JPH0143697B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a calcination device for cement raw material powder.

Modern cement calcining equipment is constructed by arranging a calcining device with an independent heat source between a raw material preheating device and a calcining furnace.

Figure 1 shows the preheating and
This is a diagrammatic system diagram showing the steps of calcination, firing, and cooling. The solid arrows in the diagram indicate the flow of hot air, and the dashed arrows indicate the flow of raw material powder. The outline of the equipment consists of a raw material preheating device 1 consisting of cyclones C ₁ to _{C 3} and a duct 7, etc., a calcining furnace 2 with an attached separation cyclone C ₄ , a calcining furnace 3 such as a rotary kiln, and a clinker cooler 4. , the cement raw material powder supplied from the raw material input chute 5 sequentially descends through each of the first to third cyclones C ₁ to C ₃ , and then passes through the firing furnace 3 .
The high-temperature exhaust gas from the calcining furnace 2 is sucked by the induced draft fan 8 and rises inside the raw material preheating device 1, so that the raw material powder and the high-temperature gas are mixed in the duct 7 and the cyclones _C1 to _C3 . Heat exchange and separation are repeated. The preheated raw material powder is introduced from the raw material preheating device 1 into the calcining furnace 2 through the preheated raw material chute 14. The calcining furnace 2 has an inverted conical shape with its lower end gradually decreasing in cross section toward the bottom, and is connected to the calcining furnace 3 via an inlet end cover 12, so that the raw material supplied to the calcining furnace 2 The powder is mixed and stirred in the calcination furnace 2 by exhaust gas from the calcination furnace flowing upward from below to form a spouted bed. On the other hand, the high-temperature combustion secondary air introduced from the clinker cooler 4 through the bleed duct 13 into the calciner 2 and the fuel supplied together with the combustion primary air from the burner 6a generate fuel in the spouted bed. Combustion occurs, and the raw material powder is calcined by receiving the combustion heat and the heat of the firing furnace exhaust gas. The calcined raw material powder enters the separation cyclone C ₄ attached to the calciner 2 from the calciner 2 together with the combustion gas and is separated, and then enters the calciner 3 from the calciner raw material chute 15 through the inlet cover 12. The clinker enters the kiln, undergoes necessary heat treatment in the kiln 3 by the combustion heat of fuel supplied from the burner 6b installed at the lower end of the kiln 3, becomes clinker, and is then cooled by the cooler 4. Note that air for cooling the clinker is supplied by a forced air blower 10, and a part of the air heated by exchanging heat with the clinker is distributed to the calciner 2 and the calciner 3 as secondary air for combustion. However, excess air is exhausted by the induced draft fan 9. The clinker discharged from the clinker cooler 4 is then conveyed to the next process by a conveyor 11.

This type of calcination furnace is installed directly above the inlet end cover of the calcination furnace and forms a spouted layer of raw material powder inside the furnace by exhaust gas from the calcination furnace introduced from below. Since the structure is simple and easy to arrange, there are various advantages such as low pressure loss and low power consumption of the induced draft fan 8, easy operation and maintenance, and less space required for the structure. There are the following problems.

In other words, the exhaust gas from the calciner, which is introduced from the lower end of the calciner, is essential for this type of calciner in order to form a spouted layer of raw material powder in the calciner, but the exhaust gas from the calciner generally contains oxygen. It mixes with the combustion air introduced into the calciner 2 from the clinker cooler 4 through the bleed duct 13 in the calciner, reducing the average oxygen concentration of the gas in the calciner. Since the fuel supplied to the furnace is combusted under such a low oxygen concentration, the combustibility of the fuel is inhibited.

In addition, since the entire amount of the preheated raw material to be calcined from the raw material preheating device is supplied to the calcining furnace to form a spouted bed, and the fuel is combusted within the spouted bed, the amount generated by combustion is Heat is immediately transferred to the raw material powder, and the temperature inside the calciner combustion chamber is close to the equilibrium temperature determined from the heat balance in the combustion chamber, and the temperature is relatively low at around 900℃ except near the burner installation area. is maintained.

Maintaining the inside of the calciner at a low temperature in this way is effective in sufficiently protecting the calciner wall from a thermal standpoint, but as well as the low oxygen concentration mentioned above, the It inhibits flammability. Therefore, in order to ensure sufficient combustion, it is necessary to introduce considerably more combustion air into the calciner than is theoretically required, which leads to an increase in fuel consumption in the calciner. I'm there. In particular, when solid fuel such as pulverized coal is used as a fuel for calcining, the combustion time is longer than that of liquid fuel such as heavy oil. It is necessary to increase the furnace capacity, leading to an increase in equipment costs. Furthermore, since the degree of progress of the calcination reaction of the raw material powder in the calcination furnace is mainly controlled by the ambient gas temperature, if the inside of the calcination furnace is maintained at a low temperature, the temperature of the raw material powder particles will be sufficiently reduced to the center of the raw powder particles. Since the calcination reaction cannot proceed, the calcination rate of the raw material powder discharged from the calcination furnace to the calcination furnace has not yet been fully satisfied.

The present invention has been made to solve the above problems, and is a short circuit in which one end is opened to the inlet cover of the calcining furnace and the other end is opened only between the upper part of the calcining furnace and the exit of the separation cyclone. By providing a duct, the average oxygen concentration in the combustion section of the calciner can be maintained high, and by connecting the preheated raw material chute from the raw material preheating device to the calciner and the short-circuit duct, the combustion inside the calciner can be maintained. It is designed to raise the temperature of the area appropriately.

The embodiments shown in the drawings will be described below. In FIG. 2, the calcining furnace 2 has a cylindrical vertical shape in this configuration example, and is composed of a lower combustion chamber 2a and an upper mixing chamber 2b that communicate with each other with a constriction part 2c as a boundary, and the lower end of the combustion chamber 2a. The cross section is gradually reduced downward to form an inverted cone-shaped portion, and the opening 2d is connected to the firing furnace 3 via the inlet end cover 12. or,
A bleed air duct 13 that guides high-temperature bleed air from the clinker cooler 4 as secondary air for combustion in the lower side wall of the combustion chamber 2a is provided with an opening 2 in the radial or tangential direction.
In the vicinity where the ceiling wall of the bleed duct 13 joins the side wall of the combustion chamber 2a, the combustion chamber 2a
A burner 6a is installed that blows fuel together with primary air toward the high-temperature bleed air flowing into the combustion chamber 2a. A preheating feedstock chute 14a from the cyclone C ₃ of the feedstock preheating device is connected pointing towards the combustion zone, while the mixing chamber 2
The combustion gas outlet 2f of b is connected to the separation cyclone _C4 .

Reference numeral 16 denotes a short-circuit duct, which is disposed so that one end thereof is opened to the inlet end cover 12 and the other end thereof is opened to the mixing chamber 2b of the calcining furnace. This short-circuit duct 16 is provided with a damper 16a for adjusting air volume, and is connected to a preheated raw material chute 14b from a raw material preheating device. This preheated raw material chute 14b is a branch of the preheated raw material chute 14 from the cyclone _C3 of the raw material preheating device, and the branched part 1
4d is provided with a distribution valve 14c so that the amount of preheated raw material supplied to the calcining furnace 2 and the short-circuit duct 16 can be adjusted as appropriate. Further, in this embodiment, one end of the short circuit duct 16 is connected to the upper part of the calcining furnace, but the separation cyclone
C ₄ or a duct between the calciner 2 and the separation cyclone C ₄ .

With this configuration, a part of the calciner exhaust gas with a low oxygen concentration is directly attracted to the upper part of the calciner or the downstream side of the calciner through the short-circuit duct 16 from the inlet end cover 12, and a jet flow is generated in the combustion chamber 2a of the calciner. Since only the amount of gas necessary for layer formation is introduced, the average oxygen concentration of the gas supplied to the combustion section in the calciner can be increased. In other words, 80 to 50% of the firing furnace exhaust gas is sent to the combustion chamber.
Furthermore, by drawing the remaining 20 to 50% to the short-circuit duct, the average oxygen concentration of the gas supplied to the combustion section can be increased by about 2 to 5%, compared to 11 to 13% according to the conventional method. At this time, the calciner exhaust gas passing through the calciner combustion section has pressure loss due to acceleration and deceleration when passing through the calciner lower end throttle 2d, energy for forming a spouted layer in the lower part of the calciner, and energy between the combustion chamber and the mixing chamber. Since there is resistance when passing through the intermediate throttle 2c, even if the cross-sectional area of the short-circuit duct is small, it is possible to attract a sufficient amount of calcining furnace exhaust gas.
The quantitative proportion of the firing furnace exhaust gas passing through 6 can be adjusted by damper 16a.

Furthermore, since only a portion of the preheated raw material to be calcined from the raw material preheating device is supplied to the combustion chamber 2a, the temperature within the combustion chamber 2a can be increased compared to the case of the conventional structure. The temperature inside the combustion chamber 2a is adjusted by the distribution ratio of the preheated raw material to the combustion chamber 2a and the short-circuit duct 16, but it is generally 950~
It is appropriate to set the temperature to 1100°C, preferably 1000 to 1050°C, and for this purpose, 90 to 50% of the preheated raw material from the raw material preheating device is sent to the combustion chamber 2a, and the remaining 10 to
50% is distributed and supplied to the short circuit duct 16.

As the average oxygen concentration of the gas supplied to the combustion section increases and the combustion temperature within the combustion chamber increases, sufficient combustion can be achieved with a small amount of excess air during combustion in the calciner. In addition, due to the large temperature difference between the combustion gas and the feed material, the combustion heat of the fuel can be effectively and quickly transferred to the raw material powder, so the amount of fuel consumed in the calciner can be reduced. .

Furthermore, even when solid fuel such as pulverized coal is used, the required combustion time is shortened due to the increase in combustion temperature, so the volume of the calciner can be selected to be small.
By significantly improving the combustibility of the fuel within the combustion chamber, it becomes possible to use low-grade fuels such as heavy oil, coal slag, and petroleum coke.

Furthermore, as the temperature inside the combustion chamber 2a increases, the raw material powder supplied from the preheated raw material chute 14a to the combustion chamber 2a quickly completes the calcination reaction in the combustion chamber 2a, so that the raw material powder is not fired from the calcination furnace. The calcination rate of the raw material powder discharged into the furnace is also significantly improved.

Furthermore, since a large amount of preheated raw material is injected into the short-circuit duct compared to the calorific value of the passing gas, the short-circuit duct is maintained at a sufficiently lower temperature than the calciner combustion section, and the wall of the short-circuit duct is hardened by the raw material powder. There is no need to worry about tying.

In these calciner structures, the cross-sectional shape of the calciner, the number of bleed ducts, the type, number, and arrangement of the fuel supply device, and even the type of fuel can be freely selected according to the purpose, and the material preheating device The type (cyclone type, tower type, etc.), number of series, number of stages, number of cyclones constituting each stage, etc. are not limited at all.

For example, it is also possible to arrange a plurality of lines of raw material preheating devices, supply the preheated raw materials from some of the series to the combustion section of the calciner, and supply the preheated raw materials from the remaining series to the short-circuit duct. Furthermore, according to the structure of the present invention, by adjusting the opening degree of the damper 16a of the short-circuit duct, it is possible to adjust the amount of exhaust gas from the firing furnace passing through the lower end throttle 2d of the calciner, as well as the pressure loss. The ratio of the firing furnace exhaust gas flowing into the cooler bleed air and the cooler bleed air can be adjusted, and the air volume adjusting damper normally installed in the cooler bleed air duct 13 can be omitted.

The present invention is constructed as described above, and is a method of calcination in which a spouted layer of raw material powder is formed in the furnace by the exhaust gas from the firing furnace, which is installed directly above the inlet end cover of the firing furnace and introduced from below. When using the furnace, only a portion of the exhaust gas from the firing furnace is introduced into the combustion section of the calciner, and only a portion of the preheated raw material from the raw material preheating device is supplied to the combustion section, and the rest of the exhaust gas is introduced into the combustion section of the calciner. The exhaust gas and the preheating raw material are to be combined on the downstream side of the calciner combustion part through the short-circuit duct, and the respective ratios of the calciner exhaust gas and the preheating raw material to the calciner combustion part and the short-circuit duct are adjusted. Since it is designed to be able to be distributed, it appropriately increases the oxygen concentration in the combustion gas in the calciner combustion section and the temperature in the combustion chamber, thereby improving the combustibility of the fuel and transferring heat from the combustion gas to the raw material powder. This promotes the transmission and calcining reaction of the raw material powder, reduces fuel consumption and downsizes equipment, and allows the use of low-grade fuel.

[Brief explanation of drawings]

FIG. 1 is a diagrammatic system diagram showing a conventional cement clinker manufacturing process, and FIG. 2 is a schematic diagram showing an embodiment of the present invention. 1... Raw material preheating device, 2... Calcining furnace, 3... Calcining furnace, 4... Clinker cooler, 6... Fuel supply device, 12... Inlet end cover, 13... Air bleed duct,
14a, b...Preheating raw material chute, 14c...Distribution valve, 14d...Branch portion, 16...Short circuit duct,
C ₄ ... Separation cyclone.

Claims (1)

[Claims] 1 A calcination furnace installed between a raw material preheating device and a calcination furnace and equipped with a separation cyclone, the lower end of which is constricted into an inverted conical shape and connected to the inlet end cover of the calcination furnace. At the same time, in addition to installing a fuel supply device on the lower side wall, a bleed air duct from a clinker cooler is connected, and in a cement raw material powder calcination device whose upper end is connected to a separation cyclone, one end is connected to the inlet end cover. A short circuit duct is provided which is open and the other end is opened only to the upper part of the calciner, the separation cyclone, or the duct connecting the calciner and the separation cyclone, and the preheated raw material chute from the raw material preheating device is connected to the calciner and the separation cyclone. A calcination device for cement raw powder powder, which is characterized in that each is connected to a short-circuit duct.