CN112723312A - Method for purifying hydrogen chloride by low-concentration impurity-containing dilute hydrochloric acid - Google Patents
Method for purifying hydrogen chloride by low-concentration impurity-containing dilute hydrochloric acid Download PDFInfo
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- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 title claims abstract description 181
- 238000000034 method Methods 0.000 title claims abstract description 84
- 239000012535 impurity Substances 0.000 title claims abstract description 61
- 229910000041 hydrogen chloride Inorganic materials 0.000 title claims abstract description 44
- IXCSERBJSXMMFS-UHFFFAOYSA-N hydrogen chloride Substances Cl.Cl IXCSERBJSXMMFS-UHFFFAOYSA-N 0.000 title claims abstract description 44
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims abstract description 117
- 239000001110 calcium chloride Substances 0.000 claims abstract description 73
- 229910001628 calcium chloride Inorganic materials 0.000 claims abstract description 73
- UXVMQQNJUSDDNG-UHFFFAOYSA-L Calcium chloride Chemical compound [Cl-].[Cl-].[Ca+2] UXVMQQNJUSDDNG-UHFFFAOYSA-L 0.000 claims abstract description 72
- 238000000746 purification Methods 0.000 claims abstract description 65
- 238000009835 boiling Methods 0.000 claims abstract description 25
- 238000004519 manufacturing process Methods 0.000 claims abstract description 12
- 239000000126 substance Substances 0.000 claims abstract description 11
- 239000002994 raw material Substances 0.000 claims description 20
- 238000003795 desorption Methods 0.000 claims description 18
- 238000001035 drying Methods 0.000 claims description 18
- 239000007789 gas Substances 0.000 claims description 15
- 239000006227 byproduct Substances 0.000 claims description 10
- 238000001704 evaporation Methods 0.000 claims description 9
- 230000008020 evaporation Effects 0.000 claims description 9
- 239000002808 molecular sieve Substances 0.000 claims description 9
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 claims description 9
- 238000007738 vacuum evaporation Methods 0.000 claims description 9
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 7
- 238000002156 mixing Methods 0.000 claims description 6
- 239000000575 pesticide Substances 0.000 claims description 4
- FECNOIODIVNEKI-UHFFFAOYSA-N 2-[(2-aminobenzoyl)amino]benzoic acid Chemical class NC1=CC=CC=C1C(=O)NC1=CC=CC=C1C(O)=O FECNOIODIVNEKI-UHFFFAOYSA-N 0.000 claims description 3
- 150000001298 alcohols Chemical class 0.000 claims description 3
- 150000001299 aldehydes Chemical class 0.000 claims description 3
- 150000002170 ethers Chemical class 0.000 claims description 3
- 238000004821 distillation Methods 0.000 description 4
- 238000011161 development Methods 0.000 description 3
- 238000000605 extraction Methods 0.000 description 3
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 2
- 239000003513 alkali Substances 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- 239000000460 chlorine Substances 0.000 description 2
- 229910052801 chlorine Inorganic materials 0.000 description 2
- 238000004891 communication Methods 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 239000004800 polyvinyl chloride Substances 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 238000010306 acid treatment Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000029087 digestion Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- 238000005187 foaming Methods 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 238000011031 large-scale manufacturing process Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 150000002894 organic compounds Chemical class 0.000 description 1
- 229920002635 polyurethane Polymers 0.000 description 1
- 239000004814 polyurethane Substances 0.000 description 1
- 229920000915 polyvinyl chloride Polymers 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 238000001577 simple distillation Methods 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B7/00—Halogens; Halogen acids
- C01B7/01—Chlorine; Hydrogen chloride
- C01B7/07—Purification ; Separation
- C01B7/0706—Purification ; Separation of hydrogen chloride
- C01B7/0712—Purification ; Separation of hydrogen chloride by distillation
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B7/00—Halogens; Halogen acids
- C01B7/01—Chlorine; Hydrogen chloride
- C01B7/07—Purification ; Separation
- C01B7/0706—Purification ; Separation of hydrogen chloride
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B7/00—Halogens; Halogen acids
- C01B7/01—Chlorine; Hydrogen chloride
- C01B7/07—Purification ; Separation
- C01B7/0706—Purification ; Separation of hydrogen chloride
- C01B7/0718—Purification ; Separation of hydrogen chloride by adsorption
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Vaporization, Distillation, Condensation, Sublimation, And Cold Traps (AREA)
Abstract
The invention relates to a method for purifying hydrogen chloride by using low-concentration dilute hydrochloric acid containing impurities, which comprises the following steps: (1) detecting the components of the impurities, and if the impurities contain substances which react with calcium chloride, classifying a differential pressure method purification process and a sulfuric acid method purification process as alternative purification processes; if the impurities do not contain substances which react with calcium chloride, a differential pressure method purification process, a calcium chloride method purification process and a sulfuric acid method purification process are listed as alternative purification processes; (2) further analyzing the boiling point range of the components in the impurities, and selecting a pressure difference method for purification if the boiling point of the main component is lower than 100 ℃; if the boiling point of the main component is greater than 100 ℃, one of the alternative purification processes is selected for purification from the other processes excluding the differential pressure purification process. The invention adopts different purification processes according to different components and boiling point ranges of impurities in the dilute hydrochloric acid, and the manufacturing cost, the operation cost and the purification efficiency of the equipment are optimal.
Description
Technical Field
The invention belongs to the technical field of byproduct hydrochloric acid treatment, and particularly relates to a method for purifying hydrogen chloride from low-concentration impurity-containing dilute hydrochloric acid.
Background
In recent years, with the development of large-scale production expansion of MDI, TDI and other chlorine-related products and the development of chlor-alkali industry, the yield of byproduct hydrochloric acid is continuously increased. Because the byproduct hydrochloric acid contains a certain amount of impurities, the application range of the byproduct hydrochloric acid is limited, the price is low, the sale is difficult, the sale of the dilute hydrochloric acid is more difficult, and the normal operation of a production device is restricted. The environmental pollution and the resource waste are caused. The problem of digestion and utilization of a large amount of byproduct hydrochloric acid becomes a common problem restricting the development of a plurality of industries such as chlor-alkali, polyurethane, pesticide, pharmaceutical chemicals and the like. Polyvinyl chloride (PVC) and other production enterprises which take hydrogen chloride as a raw material also synthesize the hydrogen chloride by consuming a large amount of hydrogen and chlorine resources to meet the production requirements. The hydrogen chloride is prepared by desorbing the byproduct hydrochloric acid and is recycled to PVC and other production devices, so that the byproduct hydrochloric acid can be recycled, the production cost of enterprises can be effectively reduced, and the economic benefit is improved.
As is well known, HCl and H2The diluted hydrochloric acid formed by O has high boiling point azeotrope (i.e. the boiling point of the diluted hydrochloric acid is higher than that of pure H)2O and HCl), whose constant boiling point and constant boiling composition vary with pressure. Therefore, dilute hydrochloric acid is treated to react HCl with H2O is split and is not feasible with simple distillation or stripping methods. At present, the industrialized dilute hydrochloric acid full resolution method mainly comprises the following steps:
1. calcium chloride process
CaCl2The aqueous solution is extracted to break the azeotropic point to recover HCl, i.e. calcium chloride is added into dilute hydrochloric acid to break the limit of the azeotropic point, and hydrogen chloride is separated out. The essence of the method is that the method is added with salt for extraction, and the method is formed by combining a salt-added extraction stripping tower and a water flash tower, and the hydrochloric acid contains sulfate radicals or contains macromolecular organic matters which can cause difficult operation; since both towers need to be heated and evaporated, the steam consumption is high, and about 10.5 tons of steam is consumed for each ton of HCl (100%) analyzed and recovered by 20% diluted hydrochloric acid.
2. Pressure swing distillation method (or called pressure difference method)
The basic principle of pressure swing distillation for azeotropic HCl recovery is that the composition of constant boiling hydrochloric acid changes with pressure, and the relative ratio isIn H2O and HCl, constant boiling hydrochloric acid is always a feature of high boiling point component, thereby achieving the purpose of making H2The purpose of separating O and HCl.
CaCl with analytical technical adaptability ratio of pressure swing distillation diluted hydrochloric acid2The aqueous solution extraction method is good in azeotrope breaking method and insensitive to most of impurities in hydrochloric acid, but the acid cannot contain macromolecular organic matters, so that liquid foaming can be caused, and the mass transfer of the filler is damaged. The pressure swing distillation azeotropic breaking process is a typical high-energy consumption process, and about 14 tons of steam is consumed for each ton of HCl (converted to 100%) by resolving and recovering 20% dilute hydrochloric acid.
In the prior art, the concentration of dilute hydrochloric acid used for treatment is generally more than 18 percent, and the analysis of components is not generally involved before the treatment is carried out by selecting a process, so that the manufacturing cost and the running cost of equipment are increased, and the treatment effect is not ideal.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention provides a method for purifying hydrogen chloride by using low-concentration impurity-containing dilute hydrochloric acid which can be used for treating dilute hydrochloric acid with the mass fraction of 4-15%.
The technical scheme adopted by the invention is as follows:
a method for purifying hydrogen chloride by using low-concentration dilute hydrochloric acid containing impurities comprises the following steps:
(1) detecting the components of the impurities, and if the impurities contain substances which react with calcium chloride, classifying a differential pressure method purification process and a sulfuric acid method purification process as alternative purification processes; if the impurities do not contain substances which react with calcium chloride, a differential pressure method purification process, a calcium chloride method purification process and a sulfuric acid method purification process are listed as alternative purification processes;
(2) further analyzing the boiling point range of the components in the impurities, and selecting a pressure difference method for purification if the boiling point of the main component is lower than 100 ℃; if the boiling point of the main component is more than 100 ℃, selecting one of other processes for purifying, wherein the other processes are the alternative purifying processes except the differential pressure method purifying process;
the differential pressure purification process comprises the following steps: the method comprises the following steps of (1) carrying out positive-pressure evaporation, rectification and concentration on hydrochloric acid containing impurities with the mass fraction of 4-15% by using a positive-pressure rectification tower, taking evaporated steam containing impurities as a heat source for vacuum evaporation, rectification and concentration in a vacuum concentration tower, and increasing the concentration of the hydrochloric acid to 22-23% by using the vacuum concentration tower; sending 22-23% hydrochloric acid to a positive pressure desorption tower, producing hydrogen chloride gas at the tower top, and obtaining hydrochloric acid with the concentration of 15.6-19.5% at the tower bottom; returning 15.6-19.5% hydrochloric acid to the previous working procedure for concentration;
the calcium chloride method purification process comprises the following steps: 4-15% of hydrochloric acid containing impurities is subjected to positive pressure evaporation, rectification and concentration through a positive pressure rectification tower, the evaporated steam containing impurities is used as a heat source for vacuum evaporation, rectification and concentration through a vacuum concentration tower, and the concentration of the hydrochloric acid is increased to 22-23% through the vacuum concentration tower; sending 22-23% hydrochloric acid to a calcium chloride analysis tower, producing hydrogen chloride gas at the tower top, sending dilute calcium chloride from the tower bottom to a calcium chloride concentration tower, mixing the concentrated calcium chloride with 22-23% hydrochloric acid, entering the calcium chloride analysis tower, and producing hydrogen chloride gas;
the sulfuric acid method purification process comprises the following steps: 4-15% of hydrochloric acid containing impurities is subjected to positive pressure evaporation, rectification and concentration through a positive pressure rectification tower, the evaporated steam containing impurities is used as a heat source for vacuum evaporation, rectification and concentration through a vacuum concentration tower, and the concentration of the hydrochloric acid is increased to 22-23% through the vacuum concentration tower; and (3) sending the 22-23% hydrochloric acid to a sulfuric acid analysis tower, producing hydrogen chloride gas at the tower top, sending the dilute sulfuric acid at the tower bottom to a dilute sulfuric acid vacuum concentration system, mixing the concentrated sulfuric acid with the 22-23% hydrochloric acid, entering the sulfuric acid analysis tower, and producing the hydrogen chloride gas.
Preferably, the hydrochloric acid containing impurities comes from byproducts in the production of pharmacy, pesticides and dye intermediates.
Preferably, the impurities are low boiling point organic compounds including alcohols, ethers, and aldehydes.
Preferably, the device adopted by the pressure-difference purification process comprises a raw material tank, a positive-pressure rectifying tower, a vacuum concentrating tower and a positive-pressure analysis tower which are sequentially communicated, wherein the raw material tank is communicated with the positive-pressure rectifying tower through a first preheater and a second preheater, the lower part of the positive-pressure rectifying tower is communicated with a first reboiler, the first reboiler is communicated with a steam pipeline, the top part of the positive-pressure rectifying tower is communicated with the lower part of the vacuum concentrating tower through a second reboiler, the top part of the vacuum concentrating tower is communicated with a first condenser, and the first condenser is communicated with a vacuum system; the top of the positive pressure analysis tower is sequentially communicated with a second condenser and a third condenser, the lower part of the third condenser is respectively communicated with a sulfuric acid drying system and a molecular sieve drying system, the lower part of the positive pressure analysis tower is communicated with a third reboiler, and the bottom of the positive pressure analysis tower is communicated with the upper part of a vacuum concentration tower.
Preferably, the first reboiler is in communication with the first preheater and the third reboiler is in communication with the second preheater; the bottom of the first condenser is communicated with a condensed water collecting device, and the bottoms of the second condenser and the third condenser are respectively communicated with the upper part of the positive pressure desorption tower.
Preferably, the device adopted by the calcium chloride method purification process comprises a raw material tank, a positive pressure rectifying tower, a vacuum concentrating tower, a calcium chloride analysis tower and a calcium chloride concentrating tower which are sequentially communicated, wherein the raw material tank is communicated with the positive pressure rectifying tower through a first preheater and a second preheater, the lower part of the positive pressure rectifying tower is communicated with a first reboiler, the first reboiler is communicated with a steam pipeline, the top part of the positive pressure rectifying tower is communicated with the lower part of the vacuum concentrating tower through a second reboiler, the top part of the vacuum concentrating tower is communicated with a first condenser, and the first condenser is communicated with a vacuum system; the top of the calcium chloride desorption tower is sequentially communicated with a second condenser and a third condenser, the lower part of the third condenser is respectively communicated with a sulfuric acid drying system and a molecular sieve drying system, and the lower part of the calcium chloride desorption tower is communicated with a third reboiler; the top of the calcium chloride concentration tower is communicated with a fourth condenser, the lower part of the calcium chloride concentration tower is communicated with a fourth reboiler, and the bottom of the calcium chloride concentration tower is communicated with the upper part of a calcium chloride analysis tower.
Preferably, the bottoms of the second condenser and the third condenser are respectively communicated with the upper part of the calcium chloride analysis tower, and the bottom of the calcium chloride concentration tower is communicated with the upper part of the calcium chloride analysis tower through a circulating pump; the bottom of the fourth condenser is communicated with a calcium chloride concentrated condensate water collector.
Preferably, the device adopted by the sulfuric acid method purification process comprises a raw material tank, a positive pressure rectifying tower, a vacuum concentration tower, a sulfuric acid analysis tower and a dilute sulfuric acid vacuum concentration system which are sequentially communicated, wherein the raw material tank is communicated with the positive pressure rectifying tower through a preheater, the lower part of the positive pressure rectifying tower is communicated with a first reboiler, the top part of the positive pressure rectifying tower is communicated with the lower part of the vacuum concentration tower through a second reboiler, and the top part of the vacuum concentration tower is communicated with a first condenser; the top of the sulfuric acid analysis tower is sequentially communicated with a second condenser and a third condenser, the lower part of the third condenser is respectively communicated with a sulfuric acid drying system and a molecular sieve drying system, and the lower part of the sulfuric acid analysis tower is communicated with a third reboiler; the dilute sulfuric acid vacuum concentration system is also communicated with the upper part of the sulfuric acid analysis tower.
Preferably, the preheater comprises a first preheater and a second preheater which are communicated in sequence, the second preheater is communicated with the upper part of the positive pressure rectifying tower, the first reboiler is communicated with the first preheater, and the third reboiler is communicated with the second preheater; the bottoms of the second condenser and the third condenser are respectively communicated with the upper part of the sulfuric acid analysis tower.
The invention adopts different purification processes according to different components and boiling point ranges of impurities in the dilute hydrochloric acid, and the manufacturing cost, the operation cost and the purification efficiency of the equipment are optimal.
Drawings
FIG. 1 is a schematic view of the structure of the apparatus used in the purification process of the present invention by differential pressure method;
FIG. 2 is a schematic view of the structure of the apparatus used in the purification process of the present invention by calcium chloride method;
FIG. 3 is a schematic view of the structure of the device used in the sulfuric acid purification process of the present invention.
Detailed Description
The invention is further illustrated by the following examples, without limiting the scope of the invention.
The raw material to be treated is dilute hydrochloric acid with the mass fraction of 4-15%, and the dilute hydrochloric acid containing impurities mainly comes from byproducts in production of pharmacy, pesticides and dye intermediates. The impurities are mainly low boiling point organic substances including alcohols, ethers and aldehydes.
A method for purifying hydrogen chloride by using low-concentration dilute hydrochloric acid containing impurities comprises the following steps:
(1) detecting the components of the impurities, and if the impurities contain substances which react with calcium chloride, classifying a differential pressure method purification process and a sulfuric acid method purification process as alternative purification processes; if the impurities do not contain substances which react with calcium chloride, a differential pressure method purification process, a calcium chloride method purification process and a sulfuric acid method purification process are listed as alternative purification processes;
(2) further analyzing the boiling point range of the components in the impurities, and selecting a pressure difference method for purification if the boiling point of the main component is lower than 100 ℃; if the boiling point of the main component is greater than 100 ℃, one of the alternative purification processes is selected for purification from the other processes excluding the differential pressure purification process.
Referring to fig. 1, the device adopted in the pressure-difference method purification process comprises a raw material tank 1, a positive pressure rectifying tower 2, a vacuum concentration tower 3 and a positive pressure desorption tower 4 which are sequentially communicated, wherein the raw material tank 1 is communicated with the positive pressure rectifying tower 2 through a first preheater 5 and a second preheater 6, the lower part of the positive pressure rectifying tower 2 is communicated with a first reboiler 7, the first reboiler 7 is communicated with a steam pipeline, the top part of the positive pressure rectifying tower 2 is communicated with the lower part of the vacuum concentration tower through a second reboiler 8, the top part of the vacuum concentration tower 3 is communicated with a first condenser 9, and the first condenser 9 is communicated with a vacuum system 10; the top of the positive pressure desorption tower 4 is sequentially communicated with a second condenser 11 and a third condenser 12, the lower part of the third condenser 12 is respectively communicated with a sulfuric acid drying system 13 and a molecular sieve drying system 14, the lower part of the positive pressure desorption tower 4 is communicated with a third reboiler 15, and the bottom of the positive pressure desorption tower 4 is communicated with the upper part of the vacuum concentration tower 3.
The first reboiler 7 is communicated with the first preheater 5, and the third reboiler 15 is communicated with the second preheater 6; the bottom of the first condenser 9 is communicated with a condensed water collecting device 16, and the bottoms of the second condenser 11 and the third condenser 12 are respectively communicated with the upper part of the positive pressure desorption tower 4.
The differential pressure purification process comprises the following steps: 4-15% of hydrochloric acid containing impurities is subjected to positive pressure evaporation, rectification and concentration by a positive pressure rectification tower 2, the evaporated steam containing impurities is used as a heat source for vacuum evaporation, rectification and concentration by a vacuum concentration tower 3, and the concentration of the hydrochloric acid is increased to 22-23% by the vacuum concentration tower 3; sending 22-23% hydrochloric acid to a positive pressure desorption tower 4, producing hydrogen chloride gas at the tower top, and obtaining hydrochloric acid with the concentration of 15.6-19.5% at the tower bottom; returning 15.6-19.5% hydrochloric acid to the vacuum concentration tower 3 in the previous process for concentration.
Referring to fig. 2, the device adopted in the calcium chloride purification process comprises a raw material tank 1, a positive pressure rectifying tower 2, a vacuum concentration tower 3, a calcium chloride analysis tower 17 and a calcium chloride concentration tower 18 which are sequentially communicated, wherein the raw material tank 1 is communicated with the positive pressure rectifying tower 2 through a first preheater 5 and a second preheater 6, the lower part of the positive pressure rectifying tower 2 is communicated with a first reboiler 7, the first reboiler 7 is communicated with a steam pipeline, the top part of the positive pressure rectifying tower 2 is communicated with the lower part of the vacuum concentration tower 3 through a second reboiler 8, the top part of the vacuum concentration tower 3 is communicated with a first condenser 9, and the first condenser 9 is communicated with a vacuum system 10; the top of the calcium chloride desorption tower 17 is sequentially communicated with a second condenser 11 and a third condenser 12, the lower part of the third condenser 12 is respectively communicated with a sulfuric acid drying system 13 and a molecular sieve drying system 14, and the lower part of the calcium chloride desorption tower 17 is communicated with a third reboiler 15; the top of the calcium chloride concentration tower 18 is communicated with a fourth condenser 19, the lower part of the calcium chloride concentration tower 18 is communicated with a fourth reboiler 20, and the bottom of the calcium chloride concentration tower 18 is communicated with the upper part of the calcium chloride analysis tower 17.
The bottoms of the second condenser 11 and the third condenser 12 are respectively communicated with the upper part of a calcium chloride analysis tower 17, and the bottom of the calcium chloride concentration tower 18 is communicated with the upper part of the calcium chloride analysis tower 17 through a circulating pump 21; the bottom of the fourth condenser 19 is communicated with a calcium chloride concentrated condensed water collector 22.
The calcium chloride method purification process comprises the following steps: 4-15% of hydrochloric acid containing impurities is subjected to positive pressure evaporation, rectification and concentration by a positive pressure rectification tower 2, the evaporated steam containing impurities is used as a heat source for vacuum evaporation, rectification and concentration by a vacuum concentration tower 3, and the concentration of the hydrochloric acid is increased to 22-23% by the vacuum concentration tower 3; and (3) sending 22-23% hydrochloric acid to a calcium chloride analysis tower 17, producing hydrogen chloride gas at the tower top, sending dilute calcium chloride from the tower bottom to a calcium chloride concentration tower 18, mixing the concentrated calcium chloride with 22-23% hydrochloric acid, entering the calcium chloride analysis tower 17, and discharging the hydrogen chloride gas.
Referring to fig. 3, the device adopted by the sulfuric acid method purification process comprises a raw material tank 1, a positive pressure rectifying tower 2, a vacuum concentration tower 3, a sulfuric acid analysis tower 23 and a dilute sulfuric acid vacuum concentration system 24 which are sequentially communicated, wherein the raw material tank 1 is communicated with the positive pressure rectifying tower 2 through a preheater, the lower part of the positive pressure rectifying tower 2 is communicated with a first reboiler 7, the top part of the positive pressure rectifying tower 2 is communicated with the lower part of the vacuum concentration tower 3 through a second reboiler 8, and the top part of the vacuum concentration tower 3 is communicated with a first condenser 9; the top of the sulfuric acid desorption tower 23 is sequentially communicated with a second condenser 11 and a third condenser 12, the lower part of the third condenser 12 is respectively communicated with a sulfuric acid drying system 13 and a molecular sieve drying system 14, and the lower part of the sulfuric acid desorption tower 23 is communicated with a third reboiler 15; the dilute sulfuric acid vacuum concentration system 24 is also communicated with the upper part of the sulfuric acid analysis tower 23.
The preheater comprises a first preheater 5 and a second preheater 6 which are communicated in sequence, the second preheater 6 is communicated with the upper part of the positive pressure rectifying tower 2, the first reboiler 7 is communicated with the first preheater 5, and the third reboiler 15 is communicated with the second preheater 6; the bottoms of the second condenser 11 and the third condenser 12 are respectively communicated with the upper part of a sulfuric acid analysis tower 23.
The sulfuric acid method purification process comprises the following steps: 4-15% of hydrochloric acid containing impurities is subjected to positive pressure evaporation, rectification and concentration by a positive pressure rectification tower 2, the evaporated steam containing impurities is used as a heat source for vacuum evaporation, rectification and concentration by a vacuum concentration tower 3, and the concentration of the hydrochloric acid is increased to 22-23% by the vacuum concentration tower 3; and (3) sending the 22-23% hydrochloric acid to a sulfuric acid analysis tower 23, producing hydrogen chloride gas at the tower top, sending the dilute sulfuric acid from the tower bottom to a dilute sulfuric acid vacuum concentration system 24, mixing the concentrated sulfuric acid with the 22-23% hydrochloric acid, entering the sulfuric acid analysis tower 23, and discharging the hydrogen chloride gas.
The invention adopts different purification processes according to different components and boiling point ranges of impurities in the dilute hydrochloric acid, and the manufacturing cost, the operation cost and the purification efficiency of the equipment are optimal.
It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that within the spirit of the invention and the scope of the appended claims, any modifications and variations of the invention may be made without departing from the spirit of the invention.
Claims (9)
1. A method for purifying hydrogen chloride by using low-concentration dilute hydrochloric acid containing impurities is characterized by comprising the following steps:
(1) detecting the components of the impurities, and if the impurities contain substances which react with calcium chloride, classifying a differential pressure method purification process and a sulfuric acid method purification process as alternative purification processes; if the impurities do not contain substances which react with calcium chloride, a differential pressure method purification process, a calcium chloride method purification process and a sulfuric acid method purification process are listed as alternative purification processes;
(2) further analyzing the boiling point range of the components in the impurities, and selecting a pressure difference method for purification if the boiling point of the main component is lower than 100 ℃; if the boiling point of the main component is more than 100 ℃, selecting one of other processes for purifying, wherein the other processes are the alternative purifying processes except the differential pressure method purifying process;
the differential pressure purification process comprises the following steps: the method comprises the following steps of (1) carrying out positive-pressure evaporation, rectification and concentration on hydrochloric acid containing impurities with the mass fraction of 4-15% by using a positive-pressure rectification tower, taking evaporated steam containing impurities as a heat source for vacuum evaporation, rectification and concentration in a vacuum concentration tower, and increasing the concentration of the hydrochloric acid to 22-23% by using the vacuum concentration tower; sending 22-23% hydrochloric acid to a positive pressure desorption tower, producing hydrogen chloride gas at the tower top, and obtaining hydrochloric acid with the concentration of 15.6-19.5% at the tower bottom; returning 15.6-19.5% hydrochloric acid to the previous working procedure for concentration;
the calcium chloride method purification process comprises the following steps: 4-15% of hydrochloric acid containing impurities is subjected to positive pressure evaporation, rectification and concentration through a positive pressure rectification tower, the evaporated steam containing impurities is used as a heat source for vacuum evaporation, rectification and concentration through a vacuum concentration tower, and the concentration of the hydrochloric acid is increased to 22-23% through the vacuum concentration tower; sending 22-23% hydrochloric acid to a calcium chloride analysis tower, producing hydrogen chloride gas at the tower top, sending dilute calcium chloride from the tower bottom to a calcium chloride concentration tower, mixing the concentrated calcium chloride with 22-23% hydrochloric acid, entering the calcium chloride analysis tower, and producing hydrogen chloride gas;
the sulfuric acid method purification process comprises the following steps: 4-15% of hydrochloric acid containing impurities is subjected to positive pressure evaporation, rectification and concentration through a positive pressure rectification tower, the evaporated steam containing impurities is used as a heat source for vacuum evaporation, rectification and concentration through a vacuum concentration tower, and the concentration of the hydrochloric acid is increased to 22-23% through the vacuum concentration tower; and (3) sending the 22-23% hydrochloric acid to a sulfuric acid analysis tower, producing hydrogen chloride gas at the tower top, sending the dilute sulfuric acid at the tower bottom to a dilute sulfuric acid vacuum concentration system, mixing the concentrated sulfuric acid with the 22-23% hydrochloric acid, entering the sulfuric acid analysis tower, and producing the hydrogen chloride gas.
2. The method for purifying hydrogen chloride by using dilute hydrochloric acid containing impurities at low concentration as claimed in claim 1, wherein: the hydrochloric acid containing impurities comes from byproducts in the production of pharmacy, pesticides and dye intermediates.
3. The method for purifying hydrogen chloride with low-concentration dilute hydrochloric acid containing impurities according to claim 1 or 2, characterized in that: the impurities are low boiling point organic substances including alcohols, ethers and aldehydes.
4. The method for purifying hydrogen chloride by using dilute hydrochloric acid containing impurities at low concentration as claimed in claim 1, wherein: the device adopted by the pressure difference method purification process comprises a raw material tank, a positive pressure rectifying tower, a vacuum concentration tower and a positive pressure analysis tower which are sequentially communicated, wherein the raw material tank is communicated with the positive pressure rectifying tower through a first preheater and a second preheater, the lower part of the positive pressure rectifying tower is communicated with a first reboiler, the first reboiler is communicated with a steam pipeline, the top part of the positive pressure rectifying tower is communicated with the lower part of the vacuum concentration tower through a second reboiler, the top part of the vacuum concentration tower is communicated with a first condenser, and the first condenser is communicated with a vacuum system; the top of the positive pressure analysis tower is sequentially communicated with a second condenser and a third condenser, the lower part of the third condenser is respectively communicated with a sulfuric acid drying system and a molecular sieve drying system, the lower part of the positive pressure analysis tower is communicated with a third reboiler, and the bottom of the positive pressure analysis tower is communicated with the upper part of a vacuum concentration tower.
5. The method for purifying hydrogen chloride by using dilute hydrochloric acid containing impurities at low concentration as claimed in claim 4, wherein: the first reboiler is communicated with the first preheater, and the third reboiler is communicated with the second preheater; the bottom of the first condenser is communicated with a condensed water collecting device, and the bottoms of the second condenser and the third condenser are respectively communicated with the upper part of the positive pressure desorption tower.
6. The method for purifying hydrogen chloride by using dilute hydrochloric acid containing impurities at low concentration as claimed in claim 1, wherein: the device adopted by the calcium chloride method purification process comprises a raw material tank, a positive pressure rectifying tower, a vacuum concentration tower, a calcium chloride analysis tower and a calcium chloride concentration tower which are sequentially communicated, wherein the raw material tank is communicated with the positive pressure rectifying tower through a first preheater and a second preheater, the lower part of the positive pressure rectifying tower is communicated with a first reboiler, the first reboiler is communicated with a steam pipeline, the top part of the positive pressure rectifying tower is communicated with the lower part of the vacuum concentration tower through a second reboiler, the top part of the vacuum concentration tower is communicated with a first condenser, and the first condenser is communicated with a vacuum system; the top of the calcium chloride desorption tower is sequentially communicated with a second condenser and a third condenser, the lower part of the third condenser is respectively communicated with a sulfuric acid drying system and a molecular sieve drying system, and the lower part of the calcium chloride desorption tower is communicated with a third reboiler; the top of the calcium chloride concentration tower is communicated with a fourth condenser, the lower part of the calcium chloride concentration tower is communicated with a fourth reboiler, and the bottom of the calcium chloride concentration tower is communicated with the upper part of a calcium chloride analysis tower.
7. The method for purifying hydrogen chloride by using dilute hydrochloric acid containing impurities at low concentration as claimed in claim 6, wherein: the bottoms of the second condenser and the third condenser are respectively communicated with the upper part of the calcium chloride analysis tower, and the bottom of the calcium chloride concentration tower is communicated with the upper part of the calcium chloride analysis tower through a circulating pump; the bottom of the fourth condenser is communicated with a calcium chloride concentrated condensate water collector.
8. The method for purifying hydrogen chloride by using dilute hydrochloric acid containing impurities at low concentration as claimed in claim 1, wherein: the device adopted by the sulfuric acid method purification process comprises a raw material tank, a positive pressure rectifying tower, a vacuum concentration tower, a sulfuric acid analysis tower and a dilute sulfuric acid vacuum concentration system which are sequentially communicated, wherein the raw material tank is communicated with the positive pressure rectifying tower through a preheater, the lower part of the positive pressure rectifying tower is communicated with a first reboiler, the top part of the positive pressure rectifying tower is communicated with the lower part of the vacuum concentration tower through a second reboiler, and the top part of the vacuum concentration tower is communicated with a first condenser; the top of the sulfuric acid analysis tower is sequentially communicated with a second condenser and a third condenser, the lower part of the third condenser is respectively communicated with a sulfuric acid drying system and a molecular sieve drying system, and the lower part of the sulfuric acid analysis tower is communicated with a third reboiler; the dilute sulfuric acid vacuum concentration system is also communicated with the upper part of the sulfuric acid analysis tower.
9. The method for purifying hydrogen chloride from low-concentration dilute hydrochloric acid containing impurities as claimed in claim 8, wherein: the preheater comprises a first preheater and a second preheater which are communicated in sequence, the second preheater is communicated with the upper part of the positive pressure rectifying tower, the first reboiler is communicated with the first preheater, and the third reboiler is communicated with the second preheater; the bottoms of the second condenser and the third condenser are respectively communicated with the upper part of the sulfuric acid analysis tower.
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