JP2009298909A - Utilizing method of pyrolysis char as carbonaceous material for sintering - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To produce a carbonaceous material used in a sintering process in an iron producing process. <P>SOLUTION: Two-stage reactors of a lower gas stream layer gasification oven and an upper gas stream layer thermal decomposition oven are used. In the gasification oven, oxygen or oxygen and steam are charged together with coal, and gasified gas is generated by partial oxidation of the coal. In the thermal decomposition oven, coal is charged and the coal is thermally decomposed by sensible heat of the gasified gas moved from the gasification oven to generate pyrolysis char and thermal decomposed gas. The pyrolysis char is recovered and the recovered char is used as the carbonaceous material in a sintering raw material process in the iron producing process. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method of using char generated from a process of producing gas, tar and char by rapidly gasifying and pyrolyzing coal in an air flow layer in a sintering process in an iron making process.

In the steel manufacturing process, iron ore needs to be used as a sintered ore in the raw material sintering process in order to be used in a blast furnace. In the raw material sintering process, at present, in addition to powdered coke that is too small to be used in a blast furnace, carbon material supplemented with coal, etc., is added to iron ore to reduce the combustion heat of the carbon material. It has been baked and hardened.
It is generally known that nitrogen oxides are generated from the nitrogen content in the carbonaceous material during the combustion in the raw material sintering step, and as a result, nitrogen oxides are contained in the sintered exhaust gas. Since the concentration of nitrogen oxides in the exhaust gas is strictly regulated, anthracite coal with a low nitrogen content is used as a carbon material mixed with powdered coke or the like in order to suppress the generation of nitrogen oxides.
In addition, as another method for producing a carbon material in which powder coke is insufficient, a method by thermal decomposition of coal in a rotary kiln or a chamber furnace is known. Patent Document 1 and Patent Document 2 show a method for producing gas, tar (oil), and char by coal pyrolysis in an airflow layer. In this method, coal pyrolysis can be efficiently carried out by air-conveying coal as fine powder and mixing with high-temperature gas by coal gasification.

JP-A-5-295371 JP 2004-217868 A

Low nitrogen anthracite used for reducing nitrogen oxides in sintered exhaust gas has a limited production area even in the world and has recently become difficult to obtain.
Moreover, since the heating temperature of coal can only be raised to about 600 to 1100 ° C. by a method such as a rotary kiln or a chamber furnace, the amount of nitrogen in the obtained carbon material is hardly reduced compared to raw material coal, and low nitrogen anthracite coal. It cannot be used as an alternative.
In view of the above problems, an object of the present invention is to provide a novel sintering carbonaceous material that can be supplemented with an amount of powdered coke that is insufficient in the raw material sintering step. Moreover, it aims at providing the carbonaceous material for sintering which can substitute the low nitrogen anthracite which has been used conventionally but has become difficult to obtain.

In the sintering step in the iron making process, iron ore is mixed with carbonaceous material, the carbonaceous material is burned, and the iron ore is baked and solidified to produce sintered ore. It is generally known that so-called Fuel NOx derived from carbonaceous materials is mostly nitrogen oxide generated during carbonaceous material combustion in the sintering process. The simplest method for suppressing the generation of nitrogen oxides is to use a carbon material that does not contain nitrogen, but low nitrogen anthracite with a low nitrogen content has recently become difficult to obtain.
When a carbon material with a low nitrogen content cannot be secured, a large-scale denitration facility for removing nitrogen oxides from the sintered exhaust gas is required. In addition, in order to produce a carbon material having a low nitrogen content from coal, it is sufficient to treat the coal at a high temperature and denitrify it. However, there is no process for efficiently treating coal on an industrial scale. I didn't come.
As a result of intensive studies, the present inventors have found that it is possible to produce a carbonaceous material (char) from which nitrogen is efficiently removed together with volatile matter from coal by thermally decomposing the coal in an air flow layer. It was.

  As a method for producing carbonaceous material by gasifying and pyrolyzing coal in an air flow layer, for example, Patent Document 1 and Patent Document 2 describe, but the generated char may be input as a gasification raw material. Not only is it stated that nitrogen content can be effectively removed in the char that is produced, but it is not envisaged to produce carbonaceous materials in the sintering process, and appropriate conditions for that Not shown.

  According to the study by the present inventors, when the coal is gasified and pyrolyzed using a two-chamber, two-stage reactor in which the lower stage is a gasification furnace and the upper stage is a pyrolysis furnace, nitrogen components are efficiently removed from the coal, It was found that the nitrogen component is reduced in the solid char produced by pyrolysis. Furthermore, when the pyrolysis temperature exceeds a specific temperature, the ratio of nitrogen decreases to the same level as the nitrogen component ratio in the coke breeze, and when the pyrolysis pressure exceeds a specific pressure, it is approximately the same as the nitrogen component ratio of anthracite. It was found that the ratio of nitrogen was lowered until the invention was made.

The gist of the present invention is as follows.
(1) Using a two-stage reactor with two upper and lower chambers in which the lower stage is a gas-bed gasification furnace and the upper stage is a gas-flow bed pyrolysis furnace, in the gasification furnace, oxygen or oxygen and water vapor are introduced together with coal. Then, a gasified gas is generated by partial oxidation of the coal, and in the pyrolysis furnace, the coal is injected, and the coal is pyrolyzed by sensible heat of the gasified gas that has moved from the gasification furnace. The pyrolysis char is characterized in that the pyrolysis char and pyrolysis gas are generated, the pyrolysis char is recovered, and the recovered char is used as a carbon material in a sintering raw material process in the steel industry. Usage as a carbon material for sintering.
(2) The method of using the pyrolysis char as a sintering carbon material according to claim 1, wherein the temperature in the pyrolysis furnace is 1200 ° C or higher.
(3) The method for using the pyrolysis char as a sintering carbon material according to claim 2, wherein the pressure in the pyrolysis furnace is 2.0 MPa or more.

  By this invention, it becomes possible to reduce the nitrogen content in the carbonaceous material used for the raw material sintering step of the iron making process, and to suppress the generation of nitrogen oxides from the sintering step. Furthermore, it becomes possible to reduce a part or all of the anthracite which has become difficult to obtain in the sintering process.

  The coal pyrolysis apparatus used in the present invention is a two-chamber, two-stage reactor having a gasification furnace below and a pyrolysis furnace above. When coal is gasified using oxygen as a gasifying agent in a gasification furnace, a gasification gas mainly composed of carbon monoxide, carbon dioxide, hydrogen, and water vapor is generated. The temperature of the gasification furnace is not lower than its melting point because it is necessary to melt and discharge the ash contained in the coal to be gasified, and is generally about 1300 to 1600 ° C. The temperature of the gas leaving the gasification furnace is also the temperature. By mixing this gasification gas with coal and hydrogen as required in the pyrolysis furnace, the temperature of the coal is raised to cause a pyrolysis reaction to obtain a product. Is a pyrolysis method of coal using a two-stage reactor.

  Moreover, by using two chambers and two stages, it is possible to completely separate the part that performs coal gasification and the part that performs thermal decomposition, and it is possible to set the operating conditions of each part individually. Here, the two-chamber reactor is a reactor structure in which a constriction is placed between the gasification furnace and the pyrolysis furnace to partially increase the flow velocity, so that the coal particles and the like put into the upper chamber are lowered. A reactor that prevents falling into a chamber and allows independent reaction conditions to be set in each chamber.

The present invention will be described in detail below. FIG. 1 shows a schematic diagram of the method of the present invention. This apparatus mainly includes a pyrolysis furnace 1, a gasification furnace 2, and a throttle throat 3 that connects the two.
The raw material coal 17 is pulverized by the coal pulverization / supply device 11 and is air-flowed to the gasification furnace 2 and the pyrolysis furnace 1 by air-flow conveyance using nitrogen gas or the like.

In the gasification furnace 2, one or a plurality of gasification burners 5 for introducing the coal 9 for gasification together with the oxygen 12 or the oxygen 12 and the water vapor 13 are installed. In the gasification furnace 2, in order to convert as much carbon and hydrogen contained in the gasification coal 9 as possible into CO and H ₂ , the gasification coal 9, oxygen 12, and steam 13 are quickly mixed to form a gas. It is necessary to oxidize oxygen 12 and water vapor 13 before sooting the volatile matter generated from the chemical coal 9.
For this purpose, coal 9 for gasification into the gasification furnace 2, oxygen 12, and steam 13 are blown by the gasification burner 5 and rapidly mixed. The gasification gas 14 generated in the gasification furnace 2 passes through the throat 3 and is sent to the pyrolysis furnace 1. In the pyrolysis furnace 1, coal 10 for pyrolysis is introduced to cause a pyrolysis reaction. By this pyrolysis reaction, pyrolysis gas and solid pyrolysis char (also simply referred to as char) are generated from coal, and tar is obtained by cooling the pyrolysis gas. Pyrolysis gas and tar can be used as fuel and chemical feedstock.

  The temperature of the gasification furnace 2 is measured by a thermocouple 23 for gasification furnace temperature measurement installed on the gasification furnace ceiling, and the temperature of the pyrolysis furnace 1 is increased in the height direction on the side wall of the pyrolysis furnace 1. It measures with the thermocouple 24 for pyrolysis temperature measurement installed above the pyrolysis coal blowing nozzle 4, respectively.

  Since the ash contained in the coal 9 for gasification becomes a molten slag 15 at a high temperature of about 1500 ° C., the water tank 8 for collecting the slag tap 6 and the slag 15 so as to be discharged from the lower part of the gasification furnace 2. Is preferably provided. The slag 15 collected in the water tank 8 is solidified and discharged as a granulated slag 18.

  The char is obtained by solid-separating the pyrolysis gas and char 16 emitted from the pyrolysis furnace outlet 7 with the solid-gas separator 20. Examples of the form of the solid-gas separator 20 include a cyclo (registered trademark) and a filter. Since the recovered char is fine powder, it is granulated to an appropriate particle size by a granulator 21 such as a compression granulator, an extrusion granulator, or a rolling granulator, and sent to the sintering step 22.

  Solid char is mainly composed of carbon and a small amount of ash, and can be used as a carbonaceous material in the sintering process. In the sintering process, the carbonaceous material is mixed with iron ore, the carbonaceous material is burned by a sintering machine, and the sintered ore is produced by combustion heat.

  For the nitrogen contained in the char, by using a two-chamber, two-stage, gas-bed pyrolysis reaction, part of the char is gasified with steam from the gasifier in the pyrolysis furnace, so that the pyrolysis of the coal Since it progresses more, the nitrogen content decreases.

As for the temperature and pressure inside the pyrolysis furnace 1 and gasification furnace 2, the denitrification reaction is promoted and the nitrogen content is reduced to the level of the nitrogen content in the powder coke used in the conventional sintering process. In order to reduce the nitrogen content to the level of nitrogen content in the anthracite coal, the pressure is preferably 2.0 MPa or more. . The temperature of the pyrolysis furnace 1 is preferably below the melting point since slagging occurs above the melting point of the ash contained in the coal 9 for gasification, and the equipment cost increases as the pressure increases. About 3 MPa is more preferable.
The char produced by the above method is granulated to a particle size of 0.25 mm or more, preferably about 1 mm to 3 mm in diameter when used in the sintering step. A granulation method is not particularly specified, but there is a method using cement as a binder.
In general, the use of anthracite in the sintering process at steelworks is about 40% of the carbonaceous material used in the sintering process, which is about 100,000 tons / year. The amount of coal treated in the method of the present invention for producing char equivalent to the anthracite used is about 2000 tons / day.

(Example 1)
An example using the coal pyrolysis apparatus shown in FIG. 1 is shown below.
The gasification furnace was charged with 500 kg / h of coal pulverized to an average particle size of 30 μm by airflow conveyance, and gasification was performed using 350 Nm ³ / h oxygen and 50 kg / h water vapor. In the pyrolysis furnace, similarly pulverized coal was supplied at 130 kg / h by airflow conveyance. The pressure in the gasification furnace and the pyrolysis furnace was 2.5 MPa (absolute pressure). The gasifier temperature was 1550 ° C., the pyrolysis temperature in the pyrolysis furnace was 1220 ° C., and 1270 Nm ³ / h pyrolysis gas and 73 kg / h char were recovered.
The calorific value of the obtained gas is 2400 kcal / Nm ³ and can be used as fuel gas. The composition of coal used was C: 70% by mass, H: 5% by mass, and N: 1.7% by mass, whereas the composition of the obtained char was C: 76% by mass, H: 0.7%. % By mass, N: 0.35% by mass and char with a low nitrogen content. The analysis of coal, char, etc. is performed in accordance with JIS. For example, the total moisture is in JISM8812, elemental analysis (C, H, N) is in JISM8813, JISM8819, and elemental analysis (TS, S in ash). Was performed based on JISM8813.
FIG. 2 shows the mass ratio of char nitrogen and carbon generated by changing the temperature of the pyrolysis furnace by changing the amount of coal charged into the pyrolysis furnace by the same method. As the pyrolysis temperature increases, the ratio of nitrogen to carbon in the char decreases, reaching the level of fine coke at 1050 ° C and the level of low nitrogen anthracite at 1200 ° C.

(Example 2)
An example in which the pressure in the gasification furnace and the pyrolysis furnace is set to 0.3 MPa (absolute pressure) using the same apparatus as in Example 1 will be described.
The amount of coal in the gasifier is 500 kg / h, the amount of coal in the pyrolysis furnace is 70 kg / h, the amount of oxygen supplied in the gasifier is 370 Nm ³ / h, the amount of steam input is 50 kg / h, the gasification temperature is 1550 ° C, Operation was performed at a pyrolysis temperature of 1220 ° C., and pyrolysis gas 1140 Nm ³ / h and char 67 kg / h were recovered.
The calorific value of the obtained pyrolysis gas is 1820 kcal / Nm ³ and can be used as fuel gas. The composition of the coal used is the same as in the examples C: 70% by mass, H: 5% by mass, N: 1.7% by mass, and the composition of the obtained char is C: 75% by mass, H: 0.7% by mass. , N: 1.0% by mass and char with a low nitrogen content.
FIG. 2 shows the ratio of nitrogen and carbon of char produced by changing the temperature of the pyrolysis furnace by changing the amount of coal put into the pyrolysis furnace by the same method. As the pyrolysis temperature increases, the ratio of nitrogen to carbon in the char decreases.

(Comparative example)
FIG. 2 shows the ratio of nitrogen and carbon in char obtained by pyrolyzing the same coal as in the example using a rotary kiln. The thermal decomposition temperature is raised only up to 800 ° C due to equipment constraints. A decrease in N / C is observed with the pyrolysis temperature, but the decrease is small compared to the examples.

It is the schematic of the coal pyrolysis apparatus based on this invention. It is the figure which showed the change of N / C mass ratio in char when changing thermal decomposition temperature.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pyrolysis furnace 2 Gasification furnace 3 Throat 4 Pyrolysis coal injection nozzle 5 Gasification burner 6 Slag tap 7 Pyrolysis furnace exit 8 Water tank 9 Coal for gasification 10 Coal for pyrolysis 11 Coal grinding | pulverization and supply apparatus 12 Oxygen 13 Steam 14 Gasification Gas 15 Slag 16 Pyrolysis Gas, Char 17 Coal 18 Granulated Slag 19 Gas, Tar 20 Solid-gas Separator 21 Granulator 22 Sintering Process 23 Thermocouple for Gasification Temperature Measurement 24 Pyrolysis Temperature Measurement Thermocouple for

Claims (3)

Using a two-stage reactor with two upper and lower chambers in the lower part of the gas bed gasification furnace and the upper part of the gas bed pyrolysis furnace,
In the gasification furnace, together with coal, oxygen or oxygen and water vapor are input to generate gasified gas by partial oxidation of the coal. In the pyrolysis furnace, coal is input, and the coal is Pyrolysis is performed by sensible heat of the gasification gas that has moved from the gasification furnace to generate pyrolysis char and pyrolysis gas, and the pyrolysis char is recovered, and the recovered char is baked in the steel industry. A method of using pyrolytic char as a carbon material for sintering, characterized in that it is used as a carbon material in a sintering raw material process.   The method for using the pyrolysis char as a sintering carbon material according to claim 1, wherein the temperature in the pyrolysis furnace is 1200 ° C or higher.   The method for using the pyrolysis char as a sintering carbon material according to claim 2, wherein the pressure in the pyrolysis furnace is 2.0 MPa or more.

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