JPS594393B2 - Cement clinker firing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cement clinker firing apparatus equipped with a calciner installed upright on the butt of a rotary kiln, and particularly to an improvement of the calciner.

Among conventional calciners, one calciner equipped with a burner and a spout area and a vortex area is disposed between a suspension preheater and a rotary kiln, and the air is extracted from the clinker cooler. The secondary air rises straight from the bottom to form a jet area, and above the jet area, secondary air is also introduced tangentially from the side to form a vortex area, and the upper part of this vortex area rises. Kiln exhaust gas is introduced through a pipe.

In such a calciner, the pressure loss in the spout area is large, so it is necessary to provide an orifice in the riser pipe. Since the rotary kiln pen iodine bath tends to occur in the rotary kiln, the operation tends to become unstable, and furthermore, alkali coating tends to occur near the orifice provided in the riser pipe, making it difficult to adjust the pressure in each gas pipeline.
Other conventional calcining furnaces are formed at the position of the riser pipe mentioned above from the end of the rotary kiln to the suspension preheater. A major advantage of a rotary kiln with a preheater is that it can be easily realized by partially modifying the final stage cyclone.

However, after lever modification, the air volume must be increased to accommodate the increased kiln burnout rate. Considering the power loss of the blower, there is a limit to this increase in air volume. Therefore, the gas led to the calciner tends to have a high proportion of kiln exhaust gas with low oxygen content, and there is a risk that the combustion oxidation reaction of the fuel in the calciner will not take place sufficiently and a large amount of carbon monoxide will be generated. It was hot. Moreover, this phenomenon is exacerbated when the temperature of the secondary air is low. The generation of carbon monoxide increases heat consumption as it is a reaction process to carbon dioxide and also increases the coating growth rate due to secondary combustion in the suspension breaker, preventing cyclone blockage. This must be avoided since it can cause problems and make stable operation for long periods of time difficult. Additionally, in this case, it was necessary to increase the size of the board firing furnace. The main object of the present invention is to solve the above-mentioned problems by realizing a calcining apparatus that can carry out the combustion oxidation reaction of fuel to a sufficiently high degree in a compact calcining furnace.

The present invention is a cement clinker firing apparatus comprising a calcining furnace with a hole installed upright at the end of a rotary kiln, and a chute through which raw materials are dumped from a second stage cyclone from below a suspension preheater connected to the calciner. A kiln exhaust gas injection port is provided in the lower part of the calcining furnace so as to form a first jet area, and a throttle part is provided in the furnace body above the first jet area, and a throttle part is provided in the furnace body above the first jet area. Therefore, a second
A jet area is formed in the calciner, and an injection port for fuel from a burner and an intake port for combustion air for the fuel are arranged in close enough proximity to each other to carry out a combustion oxidation reaction of the fuel. The raw material input port of the input chute is provided close to and below the constriction part forming the second spout area, so that the raw material is dispersed and falls across the furnace above the first spout area. The dispersed and fallen raw materials cover the combustion zone of the fuel and form a calcining reaction space for the raw materials between the inner wall of the calciner and the calciner. A cyclone from the second stage from the bottom is selected at a position shifted from directly above the exhaust gas injection port, and is below the raw material input port and above the fuel injection port and the combustion air intake port. The raw material inputting port of the other raw material inputting chute is provided so that the raw material reaches a position near the rotary kiln which is far away from the rotary kiln in the longitudinal direction of the rotary kiln on the rotary kiln bottom side of the first spout area. This is a cement clinker firing device characterized by:

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a system diagram of a cement clinker firing apparatus according to an embodiment of the present invention. The calcining furnace 10 is led between the suspension preheater 20 and the rotary kiln 31 and is placed upright directly above the rotary kiln butt 33 with the throat portion 13 interposed therebetween. The raw material powder is introduced into the duct 21 as shown by the solid line arrow, and is blown up by the hot gas from below, collected by the heat exchange hole cyclone 22, and falls to the lower stage. After going through this process, duct 23→
Cyclone 24 → branch duct 25 → cyclone 26a and cyclone 26b, resulting in 600 to 700
It is preheated to about ℃, and the limestone in the raw material is 5 to 10%.
decarboxylated to a certain extent. The raw material powder from the cyclone 26a is introduced to the calciner 10 via the chute 27, and the raw material powder from the cyclone 26b is introduced to the calciner 10 via the chute 28, where they are almost completely decarboxylated. The raw material calcined in this way reaches the cyclone 30 through the duct 29 together with the exhaust gas, where it is collected and sent to the rotary kiln 31. In the rotary kiln 31, the raw material is fired by the burner 32 to become clinker, and is cooled by the clinker cooler 40 to become a product. The path of hot gas is indicated by a dashed arrow.

The combustion exhaust gas at a temperature of about 900 to 1100°C from the raw material inlet side of the rotary kiln 31, that is, from the rotary kiln bottom 33, passes through the throat part 13 and reaches the bottom of the calciner 10, and is then evacuated from the clinker cooler 40 at a temperature of 600 to 800°C.
The secondary air for combustion, which is at a high temperature of about 100 liters, passes from the dust chamber 50 through the secondary air duct 51 and reaches the calciner 10. Calcining furnace 1
The hot gas from 0 flows through the duct 29 → cyclone 30 → branch duct 25 - cyclone 26a and cyclone 26b.
→ Duct 23 → Cyclone 24 → Duct 21 → Cyclone 22, the powder exchanges heat with the raw material powder, and is induced to be discharged from the blower 60 via the electric precipitator 61. FIG. 2 shows a longitudinal section of the calcining furnace 10 according to the present invention, FIG. 3 shows a plane of the calcining furnace 10, and FIG. 4 is a cross-sectional view taken along the line -2 in FIG.

Referring to these drawings, the calcining furnace 10 includes a lower inverted conical part 71 connected to the fixed throat part 13 at the upper part of the rotary kiln butt 33, a lower cylindrical part 72, an intermediate constricted part 73, and an upper cylindrical part. 74 and the upper constriction part 75 are arranged upright in series in this order. A plurality of burners 76 that inject fuel into the furnace are circumferentially spaced apart from each other in the lower inverted conical portion 71 and the lower portion of the lower cylindrical portion 72 . A secondary air duct 51 is connected to the lower part of the lower cylindrical portion 72 in the intake direction, and is connected to the secondary air duct 51 above the fuel injection port 96 of the burner 76 and close to the secondary air intake port JMOV. 27 raw material input ports 7a are provided. Further, the chute 2 is located close to the bottom of the intermediate constriction portion 73
Eight raw material input ports 90 are provided. Burner 76 may include a primary air blow tube. FIG. 51 is a partially cutaway vertical cross-sectional view of the calcining furnace 10, and FIG. 52 is a cross-sectional view taken along section line A-B-C-D in FIG. 51.

The chute 27 and 28 are respectively attached to the calciner 10 so as to direct the raw material toward the axis of the calciner 10, that is, in the radial direction. Exhaust gas from the rotary kiln 31 draws a smooth curve as indicated by a broken line arrow 91 from the rotary kiln tail 33, reaches the throat portion 13, and rises within the throat portion 13.

Therefore, within the throat portion 13, the kiln exhaust gas has a velocity distribution 92. This velocity distribution 92 has a maximum gas flow velocity at a position 94 that is farther away from the rotary kiln 31 in the longitudinal direction of the rotary kiln 31 toward the rotary kiln bottom 33 side (to the left in FIG. 5) than the vertical axis of the throat portion 13. has. The kiln exhaust gas is injected into the calciner 10 from the kiln exhaust gas injection port 80 to form a first jet area 93.

The exhaust gas from the rotary kiln 31 is directed around the first spout area 93 above the lower inverted conical part 71 by a broken line arrow 8.
1, a vertically swirling vortex is formed in an annular shape along the inner wall. Secondary air from the duct 51, which is tangentially introduced as indicated by a broken line arrow 79, swirls horizontally along the inner wall of the calciner 10. The raw material from the raw material input port 78 is
It is injected from above with a relatively large downward inertia force than the secondary air from intake ports J and V.

Then, the raw material rotates approximately half a rotation in the horizontal direction within the calciner 10 due to the swirling flow 79 of the secondary air, and reaches the maximum kiln exhaust gas flow velocity position 94 due to inertial force. Therefore, the raw material is blown up into the calciner 10 by the kiln exhaust gas,
The raw material is prevented from descending within the first spout area 93. Therefore, the raw material is prevented from passing through the rotary kiln 31. Further, the rise of the secondary air is suppressed by the raw material from the raw material input port 78, and a horizontal swirling flow of highly concentrated secondary air is formed near the furnace wall of the inverted conical portion 71 at the bottom of the hole. Fuel is injected from the burner 76 into this high concentration secondary air swirl flow to form a combustion zone 76a. The raw material flows into the part where the horizontal swirling flow of secondary air comes into contact with the rising jet of kiln exhaust gas and the rising speed is slow, so the combustion zone 76a is aligned with the dashed-dotted line 8.
3, and thus a calcining reaction space 82 is formed. Therefore, the raw material seals the combustion zone 76a against the kiln exhaust gas and enables stable and rapid combustion oxidation of the fuel. Since the raw material is uniformly mixed with secondary air and comes into contact with the flame, it is efficiently calcined and immediately absorbs the combustion heat of the fuel. Therefore, the furnace wall does not require any special refractory material because the holes are kept at a relatively low temperature without causing local heating, and the amount of NOx generated is reduced. Calcining reaction space 82
The raw material calcined to a desired decarboxylation rate rises while rotating horizontally within the lower cylindrical portion 72.

The kiln exhaust gas injected from the exhaust gas injection port 80 is throttled by the intermediate throttle section 73, and a vortex region 84 that swirls in the vertical direction is formed below the intermediate throttle section 73. A second jet area indicated by a broken line arrow 95 is formed by the intermediate throttle part 73, and a swirling area 85 is formed between it and the lower inner wall of the upper cylindrical part 74. The raw material inputted from the raw material input port 90 with a relatively small downward inertia force is throttled as described above and dispersed across the central flow of the kiln exhaust gas where the gas flow rate is relatively high.

Therefore, the downward inertial force of the raw material is weakened. Therefore, the raw material descends within the first spout area 93 and reaches the rotary kiln 31.
This prevents short passes. In addition, the raw material is dispersed while vigorously mixing with the central flow of the kiln exhaust gas.
descends downwards from Thus, the raw material from the raw material input port 90 covers the combustion zone 76a as described above together with the raw material from the raw material input port 78, and is efficiently calcined in the calcining reaction space 82. Further, even if the relatively fine raw materials are blown upward by the central flow of the kiln exhaust gas, they are sufficiently calcined within the swirling region 85 as will be described later. The raw material sufficiently calcined in the calcining reaction space 82 is carried upward by the central flow of the kiln exhaust gas and guided into the swirling area 85 .

By appropriately selecting the size of the intermediate constriction section 73 and, therefore, the velocity of the gas rising through the second jet area 95, only CaO etc. with low specific gravity decomposed in the lower cylindrical section 72 are allowed to move upward, and the remaining It is possible to allow only CacO3, which has a high specific gravity for decomposition, to descend to the lower cylindrical portion 72 as indicated by the solid line arrow 86 and be reheated, and the raw material can be completely decomposed. The upper constriction part 75 provided at the upper part of the upper cylinder part 74 is for forming a mixing space within the upper cylinder part 74 between the upper constriction part 75 and the intermediate constriction part 73 .

Even if the kiln exhaust gas that has risen through the intermediate throttle section 73 to form the second jet area 95 contains unburned matter, the unburned matter is 2
It mixes sufficiently with the horizontal swirling flow containing secondary air, and combustion can be completed in this mixing space. Therefore, if secondary combustion cannot be prevented, especially the second stage cyclone 26a from the bottom.
, 26b is prevented from being blocked by the anolecari coating. The air volume of the calcining furnace 10 can be easily adjusted to an optimum value by a damper (not shown) installed in the secondary air duct 51.

Although the secondary air was introduced tangentially into the calciner 10 through its intakes J and V, in other embodiments it could be, for example, radially directed, i.e. towards the axis of the calciner 10. Good too.

Even in such a case, the calcination reaction space 82 is configured to be located at a position offset from directly above the kiln exhaust gas injection port 80, so that the formation of the calcination reaction space 82 is prevented by the jet of kiln exhaust gas. so that it cannot be disturbed or disturbed. Room temperature atmosphere may be introduced instead of the secondary air from the clinker cooler 40. Although the secondary air intake port JMOV and the burner 76 may be arranged individually as shown in the figure, or may be arranged concentrically, it is important that the fuel from the burner 76 is supplied to the secondary air. Therefore, the secondary air intake port JMOV and the burner 76 must be placed sufficiently close to each other so that combustion oxidation occurs.

As another embodiment of the present invention, a single cyclone is provided as the second stage cyclone from the bottom instead of the two cyclones 26a and 26b, and the collected raw material is transferred to the intermediate squeezing part 73.
Alternatively, the ball may be thrown close to and below the intermediate constriction portion 73.

As described above, according to the present invention, the raw material collected by the second stage cyclone from the bottom is introduced into the calcining furnace near the constriction part and below the constriction part, whereby the raw material is transferred at a relatively high speed. Since it crosses the central flow of the kiln exhaust gas with a high velocity, the downward inertial force of the raw material is weakened and the raw material is prevented from passing through the rotary kiln.

Therefore, the gas velocity from the kiln exhaust gas injection port can be kept relatively low, reducing pressure loss, and since undecomposed raw materials are not introduced into the rotary kiln, the rotary kiln can be operated stably. can. Further, the center flow of the kiln exhaust gas collides with the raw material that crosses the center flow, reducing the upward velocity, thereby preventing the center flow of the kiln exhaust gas from blowing through the calciner. Thereby, the height of the calciner can be reduced. Further, since the kiln exhaust gas flows close to the combustion zone, NOx in the kiln exhaust gas is reduced to N2 by the hydrocarbons and raw materials in the fuel burned in the combustion zone, thereby suppressing the generation of NOx. Furthermore, in the calciner, a reaction space for calcining the raw material is formed between the inner wall of the calciner and the inner wall of the calciner, covering the combustion zone of the fuel at a position offset from directly above the kiln exhaust gas rising from below. Combustion is carried out safely and quickly h1, and the combustion heat is efficiently transmitted to the raw material. Therefore, it is possible to make the calciner smaller and reduce equipment costs, and it is also possible to reduce the number of heating elements in the calciner, and it also solves the issue of installation space with the suspension preheater. It becomes easier to do. In particular, according to the present invention, a raw material input port for another raw material input chute from the second stage cyclone from the bottom is provided below the raw material input port and above the fuel injection port and the combustion air intake port. This raw material inlet is arranged so that the raw material reaches a position near the rotary kiln's end side in the rotary kiln's first spout area, which is far away from the rotary kiln in the longitudinal direction of the rotary kiln. Therefore, it becomes possible for the raw material to reach a portion of the kiln exhaust gas where the flow velocity is high. This prevents the raw material from passing through the rotary kiln.
At the same time, the flow rate of kiln exhaust gas can be lowered depending on the raw material. This prevents the kiln exhaust gas from blowing through the calciner and achieves good heat exchange efficiency.

[Brief explanation of drawings]

FIG. 1 is a system diagram of a cement clinker firing apparatus according to an embodiment of the present invention, FIG. 2 is an enlarged vertical sectional view of the calcining furnace 10 shown in FIG. 1, and FIG. 3 is a plan view of the calcining furnace 10. 4 is a sectional view taken from the section line - in FIG. 2, FIG. 5 1 is a partially cutaway longitudinal sectional view of the calciner 10, and FIG. −
It is a cross-sectional view along B-C-D. 10...Calcination furnace, 13...Throat part, 20...Suspension preheater, 26a
,26b゜゜゜・・・Second cyclone from the bottom, 26
, 28...゛゜shoot, 31...Rotary kiln, 33...Rotary kiln butt 40.
... Clinker cooler, 51 ... Secondary air duct, 71 ... Lower inverted conical part, 72 ...
...Lower cylindrical part, 73...Middle drawing part, 74...
... Upper cylindrical part, 75 ... Upper drawing part, 76.
... Burner, 76a ... Heat-burning zone, 77.
...Secondary air intake port 78, 90...Raw material input port, 80...Kiln exhaust gas nozzle port, 82.
...Calcination reaction space, 93...First jet area, 95...Second jet area, 96...Fuel injection port.

Claims (1)

[Claims] 1. In a cement clinker firing apparatus, a chute for feeding raw material from a second stage cyclone from below a suspension preheater is connected to a calcining furnace formed upright at the end of a rotary kiln. 1st at the bottom of
A kiln exhaust gas injection port is provided so as to form a jet area, and a constriction part is provided in the furnace body above the first jet area, and this constriction part allows a second A jet area is formed in the calciner, and an injection port for fuel from a burner and an intake port for combustion air for the fuel are arranged sufficiently close to each other to carry out a combustion oxidation reaction of the fuel, The raw material input port of the input chute is provided close to and below the constriction part forming the second jet area, so that the raw material falls in a dispersed manner across the furnace above the first jet area,
The dispersed and fallen raw materials cover the combustion zone of the fuel and form a calcining reaction space for the raw materials between the inner wall of the calciner, and this calcining reaction space is located at the bottom of the calciner. A cyclone from the second stage from the bottom is selected at a position offset from directly above the kiln exhaust gas injection port, and is below the raw material input port and above the fuel injection port and the combustion air intake port. A raw material input port of another raw material input chute is provided so that the raw material reaches a position near a position remote from the rotary kiln in the longitudinal direction of the rotary kiln on the bottom side of the rotary kiln in the first jet area. A cement clinker firing device characterized by: