An automatic material balance method for double-tower distillation of polluted solvents

Abstract

The present invention provides an automatic material balance method for double-tower distillation of dirty solvents. The automatic material balance method for double-tower distillation of dirty solvents of the present invention comprises the following steps: S1: obtaining the original data of the materials of the double-tower distillation process of dirty solvents and constructing an original database; S2: obtaining the actual volume data and theoretical volume data of the materials according to the original data, and constructing a material balance model library; S3: constructing an evaluation model library composed of a facility operation database and a material supervision database, comparing, evaluating and adjusting the actual volume data and theoretical volume data of the materials, and adjusting the process parameters of the double-tower distillation of dirty solvents using the evaluation model library. The present invention optimizes the operation mode of the double-tower distillation process of dirty solvents by real-time balancing and adjusting the materials of the double-tower distillation process of dirty solvents, and ensures the continuous and stable operation of the double-tower distillation process system of dirty solvents.

Description

Technical Field

[0001] The invention relates to the technical field of double-tower distillation, in particular to an automatic material balance method for double-tower distillation of polluted solvents. Background Art

[0002] The double-tower distillation process of the contaminated solvent in the spent fuel reprocessing plant separates kerosene, extractant and low-boiling kerosene through the TBP distillation tower and the kerosene distillation tower. The materials involved mainly include extractant, reused kerosene, low-boiling kerosene and distillation residue. The material composition in the non-radioactive stage only needs to consider the balance of TBP and kerosene, but there are interferences of nuclides and complex inorganic salts in the radioactive stage, and uranium and plutonium nuclides need to be considered, resulting in deviations between the total actual material balance and parameter adjustment during the continuous operation process. There is often material imbalance in the process, and the parameters deviate from the normal operating range, which may cause nuclear safety risks.

[0003] At present, the material balance method for the double-tower distillation process of contaminated solvents has the following disadvantages: 1) There is insufficient correlation between operating parameters, product content, and material composition; 2) There is a lack of a material balance error alarm system, and it is impossible to accurately determine whether the system has reached equilibrium; 3) When the source term composition changes, there is no clear correlation change to adjust the operating parameters.

[0004] In view of this, the present invention is proposed. Summary of the invention

[0005] The object of the present invention is to provide an automatic material balancing method for a double-tower distillation of a contaminated solvent, which optimizes the operation mode of the double-tower distillation process of a contaminated solvent by real-time balancing and adjusting the materials of the double-tower distillation process of a contaminated solvent, and ensures the continuous and stable operation of the double-tower distillation process system of the contaminated solvent.

[0006] The present invention provides an automatic material balance method for double-tower distillation of contaminated solvents, comprising the following steps:

[0007] S1: Obtain the original data of the materials of the double-tower distillation process of the contaminated solvent and build the original database;

[0008] S2: Obtain the actual volume data and theoretical volume data of the material based on the original data, and build a material balance model library;

[0009] S3: Construct an evaluation model library consisting of a facility operation database and a material supervision database to compare, evaluate and adjust the actual volume data of materials with the theoretical volume data, and use the evaluation model library to adjust the process parameters of the double-tower distillation of contaminated solvents.

[0010] The double-tower distillation process system for polluted solvents comprises a feed tank, a falling film reboiler, a TBP distillation tower and a kerosene distillation tower which are arranged in sequence, the bottom of the falling film reboiler is connected to a distillation residue storage tank, the bottom of the TBP distillation tower is connected to the TBP storage tank through a feed pipe, a TBP distillation tower reboiler is arranged in parallel on the feed pipe, the top of the TBP distillation tower is connected to a TBP distillation tower top reflux tank through a TBP distillation tower top condenser, the bottom of the kerosene distillation tower is connected to a kerosene storage tank, and the top of the kerosene distillation tower is connected to a kerosene distillation tower top reflux tank through a kerosene distillation tower top condenser.

[0011] The feed tank is mainly used to provide the contaminated solvent generated by the spent fuel reprocessing process; the falling film reboiler is a heating device, which is mainly used to heat and vaporize the contaminated solvent. The vaporized steam enters the TBP distillation tower, and the distillation residue discharged from the bottom of the falling film reboiler separation chamber enters the distillation residue storage tank; the distillation residue storage tank is mainly used to store the distillation residue discharged from the bottom of the falling film reboiler; the TBP distillation tower kettle reboiler is mainly used to reheat and vaporize the condensed liquid of the TBP distillation tower; the TBP distillation tower is mainly used to separate the TBP fraction and the kerosene fraction; the TBP distillation tower top reflux tank mainly plays a control role. The kerosene distillation tower is mainly used to re-distill the crude kerosene fraction separated by the TBP distillation tower; the kerosene storage tank is mainly used to store the kerosene fraction separated by the kerosene distillation tower; the top reflux tank of the kerosene distillation tower mainly plays the role of controlling the balance of the kerosene distillation tower; the light kerosene storage tank is mainly used to store the light kerosene fraction separated by the kerosene distillation tower; the top condenser of the TBP distillation tower is mainly used to cool the TBP fraction separated by the TBP distillation tower; the top condenser of the kerosene distillation tower is mainly used to cool the light kerosene fraction separated by the kerosene distillation tower.

[0012] The feed tank is the input quantity, the distillation residue storage tank, TBP storage tank, kerosene storage tank, and light kerosene storage tank are the output quantities, and the serial numbers of falling film reboiler, TBP distillation tower reboiler, TBP distillation tower, TBP distillation tower top reflux tank, kerosene distillation tower, and kerosene distillation tower top reflux tank are the distillation process quantities, among which the feed liquid in the TBP distillation tower reboiler, TBP distillation tower, and kerosene distillation tower is a mixture of gas and liquid. By balancing the changes in input quantity, output quantity, and distillation process quantity over a period of time, it is confirmed whether the feed liquid is balanced. According to the material balance results, it is verified whether the TBP distillation tower and kerosene distillation tower are in gas-liquid balance, material balance, and heat balance, and then the process parameters are adjusted, and the accuracy of the instrument indication is further verified. By associating material balance with operating data, the stability of the process production line can be effectively guaranteed. At the same time, the material supervision warehouse is incorporated into the integrated circulation system, and the goal of stabilizing product quality can be achieved through material balance.

[0013] The process data of the double-tower distillation of dirty solvents includes three types: original database, material balance model library and evaluation model library; among them, the original data mainly includes DCS monitoring data, which can be displayed in real time according to the actual operation of the double-tower distillation process production line of dirty solvents, and entered into the original database. More specifically, the original data can include the liquid level data of the feed tank, residual liquid storage tank, TBP storage tank, kerosene storage tank, and light kerosene storage tank, as well as the temperature data, pressure data and liquid level data of the falling film reboiler, TBP distillation tower, and kerosene distillation tower.

[0014] The input quantity in the material balance model library is the feed part, the distillation process quantity is the falling film reboiler, TBP distillation tower and kerosene distillation tower part, and the output quantity is the product extraction part. The input and output feed liquids are in liquid state, and the volume is directly balanced by the liquid level. The distillation process quantity involves the balance in the distillation tower. The feed liquid is a mixture of gas and liquid. It is necessary to ensure the gas-liquid balance in the distillation tower and the stability of heat and mass transfer efficiency. The liquid level on the DCS screen is a single reading. The liquid level can be converted into volume according to the type of storage tank. The relationship between the liquid level and volume can be fitted into a univariate multi-function, and the correlation coefficient R after fitting is required. 2 ≥0.99. The initial liquid level and the final liquid level can be read and converted into the volume within a certain period of time according to the fitted function relationship. The present invention matches the volume-liquid level balance with the double tower parameters for verification, and realizes the material volume balance through real-time balance of DCS liquid level signals.

[0015] Specifically, the material balance model library mainly includes actual volume data and theoretical volume data of the material; wherein the actual volume data can be converted according to the liquid level data in the original data, and the theoretical volume data can be calculated according to the formula.

[0016] The actual volume data acquisition method of the material may include:

[0017] A) obtaining a liquid level-volume function based on a plurality of sets of corresponding liquid level data and volume data;

[0018] B) Based on the liquid level data in the original data, the actual volume data of the material is obtained using the liquid level-volume function.

[0019] The volume change of each storage tank per unit time is calculated through the change of material liquid level. According to the change of material liquid level per unit time, it is converted into the change of material liquid volume per unit time through the liquid level-volume function. The change of material liquid volume is used to confirm whether the incoming and outgoing materials in the system are balanced. If the deviation exceeds 10%, the cause analysis and inspection are carried out according to the balance results.

[0020] The volume in the tower is kept constant by controlling the liquid level of the falling film reboiler, TBP distillation tower, TBP distillation tower reboiler and kerosene distillation tower. Since the material, heat and gas-liquid in the distillation tower are in a dynamic equilibrium state, the material balance within a fixed time period is more accurate when the liquid level of the distillation tower is kept constant.

[0021] The feed tank, TBP storage tank, kerosene storage tank, light kerosene storage tank, and distillation residual liquid storage tank are all liquids. The direct liquid level-volume function can convert the liquid level into volume, and generally there will not be a large deviation. However, both gas and liquid exist in the falling film reboiler and the distillation tower. The above equipment can only accurately balance the liquid phase volume. By separating the dynamic balance part of the material from the static balance material, and balancing the static and dynamic materials respectively, it is possible to basically obtain whether the gas-liquid balance in the distillation tower is normal, and then achieve the balance goal.

[0022] The above-mentioned balancing system avoids system defects caused by instrument display failures. Since there are many instruments involved in the distillation process, when an instrument fails or displays an error, it may cause system operation disorder. By performing real-time balancing of materials in the system, operational errors caused by instrument failures can be avoided. At the same time, instrument display errors during the operation of the distillation tower can also be discovered in time, achieving the goal of accurate monitoring.

[0023] In step S2, the actual volume data of the material may include the volume change V1 of the dirty solvent in the feed tank, the volume change V2 of the distillation residue in the distillation residue storage tank, the volume change V3 of the TBP product in the TBP storage tank, the volume change V4 of the kerosene product in the kerosene storage tank, and the volume change V5 of the light kerosene in the light kerosene storage tank, preferably including the volume change V3 of the TBP product in the TBP storage tank and the volume change V4 of the kerosene product in the kerosene storage tank. The theoretical volume data of the material may include the theoretical volume V2′ of the distillation residue, the theoretical volume V3′ of the TBP product, the theoretical volume V4′ of the kerosene product, and the theoretical volume V5′ of the light kerosene, preferably including the theoretical volume V3′ of the TBP product and the theoretical volume V4′ of the kerosene product.

[0024] The theoretical volume V2' of the distillation residue is obtained by the following formula:

[0025] V2′=V×C%

[0026] The theoretical volume V3′ of TBP product is obtained by the following formula:

[0027]

[0028] The theoretical volume V4′ of kerosene product is obtained by the following formula:

[0029]

[0030] The theoretical volume V5′ of light kerosene is obtained by the following formula:

[0031] V5′=V×D%

[0032] In the above formula: V is the treatment volume of the contaminated solvent; A is the TBP content of the contaminated solvent, which is obtained by sampling and analysis in the feed tank; B is the TBP content of the TBP product, which is obtained by sampling and analysis in the TBP storage tank; C is the proportion of residual liquid production, which can be calculated by converting it into volume through the change in the liquid level of the residual liquid storage tank; D is the proportion of light kerosene, which can be calculated by converting it into volume through the change in the liquid level of the light kerosene storage tank; ρ1 is the density of kerosene, which is obtained by sampling and analysis in the kerosene storage tank; ρ2 is the density of light kerosene, which is obtained by sampling and analysis in the light kerosene storage tank.

[0033] The phase in the feed tank is liquid, and the treatment volume V of the dirty solvent is the volume change of the dirty solvent in the feed tank over a period of time, that is, V=V1. The phases in the distillation residue storage tank, TBP storage tank, kerosene storage tank and light kerosene storage tank are liquid, and the volume calculated based on the liquid level is also relatively stable. Therefore, it is believed that the volume change V2 of the distillation residue in the distillation residue storage tank, the volume change V3 of the TBP product in the TBP storage tank, the volume change V4 of the kerosene product in the kerosene storage tank, and the volume change V5 of the light kerosene in the light kerosene storage tank can accurately measure the changes in the above storage tanks over a period of time; however, due to the gas-liquid mixed state in the falling film reboiler, TBP distillation tower and kerosene distillation tower, the actual amount of the product after distillation deviates from the theoretical value, which can be reduced by controlling the liquid level of the above equipment to be stable. In addition, the distillation residue and light kerosene are extracted as by-products at a constant ratio, so the volume deviation has little effect and the result is controllable. The volume changes of actual TBP products and kerosene products are more obvious. When the deviation is controlled within ±10%, it is considered that the parameters are normal fluctuations. When the deviation within a unit time exceeds the above range, it is necessary to interlock and adjust the relevant parameters to achieve the goal of adjusting process parameters through material balance.

[0034] Specifically, the actual volume data of the TBP product was compared and evaluated with the theoretical volume data in the following manner, and the process parameters of the double-tower distillation of the contaminated solvent were adjusted as follows according to the evaluation results:

[0035] When -10%≤(V3-V3ˊ) / V3ˊ≤10%, the TBP product extraction is stable;

[0036] When (V3-V3ˊ) / V3ˊ≤-10%, the TBP output is low and the liquid level in the main distillation tower is high. The interlock increases the output flow rate and controls the liquid level to be stable within the normal required range.

[0037] When (V3-V3ˊ) / V3ˊ≥10%, the TBP output is too high and the liquid level in the main distillation tower is too low. The interlock reduces the output flow rate and controls the liquid level to be stable within the normal requirement range.

[0038] The actual volume data of kerosene products were compared and evaluated with the theoretical volume data in the following manner, and the process parameters of the double-tower distillation of the contaminated solvent were adjusted as follows according to the evaluation results:

[0039] When -10% ≤ (V4-V4ˊ) / V4ˊ ≤ 10%, kerosene product production is stable;

[0040] When (V4-V4ˊ) / V4ˊ≤-10%, the kerosene production is too low or the reflux flow is too large, and the falling film reboiler liquid level continues to rise, the interlock increases the kerosene production flow or reduces the reflux flow, and controls the main distillation tower reflux tank liquid level to be stable within the normal requirement range;

[0041] When (V4-V4ˊ) / V4ˊ≥10%, the kerosene production is too high, the liquid level in the reflux tank at the top of the main distillation tower or the liquid level in the reboiler in the bottom of the kerosene distillation tower continues to decrease, and the kerosene production flow is reduced by interlocking to control the liquid level in the reflux tank of the main distillation tower and the liquid level in the reboiler in the bottom of the kerosene distillation tower to be stable within the normal requirement range.

[0042] In step S3, the evaluation model library is composed of a facility operation database and a material supervision database. The facility operation data and material sampling and analysis data can be composed of relevant data from the radioactive commissioning and trial operation stages, and the equipment operation data and material analysis results from the stable stage of product indicators are selected; at the same time, the relevant data obtained by the material balance library are compared in the evaluation model library, and the system judges the resulting deviations. Finally, the comparison results formed by the evaluation model library form a relevant report to guide production practice. The generated data is also entered into the material balance library, and the algorithm is continuously iterated to achieve stable operation of the contaminated solvent distillation facility.

[0043] Based on the previous theoretical simulation and actual operation results, the facility operation database and material supervision database are formed, and the facility operation database and material supervision database are improved according to the actual operation results. In addition, the complete data of the dirty solvent double-tower distillation process is compared with the facility operation database and the material supervision database, and the temperature, liquid level and pressure in the dirty solvent double-tower distillation process are adjusted according to the comparison results to continuously optimize the dirty solvent double-tower distillation process.

[0044] The present invention designs a three-stage model and converts the liquid level signal into volume, so as to achieve real-time balance of whether the material is conserved and whether the production line is running stably. The first section is the feeding part, the second section is the TBP distillation tower and the kerosene distillation tower part, and the third section is the product extraction part; the feed liquid in the first and third sections is in liquid state, and is directly converted into volume for balance through liquid level. The second section involves the balance in the distillation tower, and the material involves gas and liquid. It is necessary to ensure the gas-liquid balance in the distillation tower, and the heat transfer and mass transfer efficiency are stable. The present invention matches the volume-liquid level balance with the double tower parameters for verification, and achieves the goal of accurately regulating the distillation tower parameters according to the material balance through real-time balance of the DCS liquid level signal.

[0045] The present invention can timely grasp the operation dynamics of the distillation facility by real-time balancing of materials, waste liquid and waste gas of the contaminated solvent distillation facility, and can feed back abnormal operating conditions that may exist in the double towers during the distillation process in real time through balancing data, so that it is convenient for operating personnel to take control measures, realize comprehensive monitoring of the system, and ensure the continuous and stable operation of the contaminated solvent distillation facility of the spent fuel reprocessing plant; in addition, the key control parameters in the contaminated solvent double-tower distillation process are compared with each other through the evaluation model library, so as to optimize the operation mode of the distillation facility. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0047] Figure 1 It is a structural schematic diagram of a double-tower distillation process system for polluted solvents;

[0048] Figure 2 This is a schematic diagram of the database model.

[0049] Description of reference numerals:

[0050] 1: Feed tank; 2: Falling film reboiler; 3: Distillation residue storage tank; 4: TBP distillation tower reboiler; 5: TBP distillation tower; 6: TBP distillation tower top reflux tank; 7: TBP storage tank; 8: Kerosene distillation tower; 9: Kerosene storage tank; 10: Kerosene distillation tower top reflux tank; 11: Light kerosene storage tank; 12: TBP distillation tower top condenser; 13: Kerosene distillation tower top condenser. DETAILED DESCRIPTION

[0051] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0052] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form also includes the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this description, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0053] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0054] Example 1

[0055] Combination Figure 1 , Figure 2 As shown, the method for automatic material balance of double-tower distillation of contaminated solvents in this embodiment comprises the following steps:

[0056] S1: Obtain the original data of the materials of the double-tower distillation process of the contaminated solvent and build the original database;

[0057] S2: Obtain the actual volume data and theoretical volume data of the material based on the original data, and build a material balance model library;

[0058] S3: Construct an evaluation model library consisting of a facility operation database and a material supervision database to compare, evaluate and adjust the actual volume data of materials with the theoretical volume data, and use the evaluation model library to adjust the process parameters of the double-tower distillation of contaminated solvents.

[0059] The double-tower distillation process of the dirty solvent adopts the double-tower distillation process system of the dirty solvent; the double-tower distillation process system of the dirty solvent comprises a feed tank 1, a falling film reboiler 2, a TBP distillation tower 5 and a kerosene distillation tower 8 which are arranged in sequence, the bottom of the falling film reboiler 2 is connected to the distillation residue storage tank 3, the bottom of the TBP distillation tower 5 is connected to the TBP storage tank 7 through a feed pipe, a TBP distillation tower reboiler 4 is arranged in parallel on the feed pipe, the top of the TBP distillation tower 5 is connected to the TBP distillation tower top reflux tank 6 through a TBP distillation tower top condenser 12, the bottom of the kerosene distillation tower 8 is connected to the kerosene storage tank 9, the top of the kerosene distillation tower 8 is connected to the kerosene distillation tower top reflux tank 10 through a kerosene distillation tower top condenser 13, the top of the kerosene distillation tower 8 is connected to the light kerosene storage tank 11, and the light kerosene outlet of the kerosene distillation tower 8 is connected to the light kerosene storage tank 11.

[0060] In the above-mentioned contaminated solvent double-tower distillation process system, the feed tank 1 is mainly used to provide the contaminated solvent generated by the spent fuel post-processing process; the falling film reboiler 2 is a heating device, which is mainly used to heat and vaporize the contaminated solvent, and the vaporized steam enters the TBP distillation tower 5, and the distillation residue discharged from the bottom of the separation chamber of the falling film reboiler 2 enters the distillation residue storage tank 3; the distillation residue storage tank 3 is mainly used to store the distillation residue discharged from the bottom of the falling film reboiler 2; the TBP distillation tower reboiler 4 is mainly used to heat and vaporize the liquid condensed in the TBP distillation tower 5 again; the TBP distillation tower 5 is mainly used to separate the TBP fraction and the kerosene fraction; the TBP distillation tower top reflux tank 6 mainly controls the balance of the TBP distillation tower 5 The TBP storage tank 7 is mainly used for storing the TBP fraction separated by the TBP distillation tower 5; the kerosene distillation tower 8 is mainly used for re-distillation of the crude kerosene fraction separated by the TBP distillation tower 5; the kerosene storage tank 9 is mainly used for storing the kerosene fraction separated by the kerosene distillation tower 8; the kerosene distillation tower top reflux tank 10 mainly plays a role in controlling the balance of the kerosene distillation tower 8; the light kerosene storage tank 11 is mainly used for storing the light kerosene fraction separated by the kerosene distillation tower 8; the TBP distillation tower top condenser 12 is mainly used for cooling the TBP fraction separated by the TBP distillation tower 5; the kerosene distillation tower top condenser 13 is mainly used for cooling the light kerosene fraction separated by the kerosene distillation tower 8.

[0061] Feed tank 1 is the input amount, distillation residual liquid storage tank 3, TBP storage tank 7, kerosene storage tank 9, light kerosene storage tank 11 are output amounts, and falling film reboiler 2, TBP distillation tower reboiler 4, TBP distillation tower 5, TBP distillation tower top reflux tank 6, kerosene distillation tower 8, kerosene distillation tower top reflux tank 10 are distillation process amounts, wherein the feed liquid in TBP distillation tower reboiler 4, TBP distillation tower 5 and kerosene distillation tower 8 is a mixture of gas and liquid. By balancing the changes in input, output and distillation process amounts over a period of time, it is confirmed whether the feed liquid is balanced. According to the material balance results, it is verified whether TBP distillation tower 5 and kerosene distillation tower 8 are in gas-liquid balance, material balance and heat balance, and then the process parameters are adjusted, and the accuracy of the instrument indication is further verified. By associating material balance with operation data, the stability of the process production line can be effectively guaranteed. At the same time, the material supervision warehouse is incorporated into the integrated circulation system, and the goal of stabilizing product quality can also be achieved through material balance.

[0062] The operating data of the contaminated solvent distillation facility are divided into three types: original database, material balance model library and evaluation model library; among them:

[0063] The original database is the parameters monitored on the DCS screen during the actual operation process, which can be displayed in real time according to the actual operation of the production line and entered into the original database. Specifically, the original data may include the liquid level data of the feed tank 1, the distillation residue storage tank 3, the TBP storage tank 7, the kerosene storage tank 9, and the light kerosene storage tank 11, as well as the temperature data, pressure data, and liquid level data of the falling film reboiler 2, the TBP distillation tower 5, and the kerosene distillation tower 8.

[0064] The function of the material balance model library is to convert the liquid level signal in the original database into the volume of process liquid through the volume-liquid level curve. The material balance model library also contains the theoretical material balance results (the ideal material balance results of facility design). The actual balance can be compared with the preliminary theoretical balance in the material balance model library. According to the deviation range, the content and output of TBP products can be predicted as the proportion of theoretical deviation.

[0065] Specifically, the material balance model library mainly includes the actual volume data and theoretical volume data of the material. The actual volume data includes the volume change V1 of the dirty solvent in the feed tank 1, the volume change V2 of the distillation residue in the distillation residue storage tank 3, the volume change V3 of the TBP product in the TBP storage tank 7, the volume change V4 of the kerosene product in the kerosene storage tank 9, and the volume change V5 of the light kerosene in the light kerosene storage tank 11. The liquid level-volume function is first obtained based on multiple groups of corresponding liquid level data and volume data, and then the actual volume data of the material is obtained using the liquid level-volume function based on the liquid level data in the original data. The theoretical volume data includes the theoretical volume V2′ of the distillation residue, the theoretical volume V3′ of the TBP product, the theoretical volume V4′ of the kerosene product, and the theoretical volume V5′ of the light kerosene, which can be calculated according to the following formula:

[0066] V2'=V×C%

[0067]

[0068] V5′=V×D%

[0069] In the above formula: V is the treatment amount of the contaminated solvent; A is the TBP content of the contaminated solvent, which is obtained by sampling and analyzing in the feed tank 1; B is the TBP content of the TBP product, which is obtained by sampling and analyzing in the TBP storage tank 7; C is the proportion of residual liquid extraction, which can be calculated by converting it into volume through the liquid level change of the distillation residual liquid storage tank 3; D is the proportion of light kerosene, which can be calculated by converting it into volume through the liquid level change of the light kerosene storage tank 11; ρ1 is the density of kerosene, which is obtained by sampling and analyzing in the kerosene storage tank 9; ρ2 is the density of light kerosene, which is obtained by sampling and analyzing in the light kerosene storage tank 11.

[0070] The input quantity in the material balance model library is the feed part, the distillation process quantity is the falling film reboiler 2, TBP distillation tower 5 and kerosene distillation tower 8 parts, and the output quantity is the product extraction part. The input and output feed liquids are in liquid state, and the volume is directly balanced by the liquid level. The distillation process quantity involves the balance in the distillation tower. The feed liquid is a mixture of gas and liquid. It is necessary to ensure the gas-liquid balance in the distillation tower, and the heat transfer and mass transfer efficiency are stable. The liquid level on the DCS screen is a single reading. The liquid level can be converted into volume according to the type of storage tank. The relationship between the liquid level and volume can be fitted into a univariate multi-function, and the correlation coefficient R after fitting is required. 2 ≥0.99. The initial liquid level and the final liquid level can be read and converted into the volume within a certain period of time according to the fitted function relationship. The present invention matches the volume-liquid level balance with the double tower parameters for verification, and realizes the material volume balance through real-time balance of DCS liquid level signals.

[0071] The evaluation model library is set up with facility operation data and material sampling and analysis data. The evaluation model library is composed of relevant data from the radioactive debugging and trial operation stages. The equipment operation data and material analysis results from the stable stage of product indicators are selected. The relevant data obtained from the material balance library are compared with the evaluation model library. The system analyzes and judges the resulting deviations. Finally, the comparison results formed by the evaluation model library are used to form relevant reports to guide production practice. In addition, the generated data are also entered into the material balance library, and the algorithm is continuously iterated to achieve stable operation of the contaminated solvent distillation facility.

[0072] On the one hand, the evaluation model library forms a facility operation database and a material supervision database based on the previous theoretical simulation and actual operation results, and improves the relevant data based on the actual operation results. On the other hand, the actual results of the original database and the material balance model library are compared with the complete database that has been formed, and relevant reports are formed according to the comparison results. Finally, the temperature, liquid level and pressure indicators in the original database are adjusted to achieve the goal of accurately controlling the key equipment parameters of the distillation facility according to the material balance. Improve the evaluation model library under different working conditions through material balance. Collect the operating data and material data of the distillation tower under different working conditions to supplement the evaluation model library system. When the system operates abnormally, the data model with high overlap in the evaluation model library can be selected to handle the abnormal conditions. At the same time, it can also summarize and balance all data, continuously supplement and improve the database, and further ensure the accuracy of the balance.

[0073] The method of this embodiment designs a three-stage model, which is as follows:

[0074] 1) Liquid level and volume balance of feed tank 1 and product tank:

[0075] In the dirty solvent distillation facility, the feed tank 1 is provided with a liquid level monitoring point, and the liquid level signal is transmitted to the background DCS screen through remote transmission, which is convenient for personnel operation, but the DCS screen does not have a real-time volume conversion relationship, and the volume entering the distillation tower cannot be balanced in real time. Therefore, this embodiment realizes automatic balance of real-time volume changes every hour by adding the liquid level and volume conversion relationship of the raw material storage tank and the product storage tank, and verifies whether the system is balanced according to the volume changes of the incoming and outgoing materials, so as to achieve the purpose of stabilizing product quality and yield.

[0076] 2) According to the residual volumes in the falling film reboiler 2, the TBP distillation tower 5 and the kerosene distillation tower 8, the equilibrium deviations of the TBP distillation tower 5 and the kerosene distillation tower 8 are verified, and equilibrium correction is performed simultaneously:

[0077] After the balance is performed according to the above step 1), the liquid level correction of the falling film reboiler 2, TBP distillation tower 5, kerosene distillation tower 8, and the top reflux tank is added synchronously. The falling film reboiler 2 and the distillation tower are both in a gas-liquid mixed state and are in dynamic equilibrium; when an abnormality occurs, it may cause an increase in the phases in the above equipment. If this part of the material is not taken into account, it will cause the whole system material imbalance. Therefore, this embodiment will synchronously perform liquid level-volume balance on the above equipment, balance the material volume of the above equipment every hour, and further supplement the stable balance of raw material supply and product extraction.

[0078] 3) Construct material balance model:

[0079] This embodiment designs a three-stage model, and converts the liquid level signal into volume, so as to achieve real-time balance of whether the material is conserved and whether the production line is running stably. The first section is the feeding part, the second section is the TBP distillation tower 5 and the kerosene distillation tower 8 part, and the third section is the product extraction part. The first and third sections of the feed liquid are in liquid state, and the balance is directly calculated by converting the liquid level into volume. The second section involves the balance in the distillation tower, and the materials involve gas and liquid. It is necessary to ensure the gas-liquid balance in the distillation tower, and the heat and mass transfer efficiency are stable. The volume-liquid level balance is matched and verified with the double tower parameters, and the DCS signal is used for online real-time balance to achieve the goal of accurately regulating the distillation tower parameters according to the material balance.

[0080] The phase in the feed tank 1 is liquid, and the treatment volume V of the dirty solvent is the volume change of the dirty solvent in the feed tank over a period of time, that is, V=V1. The phases in the distillation residue storage tank 3, TBP storage tank 7, kerosene storage tank 9 and light kerosene storage tank 11 are liquid, and the volume calculated based on the liquid level is also relatively stable. Therefore, it is believed that the volume change V2 of the distillation residue in the distillation residue storage tank, the volume change V3 of the TBP product in the TBP storage tank, the volume change V4 of the kerosene product in the kerosene storage tank, and the volume change V5 of the light kerosene in the light kerosene storage tank can accurately measure the changes in the above storage tanks over a period of time; however, since the falling film reboiler 2, TBP distillation tower 5 and kerosene distillation tower 8 are in a gas-liquid mixed state, the amount of the actual product after distillation is deviated from the theoretical value, which can be reduced by controlling the liquid level of the above equipment to be stable. In addition, the distillation residue and light kerosene are extracted as by-products at a constant ratio, so the volume deviation has little effect and the result is controllable. The volume changes of actual TBP products and kerosene products are more obvious. When the deviation is controlled within ±10%, it is considered that the parameters are normal fluctuations. When the deviation within a unit time exceeds the above range, it is necessary to interlock and adjust the relevant parameters to achieve the goal of adjusting process parameters through material balance.

[0081] For TBP products:

[0082] When -10%≤(V3-V3ˊ) / V3ˊ≤10%, the TBP product extraction is stable and no process parameter adjustment is required;

[0083] When (V3-V3ˊ) / V3ˊ≤-10%, the TBP output is low and the liquid level in the main distillation tower is high, which may cause tower flooding. The output flow rate can be increased through interlocking to control the liquid level to be stable within the normal required range.

[0084] When (V3-V3ˊ) / V3ˊ≥10%, the TBP output is too high and the liquid level in the bottom of the main distillation tower is too low. The output flow can be reduced through interlocking to control the liquid level to be stable within the normal required range.

[0085] For kerosene products:

[0086] When -10%≤(V4-V4ˊ) / V4ˊ≤10%, the kerosene product production is stable and no process parameter adjustment is required;

[0087] When (V4-V4ˊ) / V4ˊ≤-10%, the kerosene production is low or the reflux flow is too large, causing the liquid level of falling film reboiler 2 to continue to rise. Under the condition of ensuring the product is qualified, the kerosene production flow is increased or the reflux flow is reduced to control the liquid level of the reflux tank of the main distillation tower to be stable within the normal requirement range;

[0088] When (V4-V4ˊ) / V4ˊ≥10%, the kerosene production is too high, causing the liquid level in the reflux tank at the top of the main distillation tower or the liquid level in the reboiler in the bottom of the kerosene distillation tower to continue to decrease. The kerosene production flow rate is reduced by interlocking, and the liquid level in the reflux tank of the main distillation tower and the liquid level in the reboiler in the bottom of the kerosene distillation tower are controlled to be stable within the normal requirement range.

[0089] This embodiment can timely grasp the operation dynamics of the distillation facility by real-time balancing of materials, waste liquid and waste gas of the contaminated solvent distillation facility, and provide real-time feedback of abnormal operating conditions that may exist in the double towers during the distillation process through the balancing data, so that the operating personnel can take control measures, realize comprehensive monitoring of the system, and ensure the continuous and stable operation of the contaminated solvent distillation facility of the spent fuel reprocessing plant; in addition, the key control parameters in the contaminated solvent double tower distillation process are compared with each other through the evaluation model library, so as to optimize the operation mode of the distillation facility.

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for automatic material balance of double-tower distillation of polluted solvents, characterized in that: The steps include: S1: Obtain the original data of the materials of the double-tower distillation process of the contaminated solvent and build the original database; S2: Obtain the actual volume data and theoretical volume data of the material based on the original data, and build a material balance model library; S3: Construct an evaluation model library consisting of a facility operation database and a material supervision database to compare, evaluate and adjust the actual volume data of materials with the theoretical volume data, and use the evaluation model library to adjust the process parameters of the double-tower distillation of contaminated solvents.

2. The method for automatic material balance of double-tower distillation of contaminated solvents according to claim 1, characterized in that: The double-tower distillation process system for polluted solvents comprises a feed tank, a falling film reboiler, a TBP distillation tower and a kerosene distillation tower which are arranged in sequence, the bottom of the falling film reboiler is connected to a distillation residue storage tank, the bottom of the TBP distillation tower is connected to the TBP storage tank through a feed pipe, a TBP distillation tower reboiler is arranged in parallel on the feed pipe, the top of the TBP distillation tower is connected to a TBP distillation tower top reflux tank through a TBP distillation tower top condenser, the bottom of the kerosene distillation tower is connected to a kerosene storage tank, and the top of the kerosene distillation tower is connected to a kerosene distillation tower top reflux tank through a kerosene distillation tower top condenser.

3. The method for automatic material balance of double-tower distillation of contaminated solvents according to claim 1, characterized in that: The original data includes DCS monitoring data; Preferably, the original data includes liquid level data of the feed tank, residual liquid storage tank, TBP storage tank, kerosene storage tank, light kerosene storage tank, and temperature data, pressure data and liquid level data of the falling film reboiler, TBP distillation tower, and kerosene distillation tower.

4. The method for automatic material balance of double-tower distillation of contaminated solvents according to claim 1, characterized in that: The actual volume data acquisition method of the material includes: A) obtaining a liquid level-volume function based on a plurality of sets of corresponding liquid level data and volume data; B) Based on the liquid level data in the original data, the actual volume data of the material is obtained using the liquid level-volume function.

5. The method for automatic material balance of double-tower distillation of contaminated solvents according to claim 1, characterized in that: The actual volume data of the materials include the volume change V3 of the TBP product in the TBP storage tank and the volume change V4 of the kerosene product in the kerosene storage tank.

6. The method for automatic material balance of double-tower distillation of contaminated solvents according to claim 1, characterized in that: The theoretical volume of TBP product is obtained by the following formula: Wherein: V3′ is the theoretical volume of TBP product; V is the treatment volume of contaminated solvent; A is the TBP content of contaminated solvent; B is the TBP content of TBP product; C is the proportion of residual liquid production.

7. The method for automatic material balance of double-tower distillation of contaminated solvents according to claim 1, characterized in that: The theoretical volume of kerosene product is obtained by the following formula: Wherein: V4′ is the theoretical volume of kerosene product; V is the treatment volume of contaminated solvent; A is the TBP content of contaminated solvent; ρ1 is the density of kerosene; V3′ is the theoretical volume of TBP product; B is the TBP content of TBP product; C is the proportion of residual liquid production; D is the proportion of light kerosene; ρ2 is the density of light kerosene.

8. The method for automatic material balance of double-tower distillation of contaminated solvents according to claim 6, characterized in that: The actual volume data of the TBP product was compared and evaluated with the theoretical volume data in the following manner, and the process parameters of the double-tower distillation of the contaminated solvent were adjusted as follows based on the evaluation results: When -10%≤(V3-V3′) / V3′≤10%, the TBP product extraction is stable; When (V3-V3′) / V3′≤-10%, the TBP output is low and the liquid level of the main distillation tower is high. The interlock increases the output flow rate and controls the liquid level to be stable within the normal required range. When (V3-V3′) / V3′≥10%, the TBP output is too high and the liquid level in the main distillation tower is too low. The interlock reduces the output flow rate and controls the liquid level to be stable within the normal requirement range.

9. The method for automatic material balance of double-tower distillation of contaminated solvents according to claim 7, characterized in that: The actual volume data of kerosene products were compared and evaluated with the theoretical volume data in the following manner, and the process parameters of the double-tower distillation of the contaminated solvent were adjusted as follows according to the evaluation results: When -10% ≤ (V4-V4ˊ) / V4ˊ ≤ 10%, kerosene product production is stable; When (V4-V4ˊ) / V4ˊ≤-10%, the kerosene production is too low or the reflux flow is too large, and the falling film reboiler liquid level continues to rise, the interlock increases the kerosene production flow or reduces the reflux flow, and controls the main distillation tower reflux tank liquid level to be stable within the normal requirement range; When (V4-V4ˊ) / V4ˊ≥10%, the kerosene production is too high, the liquid level in the reflux tank at the top of the main distillation tower or the liquid level in the reboiler in the bottom of the kerosene distillation tower continues to decrease, and the kerosene production flow is reduced by interlocking to control the liquid level in the reflux tank of the main distillation tower and the liquid level in the reboiler in the bottom of the kerosene distillation tower to be stable within the normal requirement range.

10. The method for automatic material balance of double-tower distillation of contaminated solvents according to claim 1, characterized in that: Based on the previous theoretical simulation and actual operation results, the facility operation database and material supervision database are formed, and the facility operation database and material supervision database are improved according to the actual operation results; the complete data of the double-tower distillation process of contaminated solvents are compared with the facility operation database and the material supervision database, and the temperature, liquid level and pressure in the double-tower distillation process of contaminated solvents are adjusted according to the comparison results.

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