JPH07166167A - Process for improving coal tar - Google Patents

Abstract

PURPOSE:To provide a process for reforming coal tar, capable of economically obtaining a coal tar rich in light distillation fractions under conditions comprising relatively low temperature and pressure and capable of recycling a part of the reformed coal tar to the coal tar. CONSTITUTION:A water-added tar 20 heated at 80-250 deg.C is sprayed in a coke oven gas in an upward flow pipe 12 just after generated in a coke oven 11 to utilize the sensible heat of the coke oven gas for subjecting low molecular radicals generated in a gaseous state at 350-600 deg.C to a reaction for pulling out hydrogen atoms from the water-added tar, thus hydrogenating and stabilizing the low molecular radicals in the state of the low molecules to produce gaseous low molecular compounds. The treated coke oven gas is cooled, transferred to a tar decanter 16 and subsequently separated into the reformed coal tar, an ammoniacal aqueous solution and a carbon gas therein. A part of the reformed coal tar is transferred into a water-adding plant 19 for the tar through a piping 18. In the water-adding plant 19 for the tar, the water is added to the reformed coal tar, and subsequently transferred to the upward flow pipe 12 through a piping 20 for recycling the tar as the water-added tar.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventionally, a coal tar component contained in a coke oven gas at 600 to 800 ° C. which is generated during coal carbonization in a coke oven is cooled to about 80 ° C. by a large amount of flushing with water in the coke oven rising pipe section, After condensing in mild water, it is collected in a tar decanter through a dry main pipe together with a large amount of mild water and coke oven gas.
Naphthalene and benzols that are separated into gas and liquid by a tar decanter and are entrained in the gas line are recovered in an absorption tower installed in the gas line after the decanter.
Coal tar in the decanter is gravity-separated from the water generated during the dry distillation of coal or coal, the solid content in the coal entrained in the coke oven gas, and collected in the tar tank. The cheap water is partly recycled and the surplus is treated in the water treatment facility.

About 70% of the coal tar generated in the coke oven of a steel mill is a heavy fraction having a boiling point of about 300 ° C. or higher, and about half of the heavy fraction is a high boiling fraction called medium pitch. In the generation process, at present, no operation such as special lightening and reforming is performed.

[0004] A reforming method for lowering the molecular weight of such a heavy fraction of coal tar to lighten it has been studied for many years. 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.24
9-256 (1988)).

Also, many studies have been made on a method for reducing the molecular weight of coal tar by reducing it 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.

[0006]

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. Such a process cannot be an economical practical process among the steel mill coke oven processes.

Further, due to the reaction under the conditions of high temperature and high pressure, the heavy fraction of coal tar is lightened, and at the same time, the light fraction of the coal tar is partially 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 it is possible to economically obtain coal tar rich in light distillates under relatively low pressure conditions, and to improve the reformed coal tar. Provided is a coal tar reforming process in which a part of the above can be recycled to reform the generated coal tar.

[0010]

The present invention is a coke oven,
The coke oven comprises a hydrogenated tar spraying unit for spraying hydrogenated tar on the coke oven gas immediately after being generated in the coke oven, and a hydrogenation treatment device for hydrogenating coal tar to produce the hydrogenated tar. The low-molecular radical of coal tar generated by thermal decomposition of the coal polymer structure in coal contained in gas is reacted with the hydrogen atom donated by the hydrogenated tar to hydrogenate the low-molecular radical. While stabilizing and obtaining a reformed coal tar rich in light fractions, a part of the reformed coal tar is hydrogenated into the hydrogenated tar by the hydrogenation treatment device, and the hydrogenated tar spraying section is used. Provided is a coal tar reforming process characterized in that the hydrogenated tar is sprayed onto the coke oven gas and is used for hydrogenation stabilization of the coal tar immediately after being generated from the coal. .

The coal tar reforming process of the present invention will be described in more detail below. The ratio of the number of hydrogen atoms to the number of carbon atoms in heavy oil is an index for measuring the degree of heavyness of coal tar, coal liquefied oil or heavy petroleum oil. For example, taking a naphthalene molecule as an example, its chemical formula is C ₁₀ H ₈
Therefore, the ratio of the number of hydrogen atoms to the number of carbon atoms H / C
Is 8/10 = 0.8, and in the anthracene molecule (chemical formula C ₁₄ H ₁₀ ), H / C is 10/14 = 0.714. In the coke raw material coal, the H / C is about 0.65 to 0.8 although it varies depending on the type of coal. In the coal carbonization process in the coke oven, almost all the hydrogen content in the coal is released from the raw material coal as the hydrogen content in the gas generated from the coke oven or the hydrogen content in the organic compound of coal tar. Inserted coal 1 as operating data of coke oven
Coke oven gas generated from 300 to 40 tons
It is about 0 Nm ³ , and the amount of coal tar generated is about 3 to 5% by weight with respect to the inserted coal. When calculated from the operation data of the coke plant, the amount of hydrogen gas contained in the coke oven generated gas immediately after leaving the coke oven is small, so the amount of hydrogen contained in the coal tar is small, and the average H / The value of C is H / C value of raw coal of 0.6 to 0.
It is almost the same as 8. That is, it is due to this low H / C that most of the coal tar is heavy. Therefore, hydrogen atoms are added to the generated coal tar to produce H / C.
By increasing the value, it becomes possible to stabilize the coal tar lightly.

In the coke oven of a steel mill, in the coal carbonization gas immediately after being discharged from coal, in addition to the volatile components in coal, low molecular weight coal coal molecules generated by thermal decomposition of the coal polymer structure are generated. There are radicals. The coal polymer structure refers to a structure in which structures having a condensed aromatic ring as a structural unit as a center are bonded to each other by methylene, ether, or the like, as shown in the Wiser coal model structure. This coal polymer structure has a high temperature (for example, 4
It is thermally decomposed at (00 to 1000 ° C.) to generate a gaseous low-molecular radical. When the temperature decreases, the 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 step, 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, immediately after the above-mentioned coal carbonization gas is released from the coal, that is, before the condensation of the low-molecular radicals at high temperature, the hydrogenation tar spraying section hydrogenates the coke oven gas. Spray and contact tar. Hydrogenated tar contains more hydrogen atoms than coal tar and has 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. .

Further, in the coal tar reforming process of the present invention, a part of the coal tar rich in the light fraction obtained as described above (hereinafter referred to as reformed coal tar) is subjected to hydrogenation treatment. It is hydrogenated and reused for hydrogenation stabilization of the above-mentioned low molecular radicals as hydrogenated tar.

[0015]

In the coal tar reforming process of the present invention, the hydrogenated tar is sprayed in the hydrogenated tar spraying section to the coke oven gas immediately after it is generated in the coke oven, and the low-molecular radicals in the coke oven gas are dry distilled. Under high temperature conditions due to sensible heat during processing,
By reacting with hydrogen atoms provided by hydrogenated tar to hydrogenate and stabilize it, low-molecular radicals are prevented from cooling and condensing with each other to form a heavy fraction of coal tar. In addition, since the coal tar is reacted in the nascent gas state, there is no need for a step of thermally decomposing coal tar, which has a large amount of heavy fractions, under high pressure and high temperature conditions, so the light fraction of coal tar is decomposed. It does not gasify. Further, the obtained modified coal tar is hydrogenated by a hydrogenation treatment device to be hydrogenated tar, which is used for hydrogenation stabilization of low-molecular radicals, so that the properties of the hydrogenated tar are stable.

[0016]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a schematic view showing an example of the coal tar reforming process of the present invention. In the figure, 11 is a coke oven. An ascending pipe section 12 for leading out the coke oven gas generated inside is connected to the top of the coke oven 11. A water tank 14 is connected to the rising pipe portion 12 via a pipe 13. The downstream end of the rising pipe portion 12 is connected to the dry main pipe 15. The downstream end of the dry main pipe 15 is connected to the tar dencanter 16. A pipe 17 for discharging reformed coal tar described later is connected to the tar decanter 16. A pipe 18 is branched and connected in the middle of the pipe 17. The downstream end of the pipe 18 is connected to the tar hydrogenation plant 19. A pipe 20 is connected to the discharge side of the tar hydrogenation plant 19, and its downstream end is connected to the rising pipe part 12.

On the other hand, a pipe 21 is connected to the gas discharge side of the tar decanter 16. The downstream end of the pipe 21 is connected to the gas treatment process 22. The discharge side of the gas treatment process 22 is connected to a gas holder 24 via a pipe 23. Pipes 26 and 27 for exchanging gas with a pressure swing gas separation plant (PSA) 25 are branched and connected to the pipe 23. The hydrogen gas discharge side of the PSA 25 is connected to the tar hydrogenation plant 19 via a pipe 28.

A pipe 29 is further connected to the tar decanter 16, and its downstream end is connected to the low water tank 14. In the coal tar reforming process 10 having such a configuration, the coal tar is reformed as follows.

First, the coke oven gas immediately after being generated in the coke oven 11 has a temperature of 650 to 700 ° C. and is generated by thermal decomposition of volatile components in coal and a part of the coal polymer structure. It contains low-molecular radicals of gaseous coal tar. Immediately after the generation, the coke oven gas is sprayed with hydrogenated tar 20 at 80 to 250 ° C., preferably 80 to 150 ° C. in the rising pipe section 12. As a result, the sensible heat of the coke oven gas is used, and the temperature is 350 to 600 ° C., preferably 4 to
In a high temperature atmosphere of 00 to 500 ° C., the low molecular weight radicals generated in a gaseous state are hydrogenated and stabilized as low molecular weight by the hydrogen abstraction reaction from the hydrogenated tar to be reformed coal tar.

Thereafter, in the ascending pipe 12, the coke oven gas is sprayed with the noble water from the noble water tank 14 through the pipe 13, and the coke oven gas, the obtained reformed coal tar, and the sprayed hydrogenated tar are about 80%. After cooling to ℃, it is sent to the tar decanter 16 through the dry main pipe 15 together with ammonium hydroxide. In the tar decanter 16, gas / liquid separation is performed, and it is separated into reformed coal tar, ammonium water, and C gas.

The reformed coal tar is fed through a pipe 17 to a tar.
Although it is recovered in a tank (not shown), a part of it is sent to the tar hydrogenation plant 19 through the pipe 18.
In the tar hydrogenation plant 19, the reformed coal tar is hydrogenated to be hydrogenated tar, sent to the ascending pipe section 12 via the pipe 20, and sprayed to the coke oven gas immediately after being generated from the coke oven 11 described above. It is recycled as tar.

The hydrogenation in the tar hydrogenation plant 19 does not have to be as severe as hydrocracking and lightening the coal tar, and the reaction pressure is 50 atm or less, preferably 15 to 40 atm, and the reaction temperature is 350 to 450 ° C. , Preferably 380-4
Mild hydrogenation at 20 ℃ is good. The hydrogenated tar thus hydrogenated may be wholly recycled or a specific distillation fraction, for example, a fraction having a boiling point of 200 to 400 ° C. may be separated and the fraction may be recycled.

On the other hand, the cheap water passes through the pipe 29 and the cheap water tank 1
Although it is recycled after being sent to No. 4, a part of the water is treated as waste water generated from the coke oven 11. The coke oven gas (C gas) from which coal tar and ammonium hydroxide have been separated is sent to a gas treatment process 22 via a pipe 21 where it is subjected to gas treatment such as naphthalene absorption, desulfurization, ammonia absorption, and benzol absorption. After piping 23
Are collected by the gas holder 24. However, a part of the C gas is sent to the pressure swing gas separation plant (PSA) 25 via the pipe 26 and used for hydrogen production. P
The hydrogen produced in SA25 is sent to the tar hydrogenation plant 19 through the pipe 28 and used for hydrogenating coal tar. The exhaust gas of the PSA 25 is returned to the pipe 23 by the pipe 27.

In order to confirm the effect of coal tar reforming in the coal tar reforming process 10 described above, tar reforming by spraying hydrogenated coal in a model 30 shown in FIG. 2 was tested. .

First, coal is loaded into the carbonization furnace 31, and the carbonization of the coal is carried out while controlling the temperature of the heating device 32 so that the furnace wall temperature of the carbonization furnace 31 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 is a gaseous co-gas generated by volatile components in coal and thermal decomposition of a part of the coal polymer structure.
Contains low molecular weight radicals of rutar. This coal carbonization gas is introduced into the liquid gas mixer 34 via the pipe 33.

On the other hand, the tank 35 stores hydrogenated tar kept at 80 ° C. This hydrogenated tar is sent by the pump 37 to the liquid gas mixer 34 via the pipe 36. The amount of hydrogenated tar was twice the amount of coal tar generated from coal during carbonization.

In the liquid-gas mixer 34, 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 34, the low-molecular radicals generated in a gaseous state are hydrogenated and stabilized as low-molecular weight by the hydrogen abstraction reaction from the hydrogenated tar to become reformed coal tar.

The gaseous low molecular weight compound and hydrogenated tar are introduced into the heat exchanger 39 through the pipe 38,
Here, cool to 80 ° C. Then, the liquid is sent to the gas-liquid separator 40, and the light coal tar and hydrogenated tar which have become liquid are separated into gas components. The coal tar and hydrogenated tar are discharged to the outside of the system via the pipe 42 and collected.

On the other hand, the gas component separated in the gas-liquid separator 40 is introduced into the heat exchanger 43 via the pipe 41 and further cooled to 25 ° C., and then in the gas-liquid separator 44, light Separate into liquid components and gas components such as hydrogen and methane. After this, the gas component passes through the pipe 45, while
The light liquid component is discharged to the outside of the system through the pipe 46.

As the hydrogenated tar used in the above-mentioned examples, oil obtained by hydrogenating coal tar obtained when no lightening was carried out 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 sprayed hydrogenated tar.

FIG. 3 shows a 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 of the sampled by the pipe 42.

On the other hand, FIG. 4 shows a distillation curve of coal tar obtained by spraying hydrogenated tar in the present example for lightening. The distillation curve in FIG. 4 is obtained by subtracting the distillation fraction corresponding to the sprayed hydrogenated tar from the mixture of the lightened generated coal tar and the sprayed hydrogenated tar sampled in the pipe 42. The effectiveness of the present invention can be measured by comparing with the coal tar distillation curve of the unreduced treatment shown in 3.

As is clear from the comparison of the distillation curves of FIGS. 3 and 4, 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, unburned coal tar (A), sprayed hydrogenated tar (B), a mixture of lightened coal tar 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.

[0035]

[Table 1]

As can be seen from Table 1, from the 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.

[0037]

As described above, in the coal tar reforming process of the present invention, hydrogenated tar is sprayed onto an organic compound having a relatively low molecular weight radical state immediately after being generated in a coke oven, and this low molecular weight is sprayed. Before the radicals are condensed and become heavy, the low-molecular radicals are hydrogen-stabilized in the high temperature atmosphere of the coal carbonization gas by the hydrogen atoms of the hydrogenated tar as low-molecular weight. 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. Further, a part of the obtained reformed coal tar is hydrogenated with a hydrogenation treatment device to obtain hydrogenated tar, which is recycled and sprayed on the coke oven gas, so a separate hydrogenated tar is prepared. No need. 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 coal tar reforming process of the present invention.

FIG. 2 is a schematic view showing a treatment model used in a test for confirming the effect of the coal tar reforming process of the present invention.

FIG. 3 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. 4 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 ... Coal tar reforming process, 11 ... Coke oven,
12 ... Ascending pipe section, 13, 17, 18, 20, 21, 21
3, 26, 27, 28, 29 ... Piping, 14 ... Low water tank, 15 ... Dry main piping, 16 ... Tar decanter, 19 ... Tar hydrogenation plant, 22 ... Gas treatment process, 24 ... Gas holder, 25 ... PSA .

Claims (1)

[Claims] 1. A coke oven, a hydrogenated tar spraying section for spraying hydrogenated tar to a coke oven gas immediately after being generated in the coke oven, and a hydrogenation treatment for hydrogenating coal tar to obtain the hydrogenated tar. A low-molecular radical of coal tar generated by thermal decomposition of a coal polymer structure in coal contained in the coke oven gas, which is provided with an apparatus, and is reacted with a hydrogen atom provided by the hydrogenated tar. And stabilize the low-molecular radicals by hydrogenation to obtain modified coal tar rich in light fractions,
With the hydrogenation treatment device, a part of the reformed coal tar is hydrogenated to the hydrogenated tar, and the hydrogenated tar is sprayed onto the coke oven gas by the hydrogenated tar spraying unit,
A coal tar reforming process, which is used for stabilizing the hydrogenation of coal tar immediately after it is generated from the coal.