JPS6315864B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for treating chlorinated residues.

In chlorination at high temperatures, such as is used, for example, in the production of carbon tetrachloride and/or perchlorethylene from C ₁ to C ₃ hydrocarbons or from partially chlorinated hydrocarbons having 1 to 4 carbon atoms. In particular, an undesirable mixture is formed as a residue which actually contains perchlorinated compounds, hexachlorobenzene as well as hexachloroethane and hexachlorobutadiene.

From an environmental protection as well as an economic and technical point of view, it is an important issue to render these residues harmless and non-toxic. Hexachlorobenzene, which makes up the majority of these residues, is persistent and, when diffused into the environment, accumulates and becomes enriched in living organisms. For this reason,
This residue is often disposed of underground in locations designated by government authorities. However, this method is unsatisfactory, especially in that 5-20% by weight of the chlorine used is lost, depending on the way the chlorination process is carried out.

Furthermore, the method of recovering the chlorine portion if possible and rendering the residue harmless by incineration has considerable technical difficulties. This method presupposes that the residue is in an easily measurable or dosable state, ie it must be fluid. A melt of the residue is obtained only at temperatures above 230°C. This melt is highly corrosive;
Very difficult to handle due to high melting point. Attempts to dissolve this residue are limited by the fact that this type of treatment is only meaningful if there is a small amount of water produced as a combustion product other than the desired hydrogen chloride, otherwise the hydrogen chloride is a less valuable hydrochloric acid , so it is limited to a narrow range. moreover,
This method of rendering harmless chlorinated residues by combustion becomes completely uneconomical, since large amounts of undesirable combustion by-products are formed, such as for example carbon dioxide, carbon monoxide and especially soot. .

Another drawback is the low solubility of these chlorinated residues. For example, hexachlorobenzene about 2/
The chemical composition of the curved residue consisting of 3 and 1/4 hexachlorobutadiene is only about 7.5% soluble by weight in benzene, which is a suitable solvent, and soluble in 1,2-dichloroethane. Only about 1% by weight is dissolved in the.

It is therefore an object of the present invention to provide a process for treating chlorinated residues, which consists in rendering the chlorinated residues fluid at a temperature slightly higher than that required for melting the residues.

Another object of the invention is to provide a combustible mixture in such a way as to allow environmental protection considerations and to provide at least a major portion of the chlorine as anhydrous hydrogen chloride, useful for example in chlorination, to reduce costs and reduce costs. The goal is to recover while maintaining the level.

Other objects and advantages of the present invention will be understood from the following detailed description.

A tar-like product generated as a by-product in the pyrolysis of dichloroethane to vinyl chloride monomer and in the treatment of pyrolysis products or crude 1,2-dichloroethane resulting from direct chlorination and/or oxychlorination of ethylene. It is now known that hydrocarbons are suitable solvents for the present task of treating chlorinated residues. Alternative solvents are hydrocarbons with a boiling point of 160 DEG to 300 DEG C. and low aromatic content.

The object of the invention has the following weight ratios: hydrogen:chlorine=0.028-0.06:1 oxygen:carbon=0.0038-0.0089:1 and the following atomic ratio: carbon:hydrogen=1:1.1-1.9. in a chlorine- and oxygen-containing hydrocarbon or in a mixture thereof with a hydrocarbon having a boiling point of 160 to 380 °C at 1 bar absolute and with a carbon:hydrogen atomic ratio of 1:1.85 to 2, 100~180℃
A method for treating chlorinated residues, characterized by a step of dissolving the chlorinated residues at a temperature of . The hydrocarbon should be used in an amount to produce a liquid composition with a hydrogen:chlorine weight ratio of 0.028 to 0.05:1.

The amount of chlorinated residue in this liquid composition is preferably 20 to 50% by weight.

Further, the temperature during the treatment is determined by the following formula: t = x + 55 / 0.66 ± 5 (where t is the temperature (°C) and x represents the amount of chlorinated residue expressed in weight % based on the total weight of the composition. ) is desirable.

The correction factor ±5 represents the acceptable range of optimum temperature.

Furthermore, the hydrogen:chlorine ratio in the composition is from 0.028 to
A ratio of 0.04:1 is desirable.

The treatment is carried out in a technically suitable range of 1.2 to 5.0 bar absolute, although higher pressures can also be used if necessary.

The chlorinated residues to be treated according to the invention are, as mentioned above, unpleasant by-products obtained in chlorination processes, especially high-temperature chlorinations. Such a residue is a mixture consisting of at least 95% by weight, and in most cases 100% by weight, of perchlorinated products. The basic ingredients are hexachlorobenzene, hexachlorobutadiene and hexachloroethane. Additionally, small amounts of chlorinated hydrocarbons, which are desirable for the chlorination process itself, may be present in the mixture. Such chlorinated residues therefore have a chemical composition that can be expressed with a fairly good approximation by the following general formula: C _5-6 Cl _5.8-6.0 . The hydrogen component expected in the treatment according to the invention is practically completely absent.

The oxygen- and chlorine-containing hydrocarbons used according to the invention for the treatment of chlorinated residues are the crude chlorine-containing hydrocarbons resulting from the pyrolysis of dichloroethane or from the pyrolysis products and direct chlorination and/or oxychlorination of ethylene. , 2-dichloroethane. The mixture composition is C _3.0-3.5 H _4.0-5.5 Cl _2.6-3.6 O _0.01-0.02 and C _2.0-2.5 H _3.0-3.5 Cl _2.4-3.0 O _0.01-0.015 according to the following comprehensive formula. Tar-like mixtures such as those shown can be used. Therefore, this chlorinated residue has the following weight ratios: hydrogen:chlorine = 0.028 to 0.06:1, oxygen: carbon = 0.0038 to 0.0089:1, and the following atomic ratios: carbon:oxygen = 1:1.1 to 1.9. It is something that you have.

The tar-like composition of the formula is obtained in a primary treatment step of the pyrolysis products which consists of rapid cooling of the pyrolysis products after leaving the pyrolysis furnace. The low carbon composition represented by the formula is prepared by converting unreacted 1,2 dichloroethane from pyrolysis into crude 1,2 dichloroethane from direct and/or oxychlorination of ethylene after separating the low boiling components and the desired product vinyl chloride monomer. ,2-
It is obtained as a distillation residue in a step consisting of recovery in pure form together with dichloroethane.

The tar-like mixtures mentioned above often contain some solid materials such as coke and metal chlorides. For this reason, it is desirable to pass these mixtures through heated fine filters before using them according to the invention. Alternatively, the chlorinated residue already prepared for treatment can be passed through before being metered into the combustion plant.

Examples of alternatively used hydrocarbons having a boiling point range of 160 to 380 °C at 1 bar absolute and a carbon:hydrogen atomic ratio of 1:1.85 to 2.0 are those with an aromatic content of 10% by weight or less. Some kerosene as well as heavy oil or light oil.

The aforementioned treatment agents can be used alone or in mixtures. The use of this tar-like mixture as a processing agent is particularly important since tar-like processing agents are undesirable by-products during vinyl chloride monomer production and are best treated by combustion. desirable. In this case, it is also possible within the scope of a preferred embodiment of the process according to the invention to co-use small amounts of chlorinated hydrocarbons with a boiling point range of 160 to 380°C, for example in order to adjust the carbon/hydrogen/chlorine balance of the treatment agent. It is.

The chlorinated residue can be dissolved in a known manner, for example in a pressurized vessel (autoclave) equipped with a reflux device. The order in which the ingredients are added is not critical. It is advisable to limit the residence time of the treatment agent to about 10 hours, otherwise the decomposition of the hydrogen chloride will cause the pressure in the vessel to exceed a meaningful pressure range of about 5 bar absolute. It may rise. The process can in principle be carried out both continuously and batchwise.

Finally, the chlorinated residue treated according to the invention
Combustion devices known per se can be fed. Appropriate combustion methods are described, for example, in West German Publication No. 2827761
It is stated in the specification of the No.

By means of the method of the invention it is possible to treat chlorinated residues, in particular those obtained in high temperature chlorination processes, in such a way that they can be incinerated without causing environmental pollution. moreover,
such that at least a portion of the amount of chlorine present in the residue can be fed, for example, to oxychlorination.
It can also be recovered as anhydrous hydrogen chloride, which can be recycled. The process according to the invention is particularly advantageous as a safety method in complex production processes used in the chemical industry, since in addition to the above-mentioned chlorinated residues, the tar obtained during the production of vinyl chloride can also be rendered harmless.

Next, the present invention will be explained in more detail based on Examples and Comparative Examples.

Example 1 In the high temperature chlorination process for producing perchlorethylene, a residue with the following composition is 125
Kg/h occurs in the following amounts: Perchlorethylene 2.0% by weight Hexachloroethane 4.7% by weight Hexachlorobutadiene 23.9% by weight Hexachlorobenzene 69.4% by weight This chlorinated residue is produced under operating conditions of 270°C and 2.6 bar absolute pressure. It was obtained in a molten state in a concentrator. The residue contained 22.7% by weight carbon and 77.3% chlorine. 1000 Kg of residue was injected every 8 hours into a transport cart having a volume of approximately 4 m ³ , equipped with a compressed air driven stirrer and heated by 6 bar of steam. All parts in contact with the product were made of stainless steel.

During the 20 minute injection process, the molten residue was
The cart was fed via tubing with a throughput of Kg/hr. 3600 Kg of a tar-like fluid composition obtained from vinyl chloride production was added to the chlorination residue in an injection tube. This composition had the following analytical data: Carbon 28.58% by weight Hydrogen 3.67% by weight Chlorine 67.64% by weight Oxygen 0.11% by weight In addition, it had a carbon:hydrogen atomic ratio of 1:1.95. Hydrocarbon 250, which is a distillation fraction with a boiling point range of 180-220℃
Also added Kg. The last two additives had ambient temperature, but the temperature of the whole mixture was 150
It was maintained at ℃. At the end of the injection process, there was a total mixture weight of 2233 Kg in the cart, in which the proportion of chlorinated residue was 43.8% by weight. The hydrogen:chlorine weight ratio was 0.035:1. The pressure above the mixture was initially about 1.05 bar, but rose to about 2.2 bar absolute at the end of the injection process. The final product was a solution and the melting process took place simultaneously as the components fluidized together.

The chlorinated residue treated in this way is easily meterable and can be fed to a combustion plant.

Example 2 The method of Example 1 was repeated with the following changes: Heating of the transport cart was carried out by steam at 2.2 bar absolute. Chlorinated residue with the composition described in Example 1
9000Kg of tar-like, fluid mixture resulting from vinyl chloride production, with a throughput of 3000Kg/hour for 1000Kg
was injected. This mixture had the following composition: Carbon 24.49% by weight Hydrogen 2.86% by weight Chlorine 72.45% by weight Oxygen 0.20% by weight After about 20 minutes, a solution with a proportion of chlorinated residues of 25% by weight was obtained. Obtained. The temperature of the mixture was maintained at 121°C. The weight ratio of hydrogen:chlorine in the mixture is 0.029:
It was 1. The pressure above the mixture increased from an initial 1 bar absolute to 3 absolute bar.

The chlorinated residue treated in this way can be easily metered and fed to a combustion device.

Control Example 1 10 g of chlorinated residue having the composition described in Example 1 and a carbon:hydrogen atomic ratio of 1: were placed in a glass cylinder tube.
1.33 and 10 g of hydrocarbon were injected. After the cylinder tube had melted, the temperature was increased to 200°C. This mixture did not dissolve.

Example 3 In a glass cylinder tube (same as Control Example 1),
10 g of the chlorinated residue of the composition described in Example 1 were injected together with 40 g of the tar-like mixture obtained during vinyl chloride production as described in Example 1. After the cylinder tube had melted, the temperature was increased to 110°C. The chlorinated residue was completely dissolved.

Although only some aspects and embodiments of the invention have been described, other changes and modifications may be made without departing from the spirit and scope of the invention as defined in the claims. It will be obvious to those skilled in the art that modifications are possible.

Claims (1)

[Claims] 1. A chlorinated residue having a hydrogen:chlorine weight ratio of 0.028 to 0.06:1 and an oxygen:carbon weight ratio of 0.0038 to 0.0089:1 at a temperature of 100 to 180°C, and carbon:hydrogen. having a boiling point range of 160-380°C at 1 bar absolute in or with a chlorine- and oxygen-containing hydrocarbon in which the atomic ratio of carbon:hydrogen is 1:1.1-1.9 and the carbon:hydrogen atomic ratio is 1:1.85-1.85. The proportions of the components should be selected in such a way that a fluid mixture with a hydrogen:chlorine weight ratio of 0.028 to 0.05:1 is obtained. Characteristic method for treating chlorinated residue. 2 The proportion of chlorinated residue in the mixture is 20 to 50% by weight
The method according to claim 1, characterized in that: 3 The weight ratio of hydrogen:chlorine in the mixture is 0.028~
3. A method according to claim 1 or 2, characterized in that the ratio is 0.04:1. 4 The temperature during treatment is expressed by the following relational expression: t = x + 55 / 0.66 ± 5 (where t means temperature (°C), and x represents the proportion of chlorinated residue expressed in weight % with respect to the total weight of the mixture. 4. A method as claimed in claim 1, characterized in that the method is characterized in that: