CN117384068A - Dicyandiamide waste residue extraction method - Google Patents
Dicyandiamide waste residue extraction method Download PDFInfo
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- CN117384068A CN117384068A CN202311173734.5A CN202311173734A CN117384068A CN 117384068 A CN117384068 A CN 117384068A CN 202311173734 A CN202311173734 A CN 202311173734A CN 117384068 A CN117384068 A CN 117384068A
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- dicyandiamide
- waste residue
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- QGBSISYHAICWAH-UHFFFAOYSA-N dicyandiamide Chemical compound NC(N)=NC#N QGBSISYHAICWAH-UHFFFAOYSA-N 0.000 title claims abstract description 126
- 239000002699 waste material Substances 0.000 title claims abstract description 73
- 238000000605 extraction Methods 0.000 title claims abstract description 12
- 238000005406 washing Methods 0.000 claims abstract description 90
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 claims abstract description 62
- 239000000706 filtrate Substances 0.000 claims abstract description 53
- 239000000047 product Substances 0.000 claims abstract description 47
- 239000012065 filter cake Substances 0.000 claims abstract description 43
- 239000002002 slurry Substances 0.000 claims abstract description 35
- 229910000019 calcium carbonate Inorganic materials 0.000 claims abstract description 31
- XZMCDFZZKTWFGF-UHFFFAOYSA-N Cyanamide Chemical compound NC#N XZMCDFZZKTWFGF-UHFFFAOYSA-N 0.000 claims abstract description 20
- 229920001661 Chitosan Polymers 0.000 claims abstract description 18
- 238000001704 evaporation Methods 0.000 claims abstract description 16
- 238000007885 magnetic separation Methods 0.000 claims abstract description 16
- ATRRKUHOCOJYRX-UHFFFAOYSA-N Ammonium bicarbonate Chemical compound [NH4+].OC([O-])=O ATRRKUHOCOJYRX-UHFFFAOYSA-N 0.000 claims abstract description 15
- 239000001099 ammonium carbonate Substances 0.000 claims abstract description 15
- 235000012501 ammonium carbonate Nutrition 0.000 claims abstract description 15
- 230000008020 evaporation Effects 0.000 claims abstract description 15
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims abstract description 12
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims abstract description 12
- 238000006116 polymerization reaction Methods 0.000 claims abstract description 12
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims abstract description 9
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 9
- 235000011114 ammonium hydroxide Nutrition 0.000 claims abstract description 9
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 9
- 238000001914 filtration Methods 0.000 claims abstract description 9
- 239000001569 carbon dioxide Substances 0.000 claims abstract description 6
- 229910002092 carbon dioxide Inorganic materials 0.000 claims abstract description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 26
- 238000000034 method Methods 0.000 claims description 24
- 239000000243 solution Substances 0.000 claims description 13
- 238000003756 stirring Methods 0.000 claims description 12
- 238000004537 pulping Methods 0.000 claims description 11
- 239000007864 aqueous solution Substances 0.000 claims description 5
- 239000007787 solid Substances 0.000 claims description 4
- 238000011027 product recovery Methods 0.000 claims description 3
- 238000004064 recycling Methods 0.000 abstract description 2
- 230000000052 comparative effect Effects 0.000 description 16
- 238000011084 recovery Methods 0.000 description 14
- TWRXJAOTZQYOKJ-UHFFFAOYSA-L Magnesium chloride Chemical compound [Mg+2].[Cl-].[Cl-] TWRXJAOTZQYOKJ-UHFFFAOYSA-L 0.000 description 10
- 238000005086 pumping Methods 0.000 description 7
- 238000010586 diagram Methods 0.000 description 6
- 239000007788 liquid Substances 0.000 description 6
- ZLNQQNXFFQJAID-UHFFFAOYSA-L magnesium carbonate Chemical compound [Mg+2].[O-]C([O-])=O ZLNQQNXFFQJAID-UHFFFAOYSA-L 0.000 description 6
- 239000001095 magnesium carbonate Substances 0.000 description 6
- 229910000021 magnesium carbonate Inorganic materials 0.000 description 6
- 229910001629 magnesium chloride Inorganic materials 0.000 description 5
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 4
- 238000005273 aeration Methods 0.000 description 4
- 238000012512 characterization method Methods 0.000 description 4
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N iron oxide Inorganic materials [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 4
- UXVMQQNJUSDDNG-UHFFFAOYSA-L Calcium chloride Chemical compound [Cl-].[Cl-].[Ca+2] UXVMQQNJUSDDNG-UHFFFAOYSA-L 0.000 description 3
- 239000001110 calcium chloride Substances 0.000 description 3
- 229910001628 calcium chloride Inorganic materials 0.000 description 3
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 description 3
- 239000000920 calcium hydroxide Substances 0.000 description 3
- 229910001861 calcium hydroxide Inorganic materials 0.000 description 3
- 239000003795 chemical substances by application Substances 0.000 description 3
- 230000001276 controlling effect Effects 0.000 description 3
- 239000013078 crystal Substances 0.000 description 3
- 238000003825 pressing Methods 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000002425 crystallisation Methods 0.000 description 2
- 230000008025 crystallization Effects 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- NDLPOXTZKUMGOV-UHFFFAOYSA-N oxo(oxoferriooxy)iron hydrate Chemical compound O.O=[Fe]O[Fe]=O NDLPOXTZKUMGOV-UHFFFAOYSA-N 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 238000010992 reflux Methods 0.000 description 2
- 239000000377 silicon dioxide Substances 0.000 description 2
- 235000012239 silicon dioxide Nutrition 0.000 description 2
- 239000002893 slag Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- BHPQYMZQTOCNFJ-UHFFFAOYSA-N Calcium cation Chemical compound [Ca+2] BHPQYMZQTOCNFJ-UHFFFAOYSA-N 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 239000004568 cement Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000018044 dehydration Effects 0.000 description 1
- 238000006297 dehydration reaction Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000003673 groundwater Substances 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 239000002440 industrial waste Substances 0.000 description 1
- 239000006148 magnetic separator Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 230000000379 polymerizing effect Effects 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F11/00—Compounds of calcium, strontium, or barium
- C01F11/18—Carbonates
- C01F11/181—Preparation of calcium carbonate by carbonation of aqueous solutions and characterised by control of the carbonation conditions
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/05—Preparation or purification of carbon not covered by groups C01B32/15, C01B32/20, C01B32/25, C01B32/30
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C277/00—Preparation of guanidine or its derivatives, i.e. compounds containing the group, the singly-bound nitrogen atoms not being part of nitro or nitroso groups
- C07C277/08—Preparation of guanidine or its derivatives, i.e. compounds containing the group, the singly-bound nitrogen atoms not being part of nitro or nitroso groups of substituted guanidines
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/30—Particle morphology extending in three dimensions
- C01P2004/32—Spheres
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Life Sciences & Earth Sciences (AREA)
- Geology (AREA)
- Processing Of Solid Wastes (AREA)
Abstract
The invention provides an extraction method of dicyandiamide waste residue, which belongs to the field of dicyandiamide waste residue treatment, wherein the extraction method comprises the steps of preparing dicyandiamide waste residue into slurry, carrying out magnetic separation and enrichment, collecting effluent, then introducing carbon dioxide for treatment, and carrying out multistage washing on the obtained dicyandiamide waste residue slurry to obtain primary washing filtrate and multistage filter cakes; adjusting the pH value of the primary washing filtrate to 8.8-9.2 by ammonia water, performing low-pressure evaporation concentration and cyanamide polymerization at 70-75 ℃, crystallizing and filtering the obtained high-concentration dicyandiamide solution to obtain a dicyandiamide product; dissolving the multistage filter cake by hydrochloric acid, and filtering to obtain filtrate and a carbon product; adding chitosan into the filtrate, and adding ammonium carbonate to obtain spherical calcium carbonate product. By utilizing the extraction method of dicyandiamide waste residue, dicyandiamide, carbon and calcium carbonate in the dicyandiamide waste residue can be effectively extracted, and corresponding products can be prepared for recycling.
Description
Technical Field
The invention relates to the field of dicyandiamide waste residue treatment, in particular to a method for extracting dicyandiamide waste residue.
Background
In the past, dicyandiamide waste residue is used as industrial waste residue, if the dicyandiamide is exposed in a storage yard, the dicyandiamide is attached to the surface of the waste residue due to the characteristic of dissolving in water, and rainwater can wash the residual dicyandiamide into groundwater and rivers, so that water quality pollution is caused. In the process of producing dicyandiamide products, the problem of high dicyandiamide content in dicyandiamide waste residues is solved first. In the industrial production process, the higher the dicyandiamide content in the waste residue, the greater the treatment difficulty of the waste; when the dicyandiamide content in the waste residue is extremely low, the waste residue can be used as a raw material for producing special cement, and waste is recycled, however, the waste residue at the present stage contains so high dicyandiamide content that the waste residue cannot be recycled.
The dicyandiamide waste residue mainly contains a large amount of calcium carbonate and a small amount of substances such as ferric oxide, magnesium carbonate, carbon, calcium hydroxide, silicon dioxide and the like besides dicyandiamide, and if the components can be comprehensively utilized, the dicyandiamide waste residue is beneficial to the treatment and the environmental protection of the dicyandiamide waste residue, and each component in the dicyandiamide waste residue can be recycled, so that the enterprise benefit is improved.
Disclosure of Invention
The invention provides a method for extracting dicyandiamide waste residues.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
the extraction method of dicyandiamide waste residue comprises the following steps:
s1, pulping
Preparing dicyandiamide waste residue into slurry, carrying out magnetic separation and enrichment, collecting effluent, and then introducing carbon dioxide for treatment to prepare dicyandiamide waste residue slurry;
s2, multistage washing
The dicyandiamide waste residue slurry is subjected to multistage washing to obtain primary washing filtrate and multistage filter cakes;
s3, product recovery
Regulating the pH value of the primary washing filtrate to 8.8-9.2 by ammonia water, performing low-pressure evaporation concentration and cyanamide polymerization at 70-75 ℃, crystallizing and filtering the obtained high-concentration dicyandiamide solution to obtain a dicyandiamide product;
dissolving the multistage filter cake by hydrochloric acid, and filtering to obtain filtrate and a carbon product;
adding chitosan into the filtrate, and adding ammonium carbonate to obtain spherical calcium carbonate product.
In the step S1, the magnetic separation strength of the magnetic separation enrichment is 180 mT to 200mT.
Further, in step S2, the multistage washing includes the steps of:
taking dicyandiamide waste residue slurry, washing by a primary cyclone and dehydrating by a primary vacuum belt dehydrator to obtain a primary filter cake and primary washing filtrate;
pulping the first-stage filter cake by using the third-stage washing filtrate, washing by using a second-stage cyclone, and dehydrating by using a second-stage vacuum belt dehydrator to obtain a second-stage filter cake and a second-stage washing filtrate; the second-stage washing filtrate is used as washing water to pulp the dicyandiamide waste residue in the step S1;
washing the second-stage filter cake by a third-stage cyclone and dehydrating by a third-stage vacuum belt dehydrator to obtain a third-stage filter cake and a third-stage washing filtrate; the third-stage washing filtrate is used as washing water to pulp the first-stage filter cake; and the three-stage filter cake is the multi-stage filter cake.
Further, in the step S3, in the low-pressure evaporation concentration and the cyanamide polymerization process, the evaporated steam is condensed, and the obtained evaporated condensed water is used as washing water to pulp the secondary filter cake.
Further, in step S3, the concentration of the dicyandiamide solution is 12 to 14wt%.
Further, in the step S3, after adding chitosan and before adding ammonium carbonate, the concentration of chitosan in the obtained solution is 6-8 g/L.
Further, in the step S3, the temperature of the obtained system is 50-55 ℃ in the process of adding ammonium carbonate.
Further, in the step S3, in the process of adding ammonium carbonate, the obtained system is stirred at a stirring speed of 400-450 r/min.
Further, in step S3, an aqueous solution of ammonium carbonate having a concentration of 18 to 22wt% is used.
Further, in the step S1, the solid content of slurry prepared from dicyandiamide waste residues is 20-25 wt%.
The extraction method of dicyandiamide waste residue has the beneficial effects that:
according to the method, through a reasonable process route, after iron oxide and part of magnesium carbonate in dicyandiamide waste residue are removed through magnetic separation, carbon dioxide is introduced to convert calcium hydroxide in the dicyandiamide waste residue into calcium carbonate, and then the primary washing filtrate and the tertiary filter cake containing high concentration dicyandiamide and mono-cyanamide are obtained through multistage washing; the primary washing filtrate is subjected to low-pressure evaporation concentration and cyanamide polymerization after the specific pH value is controlled by ammonia water, so that dicyandiamide products are obtained, and the purity and recovery rate of the dicyandiamide products can be effectively improved by controlling the system at the specific pH value and the low-pressure evaporation concentration temperature by the ammonia water;
meanwhile, after the three-stage filter cake is dissolved by hydrochloric acid, filtering to obtain a carbon product, adding a specific amount of chitosan into the filtrate, and controlling the calcium chloride to be converted into a spherical calcium carbonate product under the action of ammonium carbonate by using the chitosan and magnesium chloride contained in the filtrate together as a crystal form control agent;
by utilizing the extraction method of dicyandiamide waste residue, dicyandiamide, carbon and calcium carbonate in the dicyandiamide waste residue can be effectively extracted, and corresponding products can be prepared for recycling;
according to the invention, ammonia water is adopted to control a specific pH value of the primary washing filtrate, so that the polymerization of the dicyandiamide is facilitated, and the decomposition of the dicyandiamide in the heating concentration process can be inhibited to generate ammonia, thereby further improving the recovery rate of the dicyandiamide;
the invention adopts a countercurrent washing mode to wash and dehydrate the dicyandiamide waste residue, can effectively recycle the dicyandiamide and the mono-cyanamide in the dicyandiamide waste residue, and simultaneously reduces the concentration of the residual dicyandiamide and the concentration of the mono-cyanamide in the dicyandiamide waste residue;
according to the invention, by utilizing a negative pressure evaporation mode, moisture in a system can be evaporated by controlling a specific temperature, and simultaneously, the polymerization of the cyanamide is promoted, so that the recovery rate of the dicyandiamide is further improved.
Drawings
FIG. 1 is a process flow diagram of example 1 of the present invention;
FIG. 2 is a structural representation of the calcium carbonate product prepared in example 1 of the present invention;
FIG. 3 is a structural representation of the calcium carbonate product prepared in comparative example 1 of the present invention;
FIG. 4 is a structural representation of the calcium carbonate product prepared in comparative example 2 of the present invention;
FIG. 5 is a structural representation of the calcium carbonate product prepared in comparative example 3 of the present invention
FIG. 6 is a structural representation of the calcium carbonate product prepared in comparative example 4 of the present invention.
Detailed Description
The following description of the technical solution in the embodiments of the present invention is clear and complete. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, but the present invention may be practiced in other ways other than those described herein, and persons skilled in the art will readily appreciate that the present invention is not limited to the specific embodiments disclosed below.
Example 1 method for extracting dicyandiamide waste residue
The embodiment is a method for extracting dicyandiamide waste residues, as shown in fig. 1, specifically comprising the following steps in sequence:
s1, pulping
Adding dicyandiamide waste residue into a first-stage washing tank, adding a second-stage washing filtrate, stirring, washing and pulping in the first-stage washing tank to prepare slurry with the solid content of 20-25 wt% (the solid content of the slurry in the embodiment is 25 wt%), so that dicyandiamide and mono-cyanamide in the dicyandiamide waste residue are fully dissolved in water;
opening exciting current, adjusting the magnetic separation intensity of the magnetic separator to 180-200 mT (the magnetic separation intensity is 200mT in the embodiment), starting to inject slurry for magnetic separation, and collecting effluent after primary magnetic separation of the slurry;
by setting specific magnetic separation strength, metal substances such as ferric oxide, partial magnesium carbonate and the like in dicyandiamide waste residues are removed, and calcium element and dicyandiamide are not adsorbed, so that the subsequent treatment difficulty is reduced, the purity of the recovered dicyandiamide product and calcium carbonate product is improved, meanwhile, as only partial magnesium carbonate is adsorbed, the residual magnesium carbonate in slurry is converted into magnesium chloride in the subsequent preparation process of the calcium carbonate product, and the magnesium chloride is matched with chitosan to be used as a crystal form control agent, so that the generation of spherical calcium carbonate product is controlled.
Introducing carbon dioxide into an aeration tank to perform aeration treatment for 10-15 min, converting redundant calcium hydroxide in the system into calcium carbonate, further improving the purity of the recovered dicyandiamide and calcium carbonate, and preparing dicyandiamide waste residue slurry;
s2, multistage washing
Pumping dicyandiamide slag slurry into a primary cyclone through a primary transfer pump for washing, directly refluxing overflow liquid flowing out of the top of the primary cyclone into an aeration tank for circulating and pumping the overflow liquid into the primary cyclone, and dehydrating the dicyandiamide slag slurry at the bottom of the cyclone through a primary vacuum belt dehydrator to obtain a primary filter cake and primary washing filtrate; the dicyandiamide content in the first-stage filter cake is only 20-25 wt% of the dicyandiamide waste residue slurry.
The first-stage filter cake is conveyed into a second-stage washing tank by a belt conveyor to be stirred, washed and pulped, and the third-stage washing filtrate is used as washing water to prepare second-stage slurry, so that dicyandiamide and mono-cyanamide in the first-stage filter cake can be washed into water to a larger extent;
pumping the prepared secondary slurry into a secondary cyclone by a secondary slurry supply pump for washing, and refluxing overflow liquid at the top of the tertiary cyclone to a secondary washing tank, wherein concentrated slurry at the bottom of the secondary cyclone is dehydrated in a secondary vacuum belt dehydrator to obtain a secondary filter cake and secondary washing filtrate; the concentration of dicyandiamide and the concentration of mono-cyanamide in the secondary washing tank are slightly higher, and the source of dicyandiamide in the secondary washing tank is dicyandiamide carried by free water in the primary filter cake and dicyandiamide carried by the tertiary washing filtrate; the dicyandiamide content in the secondary filter cake is only 20-25% of the concentration of the secondary slurry.
The dicyandiamide concentration in the secondary washing filtrate is higher, and the secondary washing filtrate flows back to the primary washing tank to be used as washing water for pulping;
the secondary filter cake is conveyed to a tertiary washing tank by a belt conveyor to be stirred, washed and pulped, evaporated condensed water is used as washing water to prepare tertiary slurry, so that dicyandiamide and mono-cyanamide in dicyandiamide waste residues are washed to the water to the greatest extent, and the minimum amount of dicyandiamide in the waste residues is ensured;
pumping the prepared three-stage slurry into a three-stage cyclone by a three-stage slurry supply pump for washing, directly returning overflow liquid at the top of the three-stage cyclone to a three-stage washing tank, directly feeding concentrated slurry at the bottom of the three-stage cyclone into a three-stage vacuum belt dehydrator for dehydration, and obtaining a three-stage filter cake and three-stage washing filtrate.
The sources of dicyandiamide and mono-cyanamide contained in the tertiary washing filtrate are only dicyandiamide and mono-cyanamide carried by free water in the secondary filter cake, so that the concentration of the dicyandiamide and the mono-cyanamide contained in the tertiary washing filtrate is the lowest, and the dicyandiamide and the mono-cyanamide are refluxed to a secondary washing tank to be used as washing water for pulping;
s3, product recovery
Pumping the primary washing filtrate into a recovery tank by using a recovery pump, adding 30wt% ammonia water to adjust the pH value to 8.8-9.2 (adjusting the pH value to 9.0 in the embodiment), pumping into a low-pressure evaporation system by using a feed pump, maintaining the temperature at 70-75 ℃ for low-pressure evaporation concentration and single-cyanamide polymerization (maintaining the temperature at 72 ℃ in the embodiment), evaporating water in the primary washing filtrate by using heat and a negative pressure environment, further polymerizing the single-cyanamide in the primary washing filtrate by using heat and an alkaline environment to form dicyandiamide, further obtaining a dicyandiamide solution with the concentration of 13wt%, condensing the evaporated steam, and obtaining evaporated condensate water to flow back into a tertiary washing tank to be used as washing water for pulping.
The dicyandiamide solution with high concentration is cooled to below 5 ℃ for crystallization for more than 2 hours (the temperature of crystallization in the embodiment is 0 ℃ and the time is 3 hours), filtered and dried to obtain the dicyandiamide product with the purity of 98.76 percent and the recovery rate of 96.59 percent (the recovery rate is =the weight of the dicyandiamide product ≡the theoretical weight of dicyandiamide in the dicyandiamide waste residue multiplied by 100 percent).
And conveying the three-stage filter cake to a pulping pool by a belt conveyor, adding 20wt% of hydrochloric acid, stirring and dissolving, pulping, completely converting calcium carbonate into calcium chloride (when no bubble is generated, completely converting calcium carbonate into calcium chloride, stopping adding hydrochloric acid, simultaneously converting a small amount of magnesium carbonate in the three-stage filter cake into magnesium chloride), and filtering to obtain filtrate and a carbon product (the carbon product contains a small amount of silicon dioxide).
The filtrate is conveyed to a product pool through a liquid conveying pump, chitosan is added, the concentration of chitosan in the obtained solution is 6-8 g/L (the concentration of chitosan in the solution is 7g/L in the embodiment), stirring is carried out to dissolve, a small amount of magnesium chloride and chitosan contained in the filtrate are used as a crystal form control agent, the filtrate is heated to 50-55 ℃ (the temperature after heating in the embodiment is 52 ℃), 18-22 wt% of ammonium carbonate aqueous solution (the concentration of the ammonium carbonate aqueous solution in the embodiment is 20 wt%) is dropwise added, the stirring is continued at 50-55 ℃, the stirring speed is 400-450 r/min (the stirring speed in the embodiment is 420 r/min), spherical calcium carbonate precipitation is controlled, when no precipitation is generated, dropwise adding of the ammonium carbonate aqueous solution is stopped, stirring is continued for 10min, cooling, filtering and washing are carried out, and the spherical calcium carbonate product is obtained after drying, and the whiteness degree is 95.1, and the structural representation diagram is shown in figure 2.
EXAMPLES 2 to 6 extraction method of dicyandiamide waste residue
Examples 2 to 6 are respectively a method for extracting dicyandiamide waste residues, and the steps are basically the same as those of example 1, except that the raw material consumption and the technological parameters are different, and the specific details are shown in table 1:
table 1 list of process parameters in examples 2 to 6
The other parts of examples 2 to 6 are the same as in example 1.
Experimental example 1 comparative test of extraction method of dicyandiamide waste residue
Comparative examples 1 to 9 are comparative tests of the extraction method of dicyandiamide waste residue in example 1, differing only in that:
in the step S1 of the comparative example 1, the magnetic separation strength is 150mT, the purity of the obtained dicyandiamide product is 97.42%, the recovery rate is 95.87%, the whiteness of the obtained calcium carbonate product is 93.1, and the structural characterization diagram is shown in fig. 3, so that the regular spherical shape cannot be formed.
In the step S1 of the comparative example 2, the magnetic separation strength is 250mT, the purity of the obtained dicyandiamide product is 97.42%, the recovery rate is 95.87%, the whiteness of the obtained calcium carbonate product is 93.1, and the structural characterization diagram is shown in fig. 4, so that the regular spherical shape cannot be formed.
After chitosan is added in the step S3 of the comparative example 3, the concentration of chitosan in the obtained solution is 2g/L, the whiteness of the obtained calcium carbonate product is 93.7, and the structural characterization diagram is shown in fig. 5, so that the regular spherical shape cannot be formed.
After chitosan was added in step S3 of comparative example 4, the concentration of chitosan in the obtained solution was 15g/L, and the whiteness of the obtained calcium carbonate product was 92.6, and the structural characterization diagram thereof was as shown in FIG. 6, failing to form a regular sphere.
In the step S1 of the comparative example 5, carbon dioxide aeration is not performed, and the magnetic separation effluent liquid is directly used as dicyandiamide waste residue slurry for subsequent treatment, so that the purity of the obtained dicyandiamide product is 94.17%, the recovery rate is 94.66%, and the whiteness of the obtained calcium carbonate product is 93.4.
The multistage washing process of the dicyandiamide waste slurry in step S2 of comparative example 6 comprises the steps of:
after primary stirring and washing, the dicyandiamide waste residue slurry is subjected to filter pressing by a primary filter press to obtain a primary filter cake and primary washing filtrate;
preparing secondary slurry by taking the tertiary washing filtrate as washing water of the primary filter cake, and carrying out filter pressing by adopting a secondary filter press after secondary stirring and washing to obtain a secondary filter cake and secondary washing filtrate;
preparing a third-stage slurry of the second-stage filter cake by taking evaporated condensed water as washing water, and performing filter pressing by adopting a third-stage filter press after three-stage stirring and washing to obtain a third-stage filter cake and a third-stage washing filtrate;
other procedures were consistent with those in example 1, with a purity of 92.15% and a recovery of 87.56% for the dicyandiamide product and a whiteness of 91.7 for the calcium carbonate product.
The primary washing filtrate in the step S3 of the comparative example 7 is directly injected into a low-pressure evaporation system without adjusting the pH value by ammonia water to perform low-pressure evaporation concentration and cyanamide polymerization, the purity of the finally obtained dicyandiamide product is 82.75%, the recovery rate is 86.24%, and the whiteness of the obtained calcium carbonate product is 94.6.
Adding 30wt% ammonia water into the primary washing filtrate in the step S3 of the comparative example 8 to adjust the pH value to 10.0, pumping the primary washing filtrate into a low-pressure evaporation system to perform low-pressure evaporation concentration and cyanamide polymerization, wherein the purity of the finally obtained dicyandiamide product is 87.64%, the recovery rate is 89.52%, and the whiteness of the obtained calcium carbonate product is 95.0.
The temperature of low-pressure evaporation concentration and cyanamide polymerization in step S3 of comparative example 9 was 50 ℃, the purity of the obtained dicyandiamide product was 87.64%, the recovery rate was 72.93%, and the whiteness of the obtained calcium carbonate product was 94.7.
It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Claims (10)
1. The extraction method of dicyandiamide waste residues is characterized by comprising the following steps:
s1, pulping
Preparing dicyandiamide waste residue into slurry, carrying out magnetic separation and enrichment, collecting effluent, and then introducing carbon dioxide for treatment to prepare dicyandiamide waste residue slurry;
s2, multistage washing
The dicyandiamide waste residue slurry is subjected to multistage washing to obtain primary washing filtrate and multistage filter cakes;
s3, product recovery
Adjusting the pH value of the primary washing filtrate to 8.8-9.2 by ammonia water, performing low-pressure evaporation concentration and cyanamide polymerization at 70-75 ℃, crystallizing and filtering the obtained high-concentration dicyandiamide solution to obtain a dicyandiamide product;
dissolving the multistage filter cake by hydrochloric acid, and filtering to obtain filtrate and a carbon product;
adding chitosan into the filtrate, and adding ammonium carbonate to obtain spherical calcium carbonate product.
2. The method for extracting dicyandiamide waste residue according to claim 1, wherein in the step S1, the magnetic separation strength of the magnetic separation enrichment is 180-200 mt.
3. The method for extracting dicyandiamide waste residue according to claim 1 or 2, wherein in step S2, the multistage washing comprises the steps of:
taking dicyandiamide waste residue slurry, washing by a primary cyclone and dehydrating by a primary vacuum belt dehydrator to obtain a primary filter cake and primary washing filtrate;
pulping the first-stage filter cake by using the third-stage washing filtrate, washing by using a second-stage cyclone, and dehydrating by using a second-stage vacuum belt dehydrator to obtain a second-stage filter cake and a second-stage washing filtrate; the second-stage washing filtrate is used as washing water to pulp the dicyandiamide waste residue in the step S1;
washing the second-stage filter cake by a third-stage cyclone and dehydrating by a third-stage vacuum belt dehydrator to obtain a third-stage filter cake and a third-stage washing filtrate; the third-stage washing filtrate is used as washing water to pulp the first-stage filter cake; and the three-stage filter cake is the multi-stage filter cake.
4. The method for extracting dicyandiamide waste residue according to claim 3, wherein in the step S3, the evaporated steam is condensed in the low-pressure evaporation concentration and the polymerization process of the dicyandiamide, and the obtained evaporated condensed water is used as washing water to pulp the secondary filter cake.
5. The method for extracting dicyandiamide waste residue according to claim 1, 2 or 4, wherein in the step S3, the concentration of the dicyandiamide solution is 12-14wt%.
6. The method for extracting dicyandiamide waste residue according to claim 1, 2 or 4, wherein in the step S3, the concentration of chitosan in the obtained solution is 6-8 g/L after chitosan is added and before ammonium carbonate is added.
7. The method for extracting dicyandiamide waste residue according to claim 1, 2 or 4, wherein in the step S3, the temperature of the obtained system is 50-55 ℃ in the process of adding ammonium carbonate.
8. The method for extracting dicyandiamide waste residue according to claim 1, 2 or 4, wherein in the step S3, the obtained system is stirred at a stirring speed of 400-450 r/min during the addition of ammonium carbonate.
9. The method for extracting dicyandiamide waste residue according to claim 1, 2 or 4, wherein in the step S3, an aqueous solution of ammonium carbonate having a concentration of 18 to 22wt% is used.
10. The method for extracting dicyandiamide waste residue according to claim 1, 2 or 4, wherein in the step S1, the solid content of the slurry prepared from the dicyandiamide waste residue is 20-25 wt%.
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