JPS6013738B2 - Method for firing powder raw materials such as cement - Google Patents

Description

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

). For example, equipment for producing clinker by firing these cement powder raw materials includes a so-called suspension-type raw material heating equipment, a calcination equipment with an independent heat source, a rotary kiln for firing, and a clinker cooling equipment. Combined, 'B} One method of Py consisting of a fluidized bed calcining furnace with an independent heat source, an air heater, a raw material heater, etc., [C] Py granulated in advance into small diameter pellets A vertical raw material heating device that inputs cement raw materials, a hot air supply device as secondary air for fluidization and combustion, a two-stage fluidized fluidized kiln with independent heat sources, and a packed bed clinker cooling device. Something that contains.

The following three types can be cited as conventionally known representative examples.

However, among the above-mentioned methods, in the wind method currently in practical use, almost all the decarboxylation reaction of the powdered raw material is carried out in the suspension-type raw material heating device and a pseudo-drying furnace that has an independent heat source. Although the rotary kiln that fires the calcined raw materials can be reduced in size to some extent compared to the case where such a calcining furnace is not installed, the heat transfer within the rotary kiln is The heat transfer efficiency cannot be said to be good because the heat transfer is carried out through the contact portion between the surface of the cement raw material layer and the inner wall surface of the kiln.

Accordingly, the size of the firing-related equipment increases, which inevitably results in an increase in heat radiation loss, equipment skirting, occupied area, and power for driving the equipment.

Moreover, since the formation of a high-temperature flame is necessary for the calcination of the raw materials, there is a high occurrence of toxic gases such as NQ, and severe damage to the refractory lining of the kiln due to the excessive heat load in the firing zone within the kiln. Disadvantages such as burnout and short service life are recognized. In addition, it is believed that the system is still in the pilot plant stage (B), where the head heat of the clinker is not recovered or utilized, and moreover, it is used as the nucleus for clinker grain production in the fluidized bed of the kiln. Since the pongee grain clinker is circulated after being cooled, it is not possible to reduce heat consumption.

Note that the firing reaction for clinker is a solid phase reaction, so while mixing of particles is good, the contact efficiency decreases.
It is impossible to avoid the disadvantage that clinker is generated and becomes heavy. The (C) method developed by a certain domestic cement company does not seem to have been put into practical use to date, but it is difficult to dry the pellet-shaped cement raw material that is fed into the raw material heating device. Because of this, a considerable amount of heat is required, and a suspension-type raw material heating device with a calciner cannot be applied, so the required fluidized bed calciner becomes large, resulting in a reduction in heat consumption. There are disadvantages and disadvantages such as not being able to achieve

The present invention has been completed as a result of various studies in view of the above-mentioned circumstances, and it solves the various inconveniences and disadvantages described above that are present in conventionally known or publicly used methods and devices for firing powder raw materials such as cement. , aimed at eliminating defects.

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

First, in FIG. 1, the raw material is mixed in a predetermined proportion in advance 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 a temporary furnace, that is, the flue gas conduit. The cement powder raw material introduced into 2A is passed through the combustion exhaust gas conduit 2A → cyclone C5 → raw material introduction pipe 3A → as shown by the solid arrow in the figure.
The cement powder raw material descends through the following path: exhaust gas pipe 2B → cyclone C4 → raw material introduction pipe 3B → exhaust gas pipe 2C → cyclone C3 → raw material introduction pipe 3C → exhaust gas pipe 2D → cyclone C2 → raw material introduction pipe 3D. In the suspension type raw material heating device NSP with temporary furnace, as shown by the dotted line arrow in the figure, the jet flow granulation device 5 → temporary furnace 4
→Exhaust gas pipe 2E→Cyclone C, →Exhaust gas pipe 2D→
Cyclone C2→Exhaust gas pipe 2C→Cyclone C3→Exhaust gas pipe 2B→Cyclone C4→Exhaust gas pipe 2A→Cyclone C5, and finally exhaust gas discharge pipe 2
1, a concession blower, and a Cottrell dust collector (all not shown).

), etc., and is preheated to about 760° C. by heat exchange with high-temperature combustion exhaust gas released into the atmosphere, and then charged into the calcining furnace 4. Heavy oil, gas, and other appropriate fuels are injected through the burner 6A, and heat is exchanged efficiently within the calciner 4, into which high-temperature combustion gas from the jet granulator 5 installed below is introduced. As a result, the decarboxylation reaction of these powder raw materials is almost completely completed, and the powder raw materials (hereinafter referred to as calcined raw materials) have a reduced apparent specific gravity.

) is discharged from an opening provided near the top of the calciner while suspended in the high-temperature gas rising in the calciner,
The artificial hoof material separated there enters the lowest stage cyclone C in the suspension type raw material preheating device NSP with a calcination furnace through the conduit 2E, and the false hoof material separated here is passed through the fluidized bed type clinker cooling device 8.
A raw material introduction pipe 3E is connected to the conduit 9 connecting this granulating device 5.
The air is injected into the upper surface of the perforated plate 5A in the granulator 5 while being mixed and heat-exchanged with high-temperature cooling air extracted as secondary combustion air from the high-temperature side of the cooling device. be introduced. By the way, the temperature of these calcined raw materials is still at the liquid phase formation start temperature (approximately 1 to 2
50 qo) or less, problems such as sticking and growth of the molten component of the raw material on the inner wall surface of the conduit 9 do not occur. Fuel such as heavy oil or gas is injected through the burner 6B, and high-temperature combustion secondary air drawn from the clinker cooling device 8 and high-temperature exhaust gas from the fluidized bed kiln 7 provided below are injected. The inside of this granulating device 5 into which the material is introduced is maintained at a liquid phase forming temperature range of approximately 1,25 to 1,35,000 psi, so that a part of the introduced material is melted, and the lower part of the material is melted. The combustion gas is passed through the throat part 58 from the firing furnace 7 at an appropriate high speed and flow rate, and is suspended in a spouted bed formed in the center of the apparatus by the rising high-temperature flue gas flow. When the particles are granulated and grow to a certain particle size or more, they fall through the throw section 58 into the firing furnace 7 due to their own weight.

Note that the high-temperature combustion gas rising from the firing furnace 7 into the granulator 5 mainly passes through the enlarged part, that is, the center of the spouted bed chamber, and rarely comes into direct contact with the surrounding area (inner wall of the granulator). The suspended raw material, which is still small in particle size, is brought to the inner wall of the device by the mixing, diffusion, swirling flow and reversing vortex formed in the granulation device, and forms a layer along the wall. , descends to near the upper end of the throat portion 5B, where they are attracted by the high-temperature ascending jet and coalesce, forming a flow pattern.

Therefore, the vicinity of the inner wall surface of the granulator above the perforated plate 5A is covered by a flow of relatively low-temperature cooling air containing the raw material introduced through the conduit 9, thereby avoiding adhesion and growth of the molten material. can. In order to ensure sufficient retention of the calcined raw materials fed in the form of pellets, this multi-chamber (two chambers in the illustrated embodiment) fluidized bed calcining furnace 7 is filled with air at the bottom of the perforated plate 7A. As will be described later, there is a flow with a low flow rate due to the fluidized air and combustion gas from the clinker cooling device 8 that are pumped into the chamber, and at the same time, on the upper surface side of the perforated plate 7A, Via the conduit 9A that communicates with one or more gates provided on the side wall, the combustion air is supplied from the high temperature side of the clinker cooling device 8, for example, toward the center or in the swirling direction. Since this secondary air is supplied, the solid particles are mixed and diffused very well in the firing furnace.

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 collapsing and fusion to the bottom of the furnace, but also to prevent the solid particles from collapsing and fusion to the bottom of the furnace. , blown from one or more burners 6C appropriately arranged in each chamber of the firing furnace, for example,
Since the fuel such as pulverized coal or heavy oil is sufficiently mixed with these temporary raw materials, the temperature distribution in the kiln becomes uniform, and high quality clinker can be easily obtained.

In this way, the chemical reaction is completed in the firing furnace, and the fired clinker is sent to the high temperature side of the clinker cooling device 8 through the introduction pipe 3F provided with the damper 11, On the other hand, the high-temperature exhaust gas in each chamber of the firing furnace rises, passes through the spouted bed granulator 5, and is led to the suspension type raw material preheating device NSP with a false dawn furnace. As mentioned above, the particles of the high-temperature clinker pellets fed into the clinker cooling device are generally uniform in size, so they form a good fluidized bed that is less prone to problems such as localized blow-through. However, cooling air is pumped into the air chamber at the bottom of the perforated plate 8A via blowers B4 and B, and the cooling air is extremely efficiently cooled.

In the fluidized bed cooling device 8, the appropriate amount of cooling air whose temperature has increased by exchanging heat with the high-temperature clinker is:
As mentioned above, the air is drawn from the high temperature side, and the conduits 9, 9A
The air is supplied as secondary combustion air to the granulator 5, calciner 4, and calciner 7 through the granulator 5, calciner 4, and calciner 7, respectively.

In addition, a part of the surplus high temperature air (approximately 200 o to 300 o'clock) exhausted from the low temperature side of this cooling device is used as a fuel for clinker etc. loaded in the kiln 7 and in the granulating device 5. To use it as fluidizing air for calcined raw materials, remove the contained clinker,
For example, the powder is pressurized into the lower air chambers of the firing furnace and the granulation apparatus through a pressure feed pipe 9B in which a high-temperature dust collector 10 such as a Multichron and blowers B, B, etc. are installed.

The remaining portion passes through the exhaust pipe 2J, passes through a dust collector (not shown), and is released into the atmosphere, or if necessary,
Heat can be further recovered by guiding the heat to a waste heat boiler (not shown). If the liquid phase component is large, there is a risk that the melt may adhere to the inner surface of the throat portion 5B of the granulator 5, cause growth, and cause coating problems. Therefore, in such a case, the throw section 5
Air, which is lower temperature than the pellet and whose flow rate is adjusted by the damper 12, is introduced in the swirling direction through the branch conduit 9C into the armhole part 5C formed at the appropriate lower part of B, and the temperature at which liquid phase formation starts is reached around the inner surface of the throw part. By forming and maintaining the following air layer, the surface of pellets falling from the granulator is temporarily cooled and the adhesive strength weakens, so such coating
Problems can be prevented from occurring. FIG. 2 shows an embodiment in which a rotary granulator 5' is applied.

In this case, as in the first embodiment illustrated in FIG. Through,
The mixture is placed in a rotary granulator 5' maintained at a liquid phase formation temperature (approximately 1,250° to 1,350 qC), and granulated by heating, melting, and rotation of the device. The cement raw material thus formed into a pellet shape of a predetermined grain size is put into a multi-chamber fluidized bed kiln 7, where it is sufficiently retained and fired to become clinker.

An appropriate amount of the cooling air whose temperature has increased by exchanging heat with the high-temperature clinker pellets in the fluidized bed cooling device 8 is pumped from the high temperature side of the device, and is passed through the conduits 9, 90, 9A. The calcining furnace 4, the granulating device 5' and the calcining furnace 7 are connected through
A portion of the relatively low-temperature (about 200 to 300 oo) surplus air that is supplied as secondary combustion air to the furnace 7 and exhausted from the low-temperature section is used as fluidizing air for clinker etc. loaded in the kiln 7. In order to utilize the clinker, it is sent to the air chamber at the bottom of the kiln 7 via a high-temperature dust collector 10 such as a multi-cyclone and a blower pipe 9B, which removes the clinker contained therein. be pumped.

As is clear from the above description, according to the present invention, the following excellent effects can be expected.

tl} Since the cement powder raw material is granulated into pellets having appropriate dimensions and then fired, the clinker firing, which is a solid phase reaction, progresses easily.

■ Since the process of circulating pongee grain clinker as a nucleus for growing clinker grains is unnecessary, heat loss associated with the circulation of pongee grain clinker is eliminated.

(3) Since the amount of heat recovered from the clinker cooling device is utilized extremely effectively, the required amount of heat consumption can be significantly reduced.

■ The temperature inside the firing furnace is uniform and relatively low, so
The generation of harmful gases such as N*x and the burnout of the necessary lining refractories are reduced, and high-quality clinker can be obtained.

'5- Since the fluidized bed in the firing furnace and clinker cooling device is formed using pellets, the adhesion between the raw materials is weaker than in the case of fine powder, so a safe fluidized bed can be obtained. is possible.

Note that the present invention is not limited to the above embodiments, and various design changes can be made within the scope of the invention.

[Brief explanation of drawings]

FIG. 1 is a schematic overall side view of a cement powder raw material firing apparatus exemplified to explain the method of the present invention, and FIG. 2 is a side view showing the main parts of another embodiment different from FIG. 1. It is. 1... Raw material input hopper, 2A to 2E...
... Combustion exhaust gas pipe, 3A to 38, 38 ... Raw material introduction pipe, 3F ... Introduction pipe, 4 ... Temporary bran furnace, 5
, 5'... Granulation device, 6A to 6C, 6A', 6
B'... Burner, 7... Firing furnace, 8...
...Clinker cooling device, 9 to 90... Conduit for high temperature air drawn from the clinker cooling device, 10...
...High temperature dust collector, 11,12...Damper, B,,
B3~B...Blower, B2...Primary [Tosanjisangi; Q fan, C, ~C5...Cyclone, NSP...With calcining furnace Suspension type raw material ripening device. Multi' diagram Multi Z diagram

Claims (1)

[Scope of Claims] 1. A raw material preheating device, a granulation device, a calcination furnace with an independent heat source, and a clinker cooling device that combine a calcination device for powdered raw materials such as cement with a calcination furnace having an independent heat source. By heat exchange with the high-temperature exhaust gas rising through the granulation device and the combustion gas in the calcination furnace, the powdered raw material such as cement is heated in the raw material preheating device and the calcination furnace. The calcined raw material thus obtained after almost complete decarboxylation reaction is introduced into a conduit connecting the clinker cooling device and the granulation device, and the high-temperature cooling material is extracted from the clinker cooling device. The mixture is mixed with air and conveyed to the granulator while exchanging heat, and is suspended and retained in a semi-molten state in the granulator, which is maintained within a predetermined liquid phase generation temperature range, to granulate it into a predetermined amount. Only the pellets formed into pellets with a particle size of the above are charged into the firing furnace, and the clinker obtained by sufficient firing is sent to the clinker cooling device, and on the other hand, the high temperature exhaust gas discharged from the outlet of the firing furnace is And the high temperature cooling air extracted from the clinker cooling device is
A method for firing a powder raw material such as cement, which is characterized in that the raw material is introduced to the preheating device through a granulating device and a calcining furnace. 2. The cement, etc. according to claim 1, wherein the secondary air for combustion in the calciner, granulator, and kiln is high-temperature air extracted from the clinker cooling device, respectively. Method for firing powder raw materials. 3. A method for firing powder raw materials such as cement according to claim 1 or 2, characterized in that the raw material preheating device is of a suspension type, and the calcining furnace is of a spouted bed type. 4. The calcining furnace is a multi-chamber fluidized bed type, and a part of the high temperature cooling air obtained by the clinker cooling device is sent to the multi-chamber fluidized bed calcining furnace and the granulation device after dust removal, and the fluidized air is 4. A method for firing powder raw materials such as cement according to any one of claims 1 to 3, characterized in that the air is used as oxidizing air. 5 A suspension-type raw material preheating device that combines a calcination device for powdered raw materials such as cement with a calciner equipped with a spouted bed and a vortex chamber each having an independent heat source, a rotary-type granulation device, and a multi-purpose calcination device with an independent heat source. It is configured to include a chamber fluidized bed type calcining furnace and a clinker cooling device, and the powder raw material such as cement is passed through the granulation device and is heated by heat exchange with the rising high-temperature exhaust gas and the combustion gas in the calcining furnace. The decarboxylation reaction was almost completely carried out in the raw material preheating device and calcining furnace, and the calcined raw material thus obtained was charged into the rotary granulator and maintained within a predetermined liquid phase generation temperature range. In this granulator, the pellet-like raw material, which is granulated by rotating and staying in a semi-molten state and formed into a particle size of a predetermined size or more, is charged into the firing furnace and sufficiently fired. Clinker is fed into the clinker cooling device, while the high temperature exhaust gas discharged from the outlet of the kiln and the high temperature cooling air extracted from the clinker cooling device are transferred to the granulation device or/and the calcination device. A method for firing a powder raw material such as cement, characterized in that the raw material is introduced into the raw material preheating device through a furnace. 6. According to any one of claims 1 to 4, characterized in that air having a temperature suitably lower than that of the pellets to be granulated is introduced into the lower throat of the granulating device. Method for firing powdered raw materials such as cement as described.