CN117185591B - Denitrification method and device for caprolactam wastewater - Google Patents
Denitrification method and device for caprolactam wastewater Download PDFInfo
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- JBKVHLHDHHXQEQ-UHFFFAOYSA-N epsilon-caprolactam Chemical compound O=C1CCCCCN1 JBKVHLHDHHXQEQ-UHFFFAOYSA-N 0.000 title claims abstract description 100
- 238000000034 method Methods 0.000 title claims abstract description 77
- 239000002351 wastewater Substances 0.000 title claims abstract description 77
- JHIVVAPYMSGYDF-UHFFFAOYSA-N cyclohexanone Chemical compound O=C1CCCCC1 JHIVVAPYMSGYDF-UHFFFAOYSA-N 0.000 claims abstract description 80
- 239000002699 waste material Substances 0.000 claims abstract description 58
- 239000003513 alkali Substances 0.000 claims abstract description 49
- 238000004062 sedimentation Methods 0.000 claims abstract description 48
- 238000006460 hydrolysis reaction Methods 0.000 claims abstract description 44
- 230000007062 hydrolysis Effects 0.000 claims abstract description 41
- 239000010802 sludge Substances 0.000 claims abstract description 36
- 230000003647 oxidation Effects 0.000 claims abstract description 26
- 238000007254 oxidation reaction Methods 0.000 claims abstract description 26
- 238000002156 mixing Methods 0.000 claims abstract description 22
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 20
- 238000006243 chemical reaction Methods 0.000 claims abstract description 19
- 238000006396 nitration reaction Methods 0.000 claims abstract description 13
- 239000007788 liquid Substances 0.000 claims abstract description 12
- 239000013049 sediment Substances 0.000 claims abstract description 9
- 238000001816 cooling Methods 0.000 claims abstract description 5
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 70
- 238000003756 stirring Methods 0.000 claims description 13
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 9
- 239000002253 acid Substances 0.000 claims description 8
- 238000010992 reflux Methods 0.000 claims description 8
- -1 ester compound Chemical class 0.000 claims description 7
- 238000006555 catalytic reaction Methods 0.000 claims description 6
- 230000035484 reaction time Effects 0.000 claims description 4
- 238000007599 discharging Methods 0.000 claims description 2
- 230000001376 precipitating effect Effects 0.000 claims description 2
- PPOHPUOKXMNCCI-UHFFFAOYSA-N n-(3,4,5,6-tetrahydro-2h-azepin-7-yl)hydroxylamine Chemical compound ONC1=NCCCCC1 PPOHPUOKXMNCCI-UHFFFAOYSA-N 0.000 claims 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 abstract description 18
- 229910052799 carbon Inorganic materials 0.000 abstract description 17
- WQZGKKKJIJFFOK-GASJEMHNSA-N Glucose Natural products OC[C@H]1OC(O)[C@H](O)[C@@H](O)[C@@H]1O WQZGKKKJIJFFOK-GASJEMHNSA-N 0.000 abstract description 7
- 230000000694 effects Effects 0.000 abstract description 7
- 239000008103 glucose Substances 0.000 abstract description 7
- 230000000052 comparative effect Effects 0.000 description 11
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 9
- XKMRRTOUMJRJIA-UHFFFAOYSA-N ammonia nh3 Chemical compound N.N XKMRRTOUMJRJIA-UHFFFAOYSA-N 0.000 description 7
- 239000010842 industrial wastewater Substances 0.000 description 7
- 238000006146 oximation reaction Methods 0.000 description 7
- 241000894006 Bacteria Species 0.000 description 6
- UHOVQNZJYSORNB-UHFFFAOYSA-N Benzene Chemical compound C1=CC=CC=C1 UHOVQNZJYSORNB-UHFFFAOYSA-N 0.000 description 6
- 239000002028 Biomass Substances 0.000 description 5
- 150000001298 alcohols Chemical class 0.000 description 5
- 239000003054 catalyst Substances 0.000 description 5
- 230000014759 maintenance of location Effects 0.000 description 5
- 230000001546 nitrifying effect Effects 0.000 description 5
- 229910001108 Charcoal iron Inorganic materials 0.000 description 4
- VEZUQRBDRNJBJY-UHFFFAOYSA-N cyclohexanone oxime Chemical compound ON=C1CCCCC1 VEZUQRBDRNJBJY-UHFFFAOYSA-N 0.000 description 4
- 229910052757 nitrogen Inorganic materials 0.000 description 4
- 238000004065 wastewater treatment Methods 0.000 description 4
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 description 3
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 3
- QALQXPDXOWOWLD-UHFFFAOYSA-N [N][N+]([O-])=O Chemical compound [N][N+]([O-])=O QALQXPDXOWOWLD-UHFFFAOYSA-N 0.000 description 3
- 239000000654 additive Substances 0.000 description 3
- 230000008878 coupling Effects 0.000 description 3
- 238000010168 coupling process Methods 0.000 description 3
- 238000005859 coupling reaction Methods 0.000 description 3
- 239000000945 filler Substances 0.000 description 3
- 150000002576 ketones Chemical class 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 239000002904 solvent Substances 0.000 description 3
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 2
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- HEDRZPFGACZZDS-UHFFFAOYSA-N Chloroform Chemical compound ClC(Cl)Cl HEDRZPFGACZZDS-UHFFFAOYSA-N 0.000 description 2
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 2
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 2
- 150000007513 acids Chemical class 0.000 description 2
- 230000000996 additive effect Effects 0.000 description 2
- 150000001299 aldehydes Chemical class 0.000 description 2
- RPRPDTXKGSIXMD-UHFFFAOYSA-N butyl hexanoate Chemical compound CCCCCC(=O)OCCCC RPRPDTXKGSIXMD-UHFFFAOYSA-N 0.000 description 2
- 239000013064 chemical raw material Substances 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000004821 distillation Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 150000002148 esters Chemical class 0.000 description 2
- 238000000605 extraction Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 230000009935 nitrosation Effects 0.000 description 2
- 238000007034 nitrosation reaction Methods 0.000 description 2
- 125000001477 organic nitrogen group Chemical group 0.000 description 2
- 230000020477 pH reduction Effects 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- HNAGHMKIPMKKBB-UHFFFAOYSA-N 1-benzylpyrrolidine-3-carboxamide Chemical compound C1C(C(=O)N)CCN1CC1=CC=CC=C1 HNAGHMKIPMKKBB-UHFFFAOYSA-N 0.000 description 1
- RCHLXMOXBJRGNX-UHFFFAOYSA-N 1-butylcyclohexan-1-ol Chemical compound CCCCC1(O)CCCCC1 RCHLXMOXBJRGNX-UHFFFAOYSA-N 0.000 description 1
- ZNBNBTIDJSKEAM-UHFFFAOYSA-N 4-[7-hydroxy-2-[5-[5-[6-hydroxy-6-(hydroxymethyl)-3,5-dimethyloxan-2-yl]-3-methyloxolan-2-yl]-5-methyloxolan-2-yl]-2,8-dimethyl-1,10-dioxaspiro[4.5]decan-9-yl]-2-methyl-3-propanoyloxypentanoic acid Chemical compound C1C(O)C(C)C(C(C)C(OC(=O)CC)C(C)C(O)=O)OC11OC(C)(C2OC(C)(CC2)C2C(CC(O2)C2C(CC(C)C(O)(CO)O2)C)C)CC1 ZNBNBTIDJSKEAM-UHFFFAOYSA-N 0.000 description 1
- PCWGTDULNUVNBN-UHFFFAOYSA-N 4-methylpentan-1-ol Chemical compound CC(C)CCCO PCWGTDULNUVNBN-UHFFFAOYSA-N 0.000 description 1
- OKJADYKTJJGKDX-UHFFFAOYSA-N Butyl pentanoate Chemical compound CCCCOC(=O)CCCC OKJADYKTJJGKDX-UHFFFAOYSA-N 0.000 description 1
- 125000003182 D-alloisoleucine group Chemical group [H]N([H])[C@@]([H])(C(=O)[*])[C@](C([H])([H])[H])([H])C(C([H])([H])[H])([H])[H] 0.000 description 1
- XTJFFFGAUHQWII-UHFFFAOYSA-N Dibutyl adipate Chemical compound CCCCOC(=O)CCCCC(=O)OCCCC XTJFFFGAUHQWII-UHFFFAOYSA-N 0.000 description 1
- 102000004190 Enzymes Human genes 0.000 description 1
- 108090000790 Enzymes Proteins 0.000 description 1
- 229920002292 Nylon 6 Polymers 0.000 description 1
- DKGAVHZHDRPRBM-UHFFFAOYSA-N Tert-Butanol Chemical compound CC(C)(C)O DKGAVHZHDRPRBM-UHFFFAOYSA-N 0.000 description 1
- UGACIEPFGXRWCH-UHFFFAOYSA-N [Si].[Ti] Chemical compound [Si].[Ti] UGACIEPFGXRWCH-UHFFFAOYSA-N 0.000 description 1
- WNLRTRBMVRJNCN-UHFFFAOYSA-L adipate(2-) Chemical compound [O-]C(=O)CCCCC([O-])=O WNLRTRBMVRJNCN-UHFFFAOYSA-L 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 238000005842 biochemical reaction Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- OBNCKNCVKJNDBV-UHFFFAOYSA-N butanoic acid ethyl ester Natural products CCCC(=O)OCC OBNCKNCVKJNDBV-UHFFFAOYSA-N 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 239000003610 charcoal Substances 0.000 description 1
- 230000001112 coagulating effect Effects 0.000 description 1
- PDXRQENMIVHKPI-UHFFFAOYSA-N cyclohexane-1,1-diol Chemical compound OC1(O)CCCCC1 PDXRQENMIVHKPI-UHFFFAOYSA-N 0.000 description 1
- HPXRVTGHNJAIIH-UHFFFAOYSA-N cyclohexanol Chemical compound OC1CCCCC1 HPXRVTGHNJAIIH-UHFFFAOYSA-N 0.000 description 1
- PAFZNILMFXTMIY-UHFFFAOYSA-N cyclohexylamine Chemical compound NC1CCCCC1 PAFZNILMFXTMIY-UHFFFAOYSA-N 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 229920006351 engineering plastic Polymers 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 239000000835 fiber Substances 0.000 description 1
- 238000007667 floating Methods 0.000 description 1
- ACCCMOQWYVYDOT-UHFFFAOYSA-N hexane-1,1-diol Chemical compound CCCCCC(O)O ACCCMOQWYVYDOT-UHFFFAOYSA-N 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 238000005984 hydrogenation reaction Methods 0.000 description 1
- 229910000378 hydroxylammonium sulfate Inorganic materials 0.000 description 1
- 239000008235 industrial water Substances 0.000 description 1
- 238000005342 ion exchange Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000002808 molecular sieve Substances 0.000 description 1
- 238000006386 neutralization reaction Methods 0.000 description 1
- 150000002894 organic compounds Chemical class 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000003973 paint Substances 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
- 238000004321 preservation Methods 0.000 description 1
- 230000008707 rearrangement Effects 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 description 1
- 229910000029 sodium carbonate Inorganic materials 0.000 description 1
- 238000000638 solvent extraction Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 238000009280 upflow anaerobic sludge blanket technology Methods 0.000 description 1
Abstract
The invention relates to a denitrification method and a denitrification device for caprolactam wastewater. The method comprises the following steps: 1) Removing sediment from caprolactam wastewater by a primary sedimentation tank; 2) Placing waste alkali liquor for preparing cyclohexanone by an oxidation method into a hydrolysis kettle for hydrolysis reaction, and cooling and heat exchanging through a heat exchanger after hydrolysis is completed; 3) Mixing the hydrolyzed waste alkali solution passing through the heat exchanger in the step 2) with caprolactam wastewater in a mixing valve, and then entering a pool A (anoxic pool) for denitrification reaction in the pool A; 4) The waste liquid treated in the step 3) enters an O pool (oxidation pool) and is subjected to nitration reaction in the O pool; and 5) returning a part of the water discharged from the outlet of the pool O to the inlet of the pool A, and the other part of the water discharged from the outlet of the upper layer to the secondary sedimentation tank, wherein a part of the sludge at the lower part is returned to the pool A, and the rest is discharged. The method reduces the treatment cost of caprolactam wastewater, and the biological denitrification effect is superior to that of adding glucose as a carbon source.
Description
Technical Field
The application belongs to the field of chemical wastewater treatment, and in particular relates to a denitrification method and device for caprolactam wastewater.
Background
A series of denitrification treatment methods for industrial wastewater from different sources are disclosed in the prior art.
For example, patent CN107879473B discloses a method for improving biological denitrification treatment efficiency of industrial wastewater, adding biomass charcoal iron catalyst filler into a biological aerobic tank, introducing industrial wastewater into the aerobic tank in batches, completely refluxing effluent, performing circulating operation, and domesticating to form an aerobic-biomass charcoal iron coupling system; adding biomass charcoal iron catalyst filler into a biological anoxic tank, mixing effluent of a biological aerobic tank with industrial wastewater to serve as inflow water, completely refluxing reaction effluent, performing circular operation, domesticating to form an anoxic-biomass charcoal iron coupling system, and performing multistage combination on the two coupling systems to form a multistage enhanced denitrification system, wherein biomass charcoal serves as a slow-release carbon source in a denitrification process, and the biological denitrification effect of the industrial wastewater is remarkably improved.
Patent CN116495923A discloses a pharmaceutical industry high ammonia nitrogen wastewater treatment system and a treatment process, wherein the process comprises a coagulating sedimentation tank, a distribution tank, a UASB reaction tank, an HBF tank, a secondary sedimentation tank and a clean water tank, wherein the HBF tank is continuously provided with two stages of A/O reaction tanks, an enzyme floating filler is filled in an aerobic tank, a good environment is provided for the growth of bacteria, and the ammonia nitrogen removal rate in wastewater can reach more than 90%.
Patent CN116514281a discloses a treatment process of industrial wastewater, the wastewater is treated by a grating, a part of the grating effluent enters a hydrolysis acidification tank, the other part of the grating effluent enters a high-efficiency anaerobic treatment reactor, the effluent of the reactor sequentially enters an anaerobic tank, an anoxic tank and an aerobic tank for treatment, a part of the effluent of the aerobic tank flows back to the anoxic tank, the other part of the effluent enters a sedimentation tank for mud-water separation, the process uses the hydrolysis acidification wastewater as a carbon source, the consumption of the added carbon source is reduced, and the effluent can reach the discharge standard of white spirit industrial water pollutants (GB 27631-2011).
The literature (Li Binghui. Biochemical treatment research on caprolactam wastewater of petrochemical system [ D ]. China university of technology 2012) proposes a short-cut nitrification/denitrification process for treating caprolactam wastewater, and various factors such as temperature, pH, reflux ratio, C/N ratio and sludge load are researched to influence the degradation of ammonia nitrogen, wherein glucose is used as a carbon source, the biochemical reaction temperature is controlled to be about 30 ℃, the pH value is between 7.5 and 8.5, the dissolved oxygen concentration is about 0.5 mg/L, the ammonia nitrogen concentration of effluent is lower than 8 mg/L, and the removal rate is more than 98%.
Caprolactam is known to be an important organic chemical raw material, is easy to absorb water and deliquesce, is easy to dissolve in solvents such as water, ethanol, diethyl ether, acetone, chloroform, benzene and the like, has a molecular formula of C6H11NO, is mainly used for producing nylon 6 resin, has wide application field, and can be used as fibers, engineering plastics, films and the like.
The hydroxylamine sulfate process (HSO) is a mainstream production process of caprolactam, and comprises the procedures of oximation, rearrangement, neutralization, benzene extraction, back extraction, ion exchange, hydrogenation, distillation and the like. The oximation reaction is an important procedure for producing caprolactam, the reaction takes tertiary butanol as a solvent, the reaction temperature is 85 ℃ and the pressure is 0.4 MPa, cyclohexanone, ammonia and hydrogen peroxide are subjected to oximation reaction in an oximation reactor under the catalysis of a titanium-silicon molecular sieve, and then the finished product cyclohexanone oxime is obtained through catalyst separation, solvent extraction and cyclohexanone oxime distillation. Industrial wastewater containing high concentration of organic nitrogen and ammonia nitrogen is generated in the oximation reaction, and denitrification treatment is needed to ensure that the wastewater reaches the standard for discharge.
The pre-denitrification biological denitrification process, also called as anoxic/aerobic (A/O) denitrification process, is the most economical and reasonable biological denitrification technology at present, has the advantages of good denitrification effect, less investment and low operation cost, and has the minimum influence on the environment. As shown in fig. 1, an anoxic/oxic (a/O) denitrification process consists of an a tank 2 (anoxic tank) and an O tank 3 (oxic tank), wherein heterotrophic denitrifying bacteria convert nitro nitrogen in wastewater from a primary sedimentation tank 1 into nitrogen gas to be discharged, so as to realize denitrification; in the O tank 3, nitrifying bacteria oxidize organic nitrogen and ammonia nitrogen into nitronitrogen through two processes of nitrosation and nitrifying, the generated nitronitrogen returns to the A tank 2 for continuous circulation through mixed liquor reflux, biological denitrification is realized, wastewater after A/O treatment enters the secondary sedimentation tank 4 for sedimentation, upper layer effluent after sedimentation is discharged, part of residual sludge is discharged, and the other part of residual sludge can return to the A tank 2. In the denitrification process of the pool A, an electron donor (such as an alcohol compound) is required to be added to realize denitrification reaction, and a carbon source (such as an organic compound) is also required to be added to meet the growth of heterotrophic denitrifying bacteria. In the O pool, hydrogen ions are generated in the nitration process, so that the alkalinity of the wastewater is reduced, and alkali liquor needs to be supplemented to maintain a certain alkalinity.
In the existing caprolactam wastewater biological denitrification process, in order to maintain higher denitrification efficiency, an electron donor such as alcohols and an organic carbon source are required to be added in the denitrification process, and alkali liquor is required to be supplemented in the nitrification process, so that the treatment cost of caprolactam wastewater is increased.
Cyclohexanone is an important chemical raw material, is an intermediate for producing caprolactam and adipate, and is also an important solvent for producing various paints. A large amount of waste alkali liquid is generated in the cyclohexanone production process by an oxidation method, wherein the waste alkali liquid contains 30-40% of organic matters such as alcohol, aldehyde, acid, ketone and ester, 8% of sodium hydroxide and 7% of sodium carbonate, the total alkalinity exceeds 3700 mmol/L, the relative content of the alcohol, aldehyde, acid, ketone and ester in 30-40% of organic matters is different depending on different cyclohexanone synthesis process conditions, and the content of various compounds in typical cyclohexanone waste alkali liquid by the oxidation method is shown in table 1.
TABLE 1 mass concentration percentage of various compounds in typical oxidation cyclohexanone waste lye
Therefore, considering the specific material constitution of the cyclohexanone waste lye by oxidation, it is necessary to investigate the feasibility of waste lye for producing cyclohexanone by oxidation in the anoxic/aerobic (a/O) denitrification process of cyclohexylamide wastewater.
Disclosure of Invention
Aiming at the problem that the existing caprolactam wastewater anoxic/aerobic (A/O) denitrification process needs to be externally added with additives such as electron donors, carbon sources, alkali liquor and the like, the wastewater treatment cost is increased. According to the invention, alcohols such as cyclohexanediol, hexanediol, cyclohexanol and 4-methylpentanol in the oxidized cyclohexanone waste alkali liquor are used as electron donors for denitrification reaction, acids and ketones with different carbon chain lengths are used as carbon sources, meanwhile, sodium hydroxide contained in the oxidized cyclohexanone waste alkali liquor is used as a catalyst through a high-temperature hydrolysis process, ester compounds such as ethyl butyrate, butyl valerate, butyl caproate, butyl adipate and butyl cyclohexanol contained in the oxidized cyclohexanone waste alkali liquor are hydrolyzed to generate alcohols and acids, the alcohols provide the required electron donors for heterotrophic denitrifying bacteria growth, and the denitrification efficiency of the denitrification process is further improved. In the nitrifying process, the alkalinity in the cyclohexanone waste alkali liquid by an oxidation method is utilized, and the nitrosation of nitrifying bacteria and the normal operation of the nitrifying process can be ensured without additional alkali liquid.
In one aspect, the present invention provides a caprolactam wastewater denitrification process comprising the steps of:
(1) Removing sediment from caprolactam wastewater by a primary sedimentation tank;
(2) Placing waste alkali liquor for preparing cyclohexanone by an oxidation method into a hydrolysis kettle, carrying out hydrolysis reaction under the catalysis of sodium hydroxide contained in the waste alkali liquor for cyclohexanone by the oxidation method, wherein the temperature is 50-90 ℃, the stirring speed is 10-100 r/min, the reaction time is 0.5-3 h, cooling and heat exchanging are carried out through a heat exchanger after the hydrolysis is completed, the temperature of the waste alkali liquor for hydrolysis after heat exchanging through the heat exchanger is 10-40 ℃, and the flow is 10-40L/h;
(3) Mixing the hydrolyzed waste alkali solution passing through the heat exchanger in the step (2) with caprolactam wastewater from the step (1) in a mixing valve, then entering a pool A (anoxic pool), and carrying out denitrification reaction in the pool A at the temperature of 20-40 ℃ for 10-70 h and the rotating speed of a stirring paddle of 5-60 r/min;
(4) The waste liquid treated in the step (3) enters an O pool (oxidation pool), nitration reaction is carried out in the O pool, the temperature is 20-40 ℃, and the retention time is 20-100 h; and
(5) And (3) returning part of the discharged water from the outlet of the O pool to the inlet of the A pool, wherein the flow is 30-80L/min, the other part of discharged water enters the secondary sedimentation tank, standing is carried out for 10-30 h, the upper layer discharged water in the secondary sedimentation tank is discharged, part of the lower sludge is returned to the A pool, the other part of sludge is discharged, and the sludge reflux amount is 10-60% of the total sludge amount.
In a specific embodiment, in the step (1), the caprolactam wastewater is from a caprolactam oximation process, and the flow rate of the caprolactam wastewater entering the primary sedimentation tank is 50-150 m 3 /h。
In the specific implementation mode, in the step (2), the hydrolysis temperature is 60-80 ℃, the stirring speed is 30-70 rpm, and the reaction time is 0.5-3 h; the temperature of the hydrolyzed waste alkali solution subjected to heat exchange by the heat exchanger is 20-30 ℃, and the heat exchanger is a tube type heat exchanger.
In a specific embodiment, in the step (2), in the hydrolysis kettle, the ester compound contained in the waste alkali liquid for preparing cyclohexanone by an oxidation method is hydrolyzed to generate alcohol and acid.
In a specific embodiment, in the step (2), the concentration of sodium hydroxide in the waste lye for preparing cyclohexanone by an oxidation method is 5-10%, for example 8%.
In the specific embodiment, in the step (3), the denitrification reaction temperature in the tank A is 30 ℃, the residence time is 40h, and the rotating speed of the stirring paddle is 20-40 r/min.
In a specific embodiment, in step (4), the nitration reaction temperature in the O cell is 30 ℃ and the residence time is 60 h. In the specific embodiment, in the step (5), part of the water discharged from the outlet of the O pool is returned to the inlet of the A pool, the flow is 40-60L/min, the other part of the water discharged from the outlet of the O pool enters the secondary sedimentation tank, the water is kept stand for 20-h, the upper layer of the water discharged from the secondary sedimentation tank is discharged, part of the lower sludge is returned to the A pool, the rest of the sludge is discharged, and the sludge return amount is 30-40% of the total sludge amount.
In another aspect, the present invention provides a caprolactam wastewater denitrification device comprising the following components (1) - (6) and a pipeline connecting these components in the following manner:
(1) A primary sedimentation tank for removing sediment in caprolactam wastewater;
(2) A hydrolysis kettle provided with a stirring paddle, wherein waste lye for preparing cyclohexanone by an oxidation method is contained, and ester compounds contained in the waste lye are hydrolyzed to generate alcohol and acid under the catalysis of sodium hydroxide contained in the waste lye;
(3) The heat exchanger is connected with the hydrolysis kettle through a pipeline, and exchanges heat and cools the hydrolyzed waste alkali liquor in the hydrolysis kettle;
(4) A mixing valve connected to the primary sedimentation tank and the heat exchanger through a pipeline, for mixing the wastewater from the primary sedimentation tank with the wastewater from the heat exchanger, and supplying the mixed wastewater to the tank a through the pipeline;
(5) The pool A is connected with the mixing valve through a pipeline and receives wastewater from the mixing valve, and the wastewater from the mixing valve is subjected to denitrification reaction in the pool A and then is subjected to nitration reaction in the pool O;
(6) And the secondary sedimentation tank is connected with the O tank through a pipeline and is used for precipitating the wastewater subjected to the nitration reaction, and respectively discharging upper-layer effluent and lower sludge through the pipeline.
In a specific embodiment, the hydrolysis tank has a heat-insulating jacket.
In a specific embodiment, the apparatus further comprises a line for returning the effluent from the outlet of the O-basin to the inlet of the a-basin and a line for returning a portion of the sludge in the secondary sedimentation basin to the a-basin.
Advantageous effects
According to the invention, an anoxic/aerobic (A/O) denitrification process is adopted to biologically remove ammonia nitrogen in caprolactam wastewater, an alcohol electron donor and a carbon source are provided in a denitrification process in a biological denitrification process by using a high-temperature hydrolyzed cyclohexanone waste alkali solution, and an alkaline environment is provided in a nitrification process by using the alkalinity in the waste alkali solution, so that the denitrification efficiency in the denitrification process is further improved, alcohols such as methanol and the like are not required to be added as the electron donor, glucose is not required to be added as the carbon source, alkali solution is not required to be added, the treatment cost of caprolactam wastewater is reduced, and the experimental result of the application also shows that the biological denitrification effect of caprolactam wastewater is superior to that of glucose as the carbon source.
Drawings
FIG. 1 shows a schematic diagram of an anoxic/aerobic (A/O) denitrification process in the prior art.
FIG. 2 shows a schematic diagram of an A/O denitrification device for caprolactam wastewater of the present invention.
As shown in fig. 2, caprolactam wastewater enters a primary sedimentation tank, and sediment is removed through the primary sedimentation tank 1; the cyclohexanone waste alkali liquor in the oxidation method is hydrolyzed in a hydrolysis kettle 5 with a heat preservation jacket, after hydrolysis is completed, the cyclohexanone waste alkali liquor is subjected to cooling heat exchange through a heat exchanger 6, then is mixed with caprolactam waste water in a mixing valve 7, enters a tank A2, is subjected to denitrification reaction in the tank A2, then enters a tank O3, is subjected to nitrification reaction in the tank O3, a part of discharged water at the outlet of the tank O3 is returned to the inlet of the tank A2, the other part of discharged water enters a secondary sedimentation tank 4, and is left, the discharged water at the upper layer in the secondary sedimentation tank 4 is discharged, a part of sludge at the lower part is returned to the tank A2, and the rest of sludge is discharged.
Reference numerals
1: primary sedimentation tank
2: a pool (anoxic pool)
3: o pool (aerobic pool)
4: secondary sedimentation tank
5: hydrolysis kettle
6: heat exchanger
7: mixing valve
Detailed Description
Comparative example 1: glucose is used as a carbon source, sodium hydroxide is used as an alkali liquor, and the oxidation method cyclohexanone waste alkali liquor is not utilized to carry out A/O denitrification on caprolactam wastewater.
Oximation of waste water with caprolactam by 100 m 3 The flow rate of/h enters a primary sedimentation tank, sediment is removed through the primary sedimentation tank, the adding amount of glucose is 12.5 kg/h, the mixture is mixed with caprolactam wastewater in a mixing valve, the mixture enters a tank A, denitrification reaction is carried out in the tank A, the temperature is 30 ℃, the retention time is 40h, and the rotating speed of a stirring paddle is 30 revolutions per minute; then the wastewater enters an O pool, nitration reaction is carried out in the O pool, the temperature is 30 ℃, the retention time is 60 and h, the alkali liquor addition amount is 1.0L/h, a part of wastewater at the outlet of the O pool is returned to the inlet of the A pool, the flow is 50L/min, the other part of wastewater enters a secondary sedimentation pool, the standing is 20 and h, the upper layer effluent is discharged, a part of sludge at the lower part is returned to the A pool, the rest part is discharged, and the sludge reflux amount is 35% of the total sludge amount.
Comparative example 2: the oxidation method cyclohexanone waste alkali liquor is used as an additive, and the A/O denitrification of caprolactam wastewater is carried out without high-temperature hydrolysis treatment.
Caprolactam waste water at 100 m 3 The flow of/h enters a primary sedimentation tank, sediment is removed through the primary sedimentation tank, the flow of cyclohexanone waste alkali liquid by an oxidation method is 15L/h, the cyclohexanone waste alkali liquid and caprolactam waste water are mixed in a mixing valve, then enter a tank A, denitrification reaction is carried out in the tank A, the temperature is 30 ℃, the retention time is 40h, and the rotating speed of a stirring paddle is 30 revolutions per minute; then the wastewater enters an O pool, nitration reaction is carried out in the O pool, the temperature is 30 ℃, the retention time is 60 h, a part of wastewater at the outlet of the O pool is returned to the inlet of the A pool, the flow is 50L/min, the other part of wastewater enters a secondary sedimentation tank, the wastewater stands for 20 h, the upper layer of wastewater is discharged, a part of sludge at the lower part is returned to the A pool, the rest part is discharged, and the sludge reflux quantity is 35% of the total sludge quantity.
Example 1: the oxidation method cyclohexanone waste alkali liquor is used as an additive and is subjected to high-temperature hydrolysis treatment.
Caprolactam waste water at 100 m 3 And (3) the flow of/h enters a primary sedimentation tank, and sediment is removed through the primary sedimentation tank. The method comprises the steps that cyclohexanone waste alkali liquor (with the composition shown in the table 1) is subjected to cooling heat exchange through a tube type heat exchanger after hydrolysis in a hydrolysis kettle under the catalysis of sodium hydroxide (the concentration of sodium hydroxide in the waste alkali liquor is 8%), the temperature is 70 ℃, the stirring rotation speed is 40 r/min, the reaction time is 1.5 and h, the temperature of the hydrolyzed waste alkali liquor after the hydrolysis is discharged out of the heat exchanger is 25 ℃, the flow is 15L/h, and then the hydrolyzed waste alkali liquor and caprolactam wastewater are mixed in a mixing valve and enter a pool A for denitrification reaction in the pool A, the temperature is 30 ℃, the residence time is 40h and the stirring paddle rotation speed is 30 r/min; then the wastewater enters an O pool, nitration reaction is carried out in the O pool, the temperature is 30 ℃, the residence time is 60 h, a part of wastewater at the outlet of the O pool is returned to the inlet of the A pool, the flow is 50L/min, the other part of wastewater enters a secondary sedimentation tank, the wastewater stands for 20 h, the upper layer of wastewater is discharged, a part of sludge at the lower part is returned to the A pool, the other part of sludge is discharged, and the returned sludge flow is 35% of the total sludge (the specific flow can be seen in figure 2).
Example 2: the procedure is as in example 1, except that the hydrolysis temperature of the oxidized cyclohexanone waste lye in the hydrolysis tank is 60 ℃.
Example 3: the procedure is as in example 1, except that the hydrolysis temperature of the oxidized cyclohexanone waste lye in the hydrolysis tank is 80 ℃.
Example 4: the procedure is as in example 1, except that the hydrolysis time of the oxidized cyclohexanone waste lye in the hydrolysis tank is 0.5. 0.5 h.
Example 5: the procedure is as in example 1, except that the hydrolysis time of the oxidized cyclohexanone waste lye in the hydrolysis tank is 3 h.
Test example: the total nitrogen and pH values of the secondary sedimentation tank effluent of comparative examples 1 to 2 and example 1 were analyzed once a day, and continuously detected for 15 days, wherein the total nitrogen was analyzed by HJ 636-2012 standard, the pH values were analyzed by online pH analysis, and the total nitrogen and pH results are shown in tables 2 and 3, respectively, below.
TABLE 2 Total Nitrogen in effluent over 15 days for comparative examples 1-2 and examples 1-5
TABLE 3 pH of effluent over 15 days for comparative examples 1-2 and examples 1-5
As can be seen from the results of tables 2 and 3, in comparative example 2, the present invention uses oxidized cyclohexanone waste lye as electron donor, carbon source and lye in biological denitrification process of caprolactam waste water, the denitrification effect of treated caprolactam waste water is similar to that of comparative example 1 using glucose as carbon source, while in example 1, the denitrification effect is better than that of comparative examples 1 and 2 by high temperature hydrolysis treatment of oxidized cyclohexanone waste lye. Moreover, the oxidation method does not need additional alkali liquor after cyclohexanone waste alkali liquor treatment, the pH value of the caprolactam waste water after treatment is higher than that of comparative example 1 to which alkali liquor is added, and the pH value of the caprolactam waste water after treatment of example 1 is slightly lower than that of comparative example 2 and still higher than that of comparative example 1 due to the consumption of part of sodium hydroxide catalyst in the hydrolysis process.
The results show that the invention takes the cyclohexanone waste alkali liquor by the high-temperature hydrolysis oxidation method as the electron donor, the carbon source and the alkali liquor in the biological denitrification process of the caprolactam waste water, can well realize the denitrification of the caprolactam waste liquid, does not need to add the carbon source and the alkali liquor, and reduces the wastewater treatment cost.
Claims (7)
1. A method for denitrification of caprolactam wastewater, the method comprising the steps of:
(1) Removing sediment from caprolactam wastewater by a primary sedimentation tank;
(2) Placing waste alkali liquor for preparing cyclohexanone by an oxidation method into a hydrolysis kettle, carrying out hydrolysis reaction under the catalysis of sodium hydroxide contained in the waste alkali liquor for cyclohexanone by the oxidation method, wherein the temperature is 60-80 ℃, the stirring rotation speed is 30-70 r/min, the reaction time is 0.5-3 h, cooling and heat exchanging are carried out through a heat exchanger after the hydrolysis is completed, the temperature of the waste alkali liquor for hydrolysis after heat exchanging through the heat exchanger is 20-30 ℃, the flow is 10-40L/h, the heat exchanger is a tubular heat exchanger,
in the hydrolysis kettle, the ester compound contained in the waste alkali liquor for preparing cyclohexanone by an oxidation method is hydrolyzed to generate alcohol and acid, and the mass concentration of sodium hydroxide in the waste alkali liquor for preparing cyclohexanone by the oxidation method is 5-10%;
(3) Mixing the hydrolyzed waste alkali solution passing through the heat exchanger in the step (2) with caprolactam wastewater from the step (1) in a mixing valve, then entering a pool A, performing denitrification reaction in the pool A at 20-40 ℃ for 10-70 h, and rotating a stirring paddle at a rotating speed of 5-60 r/min;
(4) The waste liquid treated in the step (3) enters an O pool, and is subjected to nitration reaction in the O pool at the temperature of 20-40 ℃ for 20-100 hours; and
(5) And (3) returning part of the discharged water from the outlet of the O pool to the inlet of the A pool, wherein the flow is 30-80L/min, the other part of discharged water enters the secondary sedimentation tank, standing is carried out for 10-30 h, the upper layer discharged water in the secondary sedimentation tank is discharged, part of the lower sludge is returned to the A pool, the other part of sludge is discharged, and the sludge reflux amount is 10-60% of the total sludge amount.
2. The method of claim 1, wherein in the step (1), the caprolactam wastewater is from a caprolactam oxime process, and the flow rate of the caprolactam wastewater into the primary sedimentation tank is 50-150 m 3 /h。
3. The method according to claim 1, wherein in the step (3), denitrification reaction is carried out in the tank A at a temperature of 30 ℃, a residence time of 40 hours and a stirring paddle rotation speed of 20-40 revolutions per minute.
4. The process of claim 1, wherein in step (4), the nitration reaction temperature in the O cell is 30 ℃ and the residence time is 60 h.
5. The method according to claim 1, wherein in the step (5), a part of the effluent from the outlet of the pool O is returned to the inlet of the pool A at a flow rate of 40-60L/min, the other part of the effluent enters the secondary sedimentation tank, the secondary sedimentation tank is left to stand for 20-h, the upper effluent in the secondary sedimentation tank is discharged, a part of the lower sludge is returned to the pool A, the rest of the sludge is discharged, and the sludge return amount is 30-40% of the total sludge amount.
6. The device comprises the following components (1) - (6) and pipelines for connecting the components in the following manner:
(1) A primary sedimentation tank for removing sediment in caprolactam wastewater;
(2) A hydrolysis kettle provided with a stirring paddle, wherein waste lye for preparing cyclohexanone by an oxidation method is contained, and ester compounds contained in the waste lye are hydrolyzed to generate alcohol and acid under the catalysis of sodium hydroxide contained in the waste lye;
(3) The heat exchanger is connected with the hydrolysis kettle through a pipeline, and exchanges heat and cools the hydrolyzed waste alkali liquor in the hydrolysis kettle;
(4) A mixing valve connected to the primary sedimentation tank and the heat exchanger through a pipeline, for mixing the wastewater from the primary sedimentation tank with the wastewater from the heat exchanger, and supplying the mixed wastewater to the tank a through the pipeline;
(5) The pool A is connected with the mixing valve through a pipeline and receives wastewater from the mixing valve, and the wastewater from the mixing valve is subjected to denitrification reaction in the pool A and then is subjected to nitration reaction in the pool O;
(6) And the secondary sedimentation tank is connected with the O tank through a pipeline and is used for precipitating the wastewater subjected to the nitration reaction, and respectively discharging upper-layer effluent and lower sludge through the pipeline.
7. The apparatus of claim 6, wherein the hydrolysis tank has a thermal jacket and the apparatus further comprises a line for returning the O-tank outlet drain to the a-tank inlet and a line for returning a portion of the sludge in the secondary sedimentation tank to the a-tank.
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