JP4842410B2 - Method for producing solid fuel for sintering, solid fuel for sintering, and method for producing sintered ore using the same - Google Patents

Description

The present invention relates to a method for producing a solid fuel for sintering used as a heat source when producing a sintered ore for a steelmaking raw material, a solid fuel for sintering, and a method for producing a sintered ore using the same.
This application claims priority on March 19, 2010 based on Japanese Patent Application No. 2010-64207 for which it applied to Japan, and uses the content here.

  In general manufacturing processes for producing sintered ore for iron making raw materials, solid materials such as powdered coke and anthracite as a heat source are used for iron-containing raw materials such as powdered iron ore, secondary raw materials such as limestone, and sintered ore. Sintered raw material with added fuel is used. After this raw material is charged on a sintering pallet that rotates endlessly in, for example, a Dwydroid-type sintering machine, a raw material packed layer is generated, and then the solid fuel in the surface layer portion of the raw material packed layer is formed in an ignition furnace. Ignite. Then, the sintered cake obtained by sucking air from the suction part (wind box) at the bottom of the sintering pallet to move the combustion point from the upper side to the lower side of the raw material packed bed and continuously proceeding the sintering reaction Is smashed to produce a sintered ore with a predetermined particle size.

  At this time, as a solid fuel for sintering, a fine coke which is secondarily generated when producing coke for blast furnace and cannot be charged into the blast furnace because the particle size is too small has a particle size of 5 mm or less. Crushed and prepared powder coke is used.

  Further, as a solid fuel for sintering that compensates for the shortage of the amount of powder coke generated, coal with low volatile content such as anthracite is crushed and prepared in the same manner as powder coke and then widely used in the sintering process.

  For powder coke used as a solid fuel for sintering, the amount of coke inventories varies greatly depending on the balance between the amount of coke produced in the coke oven and the amount of coke not used in the blast furnace. There is. At the time of increased production of pig iron in the blast furnace, the amount of coke used for the blast furnace increases, so there is not enough powder coke that can be used as a solid fuel for sintering.

  As for anthracite used as a solid fuel for sintering, anthracite is an imported product from overseas and at the same time the resource country of anthracite is limited.

  Therefore, it is important to expand the choices of fuels that can be used other than powdered coke and anthracite that have been mainly used as solid fuels for sintering.

  As a substitute fuel for coke breeze and anthracite, tar and pitch, which are secondarily produced in a coke oven, are blended into the sintering raw material, so that a large amount of volatile matter is generated and these volatile matter is not used as a heat source. Since it is mixed in the exhaust gas, there is a risk of causing problems such as oil condensation in the dust collector and lowering of dust collection efficiency.

  Moreover, although lignite and subbituminous coal are cheap coal, since the volatile matter is high, when using brown coal and subbituminous coal as a solid fuel for sintering as it is, the same problem as the above arises.

  Therefore, as a means for solving the problems related to the volatile matter, a technique is disclosed in which char obtained by pyrolyzing coal in a temperature range of 300 to 900 ° C. is used as a solid fuel for sintering (patent). Reference 1).

Japanese Patent Laid-Open No. 5-255858

  However, when using coal char as a solid fuel for sintering, the following problems have been pointed out.

  The problem is that a large amount of powder is mixed in the coal char. When coal char is produced by heat-distilling coal with a high water content, such as brown coal or sub-bituminous coal, the particle size is reduced by the carbonization of coal powder contained in the coal and the pulverization of some coal in the process of heat-distillation. A char with a high content of fine particles less than 250 μm is produced. When producing sintered ore using a sintering raw material containing coal char with a high content of fine particles as a solid fuel, the burning rate of the fine particles in the solid fuel is too high. It burns in the process and does not contribute to combustion in the high temperature region required for the sintering reaction. Further, when the fine powder particles in the solid fuel increase, the air permeability in the sintered packed bed is lowered, so that the progress of the sintering reaction is hindered and the productivity is deteriorated.

  As a method for solving such problems caused by fine particles, it is conceivable to remove fine particles having a particle size of less than 250 μm in the coal char by sieving after the production of the coal char. However, in general, it is difficult to separate fine particles having a particle size of less than 250 μm by sieving, and when processing a large amount of coal char, work efficiency and productivity are likely to be reduced due to occurrence of clogging of the sieve. There is a problem in practical use. In addition, fine powder particles having a particle size of less than 250 μm separated and recovered by this method have low utility value as they are, and it is necessary to perform environmental preservation treatment such as dust generation measures when storing and transporting them.

  The present invention has been made in view of the above-mentioned present situation. In the present invention, in the manufacturing process of char used as a solid fuel for sintering, fine powder particles having a particle size of less than 250 μm are removed by combustion, thereby improving the sintering air permeability. The hindered fine powder particles are reduced, the particle size distribution of the product char is improved, and the productivity of the sintered ore in the sinter manufacturing process is improved. That is, the present invention provides a solid fuel for sintering, a method for producing a solid fuel for sintering, and a solid fuel for sintering, in which the ratio of fine powder particles having a particle size of less than 250 μm is significantly reduced.

  The inventors changed the type and particle size of coal, made a prototype of a char using a reactor such as a test carbonization furnace or a rotary kiln, performed sintering using these prototype char as a solid fuel for sintering, Research and development on flammability has been promoted. Among them, the present inventors pay attention to the fact that the particle size distribution of char before carbonization in char production and the particle size distribution of char that changes depending on the operating conditions of the rotary kiln affect the combustibility and sinterability in the sintering process. As a result, the present inventors have found conditions for a solid fuel that can greatly improve combustibility and sinterability.

This invention is made | formed based on the above knowledge, and is comprised as follows.
(1) In the method for producing a solid fuel for sintering according to the first aspect of the present invention, char is used as a solid fuel for sintering by heat-drying coal in a temperature range of 300 to 1150 ° C. with a rotary kiln. A method for producing a solid fuel for sintering, wherein the amount of theoretical combustion air necessary for combustion of fuel and the combustion of fine particles having a particle diameter of less than 250 μm generated from the coal are obtained from the product discharge side of the rotary kiln. Air and fuel are supplied in an amount in the range of 90 to 110% of the total theoretical combustion air amount required, and the fine particles having a particle size of less than 250 μm generated from the coal in the rotary kiln are removed by combustion. Then, the coal is carbonized.
(2) In the method for producing a solid fuel for sintering according to the second aspect of the present invention, char is used as a solid fuel for sintering by heat-drying coal in a temperature range of 300 to 1150 ° C. with a rotary kiln. 90% to 110% of the theoretical amount of combustion air required for combustion of fine particles having a particle size of less than 250 μm generated from the coal from the product discharge side of the rotary kiln. An amount of air within a range is supplied, the fine particles having a particle size of less than 250 μm generated from the coal in the rotary kiln are removed by combustion, and the coal is dry-distilled.
(3) In the method for producing high-strength coke according to (1) or (2) above, the content of fine particles having a particle size of less than 250 μm in the char discharged as a product from the product discharge side of the rotary kiln is determined. You may adjust to less than 10 mass%.
(4) The solid fuel for sintering according to one aspect of the present invention is manufactured by the method for manufacturing a solid fuel for sintering according to the above (1) or (2).
(5) In the manufacturing method of the sintered ore which concerns on 1 aspect of this invention, the solid fuel for sintering as described in said (4) is mix | blended in a sintering raw material.

  According to the method for producing a solid fuel for sintering according to the first aspect or the second aspect of the present invention, fine powder particles having a particle diameter of less than 250 μm in the product char can be removed by combustion. A solid fuel for sintering excellent in combustibility and breathability can be produced.

  According to the method for producing a sintered ore according to the first aspect or the second aspect of the present invention, the sintering reaction zone is sufficient by using the sintering raw material blended with the solid fuel for sintering. Since the solid fuel for sintering can be burned to a high temperature and the air permeability of the entire sintered layer can be improved, a sintered ore of good quality can be produced efficiently.

It is a mimetic diagram explaining dry distillation of coal and combustion of fine particles in char manufacture by a rotary kiln concerning one embodiment of the present invention. It is a schematic block diagram of the manufacturing apparatus of the solid fuel for sintering containing the rotary kiln which can implement effectively the manufacturing method of the solid fuel for sintering of this embodiment.

  Hereinafter, a method for producing a solid fuel for sintering according to an embodiment of the present invention will be described with reference to the drawings.

  As a coal carbonization facility, a chamber coke oven, a rotary kiln, a fluidized bed, or the like is used. In the method for manufacturing a solid fuel for sintering according to this embodiment, a rotary kiln is used for the following reason.

  A rotary kiln is advantageous in terms of char productivity because it has a higher heat transfer rate than a chamber coke oven and can relatively increase the rate of carbonization when carbonizing powdered coal.

  The fluidized bed has a faster carbonization rate than a rotary kiln. However, in the fluidized bed, particles of coal and char collide violently, so that the amount of fine particles generated increases compared to a rotary kiln. Therefore, in this embodiment, a rotary kiln is used as a production facility for a solid fuel for sintering. The rotary kiln is divided into an internal combustion rotary kiln that heats the raw material by heat exchange by bringing the raw material and heated combustion gas into contact, and an external combustion rotary kiln that heats the raw material from the outside of the raw material without directly contacting the raw material and the heating medium. Divided. In this embodiment, both an internal combustion type rotary kiln and an external combustion type rotary kiln can be applied.

  In this embodiment, powder coal as a raw material is charged from a raw material charging side (coal charging port) at one end of an internal combustion rotary kiln that is in a sealed state, and the powdered coal is heated and dry distilled while rolling in the rotary kiln. The char that is the product is discharged from the product discharge side at the other end of the product. At that time, fuel such as heavy oil or natural gas is supplied together with combustion air from the product discharge side of the rotary kiln to the raw material input side, and the raw material is heated by burning the fuel in the rotary kiln.

  This embodiment is characterized by a method of supplying air to the rotary kiln. That is, in the case of using an internal combustion type rotary kiln, in addition to the theoretical amount of combustion air necessary for the combustion of fuel supplied to the rotary kiln, in order to burn fine powder particles having a particle diameter of less than 250 μm generated from coal in the rotary kiln. Supply a sufficient amount of air.

  In FIG. 1, the schematic diagram explaining the dry distillation of coal in the char manufacture by the rotary kiln of this embodiment and the combustion of a fine particle is shown.

  In the present embodiment, by adjusting the amount of air supplied to the rotary kiln, as shown in FIG. 1, in the internal combustion rotary kiln, a “fuel combustion zone”, a “coal dry distillation zone”, and a “fine particle combustion zone” Can be formed. In the “fuel combustion zone”, the fuel is combusted by oxygen in the air, and in the “coal dry distillation zone”, the coal is carbonized by the air heated by the combustion. The “fine particle combustion zone” is formed between the “fuel combustion zone” and the “coal dry distillation zone”, and fine particles having a particle diameter of less than 250 μm generated by heating and dry distillation of coal burn.

  In normal rotary kiln operation, in order to prevent the generation of soot from fuel, the amount of supplied air is adjusted so that the air ratio is about 1.2 to 1.4 times the theoretical amount of combustion air necessary for fuel combustion. adjust. This adjustment of the air amount can suppress soot generation in the fuel combustion zone, but burns fine powder particles having a particle size of less than 250 μm generated by heating and dry distillation of coal and removing them from the char discharged as a product. It is not possible.

  In the present embodiment, in order to remove fine particles having a particle size of less than 250 μm generated up to the coal carbonization zone in the rotary kiln by combustion, a theoretical combustion air amount necessary for the combustion of fuel and a particle size of 250 μm generated from coal are used. An amount of air in the range of 90 to 110% of the total amount (hereinafter also referred to as a target value) required for the combustion of less than fine particles is supplied. Here, the amount of air to be supplied does not necessarily have to be the same amount as the target value (100% of the target value) because the combustion characteristics differ for each carbonaceous material, and the air amount of 90 to 110% of the target value. Is preferably prepared. When the air amount is less than 90% of the target value, powder less than 250 μm tends to remain due to insufficient combustion. On the other hand, when the amount of air is 110% or more of the target value, combustion of particles of 250 μm or more occurs, so that the yield and particle size of the product char are lowered.

Here, the theoretical air amount Ao (Nm ³ / hr) necessary for fuel combustion and the theoretical combustion air amount Aoc (Nm ³ / hr) necessary for combustion of fine particles having a particle diameter of less than 250 μm generated from coal are: Is defined as follows.

Ao = (1 / 0.21). {(22.4 / 12) .C + (11.2 / 2). (H-OX / 8) + (22.4 / 32) .S} (...) 1)
Here, Ao: theoretical amount of combustion air necessary for fuel combustion (Nm ³ / hr), C: amount of carbon atoms in fuel (kg / hr), H: amount of hydrogen atoms in fuel (kg / hr), OX: The amount of oxygen atoms in the fuel (kg / hr), S: the amount of sulfur atoms in the fuel (kg / hr).

Aoc = (1 / 0.21). {(22.4 / 12) .Cc + (11.2 / 2). (Hc-OXc / 8) + (22.4 / 32) .Sc}. (2)
Here, Aoc: theoretical combustion air amount necessary for combustion of fine particles having a particle size of less than 250 μm (Nm ³ / hr), Cc: carbon atom amount (kg / hr) in fine particles having a particle size of less than 250 μm, Hc: particles Hydrogen atom amount (kg / hr) in fine particles having a diameter of less than 250 μm, OXc: oxygen atom amount (kg / hr) in fine particles having a particle size of less than 250 μm, Sc: sulfur atom amount in fine particles having a particle size of less than 250 μm (kg) / Hr).

In the present embodiment, in the internal combustion rotary kiln, the combustion of fine powder particles having a theoretical combustion air amount Ao (Nm ³ / hr) necessary for fuel combustion and a particle size of less than 250 μm is performed using the equations (1) and (2). The theoretical amount of combustion air Aoc (Nm ³ / hr) required for each is calculated, and the total amount A (= Ao + Aoc) (Nm ³ / hr) is determined as the target value of the amount of air supplied into the rotary kiln.

As a modification of the present embodiment, when an external combustion type rotary kiln is used, the theoretical combustion air amount Aoc (Nm ³ / hr) required for combustion of fine particles having a particle size of less than 250 μm is obtained using the equation (2). ) And determine this as the target value for the amount of air supplied into the rotary kiln. That is, in this case, an amount of air in the range of 90 to 110% of the theoretical amount of combustion air necessary for burning fine particles having a particle size of less than 250 μm is supplied.

  In the present embodiment, the air ratio m defined by the following equation (3) is 1.0.

m = A / Ao (3)
Here, m is the air ratio (−).
Further, in the formulas (1) and (2), the carbon atom amount C (kg / hr), the hydrogen atom amount H (kg / hr), the oxygen atom amount OX (kg / hr), and the sulfur atom amount S (kg / hr) in the fuel hr), and the carbon atom weight Cc (kg / hr), the hydrogen atom weight Hc (kg / hr), the oxygen atom weight OXc (kg / hr), and the sulfur atom weight Sc (kg / hr) of the fine particles having a particle size of less than 250 μm Can be measured by conducting a batch carbonization test in advance and conducting chemical analysis of coal and char fine particles.

  Further, according to the study by the present inventors, in coal having a particle size of less than 500 μm, the moisture and volatile components contained in the coal are released in the drying process by heating in the rotary kiln, and the volume is reduced. As a result of densification of the solid structure due to re-solidification after melt softening and release of volatile matter, it has been confirmed that almost all coal having a particle size of less than 500 μm becomes fine particles having a particle size of less than 250 μm. Therefore, when a batch dry distillation test is performed in advance and chemical analysis of char fine particles is performed, the dry distillation test can be performed using coal particles having a particle size of less than 500 μm. In the dry distillation test, the ratio of fine particles having a particle size of less than 250 μm in char obtained in the dry distillation test can be estimated from the ratio of coal particles having a particle size of less than 500 μm in the coal raw material.

  In the present embodiment, the fine powder particles of the char that have passed through the dry distillation zone in the rotary kiln float due to the rolling operation, and therefore the fine powder particles can be effectively burned and removed in the fine powder combustion zone. Therefore, the content rate of fine powder particles having a particle size of less than 250 μm in the product char can be reduced to less than 10 mass%.

  The temperature in the rotary kiln rises from the raw material input side toward the product discharge side to form a temperature distribution. Further, the composition of gas generated from coal differs depending on the thermal decomposition temperature of the components in the coal, and tar components are mainly generated at low temperatures of about 300 to 400 ° C, and methane and ethane are used at 400 to 650 ° C. Hydrocarbon gas is generated, and hydrogen is generated at 650 to 850 ° C.

  Combustible substances such as volatile matter (VM) generated by heating (pyrolysis) of these coals are mainly generated in the range from the raw material input side of the rotary kiln to the dry distillation zone in the center, and supplied from the product discharge side. It moves to the raw material input side and is discharged together with the combustion gas heated by the combustion of the produced fuel. In the present embodiment, fuel is supplied from the product discharge side of the rotary kiln and air having a theoretical combustion air amount necessary for combustion of fine particles having a particle diameter of less than 250 μm generated up to the fuel and the coal carbonization zone is supplied. Therefore, oxygen in the supplied air is consumed in the fuel combustion zone and the fine particle combustion zone of the rotary kiln. Therefore, it is possible to recover and use the VM generated in the coal dry distillation zone and the coal dry zone together with the combustion gas without consuming it by combustion, and only the fine particles in the product char generated by heating (drying and dry distillation) are effective. It can be removed by combustion. Moreover, the heat | fever required for dry distillation can also be supplied in a rotary kiln by combustion of a fine powder particle.

  In this embodiment, the temperature rises from the raw material input side in the rotary kiln toward the product discharge side, and the temperature in the rotary kiln is preferably in the range of 300 to 1150 ° C. The lower limit temperature (300 ° C.) in the above temperature range corresponds to the lower limit temperature on the raw material input side. At a temperature lower than the lower limit temperature, the carbonization of coal hardly occurs, so that the carbonization efficiency of coal is lowered. The upper limit temperature (1150 ° C.) in the above temperature range corresponds to the upper limit temperature on the product discharge side. At a temperature higher than the upper limit temperature, the fuel and air supply nozzles are likely to be deformed, and the facility management is very difficult.

  FIG. 2 is a schematic configuration diagram of an apparatus for producing a solid fuel for sintering including a rotary kiln that can effectively carry out the method for producing a solid fuel for sintering according to the present embodiment.

  Coal which is the raw material of the product char used as the solid fuel for sintering is cut out from the coal hopper 1 via the cutting conveyor 2 and is put into the rotary kiln 4 from the coal charging port 3 provided on one end side of the rotary kiln 4. Supplied. Coal supplied into the rotary kiln 4 is dry-distilled by heating in a reducing atmosphere while moving gradually while rolling to the other end side (product discharge side) of the rotary kiln 4 as the rotary kiln 4 rotates. The The char 9 that has been subjected to dry distillation is discharged out of the system (rotary kiln 4) through a cooling device 7 such as watering and a discharge conveyor 8.

  In the present embodiment, a fuel supply burner 5 that supplies fuel toward one end (raw material input side) of the rotary kiln 4 so as to penetrate the end wall of the other end (product discharge side) of the rotary kiln 4 is provided inside the rotary kiln 4. Then, a predetermined amount of air is supplied from the air compressor 6 to the fuel supply burner 5. Fuel such as heavy oil or natural gas supplied from the fuel supply burner 5 provided on the product discharge side of the rotary kiln 4 toward the raw material input side is simultaneously burned by oxygen in the air supplied from the product discharge side, and the combustion The combustion gas heated by the heat moves to the raw material input side.

  On the other hand, coal is supplied from the other end side (raw material input side) of the rotary kiln 4 and is heated by heat exchange with the combustion gas while moving in the direction opposite to the direction of movement of the combustion gas. As a result, the temperature in the rotary kiln 4 rises from the raw material input side toward the product discharge side, and this temperature distribution causes the coal drying zone, coal dry distillation zone, fine powder particles from the raw material input side to the product discharge side in the rotary kiln 4. A combustion zone is formed sequentially.

  In the fine particle combustion zone formed on the product discharge side of the rotary kiln 4 after the fuel supplied from the fuel supply burner 5 is combusted by oxygen in the air, the fine powder particles less than 250 μm mainly generated in the dry distillation zone are in the rotary kiln. So that it is swollen and effectively burned and removed by surplus oxygen in the supply air.

  The combustion gas from the other end side (product discharge side) in the rotary kiln 4 toward the one end side (raw material input side) is discharged out of the rotary kiln 4 as exhaust gas (kiln exhaust gas) after heat exchange with coal. An exhaust gas combustion furnace 10 is connected to one end side (raw material input side) of the rotary kiln 4, and the exhaust gas is sucked in the exhaust gas combustion furnace 10.

  In this embodiment, most of the fine particles having a particle size of less than 250 μm generated mainly in the carbonization zone are generated from coal particles having a particle size of less than 500 μm in the raw coal, and therefore the theoretical combustion air amount necessary for the combustion of the coal The amount of air substantially corresponding to the total amount of the theoretical combustion air required for combustion of the supplied fuel (90 to 110% of the total amount) was supplied into the rotary kiln. The ratio of coal particles having a particle size of less than 500 μm in ordinary raw coal varies greatly depending on the coal type and particle size, but when the raw coal is pulverized and adjusted to a particle size of less than 30 mm suitable for dry distillation in a rotary kiln, It is about mass%.

  Therefore, in this embodiment, by setting the amount of air supplied into the rotary kiln as described above, fine particles having a particle size of less than 250 μm generated in the rotary kiln 4 are efficiently burned in the fine particle combustion zone. The content rate of fine powder particles having a particle size of less than 250 μm in the product char on the product discharge side is reduced to less than 10% by mass.

  The combustion exhaust gas containing the gaseous product and powder discharged toward the exhaust gas combustion furnace 10 may be discharged out of the system via a gas cleaning facility such as the exhaust gas combustion furnace 10 and the dust collector 11. From an economical point of view, a waste heat recovery boiler 12 may be installed to perform sensible heat recovery of exhaust gas, and exhaust gas may be discharged through a stack (chimney) 13. Further, from the viewpoint of downsizing the facility, this combustible gas may be supplied to the gas consuming facility as it is without burning the combustible gas containing volatile components in the exhaust gas combustion furnace 10.

  In the present embodiment, the particle size of coal, which is a raw material of the solid fuel for sintering supplied from the coal hopper 1 into the rotary kiln 4, is adjusted in advance, and coarse masses of 15 mm or more in the product char are 20% by mass. It is preferable to make it less than. Thereby, the solid solid fuel does not segregate in the lowest layer of the sintered layer in the sintering step, and the sintering reaction can be efficiently performed in all of the raw material packed layers.

  In this embodiment, although the example which used the internal combustion type rotary kiln was shown, the external combustion type rotary kiln can also be used as a modification of this embodiment. In this external combustion type rotary kiln, the rotary kiln can be heated from the outside by a gas burner. In this case, the fuel supply burner 5 for supplying fuel into the rotary kiln does not supply any fuel, and the theory necessary for burning fine powder particles having a particle size of less than 250 μm generated mainly in the dry distillation zone in the rotary kiln 4. Only air of approximately the same amount as the air amount (90 to 110% of the theoretical air amount) is supplied. Thus, in the external combustion type rotary kiln, it is only necessary to change at least the amount of air supplied into the rotary kiln among the conditions of the above embodiment using the internal combustion type rotary kiln.

  In the present embodiment, for example, subbituminous coal prepared to have a particle size of 0 to 30 mm by coarse pulverization is supplied as raw coal to the rotary kiln. For example, the ratio of coal particles having a particle size of less than 500 μm in the raw coal is about 15% by mass. When this raw coal is put into a rotary kiln with a waste heat recovery boiler shown in FIG. 2 and subjected to combustion treatment by dry distillation and predetermined air supply, the particle size in the product char immediately after being discharged from the product discharge side of the rotary kiln is less than 250 μm The proportion of fine powder particles is, for example, less than 1% by mass.

  An embodiment of a production process for producing an iron ore sintered ore using the solid fuel for sintering produced by the production method of the above embodiment as a raw material for sintering will be briefly described below.

  A sintering material obtained by adding the solid fuel for sintering shown in the above embodiment as a heat source to an iron-containing raw material such as powdered iron ore, a secondary raw material such as limestone, and sintered ore is used as a heat source. The raw material packed bed is generated by continuously charging the endlessly rotating sintering pallet. After that, the solid fuel in the surface layer part of the raw material packed bed is ignited in an ignition furnace, and air is sucked from the suction part (wind box) below the sintering pallet to move the combustion point from the upper side to the lower side of the raw material packed bed. The sintering reaction is continuously performed to obtain a sintered cake. When the sintering pallet is rotated at the discharge portion of the sintering machine strand, the sintered cake is cracked to an appropriate size and crushed while falling downward by its own weight to produce a sintered ore having a predetermined particle size.

  In the manufacturing method of the sintered ore of this embodiment, since solid fuel obtained by dry distillation of coal at a temperature of 300 to 1150 ° C. is used, generation of tar, hydrocarbon gas and NOx is small during the sintering process. In addition, since there are few fine particles having a particle diameter of less than 250 μm that impede sintering air permeability, it is possible to perform a stable sintering operation excellent in productivity and product quality of sintered ore.

  Therefore, problems such as oil condensation in the dust collector and a decrease in dust collection efficiency can be prevented, and the exhaust gas treatment equipment such as NOx can be made small. In addition, the production efficiency of sintered ore can be increased to cope with increased production.

  In addition, since no lump inclusions are mixed in the solid fuel for sintering, lump solid fuel does not segregate in the lowest layer of the sintered layer in the sintering process, and the sintering reaction is completed within a predetermined time. Can be made.

  In addition, since solid fuel can be produced at low cost using inferior coal such as lignite and subbituminous coal, which is inexpensive, rich in moisture, volatile components, and N, the effectiveness of inferior coal resources that cannot be used as coke raw material The social significance is high in terms of use.

  The following experiment was conducted using an internal combustion rotary kiln having a diameter of 1.6 m and a length of 22 m.

  In Comparative Example 1, using raw coal obtained by pulverizing steam coal having a VM content of 30% (coal used for combustion of a coal-fired boiler) so as to contain 100% of particles having a particle size of 20 mm or less, 3 t This raw coal was fed into the rotary kiln at a feed rate of / h. The ratio of coal particles having a particle size of less than 500 μm in the raw material coal was 14% by mass. As a heating fuel, 300 liter / h of heavy oil was supplied into a rotary kiln from a fuel supply probe (fuel supply burner).

As a combustion air amount corresponding to a heavy oil (fuel) supply amount, 3000 Nm ³ / h of air was supplied into the rotary kiln. This amount is a supply amount equivalent to 1.2 times the theoretical air amount necessary for combustion of heavy oil (fuel), and is based on the condition of supplying the minimum amount of excess air necessary to prevent the generation of soot from the fuel. is there.

In Example 1, the same coal as in Comparative Example 1 was used, the amount of heavy oil (fuel) used was reduced to 45 liters / h, and the amount of air supplied was increased to 5200 Nm ³ / h. In this case, the theoretical amount of air required for combustion of the heavy oil as a fuel is about 420 nm ³ / h, the amount of air remaining around 4780Nm ³ is required for combustion of the pulverized particles having a particle size 250μm in finished product char Theoretical air volume. In Example 1, the temperature in the rotary kiln was 300 ° C. on the raw material input side and 1150 ° C. on the product char discharge side.

In Comparative Example 2, the same equipment as Comparative Example 1 was used, and the dry distillation conditions of Comparative Example 1 were partially changed. That is, the type of coal raw material was changed and the dry distillation temperature was lowered to conduct the dry distillation test. Here, sub-bituminous coal having a VM content of 38% was used as raw coal. The ratio of coal particles having a particle size of less than 500 μm in the raw material coal was 10% by mass. Furthermore, the supply amount of heavy oil (fuel) was reduced to 230 liters / h. The air supply amount was 330 Nm ³ / h corresponding to 1.2 times the theoretical air amount.

In Example 2, the same coal as in Comparative Example 1 was used, the amount of heavy oil (fuel) used was reduced to 40 liter / h, and the amount of air supplied was increased to 2500 Nm ³ / h. In this case, the theoretical air amount necessary for combustion of heavy oil as fuel is about 370 Nm ³ / h, and the remaining air amount is the theoretical air amount necessary for combustion of fine powder particles having a particle diameter of less than 250 μm in the product char. It is. In Example 2, the temperature in the rotary kiln was 300 ° C. on the raw material input side and 850 ° C. on the product char discharge side.

  Table 1 shows the particle size distribution of the chars produced in Comparative Examples 1 and 2 and Examples 1 and 2. The ratio of fine particles having a particle size of less than 250 μm (−0.25 mm) in the product char was 18 to 30% by mass in the comparative example, but was significantly reduced in the example (1.9% by mass in Example 1). In Example 2, it is 3.8% by mass).

  Using the above product char, a sintering test was performed using a cylindrical sintering test apparatus having a diameter of 300 mmφ and a height of 600 mm. Four types of chars (coal dry distillation char) of Comparative Example 1, Comparative Example 2, Example 1 and Example 2 were blended with other raw materials so that the mixing ratio of each raw material shown in Table 2 was obtained. A sintered raw material was prepared and fired under a constant condition of a negative pressure of 15 kPa, and the production rate, product yield, and strength were measured.

  The results of the sintering test are shown in Table 3. When the chars of Example 1 and Example 2 having a low ratio of fine particles having a particle diameter of less than 250 μm are used, productivity improvement of 20% by mass or more compared to Comparative Example 1 and Comparative Example 2 (for example, (Example 1 The production rate 38.6) of Comparative Example 1 was 31.4) /38.6≈0.2), and the product yield and product strength were also greatly improved.

  It is possible to provide a method for producing a solid fuel for sintering having a quality necessary for substantially improving the combustibility of the solid fuel in the sintering process and obtaining the productivity improvement effect in the sinter production process.

DESCRIPTION OF SYMBOLS 1 Coal hopper 2 Cutting conveyor 3 Coal inlet 4 Rotary kiln 5 Fuel supply burner (burner)
6 Air compressor 7 Cooling device 8 Discharge conveyor 9 Char (product char)
10 Exhaust gas combustion furnace 11 Dust collector 12 Waste heat recovery boiler (boiler)
13 Stack (chimney)

Claims (5)

A method for producing a solid fuel for sintering, in which char is used as a solid fuel for sintering by heat-drying coal in a temperature range of 300 to 1150 ° C. with a rotary kiln,
From the product discharge side of the rotary kiln, 90 to 110% of the total amount of theoretical combustion air necessary for fuel combustion and theoretical combustion air necessary for combustion of fine particles having a particle diameter of less than 250 μm generated from the coal The air and the fuel in an amount within the range are supplied, the fine particles having a particle size of less than 250 μm generated from the coal in the rotary kiln are removed by combustion, and the coal is dry-distilled. Solid fuel manufacturing method. A method for producing a solid fuel for sintering, in which char is used as a solid fuel for sintering by heat-drying coal in a temperature range of 300 to 1150 ° C. with a rotary kiln,
From the product discharge side of the rotary kiln, air is supplied in an amount in the range of 90 to 110% of the theoretical combustion air amount necessary for combustion of fine particles having a particle size of less than 250 μm generated from the coal, A method for producing a solid fuel for sintering, wherein the fine powder particles having a particle diameter of less than 250 μm generated from coal are removed by combustion, and the coal is subjected to dry distillation.   The sintering according to claim 1 or 2, wherein the content of fine particles having a particle size of less than 250 µm in the char discharged as a product is adjusted to less than 10% by mass from the product discharge side of the rotary kiln. Method for manufacturing solid fuel.   A solid fuel for sintering produced by the method for producing a solid fuel for sintering according to claim 1 or 2.   A method for producing a sintered ore comprising mixing the solid fuel for sintering according to claim 4 in a sintering raw material.

Images