Fixed bed adsorption column change time and stage design method

Abstract

The application discloses a fixed bed adsorption column replacement time and stage number design method, which comprises the following steps: performing single-pole continuous column adsorption experiment: a certain volume of adsorbent is loaded in an experimental column, a to-be-treated liquid is fed into the experimental column at a selected column feeding rate of liquid, and timing is started; sample analysis of adsorption original liquid and adsorption post-liquid is performed every certain time interval, and single-stage breakthrough time a and optimal separation time b are determined according to the target substance concentration and impurity concentration in the adsorption original liquid and the adsorption post-liquid; stage number c is determined according to the single-stage breakthrough time a and the optimal separation time b, and the stage number c is obtained by rounding up the quotient value of the single-stage breakthrough time a and the optimal separation time b; and a test verification step is performed. The fixed bed adsorption column replacement time and stage number design method can obtain the stage number and the column replacement time through a small test, is convenient and reliable, can make the stage number and the column replacement time design have foresight, can avoid cost waste caused by too many stage numbers, and does not need to rely on a final-stage concentration detection system feedback to determine column replacement, thereby saving equipment investment.

Description

Technical Field

[0001] This invention relates to the field of fixed-bed adsorption separation technology, and in particular to a method for designing column replacement time and number of stages in fixed-bed adsorption. Background Technology

[0002] Fixed-bed adsorption separation involves loading a certain amount of adsorbent into a column-type device. The liquid phase containing a specific concentration of the target analyte is introduced from one end of the column, passes through the adsorbent bed, and exits from the other end. As the liquid phase passes through the adsorbent bed, the target analyte undergoes physical and / or chemical interactions with the functional groups of the adsorbent, transferring from the liquid phase to the adsorbent. Impurities, however, remain largely in the liquid phase, thus achieving separation. Fixed-bed adsorption has broad application prospects in liquid system purification and target analyte extraction. Engineering designs typically employ multi-stage series adsorption, switching valves after a certain time interval to change the inlet of the liquid to be treated from stage 1 to stage 2, and simultaneously changing the outlet from stage x to stage x+1. This ensures that the target analyte concentration in the final stage outlet liquid phase remains below the design target. However, the engineering design phase requires designing an appropriate number of stages and the valve switching interval (column replacement time) to guide equipment procurement and process control. Currently, in fixed-bed adsorption applications, the number of stages is generally set based on experience, and the column replacement time is determined by feedback from the effluent concentration detection system, lacking design foresight. Summary of the Invention

[0003] The present invention aims to at least partially solve one of the technical problems in the related art.

[0004] Therefore, embodiments of the present invention propose a method for designing column replacement time and number of stages in fixed-bed adsorption. This method can be used for engineering scheme preparation and provides a reference for engineering scheme fabrication.

[0005] This invention proposes a method for designing column switching time and number of stages in fixed-bed adsorption, comprising the following steps:

[0006] A single-stage continuous column adsorption experiment was conducted: a certain volume of adsorbent was loaded into the experimental column, and the liquid to be treated was introduced at the selected feed rate, and the timing was started; samples were taken at regular intervals to analyze the original adsorption solution and the liquid after adsorption, and the single-stage breakthrough time a and the optimal separation time b were determined based on the concentration of the target substance and the concentration of impurities in the original adsorption solution and the liquid after adsorption.

[0007] The number of stages c is determined based on the single-stage breakthrough time a and the optimal separation time b. The number of stages c is obtained by rounding up the quotient of the single-stage breakthrough time a and the optimal separation time b.

[0008] In some embodiments, the single-stage breakthrough time 'a' is the time when the concentration of the target substance in the adsorbed liquid first exceeds the designed concentration of the target substance.

[0009] Experimental verification steps.

[0010] In some embodiments, the optimal separation time b is the time when the molar ratio of the main impurity to the target analyte is at its minimum or when the molar ratios of multiple impurities to the target analyte all meet the design value for the molar ratio of the impurity to the target analyte.

[0011] In some embodiments, the amount of impurities and target substances on the adsorbent is calculated using the difference method and the molar ratio is obtained by conversion.

[0012] In some embodiments, the aspect ratio of the adsorbent after filling is close to the aspect ratio required for the enlarged design.

[0013] In some embodiments, the adsorption stock solution is placed in a constant temperature container, and the stability of the adsorption stock solution is determined based on the concentration of the target substance and the concentration of impurities in the adsorption stock solution.

[0014] In some embodiments, the feasibility of the adsorption column replacement time and number of stages is verified through the experimental verification steps.

[0015] In some embodiments, the experimental verification step includes the following steps:

[0016] Prepare a c+1 stage experimental column, with c stages in series adsorption, and use the single-stage breakthrough time 'a' as the column replacement time for column replacement.

[0017] Before each column change, a sample of the final stage effluent was taken to analyze the concentration of the target analyte and compare it with the designed concentration of the target analyte.

[0018] After column replacement, the adsorbent in the original first column is taken out as the adsorbent after adsorption. The number of column replacements is n. After n column replacements, the amount of impurities and target substances on the adsorbent is calculated by the difference method, and the molar ratio of impurities to target substances is obtained by conversion and compared with the designed value of the molar ratio of impurities to target substances.

[0019] In some embodiments, the number of column replacements n ≥ 2.

[0020] In some embodiments, the experimental verification step further includes: taking a sample of the adsorbent after adsorption, performing complete desorption with high acid, analyzing the concentration of the target substance and impurities in the desorption solution, back-calculating the molar ratio of impurities to target substances on the adsorbent, and comparing it with the designed molar ratio of impurities to target substances.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] The fixed-bed adsorption column replacement time and number of stages design method of this invention can obtain the number of stages and column replacement time through small-scale experiments, which is convenient and reliable; it makes the design of the number of stages and column replacement time forward-looking, and can avoid the cost waste caused by too many stages; it does not require the feedback of the final stage concentration detection system to determine the column replacement, thus saving equipment investment. Attached Figure Description

[0023] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0024] Figure 1 This is a flowchart of the design method for fixed-bed adsorption column replacement time and number of stages in this invention. Detailed Implementation

[0025] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0026] The following reference Figure 1 This invention provides a detailed description of the design method for fixed-bed adsorption column replacement time and number of stages proposed in embodiments of the present invention.

[0027] An adsorption process was designed for a certain solution. The main components of the solution to be treated are shown in Table 1, where nickel is the target compound. The molar ratios are Mn / Ni≈8 and Mg / Ni≈53. The design objectives are: Ni < 0.01 g / L in the post-adsorption solution; and the molar ratios of Mn / Ni and Mg / Ni in the adsorbent after adsorption < 4 and < 4.

[0028] Table 1. Main metal content in the solution to be treated (g / L)

[0029] Ni Mg Mn 0.24 5.25 1.87

[0030] 1. Single-stage continuous column adsorption experiment: 120 ml of nickel extraction resin was packed into the experimental column, and the solution to be treated was passed through at a rate of 10 BV / h, with timing started simultaneously. Samples of the stock solution and the post-adsorption solution were taken every 1 hour to analyze the concentrations of Ni, Mn, and Mg in the post-adsorption solution. The results are shown in Table 2. Initially, the concentration of the target analyte in the stock solution was the same as that in the solution to be treated. However, because some solutions to be treated were not at room temperature, the stock solution needed to be maintained at a certain temperature during the experiment. In some cases, a small amount of precipitate of the target analyte may have been present, causing a decrease in the concentration of the stock solution. The stock solution was placed in a constant-temperature container, and its stability was determined based on the concentrations of the target analyte and impurities. The temperature during the experiment was the same as that of the solution to be treated to ensure the stability of the stock solution, i.e., the concentration of the target analyte remained essentially constant.

[0031] Table 2. Concentrations of major elements in the post-adsorption solution (g / L)

[0032] Column passage time / h Ni Mg Mn 1 0.00008 4.08 0.2748 2 0.001423 6.3004 1.3881 3 0.00591 6.1616 1.9986 4 0.03104 5.9696 2.2076 5 0.05525 5.8266 2.2702 6 0.07786 5.4776 2.1194 7 0.09171 5.2232 2.0646 8 0.10604 5.2892 2.0806 9 0.12493 5.9704 2.3396 10 0.13375 5.488 2.1312

[0033] As shown in Table 2, the Ni concentration in the adsorbent solution can reach the design target after 3 hours. The single-stage breakthrough time 'a' is denoted as 3 hours, which is the column replacement time. The amount of impurities and target substances on the adsorbent is calculated by the difference method and converted into molar ratios. The results are shown in Table 3.

[0034] Table 3. Molar ratios of Mn / Ni and Mg / Ni on nickel-extracting resin obtained by the difference method

[0035] Column passage time / h Mg / Ni Mn / Ni 1 18.506 8.548 2 7.326 6.081 3 4.119 4.384 4 3.082 3.392 5 2.787 2.764 6 3.273 2.487 7 4.108 2.333 8 4.721 2.219 9 4.923 2.063 10 5.758 2.060

[0036] According to Table 3, the molar ratios of Mn / Ni and Mg / Ni are both below 4 for 4-6 hours, which meets the design requirements. The average value of 5 hours is taken as the optimal separation time b.

[0037] 2. The single-level breakthrough time 'a' and the optimal separation time 'b' determine the level 'c'. The level 'c' is obtained by rounding up the quotient of the single-level breakthrough time 'a' and the optimal separation time 'b'. The quotient of the single-level breakthrough time 'a' and the optimal separation time 'b' is: b ÷ a = 5 ÷ 3 ≈ 1.67, which is rounded up to 2, meaning the level 'c' is 2.

[0038] 3. Conduct experimental verification: Prepare a c+1=3 stage experimental column, with 2 stages of tandem adsorption and 1 stage for backup column replacement. Column replacement is performed every 3 hours. Before each column replacement, a sample of the final stage effluent is taken and the concentrations of Ni, Mn, and Mg are analyzed. The results are shown in Table 4.

[0039] Table 4. Concentrations of major elements in the liquid after adsorption (g / L) as verified by experiments

[0040] Column passage time / h Ni Mg Mn 3 0.00586 5.034 1.721 6 0.0062 5.083 1.726 9 0.0068 5.099 1.728 12 0.0074 5.114 1.729 15 0.0076 5.117 1.733 18 0.0075 5.124 1.735 21 0.0079 5.129 1.737 24 0.0084 5.132 1.734 27 0.0086 5.135 1.732 30 0.0088 5.138 1.749

[0041] As shown in Table 4, the Ni concentration in the effluent was all <0.01 g / L, reaching the designed concentration of the target analyte. The adsorption amounts of Ni, Mn, and Mg on the resin were calculated using the difference method, and the molar ratios are shown in Table 5.

[0042] Table 5. Experimental verification of the Mn / Ni and Mg / Ni molar ratios on nickel-extracting resin obtained by the difference method.

[0043] Column passage time / h Mg / Ni Mn / Ni 3 2.228 0.668 6 1.725 0.646 9 1.564 0.639 12 1.412 0.636 15 1.382 0.619 18 1.309 0.609 21 1.259 0.601 24 1.230 0.616 27 1.200 0.626 30 1.170 0.549

[0044] After adsorption, 50 ml of the resin was taken and mixed with 1 L of sulfuric acid with a concentration of 150 g / L until equilibrium was reached. The concentrations of Ni, Mn, and Mg in the desorption solution were measured, and the molar ratios of the resin after adsorption were calculated, as shown in Table 6.

[0045] Table 6. Experimental verification of the Mn / Ni and Mg / Ni molar ratios on the nickel extraction resin obtained by the desorption method.

[0046] Mg / Ni Mn / Ni 1.449 0.621

[0047] As shown in Tables 5 and 6, the results of both the difference method and the desorption method verify that the molar ratios Mn / Ni < 4 and Mg / Ni < 4 on the resin after adsorption, which meet the design values ​​for the molar ratio of impurities to target substances.

[0048] The fixed-bed adsorption column replacement time and number of stages design method of the present invention can be obtained through relevant parameters of small-scale experiments, which is convenient and reliable; it makes the design of the number of stages and column replacement time forward-looking, and can avoid the cost waste caused by too many stages; it does not require feedback from the final stage concentration detection system to determine column replacement, thus saving equipment investment.

[0049] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms may refer to different embodiments or examples. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0050] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0051] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for designing column switching time and number of stages in fixed-bed adsorption, characterized in that, Includes the following steps: A single-stage continuous column adsorption experiment was conducted: a certain volume of adsorbent was loaded into the experimental column, and the solution to be treated was introduced at a selected feed rate, and timing was started; samples were taken at regular intervals to analyze the adsorption stock solution and the post-adsorption solution. The single-stage breakthrough time 'a' and the optimal separation time 'b' were determined based on the concentrations of the target analyte and impurities in the adsorption stock solution and the post-adsorption solution. The single-stage breakthrough time 'a' is the time when the concentration of the target analyte in the post-adsorption solution first exceeds the designed concentration of the target analyte, and the optimal separation time 'b' is the time when the molar ratio of the main impurity to the target analyte is at its minimum or when the molar ratios of multiple impurities to the target analyte all meet the designed molar ratio values ​​of the impurities to the target analyte. The number of stages c is determined based on the single-stage breakthrough time a and the optimal separation time b, wherein the number of stages c is obtained by rounding up the quotient of the single-stage breakthrough time a and the optimal separation time b. Experimental verification steps.

2. The method as described in claim 1, characterized in that, The molar ratio is obtained by calculating the amount of impurities and target substances on the adsorbent using the difference method and converting them.

3. The method as described in claim 1, characterized in that, The aspect ratio of the adsorbent after filling is close to the aspect ratio required for the enlarged design.

4. The method as described in claim 1, characterized in that, The adsorption stock solution is placed in a constant temperature container, and the stability of the adsorption stock solution is determined based on the concentration of the target substance and the concentration of impurities in the adsorption stock solution.

5. The method as described in claim 1, characterized in that, The feasibility of the adsorption column replacement time and number of stages was verified through the experimental verification steps.

6. The method as described in claim 5, characterized in that, The experimental verification steps include the following steps: Prepare a c+1 stage experimental column, with c stages in series adsorption, and use the single-stage breakthrough time 'a' as the column replacement time for column replacement. Before each column change, a sample of the final stage effluent was taken to analyze the concentration of the target analyte and compare it with the designed concentration of the target analyte. After column replacement, the adsorbent in the original first column is taken out as the adsorbent after adsorption. The number of column replacements is n. After n column replacements, the amount of impurities and target substances on the adsorbent is calculated by the difference method, and the molar ratio of impurities to target substances is obtained by conversion and compared with the designed value of the molar ratio of impurities to target substances.

7. The method as described in claim 6, characterized in that, The number of column replacements, n, is ≥ 2.

8. The method as described in claim 6, characterized in that, The experimental verification steps also include: taking samples of the adsorbent after adsorption, performing complete desorption with high acid, analyzing the concentrations of the target substance and impurities in the desorption solution, back-calculating the molar ratio of impurities to target substances on the adsorbent, and comparing it with the designed molar ratio of impurities to target substances.

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