Low-energy-consumption method for transferring volatile solute in solvent

Abstract

The invention relates to a low-energy-consumption method for transferring a volatile solute in a solvent. The method is used for transferring the volatile solute in a high-concentration process material into low-concentration absorption liquid. High-concentration process materials enter the precipitation tower and are subjected to countercurrent stripping by low-concentration recycle gas from the absorption tower, volatile solutes in the high-concentration process materials enter the recycle gas to obtain low-concentration process materials and high-concentration recycle gas, and the stripped high-concentration recycle gas enters the absorption tower through a booster fan and is subjected to countercurrent absorption by low-concentration absorption liquid to obtain high-concentration process materials and high-concentration recycle gas. Volatile solutes in the high-concentration circulating gas are transferred into the absorption liquid, so that high-concentration absorption liquid and low-concentration circulating gas are obtained; the low-concentration circulating gas is circulated back to the precipitation tower to perform steam stripping on the high-concentration process material again; in the process, under the condition that the two towers do not consume heat, the transfer process of the volatile solute is completed by utilizing the replacement effect of water and the volatile solute. Compared with an existing steam stripping evaporation condensation technology, the energy consumption cost can be reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of phase separation, and in particular relates to a method for transferring a volatile solute in a solvent with low energy consumption. Background Art

[0002] Ammonia-containing wastewater refers to wastewater containing high concentrations of ammonia nitrogen. Ammonia nitrogen is a common water pollutant that comes from various industrial processes, agricultural activities, and domestic sewage. High-concentration ammonia nitrogen wastewater causes serious harm to the environment and ecosystem, so treating ammonia-containing wastewater is an important environmental protection task. At present, there are several treatment processes for ammonia-containing wastewater: steam stripping evaporation condensation technology, membrane separation technology, chemical precipitation technology, activated carbon adsorption technology, biodegradation treatment technology, etc. Among the above methods, the steam stripping evaporation condensation technology treatment scheme is the main one. In many chemical processes, it is necessary to absorb volatile solutes through materials, and then volatilize and separate the volatile solutes to achieve the purpose of separation, purification, or concentration increase. In addition to the ammonia mentioned above, many other volatile solutes with similar properties to ammonia also have the problem of how to recover the solutes, but the current mainstream is steam stripping evaporation condensation technology. The stripping evaporation condensation technology is to convert the ammonia in the ammonia wastewater into a mixed gas of ammonia and water by evaporating or steam stripping the ammonia wastewater, separate it from the impurities in the ammonia wastewater, and then convert the ammonia back into ammonia water with higher purity for recycling or sale through condensation, absorption and other processes. This process requires the use of an external heat source to volatilize the volatile components into low-concentration steam. After the low-concentration steam enters the stripping tower for concentration, a higher concentration of volatile component steam is obtained at the stripping tower outlet, and then the volatile components are condensed in the solvent through a spray tower.

[0003] Stripping evaporation condensation technology Figure 1 As shown: the material at the bottom of the stripping tower enters the reboiler, where the energy required for evaporation is provided by an external heat source to evaporate the volatile solute, and then the gas (volatile solute) enters the stripping tower to exchange gas and liquid with the material to increase the concentration, and then is pressurized by the booster fan to enter the spray tower for full condensation absorption with the material, cooled by an external cold source and mixed with the material in the absorption tower to complete the absorption task. Among them, the heat required for the evaporation of the volatile solute is provided by the external heat source of the reboiler, and the heat input into the system is taken away by the cold source of the full condenser. Since both gas evaporation and condensation are latent heat, the energy consumption required for this process is very large.

[0004] Although the above scheme can effectively separate the volatile components from the solvent and convert them into a high-concentration solution with use value, all gases in the process need to be evaporated and condensed, and the evaporation and condensation processes are both high-energy consumption processes. For volatile components with higher economic value, the stripping evaporation and condensation technology can still be used to achieve separation. For some volatile components with lower value, the energy cost of the recovery process is even higher than the value of the volatile components themselves. Therefore, providing a low-energy volatile solute separation technology can create practical benefits. Summary of the invention

[0005] 1. Technical issues to be resolved

[0006] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a low-energy method for transferring volatile solutes in a solvent, which can reduce energy consumption costs compared to the existing steam stripping evaporation condensation technology, and solves the technical problem of high process energy consumption in recovering ammonia solutes in materials containing ammonia solutes by the existing steam stripping evaporation condensation technology.

[0007] (II) Technical solution

[0008] In a first aspect, the present invention provides a method for transferring a volatile solute in a solvent with low energy consumption, which is used to transfer a volatile solute in a high-concentration process material to a low-concentration absorption liquid; the method comprises:

[0009] The high-concentration process material and the low-concentration circulating gas are sent together into a precipitation tower for gas-liquid exchange, and the volatile solute in the high-concentration process material is taken out of the precipitation tower by the low-concentration circulating gas to generate high-concentration circulating gas, and at the same time, the concentration of the volatile solute in the high-concentration process material is reduced to become a low-concentration process material;

[0010] The high-concentration circulating gas and the low-concentration absorption liquid are sent to the absorption tower for gas-liquid exchange. The low-concentration absorption liquid absorbs the volatile solute in the high-concentration circulating gas to produce a high-concentration absorption liquid. Thus, the process of transferring the volatile solute from the high-concentration process material to the low-concentration absorption liquid is realized. The high-concentration absorption liquid is used for further concentration. The concentration of the volatile solute in the high-concentration circulating gas is reduced to become the low-concentration circulating gas, which is returned to the precipitation tower and used again to take the volatile solute in the high-concentration process material out of the precipitation tower.

[0011] The volatile solute is one or more of ammonia, ethanolamine, diethanolamine, ethanol, methanol, and propanol; the high-concentration process material, low-concentration process material, low-concentration absorption liquid, and high-concentration absorption liquid are all aqueous solutions; the concentration of the volatile solute in the high-concentration process material is A1, and the concentration of the volatile solute in the low-concentration process material is A2, then A1>A2; the concentration of the volatile solute in the low-concentration absorption liquid is B1, and the concentration of the volatile solute in the high-concentration absorption liquid is B2, then B2>B1.

[0012] It should be noted that "high concentration" and "low concentration" in this application are relative concepts and have no absolute meaning; if the volatile solute in a process material is to be transferred to the absorption liquid, then the process material is a high-concentration process material, and the absorption liquid is a low-concentration absorption liquid as long as it can absorb the volatile solute again. The concentration of the volatile solute in the low-concentration absorption liquid can be 0 or much lower than the saturation concentration of the volatile solute.

[0013] According to a preferred embodiment of the present invention, the absorption tower or precipitation tower is a plate tower or a packed tower. Preferably, the absorption tower or precipitation tower is an adiabatic process, and by applying insulation measures to the absorption tower or precipitation tower, heat is not transferred to the outside world, and no heat or cold is required from the outside world.

[0014] According to a preferred embodiment of the present invention, the working temperature of the precipitation tower is controlled at -10-110°C, and the working temperature of the absorption tower is controlled at 0-120°C; the operating pressure of the precipitation tower is less than 4.0 MPa absolute pressure, and the operating pressure of the absorption tower is less than 5.0 MPa absolute pressure.

[0015] According to a preferred embodiment of the present invention, the high and low in the high-concentration process material and the low-concentration absorption liquid refer to the concentration of the volatile solute, and do not refer to other substances. The high-concentration process material and the low-concentration absorption liquid are aqueous solutions containing metal salts or inert components, and the pH value is between 2-14.

[0016] Wherein, the metal salt is one or more of sulfate, nitrate, phosphate, pyrophosphate, polyphosphate, perchlorate, acetate, formates, phthalates, and chloride containing potassium, sodium, ammonium, lead, zinc, copper, cadmium, nickel, cobalt, magnesium, calcium, or chromium; the concentration of the metal salt is less than 10.0 mol / L; the inert component is a non-volatile organic matter, the concentration of which is less than 10.0 mol / L, and the organic matter is one or more of non-volatile alcohol, aldehyde, amino acid, aminocarboxylic acid complexing agent, non-amino acid organic acid, organic amine, and organic phosphoric acid, the concentration of which is less than 10.0 mol / L;

[0017] The pH of the high-concentration process material and the low-concentration absorption liquid is adjusted to be between 2 and 14 by using organic base, inorganic base, organic acid and inorganic acid.

[0018] The involatile alcohol in the inert component is one or more of propylene glycol, ethylene glycol, pentaerythritol, furfuryl alcohol, and benzyl alcohol; the involatile aldehyde in the inert component is furfural.

[0019] The low-volatile organic amine in the inert component is ethylenediamine, propylenediamine, hydroxyethylethylenediaminetriacetic acid, triethanolamine, tetraethylenepentamine, triethylenetetramine, ethylenediaminetetraacetic acid, propylenediaminediacetic acid, ethylenediaminediacetic acid, ethylene glycol diethyl ether diaminetetraacetic acid, diethyl ether diaminetetraacetic acid, propylenediaminetetraacetic acid, hydroxyethylethylenediaminetriacetic acid, diethylenetriaminepentaacetic acid, triethylenetetraaminehexaacetic acid, cyclohexanediaminetetraacetic acid, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, asparagine or glutamine.

[0020] The low-volatile organic phosphoric acid in the inert component is hydroxyethylidene diphosphonic acid, aminotrimethylphosphonic acid or diethylenetriaminepentamethylphosphonic acid.

[0021] The non-amino acid organic acid in the inert component is sodium catechol-3,5-disulfonate, 2-aminobenzoic acid-N,N-diacetic acid, acetic acid, taurine, phthalic acid, nicotinic acid, xylenol orange or catechol violet.

[0022] The amino acids in the inert component are one or more of glutamic acid, valine, histidine, aspartic acid, leucine, isoleucine, alanine, proline, serine, phenylalanine, arginine, threonine, glycine, lysine, methionine, ornithine, citrulline, and sarcosine.

[0023] Among the reagents for regulating the pH of the high-concentration process material and the low-concentration absorption liquid, the organic base is one or more of methylamine, ethylamine, ethylenediamine, propylenediamine, and propylamine; the inorganic base is one or more of ammonia, potassium hydroxide, sodium hydroxide, sodium carbonate, potassium carbonate, ammonium carbonate, calcium oxide, and calcium hydroxide; the organic acid is one or more of formic acid, acetic acid, oxalic acid, propionic acid, and citric acid; and the inorganic acid is one or more of sulfuric acid, hydrochloric acid, nitric acid, perchloric acid, and phosphoric acid.

[0024] According to a preferred embodiment of the present invention, the high-concentration process material also contains precipitated crystallized material, and the low-concentration absorption liquid also contains solid material to be dissolved, wherein the solid material is a material containing gypsum components, a material containing calcium carbonate components, or a material containing lead compound components, and the crystallized material is a material containing one or more of gypsum, calcium carbonate, and lead compounds.

[0025] According to a preferred embodiment of the present invention, the method further includes a reboiler; the low-concentration process material enters the reboiler, and under the action of boiling by external heat or / and boiling by reducing the operating pressure, the volatile solute in the low-concentration process material evaporates to produce low-concentration solute steam, and at the same time, the concentration of the volatile solute in the low-concentration process material further decreases to produce an even lower concentration process material, which contains a volatile solute concentration of A3, A2>A3.

[0026] According to a preferred embodiment of the present invention, the method also includes a full condenser; the low-concentration solute vapor produced by the reboiler and the high-concentration absorption liquid produced by the absorption tower enter the full condenser together, and under the action of condensation by an external cold source and / or boiling by increasing the operating pressure, the high-concentration absorption liquid further absorbs the volatile solutes in the low-concentration solute vapor and produces a higher concentration absorption liquid, the volatile solute concentration of which is B3, B3>B2.

[0027] A higher concentration absorption liquid can be obtained through the combined system of a reboiler and a full condenser. The low-concentration process material passes through the reboiler to obtain a process material with a lower volatile solute concentration (lower concentration process material) and a low-concentration solute vapor. The low-concentration solute vapor and the high-concentration absorption liquid (including concentration B2) pass through the full condenser to obtain a higher concentration absorption liquid (including concentration B3). In this way, the transfer rate of volatile solutes from high-concentration process materials to low-concentration absorption liquid is further improved, and the number of theoretical trays of the precipitation tower and absorption tower can be reduced, thereby reducing the operating resistance.

[0028] According to a preferred embodiment of the present invention, the reboiler is one of a kettle reboiler, a siphon reboiler and a flash kettle, and the full condenser is one of a plate absorption tower, a packed tower and a spray tower.

[0029] According to a preferred embodiment of the present invention, the volume ratio of the high-concentration process material to the low-concentration absorption liquid is between 0.0001 and 10000.

[0030] According to a preferred embodiment of the present invention, the low-concentration solute vapor generated by the reboiler evaporating and boiling the low-concentration process material, although the concentration of volatile solutes contained therein is not high, the purity of the volatile solutes is relatively high because it is produced by boiling in the reboiler. Therefore, the low-concentration solute vapor can also enter the absorption tower together with the high-concentration circulating gas generated by the precipitation tower, and be absorbed by the low-concentration absorption liquid; or, the low-concentration solute vapor can also be introduced into the precipitation tower together with the low-concentration circulating gas generated by the absorption tower, for gas-liquid exchange with the high-concentration process material, and the volatile solutes in the high-concentration process material are taken out of the precipitation tower.

[0031] According to a preferred embodiment of the present invention, in order to improve the efficiency of the circulating precipitation and absorption system and the gas-liquid exchange effect, in the precipitation tower, the high-concentration process material enters from the top of the tower and descends, and the low-concentration circulating gas enters from the bottom of the tower and ascends, countercurrently with the high-concentration process material and undergoes a gas-liquid exchange effect; in the absorption tower, the low-concentration absorption liquid enters from the top of the tower and descends, and the high-concentration circulating gas enters from the bottom of the tower and ascends, countercurrently with the low-concentration absorption liquid and undergoes a gas-liquid exchange effect.

[0032] According to a preferred embodiment of the present invention, when the volatile solute is a heat-sensitive substance, in order to reduce the operating temperature of the absorption tower and the precipitation tower to prevent the volatile solute or other components from being decomposed by heat; preferably, an inert gas is mixed into the low-concentration circulating gas or the high-concentration circulating gas to reduce the operating temperature of the precipitation tower and the absorption tower; the inert gas is one or more of nitrogen, argon, air, carbon dioxide, and helium, and the volume content of the inert gas in the low-concentration circulating gas and the high-concentration circulating gas is 0.01-99%. The inert gas is not easily absorbed by the low-concentration absorption liquid, nor does it react with the volatile solute (including direct or indirect reaction), but after the inert gas is mixed into the low-concentration circulating gas or the high-concentration circulating gas, the characteristic that the inert gas can reduce the vapor partial pressure of the volatile solute under a certain pressure can be used to bring out the volatile solute in the high-concentration process material at a lower temperature or promote the high-concentration circulating gas to be absorbed by the low-concentration absorption liquid.

[0033] According to a preferred embodiment of the present invention, the low-concentration circulating gas, high-concentration circulating gas, and low-concentration solute vapor are pressurized and input into the precipitation tower, absorption tower, and total condenser, respectively; the pressurization method is to use a compressor or a fan for pressurization; through the pressurization treatment, the efficiency of transferring volatile solutes from high-concentration process materials to low-concentration absorption liquid can be improved.

[0034] If the impurity content in the absorption liquid is low, the method of the present invention can transfer the volatile solutes in the high-concentration process material with high impurity content to the absorption liquid, thereby improving the purity and process value of the volatile solutes.

[0035] (III) Beneficial effects

[0036] The technical effect of the present invention is that: high-concentration process materials enter the precipitation tower and are countercurrently stripped by low-concentration circulating gas from the absorption tower, and volatile solutes in the high-concentration process materials enter the circulating gas to obtain low-concentration process materials and high-concentration circulating gas; the high-concentration circulating gas after stripping enters the absorption tower through a pressurized fan, and after being countercurrently absorbed by the low-concentration absorption liquid, the volatile solutes in the high-concentration circulating gas are transferred to the absorption liquid to obtain high-concentration absorption liquid and low-concentration circulating gas; the low-concentration circulating gas is circulated back to the precipitation tower to strip the high-concentration process materials again; in this process, the two towers are adiabatic processes, and the replacement effect of water and volatile solutes is used to transfer the volatile solutes from the process materials to the low-concentration absorption liquid without consuming heat in theory.

[0037] Compared with the existing process, most of the volatile solutes are transferred through the low-energy gas circulation process of the precipitation tower and the absorption tower. The heat source input to the reboiler only needs to evaporate a small part of the volatile solutes, so the energy consumption is relatively low. After the precipitation tower and the absorption tower adopt a reasonable tower plate design, only two circulating fans need to be added to realize gas circulation. Under the premise of ensuring the absorption and separation effect, the corresponding tower plate pressure drop can be reduced by optimizing the tower internals design; therefore, the head of the circulating fan is very small and the power consumption is low. Compared with the existing steam stripping-cooling absorption process, the energy consumed in the volatile solute transfer process can be greatly reduced; the energy consumption of treating the same amount of process materials containing volatile solutes is reduced by about 40-70%. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 The present invention is a schematic diagram of the process of preparing ammonia water with higher purity and higher concentration from ammonia-containing wastewater using existing steam stripping evaporation condensation technology.

[0039] Figure 2 The figure is a schematic process diagram of the method for transferring a volatile solute in a solvent with low energy consumption according to the present invention. DETAILED DESCRIPTION

[0040] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below through specific implementation modes in conjunction with the accompanying drawings.

[0041] The design technology principle of the present invention is as follows Figure 2As shown: the high-concentration process material enters the precipitation tower and is countercurrently stripped by the low-concentration circulating gas from the absorption tower. The volatile solutes in the high-concentration process material enter the circulating gas, and low-concentration process material and high-concentration circulating gas are obtained. The high-concentration circulating gas after stripping enters the absorption tower through the pressurized fan, and is countercurrently absorbed by the low-concentration absorption liquid. The volatile solutes in the high-concentration circulating gas are transferred to the absorption liquid, and high-concentration absorption liquid and low-concentration circulating gas are obtained. The low-concentration circulating gas is circulated back to the precipitation tower for the stripping process again. In this process, the two towers are adiabatic processes, and no external heat or cooling is required. The replacement effect of water and volatile solutes is used to transfer volatile solutes from process materials to absorption liquid without consuming heat in theory, thereby completing the transfer of most volatile solutes.

[0042] Theoretically, with only the help of a system consisting of a precipitation tower and an absorption tower, an infinite number of plates can be designed for the precipitation tower and the absorption tower to achieve 100% transfer of volatile solutes. However, in actual production processes, too many theoretical plates will make the volume, cost and gas resistance of the precipitation tower and the absorption tower unacceptable. Therefore, based on the combination of construction cost and operation cost, the low-concentration process material coming out of the precipitation tower still has some volatile solutes, which need to enter the reboiler and evaporate with the help of an external heat source or by using sensible heat (or reducing the operating pressure). After the volatile solutes in the low-concentration process material are reduced to a predetermined concentration, they are discharged from the reboiler, and the low-concentration solute vapor containing volatile solutes is generated. Then, it enters the total condenser through a pressurized fan, mixes with the absorption liquid that has not completed 100% absorption in the absorption tower, that is, the high-concentration absorption liquid, and is absorbed again in whole or in part to produce a higher-concentration absorption liquid. Because the absorption tower and the precipitation tower are two completely opposite processes, the volatile solutes required by the absorption tower are equal to the volatile solutes produced by the precipitation tower, so the full condenser can just absorb the volatile solutes produced by the reboiler.

[0043] like Figure 2 As shown, the system of the present invention is divided into two independent systems, one system is a circulating precipitation-absorption system composed of a precipitation tower and an absorption tower, through internal gas circulation, low-concentration circulating gas is stripped in the precipitation tower to increase the concentration, and high-concentration circulating gas is produced, and the high-concentration circulating gas is absorbed by the low-concentration absorption liquid in the absorption tower, and then becomes low-concentration circulating gas and returns to the precipitation tower, so as to complete the precipitation and absorption tasks (i.e., transfer tasks) of most volatile solutes; the second system is composed of a reboiler and a full condenser, which serves as an auxiliary and supplement to the first system, and the residual volatile solutes that have not been stripped in the high-concentration process material are supplemented by evaporation through an external heat source, and then enter the full condenser through a fan to be cooled, condensed and absorbed by an external cold source.

[0044] Compared with the existing process, most of the volatile solutes are transferred through the low-energy gas circulation process of the precipitation tower and the absorption tower. The heat source input to the reboiler only needs to evaporate a small part of the volatile solutes, so the energy consumption is relatively low. After the precipitation tower and the absorption tower adopt a reasonable tower plate design, only two circulating fans need to be added to realize gas circulation. Under the premise of ensuring the absorption and separation effect, the corresponding tower plate pressure drop can be reduced; therefore, the head of the circulating fan is very small and the power consumption is low. Compared with the existing steam stripping-cooling absorption process, the energy consumed in the volatile solute transfer process can be greatly reduced; the energy consumption of treating the same amount of process materials containing volatile solutes is reduced by about 40-70%.

[0045] In a preferred embodiment of the present invention, for some heat-sensitive materials, by mixing inert gas into high-concentration circulating gas or low-concentration circulating gas, the characteristic of these inert gases that can reduce the vapor partial pressure of volatile solutes under a certain pressure is utilized to reduce the operating temperature of the precipitation tower and the absorption tower, and the high-concentration absorption liquid is kept at a temperature below the boiling point under atmospheric pressure. By utilizing this process characteristic, the low-concentration process material produced by the precipitation tower is flashed in the reboiler by utilizing its own sensible heat or a small amount of external heat source to obtain low-concentration solute vapor, and the low-concentration solute vapor rises in the full condenser by utilizing its own initial temperature and is absorbed by the high-concentration absorption liquid. This further reduces the energy consumption of flash evaporation and fan pressurization. In addition, the heat absorbed by the external solution (cooling medium) of the full condenser can be used to provide a heat source for the reboiler, and the heat medium solution is cooled after the reboiler exchanges heat with the external solution (heat medium), which can be used to provide a cold source for the full condenser. In this way, the entire system can realize the transfer process of volatile solutes from process materials to absorption liquid without even supplementing heat.

[0046] The present invention is further described below in conjunction with preferred embodiments.

[0047] Example 1

[0048] Combination Figure 2 The principle shown in this embodiment is that only a circulating precipitation-absorption system consisting of a precipitation tower and an absorption tower is used to realize the process: the high-concentration process material is a solution containing 7.0 mol / L ammonia, 1 mol / L sodium sulfate, 0.01 mol / L pentaerythritol, 1.5 mol / L nitrilotriacetic acid and adjusted to pH 10.5 with sodium hydroxide. The low-concentration absorption liquid is a solution containing 0.5 mol / L potassium sulfate and adjusted to pH 6.0 with sulfuric acid.

[0049] The absorption tower and the precipitation tower both use floating valve plate towers, and the gas path between the absorption tower and the precipitation tower is pressurized by a circulating fan. The gas path direction is from the top outlet of the absorption tower to the bottom inlet of the precipitation tower; from the top outlet of the precipitation tower to the bottom inlet of the absorption tower. The flow ratio of high-concentration process materials to low-concentration absorption liquid is 1:1, and 50% of the volume of air is added to the low-concentration circulating gas. The operating pressure of the precipitation tower and the absorption tower is 0.1mpa absolute pressure, and the temperature is its gas-liquid equilibrium temperature.

[0050] After the high-concentration process material passes through the precipitation tower, the ammonia concentration of the low-concentration process material obtained by the discharge is 2 mol / L, and after the low-concentration absorption liquid passes through the absorption tower, the ammonia concentration of the high-concentration absorption liquid obtained by the discharge is 5.0 mol / L. In this way, most of the ammonia is transferred from the low-concentration process material to the low-concentration absorption liquid.

[0051] Example 2

[0052] Based on Example 1, this example further combines the second-stage system consisting of a reboiler and a full condenser to realize the process: the low-concentration process material in Example 1 is input into the kettle reboiler, and the high-concentration absorption liquid is sent to the full condenser. The heat source input of the reboiler is controlled so that the evaporation amount of the low-concentration process material is 2%. The low-concentration solute vapor produced in the reboiler enters the full condenser. The cooling water input amount of the full condenser is controlled so that the low-concentration solute vapor produced by the reboiler is completely condensed and absorbed in the full condenser. After evaporation, the ammonia content of the lower-concentration process material produced in the reboiler is 0.5 mol / L, and the ammonia content of the higher-concentration absorption liquid produced in the full condenser is 6.5 mol / L.

[0053] Example 3

[0054] Combination Figure 2 According to the principle shown in the figure, this embodiment uses a circulating precipitation-absorption system consisting of a precipitation tower and an absorption tower and a second-stage system consisting of a reboiler and a full condenser to realize the process:

[0055] The high-concentration process material is a solution containing 5.0 mol / L ethanol, 2 mol / L copper sulfate, 4 mol / L glycine and adjusted to pH 7 with potassium hydroxide. The low-concentration absorption liquid is water. Both the absorption tower and the precipitation tower use large-pore flow plate towers. The gas path between the absorption tower and the precipitation tower is pressurized by a circulating fan. The gas path direction is from the top outlet of the absorption tower to the bottom inlet of the precipitation tower, and from the top outlet of the precipitation tower to the bottom inlet of the absorption tower. The flow ratio of high-concentration process materials to low-concentration absorption liquid is 1:2. 10% nitrogen is mixed into the low-concentration circulating gas and the high-concentration circulating gas. The operating pressure of the precipitation tower and the absorption tower is 0.3 MPa absolute pressure, and the temperature is its gas-liquid equilibrium temperature.

[0056] After the high-concentration process material comes out of the precipitation tower, it becomes a low-concentration process material and enters the kettle reboiler. The low-concentration absorption liquid becomes a high-concentration absorption liquid after passing through the absorption tower and further enters the total condenser. The heat source input of the reboiler is controlled so that its evaporation rate is 5%. Low-concentration solute vapor is generated at the top of the reboiler and enters the total condenser. The cooling water input into the total condenser is controlled so that the low-concentration solute vapor generated in the reboiler is completely condensed and absorbed in the total condenser.

[0057] Finally, after the high-concentration process material passes through the precipitation tower and reboiler, the ethanol concentration of the discharge material is 0.1 mol / L, and after the low-concentration absorption liquid passes through the absorption tower and full condenser, the ammonia concentration of the discharge material is 2.45 mol / L.

[0058] Example 4

[0059] Combination Figure 2 According to the principle shown in the figure, this embodiment uses a circulating precipitation-absorption system consisting of a precipitation tower and an absorption tower and a second-stage system consisting of a reboiler and a full condenser to realize the process:

[0060] The high-concentration process material is a solution containing 0.8 mol / L nickel sulfate, 2 mol / L ammonium sulfate, 0.5 mol / L calcium sulfate, 0.9 mol / L ethylenediaminetetraacetic acid and adjusted with ammonia to a pH value of 9.5. The low-concentration absorption liquid is a solution containing 0.8 mol / L nickel sulfate, 2 mol / L ammonium sulfate, 0.5 mol / L calcium sulfate (solid not dissolved), 0.9 mol / L ethylenediaminetetraacetic acid and adjusted with ammonia to a pH value of 8.5.

[0061] The absorption tower and the precipitation tower both use large-pore flow plate towers. The gas path between the absorption tower and the precipitation tower is pressurized by a circulating fan. The gas path direction is from the top outlet of the absorption tower to the bottom inlet of the precipitation tower, and from the top outlet of the precipitation tower to the bottom inlet of the absorption tower. The flow ratio of high-concentration process materials to low-concentration absorption liquid is 1:1. 70% nitrogen is mixed into the low-concentration circulating gas and the high-concentration circulating gas. The operating pressure of the precipitation tower and the absorption tower is 0.1 MPa absolute pressure, and the temperature is its gas-liquid equilibrium temperature.

[0062] After the high-concentration process material comes out of the precipitation tower, it becomes a low-concentration process material and enters the kettle reboiler. The low-concentration absorption liquid becomes a high-concentration absorption liquid after passing through the absorption tower and further enters the total condenser. The heat source input of the reboiler is controlled so that its evaporation rate is 3%. Low-concentration solute vapor is generated at the top of the reboiler and enters the total condenser. The cooling water input into the total condenser is controlled so that the low-concentration solute vapor generated in the reboiler is completely condensed and absorbed in the total condenser.

[0063] After the high-concentration process material passes through the precipitation tower and reboiler, the pH value of the discharge is 8.5. After the low-concentration absorption liquid passes through the absorption tower and the total condenser, the pH value of the discharge is 9.5.

[0064] 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 by 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 low-energy volatile solute transfer method in a solvent, used to transfer volatile solutes in high-concentration process materials to low-concentration absorption liquid; characterized in that: The method comprises: The high-concentration process material and the low-concentration circulating gas are sent together into a precipitation tower for gas-liquid exchange, and the volatile solute in the high-concentration process material is taken out of the precipitation tower by the low-concentration circulating gas to generate high-concentration circulating gas, and at the same time, the concentration of the volatile solute in the high-concentration process material is reduced to become a low-concentration process material; The high-concentration circulating gas and the low-concentration absorption liquid are sent to the absorption tower for gas-liquid exchange. The low-concentration absorption liquid absorbs the volatile solute in the high-concentration circulating gas to produce a high-concentration absorption liquid. Thus, the process of transferring the volatile solute from the high-concentration process material to the low-concentration absorption liquid is realized. The high-concentration absorption liquid is used for further concentration. The concentration of the volatile solute in the high-concentration circulating gas is reduced to become the low-concentration circulating gas, which is returned to the precipitation tower and used again to take the volatile solute in the high-concentration process material out of the precipitation tower. The volatile solute is one or more of ammonia, ethanolamine, diethanolamine, ethanol, methanol, and propanol; the high-concentration process material, low-concentration process material, low-concentration absorption liquid, and high-concentration absorption liquid are all aqueous solutions; the concentration of the volatile solute in the high-concentration process material is A1, and the concentration of the volatile solute in the low-concentration process material is A2, then A1>A2; the concentration of the volatile solute in the low-concentration absorption liquid is B1, and the concentration of the volatile solute in the high-concentration absorption liquid is B2, then B2>B1.

2. The method according to claim 1, characterized in that The working temperature of the precipitation tower is controlled at -10-110°C, and the working temperature of the absorption tower is controlled at 0-120°C; the operating pressure of the precipitation tower is less than 4.0 MPa absolute pressure, and the operating pressure of the absorption tower is less than 5.0 MPa absolute pressure.

3. The method according to claim 1, characterized in that The high-concentration process material and the low-concentration absorption liquid are aqueous solutions containing metal salts or inert components, with a pH value between 2 and 14; the inert components are organic substances that are difficult to volatilize.

4. The method according to claim 1, characterized in that: The high-concentration process material also contains precipitated crystallized material, and the low-concentration absorption liquid also contains solid material to be dissolved, wherein the solid material is a material containing gypsum, a material containing calcium carbonate or a material containing lead compound, and the crystallized material is a material containing one or more of gypsum, calcium carbonate and lead compounds.

5. The method according to claim 1, characterized in that: The method also includes a reboiler; the low-concentration process material enters the reboiler, and under the action of boiling by external heat or / and boiling by reducing the operating pressure, the volatile solute in the low-concentration process material evaporates to produce low-concentration solute steam, and at the same time, the concentration of the volatile solute in the low-concentration process material further decreases to produce a lower-concentration process material, which contains a volatile solute concentration of A3, A2>A3.

6. The method according to claim 5, characterized in that The method also includes a full condenser; the low-concentration solute vapor produced by the reboiler and the high-concentration absorption liquid produced by the absorption tower enter the full condenser together, and under the action of condensation by an external cold source and / or boiling at an increased operating pressure, the high-concentration absorption liquid further absorbs volatile solutes in the low-concentration solute vapor and produces a higher concentration absorption liquid, wherein the volatile solute concentration is B3, and B3>B2.

7. The method according to claim 1, characterized in that The low-concentration solute vapor generated by evaporating and boiling the low-concentration process material in the reboiler enters the absorption tower together with the high-concentration circulating gas generated in the precipitation tower, and is absorbed by the low-concentration absorption liquid; or, the low-concentration solute vapor and the low-concentration circulating gas generated in the absorption tower are introduced into the precipitation tower together, and are used for gas-liquid exchange with the high-concentration process material, so as to bring the volatile solute in the high-concentration process material out of the precipitation tower.

8. The method according to claim 1, characterized in that In the precipitation tower, high-concentration process materials enter from the top of the tower and flow downward, and the low-concentration circulating gas enters from the bottom of the tower and flows upward, countercurrently with the high-concentration process materials and undergoes gas-liquid exchange; in the absorption tower, low-concentration absorption liquid enters from the top of the tower and flows downward, and the high-concentration circulating gas enters from the bottom of the tower and flows upward, countercurrently with the low-concentration absorption liquid and undergoes gas-liquid exchange.

9. The method according to claim 1, characterized in that: An inert gas is mixed into the low-concentration circulating gas or the high-concentration circulating gas to reduce the operating temperature of the precipitation tower and the absorption tower; the inert gas is one or more of nitrogen, argon, air, carbon dioxide, and helium, and the volume content of the inert gas in the low-concentration circulating gas and the high-concentration circulating gas is 0.01-99%.

10. The method according to claim 1, characterized in that The low-concentration circulating gas, high-concentration circulating gas and low-concentration solute steam are respectively pressurized and input into the precipitation tower, absorption tower and total condenser; the pressurization method is to use a compressor or a fan for pressurization.

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