JPH07166168A - Method for reforming coal tar - Google Patents

Abstract

PURPOSE:To provide a method for reforming a coal tar, capable of economically obtaining a coal tar rich in light distillation fractions under conditions comprising relatively low temperature and pressure. CONSTITUTION:A water-added tar is sprayed and brought into contact with a coal carbonization gas just after released from a coal on the carbonization of the coal in a coal carbonization oven 11, thus pyrolyzing the inner polymer structures of the coal contained in the coal carbonization gas to react the generated low molecular radicals of the coal tar with hydrogen atoms supplied from the water-added tar for the hydrogenative stabilization of the low molecular radicals. The treated coal tar is cooled with a heat exchanger 19, and subsequently separation-recovered into a coal tar rich in light distillation fractions and the water-added tar with a gas-liquid separating machine 20.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for reforming coal tar.

[0002]

2. Description of the Related Art For example, about 70% of coal tar generated in a coal carbonization process such as in a steel mill coke oven is a heavy fraction having a boiling point of about 300 ° C or higher, and about half of them is called medium pitch. It is a high boiling fraction. For a long time, a reforming method for lowering the molecular weight of such a heavy fraction of coal tar to lighten it has been studied. As one of these studies, for example, the use of a hydrogenation catalyst, a pressure of 50 to 150 atm, a temperature of about 400 to 450 ℃ under high temperature and high pressure reaction conditions of coal tar by the method of hydrothermal decomposition of coal tar Many studies on hydrocracking have been reported (eg, Fuel, vol.68, No.2, p.161-167 (1989), Fuel Process).
Technology, vol.20, No.1 / 3, P.249-256 (1988)).

Also, many studies have been made on a method of reducing the molecular weight of coal tar by reducing the molecular weight thereof only by thermal decomposition.
For example, a method of directly pyrolyzing coal tar by utilizing sensible heat of coke oven gas (Japanese Patent Laid-Open No. 52-148506) has been proposed.

[0004]

However, in the former method for hydrocracking coal tar, in order to lighten the heavy fraction in the coal tar, it is necessary to remove the heavy coal in coal tar under severe reaction conditions of high temperature and high pressure. In order to prevent the heavy polymer compounds from being pyrolyzed into low molecular weight compounds and then condensing each other when cooled, they are hydrogenated and stable to hydrogenation low molecular weight compounds. And need to. Since such a process requires expensive exposure-resistant high-pressure equipment, it cannot be an economical practical process for improving the added value of the reaction product.

Further, due to the reaction under high temperature and high pressure conditions, the heavy fraction of coal tar is lightened, and at the same time, the light fraction of the light fraction of coal tar is gasified. Therefore, there is a problem that a light fraction of coal tar is lost.

On the other hand, in the latter method of directly pyrolyzing coal tar, the heavy fraction of coal tar is pyrolyzed and lightened. However, since it recondenses and becomes heavy, reforming of coal tar cannot be sufficiently achieved. Also, like the former, the light fraction of coal tar is partially gasified during the thermal decomposition process,
A loss of light fraction of coal tar occurs.

The present invention has been made in view of the above points, and provides a method for reforming coal tar, which can economically obtain coal tar rich in light fractions under low pressure conditions.

[0008]

According to the present invention, in the coal carbonization process, hydrogenated tar or heavy petroleum-based oil is sprayed and brought into contact with the coal carbonization gas immediately after being discharged from the coal during carbonization, and the coal carbonization is carried out. Low-molecular radicals of coal tar, which are contained in gas and are generated by thermal decomposition of the coal polymer structure in the coal during carbonization, are hydrogen atoms donated by the hydrogenated tar or the petroleum heavy oil. The present invention provides a method for reforming coal tar, characterized in that the low-molecular radical is hydrogenated and stabilized by reacting with.

Hereinafter, the method for reforming coal tar of the present invention will be described in detail. For example, in a coal carbonization process such as in a steel mill coke oven, in the coal carbonization gas immediately after being released from the coal during carbonization, in addition to the volatile components in the coal,
There are low-molecular radicals of coal tar generated by thermal decomposition of coal polymer structure. Coal polymer structure means W
As shown in Iser's coal model structure, it means a structure in which condensed aromatic rings, which are structural units, are central to each other and are bound to each other by methylene, ether, or the like. This coal polymer structure has a high temperature (for example, 400 to 1) during carbonization.
(000 ° C.) is thermally decomposed to generate a gaseous low-molecular radical. When the temperature decreases, some of these low-molecular radicals condense with each other to form a polymer, and become a hard fraction of coal tar. That is, for example, in a steel mill coke oven, a large amount of water is sprayed on a coke oven gas containing low-molecular radicals of coal tar generated from the oven at a high temperature of about 700 to 800 ° C. to generate a coke oven gas. Is instantly cooled to a low temperature of about 80 ° C. In this cooling process,
The low-molecular radicals are aggregated in water, and some radicals are condensed with each other to be polymerized. This is because, in the state where hydrogen in the aggregation process is insufficient, the radicals are stabilized by hydrogen atoms as small molecules, and also by the condensation of the radicals to polymerize.

Therefore, in the present invention, hydrogenated tar or heavy petroleum-based heavy oil is added to the coal carbonization gas immediately after the coal carbonization gas is released from the coal, that is, before the low-molecular radicals are condensed at high temperature. Spray the oil into contact. The hydrogenated tar is an oil obtained by hydrogenating coal tar according to a conventional method, and the petroleum heavy oil is a crude oil heavy oil fraction or a heavier fraction thereof. Such hydrogenated tar and heavy petroleum oil contain more hydrogen atoms than coal tar and have a hydrogen donating ability. Therefore, the low-molecular radicals are hydrogenated by reacting with hydrogen atoms in a high temperature atmosphere. Hydrogenated low molecular weight radicals become low molecular weight compounds and are stabilized, and after that, they do not condense with each other even when cooled, so the finally obtained coal tar has a desired quality rich in light components. .

Here, as a hydrogen atom source, hydrogenated tar containing more hydrogen atoms and excellent in hydrogen donating ability than coal tar is most suitable in view of process formation. However, it may be a heavy petroleum oil containing a large amount of hydrogen atoms with respect to carbon atoms as compared with coal tar.

[0012]

The method for reforming coal tar of the present invention is to remove low-molecular radicals in the coal carbonization gas immediately after they are generated in the coal carbonization process under high temperature conditions by sensible heat during the carbonization process, under hydrogenated tar or petroleum. By reacting with hydrogen atoms donated by the heavy oil system to hydrogenate and stabilize it, low molecular weight radicals are prevented from cooling and condensing with each other to form a heavy fraction of coal tar. In addition, since coal tar can be reacted in the nascent gas state, there is no need for a step of pyrolyzing coal tar, which has a large amount of heavy fractions, under high-pressure and high-temperature conditions. It does not gasify.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view showing an example of a processing apparatus used in the coal tar reforming method of the present invention.

Reference numeral 11 in the drawing denotes a carbonization furnace in which coal is loaded. The dry distillation furnace 11 is equipped with a heating device 12. The dry distillation furnace 11 is connected to a liquid gas mixer 14 via a pipe 13. On the other hand, the tank 15 in which hydrogenated tar is stored is connected to the liquid gas mixer 14 via a pipe 16. A pump 17 for sending liquid is provided in the middle of the pipe 16.
Is provided.

A pipe 18 is connected to the outlet side of the liquid-gas mixer 14, a heat exchanger 19 is provided in the pipe 18, and a gas-liquid separator 20 is provided further downstream. Gas-liquid separator 2
A pipe 21 for sending gas and a pipe 22 for sending liquid are connected to 0. The former piping 21
A gas-liquid separator 24 is connected via a heat exchanger 23. The gas-liquid separator 24 includes a pipe 25 for discharging gas,
A pipe 26 for discharging the liquid is connected.

Using the processing apparatus 10 having the above structure, coal tar is reformed as follows. First, coal is loaded into the carbonization furnace 11, and the carbonization is performed while controlling the temperature of the heating device 12 so that the furnace wall temperature of the carbonization furnace 11 is 1000 ° C. As a result, carbonization gas is generated from the coal. The amount of the carbonization gas is about 0.3 to 0.4 Nm ³ / kg of coal, and the amount of coal tar generated is about 3 to 5 weight% based on the coal. This coal carbonization gas contains volatile components in coal and low-molecular radicals of gaseous coal tar generated when a part of the coal polymer structure undergoes thermal decomposition. This coal carbonization gas is introduced into the liquid gas mixer 14 through the pipe 13.

On the other hand, the tank 15 stores hydrogenated tar kept at 80 ° C. This hydrogenated tar is sent to the liquid gas mixer 14 via the pipe 16 by the pump 17. The amount of hydrogenated tar was twice the amount of coal tar generated from coal during carbonization.

In the liquid-gas mixer 14, hydrogenated tar is atomized into coal carbonized gas at an internal temperature of 400 to 600 ° C., preferably 400 to 500 ° C. The amount of hydrogenated tar sprayed is 1 to 5 times, preferably 1 to 3 times the amount of coal tar generated from coal during carbonization. In the liquid-gas mixer 14, the low-molecular radicals generated in a gaseous state are hydrogenated and stabilized as a low-molecular compound by the hydrogen abstraction reaction from the hydrogenated tar to become a gaseous low-molecular compound.

These gaseous low molecular weight compounds and hydrogenated tar are introduced into the heat exchanger 19 via the pipe 18,
Here, cool to 80 ° C. After that, the liquid is sent to the gas-liquid separator 20 to separate the light coal tar and hydrogenated tar, which have become liquid, into gas components. The coal tar and the hydrogenated tar are discharged to the outside of the system via the pipe 22 and collected.

On the other hand, the gas component separated in the gas-liquid separator 20 is introduced into the heat exchanger 23 via the pipe 21 and further cooled to 25 ° C., and then, in the gas-liquid separator 24, it is light. Separate into liquid components and gas components such as hydrogen and methane. After this, the gas component passes through the pipe 25, while
The light liquid component is discharged to the outside of the system through the pipe 26.

As the hydrogenated tar used in the above-mentioned examples, oil obtained by hydrogenating coal tar obtained when lightening was not carried out by using an autoclave was used. The hydrogenation conditions in the autoclave are a reaction pressure of 30 atm, a reaction temperature of 390 ° C., and a reaction temperature holding time of 60 minutes using a commercially available nickel catalyst. Of the obtained hydrogenated tar, only the fraction having a boiling point of 200 to 400 ° C. was used as the hydrogenated tar sprayed in the liquid gas mixer 14.

FIG. 2 shows the distillation curve of the coal tar obtained when the hydrogenated tar was not sprayed and the lightening was not carried out in the above-mentioned embodiment, that is, the distillation curve sampled by the pipe 22.

On the other hand, FIG. 3 shows a distillation curve of coal tar obtained by spraying hydrogenated tar for lightening in this example. The distillation curve in FIG. 3 is obtained by subtracting the distillation fraction corresponding to the sprayed hydrogenated tar from the mixture of the lightened nascent coal tar and the sprayed hydrogenated tar sampled in the pipe 22. The effectiveness of the present invention can be measured by comparing with the coal tar distillation curve of the non-lightening treatment shown in 2.

As is clear from the comparison of the distillation curves of FIGS. 2 and 3, the light fraction of coal tar below 300 ° C. was obtained by the above-described coal tar reforming method of this example.
It was confirmed that lightening of coal tar was achieved, increasing from about 30% to about 45% of the total coal tar weight.

In addition, in Table 1 below, coal tar (A) generated by non-lightening treatment, sprayed hydrogenated tar (B), and a mixture of lightened coal tar generated and sprayed hydrogenated tar
(C), a mixture of lightened generated coal tar and sprayed hydrogenated tar, minus the distillation fraction equivalent to the sprayed hydrogenated tar (D). Show. Each weight in Table 1 is a value when the weight of the generated coal tar is 100 g.

[0026]

[Table 1]

As is apparent from Table 1, from a mixture of lightened nascent coal tar and atomized hydrogenated tar,
In the case where the distillation fraction equivalent to the sprayed hydrogenated tar was subtracted (D), the light fraction of coal tar at 300 ° C or less increased in comparison with the coal tar (A) that had undergone non-lightening treatment. Was. Similar results were obtained in coal tar reforming experiments using heavy oil with a boiling point fraction of 200 to 350 ° C of crude oil instead of hydrogenated tar.

[0028]

As described above, according to the method for reforming coal tar of the present invention, hydrogenated tar or heavy petroleum oil is added to an organic compound having a relatively low molecular radical state immediately after the coal carbonization process. Before spraying and condensing the low-molecular radicals to make them heavy, the hydrogen atoms in hydrogenated tar or petroleum heavy oil cause the low-molecular radicals to remain low-molecular in the high temperature atmosphere of coal carbonization gas. Stabilize hydrogenation. As a result, light coal tar can be obtained without providing a particularly severe high temperature and high pressure condition. Further, since it is not necessary to reheat the coal tar, the light fraction in the coal tar is not thermally decomposed by reheating and is not lost by gasification. As a result of these, coal tar rich in light fractions with less heavy fractions can be economically obtained.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of a processing apparatus used in the coal tar reforming method of the present invention.

[FIG. 2] As a comparative example, without spraying hydrogenated tar,
The characteristic view which shows the distillation curve of the obtained coal tar which did not implement lightening by the reforming method of the coal tar of this invention.

FIG. 3 is a characteristic diagram showing a distillation curve of coal tar obtained by the method for reforming coal tar of the present invention.

[Explanation of symbols]

10 ... Treatment device, 11 ... Dry distillation furnace, 12 ... Heating device, 1
3, 16, 18, 21, 21, 25, 26 ... Piping, 14 ... Liquid-gas mixer, 15 ... Tank, 17 ... Pump, 19, 23 ...
Heat exchanger, 20, 24 ... Gas-liquid separator.

Claims (1)

[Claims] 1. In the coal carbonization process, hydrogenated tar or petroleum-based heavy oil is sprayed and brought into contact with the coal carbonization gas immediately after being released from the coal during carbonization to obtain the coal contained in the coal carbonization gas. The low-molecular radicals of coal tar generated by thermal decomposition of the coal polymer structure of No. 2 are reacted with hydrogen atoms provided by the hydrogenated tar or the petroleum heavy oil to hydrogenate the low-molecular radicals. A method for reforming coal tar, which comprises stabilizing and stabilizing the coal tar.