CN1095390C

CN1095390C - Method and apparatus for eliminating acid mist and acid liquor created by ADC foaming agent condensation process

Info

Publication number: CN1095390C
Application number: CN96107542A
Authority: CN
Inventors: 郑守樽
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-05-30
Filing date: 1996-05-30
Publication date: 2002-12-04
Anticipated expiration: 2016-05-30
Also published as: CN1150059A

Abstract

The present invention discloses a novel method for eliminating the pollution caused by acid mist and washing acid water produced in the condensation procedure of an ADC foaming agent and a device thereof. The present invention has the technical scheme that an inner circulation absorbing method is adopted, namely that hydrazine materials and reaction materials are used as an absorbing agent to make hydrogen chloride absorbed by the reaction materials and recycled for production before the hydrogen chloride forms the acid mist, and the material liquid is kept in pH4-9 during the neutralizing process and is separated from the condensation reaction. A production device needed by the method is composed of a neutralizing pool for hydrazine urea dissolving media, a condensing pot, an immersible pump, a stirrer, a hydrazine metering pot, a sulphuric acid pot, a draught fan, etc. The present invention has the advantages of no need of acid mist processing equipment, water and electricity saving, low acid consumption, obvious economic and social benefits, and obvious environment protection effect.

Description

Method and device for eliminating acid mist and acid water generated in ADC foaming agent condensation process

The present invention relates to a new method and its equipment for eliminating the pollution of acid mist produced in the condensation process of ADC foaming Agent (ADC) production and its washing acid water.

The basic raw materials for producing the ADC foaming agent are liquid alkali, chlorine, urea and sulfuric acid, and the production process is briefly described as follows:

1. preparing sodium hypochlorite: ………………(1)

2. preparation of hydrazine hydrate ……(2)

As can be seen from the reaction formula, the hydrazine hydrate solution (hereinafter referred to as crude hydrazine) prepared as described above contains a large amount of soluble substances such as sodium chloride, sodium carbonate and residual alkali, and the crude hydrazine can be used for preparing biurea through the condensation process after evaporation, distillation, purification and concentration according to the ADC production process at home and abroad in the past.

3. Condensation preparation of biurea ……(3)

4. Preparation of ADC foaming agent by chlorine oxidation of biurea after washing ………(4)

Because the source of the pure hydrazine hydrate which is the main raw material in ADC production is difficult, the generally prepared crude hydrazine hydrate contains only 3-4% of hydrazine and more impurities, wherein the content of the hydrazine is about 20% of sodium chloride; 4-12% of sodium carbonate, 1-5% of sodium hydroxide and a small amount of urea, ammonia and the like, and hydrazine hydrate has a boiling point higher than that of water, so that the hydrazine is very difficult to evaporate and purify, numerous and complicated equipment is required, the energy consumption is high, and the requirements of ADC production development cannot be met. The inventor has proposed a new process for producing ADC by replacing concentrated hydrazine with crude hydrazine (hereinafter referred to as hydrazine) in a first chemical factory in Fuzhou in 1970, and practice proves that the new process can meet the production requirements of ADC in terms of yield and product quality, saves distillation and purification procedures, greatly simplifies equipment, greatly reduces energy consumption and production cost, is rapidly adopted by the same nationwide, but brings a new problem of environmental pollution caused by acid mist and washing acid water when the process is popularized, and is seen in three wastes and comprehensive utilization of ADC foaming agent in No. 4 of chlor-alkali 1995, the current situation of ADC foaming agent in No. 5 of chlor-alkali industry 1991 and the development prospect in 2000.

This is because<3>The condensation reaction of formula (II) can only be carried out under slightly alkaline to slightly acidic conditions, otherwise urea is largely hydrolyzed and lost. If the reaction is slightly acidic, the reaction speed is high and the yield is high, so that the hydrazine urea solution is firstly added into concentrated sulfuric acid in a condensation pot to neutralize hydrazine, sodium hydroxide and sodium carbonate in the hydrazine and sodium hydroxide to be slightly acidic, then the temperature is raised to boiling, and the reaction is carried out at the boiling temperature<3>By the reaction of formula (I), with the addition of acid to neutralize the urea hydrolysis productThe pH of the raw ammonia can be maintained at 4-6. In particular, in the acid-adding neutralization stage, the neutralization heat and dilution heat energy released when the local concentrated acid zone formed during neutralization and the alkali in the solution are subjected to neutralization reaction promote the strong double decomposition reaction of the concentrated acid and the sodium chloride in the solution, and a large amount of hydrogen chloride is generated to escape from the reaction<5> ………………(5)

A large amount of hydrogen chloride reacts with a small amount of ammonia escaped from hydrazine to generate white acid smog which is shown in a reaction formula<6> …………………(6)

Acid rain is generated in foggy days and rainy days to cause serious pollution to the environment, and various factories take vigorous research and treatment measures on the acid fog, but most of the measures are limited to the upper and lower time of treatment, the acid fog is washed by a washing tower and then is discharged to the high altitude by an induced draft fan, the washing water is discharged in acid water, the washing tower is only enlarged, the washing water consumption is increased along with the continuous increase of the yield of various factories, the height of a discharge chimney is continuously increased, generally more than 30 meters and as high as 50 meters, the environmental conditions are locally improved by the measures, but the acid fog and the acid water discharged by the measures cannot reach the standard.

The inventor aims at solving the problem of pollution of acid mist and washing acid water generated in the ADC production condensation process, and proposes various schemes through long-term observation, research and tracking of reasons and conditions of pollution source generation, for example, the inventor provides a method of dripping acid from liquid in the 1979 national same industry alternating current of Suzhou city to reduce the generation and discharge of acid mist and reduce the acidity of washing water, and finally determines an optimal method, namely an 'internal circulation absorption method' through comparison, screening and experimental improvement. In order to improve the utilization rate of equipment of the condensation kettle, the prior hydrazine urea dissolving tank is changed into a hydrazine urea dissolving neutralization tank, so that the neutralization time of the condensation kettle is reduced, the condition of easy overflow during neutralization is improved, and an acid adding pipe and a hydrazine adding pipe are respectively and deeply submerged for improving the absorption effect.

Compared with the equipment improvement in the new and old processes, the method comprises the following steps: 1. the hydrazine-urea dissolving pool is equipped with draught fan, stirrer, submerged pump and hydrazine-adding pipe, and in the new process a sulfuric acid tank is added, and the acid-adding pipe and hydrazine-adding pipe are respectively extended into the liquid. 2. The original hydrazine urea dissolving tank is changed into a hydrazine urea dissolving and neutralizing tank, and the original neutralization reaction is carried out in the condensation pot instead of the hydrazine urea dissolving and neutralizing tank, so that the equipment utilization rate of the condensation pot is improved. 3. The original condensation pot is equipped with conduit, gas collecting main pipe and washing tower, water supply deep well pump, draught fan, high altitude chimney pipe and pipe frame, it plays the role of neutralization and condensation, the draught fan is to draw out the acid mist and exhaust after washing. The new process has no acid mist escaping, only water vapor, carbon dioxide and the like can be directly emptied from the guide pipe, and the whole set of equipment for treating the acid mist after the guide pipe can be saved.

The advantages and benefits of the new process are as follows:

1. the new process is characterized in that the reaction material can be used as the acid mist absorbent and can be recycled after absorption, the acid mist is eliminated in the production process, the whole set of equipment for treating the acid mist can be eliminated, acid water is not discharged, the acid mist is not emitted, the maximum benefit is an environmental protection benefit, the pollution of the acid mist and a large amount of acid water is eliminated fundamentally, and good economic benefit is obtained.

2. The new process can save 500 tons of water for producing each ton of ADC (see the fifth phase 'ADC foaming agent production energy consumption discussion' of 1994 of chlor-alkali of China) and the pollution discharge cost and daily treatment cost of 500 tons of sewage.

3. The construction cost of acid mist treatment can be saved by newly building a factory, and the construction cost comprises a plurality of capital construction costs such as a gas collecting main pipeline, a conveying pipeline, a draught fan, a high-altitude discharge chimney, a pipe frame, a water source (a deep well pump) and the like, and the small factory can save more than 20 ten thousand yuan per 1000 tons per year.

4. The materials used in the new process are returned to the system for use after absorbing acid mist, so that 50kg of sulfuric acid can be saved in each ton of products, and the service life of the condensation kettle can be prolonged by more than one time because no acid mist escapes.

5. The new process has simple equipment, easy operation and convenient popularization.

And (6) measuring and observing the result.

Acid mist generated by neutralization and condensation in the prior art is washed and then is rolled in dense smoke, pH is measured by pH test paper (hereinafter referred to as test paper) before washing and is less than 1, gas after washing is still measuredto be acidic pH which is less than or equal to 1, the gas is only required to be discharged from high altitude, and a chimney is generally more than 30m and as high as 50 m. The measurement result of the pipeline condensed water contains 0.5-2% of hydrochloric acid, and the pH value of a large amount of washing water is about 1-2.

The novel process is a process for separating neutralization and condensation, when the pH value of feed liquid in the neutralization process is 4-9, the pH value of discharged gas is 6-8 after being tested by test paper for many times, and the discharged gas can be directly discharged after meeting the discharge standard. And (3) when the pH value of the feed liquid is 4-6 and the temperature is 110 ℃, the discharged gas is mainly water vapor, and carbon dioxide and ammonia are subjected to condensation reaction, and the pH value is 6-9 and most of the discharged gas is 7-8 by test paper. Can meet the emission standard and can be directly discharged outdoors to keep the air of the operation environment fresh. When the condensation exhaust condensate water is measured, the pH value is 8-9.

The invention is further illustrated below with reference to the figures and examples.

In the attached figure 1, (1) a sulfuric acid tank, (2) a hydrazine metering tank, (3) a hydrazine-urea dissolving tank, (4) a stirrer, (5) a submerged pump, (6) a condensation kettle and (7) an induced draft fan.

In the attached figure 2, (1) a sulfuric acid tank, (2) a hydrazine metering tank, (3) a hydrazine-urea dissolving and neutralizing tank, (4) a stirrer, (5) a submerged pump, (6) a condensation kettle, (7) a draught fan, (8) a tail gas washing tower and (9) a chimney.

As shown in figure 1, the device for eliminating acid mist and acid water generated in the ADC foamingagent condensation process comprises a hydrazine urea dissolving neutralization tank (3), a condensation pot (6), a submerged pump (5), a stirrer (4), a hydrazine metering tank (2), a sulfuric acid tank (1), an induced draft fan (7) and the like. The hydrazine urea dissolving and neutralizing tank (3) is provided with a stirrer (4), a feeding submerged pump (5), a submerged hydrazine feeding pipe and a submerged acid feeding pipe. The hydrazine metering tank (2) passes through a valve 1^#Is connected with a submerged hydrazine feeding pipe,the sulfuric acid tank (1) passes through a valve 2^#Connected with a submerged acid adding pipe, and a feeding submerged pump (5) passes through a valve (3)^#Is connected with a condensation pot (6), an inlet pipeline of a draught fan (7) is arranged above a hydrazine urea dissolving neutralization pond (3), a stirrer (4) and an acid adding pipe under liquid are arranged in the condensation pot (6), and a sulfuric acid tank (1) passes through a valve 4^#And is connected with an acid adding pipe under liquid.

The working process is as follows: 1. hydrazine urea dissolving and neutralizing operation steps:

firstly starting the draught fan (7) and the stirrer (4), and then opening the hydrazine adding valve 1^#And an acid addition valve 2^#To keep the pH of the feed liquid in the neutralization tank at 4-9, when 3 cubic meter of hydrazine is accurately added (5 cubic meters of condensation kettle), the hydrazine adding valve 1 is immediately closed^#Urea with hydrazine and urea ratio regulated by respective process operation is added, sulfuric acid is continuously added to regulate pH to 4, and acid valve 2 is closed^#After the urea is completely dissolved, closing the stirrer (4) and the induced draft fan (7), opening a feed valve of the condensation pot (6), opening the submerged pump (5) to pump the hydrazine urea solution to thecondensation pot (6) until the residual solution is 500-600mm quantitatively, and stopping the submerged pump (5) to close the feed valve (3)^#And completing the dissolving and neutralization of a batch of hydrazine urea.

2. Compared with the prior art, the condensation operation steps save all the operations of an acid mist treatment system, feed liquid in a hydrazine urea dissolving neutralization tank (3) is pumped into a condensation pot (6), steam is introduced, heating and boiling are carried out, and an acid valve 4 is opened when the acidity is reduced^#When the pH is kept at 4-6, condensation is carried out for 4-5 hours, and then the material is taken out for liquefaction, and when 2ml of feed liquid is less than 1.5ml of iodine consumption liquid (C is 0.5 mol/L). Namely, the condensation is finished and the material is discharged.

Claims

1. A method for eliminating acid mist and acid water generated in an ADC foaming agent condensation process is characterized in that a hydrazine urea solution PH is kept between 4 and 9 in a neutralization process, raw materials of hydrazine and a hydrazine urea solution are used as acid mist absorbents, hydrazine urea dissolution and neutralization reaction are carried out in the same hydrazine urea dissolution and neutralization tank (3), hydrazine hydrate with the volume of 60% of that of a condensation pot and urea with the hydrazine and urea proportion specified according to respective process operations are added into the hydrazine urea dissolution and neutralization tank (3) in batches according to the volume of the condensation pot (6), finally acid is added to adjust the PH to 4, after the urea is completely dissolved, the feed liquid is pumped into the condensation pot (6) by a liquid, steam is introduced for heating, and the condensation reaction is completed underthe conditions of boiling and pH adjustment by acid addition under the condition of 4 to 6.

2. The utility model provides an eliminate device of acid mist and acid water that ADC foamer condensation process produced, includes hydrazine urea solution neutralization pond (3) and condensation pot (6), its characterized in that: be furnished with agitator (4) in hydrazine urea dissolves neutralization pond (3), pay-off submerged pump (5), submerged hydrazine pipe and submerged acidification pipe, hydrazine metering tank (2) link to each other with submerged hydrazine pipe through valve 1#, sulfuric acid tank (1) links to each other with submerged acidification pipe through valve 2#, pay-off submerged pump (5) link to each other with condensation pot (6) through valve 3#, draught fan (7) entry pipeline installs in the urea dissolves the top in neutralization pond (3), condensation pot (6) are furnished with agitator (4) and submerged acidification pipe, sulfuric acid tank (1) link to each other through valve 4# and submerged acidification pipe.