JPH01113491A - Manufacture of coal tar - Google Patents

Abstract

PURPOSE:To heat a powdered coal rapidly to thereby improve the production efficiency, etc., when coal tar is produced through thermal decomposition of a fluidized powdered coal in a reactor, by heating the decomposition gas and blowing the heated gas against the fluidized powdered coal in the reactor, thus accomplishing the reuse of the gas by circulation. CONSTITUTION:Raw coal 1 finely ground in a drying and grinding unit 2 is conveyed with a carrier gas 24 and blown through an injector 5 into a thermal decomposition reactor 6 for thermal decomposition. Coal char taken out of the reactor 6 is introduced into a vessel 14 and a cyclone 15, in order, for separation into a hot char 22 and a gas 25. Tar 21 is recovered from the gas 25. Then, through a circulating gas blower 18, part of the gas 25 is introduced as a carrier gas 24 into a coal feeder 4, and the remaining major part thereof is introduced into a recuperator 7 and a heat exchanger 8, in order, to be heated to a high temperature and is then blown against the fluidized powdered coal in the reactor 6 as a heated gas 10 for thermal decomposition of the powdered coal, thus accomplishing the reuse of the gas by circulation.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for producing coal tar, and more particularly to a coal rapid pyrolysis process for producing a large amount of coal tar, which is a raw material for coal chemistry.

Conventional technologyConventional 1 Coal tar is produced as a by-product of coke from coke ovens at a rate of 4 to 5% of coal.0 If coal tar is considered as the main product, current coke ovens The main component is coke, the tar production rate is low, and it is not necessarily the optimal thermal cracking process.

In order to effectively extract volatile matter from coal, it is desirable to realize thermal decomposition by rapid heating of the coal, and to suppress secondary reactions such as cracking fist carbon deposition from the generated volatile matter as much as possible. Mashi I/1゜Several processes have been developed for the purpose of mass production of coal tar, and the outline and problems of representative processes among these will be described below.

Figure 2 shows the COED process (Char-Oi 1-En
ergy-Development), (C1ean
fuels from coal symposium
.

P323. IGT, Chicago, 1975), this process was developed by FMC Corporation in the United States, and was tested on a 387/D scale in the early 1970s. It is operated using four fluidized beds to avoid coal agglomeration during the pyrolysis process. The respective pyrolysis temperatures are Stage I (31B'C), Stage I
t (454”O), m (537℃), IV (87
1'0), in stage (2), in order to supply the heat for pyrolysis, partial combustion of char is performed by 02, and the heated char is sent to the upstream fluidized bed, where it becomes the heat source necessary for the pyrolysis reaction. In order to avoid coal agglomeration, a multi-stage fluidized bed is required, and the supplied coal particle size is slightly large (-3am).
The bottleneck in this process is that the amount of tar produced is small at about 18% due to the long contact between the fluidized char and volatile components.

Figure 3 shows the ORC process (Occidental Re
5earchCorp, ), (Final report
on DOE contract, No.

EX-76-C-01-2244, 1979)
The air layer process being developed by the company - t'19? E
1-78 Ni 4T/D (7) PDU test was conducted. Heat is supplied by burning the generated char, separating it in a cyclone, and recycling the hot char to the reactor.The ratio of recycled char to coal must be at least 10:1.0 Coal tar generation The amount is very high, over 30%, and the process is promising, but the large amount of recycled char makes it difficult to operate.

Figure 4 shows the C31RO process (Oil fro layer coa
lbyflash pyrolysis and of
Grant Report, 1985), this process was developed in 1984-
Tests of 0.5↑/D have been conducted since 1985. It is a pyrolysis process with two fluidized beds, one in which the heat of pyrolysis is supplied by the combustion of char, and the other in which the pyrolysis reaction of coal takes place.

The fluidized bed is sand (1111Iφ), into which coal of 0.2mm diameter is fed, the amount of coal tar is quite large at 30%, and a large amount of hot solids can be smoothly moved between the two fluidized beds. Avoiding coal agglomeration will be an issue when increasing the size.

Problems to be Solved by the Invention Above, we have provided an overview of the processes that have been developed to date, but the technical challenges in realizing a commercially viable pyrolysis process that can produce coal tar in large quantities are ( 1) To achieve rapid heating of coal and to suppress secondary reactions of products; and (2) to avoid agglomeration during the thermal decomposition process of coal.

An object of the present invention is to provide a new method for producing coal tar that can solve the above technical problems in a method for producing coal tar by rapid pyrolysis of coal.

Means for Solving the Problems In order to achieve the above-mentioned objects, the present invention aims to recycle pyrolysis gas produced by pyrolysis of coal as gas for heating coal, and in addition to this, to It is characterized by shortening the residence time of substances in the reactor, and its gist is that in the method of manufacturing coal tar by thermal decomposition, powdered coal is continuously supplied to the reactor with an air flow. After heating the gas produced by pyrolysis of coal by indirectly exchanging heat with the combustion exhaust gas of low-calorie gas such as blast furnace gas or mixed gas, it is injected into the coal flow in the reactor and circulated as coal heating gas. A method for producing coal tar characterized by using the following method.

More specifically, the method for producing coal tar is characterized in that, in addition to the above method, the residence time of the thermal decomposition product in the reactor is set to 5 seconds or less.

The present invention will be explained below.

FIG. 1 shows an example of a process flow diagram of the present invention.

In this process, raw coal 1 is finely pulverized (-200 esh 8G%) in a coal drying and pulverizing equipment 2, and then passed through a coal feeder 4 to a carrier gas 24 with a solid-gas ratio (coal/carrier gas The pyrolysis reaction is completed in an instant by being conveyed in a state with a high ratio) and blown into the pyrolysis reactor 6 by the blowing nozzle 5, and rapidly heated by the high-temperature heated gas 10 blown through the blowing nozzle 5. The sensible heat of the solid-gas mixed phase flow containing char exiting from the reactor is recovered by the heat recovery device 7, and then the coal char is separated from the gas by the vessel 14° and the cyclone 15, and the hot char 22
is discharged from the system as

On the other hand, the tar-containing gas 25 separated from the char by the cyclone 15 passes through the scrubber 16 and the dust collector 17 to collect the tar 21, and the dust collector 41! l? A portion of the gas passes through the circulating gas blower 18 and is used as the carrier gas 24 of the coal feeder 4, and most of the remainder passes through the heat recovery device 7 and is recycled. Excess gas 2B generated by thermal decomposition and not recycled passes through gas purification equipment 19 and becomes high-calorie generated gas 20.

The present invention provides a thermal decomposition reactor 6 in such a process.
Accompanying this, a heat exchanger 8 and a combustor 9 for supplying high-temperature hot gas to this heat exchanger are provided, and the gas is sent by the above-mentioned circulating gas blower 18, and preheated (250℃) by the heat recovery device 7.
The pyrolysis gas 11 (~300°C) is indirectly heated to a high temperature via the heat exchanger 8, and then used as a heating gas for pyrolysis of coal and injected into the coal flow in the pyrolysis reactor 6. It is characterized by its recycled use.

Further, at this time, a feature is that a combustion exhaust gas 23 obtained by supplying a low calorie gas 13 such as blast furnace gas or mixed gas to the combustor 9 and burning it together with air 12 is used as a heat source to be supplied to the heat exchanger 8.

In addition to the above, another feature is that coal is blown into the reactor so that the residence time of the thermal decomposition products in the reactor is 5 seconds or less, and the coal is discharged outside the reactor.

The recycling gas mentioned above is heated to about 900℃ using a ceramic heat exchanger or a regenerative heat exchanger.The heated circulating gas is injected into the coal stream that has been conveyed, and instantly heats up. The pyrolysis reaction is completed. The reaction temperature of thermal decomposition is QQQ ~ TOO℃ 1 coal distillation time is about 5
less than seconds. The residence time (τ) mentioned here is 5
It is the reciprocal of pacevelocity (Sv), the reaction tube volume (m”) is V, and the recycle gas flow rate (
m″/S) as Qf, τ= 1/Sv =V/Q4
It is expressed as

The main technical challenges in realizing a process for producing large amounts of working coal tar are (1) achieving rapid heating of coal and suppressing secondary reactions of the product, (2) thermal decomposition of coal. As mentioned above, the purpose is to avoid agglomeration during the process.

In the coal pyrolysis process of the present invention, the pyrolysis gas is recycled and used as the heating gas for coal pyrolysis and injected into one coal stream, thereby increasing the heating rate of the coal to 104~b and further increasing the heating rate of the pyrolysis products. By suppressing the residence time in the reactor to 5 seconds or less, secondary reactions of the product are reduced and the production rate of coal tar is increased.

Furthermore, by providing a structure in which the coal is dispersed before it softens and melts using a nozzle that blows a coal flow entrained by a carrier gas and a heated recycle gas, it becomes possible to thermally decompose highly caking coal.

EXAMPLE Table 1 presents experimental results for pyrolysis using the process of the present invention for various coal types on a coal l T/H dry basis.

For example, the amount of coal tar produced is Example No.

4 (WANOQAN coal) and 1 coal (Ash Fr@e
Base) will be 30%. The calorific value of the generated gas varies depending on the type of coal, but is 5000 to 7000 Kcal/Nm3
and high calorie gas is obtained. Furthermore, in all of these examples, there was no agglomeration during the thermal decomposition process of coal, and the operation was carried out without any problems.

(The following is a blank space) Effects of the Invention When the gaseous bed pyrolysis process of the present invention is carried out, the following effects are obtained.

(1) Coal is dilutely dispersed in the airflow and rapid heating is possible (extraction amount of 104-b increases).

(2) Even highly caking coal can be used without agglomeration.

(3) Suitable for upsizing.

(4) Operation is easy as there is no circular handling of hot solids.

(5) By using high-calorie pyrolysis gas as recycled heating gas, pyrolysis gas with high added value can be obtained.

Therefore, it is an extremely useful invention industrially.

[Brief explanation of the drawing]

FIG. 1 shows a block flow diagram of the process of the present invention. FIG. 2 shows a flow diagram of the conventional technique (COEDORC process). FIG. 3 shows a flow diagram of the conventional technique (ORC process). FIG. 4 shows a flow diagram of the conventional technique (C3IRQ process).

Claims (2)

[Claims] (1) In a method of producing coal tar by pyrolysis by continuously supplying powdered coal to a reactor together with an air stream, the gas produced by pyrolysis of coal is heated and then injected into the coal stream in the reactor. A method for producing coal tar, characterized in that it is recycled and used. (2) The method according to claim 1, wherein the residence time of the thermal decomposition product in the reactor is 5 seconds or less.