CN1686857A

CN1686857A - Method for treating wastewater of rectification for producing hydrazine hydrate by carbamide method

Info

Publication number: CN1686857A
Application number: CN 200510020772
Authority: CN
Inventors: 罗云; 郑春宁; 刘灵伟; 李强; 胡顺辉; 袁雄; 李福群; 万立
Original assignee: Yibin Tianyuan Group Co Ltd
Current assignee: Yibin Tianyuan Group Co Ltd
Priority date: 2005-04-22
Filing date: 2005-04-22
Publication date: 2005-10-26
Anticipated expiration: 2025-04-22
Also published as: CN1331772C

Abstract

The present invention discloses a treatment method of waste water produced in the rectification process for producing hydrazine hydrate by using urea, sodium hypochlorite and sodium hydroxide oxiation method. Its main technical scheme includes the following procedures: in the waste water discharged from rectification process adding at least equivalent oxidation substance matched with hydrazine hydrate and ammonia existed in the waste water to make the hydrazine hydrate and ammonia react with oxidative substance and convert into nitrogen gas and water, and the nitrogen gas can be directly discharged into atmosphere.

Description

Method for treating wastewater from rectification of hydrazine hydrate by urea method

Technical Field

The invention relates to a method for treating byproducts generated in the process of producing hydrazine hydrate by using urea, sodium hypochlorite and sodium hydroxide through an oxidation method, in particular to a method for treating wastewater generated in a rectification process.

Background

Hydrazine hydrate, also known as: hydrazine hydrate, formula: n is a radical of₂H₄·H₂O, molecular weight: 50.07, belonging to fine chemical products. Hydrazine hydrate is used as a chemical intermediate, has wide potential application and application fields, and is mainly divided into three aspects: firstly, producing a plastic foaming agent; secondly, in the steam cycle of the power industry, the device is used for preventing pipelines from rusting and aging in advance, so that the safety and reliability of a power station are greatly improved; hydrazine hydrate is also an important raw material for pharmaceuticals and agricultural chemicals. Various production methods of hydrazine hydrate, such as Rashig method, Bell (Bayer) method or hydrogen peroxide method, Chinese patent with patent number 02113375.1 discloses a method for preparing concentrated hydrazine hydrate solution, which is applied by the applicant, and adopts urea, sodium hypochlorite and sodium hydroxide oxidation method (urea method for short), and the technological process mainly comprises the following steps: sodium hypochlorite solution is prepared by taking caustic soda, water and chlorine as raw materials, the sodium hypochlorite solution reacts with urea solution to generate hydrazine hydrate crude solution, wherein the hydrazine hydrate crude solution contains sodium carbonate, sodium chloride, sodium hydroxide and water, the hydrazine hydrate crude solution is cooled and crystallized, sodium carbonate decahydrate is recovered, the solution is evaporated, evaporated water and hydrazine hydrate steam are rectified again to obtain high-content hydrazine hydrate, and meanwhile, rectification waste water is discharged. It is mainly chemically reactedThe equation should be:

wherein, the chemical composition of the discharged rectification wastewater is as follows:

NH₃：3--4.5g/l N₂H₄·H₂O：0.05-0.1g/l

it can be seen that such a production method has the following disadvantages: the rectifying waste water containing hydrazine hydrate and ammonia discharged in the rectifying process is directly discharged, and the pollution to the environment is very serious because the ammonia nitrogen index of the waste water exceeds 300 times (the ammonia nitrogen index discharged by the waste water reaches the standard and is 15 mg/l). Therefore, how to solve the pollution of the rectification wastewater to the environment is a technical problem to be solved urgently in the current hydrazine hydrate production process.

Disclosure of Invention

The invention firstly aims to solve the problems and provide a method for treating the rectification wastewater generated in the hydrazine hydrate production by a urea method, wherein the ammonia nitrogen index of the wastewater treated by the method meets the national environmental protection discharge requirement; the invention also aims to recycle the solution after the rectification wastewater treatment.

The purpose of the invention is realized as follows:

adding oxidizing substances which are at least matched with the hydrazine hydrate and ammonia existing in the wastewater in equivalent weight into the wastewater discharged in the rectification process of producing the hydrazine hydrate by adopting a urea method, so that the hydrazine hydrate and the ammonia react with the oxidizing substances to be converted into nitrogen and water;

wherein, the oxidizing substance is any one of hydrogen peroxide, chlorine or sodium hypochlorite, and the most preferable scheme is hydrogen peroxide.

When the wastewater is treated by hydrogen peroxide, the following reactions occur:

when the above wastewater is treated with chlorine gas, the following reaction occurs:

then adding sodium hydroxide into the solution to neutralize hydrogen chloride to obtain a sodium chloride solution, and returning the sodium chloride solution to the hydrazine hydrate synthesis process for recycling.

When sodium hypochlorite is used to treat the wastewater, the following reactions occur:

then the sodium chloride solution is returned to the hydrazine hydrate synthesis process for recycling.

Compared with the prior art, the invention has the following advantages:

according to the invention, as the oxidizing substances are adopted to react with hydrazine hydrate and hydrogen in the wastewater discharged in the rectification process of producing hydrazine hydrate by a urea method, the oxidizing substances and the hydrazine hydrate and the hydrogen are converted into nitrogen and water, the nitrogen can be directly discharged into the atmosphere, the ammonia nitrogen index of the treated discharged water is greatly reduced and reaches less than 10mg/l, which is far lower than the related national standard, the discharged water can be directly discharged, and the environment is not polluted; meanwhile, when chlorine or sodium hypochlorite is used as an oxidant, the solution obtained by the reaction can be recycled, so that resources are fully utilized, and waste is avoided.

Drawings

FIG. 1 is a block diagram of a process flow of the present invention.

Detailed Description

Firstly, preparing hydrazine hydrate according to conventional steps, namely firstly, putting 30 percent of caustic soda into a dilute alkali preparation tank, and continuously and circularly mixing a certain amount of industrial water (the treated rectification wastewater replaces the industrial water) by using a pump until the content is 290g/l, wherein the industrial water is used for standby application; then putting the industrial water into a urea solution preparation tank, adding solid urea and a catalyst under stirring, and standing for later use when the dissolution content of the solid urea is 295-300 g/l; then continuously feeding the dilute alkali into a sodium hypochlorite reactor according to a certain flow, introducing chlorine, cooling by using 0-5 ℃ frozen saline water, and controlling the reaction temperature to be below 15 ℃ to obtain a sodium hypochlorite solution containing 8-12% of available chlorine. Chemical reaction equation:

then mixing sodium hypochlorite and urea solution according to a certain proportion by using a pump, heating the mixture to 106-108 ℃ by using steam, and reacting to generate a crude solution containing hydrazine hydrate, wherein the chemical reaction equation is as follows:

then the crude solution of hydrazine hydrate is cooled to less than 35 deg.C by pump and then sent into crystallization kettle, and cooled by liquid ammonia or frozen salt water at less than-5 deg.C, and after the temperature is reduced to-2 deg.C, 70% sodium carbonate in the crude hydrazine hydrate solution is separated by centrifugation. Feeding the crude solution of hydrazine hydrate after removing sodium carbonate into a forced circulation evaporator for evaporation, feeding the evaporated water and hydrazine hydrate steam into a rectifying tower for continuous concentration to 40%, directly discharging distilled water containing 0.05-0.1g/l of hydrazine hydrate and 3-4.5g/l of ammonia, finally feeding the 40% hydrazine hydrate solution into the rectifying tower again, heating by steam for rectification, concentrating to 80%, and evaporating to remove impurities in the hydrazine hydrate solution to obtain 80% hydrazine hydrate.

Example 1: and (3) treating the rectification wastewater by using hydrogen peroxide as an oxidant.

Pumping rectified waste water containing ammonia about 4g/l and hydrazine hydrate about 0.1g/l to a reaction with stirringStirring in a reactor, and cooling the rectification wastewater from about 60 ℃ to normal temperature by using frozen brine with the temperature of less than 0 ℃ according to NH contained in the rectification wastewater₃And N₂H₄·H₂And (4) pumping equivalent hydrogen peroxide into the rectification wastewater by using a pump, and discharging the wastewater after the ammonia nitrogen content is less than 10 mg/l.

Wherein the following reactions take place in the solution:

example 2: and (3) treating the rectification wastewater by using chlorine as an oxidant.

Pumping the rectified waste water containing ammonia about 4g/l and hydrazine hydrate about 0.1g/l into a reaction kettle with a stirrer, starting the stirrer, cooling the rectified waste water from about 60 ℃ to normal temperature by using frozen saline water at the temperature of less than 0 ℃, and according to NH contained in the rectified waste water₃And N₂H₄·H₂And (3) introducing chlorine gas with matched equivalent quantity into the reactor to ensure that the content of ammonia nitrogen in the rectification wastewater is less than 10mg/l, and reacting in the reactor as follows:

then adding 30% NaOH to adjust the PH value to 7-8, sending the treated rectification wastewaterto a hydrazine hydrate production system by using a pump for preparing urea solution and dilute alkali solution, referring to figure 1, namely adding solid urea and catalyst magnesium sulfate heptahydrate into the treated rectification wastewater, and obtaining the urea solution after the solid urea is dissolved and uniformly stirred; or adding the treated rectification wastewater into 42% liquid alkali or 72-98% solid alkali, introducing chlorine gas to prepare a sodium hypochlorite solution after preparing the alkali into a dilute alkali solution of 300g/l, and then mixing and reacting the alkali-containing sodium hypochlorite solution and a urea solution under the condition of heating to produce a crude hydrazine hydrate solution, thereby realizing the recycling in the hydrazine hydrate synthesis process.

Example 3: sodium hypochlorite is used as an oxidant to treat the rectification wastewater.

Pumping the rectified waste water containing ammonia about 4g/l and hydrazine hydrate about 0.1g/l into a reaction kettle with a stirrer, starting the stirrer, cooling the rectified waste water from about 60 ℃ to normal temperature by using frozen saline water at the temperature of less than 0 ℃, and according to NH contained in the rectified waste water₃And N₂H₄·H₂The amount of O, to which was added the equivalent of sodium hypochlorite, the following reaction occurred:

after the content of ammonia nitrogen in the wastewater after the complete rectification by reaction is less than 10mg/l, the treated wastewater after the complete rectification is sent to a hydrazine hydrate production system by a pump according to the method inthe embodiment 2 for preparing urea solution and dilute alkali solution for recycling in the hydrazine hydrate synthesis process.

Claims

1. A process for treating the rectifying waste water generated by rectifying hydrazine hydrate by urea method features that the oxidizing substance whose equivalent weight is at least matched with that of hydrazine hydrate and ammonia existing in waste water is added to the waste water discharged from rectifying process for reacting hydrazine hydrate and ammonia with said oxidizing substance to convert them to nitrogen gas and water.

2. The method for treating wastewater from rectification of hydrazine hydrate by urea process as claimed in claim 1, wherein the oxidizing substance is any one of hydrogen peroxide, chlorine or sodium hypochlorite.

3. The method for treating wastewater from rectification of hydrazine hydrate by urea process as claimed in claim 2, wherein hydrogen peroxide in equivalent weight to hydrazine hydrate and ammonia existing in wastewater is added to wastewater discharged from rectification process under normal temperature condition, so that hydrazine hydrate and ammonia in wastewater react with hydrogen peroxide to convert into nitrogen and water until ammonia nitrogen content in water is less than 10 mg/l.

4. The method for treating wastewater from rectification of hydrazine hydrate by urea process as claimed in claim 2, wherein chlorine gas in equivalent weight to hydrazine hydrate and ammonia present in wastewater is added to wastewater discharged from rectification process under normal temperature condition, hydrazine hydrate and ammonia in wastewater are reacted with chlorine gas to convert into nitrogen gas, water and hydrogen chloride, sodium hydroxide is added to the solution to neutralize hydrogen chloride to obtain sodium chloride solution until ammonia nitrogen content in the solution is less than 10mg/l, and the sodium chloride solution is returned to hydrazine hydrate synthesis process for recycling until pH value of the sodium chloride solution is 7-8.

5. The method for treating wastewater from rectification of hydrazine hydrate by urea process as claimed in claim 2, wherein sodium hypochlorite equivalent to hydrazine hydrate and ammonia existing in the wastewater is added to the wastewater discharged from rectification at normal temperature, so that hydrazine hydrate and ammonia in the wastewater react with sodium hypochlorite to convert into nitrogen gas and water, sodium chloride, until the ammonia nitrogen content in the solution is less than 10mg/l, and then the sodium chloride solution is returned to the hydrazine hydrate synthesis process for recycling.