JPS581324B2 - Method of crushing, drying and burning coal - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a method for pulverizing and drying coal and burning coal in a pollution-free and energy-saving manner by minimizing the amount of primary air even when the coal has a high moisture content. .

Flame formation has a substantial impact on the energy consumption of process furnaces.

To reduce heat consumption, fast combustion (burn-up) with favorable heat transfer by short, hot flames is required.

Quantities and values that are important for this, among other factors, are the proportion of primary air, the temperature of the secondary air, the temperature of the primary air and the blowing impact rate.

Note that primary air is air for blowing pulverized coal into the furnace, and secondary air is hot air sent to the furnace from a clinker cooler connected to the furnace.

While primary air has a relatively low temperature, secondary air has a very high temperature due to the amount of heat absorbed during cooling of the clinker in the clinker cooler.

Therefore, the proportion of primary air should be as small as possible and the temperatures of primary and secondary air should be as high as possible.

The blowing speed and the components of the momentum moment of combustion in the furnace should be freely selected within the optimum range.

Conventionally, three methods are known for burning coal: 1. indirect combustion 2. direct combustion 3. semi-direct combustion with or without an auxiliary filter.

In the case of indirect combustion, the coal grinding and drying equipment is operated completely independently of the combustion in the furnace.

In this method, the factors that have a decisive influence on the flame formation can be optimized independently of the grinding dryer, but a separate filter and grinder are required to purify the dust-containing grinder exhaust air. An intermediate storage container is required for the dried coal.

This method is therefore dangerous in terms of coal dust explosions and coal dust fires, and is expensive due to the required investment, maintenance and maintenance.

In the case of direct combustion, the entire mill exhaust air containing coal dust is blown into the process furnace.

The investment costs are considerably lower, since, for example, separate filters for cleaning the dust-containing grinding device exhaust air and intermediate storage tanks for the ground dry coal are no longer required.

The absence of these intermediate equipment and necessary intermediate steps substantially reduces the risk of coal explosions and coal fires.

However, the disadvantage is that the proportion of primary air is high.

Accordingly, an optimum blowing impact rate at the furnace burner cannot be achieved.

In semi-direct combustion, the pulverizer exhaust air containing coal dust is preliminarily dedusted using a cyclone.

A part of this air is sent back to the grinding system as circulating air,
It serves as additional carrier air in the crushing device and the remainder is blown into the furnace together with the coal dust separated in the cyclone.

If the coal has a high moisture content, and if the grinding device is heated at low temperatures, a greater amount of discharge air leaves the dryer than corresponds to the amount of carrier air.

Therefore, in these cases, either large volumes of primary air must be tolerated or additional filtration devices must be installed.

The same disadvantages thus arise as in the case of direct and indirect combustion.

In other words, if the amount of primary air is large, the furnace combustor (burner)
Optimization of the blow impact rate in the process is hindered, and additional filtration equipment means additional investment and increased risk of coal explosions and coal fires.

Therefore, it is an object of the present invention to be able to freely select and keep the amount of primary air small independently of the moisture content of the coal and the heating conditions in the pulverizer, and to change the blowing ratio in the burner nozzle from the pulverizing and drying method. can be regulated independently, while eliminating the need for separate coal dust filters and intermediate storage tanks, as in indirect process installations, and the associated safety hazards and excess costs. It is an object of the present invention to provide a method in which the heat of the exhaust air of the grinding device can be recovered.

This problem is achieved according to the invention by utilizing the part of the dust-laden air from the crushing device that is not required as primary air for heating the secondary air and/or cooling the heated material. resolved.

In a preferred embodiment, the part of the comminution outlet air which is not required as primary air is pre-dedusted through a pre-cleaning device, in particular a cyclone, before being used for cooling the heated material and/or for producing secondary air. Since it is utilized for heating, the heat from the heated material is also recovered for heating the grinder exhaust air.

In another preferred embodiment, the warm mill exhaust air containing coal dust is blown into the hot front section of the clinker cooler to recover heat there as well.

The residual coal dust is also ignited in this high-temperature zone, which results in a more thorough removal of the residual coal dust, which of course also heats the secondary air.

In another preferred embodiment, the grinding unit exhaust air is pre-cleaned through a pre-cleaning device before being blown below the grate of the clinker cooler.

In a further preferred embodiment, the grinding unit exhaust air is pre-cleaned through a pre-cleaning device before being blown over the grate of the clinker cooler.

In another preferred embodiment of the process, hot air from the clinker cooler or the top of the kiln is used for drying the coal.

In another preferred embodiment, the hot exhaust gas of the furnace equipment is utilized for coal drying.

In another particular embodiment, a dedicated combustion device is used for drying the coal.

The method of the invention is suitable for the calcination process of cement clinker, lime or expansive viscosity using a rotary kiln followed by a planetary, tube, shaft or fluidized bed cooling device.

It is also suitable for the firing process of cement clinker, lime or expanded clay when equipped with a shaft furnace or thrust wheel furnace.

The method of the invention is furthermore suitable when using ring roller mills or ball mills for grinding and drying.

Finally, the method of the invention is suitable when operating installations with coal-only combustion or mixed combustion with coal and other fuels.

In this specification, when we refer to fuel, we mean fuel whose main component is coal, and more specifically, we refer to both fuel consisting only of coal and fuel consisting of a mixture of coal and other fuels. do.

Therefore, since it contains at least coal as a main component, this fuel takes the form of coal dust particles when crushed by a crushing device.

The above-mentioned applicability of the method of the present invention is given as an example and is not meant to be limiting in any way.

The present invention makes it possible to limit the proportion of primary air for the furnace burner to the minimum necessary for optimal combustion, independent of the grinding drying system and the moisture content of the coal, while at the same time directing the remainder of the grinding unit exhaust air to a separate offshore It can be used in a pollution-free and energy-saving manner without any additional equipment.

The method according to the invention is carried out in an energy-saving manner, since the heat of the hot grinding device exhaust air is reused for heating the secondary air.

Furthermore, since the residual coal dust in the air discharged from the crusher is supplied to the secondary air, it is not necessary to separate it by filtration.

In particular, residual coal dust in this secondary air stream can be combusted according to a particular embodiment of the inventive method.

This means that the entire coal dust of the crusher exhaust air is directly and completely utilized, so that the method of the invention not only saves energy or raw materials, but also pollution-free and at lower cost. Implemented.

This is because residual coal dust is removed and separate filtering equipment is therefore no longer necessary.

Furthermore, since there is no intermediate coal dust storage tank or furnace filtration equipment, and even if the coal has a high moisture content, the associated crushing and drying equipment can be operated at a low heated air temperature without thermoeconomic loss, making it possible to inactivate the coal. The inventive method guarantees a high degree of safety against explosions or fires caused by coal dust, and even high coal moisture can be avoided by thoroughly utilizing the waste heat of the furnace and/or clinker cooler. can be overcome without any problem.

The method of the present invention will be explained with reference to the accompanying drawings.

The drawing schematically shows a device which is operated according to the method of the invention.

The device shown therein is particularly intended for cement furnaces with thrust grate cooling for clinkers.

The coal dried and crushed by the coal crushing device 1 is separated by a high-capacity cyclone 2 as a separator, and then separated by a shutoff mechanism 3.
through which it enters the primary air stream or sub-stream 4 of the primary air.

The amount of gas or air required for drying and as carrier air is drawn by the system blower 5 through the coal crusher 1 and the high capacity cyclone.

The conveying medium and drying medium to the coal crushing device 1 is the high-temperature cooling device exhaust air that has passed through the cooling device exhaust air conduit 6 or the high-temperature furnace top air that has passed through the furnace top air conduit 7 or the furnace exhaust gas conduit. Furnace exhaust gas passing through 8, combustion chamber 9
or a combination of cooling air, furnace top air, furnace exhaust gas and heating gas from the cooling air valve 10, furnace air valve 11, furnace exhaust gas valve 12 and combustion chamber valve 13 for regulation. Using the cold air valve 30, the dust-containing hot air is pre-purified in the cyclone 14.

After passing through the system blower 5, the grinding unit exhaust air containing coal dust, which has been pre-dedusted in the high-capacity cyclone 2, is divided and sent to the primary air blower 15, through the coupling conduit valve 19 and the coupling conduit 18 to the crushing unit inlet, or The cooled air is conveyed to the cooling air blower 16 of the clinker cooling device 17.

The amount of each part can be optimized depending on the amount required for the grinding system, coal moisture and flame formation, respectively, and can be adjusted within the range of 0 to 100%.

Serving for this are a coupling conduit valve 19, a cooling air supply valve 20 and an auxiliary valve 21, as well as a primary air valve 22 and a cold air mixing valve 23.

This adjustability allows the proportion of primary air to be lowered arbitrarily and allows very different burner nozzles 24 and combination combustion devices with e.g. You can drive the car without having to put it in.

Particularly if the coal has a high moisture content, a larger portion of the crusher exhaust air is blown into the clinker cooling system.

The blowing can take place with the aid of an existing cooling air blower 16, as shown in the figures, or directly into the cooling chamber 31, which is not shown in the figures.

Alternatively, this blowing may be done by dividing it into multiple cooling air blowers 16, or even by using a separate cooling air supply blower 34 into one or more cooling air chambers 31 or directly into the grid. 25 to the hot air section of the clinker cooler 37.

However, it is preferred to blow into the cooling air chamber 31 adjacent to the hot air portion of the clinker cooler 37.

Thereby, the sensible heat of the grinding device exhaust air can be fully utilized for secondary air heating.

Moreover, the non-sensible heat contained in the crusher exhaust air in the form of residual coal dust ignites as it passes through the hot clinker layer and is thus used up.

That further heats the secondary air. Excess cooler exhaust air is routed through exhaust air conduit 32 to exhaust air dedusting device 27 where it is dedusted.

With the help of the exhaust air blower 28 and the control valve 29, the exhaust air is discharged out of the system depending on the furnace top pressure.

In the method of the invention, unlike the indirect method, the total heat of the exhaust air, ie the sensible heat, as well as the heat present in the residual coal dust of the exhaust air, is recovered.

Moreover, as a result of the combustion of the residual coal dust, a coal filter is no longer necessary.

This represents considerable savings and increased operational safety.

The method of the invention is also substantially more pollution-free than previously known methods, since the coal dust thus no longer passes into the atmosphere.

Also, since intermediate storage of coal dust is not required, the risk of fire and explosion due to coal dust is significantly reduced.

Overall, it is self-evident that equipment, maintenance and operating costs are lower.

Unlike the direct method and semi-direct method, the amount of primary air can be freely selected.

It is therefore possible to optimize the flame and keep the primary air volume fairly low.

Fuel savings are thereby achieved, which is approximately 100 Kcal/Kg clinker (0.4
2GJ/t clinker).

[Brief explanation of the drawing]

The drawing conceptually illustrates an apparatus operated according to the method of the invention. 1... Coal crusher, 2... High capacity cyclone, 3
... Shutoff mechanism, 4... Primary air conduit, 5... System blower, 6... Cooler air conduit, 7... Furnace top air conduit, 8... Furnace exhaust gas conduit, 9.・・Combustion chamber, 1
0...Cooler air valve, 11...Furnace top air valve, 12.
...Furnace exhaust gas valve, 13...Combustion chamber valve, 14...Cyclone, 15...Primary air blower, 16...Cooling air blower, 17...Clinker cooler, 18...
Coupling conduit, 19... Coupling conduit, valve, 20... Cooling air supply valve, 21... Auxiliary valve, 22... Primary air valve,
23... Cold air mixer valve, 24... Burner nozzle, 25... Grate, 26... Cooling air chamber, 27...
Exhaust air dust removal device, 28... Exhaust air blower, 29.
...Exhaust air blower valve, 30...Cold air valve, 31...
- Cooling air chamber, 32... Discharge air conduit, 33... System valve, 34... Cooling air supply blower, 35...
Rotary kiln, 36...Additional fuel, 37...Heated air portion of clinker cooler.

Claims (1)

[Claims] 1. A method using solid fuel mainly composed of coal for heating a kiln that discharges heated material to a cooler, comprising: a step of pulverizing the fuel in a pulverizer; transporting the separated fuel to a separator for separating coal dust particles from the coal dust-containing air using at least the air discharged from the cooler; A method for pulverizing, drying and burning coal, comprising a step of conveying using air discharged from a cooler, and a step of conveying at least a part of the coal dust-containing air to the cooler. 2. The step of pneumatically conveying the separated coal dust particles to the kiln is accomplished by air containing coal dust as primary air for conveying the separated coal dust particles to the kiln. The method described in Section 1. 3. The method according to claim 2, further comprising the step of using coal dust-containing air conveyed to a cooler as secondary air for burning the separated coal dust particles. 4 The step of pneumatically conveying at least a portion of the coal dust-containing air to the cooler includes blowing at least a portion of the coal dust-containing air below a support in the cooler that supports the heated material. 4. The method of claim 3, comprising the step of: 5. The method of claim 4, further comprising the step of conveying air from the cooler to the grinding device to dry the fuel. 6. The method of claim 4, further comprising the step of conveying combustion gases of combusted fuel particles to the grinding device for drying the fuel. 7. The method of claim 4, further comprising the step of burning residual fuel in addition to the pulverized solid fuel to heat the kiln. 8 Claims 4, 5, and 6 further comprising a step of recirculating a part of the coal dust-containing air to the crushing device.
The method according to any one of paragraphs 1 and 7. 9. The cooler is a clinker cooler, in which coal is used as the fuel and a cyclone is used as the separator to heat a kiln that discharges clinker as heated material into a grate in the clinker cooler. further comprising the step of separating the coal dust-containing air separated by the cyclone into at least a first and second flow, and the step of air conveying the separated coal dust particles to a kiln, said first flow of coal dust-containing air as primary air for blowing the coal dust-containing air into the combustion kiln; blowing said second stream of coal dust-laden air into a clinker cooler below a grate of the clinker cooler to combust the separated coal dust particles as secondary air to combust the separated coal dust particles; Claim further comprising the step of using the hot air obtained from said blowing step and the step of conveying combustion gas from the burned coal particles to a coal crushing device for drying the coal in the crushing device. The method described in item 1. 10. The method of claim 9, further comprising the step of conveying hot air from the clinker cooler to the coal crusher to dry the coal within the coal crusher. 11 Combustion gas or air from the clinker cooler,
11. The method according to claim 10, further comprising the step of cleaning prior to conveying to a coal crusher. 12 The step of separating the coal dust-containing air discharged from the cyclone into at least a first or second flow includes separating the coal dust-containing air discharged from the cyclone into first, second, and third flows. 12. The method of claim 11, further comprising the step of recirculating the third stream to the coal crusher.