CN112250049B - Separation method of hydrazine hydrate byproduct saline-alkali by urea method - Google Patents
Separation method of hydrazine hydrate byproduct saline-alkali by urea method Download PDFInfo
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- CN112250049B CN112250049B CN202011012965.4A CN202011012965A CN112250049B CN 112250049 B CN112250049 B CN 112250049B CN 202011012965 A CN202011012965 A CN 202011012965A CN 112250049 B CN112250049 B CN 112250049B
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- C01B21/00—Nitrogen; Compounds thereof
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- C01B21/16—Hydrazine; Salts thereof
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- C—CHEMISTRY; METALLURGY
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- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D3/00—Halides of sodium, potassium or alkali metals in general
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- C01D7/00—Carbonates of sodium, potassium or alkali metals in general
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Abstract
The invention discloses a separation method of a byproduct saline-alkali of hydrazine hydrate by a urea method. The method comprises the following steps: (1) Freezing the crude hydrazine hydrate solution produced by the urea method to crystallize and centrifugally separating to obtain sodium carbonate decahydrate and mother liquor II; (2) Washing the byproduct salt and alkali of hydrazine hydrate by the urea method with a washing solution at 30-50 ℃, and centrifugally filtering to obtain crude sodium chloride salt and mother liquor I; the washing liquid is a mixture of mother liquid I and mother liquid II which are recycled; (3) Adding saturated sodium chloride brine into the sodium chloride crude salt to prepare slurry, adjusting the pH to 7-8 by hydrochloric acid, and centrifugally filtering to obtain refined sodium chloride. The method forms a byproduct salt and alkali recycling treatment system, which can efficiently separate and purify sodium chloride in salt and alkali to purity of more than 99wt%, reduces the loss of hydrazine hydrate and reduces the production cost. And the washing circulation system is connected with the refrigeration system, so that an independent washing mother liquor refrigeration system is not needed to be additionally built, and the equipment investment is reduced.
Description
Technical Field
The invention relates to the technical field of chemical industry saline-alkali separation, in particular to a separation method of hydrazine hydrate byproduct saline-alkali by a urea method.
Background
Hydrazine hydrate and hydrazine salt (comprising hydrazine hydrochloride and hydrazine sulfate) are important chemical raw materials and are widely applied to the production of medicines, pesticides and plastic rubber foaming agents ADC. The existing and mature hydrazine hydrate production process mainly comprises a ketazine process and a urea sodium hypochlorite oxidation process, and the urea sodium hypochlorite oxidation method has the advantages of low investment, simple equipment, most mature process, easy mastering of technology and the like, so that the main hydrazine hydrate, hydrazine salt and ADC foaming agent production process in China mainly comprises the urea sodium hypochlorite oxidation method process, and the process comprises the following steps:
the chlorine and caustic soda react to obtain sodium hypochlorite, then the sodium hypochlorite reacts with urea and caustic soda to obtain crude hydrazine hydrate solution (hereinafter referred to as crude hydrazine) with hydrazine content of 4-6wt%, the solution also contains 12-17wt% of sodium chloride, 10-14wt% of sodium carbonate and 0.1-3wt% of sodium hydroxide, sodium carbonate decahydrate can be separated out by freezing and crystallizing the crude hydrazine solution (the amount of the separated sodium carbonate decahydrate is about 50-70wt%) and the chemical reaction equation is as follows:
2NaOH+Cl 2 →NaC1O+NaCl+H 2 O
NaClO+(NH 2 ) 2 CO+2NaOH→N 2 H 4 ·H 2 O+NaCl+Na 2 CO 3
Na 2 CO 3 +10H 2 O→Na 2 CO 3 ·10H 2 O
the crude hydrazine is recovered with sodium carbonate decahydrate to obtain refined hydrazine hydrate solution (hereinafter referred to as 'refined hydrazine'), and the refined hydrazine still contains a large amount of sodium chloride and part of sodium carbonate, and is carried into a post-system along with refined hydrazine, so that the salt content in the system is further improved. For this reason, more and more enterprises now pre-extract sodium chloride and sodium carbonate by evaporating refined hydrazine so as to reduce the processing burden of the subsequent procedures. However, the availability of the extracted sodium chloride and sodium carbonate is relatively low if the sodium chloride and the sodium carbonate are not separated, so that the research has important significance for separating mixed salt of the sodium chloride and the sodium carbonate.
In theory, a small amount of sodium carbonate in the mixed salt can be washed away by using the water solution of the nearly saturated sodium chloride salt, and the main reason is that the solubility of the water sodium chloride of the nearly saturated sodium chloride salt is nearly saturated, so that the sodium chloride is difficult to dissolve again, and a small amount of sodium carbonate can be dissolved so as to achieve the purpose of separating the salt and the alkali. However, the method is used for separating the byproduct salt and alkali of hydrazine hydrate by the urea method, and has the main defects that: firstly, the system can not be shared with the existing crude hydrazine freezing and sodium carbonate recovery system, and a set of freezing device special for recovering sodium carbonate from brine washing liquid needs to be newly built; in the cyclic washing process of the washing liquid, the useful component hydrazine hydrate in the washing liquid is gradually accumulated, and the part of hydrazine hydrate is difficult to recycle, so that the loss of the hydrazine hydrate is caused; thirdly, in the circulating washing process of the washing liquid, sodium hydroxide is gradually accumulated, and due to the existence of sodium ions, the co-dissolution balance of sodium chloride and sodium carbonate is unstable.
A saline-alkali separation and recycling technology of waste salt and alkaline residues in the production of the hydrazine hydrate with the application number of 200410047148.7 and the application date of 2004.12.29; the technology of the patent utilizes water and mother liquor to add sodium bicarbonate for washing mixed salt, the technology supplements part of water in the mixed salt for washing, the amount of dissolved sodium chloride is more, the sodium chloride loss is large, and the sodium bicarbonate is added for neutralizing sodium hydroxide in the mixed salt, so that the material consumption is high, and the washing process and the washing cost are increased. The patent uses the gravity difference of salt slurry and alkali slurry to separate by using a classification device, and the separation device has high requirement and is difficult to industrialize.
The separation (namely salt washing) method of byproduct saline-alkali (hereinafter referred to as saline-alkali) of hydrazine hydrate by the urea method is that industrial water is used for preparing washing liquid for washing, and the content of sodium carbonate in the saline-alkali which can be effectively treated is less than 5wt%. The washing liquid is specially prepared and is not recycled, so that the treatment process is complex and the cost is high.
Disclosure of Invention
The invention aims to provide a separation method of a byproduct saline-alkali of hydrazine hydrate by a urea method. The specific technical scheme is as follows:
a separation method of byproduct saline-alkali of hydrazine hydrate by urea method comprises the following steps:
(1) Freezing the crude hydrazine hydrate solution produced by the urea method to crystallize and centrifugally separating to obtain sodium carbonate decahydrate and mother liquor II;
(2) Washing the byproduct salt and alkali of the hydrazine hydrate by the solid urea method with a washing solution at 30-50 ℃, and centrifugally filtering to obtain solid sodium chloride crude salt and mother liquor I; the washing liquid is a mixture of mother liquid I and mother liquid II which are recycled, the mass ratio of the saline and alkaline to the mother liquid II is 1:1.7-3.5, and the saline and alkaline accounts for 15-30% of the total volume of the saline and alkaline washing liquid;
(3) Adding saturated sodium chloride brine into the solid sodium chloride crude salt obtained in the step (2) to prepare slurry, wherein the solid phase in the slurry accounts for 15-30% of the total volume, dropwise adding hydrochloric acid into the slurry to adjust the pH to 7-8, and centrifugally filtering to obtain refined sodium chloride and mother liquor III.
Preferably, the method further comprises: freezing the mother liquor I which is not used in washing by a freezing system until crystallization and centrifugal separation are carried out, thus obtaining sodium carbonate decahydrate and mother liquor II; inputting mother liquor II which is not used in washing into a production system; mother liquor III is added into the slurry in the step (3) for recycling.
Preferably, the crude hydrazine hydrate solution and mother liquor I both contain 12 to 17wt% sodium chloride and 10 to 14wt% sodium carbonate, and the mother liquor II contains 15 to 20wt% sodium chloride and 3 to 7wt% sodium carbonate.
Preferably, the temperature of the freezing in the step (1) is-10-15 ℃.
Preferably, the saline alkali consists of 50-74 wt% of sodium chloride, 15-30 wt% of sodium carbonate, 4-8 wt% of hydrazine hydrate and 7-16 wt% of impurities.
Preferably, the flow rate of the washing liquid in the step (2) is 3-6 m/h.
The beneficial effects of the invention are that
According to the invention, crude hydrazine hydrate solution produced by a urea method is frozen to be crystallized and centrifugally separated to obtain sodium carbonate decahydrate and mother liquor II, the mother liquor I and the mother liquor II are circularly washed to generate mother liquor I, the mother liquor I and the mother liquor II are mixed to form circulating washing liquid to wash salt and alkali, sodium carbonate and impurity NaOH in the salt and alkali are washed into the washing liquid, one part of the washed mother liquor I after centrifugal filtration enters a salt washing device for salt washing, the other part of the washed mother liquor I enters a freezing system for freezing crystallization and centrifugal filtration to obtain sodium carbonate decahydrate and the mother liquor II, one part of the mother liquor II enters the salt washing device for salt washing, and the other part of the mother liquor II enters a production system. In addition, mother liquor III obtained after the solid sodium chloride crude salt is pulped, neutralized, crystallized and centrifugally filtered is added into the slurry for recycling. Thus forming a saline-alkali circulation treatment system. The method can efficiently separate and purify the sodium chloride in the saline alkali to the purity of more than 99 weight percent, reduces the loss of hydrazine hydrate in a production system and reduces the production cost.
When salt is washed, the solid phase and the liquid phase are in large-area countercurrent contact under the action of circulating washing liquid, and the salt and alkali separation efficiency is high. And the washing circulation system is connected with the refrigeration system, so that an independent washing mother liquor refrigeration system is not needed to be additionally built, and the equipment investment is reduced.
In addition, the refined hydrazine (mother liquor II) and the crude hydrazine exchange heat through a heat exchanger, and the refined hydrazine and the crude hydrazine are cooled to Wen Cujing ℃ above 70 ℃ from a production system and then sent to a freezing process, so that the energy consumption of the freezing process is reduced; meanwhile, the temperature of refined hydrazine is increased, and the refined hydrazine is fed into salt washing equipment to serve as washing liquid without additional heating, so that the energy consumption is reduced.
Drawings
FIG. 1 is a flow chart of an embodiment of the present invention.
Detailed Description
The process flows of examples 1-3 are shown in FIG. 1.
Wherein, the crude hydrazine hydrate solution (crude hydrazine) produced by the urea method is cooled, frozen to be crystallized and centrifugally separated to obtain mother liquor II.
The washing liquid used in the first washing cycle consists of mother liquor II, and the washing liquid after the second washing cycle consists of mother liquor I and mother liquor II. Thus, the salt and alkali are circularly treated. Examples 1-3 illustrate the situation after the second wash cycle.
Example 1
(1) The crude hydrazine hydrate solution (crude hydrazine, the temperature of which can reach more than 70 ℃) newly produced by the urea method is cooled by a heat exchanger and then sent to a refrigeration system for refrigeration at the temperature of minus 10 ℃ to be crystallized and centrifugally separated, so as to obtain sodium carbonate decahydrate and mother liquor II (the content of hydrazine hydrate is 4.7 to 7.4 weight percent, the content of sodium chloride is 15 to 20 weight percent and the content of sodium carbonate is 3 to 7 weight percent).
(2) In salt washing equipment, 200.1g of solid hydrazine hydrate byproduct salt and alkali (55.77 wt% of sodium chloride, 25.95wt% of sodium carbonate, 6.79wt% of hydrazine hydrate and the balance of impurities) is washed by a washing liquid at 30 ℃ (the flow rate of the washing liquid is 3-6 m/h), and centrifugal filtration is carried out to obtain 111.9g of solid crude sodium chloride (92.61 wt% of sodium chloride, 2.11wt% of sodium carbonate, 0.51wt% of hydrazine hydrate and the balance of impurities) and mother liquor I (4-6 wt% of hydrazine hydrate, 12-17 wt% of sodium chloride and 10-14 wt% of sodium carbonate);
wherein the washing liquid is a mixture of mother liquor I and mother liquor II which are recycled, the mass of the mother liquor II is 340.3g, and the volume ratio of the saline alkali to the washing liquid is 15:85; freezing the mother liquor I which is not used in washing to be crystallized by a freezing system at the temperature of minus 10 ℃ and centrifugally separating to obtain sodium carbonate decahydrate and mother liquor II; the unused mother liquor II is input into the production system.
(3) Adding solid sodium chloride crude salt into a neutralization pulping tank, adding saturated sodium chloride brine to prepare slurry with a solid-liquid volume ratio of 15:85, dropwise adding 4.6ml of hydrochloric acid with a concentration of 31wt% into the slurry to adjust the pH to 7-8, centrifugally filtering to obtain refined sodium chloride (the sodium chloride content is 99.1wt% and the sodium carbonate content is 0.15 wt%) and mother liquor III, and adding the mother liquor III into the neutralization pulping tank for recycling.
Example 2
(1) The crude hydrazine hydrate solution (crude hydrazine, the temperature of which can reach more than 70 ℃) newly produced by the urea method is cooled by a heat exchanger and then sent to a freezing system for 0 ℃ for freezing until crystallization and centrifugal separation, so that sodium carbonate decahydrate and mother liquor II (the content of hydrazine hydrate is 4.7-7.4 wt%, the content of sodium chloride is 15-20 wt% and the content of sodium carbonate is 3-7 wt%) are obtained.
(2) In salt washing equipment, 199.9g of solid hydrazine hydrate byproduct salt and alkali (with the content of 59.78wt% of sodium chloride, 21.71wt% of sodium carbonate, 5.29wt% of hydrazine hydrate and the balance of impurities) is washed by a washing liquid with the temperature of 40 ℃ (the flow rate of the washing liquid is 3-6 m/h), and centrifugal filtration is carried out to obtain 117.6g of solid crude sodium chloride (with the content of 93.53wt% of sodium chloride, 0.52wt% of sodium carbonate, 0.35wt% of hydrazine hydrate and the balance of impurities) and mother liquor I (with the content of hydrazine being 4-6 wt%, the content of sodium chloride being 12-17 wt% and the content of sodium carbonate being 10-14 wt%);
wherein the washing liquid is a mixture of mother liquor I and mother liquor II which are recycled, the mass of the mother liquor II is 700.1g, and the volume ratio of the saline alkali to the washing liquid is 30:70; freezing the mother liquor I which is not used in washing to be crystallized by a freezing system at 0 ℃ and centrifugally separating to obtain sodium carbonate decahydrate and mother liquor II; the unused mother liquor II is input into the production system.
(3) Adding solid sodium chloride crude salt into a neutralization pulping tank, adding saturated sodium chloride brine to prepare slurry with a solid-liquid volume ratio of 30:70, dropwise adding 1.2ml of hydrochloric acid with a concentration of 31wt% into the slurry to adjust the pH to 7-8, centrifugally filtering to obtain refined sodium chloride (the sodium chloride content is 99.3wt% and the sodium carbonate content is 0.11 wt%) and mother liquor III, and adding the mother liquor III into the neutralization pulping tank for recycling.
Example 3
(1) The crude hydrazine hydrate solution (crude hydrazine, the temperature of which can reach more than 70 ℃) newly produced by the urea method is cooled by a heat exchanger and then sent to a refrigerating system for refrigerating at 15 ℃ until crystallization and centrifugal separation are carried out, so that sodium carbonate decahydrate and mother liquor II (the content of hydrazine hydrate is 4.7-7.4 wt%, the content of sodium chloride is 15-20 wt% and the content of sodium carbonate is 3-7 wt%) are obtained.
(2) In salt washing equipment, 200.2g of solid hydrazine hydrate byproduct salt and alkali (61.15 wt% of sodium chloride, 20.37wt% of sodium carbonate, 5.31wt% of hydrazine hydrate and the balance of impurities) is washed by washing liquid at 50 ℃ (the flow rate of the washing liquid is 3-6 m/h), and centrifugal filtration is carried out to obtain 118.7g of solid crude sodium chloride (94.18 wt% of sodium chloride, 0.84wt% of sodium carbonate, 0.16wt% of hydrazine hydrate and the balance of impurities) and mother liquor I (4-6 wt% of hydrazine hydrate, 12-17 wt% of sodium chloride and 10-14 wt% of sodium carbonate);
wherein the washing liquid is a mixture of mother liquor I and mother liquor II which are recycled, the mass of the mother liquor II is 600.1g, and the volume ratio of the saline alkali to the washing liquid is 20:80; freezing the mother liquor I which is not used in washing by a freezing system at 15 ℃ until crystallization and centrifugal separation are carried out, thus obtaining sodium carbonate decahydrate and mother liquor II; the unused mother liquor II is input into the production system.
(3) Adding solid sodium chloride crude salt into a neutralization pulping tank, adding saturated sodium chloride brine to prepare slurry with the solid-liquid volume ratio of 20:80, dropwise adding 2.0ml of hydrochloric acid with the concentration of 31wt% into the slurry to adjust the pH to 7-8, centrifugally filtering to obtain refined sodium chloride (the sodium chloride content is 99.2wt% and the sodium carbonate content is 0.11 wt%) and mother liquor III, and adding the mother liquor III into the neutralization pulping tank for recycling.
Claims (3)
1. The method for separating the byproduct saline-alkali from the hydrazine hydrate by the urea method is characterized by comprising the following steps of:
(1) Freezing the crude hydrazine hydrate solution produced by the urea method to crystallize and centrifugally separating to obtain sodium carbonate decahydrate and mother liquor II;
(2) Washing the byproduct salt and alkali of the hydrazine hydrate by the solid urea method with a washing solution at 30-50 ℃, and centrifugally filtering to obtain solid sodium chloride crude salt and mother liquor I; the washing liquid is a mixture of mother liquid I and mother liquid II which are recycled, the mass ratio of the saline and alkaline to the mother liquid II is 1:1.7-3.5, and the saline and alkaline accounts for 15-30% of the total volume of the saline and alkaline washing liquid;
(3) Adding saturated sodium chloride brine into the solid sodium chloride crude salt obtained in the step (2) to prepare slurry, wherein the solid phase in the slurry accounts for 15-30% of the total volume, dropwise adding hydrochloric acid into the slurry to adjust the pH to 7-8, and centrifugally filtering to obtain refined sodium chloride and mother liquor III;
further comprises: freezing the mother liquor I which is not used in washing by a freezing system until crystallization and centrifugal separation are carried out, thus obtaining sodium carbonate decahydrate and mother liquor II; inputting mother liquor II which is not used in washing into a production system; adding mother liquor III into the slurry obtained in the step (3) for recycling;
the crude hydrazine hydrate solution and the mother solution I both contain 12-17 wt% of sodium chloride and 10-14 wt% of sodium carbonate, and the mother solution II contains 15-20 wt% of sodium chloride and 3-7 wt% of sodium carbonate;
the saline-alkali consists of 50-74 wt% of sodium chloride, 15-30 wt% of sodium carbonate, 4-8 wt% of hydrazine hydrate and 7-16 wt% of impurities.
2. The method for separating byproduct saline-alkali from hydrazine hydrate by the urea method according to claim 1, wherein the freezing temperature in the step (1) is-10-15 ℃.
3. The method for separating byproduct salt and alkali from hydrazine hydrate by the urea method according to claim 1, wherein the flow rate of the washing liquid in the step (2) is 3-6 m/h.
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| CN100389892C (en) * | 2005-10-13 | 2008-05-28 | 宜宾天原股份有限公司 | Recovering treatment of hydrated hydrazine by-product saline-alkali by urea method |
| CN104892463A (en) * | 2015-04-16 | 2015-09-09 | 杭州海虹精细化工有限公司 | Process for producing biurea through optimized urea method |
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