JPS6013737B2 - Method for firing powder raw materials such as cement - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the firing of cement powder raw materials such as limestone, clay, silica stone, etc., or powder raw materials such as limestone and alumina alone (hereinafter referred to as "powder raw materials such as cement"). Regarding the method.

For example, equipment for obtaining clinker by firing these cement powder raw materials includes a combination of a suspension-type raw material preheating system, a temporary heating system with an independent heat source, a rotary kiln for firing, and a clinker cooling system. 'BI Pyz consisting of a fluidized bed kiln with an independent heat source, an air preheater, a raw material preheater, etc.
el system, [C} A vertical raw material heating device that feeds the cement raw material that has been granulated into small diameter pellets in advance, a hot air supply device that serves as secondary air for fluidization or combustion, each independent of the other. A two-stage fluidized fluidized kiln with a heat source and a packed bed clinker cooling device,
The following three types can be cited as conventionally known representative examples.

However, among the above methods, in the wind method currently in use, almost all of the decarboxylation reaction of the powdered raw material is carried out in the suspension-type raw material preheating device and in the quasi-drying furnace, which has an independent heat source. Although the scale of a rotary kiln for firing raw materials can be made smaller to some extent than when such a calciner is not installed, the heat transfer within the rotary kiln is limited to the surface of the cement raw material layer deposited. The heat transfer efficiency cannot be said to be good because the heat transfer is carried out through the contact portion of the inner wall surface of the kiln.

Therefore, the size of the firing-related equipment increases, which inevitably results in increases in heat dissipation loss, installation of the equipment, area occupied, and power for driving the equipment.

Moreover, since the formation of a high-temperature fire is necessary for the firing of the pseudo-fired raw material, the kiln lining is fireproof due to the frequent occurrence of toxic gases such as N○x and excessive heat load in the firing zone within the kiln. Disadvantages such as severe burnout of objects and short service life are recognized. In addition, in the curved method, which is considered to be still in the pilot plant stage, the head heat of the clinker is not recovered and utilized, and moreover, it is used as the core of clinker grain generation in the fluidized bed of the kiln. Since the fine clinker is circulated after being cooled, no reduction in heat consumption can be expected.

According to a certain domestic cement company, the method developed by a certain domestic cement company has not yet been put into practical use. This requires a considerable amount of heat,
The degree of progress of the decarboxylation reaction and calcination reaction is inevitably uneven between the inside and outside of these pellets, and therefore the properties of the clinker tend to vary;
Since it is impossible to apply a suspension type raw material preheating device with a pseudo-drying furnace, the required fluidized bed type calcining furnace becomes large, and as a result, it is not possible to reduce heat consumption, and the pellet granulation equipment is not suitable. This has disadvantages and drawbacks, such as an increase in the overall equipment cost.

The present invention has been completed as a result of various studies in view of the above-mentioned circumstances, and it overcomes the various inconveniences and disadvantages described above that are present in conventionally known and publicly used methods and devices for firing powder raw materials such as cement. According to the present invention, it is possible to reduce the vertical area of the entire equipment, reduce heat consumption, prevent the generation of toxic gases such as NOx, and extend the life of the refractory lining. Moreover, it is of high quality and rotary
Compared to the kiln method, clinker particles with a diameter of 4 mm can be obtained, so the crushing power of the cement mill can be reduced, and other excellent effects can be achieved.

Next, embodiments of the method of the present invention will be specifically described with reference to the drawings.

They are blended in a predetermined ratio in advance and mixed well, and then transferred from the raw material input hopper 1 to the uppermost floating heat exchanger in the suspension type raw material heating device NSP with temporary furnace, that is,
The cement powder raw material introduced into the combustion exhaust gas pipe 28 is
As shown by the solid arrow in the figure, the combustion exhaust gas conduit 2A
→ Cyclone C5 → Raw material introduction pipe 3^ → Exhaust gas pipe 28 →
Cyclone C4 → Raw material introduction pipe 3B → Exhaust gas conduit 2c → Cyclone C3 → Raw material introduction pipe 3c → Exhaust gas pipe 2o → Cyclone C2 → Raw material introduction pipe 3.

During this time, the cement powder raw material is placed in a suspension-type raw material heating device NSP with a calciner, which has a spouted bed and a vortex chamber, as shown by the dotted arrow in the figure. Furnace 4→Exhaust gas pipe 2E→Cyclone C. →Exhaust gas pipe 2. → Cyclone C2 → Exhaust gas pipe 2c → Cyclone C3 → Exhaust gas pipe 2B → Cyclone C4 → Exhaust gas pipe 2^ → Cyclone C5. (not shown), and is heated to approximately 750 oo by heat exchange with high-temperature combustion exhaust gas released into the atmosphere, and is then charged into the pseudo-dawn furnace 4. Through burner 5^,
Heavy oil, gas, or other appropriate fuel is injected, and a portion of the cooling air heated by exchanging heat with the high-temperature clinker in the fluidized bed clinker cooling device 9 is extracted as secondary air for combustion, and is passed through the conduit 10. The decarboxylation reaction of the powdered raw materials introduced thereinto is efficiently exchanged in the falsifying furnace 4, and the decarboxylation reaction of the powdered raw materials that have been introduced therein rapidly proceeds mainly within the falsifying furnace 4.

After the decarboxylation reaction has almost completely completed, the powdered raw material (hereinafter referred to as temporary raw material) whose apparent specific gravity has become smaller is suspended in the high-temperature gas rising in the calciner and is placed at the top of the calciner. The calcined raw material is discharged from a nearby entrance and enters the lowest stage cyclone C in the suspension type raw material preheating device NSP with a calcining furnace through a conduit 28, where the calcined raw material is separated and sent to a high temperature separator 7. The high-temperature (approximately 1,4000 to 1,500 qo) exhaust gas from the firing furnace 8 accompanied by pongee grain clinker and grain firing raw materials is fed into the conduit 2F connecting the raw material separator 6 and the unfired raw material separator 6 through the raw material introduction pipe 38. The unfired raw materials are conveyed to the unfired raw material separator while being mixed with the unfired raw materials and subjected to heat exchange. The calcined raw materials and clinker collected in the calcined raw material separator are introduced into the upper surface of the perforated plate 8A in the fluidized bed type calcining furnace 8 through the raw material introduction pipe 3p.

Incidentally, since the temperature of these calcined raw materials is still maintained below the liquid phase formation start temperature (approximately 1,250 qo) at this stage, the temperature of the calcined raw materials is still maintained below the liquid phase formation start temperature (approximately 1,250 qo). Problems such as sticking and growth of the molten components of the raw materials do not occur.

Note that in this unfired raw material separator 6, as mentioned above,
The high-temperature calcining furnace exhaust gas separated from the calcining raw material and the pongee grain clinker is guided to the suspension type raw material heating device NSP with calcining furnace installed above it, and the cement powder raw material input from the raw material input hopper 1 is fed into the calcining furnace. It is used for preheating. On the other hand, inside this fluidized bed type firing furnace 8, the liquid phase generation temperature range is 1,
Since it is maintained at around 4000 to 1,500q0,
A portion of the input calcining raw material is melted and aggregated to form a nucleus, or is attached to clinker particles already staying in the furnace, thereby being granulated and fired. As will be described later, inside this firing furnace 8, there is a high-velocity flow due to the fluidizing air and combustion gas from the clinker cooling device 9 introduced into the air chamber at the bottom of the perforated plate 8^. From the high temperature side of the clinker cooling device 9, for example, on the upper surface side of the perforated plate 8^, via a conduit 10^ that passes through one or more closures provided on the side wall of the perforated plate 8^. Since secondary air for combustion is supplied toward the center or in the direction of rotation, the solid particles in the firing furnace are mixed,
Diffusion is very good.

Therefore, the movement of these particles in the firing furnace is active, and as a result, it is possible not only to prevent the solid particles from adhering to each other but also to the furnace wall and the bottom of the furnace. Since the fuel such as pulverized coal or heavy oil, which is injected from one or more appropriately arranged burners 5B, is sufficiently mixed with the false raw materials, the temperature distribution inside the kiln is as follows. It becomes uniform and high quality clinker can be easily obtained.

In this way, the chemical reaction has been completed in the firing furnace, and the relatively aggregated clinker that has been granulated and fired is mixed with the remaining unfired raw materials whose predetermined reactions have not been completed due to insufficient residence time. Together with the pongee clinker, it is discharged along with the rising high-speed combustion exhaust gas, passes through the conduit 2G, and enters the high-temperature separator 7, where the difference in particle size between the coarse clinker, the pongee clinker, and the unfired raw material is determined. separated by

That is, the lees clinker is in the introduction pipe 3. The lightweight pongee grain clinker and unfired raw materials mixed therein are suspended in the high-temperature exhaust gas from the kiln and are fed to the high-temperature part of the clinker cooling device by their own weight. Conduit 2F → Calcination raw material separator. 6 → Introduction pipe 3F → Firing furnace 8 →
While circulating through the path from the exhaust gas pipe 2G to the high-temperature separator 7, all of the gas is sufficiently fired and granulated to grow into a predetermined coarse-grained clinker, and finally passes through the introduction pipe 3G to cool the clinker. is guided to device 9. As mentioned above, the particles of high-temperature clinker fed into a fluidized bed cooling system are generally uniform in size, so problems such as local blow-through occur, making it difficult to maintain a good fluidized bed. forming a perforated plate 9
^ Cooling air is pumped into the lower air chamber for extremely efficient cooling.

In the fluidized bed cooling device 9, an appropriate amount of the cooling air whose temperature has increased by exchanging heat with the high-temperature coarse clinker is, as described above, drawn from the high-temperature side and passed through the conduit. 10
, 10^ to the falsification furnace 4 and the firing furnace 8, respectively, as secondary air for combustion.

Also, a part of the excess high temperature air (approximately 200 to 300 q0) exhausted from the low temperature side of this cooling device is used as fluidizing air for clinker etc. loaded in the firing furnace 8, as described above. For example, mulch to remove the clinker that it contains.

A high-temperature dust collector 7^ such as a vacuum cleaner 7^ and a proar B2 are press-fitted into the air chamber in the lower part of the firing furnace via the interposed pressure feed pipe 10B. The remaining part passes through the exhaust pipe 2J and passes through the dust collector (
Heat can be further recovered by releasing the heat into the atmosphere through a heat exchanger (not shown) or, if necessary, guiding it to a waste heat boiler (not shown).

By the way, when the particle size of the clinker produced in the kiln 8 tends to be small, the clinker collected in the high temperature separator 7 is not directly put into the cooling device 9,
The secondary air is fed into a secondary air supply conduit 10^ that connects this cooling device and the firing furnace 8, and a variable throttle 1 is provided at a suitable position in the secondary air supply pipe 10^.
By adjusting step 2, the airflow may be separated so that only relatively large particles are sent to the cooling device. The clinker that has been cooled in a fluidized bed cooling device and taken out as a product is passed through a vibrating sieve 11 to separate the mixed raw material for firing, and the separated fine unfired raw material powder is collected at a high temperature. Separately collected via dust container 7^,
It is also possible to guide the secondary air through the citrus air conduit 10' together with the dust contained in the exhaust gas from the clinker cooling device 9 through the conduit 10c and return it to the calciner 4. If the liquid phase component is large, the exhaust gas pipe 2G is connected from the top outlet of the firing furnace 8.
, the high-temperature separator 7, the exhaust gas conduit 2F, and the region up to the unfired raw material separator 6 is above the liquid phase formation start temperature. Coating problems such as adhesion and growth of the molten material are likely to occur.

In such a case, all or an appropriate amount of the calcined raw material collected by the lowermost cyclone C constituting the suspension type raw material heating device NSP with calciner 8 is transferred to the outlet side of the calciner 8 and the high temperature. By injecting it into the conduit 2G that communicates with the inlet side of the separator 7 and at a position near the outlet of the firing furnace via the introduction pipe 3, the temperature in those areas is lowered to below the liquid phase formation start temperature. and is retained, so there is no need to worry about such coaching troubles. It should be noted that the present invention is not limited to the above embodiments, and it goes without saying that various design changes may be made within the scope of the invention.

[Brief explanation of drawings]

The drawing is an example of a schematic side view of the entire cement powder raw material firing apparatus suitable for carrying out the method of the present invention. 1... Raw material input hopper, C, ~C5... Cyclone, 2^~2G... Combustion exhaust gas pipe, 3^~
3, ... Raw material introduction pipe, 4 ... False dawn furnace, 5^, 5
B...Burner, 6...Unfired raw material separator, 7.
...High temperature separator, 7^...High temperature dust collector,
8... Firing furnace, 9... Clinker cooling device,
10, 10^, 10B... Conduit for high-temperature air from the clinker cooling device, 10... Conduit, 11.
...Vibrating sieve, 12...Variable aperture, B
...Primary air fan, B2, &, B4...
...Blower, NSP...Suspension type raw material preheating device with temporary furnace. Ta-no-zu

Claims (1)

[Scope of Claims] 1. A raw material preheating device that combines a firing device for powdered raw materials such as cement with a calcining furnace that has an independent heat source, a high-temperature separator, an unfired raw material separator, and a calcining furnace that has an independent heat source. and a clinker (product) cooling device, by exchanging powder raw materials such as cement with high-temperature exhaust gas rising through the green raw material separator and combustion gas in the calciner. , the decarboxylation reaction is almost completely carried out in the raw material preheating device and the calcining furnace, and all or part of the calcined raw material thus obtained is transferred to the exhaust gas outlet side of the high temperature separator and the uncalcined raw material separator. The waste gas is introduced into a conduit that communicates with the exhaust gas inlet side of the furnace, mixed with the high-temperature exhaust gas from the firing furnace containing fine clinker and unfired powder raw materials, and guided to the unfired raw material separator while exchanging heat. Powdered or granular solids separated and collected from the high-temperature exhaust gas are fed into the kiln, and the clinker, which is granulated and fired there, is suspended in the high-temperature exhaust gas along with the unfired raw materials and is then released from the outlet of the kiln. It is discharged and sent to the high temperature separator, where only the selectively separated coarse clinker is sent to the clinker cooling device, and the remaining unburned raw materials and fine clinker are left after the calcination reaction has been completed and the desired One formed by connecting the high temperature separator, green raw material separator and kiln until it is granulated and grown to a size, separated, collected, and fed into the clinker cooling device. In addition to ensuring that the closed circuit circulates and stagnates at high temperatures, the high-temperature exhaust gas discharged from the outlet of the firing furnace passes through the high-temperature separator, the unfired raw material separator, and the calcining furnace, and then the raw material A method for firing powdered raw materials such as cement, characterized in that the materials are guided to a preheating device. 2. The firing of powdered raw materials such as cement according to claim 1, wherein the secondary air for combustion in the calcination furnace and the calcination furnace is high-temperature air extracted from the clinker cooling device, respectively. Method. 3. The cement, etc. according to claim 1 or 2, characterized in that the raw material preheating device is of a suspension type, and the calciner has a spouted bed and a vortex chamber. Method for firing powder raw materials. 4 The kiln is a fluidized bed kiln, and a part of the high-temperature cooling air obtained by the clinker cooling device is sent to the kiln after dust removal to be used as fluidizing air. A method for firing a powder raw material such as cement according to any one of claims 1 to 3, characterized in that: 5 A suspension-type raw material preheating device that combines a firing device for powdered raw materials such as cement with a calciner that has an independent heat source, a high-temperature separator, a green raw material separator, a calciner that has an independent heat source, and clinker ( The powder raw material such as cement is cooled by heat exchange with the high-temperature exhaust gas rising through the green raw material separator and the combustion gas in the calciner. A conduit for communicating part or all of the calcined raw material obtained by almost complete decarboxylation in the preheating device and the calcining furnace between the outlet side of the calciner and the inlet side of the high-temperature separator. The high-temperature separator is injected into the kiln at a position near the exit of the kiln, and is mixed and heat-exchanged with the high-temperature exhaust gas from the kiln containing the clinker and unburned powder raw materials whose temperature has been appropriately lowered. The powdered or granular solids separated and collected from the high-temperature exhaust gas are then introduced into the kiln, where the granulated and fired clinker is converted into unfired raw material. At the same time, the coarse clinker is discharged from the outlet of the kiln while suspended in high-temperature exhaust gas, and sent to the high-temperature separator, where only the coarse clinker that has been selectively separated is sent to the clinker cooling device, and the remaining unbaked clinker is sent to the clinker cooling device. The raw material and fine clinker are kept in the high-temperature separator until the firing reaction is completed, they are granulated and grown to a desired size, separated, collected, and fed into the clinker cooling device. , the high-temperature exhaust gas discharged from the outlet of the kiln is reliably circulated and retained in a closed circuit formed by the connection of the unfired raw material separator and the kiln in a high-temperature state. A method for firing a powder raw material such as cement, characterized in that the raw material is led to the raw material preheating device through a separator, an unfired raw material separator, and a calcining furnace. 6 A raw material preheating device that combines a calcination device for powdered raw materials such as cement with a calciner that has an independent heat source, a high-temperature separator, an unfired raw material separator, a kiln that has an independent heat source, and a clinker (product). The powder raw material such as cement is heated by heat exchange with the high-temperature exhaust gas rising through the green raw material separator and the combustion gas in the calciner. The decarboxylation reaction is almost completely carried out in the calcining furnace, and all or part of the calcined raw material thus obtained is transferred between the exhaust gas outlet side of the high-temperature separator and the exhaust gas inlet side of the green raw material separator. It is introduced into the connecting pipe, mixed with the high-temperature exhaust gas from the firing furnace containing fine clinker and unfired powder raw materials, and guided to the unfired raw material separator while exchanging heat, where it is separated and captured from the high-temperature exhaust gas. The collected powder or granular bodies are put into the kiln, and the clinker granulated and fired there is discharged from the outlet of the kiln while suspended in high-temperature exhaust gas together with the unfired raw materials. The relatively coarse clinker is sent to a high-temperature separator, where it is selectively separated, and then introduced into a secondary air supply conduit that connects the clinker cooling device and the kiln, where it is air-separated. Only large particles are allowed to fall into the clinker cooling device, and the clinker is cooled in this cooling device and taken out as a product. , if necessary, a conduit for supplying high-temperature air extracted from the clinker cooling device to remove dust contained in the recovered unfired raw material and the high-temperature exhaust gas from the clinker cooling device that was separately collected by a high-temperature dust collector. A method for firing a powder raw material such as cement, characterized in that the raw material is returned to the calcining furnace through the calcination furnace.