adsorption tower at each sampling time.

[0028] So far, according to the above process of this embodiment, the adsorption temperature data, adsorption pressure data and VOC concentration data in the adsorption tower at each sampling time can be obtained.

[0029] Step 2: Analyze the changes in adsorption pressure and adsorption temperature at each sampling time and its adjacent sampling times, respectively construct the adsorption promotion characteristic value and adsorption inhibition characteristic value at each sampling time, and combine the adsorption promotion characteristic value and the adsorption inhibition characteristic value to obtain the adsorption gain coefficient of the adsorption environment in the adsorption tower at each sampling time.

[0030] In the process of multi-stage adsorption of low-concentration VOC organic waste gas, the adsorption capacity of the composite adsorbent in the adsorption tower is easily affected by the adsorption temperature and adsorption pressure. Under normal circumstances, within a relatively small range of adsorption pressure, as the adsorption pressure increases, the rate of adsorption of VOC organic waste gas by the composite adsorbent will first rise and then stabilize and reach adsorption saturation. Low temperature helps the composite adsorbent to adsorb VOC organic waste gas. As the adsorption temperature increases, the adsorption amount of the composite adsorbent will decrease. However, during the physical adsorption process in the adsorption tower, due to the change in the concentration of VOC organic waste gas and the generation of adsorption heat effect during the adsorption process, the adsorption temperature and adsorption pressure of the composite adsorbent in the adsorption tower are easily unstable, causing the adsorption capacity of the composite adsorbent in the adsorption tower to change to varying degrees.

[0031] Specifically, in this embodiment, the schematic diagram of the adsorption temperature change is as follows Figure 3 As shown, the horizontal axis is time, the unit is s, and the vertical axis is adsorption temperature, the unit is ℃; the schematic diagram of the adsorption pressure change in this embodiment is as shown Figure 4 As shown, the horizontal axis is time, the unit is s, and the vertical axis is adsorption pressure, the unit is Kpa.

[0032] In order to analyze the influence of the adsorption environment on the composite adsorbent during the multi-stage adsorption of low-concentration VOC organic waste gas, the T sampling moments with the closest time interval between each sampling moment are recorded as the T neighboring sampling moments of each sampling moment, and the adsorption temperature and adsorption pressure of each sampling moment and its T neighboring sampling moments are respectively recorded as vectors composed of the adsorption temperature change vector and the adsorption pressure change vector of each sampling moment in chronological order, which respectively characterize the change characteristics of the adsorption temperature and adsorption pressure in the adsorption tower of the multi-stage adsorption. In this embodiment, T is taken as 20.

[0033] In order to analyze the influence of adsorption pressure and adsorption temperature on the composite adsorbent in the adsorption environment, the difference between each element except the first element and the previous element in the adsorption pressure change vector at the t-th sampling moment is calculated. In this embodiment, for the convenience of understanding and expression, the difference between each element except the first element in the adsorption pressure change vector and the previous element is recorded as each pressure increase or decrease value. The pressure increase or decrease value reflects the characteristics of the increase or decrease of the adsorption pressure. The positive pressure increase or decrease value and the larger the value, the more it indicates that the adsorption pressure in the adsorption tower shows an increasing change characteristic.

[0034] Furthermore, in order to reflect the promoting effect of adsorption pressure on the adsorption of low-concentration VOC organic waste gas by the composite adsorbent, the cumulative sum of all the pressure increase and decrease values ​​in the adsorption pressure change vector at the t-th sampling moment is calculated in this embodiment, and recorded as the adsorption promotion characteristic value at the t-th sampling moment. The adsorption promotion characteristic value reflects the promoting effect of the change of adsorption pressure on the adsorption of low-concentration VOC organic waste gas by the composite adsorbent. The more significant the increase in the adsorption pressure in the adsorption tower, the greater the adsorption promotion characteristic value, indicating that when the adsorption amount of the composite adsorbent has not reached the saturation state, the composite adsorbent in the adsorption tower can be promoted to quickly adsorb VOC organic waste gas.

[0035] At the same time, the same calculation method as the above-mentioned adsorption promotion characteristic value is used. For the adsorption temperature at each sampling moment and its neighboring sampling moments, the difference between each element except the first element in the adsorption temperature change vector at the t-th sampling moment and the previous element is calculated accordingly. For the convenience of understanding and expression, it is recorded as each temperature increase or decrease value. Among them, the temperature increase or decrease value reflects the characteristics of the increase or decrease of the adsorption temperature. The temperature increase or decrease value is a positive value and the larger the value is, the more it represents the increasing change characteristics of the adsorption temperature in the adsorption tower at this time, and the less conducive it is for the composite adsorbent to physically absorb VOC organic waste gas.

[0036] Accordingly, the cumulative sum of all the temperature increase and decrease values ​​in the adsorption temperature change vector at the t-th sampling moment is calculated and recorded as the adsorption inhibition characteristic value at the t-th sampling moment. The adsorption inhibition characteristic value reflects the inhibitory effect of the adsorption temperature change on the adsorption of low-concentration VOC organic waste gas by the composite adsorbent. The more significant the growth characteristics of the adsorption temperature in the adsorption tower, the larger the adsorption inhibition characteristic value, indicating that the growth of the adsorption temperature in the adsorption tower has a stronger inhibitory effect on the adsorption of low-concentration VOC organic waste gas by the composite adsorbent.

[0037] Based on the above analysis, the adsorption gain coefficient of the adsorption environment in the adsorption tower at each sampling time is calculated. In this embodiment, the specific calculation relationship is: , where is the adsorption gain coefficient of the adsorption environment in the adsorption tower at the tth sampling moment, is an exponential function with a natural constant as base, is the adsorption inhibition characteristic value at the t-th sampling moment, is the adsorption promotion characteristic value at the t-th sampling moment, To avoid a constant with a denominator of 0, the value range is 0 to 1, and in this embodiment, the value is 0.1. The adsorption gain coefficient reflects the gain degree of the change of the adsorption environment in the adsorption tower on the adsorption of VOC organic waste gas by the composite adsorbent. The larger the adsorption promotion characteristic value and the smaller the adsorption inhibition characteristic value, the more beneficial it is for the composite adsorbent in the adsorption tower to physically adsorb VOC organic waste gas when the composite adsorbent has not reached the adsorption saturation state. That is, the higher the gain degree of the composite adsorbent adsorbing VOC organic waste gas at this time, the greater the adsorption gain coefficient.

[0038] Step three: According to the correlation between the adsorption pressure and the VOC concentration at each sampling moment and its adjacent sampling moments, and combined with the adsorption gain coefficient and the change of the VOC concentration, the adsorption stable state value of the adsorbent in the adsorption tower at each sampling moment is obtained, and the preset time length is used as the measurement period. The discrete degree of the adsorption stable state value at all sampling moments in each measurement period is analyzed to obtain the adsorption-desorption equilibrium degree of the adsorbent in the adsorption tower in each measurement period.

[0039] Furthermore, when the adsorption of the composite adsorbent has not reached saturation, the VOC concentration in the adsorption tower should show a more significant decrease with the increase of the adsorption pressure. At this time, the interaction between the two is closer. However, when the change of the adsorption environment in the adsorption tower has a higher gain on the adsorption of VOC organic waste gas by the composite adsorbent, if the interaction between the change of VOC concentration in the adsorption tower and the change of adsorption pressure is weaker, then the composite adsorbent in the adsorption tower adsorbs enough organic matter, indicating that it is closer to the time to regenerate the adsorbent in the adsorption tower, and the ability of the composite adsorbent to adsorb low-concentration VOC organic waste gas needs to be improved.

[0040] In order to analyze the state of the composite adsorbent in the adsorption tower close to adsorption stability, the VOC concentrations at each sampling moment and its T neighboring sampling moments are arranged in chronological order to form a vector, which is recorded as the VOC concentration change vector at each sampling moment. Further, the Pearson correlation coefficient between the adsorption pressure change vector and the VOC concentration change vector at each sampling moment is calculated, and the calculation result of the exponential function with a natural constant as the base and the opposite number of the Pearson correlation coefficient as the exponent is used as the interaction intensity at each sampling moment. The calculation of the Pearson correlation coefficient is a well-known technology and the specific process will not be repeated here.

[0041] It can be understood that the interaction strength reflects the interaction relationship between the change in adsorption pressure and the change in VOC concentration in the adsorption tower. The stronger the interaction relationship between the change in adsorption pressure and the change in VOC concentration in the adsorption tower, the higher the interaction strength.

[0042] Based on the above analysis, the adsorption stable state value of the adsorbent in the adsorption tower at each sampling time is calculated. In this embodiment, the specific calculation relationship is: , where is the adsorption steady state value of the adsorbent in the adsorption tower at the tth sampling moment, is the number of elements in the VOC concentration change vector at the i-th sampling moment, is the interaction strength at the tth sampling moment, and are the rth and r-1th elements in the VOC concentration change vector at the i-th sampling moment, respectively. If the adsorption gain coefficient of the adsorption environment in the adsorption tower is larger, it means to a certain extent that the adsorption environment is beneficial to the physical adsorption of VOC organic waste gas by the composite adsorbent. At the same time, if the interaction strength is smaller and the VOC concentration change is smaller, the interaction relationship between the VOC concentration change and the adsorption pressure change in the adsorption tower is weaker, which means to a certain extent that the composite adsorbent in the adsorption tower is more likely to tend to the adsorption stable state at this time. At this time, the closer it is to the time of regenerating the adsorbent in the adsorption tower, the greater the adsorption stable state value.

[0043] Furthermore, in order to more accurately adjust the regeneration time of the adsorbent in the adsorption tower and avoid frequent regeneration of the adsorbent in the adsorption tower, one minute is used as a measurement period. If the change in the adsorption stable state value of the adsorbent in the adsorption tower at all sampling times within a certain measurement period tends to be horizontal, it can reflect that the adsorption rate of the composite adsorbent in the adsorption tower is equal to the desorption rate. At this time, the composite adsorbent absorbs low-concentration VOC organic waste gas to reach a equilibrium state, indicating that it is time to regenerate the adsorbent in the adsorption tower.

[0044] Based on the above analysis, the adsorption-desorption equilibrium of the adsorbent in the adsorption tower in each measurement period is calculated. In this embodiment, the specific calculation relationship is: , where is the adsorption-desorption equilibrium of the adsorbent in the adsorption tower in the uth measurement period, is the normalization function, is the number of sampling moments in the uth measurement period, is the adsorption steady state value at the i-th sampling moment in the u-th measurement period, is the mean of the adsorption steady-state values ​​at all sampling moments in the u-th measurement period.

[0045] It can be understood that the smaller the difference between the adsorption steady-state value and its average level during the measurement period, and the larger the adsorption steady-state value, the more it characterizes that the change in the adsorption steady-state value at this time is close to the average level change, and the higher the adsorption steady-state of the composite adsorbent, the more accurately it can reflect that the composite adsorbent absorbs low-concentration VOC organic waste gas to reach a equilibrium state. At this time, the adsorption rate of the composite adsorbent in the adsorption tower is close to the desorption rate, and the greater the adsorption-desorption equilibrium degree.

[0046] Step 4: Analyze the comparison result between the adsorption-desorption equilibrium degree and the preset desorption equilibrium threshold value, and judge the regeneration time of the adsorbent in the adsorption tower.

[0047] In order to accurately and effectively judge the regeneration time of the adsorbent in the adsorption tower and avoid the phenomenon of frequent regeneration of the adsorbent in the adsorption tower, in the process of multi-stage adsorption of low-concentration VOC organic waste gas by the composite adsorbent in the adsorption tower, the adsorption-desorption equilibrium of the composite adsorbent in the adsorption tower in each measurement period is monitored in real time. If the adsorption-desorption equilibrium corresponding to the previous measurement period at the current moment exceeds the preset desorption equilibrium threshold, it means that the composite adsorbent has adsorbed enough organic matter and the composite adsorbent should be regenerated. At this time, the PLC controller triggers an alarm signal, starts the vacuum pump, and regenerates the composite adsorbent in the adsorption tower by a vacuum desorption method. In this embodiment, the desorption equilibrium threshold is 0.87; If the adsorption-desorption equilibrium corresponding to the previous measurement period at the current moment does not exceed the desorption equilibrium threshold, it means that the composite adsorbent has not adsorbed enough organic matter and the composite adsorbent should not be regenerated. At this time, the PLC controller does not trigger the alarm signal and continues to perform physical adsorption through the composite adsorbent in the adsorption tower, so as to avoid frequent regeneration of the adsorbent in the adsorption tower, thereby ensuring that the composite adsorbent is in the best working state for a long time and improving the adsorption efficiency of the adsorbent during the treatment of low-concentration VOC organic waste gas.

[0048] At this point, according to the above process of this embodiment, the regeneration status of the adsorbent in the adsorption tower can be judged.

[0049] Based on the same inventive concept as the above method, an embodiment of the present application also provides a low-concentration VOC treatment system based on multi-stage adsorption technology, including a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, the steps of any one of the above-mentioned low-concentration VOC treatment methods based on multi-stage adsorption technology are implemented.

[0050] It is to be understood that the sequence of the embodiments of the present application described above is for description only and does not represent the advantages and disadvantages of the embodiments. The above describes specific embodiments of the present specification. In addition, the processes depicted in the accompanying drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0051] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0052] The above content is only an implementation method of the present application and is not intended to limit the scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly used in other related technical fields, are also included in the protection scope of the present application.

Claims

1. A low-concentration VOC treatment method based on multi-stage adsorption technology, characterized in that: The following steps are involved: Obtain the adsorption temperature, adsorption pressure and VOC concentration at each sampling time during the physical adsorption of low-concentration VOC organic waste gas in the adsorption tower; The changes in adsorption pressure and adsorption temperature at each sampling time and its adjacent sampling time were analyzed, and the adsorption promotion characteristic value and adsorption inhibition characteristic value at each sampling time were constructed respectively. The adsorption gain coefficient of the adsorption environment in the adsorption tower at each sampling time was obtained by combining the adsorption promotion characteristic value and the adsorption inhibition characteristic value. According to the correlation between the adsorption pressure and the VOC concentration at each sampling moment and its neighboring sampling moments, and in combination with the adsorption gain coefficient and the change of the VOC concentration, the adsorption stable state value of the adsorbent in the adsorption tower at each sampling moment is obtained, and the preset time length is used as the measurement period. The discrete degree of the adsorption stable state value at all sampling moments in each measurement period is analyzed to obtain the adsorption-desorption equilibrium degree of the adsorbent in the adsorption tower in each measurement period; The comparison result between the adsorption-desorption equilibrium degree and the preset desorption equilibrium threshold is analyzed to judge the regeneration time of the adsorbent in the adsorption tower.

2. The low-concentration VOC treatment method based on multi-stage adsorption technology according to claim 1, characterized in that: The neighboring sampling moments of each sampling moment are a plurality of sampling moments with the shortest time intervals between the sampling moments.

3. The low-concentration VOC treatment method based on multi-stage adsorption technology according to claim 2, characterized in that: The construction of the adsorption promotion characteristic value at each sampling moment includes: The adsorption pressures at the sub-sampling moments and their neighboring sampling moments are combined into an adsorption pressure change vector at each sampling moment in chronological order; the difference between each element in the adsorption pressure change vector except the first element and its previous element is calculated, and the cumulative sum of all the differences in the adsorption pressure change vector at each sampling moment is taken as the adsorption promotion characteristic value at each sampling moment; For the adsorption temperature at each sampling time and its neighboring sampling time, the adsorption inhibition characteristic value at each sampling time is obtained accordingly.

4. The low-concentration VOC treatment method based on multi-stage adsorption technology according to claim 1, characterized in that: The expression of the adsorption gain coefficient of the adsorption environment in the adsorption tower at each sampling time is: , where is the adsorption gain coefficient of the adsorption environment in the adsorption tower at the tth sampling moment, is an exponential function with a natural constant as base, is the adsorption inhibition characteristic value at the t-th sampling moment, is the adsorption promotion characteristic value at the t-th sampling moment, To avoid constants with denominators equal to 0.

5. The low-concentration VOC treatment method based on multi-stage adsorption technology according to claim 1, characterized in that: The expression of the adsorption steady state value of the adsorbent in the adsorption tower at each sampling time is: , where is the adsorption steady state value of the adsorbent in the adsorption tower at the tth sampling moment, is the adsorption gain coefficient of the adsorption environment in the adsorption tower at the tth sampling moment, is the number of elements in the VOC concentration change vector at the i-th sampling moment, and are the rth and r-1th elements in the VOC concentration change vector at the i-th sampling moment, is the interaction strength at the t-th sampling moment, wherein the interaction strength at each sampling moment is calculated according to the correlation between the adsorption pressure and the VOC concentration at each sampling moment and its neighboring sampling moments.

6. The low-concentration VOC treatment method based on multi-stage adsorption technology according to claim 5, characterized in that: The VOC concentration change vector is composed of the VOC concentrations at each sampling time and its neighboring sampling time arranged in chronological order.

7. The low-concentration VOC treatment method based on multi-stage adsorption technology according to claim 5, characterized in that: The acquisition of the interaction strength further includes: calculating the Pearson correlation coefficient between the adsorption pressure change vector and the VOC concentration change vector at each sampling moment, and using the calculation result of an exponential function with a natural constant as the base and the opposite number of the Pearson correlation coefficient as the exponent as the interaction strength at each sampling moment; wherein the adsorption pressure at each sampling moment and its neighboring sampling moments constitutes the adsorption pressure change vector at each sampling moment.

8. The low-concentration VOC treatment method based on multi-stage adsorption technology according to claim 1, characterized in that: The expression of the adsorption-desorption equilibrium of the adsorbent in the adsorption tower in each measurement period is: , where is the adsorption-desorption equilibrium of the adsorbent in the adsorption tower in the uth measurement period, is the normalization function, is the number of sampling moments in the uth measurement period, is the adsorption steady state value at the i-th sampling moment in the u-th measurement period, is the mean of the adsorption steady-state values ​​at all sampling moments in the u-th measurement period, To avoid constants with denominators equal to 0.

9. The low-concentration VOC treatment method based on multi-stage adsorption technology according to claim 1, characterized in that: The step of determining the regeneration time of the adsorbent in the adsorption tower comprises: If the adsorption-desorption equilibrium degree corresponding to the previous measurement period at the current moment exceeds the preset desorption equilibrium threshold, the current moment is the regeneration moment of the adsorbent in the adsorption tower, and the composite adsorbent in the adsorption tower is regenerated.

10. A low-concentration VOC treatment system based on multi-stage adsorption technology, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 9 are implemented.

Images