JP2001026402A - Recovery of hydrogen chloride - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably recover hydrogen chloride from hot exhaust gas, based on gaseous hydrogen chloride generated by thermally decomposing a chlorine- containing resin, while removing the moisture or the like from the host exhaust gas by containing the hot exhaust gas with an organic solvent that is not active to the hydrogen chloride and containing water of an amount that exceeds the saturated solubility. SOLUTION: The chlorine-containing resin in the waste of vinyl chloride resin or the like is heated to around 300-400 deg.C and decomposed into a carbide using a rotary kiln or the like, preferably, having a non-oxidized atmosphere with an inert gas such as nitrogen. The exhaust gas based on gaseous hydrogen chloride discharged when decomposed is brought into contact with the organic solvent, preferably, a chlorine-containing hydrocarbon such as ethylene dichloride, which is not active to the hydrogen chloride and containing water of an amount that exceeds the saturated solubility while keeping gas state, preferably the temperature of >=200 deg.C. This method does not cause the clogging of pipelines owing to high boiling pint organic compounds. The impurities caused by the moisture and additives are efficiently removed and the purified gaseous hydrogen chloride can be recovered stably.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel method for recovering purified hydrogen chloride in gaseous form from an exhaust gas discharged from a pyrolysis step of a chlorine-containing resin. More specifically, it is a method of continuously and efficiently removing moisture and other impurities from the exhaust gas to stably recover purified hydrogen chloride in a gaseous state.

[0002]

2. Description of the Related Art Wastes made of chlorine-containing resins such as vinyl chloride resins are being restricted from being burned and disposed of due to the problem of dioxins that may be generated during combustion. On the other hand, there is an increasing social movement regarding the reuse of waste in order to protect limited resources.

Against this background, attempts have been made to recover chlorine-containing resins by dehydrochlorination to recover substantially no chlorine-containing carbides, and to reuse them as fuel having no problem with respect to the generation of dioxins and the like. Various proposals have been made.

[0004] For example, a vinyl chloride resin is indirectly heated to about 350 ° C in a non-combustion atmosphere, generally in a nitrogen gas atmosphere, and thermally decomposed to obtain a dehydrochlorinated carbide. There is a method of reusing it as a fuel such as a fuel for cement production and a fuel for a blast furnace. On the other hand, in the thermal decomposition, hydrogen chloride is generated together with the carbide. The hydrogen chloride is discharged as an exhaust gas accompanied by heat in the apparatus for performing pyrolysis, and the amount thereof is, for example, as much as 0.6 tons of gas containing hydrogen chloride per t of the vinyl chloride resin. Become.

Therefore, it is desired to develop a technique for recovering the above-mentioned hydrogen chloride and reusing it as a raw material in a process for producing another chlorinated product. In particular, when the recovered hydrogen chloride is used in reactions such as production of ethylene dichloride (EDC) by oxychlorination and production of methyl chloride by reaction with methyl alcohol, hydrogen chloride may be recovered in gaseous form. is necessary.

[0006]

However, at present, almost no studies have been made on a technique for recovering and recycling hydrogen chloride from exhaust gas generated by thermal decomposition of a chlorine-containing resin. The present inventors have conducted various studies on a method for recovering hydrogen chloride in the exhaust gas in a gaseous state, and as a result, have found the following problem.

For example, in the exhaust gas discharged from the pyrolysis step, in addition to the target hydrogen chloride, the moisture absorbed by the chlorine-containing resin in the course of distribution, and the adhesion during storage before the decomposition step. It has been found that there is a relatively large amount of water derived from water that is produced, water added in the process, etc., and it is necessary to remove the water.

[0008] Generally, it is conventionally known that the removal of water in a gas is carried out by cooling the gas to condense the water, and is carried out in various factories.

However, when applying such a separation method by cooling to the exhaust gas discharged from the pyrolysis step, the present inventors found that the clogging of the piping leading to the cooling section occurred in a very short time. It became clear by the experiment. In addition, in film applications such as agricultural films of chlorine-containing resins, an antifogging agent composed of a fluorine-based surfactant is often added to impart antifogging properties to the film. In the case of thermally decomposing a chlorine-containing resin containing such a fluorine-based surfactant, the fluorine-based surfactant is partially decomposed to generate hydrogen fluoride, which may be mixed into hydrogen chloride gas. The decomposition of the fluorine-based surfactant is more likely to occur as the thermal decomposition temperature increases.

Accordingly, it is an object of the present invention to stably remove hydrogen fluoride and other impurities contained in exhaust gas from the exhaust gas from the thermal decomposition process of chlorine-containing resin under the influence of moisture and additives. It is an object of the present invention to provide an industrially effective recovery method which can be carried out.

[0011]

Means for Solving the Problems The inventors of the present invention have conducted studies to achieve the above object, and as a result, first, a substance causing clogging in the removal of water is subjected to a thermal decomposition treatment. It has been found that chlorine-containing resins are various organic additives contained in the product stage, especially high-boiling organic additives. As a result of further study, the exhaust gas is cooled by contacting it with an organic solvent inert to hydrogen chloride while maintaining the state of a hot gas so that the high-boiling organic compound does not solidify. Thus, while preventing the high-boiling organic additive from adhering to the pipe wall, not only can the water condensed in the exhaust gas by the cooling, but also in the exhaust gas due to the organic solvent, other than hydrogen chloride, It has been found that the removal of impurities is performed very efficiently, and the purified hydrogen chloride gas can be stably recovered in gaseous form.

Furthermore, it has been found that the presence of water in an amount exceeding the saturation solubility upon contact with the above-mentioned organic solvent makes it possible to efficiently remove the above-mentioned hydrogen fluoride by the above-mentioned treatment, thereby completing the present invention. Was.

That is, according to the present invention, an exhaust gas containing hydrogen chloride as a main component, which is discharged from a thermal decomposition step of a chlorine-containing resin, is inert and saturated with hydrogen chloride while maintaining a hot gas state. This is a method for recovering hydrogen chloride generated by thermal decomposition of a chlorine-containing resin, which comprises contacting an organic solvent in the presence of an amount of water exceeding the solubility and then recovering the same as hydrogen chloride gas.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, as the above-mentioned chlorine-containing resin, a known resin which can be dehydrochlorinated by thermal decomposition is used without any particular limitation. For example, vinyl chloride resin, vinylidene chloride resin, chlorinated polyolefin and the like can be mentioned. Among them, a vinyl chloride resin is typical.

The exhaust gas to be subjected to the method for recovering hydrogen chloride according to the present invention contains, as additives, high boiling compounds such as phthalic acid esters such as dioctyl phthalate (DOP);
This is an exhaust gas containing hydrogen chloride gas, which is produced by subjecting a chlorine-containing resin containing a fluorine-containing organic compound such as a fluorine-based surfactant to a thermal decomposition treatment in a thermal decomposition step. Usually, the chlorine-containing resin containing these additives may be present at least partially in the chlorine-containing resin as waste, but the method of the present invention can be suitably applied to such a chlorine-containing resin. it can.

In the present invention, the thermal decomposition step is a step of heating the above-mentioned chlorine-containing resin under non-oxidizing conditions to remove hydrogen chloride. The process is adopted without any particular limitation.

A typical example of the thermal decomposition apparatus used in the above process is as follows. A substantially closed rotary kiln type indirect heating furnace capable of moving contents in one direction while rotating a cylindrical body. In addition, those having a structure having a chlorine-containing resin piece inlet at the upstream end of the content, a content outlet at the downstream end, and an exhaust gas outlet at another position at the downstream end are listed. Can be In addition, as a pyrolysis device having another structure, a device such as a fluidized bed type can be used.
The pyrolysis in the pyrolysis step is described by taking the rotary kiln type indirect heating furnace as an example. If the chlorine-containing resin is supplied from the inlet, the kiln is indirectly heated from the inside or outside, and the internal temperature is 300 to It is generally performed by adjusting to 400 ° C. The chlorine-containing resin is dechlorinated while moving in the kiln, is separated into a solid made of dechlorinated chlorine-containing resin (hereinafter also referred to as carbide) and an exhaust gas containing hydrogen chloride, and each is taken out from an outlet. It is.

As described above, since the amount of hydrogen fluoride generated by the decomposition of a fluorine-based surfactant or the like increases as the temperature increases, a relatively high decomposition temperature, for example, 340
The present invention is particularly effective when the thermal decomposition of the chlorine-containing resin is carried out at around 380 ° C.

Of course, the present invention can also be applied to the case where the thermal decomposition is carried out at a temperature higher than the above-mentioned temperature.
If necessary, carbon, hydrocarbon, and the like generated by the decomposition of carbides may be separated to recover the hydrogen chloride gas. For the separation, a conventional technique of absorbing or adsorbing the substance can be applied.

The interior of the kiln is previously replaced with an inert gas, for example, a known inert gas such as nitrogen or argon, in order to provide a non-oxidizing atmosphere. Is recommended to be supplied as a carrier gas. It is also preferable to use hydrogen chloride gas as the inert gas, and it is possible to increase the concentration of the obtained hydrogen chloride gas. Can be obtained. Such high-purity hydrogen chloride gas is effective as the hydrogen chloride gas for the oxychlorination. It is also effective to circulate and use a part of the hydrogen chloride gas as the carrier gas.

The exhaust gas contains, together with hydrogen chloride produced by thermal decomposition of the chlorine-containing resin, water supplied along with the chlorine-containing resin and other undecomposed organic components. It is discharged from the pyrolysis process as hot gas.

According to the analysis by the present inventors, phthalic acid esters such as dioctyl phthalate (DOP) are added to the exhaust gas as an additive for imparting necessary physical properties during or after molding the chlorine-containing resin. It has been found that such high-boiling organic matter is generally contained at a concentration of several hundreds to several thousand ppm, and in some cases even tens of percent. The hydrogen fluoride gas varies depending on the type of the fluorine-containing resin used, but may reach 200 ppm in some cases.

For this reason, when the above-mentioned exhaust gas is directly cooled by gas cooling, which is a conventional method for removing water in a gas, these high-boiling organic substances are condensed in the pipe, Since the pipe is clogged within a short time, stable operation cannot be performed for a long time. The greatest feature of the present invention is that the above-mentioned exhaust gas is treated with an organic solvent (hereinafter referred to as water) in the presence of an amount of water that is inert to hydrogen chloride and exceeds the saturation solubility while maintaining a hot gas state. (Hereinafter referred to simply as a hydrated organic solvent).

That is, by such an operation, the high-boiling organic compound which causes clogging of the pipe can be dissolved or suspended in the water-containing organic solvent before or at the same time as condensing, and as a result, it adheres to the pipe or the like. And can be removed from the gas. Further, in the system of the aqueous organic solvent of the present invention in which an amount of water exceeding the saturation solubility is present,
Due to the presence of the phase-separated water, the hydrogen fluoride contained in the exhaust gas is preferentially and extremely efficiently absorbed and removed by the hydrogen chloride.

In the organic solvent, a certain amount of water is present in a dissolved state, and the water can also absorb hydrogen fluoride. However, the amount is generally small, and the amount of hydrogen fluoride contained in the exhaust gas is small. Is insufficient for practical removal, or the absorption rate is low, which is not practical.

Further, the exhaust gas is cooled by contact with the water-containing organic solvent, and most of the water is condensed in the water-containing organic solvent.

In the above-mentioned water-containing organic solvent, the mode in which water is present in an amount exceeding the saturation solubility may be such that the water present at the time of contact with exhaust gas is present. It is preferable to mix a predetermined amount of water with the water. Further, in the above embodiment, condensed water in which water contained in the exhaust gas is condensed may be used as a part of water. In this case, it is preferable to control the amount of water present in contact with the organic solvent by analyzing the amount of water in the organic solvent after mixing with the exhaust gas.

In the present invention, when a tin-based stabilizer is added to the chlorine-containing resin, the tin compound originating from the stabilizer may be present as a vapor in the exhaust gas. Also has the effect of being easily extracted into the organic solvent and being removed from the hydrogen chloride gas.

On the other hand, a low-boiling substance insoluble in a water-containing organic solvent containing hydrogen chloride as a main component exists as a gas phase.

Therefore, the above operation makes it possible to stably recover the hydrogen chloride from which most of the water has been removed, without the clogging of the piping by the high-boiling organic compound.

Hereinafter, the operation of contacting the aqueous organic solvent with the exhaust gas will be described in more detail.

First, it is important to maintain the temperature of the exhaust gas before contact with the water-containing organic solvent in the state of a hot gas. Generally, what is necessary is just to maintain the boiling point of the high-boiling organic compound or higher, especially 200 ° C. or higher, more preferably,
It is preferable to maintain the temperature at 250 ° C. or higher.

Here, the method for maintaining the exhaust gas at the above temperature is not particularly limited. For example, a method of keeping the exhaust gas pipe warm, a method of heating the exhaust gas pipe, and the like are common.

As the organic solvent constituting the water-containing organic solvent, an organic solvent which is substantially inert to hydrogen chloride is used without any particular limitation. Particularly preferred is an organic solvent having a boiling point higher than the temperature after contact with exhaust gas. Examples of suitable organic solvents include chlorine-based organic solvents such as ethylene dichloride (EDC), dichloromethane and chlorobenzene, and non-chlorine-based organic solvents such as n-hexane. Among them, a chlorine-based organic solvent is preferably used because of low contamination of hydrogen chloride and low solubility of hydrogen chloride. In particular, when the obtained hydrogen chloride is used for the production of EDC, a part of the produced EDC can be used as the organic solvent, and the impure EDC after contact with the exhaust gas is used as the EDC. The present invention can be purified and reused in a manufacturing facility, and the present invention can be carried out extremely economically.

It is also possible to use, as the organic solvent, heavy ends obtained from a purification step in the production of chlorine-based organic solvents such as EDC, dichloromethane, chlorobenzene and the like. In the mode using such heavy ends, the same effects as described above can be obtained.In addition, the heavy ends after contacting with the exhaust gas may be circulated and treated in the detoxification equipment existing in the purification step, for example, a combustion furnace or the like. It also has the advantage that it can be done.

In the present invention, the amount of water contained in the organic solvent is not particularly limited as long as it exceeds the saturation solubility in the organic solvent. Therefore, the amount of water exceeding the saturation solubility is preferably adjusted to 1% by weight or more, preferably 2% by weight or more based on the organic solvent. Conversely, if the amount of water is too large,
Since the amount of dissolved hydrogen chloride gas increases and the loss increases, the amount of water exceeding the saturation solubility is 3
It is preferable to adjust the amount to be 0% by weight or less, preferably 25% by weight or less.

It is preferable that the water-containing organic solvent in which the amount of water contained is adjusted as described above is cooled upon contact with the exhaust gas. The temperature of the water-containing organic solvent is a temperature lower than the boiling point of the water-containing organic solvent, preferably lower than the boiling point by 20 ° C. or more.

Further, the method of contacting the exhaust gas with the water-containing organic solvent is not particularly limited, and a known gas-liquid contact method is employed. For example, (a) a method of forcibly forming a gas-liquid mixed flow of an exhaust gas and a water-containing organic solvent using an ejector, (b) a method of spraying a water-containing organic solvent into an exhaust gas flow,
(C) A method in which exhaust gas is directly blown into a liquid phase comprising a water-containing organic solvent. In the method (b), opposing contact is preferable, and a mode in which a water-containing organic solvent is sprayed from above on the upward flow of exhaust gas to make opposing contact is recommended. Further, in the method (c), a mode using a packed tower, a bubble bell tower, or the like is preferable since the contact can be performed effectively.

Among these contact methods, the most effective and simple one is the method using the ejector (a).

In the present invention, after contacting the exhaust gas with a water-containing organic solvent, a gas phase containing hydrogen chloride as a main component is obtained,
By recovering the gas phase, most of the impurities such as organic compound components and moisture are removed, and purified hydrogen chloride can be recovered.

For the recovery of the gas phase containing hydrogen chloride as a main component, a mode in which the water-containing organic solvent can be efficiently removed is suitably adopted. For example, in the above method (a), since gas-liquid mixed phase flow is obtained after contact, it is preferable to recover the gas phase using a known gas-liquid separation device. Also,
In the methods (b) and (c), since the gas phase is generally obtained from the top of the device, a gas-liquid separation device is not separately required, but a demister may be attached to the device outlet of the gas phase or the device outlet may be used. In the vicinity, it is preferable to make contact with a cooled water-containing organic solvent.

The gas phase thus recovered depends on the type and supply amount of a carrier gas such as an inert gas in the above-mentioned pyrolysis step.
It is contained at a concentration of about 00% by volume. It is preferable that the conditions in the thermal decomposition step be set so that the hydrogen chloride concentration is 90% by volume or more, preferably 95% by volume or more.

The gas phase may be recovered as it is and used as a hydrogen chloride source in another step, but it is preferable to further remove a trace amount of water. For the removal of the water, a known method is employed without particular limitation. For example, a cryogenic separation method of cooling the gas phase to −20 ° C. or less, concentrated sulfuric acid,
A method of contacting with a dehydrating agent such as calcium chloride, zeolite, or acid-resistant molecular sieve can be suitably performed.

Hereinafter, the present invention will be described more specifically with reference to the accompanying drawings, but the present invention is not limited to the accompanying drawings. FIG. 1 and FIG. 2 are process diagrams showing a typical embodiment in the method for recovering hydrogen chloride of the present invention.

In FIG. 1, a chlorine-containing resin 2 is supplied to a thermal decomposition step 1 and is decomposed by being heated in a non-oxidizing atmosphere to form an exhaust gas 4 containing a carbide 3 as a solid and hydrogen chloride as a gas. And generate

The exhaust gas is kept in a hot gas state by heating or heating the line 4, and the gas-liquid mixing device (in the figure, the ejector (a) is used in FIG. 18 indicating the contact method).

The water-containing organic solvent is cooled, if necessary, through a cooler, and then supplied to the gas-liquid mixing device through a line 5, where it is brought into contact with the exhaust gas, and the exhaust gas is cooled (preferably quenched). And dissolve the organic matter in it.

The mixing ratio of the water-containing organic solvent and the exhaust gas in the gas-liquid mixing device, depending on the performance of the device of the ejector or the like, in general, with respect to the exhaust gas 1 Nm ³ 10 to 20
0 L, preferably 30-100 L. Next, the mixture of the exhaust gas and the water-containing organic solvent obtained from the gas-liquid mixing device 18 is sent from the line 6 to the gas-liquid separation device 7, where the mixture is separated into a gas phase and a liquid phase. The liquid phase is mainly composed of a water-containing organic solvent, in which components soluble in the water-containing organic solvent and components having a lower boiling point than the organic compound in the exhaust gas are dissolved or suspended.

The liquid phase is withdrawn from the bottom of the gas-liquid separator 7 and a part thereof is circulated to the gas-liquid mixer 18 for contact with the exhaust gas. Of course, it is also possible to use a new water-containing organic solvent in the gas-liquid mixing device 18 without performing the circulation.

FIG. 2 shows a countercurrent contact device 24 for spraying a water-containing organic solvent by a shower against an upward flow of exhaust gas instead of a contact method using a gas-liquid mixing device such as an ejector.
Is shown. That is, the exhaust gas 4 obtained from the pyrolysis step 1 is kept in a hot gas state by keeping or heating the line 4 while maintaining such a high temperature state.
After being supplied to the countercurrent contact device 24 and coming into contact with the water-containing organic solvent sprayed from the spray nozzle 25, it is taken out of the tower 8 as a gas phase from the line 8.

In this case, the water-containing organic solvent to be sprayed is cooled through a cooler if necessary, and then sprayed from a nozzle 25 through a line 26. It is preferable that such spraying is performed by providing a spray nozzle in multiple stages as shown in the figure, because effective contact can be achieved. Further, the spraying amount is 10 to 200 L, preferably ³⁰ to 100 L per 1 Nm ^{3 of} the exhaust gas, though it depends on the fineness of the shower to be sprayed. On the other hand, a gas containing hydrogen chloride from which most impurities have been purified and removed is recovered as a gas phase of the gas-liquid separation device 7 in FIG. 1 or as a gas phase from the countercurrent contact device 24 in FIG. Since the gas containing hydrogen chloride taken out as the gas phase may contain some of the above-mentioned organic substances and moisture, the condensate 23 is supplied from the line 8 through the cooler 22 as necessary.
Is removed as a drain, and after that, the above-mentioned dehydration treatment is performed in the dehydration equipment 9 to obtain a highly purified hydrogen chloride 10
As such, it can be reused in any production process such as a production process by oxychlorination of EDC. Further, the above-mentioned hydrogen chloride can also be used as a seal gas of a thermal decomposition apparatus used in the thermal decomposition step.

The gas phase of the gas-liquid separation device 7 shown in FIG. 1 or the gas phase of the gas-liquid contact device 24 shown in FIG. 2 is provided with a packed layer 21 near the top of each device. It is preferable that the contact and supply are performed from the step 12 because organic substances such as EDC and benzene and moisture in the gas phase can be further reduced. Such a cooling temperature is particularly preferably 30 ° C. or lower, generally 20 to −5 ° C.

It is preferable that the remainder of the liquid phase is sent from the line 20 to the purifier 13 for distillation or distillation. 1 and 2, the liquid phase is supplied to a purification device 13. In the purification of the liquid phase, the bottom liquid is set near the boiling point of the water-containing organic solvent, the water-containing organic solvent is taken out as vapor from the top, and the high-boiling organic compound, metal, and
Aqueous organic solvent waste liquid 1 containing other impurities at high concentration 1
4 is taken out.

As described above, when heavy ends are used as the organic solvent, the above purification is not particularly required.

The organic solvent gas 15 taken out from the top of the tower is cooled, and water 17 entrained by the water-containing organic solvent is removed by a water separator 16 or adjusted as necessary. It is preferable to reuse it for contact.

Of course, the purified water-containing organic solvent is used as the water-containing organic solvent 11 to be supplied to the gas-liquid separator 7 of FIG. 1 or as the water-containing organic solvent 11 to be supplied to the countercurrent contact device 24 of FIG. It is also possible.

In the above-mentioned refining tower, when a production facility for the water-containing organic solvent to be used is present in the vicinity, it is preferable to use the purification facility of the production facility.

[0058]

As will be understood from the above description, according to the present invention, highly purified hydrogen chloride is obtained from the exhaust gas discharged from the pyrolysis step of the chlorine-containing resin to which the various additives have been added. Gas can be stably recovered for a long period of time, and its industrial value is extremely high.

[0059]

The present invention will be described in more detail with reference to the following Examples, which by no means limit the scope of the present invention.

Example 1 The pyrolysis of a chlorine-containing resin and the recovery of hydrogen chloride were performed according to the steps shown in FIG.

That is, the chlorine-containing resin 2 has an average particle size of 5 m.
The vinyl chloride resin pieces crushed to m were supplied to a pyrolysis step 1 using a rotary kiln-type pyrolysis apparatus, and heated to 380 ° C. in an atmosphere of nitrogen gas to perform pyrolysis.

The vinyl chloride resin was used in an amount of 30 parts by weight of a plasticizer (DOP), 0.1 part by weight of an antifogging agent (perfluoroalkyl-containing oligomer), and a stabilizer (tin) with respect to 100 parts by weight of the resin. Compound) was contained in an amount of 2 parts by weight.

The carbide 3 obtained by the above decomposition is recovered, and the exhaust gas 4 containing hydrogen chloride as a gas is recovered.
Was supplied to an ejector as a gas-liquid mixing device 18 while maintaining the temperature of the line 4 at 300 ° C. or higher. Further, after cooling the EDC containing water to 40 ° C. with a cooler, 60 L of exhaust gas 1 Nm ^{3 was} supplied from the line 5.
And supplied continuously to the gas-liquid mixing device to make contact with the exhaust gas. While analyzing the amount of water in the organic solvent after contact with the ejector, the amount of water mixed with the supplied organic solvent is adjusted so that the amount of water exceeding the saturation solubility in the organic solvent is 7% by weight based on the organic solvent. It was adjusted.

Next, the mixture of the exhaust gas and EDC obtained from the gas-liquid mixing device 18 was sent to the gas-liquid separation device 7 from the line 6 and separated into a gas phase and a liquid phase. In the gas-liquid separation device, the ED cooled to 30 ° C. was supplied from the line 12 from above the packed bed 21 provided in the gas phase and was brought into contact with the gas phase.

The gas phase obtained from the gas-liquid separator is
A dehydration treatment is performed by passing through a dehydration facility 9 filled with an acid-resistant molecular sieve through a cooler 22, and 80% by volume of hydrogen chloride, 20% by volume of nitrogen, and 10% of water.
t. ppm or less, 2 wt. pm, the remaining hydrogen chloride gas having the remaining impurities was continuously obtained.

The liquid phase obtained from the gas-liquid separator is:
The product was rectified in a rectification column as the purification device 13 to obtain an EDC having a purity of 99%.

As a result of carrying out the above-mentioned steps continuously for one month, there was no blockage of the pipe due to the high-boiling organic substances added to the vinyl chloride resin, and hydrogen chloride could be recovered more stably than the exhaust gas. Was.

Example 2 The pyrolysis of chlorine-containing resin and the recovery of hydrogen chloride were carried out according to the steps shown in FIG.

Exhaust gas 4 obtained in the same manner as in Example 1.
Was supplied to the countercurrent contact device 24 while maintaining the temperature of the line 4 at 300 ° C. or higher. In the countercurrent contact device 24, the EDC containing water is cooled to 30 ° C. from the nozzles 25 provided in three stages, and the water-containing EDC is supplied into the device from the nozzle 25 via the line 26 in an amount of 60 L per 1 Nm ³ of exhaust gas. It was sprayed and brought into contact with the exhaust gas. While analyzing the amount of water in the organic solvent at the bottom of the countercurrent contact device, the amount of water in the organic solvent exceeding the saturation solubility was 10% by weight based on the organic solvent.
The amount of water mixed with the organic solvent to be supplied was adjusted so as to be as follows. A gas phase was recovered from the top of the countercurrent contact device 24.

The obtained gas phase passes through a dehydrator 9 filled with an acid-resistant molecular sieve through a cooler 22 to be subjected to a dehydration treatment.
%, Nitrogen 20% by volume, water 9 wt. ppm or less, 1 wt. Purified hydrogen chloride gas containing ppm and the remainder being other impurities could be continuously obtained.

The liquid phase obtained from the gas-liquid separator is:
The product was rectified in a rectification column as the purification device 13 to obtain an EDC having a purity of 99%. As a result of continuously performing the above-described steps for one month, there was no blockage of the pipe due to the high-boiling organic substances added to the vinyl chloride resin, and hydrogen chloride could be recovered more stably than the exhaust gas.

Comparative Example 1 In Example 1, the amount of water exceeding the saturation solubility in the organic solvent after passing through the ejector was reduced by -1 with respect to the organic solvent.
Hydrogen chloride gas in the exhaust gas was recovered in the same manner except that the amount of water to be added to the EDC was adjusted so as to be% by weight, that is, except that the amount of water was less than the saturated solubility of the organic solvent.

The gas phase thus obtained is subjected to a dehydration treatment by passing through a dehydrator 9 filled with an acid-resistant molecular sieve through a cooler 22 to obtain 80% by volume of hydrogen chloride and 20% by volume of nitrogen. , Water 9 wt. ppm
Hereinafter, 10 wt. As a result, hydrogen chloride gas containing ppm and the balance being other impurities was obtained.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing typical steps in the method of the present invention.

FIG. 2 is a schematic diagram showing another representative step in the method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pyrolysis process 2 Chlorine-containing resin 3 Carbide 7 Gas-liquid separation device 9 Dehydration equipment 10 Hydrogen chloride 11 Water-containing organic solvent 13 Purification device 14 Waste water-containing organic solvent 16 Water separator 17 Water 18 Gas-liquid mixing device 21 Filling layer 22 Cooler 24 Countercurrent contact device 25 Nozzle

 ──────────────────────────────────────────────────続 き Continued on front page F-term (reference) 4D002 AA19 AA23 AA28 AA33 AA40 AB01 AC04 BA02 BA04 BA12 BA13 CA01 CA03 CA07 CA13 DA17 DA35 DA56 DA70 EA02 EA05 EA07 EA13 FA01 GA01 GA02 GA03 GB01 GB02 GB03 GB05 GB08 GB11 HA02 HA06 HA10 AA16 AB01 AB03 CA04 CA10 CA26 CA27 CA41 CA52 CA64 CA72

Claims (3)

[Claims] 1. An exhaust gas containing hydrogen chloride as a main component, which is discharged from a thermal decomposition step of a chlorine-containing resin, is inert to hydrogen chloride and exceeds a saturated solubility while maintaining a hot gas state. After contacting with an organic solvent in the presence of water,
A method for recovering hydrogen chloride generated by thermal decomposition of a chlorine-containing resin, which is recovered as hydrogen chloride gas. 2. The method for recovering hydrogen chloride according to claim 1, wherein the exhaust gas is brought into contact with an organic solvent while maintaining the temperature at 200 ° C. or higher. 3. The method for recovering hydrogen chloride according to claim 1, wherein the organic solvent is a chlorinated hydrocarbon.