CN112250049A - Method for separating saline and alkaline byproduct of hydrazine hydrate by urea method - Google Patents
Method for separating saline and alkaline byproduct of hydrazine hydrate by urea method Download PDFInfo
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- CN112250049A CN112250049A CN202011012965.4A CN202011012965A CN112250049A CN 112250049 A CN112250049 A CN 112250049A CN 202011012965 A CN202011012965 A CN 202011012965A CN 112250049 A CN112250049 A CN 112250049A
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- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B21/00—Nitrogen; Compounds thereof
- C01B21/082—Compounds containing nitrogen and non-metals and optionally metals
- C01B21/16—Hydrazine; Salts thereof
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- 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
- C01D3/14—Purification
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D7/00—Carbonates of sodium, potassium or alkali metals in general
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Abstract
The invention discloses a method for separating saline from a hydrazine hydrate byproduct by a urea method. The method comprises the following steps: (1) freezing the rough 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 urea-process hydrazine hydrate with a washing solution at 30-50 ℃, and centrifugally filtering to obtain sodium chloride crude salt and a mother solution I; the washing liquid is a mixture of a mother liquid I and a mother liquid II which are recycled; (3) and adding saturated sodium chloride brine into the crude sodium chloride salt to prepare slurry, adjusting the pH to 7-8 with hydrochloric acid, and performing centrifugal filtration to obtain the refined sodium chloride. The method forms a circular treatment system of byproduct salt and alkali, can efficiently separate and purify sodium chloride in the salt and alkali to the purity of over 99 wt%, reduces the loss of hydrazine hydrate, and reduces the production cost. And the washing circulation system is linked with the freezing system, so that an additional set of separate washing mother liquor freezing system is not required, and the equipment investment is reduced.
Description
Technical Field
The invention relates to the technical field of separation of saline and alkali in chemical industry, in particular to a method for separating saline and alkali from a hydrazine hydrate byproduct by a urea method.
Background
Hydrazine hydrate and hydrazine salt (including 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 main mature hydrazine hydrate production process at the present stage comprises a ketazine process and a urea sodium hypochlorite oxidation process, and the urea sodium hypochlorite oxidation process has the advantages of low investment, simple equipment, mature process, easy mastering of the technology and the like, so the main hydrazine hydrate, hydrazine salt and ADC foaming agent production process in China mainly comprises the urea sodium hypochlorite oxidation process, and the process flow is as follows:
reacting chlorine and caustic soda to obtain sodium hypochlorite, reacting the sodium hypochlorite with urea and caustic soda to obtain a rough hydrazine hydrate solution (hereinafter referred to as 'rough hydrazine') with hydrazine hydrate content of 4-6 wt%, wherein the solution also contains 12-17 wt% of sodium chloride, 10-14 wt% of sodium carbonate and 0.1-3 wt% of sodium hydroxide, and freezing and crystallizing the rough hydrazine solution to separate out sodium carbonate decahydrate (the amount of the separated sodium carbonate decahydrate is about 50-70 wt% of the total amount), and the chemical reaction equation is as follows:
2NaOH+Cl2→NaC1O+NaCl+H2O
NaClO+(NH2)2CO+2NaOH→N2H4·H2O+NaCl+Na2CO3
Na2CO3+10H2O→Na2CO3·10H2O
the crude hydrazine is recycled to obtain refined hydrazine hydrate solution (hereinafter referred to as refined hydrazine) after sodium carbonate decahydrate, and the refined hydrazine still contains a large amount of sodium chloride and part of sodium carbonate and is carried into a rear system along with the refined hydrazine, so that the salt content in the system is further improved. Therefore, more and more enterprises adopt a mode of evaporating the refined hydrazine to pre-extract the sodium chloride and the sodium carbonate so as to reduce the treatment burden of the subsequent process. However, if sodium chloride and sodium carbonate are extracted and not separated, the availability is low, so that the research has important significance for separating mixed salt of sodium chloride and sodium carbonate.
Theoretically, a small amount of sodium carbonate in the mixed salt can be washed away by using a nearly saturated sodium chloride aqueous solution, the main reason is that the solubility of sodium chloride is nearly saturated, the sodium chloride is difficult to dissolve again, and the small amount of sodium carbonate can be dissolved so as to achieve the purpose of salt and alkali separation. However, the method is used for separating the saline from the byproduct of hydrazine hydrate by the urea method, and has the following main defects: firstly, the system can not be shared with the existing crude hydrazine freezing sodium carbonate recovery system, and a set of freezing device special for recovering sodium carbonate from saline washing liquid needs to be newly built; secondly, in the circulating washing process of the washing liquid, useful components of hydrazine hydrate in the washing liquid are 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 washing process of the washing liquid circulation, sodium hydroxide is gradually accumulated, and the sodium chloride and sodium carbonate are instable in codissolving balance due to the existence of sodium ions.
Application No. 200410047148.7, application No. 2004.12.29, name hydrazine hydrate production waste salt alkali slag salt alkali separation and cyclic utilization technology; the patent technology utilizes water, mother liquor and baking soda to wash mixed salt, part of water is supplemented into the mixed salt for washing, the amount of dissolved sodium chloride is large, the loss of sodium chloride is large, the sodium bicarbonate is supplemented for neutralizing the sodium hydroxide in the mixed salt, the material consumption is high, and the washing process and the washing cost are increased. Application No. 200510021859.1, application date 2005.10.13, name urea method hydrazine hydrate byproduct salt and alkali recovery processing method, this patent utilizes salt thick liquid, alkali thick liquid gravity difference, adopts the classification equipment to separate, requires highly to the separation equipment, is difficult to the industrialization.
The present common method for separating (salt washing) the byproduct salt and alkali (hereinafter referred to as salt and alkali) of hydrazine hydrate by urea method is to use industrial water to prepare washing liquid for washing, and the content of sodium carbonate in the salt and alkali which can be effectively treated is less than 5 wt%. The washing liquid needs to be specially prepared and is not recycled, so that the treatment process is complex and high in cost.
Disclosure of Invention
The invention aims to provide a method for separating a hydrazine hydrate byproduct salt and alkali by a urea method. The specific technical scheme is as follows:
a method for separating saline from an byproduct of hydrazine hydrate by a urea method comprises the following steps:
(1) freezing the rough hydrazine hydrate solution produced by the urea method to crystallize and centrifugally separating to obtain sodium carbonate decahydrate and mother liquor II;
(2) washing solid-state urea-process hydrazine hydrate byproduct salt and alkali with a washing solution at the temperature of 30-50 ℃, and centrifugally filtering to obtain solid sodium chloride crude salt and a mother solution I; the washing liquid is a mixture of a mother liquid I and a mother liquid II which are recycled, the mass ratio of the salt and the alkali to the mother liquid II is 1: 1.7-3.5, and the salt and the alkali account for 15-30% of the total volume of the salt and the washing liquid;
(3) and (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 value to 7-8, and performing centrifugal filtration to obtain refined sodium chloride and mother liquor III.
Preferably, the method further comprises the following steps: freezing the unused mother liquor I in washing to crystallize by using a freezing system and carrying out centrifugal separation to obtain sodium carbonate decahydrate and mother liquor II; inputting the unused mother liquor II in washing into a production system; and (4) adding the mother liquor III into the slurry obtained in the step (3) for recycling.
Preferably, the crude hydrazine hydrate solution and the mother liquor I both contain 12-17 wt% of sodium chloride and 10-14 wt% of sodium carbonate, and the mother liquor II contains 15-20 wt% of sodium chloride and 3-7 wt% of sodium carbonate.
Preferably, the freezing temperature 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 speed of the washing liquid in the step (2) during washing is 3-6 m/h.
The invention has the advantages of
The invention freezes the rough hydrazine hydrate solution produced by urea method to crystallize and centrifugalize to obtain sodium carbonate decahydrate and mother liquor II, the mother liquor I is produced by circular washing, the mother liquor I and the mother liquor II are mixed to form circular washing liquid to wash saline alkali, the sodium carbonate and impurity NaOH in the saline alkali are washed into the washing liquid, one part of the washed and centrifugalized mother liquor I enters salt washing equipment for salt washing, the other part enters a freezing system to freeze, crystallize and centrifugalized to obtain sodium carbonate decahydrate and mother liquor II, one part of the mother liquor II enters the salt washing equipment for salt washing, and the other part enters a production system. In addition, mother liquor III obtained after solid sodium chloride crude salt pulping, neutralization crystallization and centrifugal filtration is added into the slurry for recycling. Thus forming a saline-alkali recycling treatment system. The sodium chloride in the saline alkali can be efficiently separated and purified to the purity of more than 99 wt%, the loss of hydrazine hydrate in a production system is reduced, and the production cost is reduced.
When salt is washed, the solid phase and the liquid phase are in large-area countercurrent contact under the action of the circulating washing liquid, and the salt and alkali separation efficiency is high. And the washing circulation system is linked with the freezing system, so that an additional set of separate washing mother liquor freezing system is not required, 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 crude hydrazine with the high temperature of more than 70 ℃ from the production system is cooled firstly and then sent to the freezing process, so that the energy consumption of the freezing process is reduced; meanwhile, the temperature of the refined hydrazine is increased, and the refined hydrazine is sent to salt washing equipment to be used 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 flow for examples 1-3 is 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 saline alkali is circularly treated. Examples 1-3 describe the situation after the second wash cycle.
Example 1
(1) Cooling a crude hydrazine hydrate solution (crude hydrazine, the temperature can reach more than 70 ℃) newly produced by a urea method through a heat exchanger, then sending the solution to a freezing system for freezing at the temperature of-10 ℃ to crystallize, and centrifugally separating to obtain sodium carbonate decahydrate and a mother solution 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%).
(2) In salt washing equipment, 200.1g of solid urea-process hydrazine hydrate byproduct saline alkali (the content of sodium chloride is 55.77 wt%, the content of sodium carbonate is 25.95 wt%, the content of hydrazine hydrate is 6.79 wt%, and the balance is 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 sodium chloride crude salt (the content of sodium chloride is 92.61 wt%, the content of sodium carbonate is 2.11 wt%, the content of hydrazine hydrate is 0.51 wt%, and the balance is impurities) and mother liquor I (the content of hydrazine hydrate is 4-6 wt%, the content of sodium chloride is 12-17 wt%, and the content of sodium carbonate is 10-14 wt%);
wherein the washing liquid is a mixture of recycled mother liquid I and mother liquid II, the mass of the mother liquid II is 340.3g, and the volume ratio of the salt and the alkali to the washing liquid is 15: 85; freezing the unused mother liquor I by using a freezing system at the temperature of-10 ℃ until crystallization and performing centrifugal separation to obtain sodium carbonate decahydrate and mother liquor II; and inputting the unused mother liquor II into a 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 31 wt% into the slurry to adjust the pH to 7-8, performing centrifugal filtration to obtain refined sodium chloride (the sodium chloride content is 99.1 wt%, 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) Cooling a crude hydrazine hydrate solution (crude hydrazine, the temperature can reach more than 70 ℃) newly produced by a urea method through a heat exchanger, then sending the solution to a freezing system for freezing at 0 ℃ until crystallization, and carrying out centrifugal separation to obtain sodium carbonate decahydrate and a mother solution 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%).
(2) In salt washing equipment, 199.9g of solid urea-process hydrazine hydrate byproduct salt and alkali (the content of sodium chloride is 59.78 wt%, the content of sodium carbonate is 21.71 wt%, the content of hydrazine hydrate is 5.29 wt%, and the balance is impurities) are washed by a washing solution at 40 ℃ (the flow rate of the washing solution is 3-6 m/h), and centrifugal filtration is carried out to obtain 117.6g of solid sodium chloride crude salt (the content of sodium chloride is 93.53 wt%, the content of sodium carbonate is 0.52 wt%, the content of hydrazine hydrate is 0.35 wt%, and the balance is impurities) and mother liquor I (the content of hydrazine hydrate is 4-6 wt%, the content of sodium chloride is 12-17 wt%, and the content of sodium carbonate is 10-14 wt%);
wherein the washing liquid is a mixture of recycled mother liquid I and mother liquid II, the mass of the mother liquid II is 700.1g, and the volume ratio of the salt and the alkali to the washing liquid is 30: 70; freezing the unused mother liquor I in washing by using a freezing system at 0 ℃ until crystallization and performing centrifugal separation to obtain sodium carbonate decahydrate and mother liquor II; and inputting the unused mother liquor II into a 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 31 wt% into the slurry to adjust the pH to 7-8, performing centrifugal filtration to obtain refined sodium chloride (the sodium chloride content is 99.3 wt%, 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) Cooling a crude hydrazine hydrate solution (crude hydrazine, the temperature can reach more than 70 ℃) newly produced by a urea method through a heat exchanger, then sending the solution to a freezing system for 15 ℃ for freezing until crystallization, and carrying out centrifugal separation to obtain sodium carbonate decahydrate and a mother solution 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%).
(2) In salt washing equipment, 200.2g of solid urea-process hydrazine hydrate byproduct saline alkali (the content of sodium chloride is 61.15 wt%, the content of sodium carbonate is 20.37 wt%, the content of hydrazine hydrate is 5.31 wt%, and the balance is impurities) is washed by a 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 sodium chloride crude salt (the content of sodium chloride is 94.18 wt%, the content of sodium carbonate is 0.84 wt%, the content of hydrazine hydrate is 0.16 wt%, and the balance is impurities) and mother liquor I (the content of hydrazine hydrate is 4-6 wt%, the content of sodium chloride is 12-17 wt%, and the content of sodium carbonate is 10-14 wt%);
wherein the washing liquid is a mixture of a mother liquid I and a mother liquid II which are recycled, the mass of the mother liquid II is 600.1g, and the volume ratio of the salt and the alkali to the washing liquid is 20: 80; freezing the mother liquor I which is not used in washing by using a freezing system at 15 ℃ to crystallize, and centrifugally separating to obtain sodium carbonate decahydrate and mother liquor II; and inputting the unused mother liquor II into a 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 20:80, dropwise adding 2.0ml of hydrochloric acid with a concentration of 31 wt% into the slurry to adjust the pH to 7-8, performing centrifugal filtration to obtain refined sodium chloride (the sodium chloride content is 99.2 wt%, 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 (6)
1. A method for separating saline from an byproduct of hydrazine hydrate by a urea method is characterized by comprising the following steps:
(1) freezing the rough hydrazine hydrate solution produced by the urea method to crystallize and centrifugally separating to obtain sodium carbonate decahydrate and mother liquor II;
(2) washing solid-state urea-process hydrazine hydrate byproduct salt and alkali with a washing solution at the temperature of 30-50 ℃, and centrifugally filtering to obtain solid sodium chloride crude salt and a mother solution I; the washing liquid is a mixture of a mother liquid I and a mother liquid II which are recycled, the mass ratio of the salt and the alkali to the mother liquid II is 1: 1.7-3.5, and the salt and the alkali account for 15-30% of the total volume of the salt and the washing liquid;
(3) and (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 value to 7-8, and performing centrifugal filtration to obtain refined sodium chloride and mother liquor III.
2. The method for separating the saline alkali byproduct of hydrazine hydrate by urea process according to claim 1, further comprising: freezing the unused mother liquor I in washing to crystallize by using a freezing system and carrying out centrifugal separation to obtain sodium carbonate decahydrate and mother liquor II; inputting the unused mother liquor II in washing into a production system; and (4) adding the mother liquor III into the slurry obtained in the step (3) for recycling.
3. The method for separating the byproduct saline alkali of hydrazine hydrate by urea process according to claim 1, wherein the crude hydrazine hydrate solution and the mother liquor I both contain 12-17 wt% of sodium chloride and 10-14 wt% of sodium carbonate, and the mother liquor II contains 15-20 wt% of sodium chloride and 3-7 wt% of sodium carbonate.
4. The method for separating the saline alkali byproduct of hydrazine hydrate by urea process according to claim 1, wherein the freezing temperature in the step (1) is-10 ℃ to 15 ℃.
5. The method for separating the byproduct saline alkali of the urea-process hydrazine hydrate according to claim 1, wherein 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.
6. The method for separating the byproduct saline alkali of the urea-process hydrazine hydrate 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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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114853638A (en) * | 2022-05-13 | 2022-08-05 | 宁夏日盛高新产业股份有限公司 | Production method and system of biurea |
| CN115350500A (en) * | 2022-08-23 | 2022-11-18 | 宁夏日盛高新产业股份有限公司 | Byproduct comprehensive utilization system in foaming agent production |
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| CN1745913A (en) * | 2005-10-13 | 2006-03-15 | 宜宾天原股份有限公司 | Recovering treatment of hydrated hydrazine by-product saline-alkali by urea method |
| CN1796280A (en) * | 2004-12-29 | 2006-07-05 | 陈大元 | Separation of salt and alkali from waste salt and alkali residue in production of hydrazine hydrate and technique of cyclic utilization |
| 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 |
| CN107055581A (en) * | 2017-03-31 | 2017-08-18 | 衡阳市锦轩化工有限公司 | A kind of method of coproduction hexafluoro sodium aluminate and biruea |
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2020
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| CN1796280A (en) * | 2004-12-29 | 2006-07-05 | 陈大元 | Separation of salt and alkali from waste salt and alkali residue in production of hydrazine hydrate and technique of cyclic utilization |
| CN1745913A (en) * | 2005-10-13 | 2006-03-15 | 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 |
| CN107055581A (en) * | 2017-03-31 | 2017-08-18 | 衡阳市锦轩化工有限公司 | A kind of method of coproduction hexafluoro sodium aluminate and biruea |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114853638A (en) * | 2022-05-13 | 2022-08-05 | 宁夏日盛高新产业股份有限公司 | Production method and system of biurea |
| CN115350500A (en) * | 2022-08-23 | 2022-11-18 | 宁夏日盛高新产业股份有限公司 | Byproduct comprehensive utilization system in foaming agent production |
| CN115350500B (en) * | 2022-08-23 | 2023-10-13 | 宁夏日盛高新产业股份有限公司 | Byproduct comprehensive utilization system in foaming agent production |
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