CN112047807A - Impurity removal process for methyl bromide by adopting weak base - Google Patents
Impurity removal process for methyl bromide by adopting weak base Download PDFInfo
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- CN112047807A CN112047807A CN202010859787.2A CN202010859787A CN112047807A CN 112047807 A CN112047807 A CN 112047807A CN 202010859787 A CN202010859787 A CN 202010859787A CN 112047807 A CN112047807 A CN 112047807A
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- absorption tower
- methyl bromide
- weak base
- bromomethane
- spraying
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- GZUXJHMPEANEGY-UHFFFAOYSA-N bromomethane Chemical compound BrC GZUXJHMPEANEGY-UHFFFAOYSA-N 0.000 title claims abstract description 264
- 229940102396 methyl bromide Drugs 0.000 title claims abstract description 100
- 239000012535 impurity Substances 0.000 title claims abstract description 58
- 238000000034 method Methods 0.000 title claims abstract description 37
- 238000010521 absorption reaction Methods 0.000 claims abstract description 151
- 238000005507 spraying Methods 0.000 claims abstract description 84
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims abstract description 72
- 238000001035 drying Methods 0.000 claims abstract description 12
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 6
- 230000003472 neutralizing effect Effects 0.000 claims abstract description 3
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 claims description 31
- 238000009423 ventilation Methods 0.000 claims description 23
- UIIMBOGNXHQVGW-UHFFFAOYSA-M Sodium bicarbonate Chemical compound [Na+].OC([O-])=O UIIMBOGNXHQVGW-UHFFFAOYSA-M 0.000 claims description 21
- 238000012856 packing Methods 0.000 claims description 20
- 229910000029 sodium carbonate Inorganic materials 0.000 claims description 15
- 229910000030 sodium bicarbonate Inorganic materials 0.000 claims description 10
- 235000017557 sodium bicarbonate Nutrition 0.000 claims description 10
- AYJRCSIUFZENHW-UHFFFAOYSA-L barium carbonate Chemical compound [Ba+2].[O-]C([O-])=O AYJRCSIUFZENHW-UHFFFAOYSA-L 0.000 claims description 6
- VMHLLURERBWHNL-UHFFFAOYSA-M Sodium acetate Chemical compound [Na+].CC([O-])=O VMHLLURERBWHNL-UHFFFAOYSA-M 0.000 claims description 3
- 239000001632 sodium acetate Substances 0.000 claims description 3
- 235000017281 sodium acetate Nutrition 0.000 claims description 3
- UIIMBOGNXHQVGW-DEQYMQKBSA-M Sodium bicarbonate-14C Chemical compound [Na+].O[14C]([O-])=O UIIMBOGNXHQVGW-DEQYMQKBSA-M 0.000 claims description 2
- 235000017550 sodium carbonate Nutrition 0.000 claims description 2
- 238000000746 purification Methods 0.000 abstract description 5
- 230000000694 effects Effects 0.000 abstract description 2
- 239000002585 base Substances 0.000 description 65
- 238000007599 discharging Methods 0.000 description 32
- 239000000945 filler Substances 0.000 description 17
- 239000007789 gas Substances 0.000 description 17
- 230000000052 comparative effect Effects 0.000 description 16
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 9
- 239000002808 molecular sieve Substances 0.000 description 8
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 description 8
- 238000005273 aeration Methods 0.000 description 5
- WKBOTKDWSSQWDR-UHFFFAOYSA-N Bromine atom Chemical compound [Br] WKBOTKDWSSQWDR-UHFFFAOYSA-N 0.000 description 4
- CPELXLSAUQHCOX-UHFFFAOYSA-N Hydrogen bromide Chemical compound Br CPELXLSAUQHCOX-UHFFFAOYSA-N 0.000 description 4
- 239000007788 liquid Substances 0.000 description 4
- 239000003513 alkali Substances 0.000 description 3
- GDTBXPJZTBHREO-UHFFFAOYSA-N bromine Substances BrBr GDTBXPJZTBHREO-UHFFFAOYSA-N 0.000 description 3
- 229910052794 bromium Inorganic materials 0.000 description 3
- 238000000354 decomposition reaction Methods 0.000 description 3
- 238000000926 separation method Methods 0.000 description 3
- BMYNFMYTOJXKLE-UHFFFAOYSA-N 3-azaniumyl-2-hydroxypropanoate Chemical compound NCC(O)C(O)=O BMYNFMYTOJXKLE-UHFFFAOYSA-N 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 229910000042 hydrogen bromide Inorganic materials 0.000 description 2
- 238000006386 neutralization reaction Methods 0.000 description 2
- 241000238631 Hexapoda Species 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 201000010099 disease Diseases 0.000 description 1
- 208000037265 diseases, disorders, signs and symptoms Diseases 0.000 description 1
- JIRDGEGGAWJQHQ-UHFFFAOYSA-N disulfur dibromide Chemical compound BrSSBr JIRDGEGGAWJQHQ-UHFFFAOYSA-N 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- -1 hydrogen ions Chemical class 0.000 description 1
- 230000003301 hydrolyzing effect Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000009965 odorless effect Effects 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 239000002689 soil Substances 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
- 238000009333 weeding Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C17/00—Preparation of halogenated hydrocarbons
- C07C17/38—Separation; Purification; Stabilisation; Use of additives
- C07C17/395—Separation; Purification; Stabilisation; Use of additives by treatment giving rise to a chemical modification of at least one compound
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Treating Waste Gases (AREA)
- Gas Separation By Absorption (AREA)
Abstract
The invention relates to a bromomethane impurity removal process adopting weak base, belonging to the field of bromomethane purification and comprising the following steps: step 1, introducing methyl bromide into a first absorption tower from the bottom of the first absorption tower, spraying a weak base solution with the pH of 8-10 from the top of the first absorption tower, and neutralizing the methyl bromide; step 2, introducing the methyl bromide obtained in the step 1 into a second absorption tower from the bottom of the second absorption tower, spraying a sulfuric acid solution from the top of the second absorption tower, and drying the methyl bromide; wherein the weak base solution is prepared from weak base and water. The method has the effects of reducing the loss rate of the methyl bromide and improving the impurity removal yield of the methyl bromide.
Description
Technical Field
The invention relates to the technical field of methyl bromide impurity removal, in particular to a methyl bromide impurity removal process adopting weak base.
Background
Methyl bromide, also known as methyl bromide or methyl bromide, is a colorless, odorless liquid with a boiling point of 3.6 ℃ and is slightly soluble in water. It has strong fumigating action and can kill various harmful living things in high efficiency and broad spectrum. It has strong penetrating power to soil and can penetrate into organism without decomposition, so as to achieve the purposes of killing insects, preventing diseases and weeding.
The process for producing methyl bromide is generally carried out by reacting sulfur with bromine, adding water into the reaction system, hydrolyzing the produced sulfur bromide into hydrobromic acid and sulfuric acid, and reacting the hydrobromic acid with methanol to produce methyl bromide. The bromomethane prepared by the preparation method contains impurities such as hydrogen bromide, methanol, bromine and the like, so that the bromomethane needs to be purified and refined in the production process of the bromomethane.
At present, the impurity removal process for methyl bromide generally comprises the steps of washing methyl bromide through low-concentration strong alkali, drying through sulfuric acid, condensing and collecting, but after the impurity removal method is adopted to remove the impurities from the methyl bromide, the loss rate of the methyl bromide is high, and the yield of the methyl bromide after the impurity removal is low.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a bromomethane impurity removal process adopting weak base, which has the effects of reducing the loss rate of bromomethane and improving the impurity removal yield of bromomethane.
The technical purpose of the invention is realized by the following technical scheme:
a methyl bromide impurity removal process adopting weak base comprises the following steps:
step 1: introducing bromomethane into the first absorption tower from the bottom of the first absorption tower, spraying a weak base solution with the pH of 8-10 from the top of the first absorption tower, and neutralizing the bromomethane;
step 2: introducing the bromomethane obtained in the step (1) into a second absorption tower from the bottom of the second absorption tower, spraying a sulfuric acid solution from the top of the second absorption tower, and drying the bromomethane;
wherein the weak base solution is prepared from weak base and water.
The present invention in a preferred example may be further configured to: the weak base comprises one or more of sodium bicarbonate, sodium carbonate, sodium acetate and barium carbonate.
The present invention in a preferred example may be further configured to: the weak base includes sodium bicarbonate and sodium carbonate.
By adopting the technical scheme, one molecule of sodium carbonate can be subjected to neutralization reaction with two molecules of hydrogen ions, the use amount of the sodium carbonate can be reduced by adopting the sodium carbonate, but the pH value of a saturated sodium carbonate solution is about 10, the pH value of a saturated sodium bicarbonate solution is about 8, and the sodium carbonate and the sodium bicarbonate are matched to be a weak alkali solution, so that the pH value of the weak alkali solution is conveniently controlled to be in the range of 8-10.
The present invention in a preferred example may be further configured to: the ventilation rate of the methyl bromide in the step 1 is 220-235 m/h, and the temperature of the methyl bromide is 25-35 ℃.
The present invention in a preferred example may be further configured to: the spraying amount of the weak base solution is 1.5-2.5 m/h, the spraying temperature is 30-50 ℃, and the pressure in the first absorption tower is 1.4-1.6 atm.
The present invention in a preferred example may be further configured to: the first absorption tower adopts corrugated packing, and the height of the packing layer is 3-4 m.
The present invention in a preferred example may be further configured to: the ventilation rate of the bromomethane in the step 2 is 220-235 m/h, and the temperature of the bromomethane is 35-45 ℃.
The present invention in a preferred example may be further configured to: the mass concentration of the sulfuric acid is 85-95%.
The present invention in a preferred example may be further configured to: in the step 2, the spraying amount of the sulfuric acid is 1.5-2.5 m/h, the spraying temperature is 50-70 ℃, and the pressure in the second absorption tower is 1.3-1.5 atm.
The present invention in a preferred example may be further configured to: the second absorption tower adopts corrugated packing, and the height of the packing layer is 3-4 m.
The invention has the following beneficial effects:
according to the invention, the methyl bromide is neutralized by using the weak base solution with the pH of 8-10, so that hydrogen bromide, methanol and bromine doped in the methyl bromide can be effectively removed, and the decomposition of the methyl bromide can be reduced, thereby reducing the loss rate of the methyl bromide and improving the yield of the methyl bromide after impurity removal. In addition, the weak base has small corrosion performance and small corrosion to equipment, thereby prolonging the service life of the equipment and reducing the cost. In addition, because the decomposition of the methyl bromide is reduced, the concentration of bromine salt generated in the weak base solution is lower, so that the weak base solution after impurity removal can be directly discharged, the weak base solution does not need to be concentrated and desalted, and the energy consumption for impurity removal is reduced.
According to the invention, the weak base solution is adopted to remove impurities from the methyl bromide, so that the condition of incomplete impurity removal is easy to occur, although the weak base solution is adopted to carry out neutralization impurity removal, the type and the thickness of the filler are limited by adopting a contact mode of an absorption tower, the spraying amount, the spraying temperature and the pressure in the tower of the weak base solution are controlled, the introduction amount and the introduction temperature of the methyl bromide are controlled, and the loss rate of the methyl bromide is reduced, and the purity of the methyl bromide can be improved.
In addition, the water contained in the methyl bromide is effectively removed through the sulfuric acid with a certain concentration and limiting the spraying amount and the spraying temperature of the sulfuric acid, so that the content of impurities in the methyl bromide is further reduced, and the purity of the methyl bromide is improved.
Detailed Description
The present invention will be described in further detail with reference to examples and comparative examples.
In the following examples and comparative examples:
the height of the first absorption tower is 7.5m, the tower diameter is 400mm, and corrugated packing is adopted.
The height of the second absorption tower is 7.5m, the diameter of the tower is 400mm, and corrugated packing is adopted.
Example 1
A methyl bromide impurity removal process adopting weak base comprises the following steps:
step 1: introducing bromomethane gas into the first absorption tower from the bottom of the first absorption tower at a ventilation rate of 220 m/h, and discharging the bromomethane gas from the top of the first absorption tower; spraying the weak base solution containing sodium acetate and barium carbonate from the top of the first absorption tower at the spraying amount of 1.5 m/h, and discharging from the bottom of the first absorption tower; wherein the pH value of the weak base solution is 9, and the height of the filler layer is 3 m; the temperature of introducing the methyl bromide into the first absorption tower is 25 ℃, the spraying temperature of the weak base solution is 30 ℃, and the pressure in the first absorption tower is 1.4 atm.
Step 2: introducing the bromomethane discharged in the step 1 into a second absorption tower from the bottom of the second absorption tower at an aeration rate of 220 m/h, and then discharging the bromomethane from the top of the second absorption tower; spraying the sulfuric acid solution with the mass concentration of 85% from the top of the second absorption tower at the spraying amount of 1.5 m/h, and discharging from the bottom of the second absorption tower; wherein the height of the filler layer is 3 m; the temperature of introducing the methyl bromide into the second absorption tower is 35 ℃, the spraying temperature of the sulfuric acid is 50 ℃, and the pressure in the second absorption tower is 1.3 atm.
And step 3: and (3) further drying the methyl bromide discharged in the step (2) by using a molecular sieve, and condensing, collecting and storing.
Example 2
A methyl bromide impurity removal process adopting weak base comprises the following steps:
step 1: introducing bromomethane gas into the first absorption tower from the bottom of the first absorption tower at the ventilation rate of 224 m/h, and discharging the bromomethane gas from the top of the first absorption tower; spraying a weak base solution containing sodium carbonate and sodium bicarbonate from the top of the first absorption tower at a spraying amount of 1.75 m/h, and discharging from the bottom of the first absorption tower; wherein the pH value of the weak base solution is 8.5, and the height of the filler layer is 3.25 m; the temperature of introducing the methyl bromide into the first absorption tower is 27.5 ℃, the spraying temperature of the weak base solution is 35 ℃, and the pressure in the first absorption tower is 1.45 atm.
Step 2: introducing the bromomethane discharged in the step 1 into a second absorption tower from the bottom of the second absorption tower at the ventilation rate of 224 m/h, and then discharging the bromomethane from the top of the second absorption tower; spraying the sulfuric acid solution with the mass concentration of 87.5% from the top of the second absorption tower at the spraying amount of 1.75 m/h, and discharging from the bottom of the second absorption tower; wherein the height of the filler layer is 3.25 m; the temperature of introducing the methyl bromide into the second absorption tower is 37.5 ℃, the spraying temperature of the sulfuric acid is 55 ℃, and the pressure in the second absorption tower is 1.35 atm.
And step 3: and (3) further drying the methyl bromide discharged in the step (2) by using a molecular sieve, and condensing, collecting and storing.
Example 3
A methyl bromide impurity removal process adopting weak base comprises the following steps:
step 1: introducing bromomethane gas into the first absorption tower from the bottom of the first absorption tower at the ventilation rate of 228 m/h, and discharging the bromomethane gas from the top of the first absorption tower; spraying a weak base solution containing sodium carbonate and sodium bicarbonate from the top of the first absorption tower at a spraying amount of 2 m/h, and discharging from the bottom of the first absorption tower; wherein the pH value of the weak base solution is 8, and the height of the filler layer is 3.5 m; the temperature of introducing the methyl bromide into the first absorption tower is 30 ℃, the spraying temperature of the weak base solution is 40 ℃, and the pressure in the first absorption tower is 1.5 atm.
Step 2: introducing the bromomethane discharged in the step 1 into a second absorption tower from the bottom of the second absorption tower at the ventilation rate of 228 m/h, and then discharging the bromomethane from the top of the second absorption tower; spraying the sulfuric acid solution with the mass concentration of 90% from the top of the second absorption tower at the spraying amount of 2 m/h, and discharging from the bottom of the second absorption tower; wherein the height of the filler layer is 3.5 m; the temperature of introducing the methyl bromide into the second absorption tower is 40 ℃, the spraying temperature of the sulfuric acid is 60 ℃, and the pressure in the second absorption tower is 1.4 atm.
And step 3: and (3) further drying the methyl bromide discharged in the step (2) by using a molecular sieve, and condensing, collecting and storing.
Example 4
A methyl bromide impurity removal process adopting weak base comprises the following steps:
step 1: introducing bromomethane gas into the first absorption tower from the bottom of the first absorption tower at the ventilation rate of 231 m/h, and discharging the bromomethane gas from the top of the first absorption tower; spraying a weak base solution containing sodium carbonate and sodium bicarbonate from the top of the first absorption tower at a spraying amount of 2.25 m/h, and discharging from the bottom of the first absorption tower; wherein the pH value of the weak base solution is 9.5, and the height of the filler layer is 3.75 m; the temperature of introducing the methyl bromide into the first absorption tower is 32.5 ℃, the spraying temperature of the weak base solution is 45 ℃, and the pressure in the first absorption tower is 1.55 atm.
Step 2: introducing the bromomethane discharged in the step 1 into a second absorption tower from the bottom of the second absorption tower at an aeration rate of 231 m/h, and then discharging the bromomethane from the top of the second absorption tower; spraying the sulfuric acid solution with the mass concentration of 92.5% from the top of the second absorption tower at the spraying amount of 2.25 m/h, and discharging from the bottom of the second absorption tower; wherein the height of the filler layer is 3.75 m; the temperature of introducing the methyl bromide into the second absorption tower is 42.5 ℃, the spraying temperature of the sulfuric acid is 65 ℃, and the pressure in the second absorption tower is 1.45 atm.
And step 3: and (3) further drying the methyl bromide discharged in the step (2) by using a molecular sieve, and condensing, collecting and storing.
Example 5
A methyl bromide impurity removal process adopting weak base comprises the following steps:
step 1: introducing bromomethane gas into the first absorption tower at the ventilation rate of 235 m/h from the bottom of the first absorption tower, and discharging the bromomethane gas from the top of the first absorption tower; spraying weak base solution containing sodium carbonate and sodium bicarbonate from the top of the first absorption tower at the spraying amount of 2.5 m/h, and discharging from the bottom of the first absorption tower; wherein the pH value of the weak base solution is 10, and the height of the filler layer is 4 m; the temperature of introducing the methyl bromide into the first absorption tower is 35 ℃, the spraying temperature of the weak base solution is 50 ℃, and the pressure in the first absorption tower is 1.6 atm.
Step 2: introducing the bromomethane discharged in the step 1 into a second absorption tower from the bottom of the second absorption tower at the ventilation rate of 235 m/h, and then discharging the bromomethane from the top of the second absorption tower; spraying the sulfuric acid solution with the mass concentration of 95% from the top of the second absorption tower at the spraying amount of 2.5 m/h, and discharging from the bottom of the second absorption tower; wherein the height of the filler layer is 4 m; the temperature of introducing the methyl bromide into the second absorption tower is 45 ℃, the spraying temperature of the sulfuric acid is 70 ℃, and the pressure in the second absorption tower is 1.5 atm.
And step 3: and (3) further drying the methyl bromide discharged in the step (2) by using a molecular sieve, and condensing, collecting and storing.
Example 6
A methyl bromide impurity removal process adopting weak base comprises the following steps:
step 1: introducing bromomethane gas into the first absorption tower from the bottom of the first absorption tower at a ventilation rate of 220 m/h, and discharging the bromomethane gas from the top of the first absorption tower; spraying a weak base solution containing sodium carbonate and sodium bicarbonate from the top of the first absorption tower at a spraying amount of 2 m/h, and discharging from the bottom of the first absorption tower; wherein the pH value of the weak base solution is 8.5, and the height of the filler layer is 3.75 m; the temperature of introducing the methyl bromide into the first absorption tower is 35 ℃, the spraying temperature of the weak base solution is 30 ℃, and the pressure in the first absorption tower is 1.45 atm.
Step 2: introducing the bromomethane discharged in the step 1 into a second absorption tower from the bottom of the second absorption tower at an aeration rate of 220 m/h, and then discharging the bromomethane from the top of the second absorption tower; spraying a sulfuric acid solution with the mass concentration of 87.5% from the top of the second absorption tower at the spraying amount of 2 m/h, and discharging from the bottom of the second absorption tower; wherein the height of the filler layer is 3.75 m; the temperature of introducing the methyl bromide into the second absorption tower is 45 ℃, the spraying temperature of the sulfuric acid is 50 ℃, and the pressure in the second absorption tower is 1.35 atm.
And step 3: and (3) further drying the methyl bromide discharged in the step (2) by using a molecular sieve, and condensing, collecting and storing.
Example 7
A methyl bromide impurity removal process adopting weak base comprises the following steps:
step 1: introducing bromomethane gas into the first absorption tower from the bottom of the first absorption tower at the ventilation rate of 231 m/h, and discharging the bromomethane gas from the top of the first absorption tower; spraying a weak base solution containing sodium carbonate and sodium bicarbonate from the top of the first absorption tower at a spraying amount of 1.75 m/h, and discharging from the bottom of the first absorption tower; wherein the pH value of the weak base solution is 9, and the height of the filler layer is 3 m; the temperature of introducing the methyl bromide into the first absorption tower is 27.5 ℃, the spraying temperature of the weak base solution is 40 ℃, and the pressure in the first absorption tower is 1.55 atm.
Step 2: introducing the bromomethane discharged in the step 1 into a second absorption tower from the bottom of the second absorption tower at an aeration rate of 231 m/h, and then discharging the bromomethane from the top of the second absorption tower; spraying the sulfuric acid solution with the mass concentration of 90% from the top of the second absorption tower at the spraying amount of 1.75 m/h, and discharging from the bottom of the second absorption tower; wherein the height of the filler layer is 3 m; the temperature of introducing the methyl bromide into the second absorption tower is 37.5 ℃, the spraying temperature of the sulfuric acid is 60 ℃, and the pressure in the second absorption tower is 1.45 atm.
And step 3: and (3) further drying the methyl bromide discharged in the step (2) by using a molecular sieve, and condensing, collecting and storing.
Example 8
A methyl bromide impurity removal process adopting weak base comprises the following steps:
step 1: introducing bromomethane gas into the first absorption tower from the bottom of the first absorption tower at a ventilation rate of 225 m/h, and discharging the bromomethane gas from the top of the first absorption tower; spraying a weak base solution containing sodium carbonate and sodium bicarbonate from the top of the first absorption tower at a spraying amount of 1.8 m/h, and discharging from the bottom of the first absorption tower; wherein the pH value of the weak base solution is 8.2, and the height of the filler layer is 3.6 m; the temperature of introducing the methyl bromide into the first absorption tower is 30 ℃, the spraying temperature of the weak base solution is 35 ℃, and the pressure in the first absorption tower is 1.6 atm.
Step 2: introducing the bromomethane discharged in the step 1 into a second absorption tower from the bottom of the second absorption tower at an aeration rate of 225 m/h, and then discharging the bromomethane from the top of the second absorption tower; spraying 88% sulfuric acid solution at a spraying amount of 1.4 m/h from the top of the second absorption tower, and discharging from the bottom of the second absorption tower; wherein the height of the filler layer is 3.4 m; the temperature of introducing the methyl bromide into the second absorption tower is 37 ℃, the spraying temperature of the sulfuric acid is 66 ℃, and the pressure in the second absorption tower is 1.46 atm.
And step 3: and (3) further drying the methyl bromide discharged in the step (2) by using a molecular sieve, and condensing, collecting and storing.
Comparative example 1
A bromomethane edulcoration process using weak base, which differs from example 3 in that in step 1, the ventilation amount of bromomethane is 210m for each year, the temperature is 20 ℃, the pH of the weak base solution is 10.5, the spraying amount of the weak base solution is 1.2m for each year, the spraying temperature is 55 ℃, the height of the packing layer of the first absorption tower is 4.5m, and the pressure in the tower is 1.3 atm;
in step 2, carrying out the ethanol-liquid separation on the bromomethane at 50 ℃ and a gas flow rate of 260 m/h, carrying out the mass concentration of the sulfuric acid at 75% during the ethanol-liquid separation, carrying out the spraying at 45 ℃ and carrying out the ethanol-liquid separation on the sulfuric acid at 3 m/h, wherein the height of a packing layer of the second absorption tower is 2.5m, and the pressure in the tower is 1.7 atm.
Comparative example 2
A bromomethane edulcoration process using weak base, which differs from example 3 in that in step 1, the ventilation amount of bromomethane is 235m for plantation/h at 40 ℃, the pH of the weak base solution is 7.5, the spraying amount of the weak base solution is 3m for plantation/h, the spraying temperature is 25 ℃, the height of the packing layer of the first absorption tower is 2.5m, and the pressure in the tower is 1.8 atm;
in step 2, carrying out labor intensity of methyl bromide at 30 ℃ under 210 m/h, carrying out labor intensity of sulfuric acid at 97% by mass, carrying out spraying at 75 ℃ under 4.5m in height of a packing layer of the second absorption tower under 1.1 atm.
Comparative example 3
A bromomethane edulcoration process using weak base, which differs from example 3 in that in step 1, the ventilation amount of bromomethane is 228 mn/h, the temperature is 30 ℃, the pH of the weak base solution is 7.5, the spraying amount of the weak base solution is 1 mn/h, the spraying temperature is 40 ℃, the height of the packing layer of the first absorption tower is 2m, and the pressure in the tower is 1.5 atm;
in step 2, the ventilation amount of the methyl bromide is 228 m/h, the temperature is 40 ℃, the mass concentration of the sulfuric acid is 90%, the spraying amount of the sulfuric acid is 2m for carrying out plantation/h, the spraying temperature is 60 ℃, the height of a packing layer of the second absorption tower is 3.5m, and the pressure in the tower is 1.4 atm.
Comparative example 4
A bromomethane edulcoration process using weak base, which differs from example 3 in that in step 1, the ventilation amount of bromomethane is 228 mn/h, the temperature is 40 ℃, the pH of the weak base solution is 9, the spraying amount of the weak base solution is 2 mn/h, the spraying temperature is 50 ℃, the height of the packing layer of the first absorption tower is 1.5m, and the pressure in the tower is 1.5 atm;
in step 2, the ventilation amount of the methyl bromide is 228 m/h, the temperature is 40 ℃, the mass concentration of the sulfuric acid is 90%, the spraying amount of the sulfuric acid is 2m for carrying out plantation/h, the spraying temperature is 60 ℃, the height of a packing layer of the second absorption tower is 3.5m, and the pressure in the tower is 1.4 atm.
Comparative example 5
A bromomethane edulcoration process using weak base, which differs from example 3 in that in step 1, the ventilation amount of bromomethane is 260m for each year, the temperature is 20 ℃, the pH of the weak base solution is 9, the spraying amount of the weak base solution is 2m for each hour, the spraying temperature is 20 ℃, the height of the packing layer of the first absorption tower is 3.5m, and the pressure in the tower is 1.2 atm;
in step 2, the ventilation amount of the methyl bromide is 228 m/h, the temperature is 40 ℃, the mass concentration of the sulfuric acid is 90%, the spraying amount of the sulfuric acid is 2m for carrying out plantation/h, the spraying temperature is 60 ℃, the height of a packing layer of the second absorption tower is 3.5m, and the pressure in the tower is 1.4 atm.
The impurity removal process of examples 1 to 8 and comparative examples 1 to 5 was used to remove impurities from methyl bromide, and the impurity removal yield of the obtained methyl bromide and the content of impurities in the methyl bromide are shown in table 1;
wherein the impurity removal yield of methyl bromide = (content of methyl bromide after purification x purity after purification)/(content of methyl bromide before purification x purity before purification).
TABLE 1 impurity removal yield and impurity content of bromomethane
| Item | Impurity removal yield (%) | Impurity content (ppm) |
| Example 1 | 98.3 | 16.6 |
| Example 2 | 99.5 | 19.5 |
| Example 3 | 98.8 | 18.6 |
| Example 4 | 99.8 | 20.0 |
| Example 5 | 99.9 | 19.5 |
| Example 6 | 98.4 | 15.9 |
| Example 7 | 98.9 | 17.6 |
| Example 8 | 99.6 | 18.4 |
| Comparative example 1 | 85.4 | 60.8 |
| Comparative example 2 | 86.9 | 66.4 |
| Comparative example 3 | 90.3 | 58.9 |
| Comparative example 4 | 87.6 | 56.3 |
| Comparative example 5 | 90.1 | 54.8 |
By combining examples 1-8 and comparative examples 1-2, it can be seen that the yield of methyl bromide obtained by the methyl bromide impurity removal process of examples 1-8 is between 98.3-99.9% and the impurity content is within the range of 15-20ppm, while the yield of methyl bromide obtained by the impurity removal process of comparative examples 1-2 is between 85-91 and the impurity content is within the range of 60-67ppm, thus it can be seen that the impurity removal yield of methyl bromide can be greatly improved and the impurity content in methyl bromide can be reduced by the impurity removal process of the present invention.
In addition, as can be seen from comparative examples 3 to 5, when the impurity removal is performed on methyl bromide after the conditions in example 3 are partially changed, the yield and purity of the obtained methyl bromide are far lower than those of the methyl bromide in example 3, and further, the impurity in the methyl bromide can be sufficiently reduced and the yield of the methyl bromide can be improved only by performing the impurity removal under the conditions within the range defined by the invention.
The present embodiment is only for explaining the present invention, and it is not limited to the present invention, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present invention.
Claims (10)
1. A methyl bromide impurity removal process adopting weak base is characterized by comprising the following steps:
step 1: introducing bromomethane into the first absorption tower from the bottom of the first absorption tower, spraying a weak base solution with the pH of 8-10 from the top of the first absorption tower, and neutralizing the bromomethane;
step 2: introducing the bromomethane obtained in the step (1) into a second absorption tower from the bottom of the second absorption tower, spraying a sulfuric acid solution from the top of the second absorption tower, and drying the bromomethane;
wherein the weak base solution is prepared from weak base and water.
2. The process for removing impurities from methyl bromide by using weak base according to claim 1, which is characterized in that: the weak base comprises one or more of sodium bicarbonate, sodium carbonate, sodium acetate and barium carbonate.
3. The process for removing impurities from methyl bromide by using weak base according to claim 2, which is characterized in that: the weak base includes sodium bicarbonate and sodium carbonate.
4. The process for removing impurities from methyl bromide by using weak base according to claim 3, which is characterized in that: the ventilation rate of the methyl bromide in the step 1 is 220-235 m/h, and the temperature of the methyl bromide is 25-35 ℃.
5. The process for removing impurities from methyl bromide by using weak base according to claim 3, which is characterized in that: the spraying amount of the weak base solution is 1.5-2.5 m/h, the spraying temperature is 30-50 ℃, and the pressure in the first absorption tower is 1.4-1.6 atm.
6. The process for removing impurities from methyl bromide by using weak base according to claim 3, which is characterized in that: the first absorption tower adopts corrugated packing, and the height of the packing layer is 3-4 m.
7. The process for removing impurities from methyl bromide by using weak base according to claim 3, which is characterized in that: the ventilation rate of the bromomethane in the step 2 is 220-235 m/h, and the temperature of the bromomethane is 35-45 ℃.
8. The process for removing impurities from methyl bromide by using weak base according to claim 3, which is characterized in that: the mass concentration of the sulfuric acid is 85-95%.
9. The process for removing impurities from methyl bromide by using weak base according to claim 3, which is characterized in that: in the step 2, the spraying amount of the sulfuric acid is 1.5-2.5 m/h, the spraying temperature is 50-70 ℃, and the pressure in the second absorption tower is 1.3-1.5 atm.
10. The process for removing impurities from methyl bromide by using weak base according to claim 3, which is characterized in that: the second absorption tower adopts corrugated packing, and the height of the packing layer is 3-4 m.
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