CN113045427A - Nitrochlorobenzene preparation method and system capable of reducing nitrate content in wastewater - Google Patents
Nitrochlorobenzene preparation method and system capable of reducing nitrate content in wastewater Download PDFInfo
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- 239000002351 wastewater Substances 0.000 title claims abstract description 89
- BFCFYVKQTRLZHA-UHFFFAOYSA-N 1-chloro-2-nitrobenzene Chemical compound [O-][N+](=O)C1=CC=CC=C1Cl BFCFYVKQTRLZHA-UHFFFAOYSA-N 0.000 title claims abstract description 78
- 229910002651 NO3 Inorganic materials 0.000 title claims abstract description 51
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 title claims abstract description 51
- 238000002360 preparation method Methods 0.000 title claims abstract description 30
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 163
- 239000007788 liquid Substances 0.000 claims abstract description 140
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims abstract description 132
- 229910017604 nitric acid Inorganic materials 0.000 claims abstract description 132
- 238000005406 washing Methods 0.000 claims abstract description 122
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 68
- 238000006396 nitration reaction Methods 0.000 claims abstract description 59
- 230000001546 nitrifying effect Effects 0.000 claims abstract description 56
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 40
- 230000002378 acidificating effect Effects 0.000 claims abstract description 35
- 238000004519 manufacturing process Methods 0.000 claims abstract description 33
- 239000003513 alkali Substances 0.000 claims abstract description 31
- 229910001873 dinitrogen Inorganic materials 0.000 claims abstract description 31
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims abstract description 27
- 239000011347 resin Substances 0.000 claims abstract description 13
- 229920005989 resin Polymers 0.000 claims abstract description 13
- 238000001179 sorption measurement Methods 0.000 claims abstract description 13
- 230000003647 oxidation Effects 0.000 claims abstract description 9
- 238000007254 oxidation reaction Methods 0.000 claims abstract description 9
- 239000002253 acid Substances 0.000 claims description 107
- 239000002699 waste material Substances 0.000 claims description 76
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 68
- 238000000926 separation method Methods 0.000 claims description 30
- 238000000034 method Methods 0.000 claims description 26
- 238000011084 recovery Methods 0.000 claims description 25
- 238000006243 chemical reaction Methods 0.000 claims description 21
- 238000004065 wastewater treatment Methods 0.000 claims description 19
- MVPPADPHJFYWMZ-UHFFFAOYSA-N chlorobenzene Chemical compound ClC1=CC=CC=C1 MVPPADPHJFYWMZ-UHFFFAOYSA-N 0.000 claims description 18
- 238000001035 drying Methods 0.000 claims description 18
- 230000007935 neutral effect Effects 0.000 claims description 17
- 238000007599 discharging Methods 0.000 claims description 13
- 239000007791 liquid phase Substances 0.000 claims description 12
- 230000029087 digestion Effects 0.000 claims description 10
- 239000012071 phase Substances 0.000 claims description 10
- 239000002994 raw material Substances 0.000 claims description 8
- 239000007792 gaseous phase Substances 0.000 claims description 7
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 claims description 7
- 238000007664 blowing Methods 0.000 claims description 6
- 238000006555 catalytic reaction Methods 0.000 claims description 6
- 238000004064 recycling Methods 0.000 claims description 5
- VGPSUIRIPDYGFV-UHFFFAOYSA-N [N].O[N+]([O-])=O Chemical compound [N].O[N+]([O-])=O VGPSUIRIPDYGFV-UHFFFAOYSA-N 0.000 claims description 4
- 239000007789 gas Substances 0.000 claims description 4
- 239000008367 deionised water Substances 0.000 claims description 3
- 229910021641 deionized water Inorganic materials 0.000 claims description 3
- 241000589614 Pseudomonas stutzeri Species 0.000 claims description 2
- 239000002910 solid waste Substances 0.000 abstract description 6
- 238000001514 detection method Methods 0.000 abstract description 5
- VWDWKYIASSYTQR-UHFFFAOYSA-N sodium nitrate Chemical compound [Na+].[O-][N+]([O-])=O VWDWKYIASSYTQR-UHFFFAOYSA-N 0.000 description 8
- CZGCEKJOLUNIFY-UHFFFAOYSA-N 4-Chloronitrobenzene Chemical compound [O-][N+](=O)C1=CC=C(Cl)C=C1 CZGCEKJOLUNIFY-UHFFFAOYSA-N 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- 238000001704 evaporation Methods 0.000 description 5
- 230000008020 evaporation Effects 0.000 description 5
- KMAQZIILEGKYQZ-UHFFFAOYSA-N 1-chloro-3-nitrobenzene Chemical compound [O-][N+](=O)C1=CC=CC(Cl)=C1 KMAQZIILEGKYQZ-UHFFFAOYSA-N 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 235000010344 sodium nitrate Nutrition 0.000 description 4
- 239000004317 sodium nitrate Substances 0.000 description 4
- 238000010926 purge Methods 0.000 description 3
- 150000003839 salts Chemical class 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
- WRIDQFICGBMAFQ-UHFFFAOYSA-N (E)-8-Octadecenoic acid Natural products CCCCCCCCCC=CCCCCCCC(O)=O WRIDQFICGBMAFQ-UHFFFAOYSA-N 0.000 description 2
- LQJBNNIYVWPHFW-UHFFFAOYSA-N 20:1omega9c fatty acid Natural products CCCCCCCCCCC=CCCCCCCCC(O)=O LQJBNNIYVWPHFW-UHFFFAOYSA-N 0.000 description 2
- QSBYPNXLFMSGKH-UHFFFAOYSA-N 9-Heptadecensaeure Natural products CCCCCCCC=CCCCCCCCC(O)=O QSBYPNXLFMSGKH-UHFFFAOYSA-N 0.000 description 2
- ZQPPMHVWECSIRJ-UHFFFAOYSA-N Oleic acid Natural products CCCCCCCCC=CCCCCCCCC(O)=O ZQPPMHVWECSIRJ-UHFFFAOYSA-N 0.000 description 2
- 239000005642 Oleic acid Substances 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 2
- XKMRRTOUMJRJIA-UHFFFAOYSA-N ammonia nh3 Chemical compound N.N XKMRRTOUMJRJIA-UHFFFAOYSA-N 0.000 description 2
- 239000006227 byproduct Substances 0.000 description 2
- 238000002425 crystallisation Methods 0.000 description 2
- 230000008025 crystallization Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- QXJSBBXBKPUZAA-UHFFFAOYSA-N isooleic acid Natural products CCCCCCCC=CCCCCCCCCC(O)=O QXJSBBXBKPUZAA-UHFFFAOYSA-N 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- ZQPPMHVWECSIRJ-KTKRTIGZSA-N oleic acid Chemical compound CCCCCCCC\C=C/CCCCCCCC(O)=O ZQPPMHVWECSIRJ-KTKRTIGZSA-N 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 238000005273 aeration Methods 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 239000003518 caustics Substances 0.000 description 1
- 239000012141 concentrate Substances 0.000 description 1
- 238000004821 distillation Methods 0.000 description 1
- 239000002920 hazardous waste Substances 0.000 description 1
- 244000005700 microbiome Species 0.000 description 1
- 238000006386 neutralization reaction Methods 0.000 description 1
- 230000003472 neutralizing effect Effects 0.000 description 1
- 239000010865 sewage Substances 0.000 description 1
- 239000008234 soft water Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C201/00—Preparation of esters of nitric or nitrous acid or of compounds containing nitro or nitroso groups bound to a carbon skeleton
- C07C201/06—Preparation of nitro compounds
- C07C201/08—Preparation of nitro compounds by substitution of hydrogen atoms by nitro groups
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C201/00—Preparation of esters of nitric or nitrous acid or of compounds containing nitro or nitroso groups bound to a carbon skeleton
- C07C201/06—Preparation of nitro compounds
- C07C201/16—Separation; Purification; Stabilisation; Use of additives
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- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
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Abstract
The invention provides a nitrochlorobenzene preparation method and a nitrochlorobenzene preparation system capable of reducing the content of nitrate in wastewater, and belongs to the technical field of nitrochlorobenzene production. In the nitrochlorobenzene production method, an acidic nitration liquid A generated by nitration reaction is blown off by nitrogen gas at a predetermined temperature, for example, at a temperature of 75 to 85 ℃, and a small amount of nitric acid remaining in the acidic nitration liquid A is blown off and separated to obtain a nitration liquid B. The nitrifying liquid B only contains a very small amount of nitric acid, after alkali washing and water washing, the generated washing wastewater only contains a small amount of nitrate, through detection, the total nitrogen content in the washing wastewater is less than 600mg/L, the content of the nitrate in the nitrochlorobenzene production wastewater is greatly reduced, the nitrochlorobenzene production wastewater can reach the standard after resin adsorption and Fenton oxidation, and the treatment difficulty and the treatment cost of the nitrochlorobenzene production wastewater are reduced. Meanwhile, the using amount of sodium hydroxide is reduced, and the generation amount of nitrate solid waste is reduced.
Description
Technical Field
The invention belongs to the technical field of nitrochlorobenzene production, and particularly relates to a nitrochlorobenzene preparation method and a nitrochlorobenzene preparation system capable of reducing the content of nitrate in wastewater.
Background
The method is one of important processes for preparing nitrochlorobenzene by using chlorobenzene and nitric acid as raw materials and reacting the raw materials to generate the nitrochlorobenzene under the catalytic action of sulfuric acid. The reaction is finished, and then materials are refined and separated to obtain acidic nitration liquid and waste acid. Due to the inherent nature of this reaction, the sulfuric acid does not react completely with the nitric acid in the nitric acid mixture, and a small amount (about 1%) of nitric acid remains dissolved in the acidic nitration liquor. Before the acidic nitrifying liquid enters a rectification process, residual acid in the material must be neutralized by using a sodium hydroxide solution, and then the residual acid is washed by using soft water again to obtain a neutral nitrifying liquid. The neutral nitrifying liquid is dried and then subjected to a series of procedures such as rectification, crystallization and the like to obtain finished products of p-nitrochlorobenzene and o-nitrochlorobenzene. In the alkali washing neutralization process, sodium nitrate obtained by neutralizing nitric acid and sodium hydroxide enters alkali washing wastewater, and the total nitrogen content in the alkali washing wastewater is up to 10000mg/L and far exceeds a sewage discharge index (70 mg/L) due to the existence of the sodium nitrate. And the sodium nitrate is extremely stable in aqueous solution and is difficult to remove by conventional physical and chemical means, and because the salt concentration in the water is too high, microorganisms are difficult to survive in the water, so the biochemical treatment means cannot be realized. Only can be separated by evaporation and concentration, and the finally obtained solid sodium nitrate waste salt is treated as hazardous waste. The evaporation process needs to consume a large amount of energy, and the waste salt disposal cost is high and the economical efficiency is poor. Moreover, the production process causes large nitric acid loss, and practice shows that the yield of nitrochlorobenzene is calculated according to 6 ten thousand tons/year, and the amount of nitric acid lost due to the reasons reaches 730 tons every year in the nitrochlorobenzene production process.
Disclosure of Invention
In view of the above, the invention provides a preparation method of nitrochlorobenzene, which can reduce the content of nitrate in wastewater, so as to solve the technical problem that in the prior art, a large amount of nitrate exists in nitrochlorobenzene production wastewater and the treatment is difficult.
The invention also provides a nitrochlorobenzene preparation device capable of reducing the content of nitrate in wastewater, so as to realize the method, reduce the content of nitrate in wastewater from nitrochlorobenzene production and reduce the loss of nitric acid in the nitrochlorobenzene production process.
The technical scheme adopted by the invention for solving the technical problems is as follows:
a preparation method of nitrochlorobenzene capable of reducing the content of nitrate in wastewater comprises the following steps:
a. nitration reaction: chlorobenzene and nitric acid are used as raw materials, and are reacted to generate acidic nitration liquid A under the catalysis of sulfuric acid;
b. nitrogen stripping: blowing nitrogen into the acidic nitrifying liquid A at a preset temperature, and carrying out stripping to obtain nitrifying liquid B and nitrogen containing nitric acid;
c. acid oil separation: carrying out acid-oil separation on the nitrifying liquid B to obtain nitrifying liquid C and waste acid;
d. alkali washing and water washing: after the nitrifying liquid C is contacted with a sodium hydroxide solution and subjected to alkali washing, the nitrifying liquid C is contacted with deionized water and subjected to water washing to obtain a neutral nitrifying liquid D and washing wastewater;
e. drying and separating: and drying and separating the neutral nitration liquid D to prepare the nitrochlorobenzene.
Preferably, the method further comprises the following steps:
f. and (3) recovering nitric acid: and (c) absorbing the nitric acid in the nitric acid-containing nitrogen gas obtained in the step b by using concentrated sulfuric acid, wherein the obtained concentrated sulfuric acid containing the nitric acid is used for preparing mixed acid for digestion reaction.
Preferably, the method further comprises the following steps:
g. waste acid concentration: concentrating the waste acid obtained in the step c to obtain concentrated waste acid;
h. and (3) recycling waste acid: and (c) absorbing the nitric acid in the nitric acid-containing nitrogen gas obtained in the step (b) by using concentrated waste acid, and using the obtained concentrated waste acid containing the nitric acid to prepare mixed acid for digestion reaction.
Preferably, the method further comprises the following steps:
i. wastewater treatment: and d, sequentially carrying out resin adsorption and oxidation treatment on the washing wastewater obtained in the step d, and discharging the washing wastewater up to the standard.
A nitrochlorobenzene preparation system capable of reducing the nitrate content in wastewater comprises:
the nitration reaction device is used for reacting chlorobenzene and nitric acid serving as raw materials under the catalysis of sulfuric acid to generate acidic nitration liquid A;
the feed end of the nitrogen stripping device is connected with the discharge end of the nitration reaction device and is used for blowing nitrogen into the acidic nitration liquid A at a preset temperature to carry out stripping so as to obtain nitration liquid B and nitrogen containing nitric acid; the top of the nitrogen stripping device is provided with a nitric acid-containing nitrogen discharging pipe, and the bottom of the nitrogen stripping device is provided with a nitrifying liquid B discharging pipe;
the feed end of the acid-oil separation device is connected with the nitrifying liquid B discharge pipe and is used for carrying out acid-oil separation on the nitrifying liquid B to obtain nitrifying liquid C and waste acid; the top of the acid-oil separation device is provided with a nitrifying liquid C discharge pipe, and the bottom of the acid-oil separation device is provided with a waste acid discharge pipe;
the alkali washing and water washing device is used for sequentially carrying out alkali washing and water washing on the nitrifying liquid C to obtain neutral nitrifying liquid D and washing wastewater; the alkaline washing and water washing device comprises an alkaline washing kettle and a water washing kettle which are sequentially connected, wherein the feed end of the alkaline washing kettle is connected with the nitrifying liquid C discharge pipe, and the bottom of the alkaline washing kettle is connected with a washing wastewater tank; the feed end of the water washing kettle is connected with the oil phase discharge end of the alkaline washing kettle, and the bottom of the water washing kettle is connected with the washing wastewater tank; and
and the feed end of the drying and separating device is connected with the oil phase discharge end of the washing kettle and is used for drying and separating the neutral nitration liquid D to prepare nitrochlorobenzene.
Preferably, the nitrochlorobenzene preparation system capable of reducing the nitrate content in the wastewater further comprises: the nitric acid recovery device is used for absorbing nitric acid in the nitric acid-containing nitrogen obtained from the nitrogen stripping device by using concentrated sulfuric acid to obtain concentrated sulfuric acid containing nitric acid; the gas phase feed end of the nitric acid recovery device is connected with the nitric acid-containing nitrogen discharge pipe, and a concentrated sulfuric acid feed pipe is arranged on the nitric acid recovery device; the discharge end of the nitric acid recovery device is connected with a mixed acid preparation tank.
Preferably, the nitrochlorobenzene preparation system capable of reducing the nitrate content in the wastewater further comprises: the feed end of the waste acid concentrating device is connected with the waste acid discharge pipe and is used for concentrating the waste acid obtained in the acid oil separation device to obtain concentrated waste acid; and the discharge end of the concentrated waste acid of the waste acid concentrating device is connected with the concentrated sulfuric acid feed pipe so as to utilize the concentrated waste acid to absorb nitric acid in the nitric acid-containing nitrogen obtained from the nitrogen stripping device, and the obtained concentrated waste acid containing the nitric acid is used for preparing mixed acid for digestion reaction.
Preferably, the nitrochlorobenzene preparation system capable of reducing the nitrate content in the wastewater further comprises: the wastewater treatment device is connected with the wastewater treatment tank and is used for treating the washing wastewater generated by the alkaline washing and rinsing device; the wastewater treatment device comprises a resin adsorption component and a Fenton reaction component which are connected in sequence.
Preferably, the nitrogen stripping device comprises a first venturi mixer and a first gas-liquid separator, and the discharge end of the first venturi mixer is connected with the first gas-liquid separator; the bottom of first vapour and liquid separator is provided with first forced circulation subassembly, the discharge end of first forced circulation subassembly is connected the liquid phase entry of first venturi mixer, the gaseous phase entry of first venturi mixer is provided with the nitrogen gas inlet pipe.
Preferably, the nitric acid recovery device comprises a second venturi mixer and a second gas-liquid separator, and the discharge end of the second venturi mixer is connected with the second gas-liquid separator; the bottom of second vapour and liquid separator is provided with the second forced circulation subassembly, the discharge end of second forced circulation subassembly is connected the liquid phase entry of second venturi mixer, the gaseous phase entry of second venturi mixer is connected contain nitric acid nitrogen gas discharging pipe.
According to the technical scheme, the invention provides the nitrochlorobenzene preparation method and the nitrochlorobenzene preparation system capable of reducing the content of the nitrate in the wastewater, and the nitrochlorobenzene preparation method and the nitrochlorobenzene preparation system have the beneficial effects that: the acidic nitrified liquid A produced by the nitration reaction is purged with nitrogen gas at a predetermined temperature, for example, 75 to 85 ℃ to separate a small amount of nitric acid remaining in the acidic nitrified liquid A by purging, thereby obtaining a nitrified liquid B. The nitrifying liquid B only contains a very small amount of nitric acid, after alkali washing and water washing, the generated washing wastewater only contains a small amount of nitrate, through detection, the total nitrogen content in the washing wastewater is less than 600mg/L, the content of the nitrate in the nitrochlorobenzene production wastewater is greatly reduced, the nitrochlorobenzene production wastewater can reach the standard after resin adsorption and Fenton oxidation, and the treatment difficulty and the treatment cost of the nitrochlorobenzene production wastewater are reduced. Meanwhile, the using amount of sodium hydroxide is reduced, and the generation amount of nitrate solid waste is reduced.
Drawings
FIG. 1 is a process flow diagram of a nitrochlorobenzene production process that enables the reduction of nitrate content in wastewater.
FIG. 2 is a flow diagram of the pipeline of a nitrochlorobenzene production system that can reduce the nitrate content in wastewater.
In the figure: the nitrochlorobenzene preparation system 10 capable of reducing the content of nitrate in wastewater, a nitration reaction device 100, a nitrogen stripping device 200, a nitric acid-containing nitrogen discharge pipe 210, a nitration liquid B discharge pipe 220, a first Venturi mixer 230, a first gas-liquid separator 240, a first forced circulation component 250, a forced circulation pump 251, a heater 252, a nitrogen gas feed pipe 260, an acid-oil separation device 300, a nitration liquid C discharge pipe 310, a waste acid discharge pipe 320, an alkaline washing and water washing device 400, an alkaline washing kettle 410, a water washing kettle 420, a washing wastewater tank 430, a drying and separating device 500, a nitric acid recovery device 600, a concentrated sulfuric acid feed pipe 610, a mixed acid configuration tank 620, a second Venturi mixer 630, a second gas-liquid separator 640, a second forced circulation component 650, a waste acid concentration device 700, a wastewater treatment device 800, a resin adsorption component 810, a Fenton reaction component 820 and a nitrogen gas recovery device 900.
Detailed Description
The technical scheme and the technical effect of the invention are further elaborated in the following by combining the drawings of the invention.
Referring to fig. 1, in one embodiment, a method for preparing nitrochlorobenzene capable of reducing the nitrate content in wastewater comprises the following steps:
s11 nitration reaction: chlorobenzene and nitric acid are used as raw materials and react under the catalysis of sulfuric acid to generate acidic nitration liquid A.
The nitration reaction method adopts the traditional nitration reaction process, and chlorobenzene reacts with mixed acid formed by the preparation of nitric acid and concentrated sulfuric acid to generate acidic nitration liquid A. The acidic nitration liquid A contains nitrochlorobenzene (including o-nitrochlorobenzene, m-nitrochlorobenzene and p-nitrochlorobenzene) generated by the reaction, waste sulfuric acid, a small amount of nitric acid (about 1%) remained without complete reaction and other by-products.
Because a small amount of nitric acid is remained in the acidic nitration liquid A, if alkali washing and water washing processes are directly carried out, a large amount of alkali needs to be added, and the alkali washing wastewater contains high-concentration nitrate (the total nitrogen content reaches 10000 mg/L), so that the waste of the alkali and the nitric acid is caused, the wastewater treatment difficulty is increased, the wastewater treatment cost is increased, more nitrate solid wastes are generated after the wastewater treatment, and the treatment cost is higher.
S12, nitrogen stripping: blowing nitrogen into the acidic nitrifying liquid A at a preset temperature, and carrying out stripping to obtain nitrifying liquid B and nitrogen containing nitric acid.
In order to solve the problems, part of nitric acid is recycled, the alkali consumption is reduced, the nitrate content in the nitrochlorobenzene production wastewater is reduced, and the production cost is reduced.
For example, nitrogen gas is blown into the acidic nitrified liquid A at a temperature of 75 to 85 ℃ to blow off the nitric acid, and the nitric acid is removed from the acidic nitrified liquid A as nitric acid vapor together with the nitrogen gas, thereby obtaining a nitrified liquid B containing a very small amount of nitric acid and a nitrogen gas containing nitric acid.
S13, acid oil separation: and (4) carrying out acid-oil separation on the nitrifying liquid B to obtain nitrifying liquid C and waste acid. Separating the nitrifying liquid B by oleic acid to obtain nitrifying liquid C and waste acid, wherein the nitrifying liquid C mainly contains nitrochlorobenzene and a small amount of acid, and the waste acid mainly contains concentrated sulfuric acid with the concentration of about 70%.
S14, alkali washing and water washing: after the nitrifying liquid C is contacted with a sodium hydroxide solution and subjected to alkali washing, the nitrifying liquid C is contacted with deionized water and subjected to water washing, so that a neutral nitrifying liquid D and washing wastewater are obtained.
S15, drying and separating: and drying and separating the neutral nitration liquid D to prepare the nitrochlorobenzene. And (3) separating the neutral nitration liquid D by adopting a traditional separation means, and obtaining o-nitrochlorobenzene, m-nitrochlorobenzene and p-nitrochlorobenzene products by adopting a method of rectification, evaporation, temperature reduction and crystallization.
In the present invention, the acidic nitrified liquid A produced by the nitration reaction is purged with nitrogen gas at a predetermined temperature, for example, 75 to 85 ℃ to thereby separate a small amount of nitric acid remaining in the acidic nitrified liquid A by purging, and thus a nitrified liquid B is obtained. Only a small amount of nitric acid is contained in the nitrifying liquid B, after alkali washing and water washing, only a small amount of nitrate is contained in the generated washing wastewater, through detection, the total nitrogen content in the washing wastewater is less than 600mg/L, the content of the nitrate in the nitrochlorobenzene production wastewater is greatly reduced, the nitrochlorobenzene production wastewater can reach the standard after resin adsorption and Fenton oxidation, and the treatment difficulty and the treatment cost of the nitrochlorobenzene production wastewater are reduced. Meanwhile, the using amount of sodium hydroxide is reduced, and the generation amount of nitrate solid waste is reduced.
In a preferred embodiment, the method for preparing nitrochlorobenzene capable of reducing the nitrate content in wastewater further comprises the following steps:
s16 nitric acid recovery: and (4) absorbing the nitric acid in the nitric acid-containing nitrogen gas obtained in the step S12 by using concentrated sulfuric acid, wherein the obtained concentrated sulfuric acid containing the nitric acid is used for preparing mixed acid for digestion reaction.
In the present embodiment, the property of concentrated sulfuric acid that has good absorption performance for nitric acid is utilized, and the nitrogen containing nitric acid obtained in step S12 and the concentrated sulfuric acid are mixed and subjected to gas-liquid separation to obtain concentrated sulfuric acid containing nitric acid and nitrogen gas, and the concentrated sulfuric acid containing nitric acid can be used to prepare mixed acid for digestion reaction, thereby realizing recovery and utilization of nitric acid. The nitrogen is recycled after alkali washing and drying, so that the nitrogen loss is reduced.
In one embodiment, the concentrated sulfuric acid may be 85% to 90% concentrated sulfuric acid used for preparing mixed acid. Preferably, the waste acid produced in step 13 may be concentrated waste acid obtained by concentrating the waste acid.
For example, the preparation method of nitrochlorobenzene capable of reducing the nitrate content in wastewater further comprises the following steps:
s17, waste acid concentration: and c, concentrating the waste acid obtained in the step c to obtain concentrated waste acid. The waste acid is concentrated by a distillation concentration method to the concentrated waste acid with the sulfuric acid concentration of about 70 percent to the concentrated waste acid with the sulfuric acid concentration of 85 to 88 percent, so that the waste acid can be recycled, and the sulfuric acid consumption is reduced.
S18, recycling waste acid: and (3) absorbing the nitric acid in the nitric acid-containing nitrogen gas obtained in the step (12) by using concentrated waste acid, and using the obtained concentrated waste acid containing the nitric acid for preparing mixed acid for digestion reaction.
Further, the preparation method of nitrochlorobenzene capable of reducing the content of nitrate in wastewater further comprises the following steps:
s19, wastewater treatment: and (4) performing resin adsorption and oxidation treatment on the washing wastewater obtained in the step (14) in sequence, and discharging the washing wastewater after reaching the standard. As only a small amount of nitric acid in the nitrifying liquid B is subjected to alkaline washing and water washing, only a small amount of nitrate is contained in the generated washing wastewater, and the total nitrogen content in the washing wastewater is less than 600mg/L through detection, the washing wastewater is prevented from being treated in an evaporation and concentration mode with high energy consumption, the COD content and the chromaticity of the wastewater are directly reduced by a resin adsorption method, and the discharge requirement can be met after the COD content and the total nitrogen and ammonia nitrogen content of the wastewater are further reduced by a Fenton oxidation method.
Referring to fig. 2, in another embodiment of the present invention, a nitrochlorobenzene production system 10 capable of reducing the nitrate content in wastewater comprises: 100 parts of nitration reaction device, 200 parts of nitrogen stripping device, 300 parts of acid-oil separation device, 400 parts of alkaline washing and washing device and 500 parts of drying and separating device.
The nitration reaction device 100 is used for reacting chlorobenzene and nitric acid serving as raw materials under the catalysis of sulfuric acid to generate an acidic nitration liquid A.
And the feeding end of the nitrogen stripping device 200 is connected with the discharging end of the nitration device 100 and is used for blowing nitrogen into the acidic nitration liquid A at a preset temperature to carry out stripping so as to obtain nitration liquid B and nitrogen containing nitric acid. The top of the nitrogen stripping device 200 is provided with a nitric acid-containing nitrogen discharge pipe 210, and the bottom is provided with a nitrifying liquid B discharge pipe 220.
The feed end of the acid-oil separation device 300 is connected with the nitrifying liquid B discharge pipe 220 and is used for carrying out acid-oil separation on the nitrifying liquid B to obtain nitrifying liquid C and waste acid. The top of the acid-oil separation device 300 is provided with a nitrifying liquid C discharge pipe 310, and the bottom is provided with a waste acid discharge pipe 320.
The alkaline washing and water washing device 400 is used for sequentially performing alkaline washing and water washing operations on the nitrifying liquid C to obtain neutral nitrifying liquid D and washing wastewater. The alkaline washing device 400 comprises an alkaline washing kettle 410 and a water washing kettle 420 which are connected in sequence, wherein the feed end of the alkaline washing kettle 410 is connected with the nitrifying liquid C discharge pipe 310, and the bottom of the alkaline washing kettle is connected with a washing wastewater tank 430. The feed end of the water washing kettle 420 is connected with the oil phase discharge end of the alkaline washing kettle 410, and the bottom of the water washing kettle is connected with the washing wastewater tank 430.
And the feed end of the drying and separating device 500 is connected with the oil phase discharge end of the water washing kettle 420 and is used for drying and separating the neutral nitration liquid D to prepare nitrochlorobenzene.
In the present embodiment, chlorobenzene reacts with mixed acid formed by mixing nitric acid and sulfuric acid in the nitration apparatus 100 to produce acidic nitration liquid a. The acidic nitration liquid A contains nitrochlorobenzene (including o-nitrochlorobenzene, m-nitrochlorobenzene and p-nitrochlorobenzene) generated by the reaction, waste sulfuric acid, a small amount of nitric acid (about 1%) remained without complete reaction and other by-products.
Because a small amount of nitric acid is remained in the acidic nitration liquid A, if alkali washing and water washing processes are directly carried out, a large amount of alkali needs to be added, and the alkali washing wastewater contains high-concentration nitrate (the total nitrogen content reaches 10000 mg/L), so that the waste of the alkali and the nitric acid is caused, the wastewater treatment difficulty is increased, the wastewater treatment cost is increased, more nitrate solid wastes are generated after the wastewater treatment, and the treatment cost is higher.
In order to solve the problems, part of nitric acid is recycled, the alkali consumption is reduced, the nitrate content in the nitrochlorobenzene production wastewater is reduced, the production cost is reduced, the nitrogen stripping device 200 is arranged, the acidic nitration liquid A generated by the reaction is sent into the nitrogen stripping device 200, nitrogen is blown into the acidic nitration liquid A, stripping is carried out at the temperature of 75-85 ℃, a small amount of nitric acid remained in the acidic nitration liquid A is stripped and separated, and the nitration liquid B is obtained.
And (3) carrying out oil-acid separation on the nitrified liquid B by the acid-oil separation device 300 to obtain nitrified liquid C and waste acid, carrying out alkali washing and water washing on the nitrified liquid C by the alkali washing and water washing device 400 to obtain neutral nitrified liquid D and washing wastewater, and carrying out drying separation on the neutral nitrified liquid D by the drying and separating device 500 to prepare nitrochlorobenzene (including o-nitrochlorobenzene, m-nitrochlorobenzene and p-nitrochlorobenzene).
The acidic nitrified liquid A produced by the nitration reaction is purged with nitrogen gas at a predetermined temperature, for example, 75 to 85 ℃ to separate a small amount of nitric acid remaining in the acidic nitrified liquid A by purging, thereby obtaining a nitrified liquid B. Only a small amount of nitric acid is contained in the nitrifying liquid B, after alkali washing and water washing, only a small amount of nitrate is contained in the generated washing wastewater, through detection, the total nitrogen content in the washing wastewater is less than 600mg/L, the content of the nitrate in the nitrochlorobenzene production wastewater is greatly reduced, the nitrochlorobenzene production wastewater can reach the standard after resin adsorption and Fenton oxidation, and the treatment difficulty and the treatment cost of the nitrochlorobenzene production wastewater are reduced. Meanwhile, the using amount of sodium hydroxide is reduced, and the generation amount of nitrate solid waste is reduced.
Further, the nitrochlorobenzene production system 10 capable of reducing the nitrate content in the wastewater further includes: and the nitric acid recovery device 600 is configured to absorb the nitric acid in the nitric acid-containing nitrogen gas obtained in the nitrogen stripping device 200 with concentrated sulfuric acid to obtain concentrated sulfuric acid containing nitric acid. The gaseous phase feed end of nitric acid recovery unit 600 is connected contain nitric acid nitrogen gas discharging pipe 210, just last 600 of nitric acid recovery unit is provided with concentrated sulfuric acid inlet pipe 610, the discharge end of nitric acid recovery unit 600 is connected with mixed acid configuration groove 620.
In the nitrogen stripping device 200, nitrogen gas carrying nitric acid vapor enters the nitric acid recovery device 600 from the nitric acid-containing nitrogen gas discharge pipe 210, and contacts with concentrated sulfuric acid, and after the nitric acid is absorbed by the concentrated sulfuric acid, the concentrated sulfuric acid containing nitric acid enters the mixed acid preparation tank 620 to prepare mixed acid for nitration. The nitrogen is recycled after alkali washing and drying, so that the nitrogen loss is reduced.
Further, in order to recycle the waste acid generated by the acid oil separation device 300, the nitrochlorobenzene preparation system 10 capable of reducing the nitrate content in the wastewater further includes a waste acid concentration device 700, and a feed end of the waste acid concentration device 700 is connected to the waste acid discharge pipe 320, and is configured to concentrate the waste acid obtained in the acid oil separation device 300 to obtain concentrated waste acid. The discharge end of the concentrated waste acid of the waste acid concentrating device 700 is connected to the concentrated sulfuric acid feed pipe 610, so that the concentrated waste acid is used for absorbing nitric acid in the nitric acid-containing nitrogen gas obtained from the nitrogen stripping device 200, and the obtained concentrated waste acid containing nitric acid is used for preparing mixed acid for digestion reaction.
That is, in the acid-oil separation device 300, oleic acid is separated, the generated waste sulfuric acid with lower concentration is concentrated by the waste acid concentration device 700 to obtain sulfuric acid with higher concentration, the sulfuric acid with higher concentration is used as the feed material of the absorption acid of the nitric acid recovery device 600, the nitric acid in the nitrogen gas containing nitric acid is absorbed, the nitric acid enters the mixed acid configuration tank 620, mixed acid is configured, and the mixed acid returns to the nitration reaction device 100 for recycling, i.e. the low-concentration waste acid generated in the nitration reaction process is recycled, and the lost nitric acid in the acidic nitration liquid a is also recycled, so that cost reduction and efficiency improvement are realized.
In another embodiment, the nitrochlorobenzene production system 10 capable of reducing the nitrate content in the wastewater further includes: and the wastewater treatment device 800 is connected with the wastewater treatment tank 430, and is used for treating the washing wastewater generated by the alkaline washing and rinsing device 400. The wastewater treatment device 800 comprises a resin adsorption component 810 and a Fenton reaction component 820 which are sequentially connected, so that the COD content and the chromaticity of wastewater are reduced by a resin adsorption method directly, the discharge requirement can be met after the COD content and the total nitrogen and ammonia nitrogen content of the wastewater are further reduced by a Fenton oxidation method, and the washing wastewater is prevented from being treated by adopting a high-energy-consumption evaporation and concentration mode.
In a preferred embodiment, in order to further improve the nitrogen stripping effect and reduce the nitric acid content of the nitrified liquid B, the nitrogen stripping device 200 includes a first venturi mixer 230 and a first gas-liquid separator 240, and a discharge end of the first venturi mixer 230 is connected to the first gas-liquid separator 240. The bottom of the first gas-liquid separator 240 is provided with a first forced circulation component 250, the discharge end of the first forced circulation component 250 is connected with the liquid phase inlet of the first venturi mixer 230, and the gas phase inlet of the first venturi mixer 230 is provided with a nitrogen feeding pipe 260.
The first forced circulation component 250 forcibly circulates the liquid phase in the first gas-liquid separator 240, and sufficiently mixes the liquid phase with the nitrogen entering the first venturi mixer 230 to repeatedly blow off the liquid phase, thereby improving the nitrogen blowing-off effect. Preferably, the first forced circulation module 250 includes a forced circulation pump 251 and a heater 252, the forced circulation pump 251 forcibly circulates the liquid phase in the first gas-liquid separator 240, and heats the liquid phase by the heater 252, and the outlet temperature of the heater 252 is maintained at 75 to 85 ℃ to improve the nitrogen stripping effect. Further, the outlet end of the first venturi mixer 230 is inserted below the liquid level of the liquid phase of the first gas-liquid separator 240, the gas-liquid mixture enters below the liquid level, gas-liquid separation and aeration are simultaneously performed, and nitrogen blows out nitric acid in the material in the process, so that the nitrogen stripping effect is further improved, the content of nitric acid in the nitrified liquid B is reduced, and the content of nitric acid in the nitrified liquid B obtained after stripping is detected to be less than 0.1%.
In another preferred embodiment, the nitric acid recovery device 600 comprises a second venturi mixer 630 and a second gas-liquid separator 640, and the discharge end of the second venturi mixer 630 is connected to the second gas-liquid separator 640. The bottom of second vapour and liquid separator 640 is provided with second forced circulation subassembly 650, the discharge end of second forced circulation subassembly 650 is connected the liquid phase inlet of second venturi mixer 630, the gaseous phase inlet of second venturi mixer 630 is connected contain nitric acid nitrogen gas discharging pipe 210.
The nitrogen gas that carries nitric acid vapour that produces in the nitrogen gas stripping device 200 is by the nitrogen gas discharging pipe 210 that contains nitric acid gets into the gaseous phase feed end of second venturi mixer 630, with by the concentrated sulfuric acid or the intensive spent acid intensive contact mixing that concentrated sulfuric acid feed pipe 610 got into absorb the nitric acid that carries in the nitrogen gas that contains nitric acid. After absorbing nitric acid, concentrated sulfuric acid or concentrated waste acid enters the mixed acid preparation tank 620 to prepare mixed acid for nitration reaction, so that the nitric acid is recycled.
In one embodiment, the nitrochlorobenzene production system 10 capable of reducing the nitrate content in the wastewater further includes: and a feed end of the nitrogen recovery device 900 is connected with a gas phase discharge end of the nitric acid recovery device 600, and a discharge end is connected with the nitrogen feeding pipe 260. After being absorbed by concentrated sulfuric acid, the generated nitrogen with low acid content is washed, dried and pressurized by the nitrogen recovery device 900, and then returns to the nitrogen stripping device 200 for recycling, so that the nitrogen loss is reduced. For example, the nitrogen recovery unit 900 is a caustic tower.
While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.
Claims (10)
1. A preparation method of nitrochlorobenzene capable of reducing the content of nitrate in wastewater is characterized by comprising the following steps:
a. nitration reaction: chlorobenzene and nitric acid are used as raw materials, and are reacted to generate acidic nitration liquid A under the catalysis of sulfuric acid;
b. nitrogen stripping: blowing nitrogen into the acidic nitrifying liquid A at a preset temperature, and carrying out stripping to obtain nitrifying liquid B and nitrogen containing nitric acid;
c. acid oil separation: carrying out acid-oil separation on the nitrifying liquid B to obtain nitrifying liquid C and waste acid;
d. alkali washing and water washing: after the nitrifying liquid C is contacted with a sodium hydroxide solution and subjected to alkali washing, the nitrifying liquid C is contacted with deionized water and subjected to water washing to obtain a neutral nitrifying liquid D and washing wastewater;
e. drying and separating: and drying and separating the neutral nitration liquid D to prepare the nitrochlorobenzene.
2. The method for preparing nitrochlorobenzene according to claim 1, capable of reducing the nitrate content in wastewater, further comprising the steps of:
f. and (3) recovering nitric acid: and (c) absorbing the nitric acid in the nitric acid-containing nitrogen gas obtained in the step b by using concentrated sulfuric acid, wherein the obtained concentrated sulfuric acid containing the nitric acid is used for preparing mixed acid for digestion reaction.
3. The method for preparing nitrochlorobenzene according to claim 1, capable of reducing the nitrate content in wastewater, further comprising the steps of:
g. waste acid concentration: concentrating the waste acid obtained in the step c to obtain concentrated waste acid;
h. and (3) recycling waste acid: and (c) absorbing the nitric acid in the nitric acid-containing nitrogen gas obtained in the step (b) by using concentrated waste acid, and using the obtained concentrated waste acid containing the nitric acid to prepare mixed acid for digestion reaction.
4. The method for preparing nitrochlorobenzene according to claim 1, capable of reducing the nitrate content in wastewater, further comprising the steps of:
i. wastewater treatment: and d, sequentially carrying out resin adsorption and oxidation treatment on the washing wastewater obtained in the step d, and discharging the washing wastewater up to the standard.
5. A nitrochlorobenzene preparation system capable of reducing the content of nitrate in wastewater is characterized by comprising:
the nitration reaction device is used for reacting chlorobenzene and nitric acid serving as raw materials under the catalysis of sulfuric acid to generate acidic nitration liquid A;
the feed end of the nitrogen stripping device is connected with the discharge end of the nitration reaction device and is used for blowing nitrogen into the acidic nitration liquid A at a preset temperature to carry out stripping so as to obtain nitration liquid B and nitrogen containing nitric acid; the top of the nitrogen stripping device is provided with a nitric acid-containing nitrogen discharging pipe, and the bottom of the nitrogen stripping device is provided with a nitrifying liquid B discharging pipe;
the feed end of the acid-oil separation device is connected with the nitrifying liquid B discharge pipe and is used for carrying out acid-oil separation on the nitrifying liquid B to obtain nitrifying liquid C and waste acid; the top of the acid-oil separation device is provided with a nitrifying liquid C discharge pipe, and the bottom of the acid-oil separation device is provided with a waste acid discharge pipe;
the alkali washing and water washing device is used for sequentially carrying out alkali washing and water washing on the nitrifying liquid C to obtain neutral nitrifying liquid D and washing wastewater; the alkaline washing and water washing device comprises an alkaline washing kettle and a water washing kettle which are sequentially connected, wherein the feed end of the alkaline washing kettle is connected with the nitrifying liquid C discharge pipe, and the bottom of the alkaline washing kettle is connected with a washing wastewater tank; the feed end of the water washing kettle is connected with the oil phase discharge end of the alkaline washing kettle, and the bottom of the water washing kettle is connected with the washing wastewater tank; and
and the feed end of the drying and separating device is connected with the oil phase discharge end of the washing kettle and is used for drying and separating the neutral nitration liquid D to prepare nitrochlorobenzene.
6. The nitrochlorobenzene production system according to claim 5, further comprising:
the nitric acid recovery device is used for absorbing nitric acid in the nitric acid-containing nitrogen obtained from the nitrogen stripping device by using concentrated sulfuric acid to obtain concentrated sulfuric acid containing nitric acid; the gas phase feed end of the nitric acid recovery device is connected with the nitric acid-containing nitrogen discharge pipe, and a concentrated sulfuric acid feed pipe is arranged on the nitric acid recovery device; the discharge end of the nitric acid recovery device is connected with a mixed acid preparation tank.
7. The nitrochlorobenzene production system according to claim 6, further comprising:
the feed end of the waste acid concentrating device is connected with the waste acid discharge pipe and is used for concentrating the waste acid obtained in the acid oil separation device to obtain concentrated waste acid;
and the discharge end of the concentrated waste acid of the waste acid concentrating device is connected with the concentrated sulfuric acid feed pipe so as to utilize the concentrated waste acid to absorb nitric acid in the nitric acid-containing nitrogen obtained from the nitrogen stripping device, and the obtained concentrated waste acid containing the nitric acid is used for preparing mixed acid for digestion reaction.
8. The nitrochlorobenzene production system according to claim 5, further comprising:
the wastewater treatment device is connected with the wastewater treatment tank and is used for treating the washing wastewater generated by the alkaline washing and rinsing device; the wastewater treatment device comprises a resin adsorption component and a Fenton reaction component which are connected in sequence.
9. The nitrochlorobenzene preparation system capable of reducing the nitrate content in wastewater according to claim 5, wherein the nitrogen stripping device comprises a first venturi mixer and a first gas-liquid separator, and a discharge end of the first venturi mixer is connected with the first gas-liquid separator; the bottom of first vapour and liquid separator is provided with first forced circulation subassembly, the discharge end of first forced circulation subassembly is connected the liquid phase entry of first venturi mixer, the gaseous phase entry of first venturi mixer is provided with the nitrogen gas inlet pipe.
10. The nitrochlorobenzene preparation system according to claim 6, wherein the nitric acid recovery unit comprises a second venturi mixer and a second gas-liquid separator, and a discharge end of the second venturi mixer is connected to the second gas-liquid separator; the bottom of second vapour and liquid separator is provided with the second forced circulation subassembly, the discharge end of second forced circulation subassembly is connected the liquid phase entry of second venturi mixer, the gaseous phase entry of second venturi mixer is connected contain nitric acid nitrogen gas discharging pipe.
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