CN113912470A - Method and device for recovering nitric acid - Google Patents
Method and device for recovering nitric acid Download PDFInfo
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- CN113912470A CN113912470A CN202010658576.2A CN202010658576A CN113912470A CN 113912470 A CN113912470 A CN 113912470A CN 202010658576 A CN202010658576 A CN 202010658576A CN 113912470 A CN113912470 A CN 113912470A
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- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 title claims abstract description 84
- 229910017604 nitric acid Inorganic materials 0.000 title claims abstract description 84
- 238000000034 method Methods 0.000 title claims abstract description 49
- PPBRXRYQALVLMV-UHFFFAOYSA-N Styrene Chemical compound C=CC1=CC=CC=C1 PPBRXRYQALVLMV-UHFFFAOYSA-N 0.000 claims abstract description 170
- 238000000926 separation method Methods 0.000 claims abstract description 149
- 238000005406 washing Methods 0.000 claims abstract description 86
- 239000002253 acid Substances 0.000 claims abstract description 80
- 239000002351 wastewater Substances 0.000 claims abstract description 54
- 239000003513 alkali Substances 0.000 claims abstract description 31
- 229930195733 hydrocarbon Natural products 0.000 claims abstract description 27
- 150000002430 hydrocarbons Chemical class 0.000 claims abstract description 27
- 238000004064 recycling Methods 0.000 claims abstract description 10
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 36
- 238000000605 extraction Methods 0.000 claims description 35
- 238000010992 reflux Methods 0.000 claims description 22
- 101000623895 Bos taurus Mucin-15 Proteins 0.000 claims description 16
- 239000004215 Carbon black (E152) Substances 0.000 claims description 14
- 238000011084 recovery Methods 0.000 claims description 11
- 238000004519 manufacturing process Methods 0.000 claims description 5
- 239000003518 caustics Substances 0.000 claims description 3
- JLBJTVDPSNHSKJ-UHFFFAOYSA-N 4-Methylstyrene Chemical compound CC1=CC=C(C=C)C=C1 JLBJTVDPSNHSKJ-UHFFFAOYSA-N 0.000 claims description 2
- CTQNGGLPUBDAKN-UHFFFAOYSA-N O-Xylene Chemical compound CC1=CC=CC=C1C CTQNGGLPUBDAKN-UHFFFAOYSA-N 0.000 claims description 2
- 238000005554 pickling Methods 0.000 claims description 2
- 239000008096 xylene Substances 0.000 claims description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 abstract description 10
- 229910052757 nitrogen Inorganic materials 0.000 abstract description 5
- 239000000126 substance Substances 0.000 abstract description 2
- 238000004140 cleaning Methods 0.000 description 10
- 239000007788 liquid Substances 0.000 description 7
- 239000002699 waste material Substances 0.000 description 6
- 229910052770 Uranium Inorganic materials 0.000 description 4
- 239000007789 gas Substances 0.000 description 4
- JFALSRSLKYAFGM-UHFFFAOYSA-N uranium(0) Chemical compound [U] JFALSRSLKYAFGM-UHFFFAOYSA-N 0.000 description 4
- 239000002585 base Substances 0.000 description 3
- 238000010521 absorption reaction Methods 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 150000007522 mineralic acids Chemical class 0.000 description 2
- 238000006386 neutralization reaction Methods 0.000 description 2
- 230000003472 neutralizing effect Effects 0.000 description 2
- 238000000746 purification Methods 0.000 description 2
- 229910002651 NO3 Inorganic materials 0.000 description 1
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000004880 explosion Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 description 1
- 239000003758 nuclear fuel Substances 0.000 description 1
- 150000007524 organic acids Chemical class 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000004065 wastewater treatment Methods 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C7/00—Purification; Separation; Use of additives
- C07C7/148—Purification; Separation; Use of additives by treatment giving rise to a chemical modification of at least one compound
- C07C7/17—Purification; Separation; Use of additives by treatment giving rise to a chemical modification of at least one compound with acids or sulfur oxides
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B21/00—Nitrogen; Compounds thereof
- C01B21/20—Nitrogen oxides; Oxyacids of nitrogen; Salts thereof
- C01B21/38—Nitric acid
- C01B21/46—Purification; Separation ; Stabilisation
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C7/00—Purification; Separation; Use of additives
- C07C7/005—Processes comprising at least two steps in series
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C7/00—Purification; Separation; Use of additives
- C07C7/04—Purification; Separation; Use of additives by distillation
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C7/00—Purification; Separation; Use of additives
- C07C7/148—Purification; Separation; Use of additives by treatment giving rise to a chemical modification of at least one compound
- C07C7/14833—Purification; Separation; Use of additives by treatment giving rise to a chemical modification of at least one compound with metals or their inorganic compounds
- C07C7/1485—Purification; Separation; Use of additives by treatment giving rise to a chemical modification of at least one compound with metals or their inorganic compounds oxides; hydroxides; salts
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- Engineering & Computer Science (AREA)
- Analytical Chemistry (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Water Supply & Treatment (AREA)
- Inorganic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
The invention belongs to the field of chemical industry, and particularly discloses a method and a device for recovering nitric acid, wherein the method comprises the step of sending acid-containing wastewater into a separation tower to sequentially discharge hydrocarbons and nitric acid, wherein the acid-containing wastewater comprises 10-70 wt% of nitric acid and hydrocarbons with the content of not more than 10 wt%. The method for recycling the nitric acid is applied to a crude styrene decoloring process, and the acid-containing wastewater generated in the acid washing process of the crude styrene decoloring process is separated and utilized again, so that the recycling of the nitric acid and the styrene can be realized, the alkali consumption can be reduced, the wastewater discharge amount of the existing crude styrene decoloring device can be reduced, the total nitrogen discharge amount of the wastewater of the existing crude styrene decoloring device is greatly reduced, and the disposability of the wastewater in the crude styrene decoloring process is improved.
Description
Technical Field
The invention belongs to the field of chemical industry, and particularly relates to a method and a device for recovering nitric acid.
Background
At present, a crude styrene decoloring unit of a domestic styrene extraction device has two processes of inorganic acid decoloring and organic acid decoloring, wherein the nitric acid content of nitric acid wastewater generated by the inorganic acid decoloring process is high, the part of nitric acid is further neutralized by alkaline liquor and then becomes nitrate to enter a wastewater treatment plant for further treatment, the discharge of the acid-containing wastewater not only causes the waste of nitric acid, but also brings the waste of neutralized alkaline liquor, and the treatment difficulty of the nitrogen-containing salt wastewater generated after neutralization is high.
CN201310413412.3 relates to a dilute nitric acid recovery method, which comprises the following steps: feeding dilute nitric acid with the concentration of 3-8% into the middle of a rectifying tower, feeding steam evaporated from the top of the rectifying tower into a heat exchanger to exchange heat with tail gas at 20 ℃ from an absorption tower, heating the tail gas after heat exchange by using high-temperature NOx, and feeding the tail gas into a tail gas expander to recover energy; the water vapor forms condensate liquid during heat exchange, part of the condensate liquid is sent to the top of the rectifying tower to be used as reflux liquid, and the other part of the condensate liquid is used as water for the nitric acid absorption tower; and nitric acid with the concentration of more than 35% is formed at the bottom of the rectifying tower and is sent back to the direct nitric acid system to process concentrated nitric acid.
CN201611217555.7 relates to a technological method and a device for recycling nitric acid in uranium-containing waste liquid in uranium purification conversion and nuclear fuel post-treatment industries. According to the invention, the nitric acid and water in the uranium-containing acidic waste liquid are recovered for reuse by the process method for recovering the nitric acid through vacuum rectification, so that the waste of the nitric acid is avoided, the volume of the waste liquid is greatly reduced, the risks of over-quick corrosion of equipment and red oil explosion are reduced, and the purposes of reducing the production cost of uranium purification, protecting the environment, reducing emission and improving the operation safety are achieved.
It can be seen from the techniques disclosed in the above patent applications that the existing nitric acid recovery methods only achieve the concentration of nitric acid or the removal of impurities from nitric acid, and do not involve the recovery of products in nitric acid.
Disclosure of Invention
The invention aims to provide a method and a device for recovering nitric acid, which can realize the recovery of nitric acid and hydrocarbons in acid-containing wastewater, can reduce the alkali consumption when being applied to a crude styrene decoloring process, and can reduce the wastewater discharge of the existing crude styrene decoloring device, thereby greatly reducing the total nitrogen discharge of the wastewater of the existing crude styrene decoloring device and improving the disposability of the wastewater of the device.
In order to achieve the above object, a first aspect of the present invention provides a method for recovering nitric acid, characterized by comprising:
the method comprises the following steps of recovering nitric acid and hydrocarbons in acid-containing wastewater in one of the following three ways, wherein the acid-containing wastewater comprises 10-70 wt% of nitric acid and no more than 10 wt% of hydrocarbons:
the first method is as follows: sending the acid-containing wastewater to a separation tower I to separate a light component I and a heavy component I, continuously sending the separated light component I to a separation tower II, and further separating a light component III and nitric acid;
the second method comprises the following steps: sending the acid-containing wastewater to a separation tower I to separate a light component III and a heavy component II, and continuously sending the separated heavy component II to a separation tower II to further separate nitric acid and the heavy component I;
the third method comprises the following steps: sending the acid-containing wastewater to a separation tower I to separate a light component IV and a heavy component III, sending the separated heavy component III to a separation tower II, continuously separating a light component II and a heavy component I, continuously sending the light component II to the separation tower I, and further separating nitric acid and a light component V.
The light component and the heavy component separated by the method are mainly different in the content of hydrocarbons, nitric acid, water and heavy tar, and the light component I contains 1-20 wt% of hydrocarbons, 30-60 wt% of water and 30-60 wt% of nitric acid; the light component II contains 30-70 wt% of water and 30-70 wt% of nitric acid; the light component III contains 10-50 wt% of hydrocarbon and 50-90 wt% of water; the light component IV contains 30-90 wt% of hydrocarbon and 10-70 wt% of water; the light component V contains 95 to 99.9 wt% of water and 0.1 to 5 wt% of hydrocarbons. Correspondingly, the separated heavy component I contains 80-100 wt% of heavy tar, and the heavy component II contains 60-70 wt% of nitric acid and 30-40 wt% of water; the heavy component III contains 30-70 wt% of nitric acid and 30-70 wt% of water.
According to the invention, preferably, the content of nitric acid in the acid-containing wastewater is 30-65 wt%, further preferably, the content of nitric acid is 40-60 wt%, the content of hydrocarbons is 0.01-10 wt%, and the content of water is 30-70 wt%; the hydrocarbon is at least one of styrene, xylene and methyl styrene; the acid-containing wastewater comes from a styrene extraction device. In the first recovery mode of the present invention, preferably, the number of theoretical plates of the separation column i is 1 to 20, and the theoretical feed plates are from the 1 st plate to the 15 th plate; the mass reflux ratio of the separation tower I is 1-5, the operation pressure of the top of the separation tower I is 5-120 kPaA, the operation temperature is 50-130 ℃, and further preferably, the operation pressure of the top of the separation tower I is 5-30 kPaA, and the operation temperature is 50-100 ℃;
the number of theoretical plates of the separation tower II is 1-20, and the theoretical feeding plates are from the 1 st plate to the 15 th plate; the mass reflux ratio of the separation tower II is 1-5, the operation pressure of the top of the separation tower II is 5-120 kPaA, the operation temperature is 30-110 ℃, and further preferably, the operation pressure of the top of the separation tower II is 60-120 kPaA, and the operation temperature is 80-110 ℃.
In the second recovery mode of the present invention, preferably, the number of theoretical plates of the separation column i is 1 to 20, and the theoretical feed plates are from the 1 st plate to the 15 th plate; the mass reflux ratio of the separation tower I is 1-5, the operation pressure of the top of the separation tower I is 5-120 kPaA, the operation temperature is 30-110 ℃, and further preferably, the operation pressure of the top of the separation tower I is 5-30 kPaA, and the operation temperature is 30-70 ℃;
the number of theoretical plates of the separation tower II is 1-20, and the theoretical feeding plates are from the 1 st plate to the 15 th plate; the mass reflux ratio of the separation tower II is 1-5, the operation pressure of the top of the separation tower II is 5-120 kPaA, the operation temperature is 50-130 ℃, and further preferably, the operation pressure of the top of the separation tower II is 5-30 kPaA, and the operation temperature is 50-100 ℃.
In the third recovery mode of the present invention, preferably, the number of theoretical plates of the separation column i is 1 to 20, and the theoretical feed plates are from the 1 st plate to the 15 th plate; the mass reflux ratio of the separation tower I is 1-5, the operation pressure of the top of the separation tower I is 5-120 kPaA, the operation temperature is 20-110 ℃, and further preferably, the operation pressure of the top of the separation tower I is 5-30 kPaA, and the operation temperature is 20-70 ℃;
the number of theoretical plates of the separation tower II is 1-20, and the theoretical feeding plates are from the 1 st plate to the 15 th plate; the mass reflux ratio of the separation tower II is 1-5, the operation pressure of the top of the separation tower II is 5-120 kPaA, the operation temperature is 50-130 ℃, and further preferably, the operation pressure of the top of the separation tower II is 5-30 kPaA, and the operation temperature is 50-100 ℃;
the number of theoretical plates of the separation tower III is 1-20, and the theoretical feeding plates are from the 1 st plate to the 15 th plate; the mass reflux ratio of the separation tower III is 1-5, the operation pressure of the top of the separation tower III is 5-120 kPaA, the operation temperature is 30-110 ℃, and further preferably, the operation pressure of the top of the separation tower III is 80-120 kPaA, and the operation temperature is 90-110 ℃.
The invention provides a device for recovering nitric acid, which comprises an acid-containing wastewater feeding pipeline, a nitric acid extraction pipeline, a hydrocarbon extraction pipeline, a separation tower I, a separation tower II and an optional separation tower III;
the acid-containing wastewater feeding pipeline is connected with the separation tower I,
the top of the separation tower I is connected with a separation tower II, the top of the separation tower II is connected with a hydrocarbon extraction pipeline, and the bottom of the separation tower II is connected with a nitric acid extraction pipeline;
or the top of the separation tower I is connected with a hydrocarbon extraction pipeline, the bottom of the separation tower I is connected with a separation tower II, and the top of the separation tower II is connected with a nitric acid extraction pipeline;
or the top of the separation tower I is connected with a hydrocarbon extraction pipeline, the bottom of the separation tower I is connected with a separation tower II, the top of the separation tower II is connected with a separation tower III, and the bottom of the separation tower III is connected with a nitric acid extraction pipeline.
In a third aspect, the present invention provides a process for decoloring crude styrene, the process comprising: and (3) sequentially carrying out acid washing, alkali washing and water washing on the crude styrene to obtain decolored styrene, and recovering acid-containing wastewater in the acid washing process by using the method for recovering nitric acid to obtain styrene and nitric acid.
The acid washing, alkali washing and water washing processes of the crude styrene involved in the present invention are conventional techniques in the art, and are not particularly limited, and those skilled in the art can confirm the operation conditions according to the conventional operations.
In the invention, the recovered nitric acid can be used as a decoloring agent and sent to the pickling unit for recycling. In order to further recover the raw materials, the styrene obtained from the recovery may also be sent to a caustic wash unit.
The fourth aspect of the present invention provides an apparatus for decoloring crude styrene, the apparatus comprising: a crude styrene feeding pipeline, an acid washing unit, an alkali washing unit, a water washing unit, a decolored styrene extraction pipeline and the device for recovering nitric acid;
the device comprises a crude styrene feeding pipeline, an acid washing unit, an alkali washing unit, a water washing unit and a decolored styrene extraction pipeline, wherein the crude styrene feeding pipeline, the acid washing unit, the alkali washing unit, the water washing unit and the decolored styrene extraction pipeline are sequentially connected, and the acid washing unit is connected with the nitric acid recovery device through the acid-containing wastewater feeding pipeline.
The acid washing unit, the alkali washing unit and the water washing unit are not particularly limited and are all conventional in the field.
According to the invention, preferably, the nitric acid production line is connected with the acid washing unit, and the hydrocarbon production line is connected with the alkaline washing unit.
Compared with the prior art, the invention has the following advantages:
1) the invention can realize the recycling of nitric acid and hydrocarbons and reduce the discharge of acid-containing wastewater by recycling the acid-containing wastewater.
2) The invention can realize the recovery of nitric acid and styrene, reduce the consumption of alkali, and reduce the wastewater discharge of the existing crude styrene decoloring device, thereby greatly reducing the total nitrogen discharge of the wastewater of the existing crude styrene decoloring device and improving the disposability of the wastewater in the crude styrene decoloring process.
Additional features and advantages of the invention will be set forth in the detailed description which follows.
Drawings
The above and other objects, features and advantages of the present invention will become more apparent by describing in more detail exemplary embodiments thereof with reference to the attached drawings, in which like reference numerals generally represent like parts throughout.
Figure 1 shows a schematic of the current crude styrene decolouration process scheme of the present invention.
FIG. 2 shows a schematic flow chart of the crude styrene decoloring process in example 1 of the present invention.
FIG. 3 shows a schematic flow chart of the crude styrene decoloring process in example 2 of the present invention.
FIG. 4 shows a schematic flow chart of the crude styrene decoloring process in example 3 of the present invention.
Description of reference numerals:
1. an acid washing unit; 2. an alkaline washing unit; 3. a water washing unit; 4. decolorizing styrene; 5. acid-containing wastewater; 6. crude styrene; 7. a separation tower I; 8. a separation tower II; 9. a light component I; 10. a heavy component I; 11. a light component III; 12. nitric acid; 13. a heavy component II; 14. a light component IV; 15. a separation column III; 16. a heavy component III; 17. a light component II; 18. a light fraction V; 19. and an acid-base neutralization unit.
Detailed Description
Preferred embodiments of the present invention will be described in more detail below. While the following describes preferred embodiments of the present invention, it should be understood that the present invention may be embodied in various forms and should not be limited by the embodiments set forth herein.
The crude styrene related in the following embodiments of the invention comes from an extraction unit of a styrene extraction device, and contains styrene and other impurities, wherein the styrene content is 95-99.99 wt%.
Example 1
A device for decoloring crude styrene (as shown in figure 2) comprises a crude styrene feeding pipeline, an acid washing unit 1, an alkali washing unit 2, a water washing unit 3, a decolored styrene extraction pipeline, a separation tower I7 and a separation tower II 8, wherein the crude styrene feeding pipeline, the acid washing unit 1, the alkali washing unit 2, the water washing unit 3 and the decolored styrene extraction pipeline are sequentially connected,
the acid cleaning unit 1 is connected with the separation tower I7 through an acid-containing wastewater feeding pipeline, the top of the separation tower I7 is connected with the separation tower II 8, the top of the separation tower II is connected with the alkaline cleaning unit 2, and the bottom of the separation tower is connected with the acid cleaning unit 1.
The device is used for recycling nitric acid, specifically, crude styrene 6 is sequentially subjected to acid washing, alkali washing and water washing to obtain decolored styrene 4, acid-containing wastewater 5 in the acid washing process is sent to a separation tower I7 to separate a heavy component I10 and a light component I9, the separated light component I9 is continuously sent to a separation tower II 8 to further separate a light component III 11 and nitric acid 12, the light component III 11 is sent to an alkali washing unit 2, and the nitric acid 12 is sent to an acid washing unit 1.
Wherein the theoretical plate number of the separation tower I is 10, the theoretical feed plate is the 5 th plate, the mass reflux ratio is 2, the operation pressure at the top of the tower is 5kPaA, and the operation temperature is 50 ℃;
the theoretical plate number of the separation tower II is 10, the theoretical feeding plate is the 5 th plate, the mass reflux ratio is 2, the operation pressure at the top of the tower is 70kPaA, and the operation temperature is 90 ℃.
Example 2
A device for decoloring crude styrene (as shown in figure 3) comprises a crude styrene feeding pipeline, an acid washing unit 1, an alkali washing unit 2, a water washing unit 3, a decolored styrene extraction pipeline, a separation tower I7 and a separation tower II 8, wherein the crude styrene feeding pipeline, the acid washing unit 1, the alkali washing unit 2, the water washing unit 3 and the decolored styrene extraction pipeline are sequentially connected,
the acid cleaning unit 1 is connected with the separation tower I7 through an acid-containing wastewater feeding pipeline, the top of the separation tower I7 is connected with the alkaline cleaning unit 2, the bottom of the separation tower is connected with the separation tower II 8, and the top of the separation tower II 8 is connected with the acid cleaning unit 1.
The device is used for recycling nitric acid, specifically, crude styrene 6 is sequentially subjected to acid washing, alkali washing and water washing to obtain decolored styrene 4, acid-containing wastewater 5 in the acid washing process is sent to a separation tower I7, a light component III 11 and a heavy component II 13 are separated out, the separated light component III 11 is sent to an alkali washing unit 2, the heavy component II 13 is continuously sent to a separation tower II 8, nitric acid 12 and a heavy component I10 are further separated out, and the nitric acid 12 is sent to an acid washing unit 1. Wherein the theoretical plate number of the separation tower I is 10, the theoretical feed plate is the 5 th plate, the mass reflux ratio is 2, the operation pressure at the top of the tower is 5kPaA, and the operation temperature is 30 ℃;
the theoretical plate number of the separation tower II is 10, the theoretical feeding plate is the 5 th plate, the mass reflux ratio is 2, the operation pressure at the top of the tower is 5kPaA, and the operation temperature is 50 ℃.
Example 3
A device for decoloring crude styrene (as shown in figure 4) comprises a crude styrene feeding pipeline, an acid washing unit 1, an alkali washing unit 2, a water washing unit 3, a decolored styrene extraction pipeline, a separation tower I7, a separation tower II 8 and a separation tower III 15, wherein the crude styrene feeding pipeline, the acid washing unit 1, the alkali washing unit 2, the water washing unit 3 and the decolored styrene extraction pipeline are sequentially connected,
the acid cleaning unit 1 is connected with the separation tower I7 through an acid-containing wastewater feeding pipeline, the top of the separation tower I7 is connected with the alkaline cleaning unit 2, the bottom of the separation tower is connected with the separation tower II 8, the top of the separation tower II 8 is connected with the separation tower III 15, the top of the separation tower III 15 is connected with the alkaline cleaning unit 2, and the bottom of the separation tower is connected with the acid cleaning unit 1.
The device is used for recycling nitric acid, specifically, crude styrene 6 is sequentially subjected to acid washing, alkali washing and water washing to obtain decolored styrene 4, acid-containing wastewater 5 in the acid washing process is sent to a separation tower I7 to separate a light component IV 14 and a heavy component III 16, the separated light component IV 14 is sent to an alkali washing unit 2, the heavy component III 16 is continuously sent to a separation tower II 8 to further separate a light component II 17 and a heavy component I10, the light component II 17 is continuously sent to a separation tower III 15 to further separate nitric acid 12 and a light component V18, and the light component V18 is sent to an alkali washing unit 2.
Wherein the theoretical plate number of the separation tower I is 10, the theoretical feed plate is the 5 th plate, the mass reflux ratio is 2, the operation pressure at the top of the tower is 5kPaA, and the operation temperature is 20 ℃;
the theoretical plate number of the separation tower II is 10, the theoretical feeding plate is the 5 th plate, the mass reflux ratio is 2, the operation pressure at the top of the tower is 5kPaA, and the operation temperature is 50 ℃;
the theoretical plate number of the separation tower III is 10, the theoretical feeding plate is the 5 th plate, the mass reflux ratio is 2, the operation pressure at the top of the tower is 100kPaA, and the operation temperature is 100 ℃.
Comparative example
The existing crude styrene decoloring device (shown in figure 1) comprises a crude styrene feeding pipeline, an acid washing unit 1, an alkali washing unit 2, a water washing unit 3, an acid-base neutralizing unit 21 and a decolored styrene extraction pipeline, wherein the crude styrene feeding pipeline, the acid washing unit 1, the alkali washing unit 2, the water washing unit 3 and the decolored styrene extraction pipeline are sequentially connected, crude styrene 6 sequentially undergoes acid washing, alkali washing and water washing to obtain decolored styrene 4, and the acid washing unit 1 is connected with the acid-base neutralizing unit 19 through an acid-containing wastewater feeding pipeline.
Examples 1-3 and comparative examples were conducted in a pilot test apparatus and the results are shown in Table 1:
TABLE 1
As can be seen from the comparison results in table 1, the process for recovering nitric acid provided by the present invention can reduce the acid consumption of the apparatus by 57%, reduce the alkali consumption by 54%, reduce the wastewater discharge by 58%, and reduce the total nitrogen discharge of wastewater by 58%, thereby realizing the reuse of nitric acid wastewater, recovering nitric acid, recovering styrene, reducing the alkali consumption, reducing the wastewater discharge of the existing crude styrene decolorizer, greatly reducing the total nitrogen discharge of wastewater of the existing crude styrene decolorizer, and improving the disposability of wastewater of the apparatus.
Having described embodiments of the present invention, the foregoing description is intended to be exemplary, not exhaustive, and not limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments.
Claims (10)
1. A method for recovering nitric acid, the method comprising:
the method comprises the following steps of recovering nitric acid and hydrocarbons in acid-containing wastewater in one of the following three ways, wherein the acid-containing wastewater comprises 10-70 wt% of nitric acid and no more than 10 wt% of hydrocarbons:
the first method is as follows: sending the acid-containing wastewater to a separation tower I to separate a light component I and a heavy component I, continuously sending the separated light component I to a separation tower II, and further separating a light component III and nitric acid;
the second method comprises the following steps: sending the acid-containing wastewater to a separation tower I to separate a light component III and a heavy component II, and continuously sending the separated heavy component II to a separation tower II to further separate nitric acid and the heavy component I;
the third method comprises the following steps: sending the acid-containing wastewater to a separation tower I to separate a light component IV and a heavy component III, sending the separated heavy component III to a separation tower II, continuously separating a light component II and a heavy component I, continuously sending the light component II to the separation tower III, and further separating a light component V and nitric acid.
2. The method as claimed in claim 1, wherein, in the first mode, the theoretical plate number of the separation tower I is 1-20, and the theoretical feeding plates are from 1 st plate to 15 th plate; the mass reflux ratio of the separation tower I is 1-5, the operation pressure of the top of the separation tower I is 5-120 kPaA, the operation temperature is 50-130 ℃, and preferably, the operation pressure of the top of the separation tower I is 5-30 kPaA, and the operation temperature is 50-100 ℃;
the number of theoretical plates of the separation tower II is 1-20, and the theoretical feeding plates are from the 1 st plate to the 15 th plate; the mass reflux ratio of the separation tower II is 1-5, the operation pressure of the top of the separation tower II is 5-120 kPaA, the operation temperature is 30-110 ℃, and preferably, the operation pressure of the top of the separation tower II is 60-120 kPaA, and the operation temperature is 80-110 ℃.
3. The method as claimed in claim 1, wherein, in the second mode, the theoretical plate number of the separation tower I is 1-20, and the theoretical feeding plates are from 1 st plate to 15 th plate; the mass reflux ratio of the separation tower I is 1-5, the operation pressure of the top of the separation tower I is 5-120 kPaA, the operation temperature is 30-110 ℃, and preferably, the operation pressure of the top of the separation tower I is 5-30 kPaA, and the operation temperature is 30-70 ℃;
the number of theoretical plates of the separation tower II is 1-20, and the theoretical feeding plates are from the 1 st plate to the 15 th plate; the mass reflux ratio of the separation tower II is 1-5, the operation pressure of the top of the separation tower II is 5-120 kPaA, the operation temperature is 50-130 ℃, and preferably, the operation pressure of the top of the separation tower II is 5-30 kPaA, and the operation temperature is 50-100 ℃.
4. The method as claimed in claim 1, wherein, in the third mode, the theoretical plate number of the separation tower I is 1-20, and the theoretical feeding plates are from 1 st plate to 15 th plate; the mass reflux ratio of the separation tower I is 1-5, the operation pressure of the top of the separation tower I is 5-120 kPaA, the operation temperature is 20-110 ℃, and preferably, the operation pressure of the top of the separation tower I is 5-30 kPaA, and the operation temperature is 20-70 ℃;
the number of theoretical plates of the separation tower II is 1-20, and the theoretical feeding plates are from the 1 st plate to the 15 th plate; the mass reflux ratio of the separation tower II is 1-5, the operation pressure of the top of the separation tower II is 5-120 kPaA, the operation temperature is 50-130 ℃, and preferably, the operation pressure of the top of the separation tower II is 5-30 kPaA, and the operation temperature is 50-100 ℃;
the number of theoretical plates of the separation tower III is 1-20, and the theoretical feeding plates are from the 1 st plate to the 15 th plate; the mass reflux ratio of the separation tower III is 1-5, the operation pressure of the top of the separation tower III is 5-120 kPaA, the operation temperature is 30-110 ℃, and preferably, the operation pressure of the top of the separation tower III is 80-120 kPaA, and the operation temperature is 90-110 ℃.
5. The method according to any one of claims 1 to 4, wherein the acid-containing wastewater contains 30 to 65 wt% of nitric acid, preferably 40 to 60 wt% of nitric acid, 0.01 to 10 wt% of hydrocarbons and 30 to 70 wt% of water; the hydrocarbon is at least one of styrene, xylene and methyl styrene; the acid-containing wastewater comes from a styrene extraction device.
6. The device for recovering the nitric acid is characterized by comprising an acid-containing wastewater feeding pipeline, a nitric acid extraction pipeline, a hydrocarbon extraction pipeline, a separation tower I, a separation tower II and an optional separation tower III;
the acid-containing wastewater feeding pipeline is connected with the separation tower I,
the top of the separation tower I is connected with a separation tower II, the top of the separation tower II is connected with a hydrocarbon extraction pipeline, and the bottom of the separation tower II is connected with a nitric acid extraction pipeline;
or the top of the separation tower I is connected with a hydrocarbon extraction pipeline, the bottom of the separation tower I is connected with a separation tower II, and the top of the separation tower II is connected with a nitric acid extraction pipeline;
or the top of the separation tower I is connected with a hydrocarbon extraction pipeline, the bottom of the separation tower I is connected with a separation tower II, the top of the separation tower II is connected with a separation tower III, and the bottom of the separation tower III is connected with a nitric acid extraction pipeline.
7. A process for decolouring crude styrene, which comprises: the method comprises the steps of sequentially carrying out acid washing, alkali washing and water washing on crude styrene to obtain decolored styrene, and recycling acid-containing wastewater in the acid washing process by using the method of any one of claims 1 to 5 to obtain styrene and nitric acid.
8. The process of claim 7, wherein the recovered styrene is sent to a caustic wash unit and the recovered nitric acid is sent to a pickling unit.
9. An apparatus for decolouring crude styrene, said apparatus comprising: a crude styrene feeding pipeline, an acid washing unit, an alkali washing unit, a water washing unit, a decolored styrene extraction pipeline and the device for recovering nitric acid in claim 6;
the device comprises a crude styrene feeding pipeline, an acid washing unit, an alkali washing unit, a water washing unit and a decolored styrene extraction pipeline, wherein the crude styrene feeding pipeline, the acid washing unit, the alkali washing unit, the water washing unit and the decolored styrene extraction pipeline are sequentially connected, and the acid washing unit is connected with the nitric acid recovery device through the acid-containing wastewater feeding pipeline.
10. The apparatus of claim 9, wherein the nitric acid production line is connected to the acid wash unit and the hydrocarbon production line is connected to the caustic wash unit.
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