JPS5917063B2 - Limestone firing method using solid fuel with high volatile content - Google Patents

Description

[Detailed Description of the Invention] This invention efficiently produces limestone (including dolomite, magnesite, and similar calcined raw materials) by charging solid fuel with a high volatile content into a calcining furnace in the form of lumps or granules. The present invention relates to a firing method in a limestone kiln for safely producing quicklime (including calcined dolomite, calcined magnesite, and the like) by safely firing (calcining).

Conventionally, in this type of limestone kiln, raw materials and fuel containing no or only a small amount of volatile matter are charged from the top of the furnace, either simultaneously or in alternating layers, and the preheating zone is moved downward from the top of the furnace. A method of firing limestone, etc. is carried out in which a firing zone and a cooling zone are configured, product cooling air is introduced from the lower part of the cooling zone, and exhaust gases such as combustion exhaust gas and gases generated due to combustion decomposition of raw materials are discharged from the upper part of the pre-preparation zone. I was worried.

In this case, the fuel used is coke from which volatile matter has been removed by carbonization of coal, etc., or anthracite, which originally has a very low volatile matter content. , lignite, etc. were not used as fuel.

This is because thermal decomposition of the fuel begins to occur when the fuel is heated together with the raw materials in the preheating zone and reaches the firing zone, but at this temperature, the components generated by thermal decomposition, that is, the volatile matter in the fuel, cannot yet be combusted. This is because it cannot be done.

In other words, in the conventional firing method, the volatile matter in the fuel is exhausted outside the furnace without being used as a heat source, or as a heat source, which not only causes a large loss in terms of thermoeconomics but also reduces the Burning outside may cause explosion hazard,
Furthermore, there were many safety problems, such as the emission of toxic components such as carbon monoxide.

In addition, some of the gas generated by thermal decomposition in a relatively high-temperature atmosphere condenses into a liquid in relatively low-temperature areas such as the preheating zone or flue, which can cause various problems such as blockage inside the furnace. This sometimes made it impossible to continue operating the furnace.

For the reasons mentioned above, it has been impossible to use solid fuel with a high volatile content in the form of lumps or granules in the conventional limestone firing method.

In order to use a solid fuel with a high volatile content, it is necessary to burn it in a separate device installed outside the furnace and then introduce the generated high-temperature combustion gas into the furnace, or if the solid fuel is pulverized and used as a liquid fuel. The only way to do this is to burn it using a similar method, and both methods had many problems in terms of thermal efficiency and ease of operation.

As explained below, this invention uses a firing method in which liquid fuel and lump or granular solid fuel, which are handled in completely different ways, are introduced into the furnace body from the side of the firing zone. In addition, it is possible to utilize the heat generated when solid fuel with a high volatile content is charged into the furnace in lump or granular form and combusted, or in any device. This is what I did.

Hereinafter, a limestone firing furnace employing the firing method of the present invention will be explained with reference to the drawings.

FIG. 1 is a vertical cross-sectional (schematic) view of a limestone kiln in which a conventional limestone kiln method is carried out.

Moreover, FIGS. 2 to 5 are longitudinal sectional views of a limestone firing furnace in which the limestone firing method of the present invention is carried out.

1 is a furnace body of a limestone kiln, 2 is a raw material feeding device, 3 is a product discharge device, 4 is a furnace exhaust gas outlet, 5 is a product cooling air inlet,
6 Extraction of gas and/or air and/or
An inlet, 7 a beam, 9 a space formed inside the furnace based on the angle of repose of the solid, 11 an exhaust gas fan, 12 an air fan, 13 a recuperator, 15 a valve or damper, 16 an auxiliary heat source 17 is a solid fuel hopper, 18 is a rock feeder, 19 is a solid fuel feeder, and 20 is a fuel input port.

In addition, P is a preheating zone, B is a firing zone, B1 is an upper firing zone, B
2 is a lower firing zone, and C is a cooling zone.

FIG. 1 shows an embodiment of a limestone kiln for calcining limestone using a solid fuel containing no or only a small amount of volatile matter.

In the figure, the gas flow (solid and dotted arrows) flows countercurrently upward throughout the furnace with respect to the downward solid flow (double solid arrows).

FIG. 2 shows a vertical cross-sectional view (schematic) of a basic embodiment of a limestone kiln in which the limestone kiln method of the present invention is implemented.

The raw material to be calcined (double solid line) is charged into the furnace body 1 by a raw material feeding device 2 provided at the top of the furnace.

On the other hand, the solid fuel is directly fed into the firing zone B in the form of lumps and/or granules by the feeder 19 from the side of the furnace body.

The solid fuel charged into the firing zone B is thermally decomposed while descending in the firing zone B together with the raw material, and volatile components are gasified.

The combustible components in the gasified volatile matter are mainly stored in the fuel input port 2.
The remaining fixed carbon that has been burned in the upper firing zone B1 above 0 and the volatile matter has been evaporated is mainly burned in the lower firing zone B2 below the fuel inlet 20.

In this way, since the volatile matter during combustion and the fixed carbon are combusted in separate zones, overheating can be prevented and a uniform calcined product can be obtained.

The air necessary for combustion of the solid fuel is introduced into the furnace body 1 from the product air population 5 at the bottom of the furnace by a cold air forcing fan (not shown) and/or an exhaust gas fan 11, and ascends through the cooling zone C. In the meantime, it is heated by exchanging heat with the calcined product (indicated by the dotted arrow in the figure).

The mixture of combustion gas generated by combustion of fuel in firing zones B1 and B2 and gas generated by heat exchange of raw materials exchanges heat with the raw materials while ascending the preheating zone P (solid arrow) and becomes furnace exhaust gas. The fan 11 exhausts the exhaust gas out of the furnace body 1 from the furnace exhaust gas outlet 4 and dissipates it into the atmosphere.

On the other hand, the calcined product (double solid line arrow) is taken out of the furnace body 1 by the product discharge device 3.

The design of the preheating zone P, the firing zone B, and the cooling zone C, especially the length of each zone, can be determined so that the temperature of each zone is suitable for burning the fuel and calcining the raw materials.

In the limestone firing method of the present invention, in order to directly charge solid fuel with a high volatile content into the firing zone B from the side of the furnace body 1, it is necessary to A beam-like object 7 or the like is installed inside the body to form a space 9 corresponding to the angle of repose of the solid, and solid fuel is introduced into this space 9.

Next, the beam-like object 7 will be explained.

As for the number of beams 7a of the beam-shaped member 7, the greater the number, the better, since if there is only one beam, the cross section of the furnace body 1 will lack uniformity.

However, if there are too many, the passage (cross-sectional area) inside the furnace will be narrowed, so the number will be determined by itself.

The shape of the beam 7a is such that the lower part is wider than the upper part as shown in Fig. 6 in order to reduce the resistance to solid flow and form a wide space, and it is arched in order to provide sufficient mechanical strength. Design it to be.

In addition, in order to prevent the disadvantage that gas tends to collect on the wall surface of the furnace,
The shape of the beam 7a is widened at the center of the furnace body 1, as shown in FIG. 7, so that the filling material in the center is low.

Narrow the furnace wall.

In addition, if the structure inside the furnace body 1 is made into an inverted conical shape as shown in FIG. 8 without installing the beam-like object 7, or if it is made into a pre-drawn shape as shown in FIG. Since the space 9 corresponding to the angle of repose is naturally formed, the same effect as when the beam-like object 7 is provided can be achieved.

FIG. 3 is a longitudinal sectional view (schematic) showing another embodiment of the limestone firing method of the present invention.

In this embodiment, in FIG. 2, a part of the raw material introduced into the furnace body 1 from the raw material feeding device 2 provided at the top of the furnace is transferred from a raw material storage tank (not shown) to a raw material introduction branch pipe 23. The solid fuel is introduced into the mixer 21, where it is mixed with the solid fuel introduced from the fuel tank (not shown) through the fuel introduction pipe 22, and then directly charged into the firing zone B from the side of the furnace body.

The materials mixed with fuel and introduced into the calcination zone B are not limited to raw materials, but include calcined products, intermediate products, and other materials that have a negative impact on the calcination operation and product quality. It is acceptable as long as it does not affect

By mixing the combustion with raw materials and diluting it in this way, it becomes possible to make the fuel distribution in the horizontal direction of the firing zone more uniform.

FIG. 4 is a longitudinal sectional view (schematic) showing another embodiment of the limestone firing method of the present invention.

In this embodiment, as shown in FIG. 4, solid fuel in the form of lumps and/or granules is introduced into a space 9 formed according to the angle of repose of the solid, and a burner is provided to provide fluid fuel and ( or) introducing auxiliary heat sources such as powdered solid fuel and/or heated gas.

The device 16 for generating the auxiliary heat source is usually provided at a location where solid fuel in lumps and/or granules is directly introduced into the firing zone, but it may also be provided at the boundary between the lower firing zone B2 and the cooling zone C.

Instead of (or in combination with) the auxiliary heat source, room temperature or heated air may be introduced for the purpose of promoting combustion.

By using an auxiliary heat source in combination, the temperature distribution in each zone can be brought close to the ideal state.

A part of the mixture of combustion gas generated by combustion of fuel in firing zones B1 and B2 and gas generated by thermal decomposition of raw materials is removed from the furnace by exhaust gas fan 11 from the boundary between preheating zone P and upper firing zone B1. It is extracted into the recuperator 13, where it exchanges heat with the cold air sent in from the air fan 12 to lower its temperature, and is further dissipated into the atmosphere together with the furnace exhaust gas extracted from the furnace top by the exhaust gas fan 11. Ru.

On the other hand, in the recuperator 13, heated air (indicated by dotted arrows in the figure) heated by heat exchange with the furnace exhaust gas is sent to a device 16 that generates an auxiliary heat source, and is sent to the sintering zone and/or lower sintering area along with auxiliary fuel. It is introduced into the furnace body from the boundary between zone B2 and cooling zone C.

FIG. 5 is a longitudinal sectional view (schematic) showing another embodiment of the limestone firing method of the present invention.

In this embodiment, in FIG. 4, a part of the raw material fed into the furnace body 1 from the raw material feeding device 2 provided at the top of the furnace is transferred from a raw material storage tank (not shown) to a raw material introduction branch pipe 23. The solid fuel is introduced into a mixer 21, where it is mixed with solid fuel introduced from a fuel tank (not shown) through a fuel introduction pipe 22, and then directly introduced into the firing zone B from the furnace body side.

Since the limestone firing method of the present invention is carried out as described above, it can achieve the following effects compared to conventional methods.

(1) Since all the combustible components in the volatile matter of the fuel are combusted within the furnace, there is no danger of combustion outside the furnace and, in some cases, explosion.

(2) It is safe to work with because there is no risk of toxic components such as oxygen monocarb being discharged outside the furnace.

(3) Volatile components of the fuel can also be combusted, so there is no unburned loss.

(4) Volatile matter does not condense in relatively low-temperature areas such as the preheating zone or the flue, causing various problems such as clogging.

(5) The inside of the packed bed made of calcined raw materials such as limestone is used as a pyrolysis furnace for fuel, and all the volatile matter and fixed carbon that are pyrolysis products are burned in the packed bed and converted into calcined raw materials. Because combustion heat is directly transferred, the thermal efficiency is much higher than the conventional method in which high-temperature combustion gas produced by burning fuel outside the furnace, that is, outside the packed bed, is introduced into the packed bed.

(6) Because a region where combustible components in the volatile matter burn and a region where fixed carbon burns are formed in the firing zone, local overheating does not occur and stable furnace operation produces high quality and homogeneous products. You can get it at

(7) A part of the ash contained in the fuel is contained in the exhaust gas and discharged outside the furnace, and the other part is discharged together with the product, but the ash tends to selectively adhere to products with small particle sizes. Therefore, it is easy to obtain products with low ash content through operations such as sieving.

Ash in the exhaust gas can be collected using a known dust collector.

When coke is used as a raw material, the volatile matter in the coke raw material coal is not used, and only fixed carbon is used, but if the limestone firing method of the present invention is used, the volatile matter is also used. Since the ash content per unit calorific value of the fuel is lower than when coke is used, the ash content contained in the product is also reduced accordingly.

(8) Since the fuel can be used in lump or granular form, there is no need for fuel crushing equipment as in the case of pulverized coal combustion.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view (schematic) of a limestone kiln that implements a conventional limestone kiln method. FIGS. 2 to 6 are longitudinal sectional views (schematic) of a limestone kiln in which the limestone kiln method of the present invention is carried out. FIG. 2 shows a basic embodiment of the invention. FIG. 3 is a longitudinal sectional view (schematic) of an embodiment in which a method is implemented in which a portion of the fuel and raw materials are mixed and introduced directly into the firing zone. FIG. 4 is a longitudinal sectional view (schematic) of an embodiment in which a method of using an auxiliary heat source is implemented. FIG. 5 is a longitudinal cross-sectional view (schematic) of one embodiment of FIG. 4 in which a method is implemented in which a portion of the fuel and raw materials are mixed and directly introduced into the firing zone. Fig. 6 is a vertical sectional view of the main part of an embodiment in which a beam-shaped object is installed inside the furnace body, Fig. 7 is a sectional view taken along a-a of Fig. 6, and Fig. 8 shows a part of the structure inside the furnace body. FIG. 9 is a longitudinal cross-sectional view of a main part of an embodiment in which the furnace body has an inverted conical shape, and FIG. 1 is a furnace body of a limestone kiln, 2 is a raw material feeding device, 3 is a product discharge device, 4 is a furnace exhaust gas outlet, 5 is a product cooling air inlet,
6 is a gas and/or air extraction (or) inlet, 7 is a beam-like object, 9 is a space formed in the furnace body based on the angle of repose of the solid, 11 is a waste removal fan, 12 is an air fan, 13 15 is a recuperator, 15 is a valve or damper, 16 is a device for generating an auxiliary heat source, 17 is a solid fuel hopper, 18 is a row feeder, 19 is a solid fuel feeder, 20 is a fuel input port, 21 is a mixer, 22 23 is a fuel introduction pipe, and 23 is a raw material introduction branch pipe. In addition, P is a preheating zone, B is a firing zone, B1 is an upper firing zone, B
2 is a lower firing zone, and C is a cooling zone.

Claims (1)

[Scope of Claims] 1. A lime kiln that comprises a pre-heating zone, a firing zone, and a cooling zone from the top to the bottom, introducing cold air from the lower part of the cooling zone, and exhausting exhaust gas such as combustion gas from the upper part of the pre-preparing zone. In this method, raw materials are introduced from the upper part of the preheating zone, and lumpy and/or granular solid fuel is directly introduced into the firing zone from the side of the furnace body. Firing method. 2. Claim No. 2, characterized in that a part of the raw material charged from the upper part of the preheating zone is mixed with solid fuel in the form of lumps and/or granules, and the mixture is directly charged into the firing zone from the side of the furnace body. A method for burning limestone using the solid fuel with a high volatile content according to item 1. 3 Introducing fluid fuel and/or powdered solid fuel and/or heated air and/or heated gas as an auxiliary heat source into the bulk and/or granular solid fuel input location of the furnace body. A method for firing limestone using a solid fuel with a high volatile content according to claim 1 or 2, characterized in that the solid fuel has a high volatile content. 4. A space according to the angle of repose of the solid is formed inside the firing zone, and a raw material or a mixture of raw material and solid fuel is introduced into this space. , a method for firing limestone using the solid fuel with a high volatile content as described in item 3. 5. Volatilization according to claim 3, characterized in that a space is formed in accordance with the angle of repose of the solid in the furnace body, and combustion gas and/or heated air are extracted and/or introduced into this space. A method of firing limestone using solid fuel with a high content. 6. A solid fuel with a high volatile content according to claim 4 or 5, characterized in that a beam-like object is installed inside the furnace to form a space corresponding to the angle of repose of the solid. Method of firing limestone. 7. The volatilization device according to claim 4 or 5, characterized in that the main part of the furnace inner wall is formed into an inverted conical shape and/or a descending conical shape to form a space corresponding to the angle of repose of the solid. A method of firing limestone using solid fuel with a high content.