CN104495953A - Process for treating industrial waste hydrochloric acid in recycling way through salt fractionation method - Google Patents

Abstract

The present invention relates to a kind of salting-out method resource treatment process of industrial waste hydrochloric acid. The treatment of industrial waste hydrochloric acid is carried out in a treatment system. The steps of the treatment process are: (1) reaction of iron powder; (2) mixing of ferrous chloride; (3) chlorination Ferrous neutralization and crystallization (4) recycling of ferrous chloride crystals or solutions; (5) calcium chloride neutralization and crystallization (6) condensation and absorption of precipitated gases. The present invention utilizes the same ion effect, adding ferrous chloride crystals or solutions to industrial waste hydrochloric acid, concentrating under negative pressure and heating conditions, the precipitated gas can be partially condensed into hydrochloric acid for reuse, and the remaining part is made of calcium oxide or hydrogen Calcium oxide absorption, the finished product is ferrous chloride, calcium chloride, hydrochloric acid, will not cause secondary pollution, small investment, low operating costs, is a new process to realize the resource utilization of industrial waste hydrochloric acid, has a wide range of application prospects .

Description

A kind of salting-out method resource treatment process of industrial waste hydrochloric acid

technical field

The invention belongs to the field of environmental protection, and relates to the treatment of industrial waste hydrochloric acid, in particular to a process for recycling industrial waste hydrochloric acid by a salting-out method.

Background technique

As a commonly used chemical product, hydrochloric acid is widely used in carbon steel cold rolling, galvanizing and other processes. As a pickling medium, hydrochloric acid reacts with iron oxide on the surface of steel to generate ferrous chloride and ferric chloride and dissolve them in the acid solution. In the hydrochloric acid waste liquid that this reaction produces, contain the hydrochloric acid of 5% and the ferrous chloride of 10-12%, if directly discharge this part hydrochloric acid waste liquid, will cause serious environmental pollution to discharge area. In addition, the waste acid liquid contains ferrous chloride and hydrogen chloride, which can be considered as very good chemical raw materials. Therefore, the resource treatment and utilization of waste hydrochloric acid is an inevitable requirement for protecting the environment and realizing green development.

According to statistics, a push-pull pickling unit with an annual output of 450,000 tons of cold-rolled steel plates needs about 20,000 tons of hydrochloric acid per year, and the waste liquid containing hydrochloric acid is also nearly 20,000 tons. up to 51 million tons. Based on this calculation, the annual output of waste hydrochloric acid in the cold rolling industry alone has exceeded 2.2 million tons. It can be seen that the recycling of waste hydrochloric acid is not only related to environmental protection, but also has very important significance for the utilization of resources and the promotion of the development of circular economy.

There are many traditional methods for treating industrial waste hydrochloric acid, including thermal decomposition method, high temperature hydrolysis method, extraction method, membrane separation method, precipitation method and neutralization method. Thermal decomposition method and high temperature hydrolysis method can be divided into processes such as roasting method and fluidized bed method; the working principles of these two methods are the same, all are to react waste hydrochloric acid containing ferrous chloride with oxygen at high temperature, and It absorbs concentrated and volatilized hydrogen chloride, and its finished products are hydrochloric acid and iron red. The disadvantages are large investment, high operating costs, high technical difficulties, and difficult management and maintenance. The extraction method uses the extract composed of the organic phase for countercurrent extraction, but the method of recycling the extract phase still requires high investment and is inconvenient to operate, so it is not suitable. The membrane separation method uses membrane ions to selectively separate iron and acid. The disadvantage is that with the increase of the osmotic pressure of iron ions on both sides of the membrane, a large pressure energy input is required, and it has a great impact on the material and compressive performance of the membrane. High requirements are put forward, and the initial investment and operating costs are relatively high. Precipitation method is to utilize flocculant to flocculate ferrous chloride in waste hydrochloric acid. Although this method utilizes part of ferrous chloride in waste hydrochloric acid, there is still a small part of ferrous chloride in the remaining waste acid solution. This makes the purity level of the product generated by the subsequent waste acid treatment generally not high, which affects the performance of the product. The neutralization method uses alkali to react with waste hydrochloric acid. This is the oldest method for treating pickling waste liquid. However, because hydrogen chloride and ferrous chloride in waste acid liquid have not been utilized, and it is easy to cause secondary pollution, This method is basically no longer used.

The salting-out method involved in the application of the present invention refers to a method in which a large amount of inorganic salt is added to a solution to reduce the solubility of certain substances and precipitate out to separate them from other components. At present, the salting-out method is mainly used for the separation and purification of proteins. Inorganic salts commonly used for salting-out include sodium chloride, sodium sulfate, magnesium sulfate, ammonium sulfate, etc. The same kind of ion as the precipitated substance will also have the effect of separation.

By searching, there is no published patent document that adopts the salting-out method to process waste hydrochloric acid.

Contents of the invention

The object of the present invention is to overcome the deficiencies of the prior art, and provide a process for recycling industrial waste hydrochloric acid by salting out, which is environmentally friendly, low in investment and low in operating cost.

The present invention solves its technical problem and realizes by taking the following technical solutions:

A kind of salting-out method resource treatment process of industrial waste hydrochloric acid, the treatment of industrial waste hydrochloric acid is carried out in the treatment system, the steps of the treatment process are:

(1) Iron powder reaction: put industrial waste hydrochloric acid into the iron powder reactor, and under the absolute atmospheric pressure of 0.01MPa to 0.098MPa, add iron powder into the iron powder reactor, stir and react fully, so that part of the hydrogen chloride reacts to form ferrous chloride ;

(2) Mixing of ferrous chloride: Feed the ferrous chloride solution discharged from the iron powder reactor into the ferrous chloride mixer, and then add ferrous chloride crystals or solution, at an absolute atmospheric pressure of 0.01MPa to 0.098MPa, Under the condition of temperature from 50°C to 100°C, make the mass concentration of ferrous chloride solution greater than 30%; stir well, and neutralize with sodium hydroxide until the pH value is 6-7;

(3) ferrous chloride crystallization: the discharge of ferrous chloride mixer is evaporated to crystallization, generates ferrous chloride crystal, also contains part ferrous chloride solution simultaneously, saturated solution is put into ferrous chloride crystallization The tank undergoes repeated heating crystallization and cooling crystallization, and the obtained crystallization and saturated solution are transferred to the ferrous chloride finished product tank, and the precipitated water vapor leads to the iron powder reactor and the heating sleeve in the ferrous chloride mixer;

⑷Recycling of ferrous chloride crystals or solutions: add part of the ferrous chloride crystals generated above, or a solution containing ferrous chloride concentration greater than or equal to 40%, into the ferrous chloride mixer again to cause chlorine Crystallization of the solution in the ferrous chloride mixer or increase the saturation of chloride ions in the solution;

(5) Calcium chloride neutralization and crystallization: the calcium chloride generated after the reaction of the spray tower and the incompletely reacted calcium oxide or calcium hydroxide are passed into the neutralization tank, and neutralized with the hydrochloric acid produced by the washing tower to generate chlorine Calcium solution, the neutralized calcium chloride solution is evaporated to crystallization, and the water vapor separated out in the crystallization process leads to the heating sleeve in the iron powder reactor and the ferrous chloride mixer;

(6) Condensation and absorption of precipitated gas: The precipitated gas in the above steps (1) and (2) is first passed to the scrubber, absorbed by water or industrial waste acid to generate hydrochloric acid; the remaining unabsorbed gas is passed to the calcium oxide or calcium hydroxide absorption tower, Calcium oxide or calcium hydroxide generates calcium chloride after absorbing gas, and the pH value is adjusted to 7 to 8. After heating and crystallization, it becomes calcium chloride crystal or saturated solution.

Moreover, the concentration of ferrous chloride contained in the ferrous chloride solution is greater than or equal to 40%.

Moreover, the treatment system includes an iron powder reactor, a ferrous chloride mixer of waste hydrochloric acid, a ferrous chloride crystallization tank, a ferrous chloride finished product tank, a washing tower, a hydrochloric acid finished product tank, a spray tower, and a neutralization tank , calcium chloride crystallization tank, calcium chloride collection tank and exhaust machine, the front end of the iron powder reactor is connected to the input nozzle of industrial waste hydrochloric acid, and the rear end is connected to the ferrous chloride mixer of waste hydrochloric acid through the pump and valve , the ferrous chloride mixer is connected to the ferrous chloride crystallization tank through a pump and a valve, and the ferrous chloride crystallization tank is connected to the ferrous chloride mixer and the ferrous chloride finished product tank through a pump and a valve respectively; the iron powder reactor, The gas valve generated by the ferrous chloride mixer due to heating and negative pressure is connected to the scrubber, and the discharge valve at the bottom of the scrubber is connected to the hydrochloric acid product tank, and the valve of the hydrochloric acid product tank is connected to the neutralization tank; the gas valve on the top of the scrubber is connected to Calcium hydroxide spray tower, the top outlet of the calcium hydroxide spray tower is discharged through the exhaust machine, the bottom outlet is connected to the neutralization tank, the neutralization tank is connected to the calcium chloride crystallization tank, and the calcium chloride crystallization tank is connected to the calcium chloride collection Can.

And, the discharged material of described ferrous chloride crystallization tank is divided into two lines, and one line is that the ferrous chloride finished product of discharging is directly collected in the ferrous chloride finished product tank, and the other line is connected with chlorine by pump and valve. Connect the ferrous chloride mixer.

And, the high-temperature steam produced in the calcium chloride crystallization tank and the ferrous chloride crystallization tank enters the iron powder reactor and the waste ferrous chloride hydrochloride mixer respectively through pipelines to heat the iron powder reactor and the ferrous chloride crystallization tank. The material in the waste ferrous chloride hydrochloride mixer.

And, described iron powder reactor and ferrous chloride mixer all are equipped with the iron powder inlet of band sealing device, also are equipped with the agitator of belt seal simultaneously, the following of iron powder reactor and ferrous chloride mixer There are sewage outlets with valves.

Advantage and positive effect of the present invention are:

1. The present invention utilizes the same ion effect, the solubility of hydrogen chloride decreases with the increase of temperature, and the solubility of ferrous chloride decreases with the increase of temperature. Ferrous chloride crystals or solutions are added to industrial waste hydrochloric acid. Concentrated under certain conditions, the precipitated gas can be partially condensed into hydrochloric acid for reuse, and the remaining part is absorbed by calcium oxide or calcium hydroxide. The finished product is ferrous chloride, calcium chloride, and hydrochloric acid, which will not cause secondary pollution. The cost is low, and it is a new process to realize the resource utilization of industrial waste hydrochloric acid, which has broad application prospects.

2, the present invention adopts adding ferrous chloride crystal or solution in industrial waste hydrochloric acid, has improved the chloride ion concentration of solution, has reduced the solubility of wherein hydrogen chloride, makes it from unsaturated to supersaturated, and then becomes hydrogen chloride gas to separate out, And it is absorbed by calcium oxide or calcium hydroxide, which can not only increase the concentration of recovered hydrochloric acid, so that the produced hydrochloric acid can enter the production field again, but also reduce the amount of absorbent calcium oxide or calcium hydroxide, and reduce the cost of waste acid treatment.

3. The present invention first uses iron powder to reduce the concentration of waste acid, and then less calcium hydroxide material can be used later, and the solubility of hydrogen chloride is reduced by salting out and negative pressure, so that hydrogen chloride is easily precipitated; using ferrous chloride crystallization tank, calcium chloride The secondary steam generated by the crystallization tank heats the reactor and mixer, which realizes energy saving, no waste is discharged in the process, and all products can be used as raw materials, which realizes environmental protection.

Description of drawings

Fig. 1 is a schematic diagram of the system structure of the present invention;

Fig. 2 is the variation graph of hydrogen chloride solubility of the present invention at 1atm with temperature;

Fig. 3 is the variation graph of ferrous chloride solubility of the present invention with temperature at 1 atm.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings and through specific embodiments. The following embodiments are only descriptive, not restrictive, and cannot limit the protection scope of the present invention.

The process for treating industrial waste hydrochloric acid involved in the present invention adopts a corresponding treatment system to process waste hydrochloric acid. In order to describe the process of the present invention more clearly, the applicant first explains the structure of the processing system:

This system includes iron powder reactor, waste hydrochloric acid ferrous chloride mixer, ferrous chloride crystallization tank, ferrous chloride finished product tank, washing tower, hydrochloric acid finished product tank, spray tower, neutralization tank, calcium chloride Crystallization tank, calcium chloride collection tank and exhaust machine, the front end of the iron powder reactor is connected to the input nozzle of industrial waste hydrochloric acid, and the rear end is connected to the ferrous chloride mixer of waste hydrochloric acid through pumps and valves, and the industrial waste Hydrochloric acid first enters the iron powder reactor, which can consume part of hydrogen chloride to reduce the amount of calcium hydroxide later; the material from the ferrous chloride mixer enters the ferrous chloride crystallization tank, and the material outlet of the ferrous chloride crystallization tank is divided into two One line is that the finished product of ferrous chloride is directly collected in the finished product tank of ferrous chloride, and the other line is connected to the ferrous chloride mixer through a pump and a valve, and its purpose is to increase the amount of chlorine in the mixer. Ion concentration, reducing the solubility of hydrogen chloride in the mixer.

The gas valve generated by the iron powder reactor and ferrous chloride mixer due to heating and negative pressure is connected to the scrubber, and the discharge valve at the bottom of the scrubber is connected to the hydrochloric acid product tank, and the valve of the hydrochloric acid product tank is connected to the neutralization tank; the scrubber The gas valve on the top of the gas valve is connected to the calcium hydroxide spray tower. The gas from the top of the calcium hydroxide spray tower is discharged through the exhaust machine, and the bottom discharge is connected to the neutralization tank. The neutralization tank is connected to the calcium chloride crystallization tank, and the calcium chloride crystallization tank The tank communicates with the calcium chloride collection tank. The principle of this reaction is: the washing tower is washed with water, and the generated hydrochloric acid enters the finished hydrochloric acid tank, and part of the hydrochloric acid in the finished hydrochloric acid tank can be used as hydrochloric acid, and a part is used for neutralization in the neutralization tank. The unwashed gas at the top of the scrubber enters the calcium hydroxide spray tower, where hydrogen chloride reacts with calcium hydroxide to form calcium chloride and then enters the neutralization tank. Since this part of calcium hydroxide cannot be fully reacted, it is neutralized with part of the generated hydrochloric acid in the neutralization tank to generate calcium chloride, and the solution of calcium chloride enters the calcium chloride crystallization tank for crystallization, and the crystallized product is the finished product of calcium chloride and enters the chlorine Calcium collection tank.

The high-temperature water vapor generated during the crystallization process in the ferrous chloride crystallization tank and calcium chloride crystallization tank enters the iron powder reactor and waste ferrous chloride hydrochloride mixer respectively through the pipeline to heat the iron powder reactor and For the material in the waste ferrous chloride hydrochloride mixer, the ferrous chloride crystallization tank has a neutralizing liquid inlet pipe.

The iron powder reactor and the ferrous chloride mixer are equipped with an iron powder inlet with a sealing device, and a sealed stirrer is also installed, and the iron powder reactor and the ferrous chloride mixer are all equipped with Sewage outlet with valve.

A kind of salting-out method resource treatment process of industrial waste hydrochloric acid, its steps are:

⑴ Iron powder reaction

Pass industrial waste hydrochloric acid into the iron powder reactor, and under the absolute atmospheric pressure of 0.01MPa to 0.098MPa, add iron powder in the iron powder reactor, stir and react fully, and produce ferrous chloride solution; the mass concentration of the subchloride solution is greater than 30%, the precipitated gas leads to calcium oxide or calcium hydroxide absorption tower.

(2) Mixing of ferrous chloride:

Pass the ferrous chloride solution discharged from the iron powder reactor into the ferrous chloride mixer, then add ferrous chloride crystals or solution, under the conditions of absolute atmospheric pressure 0.01MPa to 0.098MPa, temperature 50°C to 100°C Evaporate to crystallization to generate ferrous chloride crystals, neutralize with sodium hydroxide to a pH value of 6-7;

(3) Ferrous chloride neutralization crystallization: the discharge of ferrous chloride mixer is evaporated to crystallization, generates ferrous chloride crystal, also contains part ferrous chloride solution simultaneously, saturated solution is put into ferrous chloride The iron crystallization tank performs repeated heating crystallization and cooling crystallization, and the obtained crystallization and saturated solution are transferred to the ferrous chloride finished product tank, and the precipitated water vapor leads to the iron powder reactor and the heating sleeve in the ferrous chloride mixer;

(4) Recycling of crystals or solutions of ferrous chloride

Part of the ferrous chloride crystals generated above, or a solution containing a concentration of ferrous chloride greater than or equal to 40%, is added to the ferrous chloride mixer again to cause crystallization of the solution in the ferrous chloride mixer or increase the chloride ion of the solution saturation;

(5) Calcium chloride neutralization and crystallization: the calcium chloride generated after the spray tower reaction and the incompletely reacted calcium oxide or calcium hydroxide are passed into the neutralization tank, and neutralized with the hydrochloric acid produced by the washing tower, Calcium chloride solution is generated, the neutralized calcium chloride solution is evaporated to crystallization, and the water vapor precipitated in the crystallization process leads to the heating sleeve in the iron powder reactor and ferrous chloride mixer;

(6) Condensation and absorption of precipitated gas

The gas precipitated in the aforementioned steps 1 and 2 is first passed to the washing tower, absorbed by water or industrial waste acid, and hydrochloric acid is generated; the remaining unabsorbed gas is passed to the calcium oxide or calcium hydroxide absorption tower, and calcium oxide or calcium hydroxide is formed after absorbing the gas Calcium chloride, adjust the PH value to 7 to 8, heat and crystallize as calcium chloride crystal or saturated solution finished product, and then the unabsorbed gas is discharged to the atmosphere with an induced draft fan.

According to Fig. 2 and shown in Fig. 3, under one atmospheric pressure, the solubility of hydrogen chloride decreases rapidly with the increase of temperature, and the solubility of ferrous chloride increases rapidly with the increase of temperature. Therefore, adding a sufficient amount of ferrous chloride to industrial waste hydrochloric acid can effectively reduce the solubility of hydrogen chloride in waste hydrochloric acid, especially under the conditions of heating and negative pressure, hydrogen chloride can be easily precipitated.

Claims (6)

1. A salting-out method resource treatment process of industrial waste hydrochloric acid is characterized in that: the processing of industrial waste hydrochloric acid is carried out in a treatment system, and the steps of the treatment process are: (1) Iron powder reaction: put industrial waste hydrochloric acid into the iron powder reactor, and under the absolute atmospheric pressure of 0.01MPa to 0.098MPa, add iron powder into the iron powder reactor, stir and react fully, so that part of the hydrogen chloride reacts to form ferrous chloride ; (2) Mixing of ferrous chloride: Feed the ferrous chloride solution discharged from the iron powder reactor into the ferrous chloride mixer, and then add ferrous chloride crystals or solution, at an absolute atmospheric pressure of 0.01MPa to 0.098MPa, Under the condition of temperature from 50°C to 100°C, make the mass concentration of ferrous chloride solution greater than 30%; stir well, and neutralize with sodium hydroxide until the pH value is 6-7; (3) ferrous chloride crystallization: the discharge of ferrous chloride mixer is evaporated to crystallization, generates ferrous chloride crystal, also contains part ferrous chloride solution simultaneously, saturated solution is put into ferrous chloride crystallization The tank undergoes repeated heating crystallization and cooling crystallization, and the obtained crystallization and saturated solution are transferred to the ferrous chloride finished product tank, and the precipitated water vapor leads to the iron powder reactor and the heating sleeve in the ferrous chloride mixer; (4) recirculation of the crystal of ferrous chloride or solution: the part ferrous chloride crystal of above-mentioned generation, or the solution containing ferrous chloride concentration greater than or equal to 40%, add in the ferrous chloride mixer again, Initiate the crystallization of the solution in the ferrous chloride mixer or increase the saturation of chloride ions in the solution; (5) Calcium chloride neutralization and crystallization: the calcium chloride generated after the spray tower reaction and the incompletely reacted calcium oxide or calcium hydroxide are passed into the neutralization tank, and neutralized with the hydrochloric acid produced by the washing tower, Calcium chloride solution is generated, the neutralized calcium chloride solution is evaporated to crystallization, and the water vapor precipitated in the crystallization process leads to the heating sleeve in the iron powder reactor and ferrous chloride mixer; (6) Condensation and absorption of the precipitated gas: the precipitated gas in the aforementioned steps ⑴ and ⑵ is first passed to the washing tower, absorbed by water or industrial waste acid to generate hydrochloric acid; the remaining unabsorbed gas is led to calcium oxide or calcium hydroxide for absorption After absorbing the gas, calcium oxide or calcium hydroxide generates calcium chloride, adjusts the pH value to 7 to 8, and crystallizes after heating to produce calcium chloride crystals or saturated solution products. 2. The process for recycling industrial waste hydrochloric acid by salting-out method according to claim 1, characterized in that: the concentration of ferrous chloride contained in the ferrous chloride solution is greater than or equal to 40%. 3. the salting-out method resource treatment process of industrial waste hydrochloric acid according to claim 1, is characterized in that: described treatment system comprises iron powder reactor, the ferrous chloride mixer of waste hydrochloric acid, ferrous chloride crystallization tank, ferrous chloride product tank, washing tower, hydrochloric acid product tank, spray tower, neutralization tank, calcium chloride crystallization tank, calcium chloride collection tank and exhaust machine, the front end of the iron powder reactor is connected to industrial waste hydrochloric acid The input pipe port of the rear end is connected to the ferrous chloride mixer of waste hydrochloric acid through the pump and the valve, and the ferrous chloride mixer is connected to the ferrous chloride crystallization tank through the pump and the valve, and the ferrous chloride crystallization tank passes through the The pump and valve are connected to the ferrous chloride mixer and the ferrous chloride finished product tank; the gas valve generated by the iron powder reactor and the ferrous chloride mixer due to heating and negative pressure is connected to the washing tower, and the bottom discharge valve of the washing tower It is connected to the hydrochloric acid product tank, and the valve of the hydrochloric acid product tank is connected to the neutralization tank; the gas valve on the top of the washing tower is connected to the calcium hydroxide spray tower, and the gas from the top of the calcium hydroxide spray tower is discharged through the exhaust machine, and the bottom discharge is connected to the neutralization tank. pool, the neutralization pool is connected to the calcium chloride crystallization tank, and the calcium chloride crystallization tank is connected to the calcium chloride collection tank. 4. the salting-out method according to claim 3 is characterized in that: the discharged material of the ferrous chloride crystallization tank is divided into two lines, and one line is the chlorination of the discharge. The ferrous finished product is directly collected in the ferrous chloride finished product tank, and the other line is connected with the ferrous chloride mixer through a pump and a valve. 5. The process of salting out method resourceful treatment of industrial waste hydrochloric acid according to claim 3, characterized in that: the high-temperature water vapor produced in the calcium chloride crystallization tank and the ferrous chloride crystallization tank passes through the pipeline respectively Enter the iron powder reactor and the waste ferrous chloride hydrochloride mixer to heat the materials in the iron powder reactor and the waste ferrous chloride hydrochloride mixer. 6. The salting-out method according to claim 3 is characterized in that: the iron powder reactor and the ferrous chloride mixer are equipped with an iron powder inlet with a sealing device, At the same time, it is also equipped with a sealed agitator, and the bottom of the iron powder reactor and the ferrous chloride mixer are equipped with sewage outlets with valves.