JPS62283850A - Powder raw material burning apparatus - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a firing apparatus for firing powder raw materials such as cement raw materials and limestone. The present invention relates to a system in which the sensible heat of exhaust gas from a multi-stage heat exchange unit is efficiently recovered and used in a waste heat boiler for power generation, and the powder raw material can be preheated in an optimal state.

(Prior art) Conventionally, for example, a sintering device for powdered raw materials for cement has a second
There are devices configured as shown in FIGS.

FIG. 2 shows a first conventional example.

In the figure, 1 is a rotary kiln-type firing furnace that obtains talin power by firing cement powder raw materials, 2 is a talin cooler that cools the talin power discharged from the kiln 1 by air flow, and 3 is the above-mentioned kiln l. 4 is a raw material supply device such as a screw conveyor that supplies the powder raw material to the preheating device 3.

The tarinka outlet side of the firing furnace 1 is connected to the cooler 2 by a firing shade 6 equipped with a fuel supply device 5a. On the other hand, a forced air blower 7 is connected to the cooler 2 to supply air for Tallinn force cooling to the cooler 2, and an exhaust fan 8 is also connected to discharge a part of high-temperature air from the cooler 2. be done.

On the other hand, the preheating device 3 has four stages of heat exchange units hH+ to H4 which are end-shaped in the vertical direction and connected to each other, and each of these heat exchange units is connected to a cyclone CI which is a powder collector.
``'C4, and a gas duct and a raw material chute connected to each of these cyclones.In other words, the gas inlet of each cyclone and the gas outlet of the other cyclone located below this cyclone are They are connected by gas ducts lla to llc, respectively.Furthermore, the entrance end cover 12 of the firing furnace 1 and the gas inlet of the cyclone C4 located at the lowest stage are connected by a gas duct 13. The gas outlet of the cyclone C1 is connected to the exhaust gas induction conduit!L machine 14 by an exhaust gas duct) 15.

The powder discharge port of each cyclone and the gas inlet side gas duct of another cyclone located below this cyclone are connected by raw material shoes 17a to 17c, respectively. Further, the powder discharge port of the cyclone C4 in the lower stage is connected to the inlet end cover 12 of the firing furnace l by a raw material chute 18. Furthermore, the first feeder 4 of the raw material feeder 4 is connected to the gas duct 11a on the gas inlet side of the uppermost cyclone C1.
a is connected by a first supply chute 19.

Further, a calciner 21 equipped with a fuel supply device i5b is interposed between the gas inlet side gas duct 13 of the lowermost cyclone C4 and the raw material chute 17c from the cyclone C3 located above the cyclone C4. will be established. This calciner 21 heats the powder raw material with the exhaust gas from the calciner 1 and the combustion gas obtained by burning the fuel, and in order to supply air for combustion of the fuel, this calciner 21 and cooling@
2 are connected by an air bleed duct 22. 23 is a finished product conveyor, which transports the finished product cooled by the cooler 2 to the next process.

Next, the operating state of the cement powder raw material firing apparatus will be explained. The powder raw material sent to the preheating device 3 by the raw material supply device 4 is fed to the supply chute 1 from the raw material supply device 4.
9 to the gas duct 11a, and this gas duct h
The uppermost cyclone C, accompanying the updraft within lla,
sent to.

Then, it descends sequentially through the cyclone 70 days 02 + C3 and the raw material chutes 17a and L7b, during which time it is sequentially preheated by hot air rising through the gas ducts lla, llb, and llc. This preheated powder raw material is passed from the third stage cyclone C3 to the calciner 2 through the raw material chute 17c.
1. On the other hand, fuel supplied from the fuel supply device 5b is combusted in the calciner 21 using high-temperature combustion air induced from the cooler 2 via the bleed duct 22. The heat from this fuel combustion and the calcining furnace 21 from the calcining furnace 1
Due to the high temperature exhaust gas drawn into the calciner 21
The powdered raw material is calcined in the chamber. The calcined powder raw material enters the cyclone C4 from the calciner 21 through the gas duct 13 together with the exhaust gas, and then is introduced into the calciner 1 from the raw material chute 18 through the entrance cover 12 of the calciner 1.

High-temperature air from a cooler 2 and firing fuel from a fuel supply device 5a are introduced into the firing furnace 1, and the talin force formed by firing under high temperature enters the cooler 2 and is cooled. Ru. In this case, the air for Tallinn force cooling is forced air J
It is supplied to the cooler 2 by a7 and heated by heat exchange with the tarinka. A part of this heated high-temperature air is recovered as combustion air in the calciner 21 and the calciner 1, and the excess air that is not recovered is exhausted by exhaust air Ja8 (in the figure, the gas flow is indicated by the solid arrow). (the flow of the powder raw material is indicated by the dashed arrow).

The temperature of the exhaust gas from the uppermost cyclone C1 in the preheating device 3 depends on the properties of the raw material and the presence or absence of the calciner 21, but in the preheating device 3 with four heat exchange units, the temperature is 35.
The temperature is about 0°C to 400°C, and a considerable amount of heat energy still remains. Therefore, attempts have been made to utilize this exhaust gas sensible heat more effectively.

That is, an exhaust heat boiler 27 is interposed in the middle of the exhaust gas duct 15 as equipment for utilizing exhaust heat of exhaust gas.

Furthermore, thermal economy is improved by generating heat through heat exchange with high-temperature exhaust gas and using this for power generation.

By the way, like the preheating device 3 above, there are 4 heat exchange units.
In the case of a stage or higher, the temperature of the exhaust gas from the preheating device 3 used in the waste heat boiler 27 is not so high, so the temperature and pressure of the steam generated in the waste heat boiler 27 do not rise sufficiently, and the power generation efficiency of the turbine decreases. Furthermore, since the exhaust gas from the preheating device 3 is generally used as a ripening material for drying raw materials, only the surplus can be used for heating in the waste heat boiler 27, and as a result, there is a shortage of available gas sensible heat. However, the efficiency of power generation turbines is not high enough.

Therefore, in order to compensate for the lack of heat quantity of the exhaust gas used in the exhaust heat boiler 27, various means have been proposed in the past. A conventional example provided with each of these means will be explained with reference to FIGS. 3 and 4. In addition, Figures 3 and 4 are the second and third figures, respectively.
A conventional example is shown, and both of these conventional examples have the same basic configuration as the first conventional example. Therefore, the same components are given the same reference numerals, and the explanation thereof will be omitted.

FIG. 3 shows a second conventional example, which is disclosed in Japanese Patent Laid-Open No. 59-59243 filed by the present applicant.

That is, the raw material supply device 4 is provided with a first supply@4a and a second supply machine 4b, and the first supply machine 4a is connected to the first supply chute 19 to the gas duct ()lla on the gas inlet side of the uppermost cyclone C1. By! tc continued. On the other hand, the second supply device 4b is connected to the gas inlet side gas duct 11b of the second stage cyclone C2 from the top through second supply chutes 2 and 9.

A portion of the powdered raw material in the raw material supply device 4 is sent to the gas duct) lla that constitutes the uppermost heat exchange unit H1, and the rest skips the uppermost heat exchange unit H+ and constitutes the next heat exchange unit H2. (hereinafter referred to as the raw material short-circuit supply method). In this case, the thermal efficiency in the preheating device 3 decreases corresponding to the decrease in the raw material powder supplied to the uppermost heat exchange unit H1. As a result, the temperature of the exhaust gas finally discharged from the preheating device 3 increases, thereby compensating for this apparent exhaust gas deficiency.

FIG. 4 shows a third embodiment, which is shown in Japanese Patent Application Laid-Open No. 59-59241 filed by the same applicant.

That is, the middle part of the gas discharge port side gas duct 11C of the lowermost cyclone C4 and the middle part of the exhaust gas duct 15 are connected by the short-circuit gas conduit 31.

A dust collector 32 is interposed in the middle of the short-circuit gas conduit 31, and this dust collector 32 collects powder and raw materials scattered along with the short-circuit gas flowing inside the short-circuit gas conduit 31. .

Further, the powder discharge port of the dust collector 32 is connected by a raw material chute 33 to the raw material chute 18 from the lowermost cyclone C4. Furthermore, a tamper 34 is interposed in the middle of the short-circuit gas conduit 31 on the gas discharge port side of the dust collector 32. By adjusting the opening degree of the damper 34, the amount of short-circuited exhaust gas flowing from the midway part of the preheating device 3 to the exhaust gas duct 15 can be adjusted.

Then, the hot gas extracted by short-circuiting the upper stage of the preheating device 3 from the short-circuit gas conduit 31 joins with the exhaust gas discharged from the uppermost stage cyclone C, and is guided to the waste heat boiler 27 (
(hereinafter referred to as the gas short circuit induction method). For this reason gas dak)
The hot gas extracted from the llc is not used for heat exchange with the powder raw material in the heat exchange unit located above the oil gas section, and thus maintains a high temperature. Therefore, when this is combined with the exhaust gas in the exhaust gas duct 15,
The thermal efficiency in the preheating device 3 decreases corresponding to this amount of short-circuit gas. As a result, the temperature of the exhaust gas introduced into the exhaust heat boiler 27 increases, and the obvious shortage of exhaust gas to the exhaust heat boiler 27 is compensated for.

In the second and third conventional examples described above, the exhaust gas temperature is increased at the expense of slightly sacrificing the preheating efficiency of the powdered raw material in the preheating device 3, so it is necessary to increase the amount of fuel used in the calcining furnace 1 or the calcining furnace 21 accordingly. arise. Therefore, the exhaust gas introduced from the preheating device 3 to the waste heat boiler 27 not only increases in temperature but also in quantity. In this case, the exhaust gas temperature can be adjusted by the raw material or the short-circuit amount of hot gas, so it is possible to significantly increase the recovered heat in the exhaust heat boiler 27, and the temperature and pressure of the generated steam are increased, so the turbine The power generation efficiency will be significantly improved. The increase in the amount of fuel used in the above-mentioned firing device is used to increase the amount of heat recovered in the waste heat boiler 27 and to improve the heat utilization efficiency in the power generation equipment, so the increase in the amount of fuel used in the firing device as a whole including the waste heat power generation equipment increases. energy economy can be improved.

(Problems to be Solved by the Invention) By the way, the raw material short-circuit supply method in the second conventional example,
In both of the gas short circuit induction method in the and third conventional example, the temperature of the gas introduced into the waste heat boiler 27 is increased,
Although the efficiency of the waste heat power generation equipment including the waste heat boiler 27 has been improved, there is still room for improvement in the operating state of the preheating device 3.

That is, a common problem in both conventional examples is that if the amount of raw material processed in the preheating device 3 is constant, the amount of exhaust gas passing through the preheating device 3 is almost uniquely determined. For this reason, when trying to change the temperature of the exhaust gas introduced into the waste heat boiler 27 to a desired value, the amount of passing gas cannot be adjusted to a value suitable for preheating the powder raw material in the preheating device 3.

Hereinafter, a case where the preheating device 3 is equipped with a calcining furnace 21 composed of four stages of heat exchange units will be described in more detail.

The heat is introduced from the preheating device 3 into the waste heat boiler 27 .

The temperature of the exhaust gas is determined by the heat resistance limit determined by the material of the wood pipes in the boiler, the steam turbine impeller, and the casing.
Between 0°C and 500°C, especially between 420°C and 4e o'
c is appropriate. For this reason, it is necessary to raise the exhaust gas temperature by 40°C to 80°C, approximately 60°C on average, compared to the first conventional example. When the preheating device 3 does not include the calcining furnace 21 or is of a five-stage heat exchange type, the exhaust gas temperature of the preheating device using a method that does not short-circuit the raw materials or gas as in the first conventional example is generally even higher. It is low. Therefore, the temperature difference needed to raise the exhaust gas introduced into the waste heat boiler 27 to the appropriate temperature becomes even larger, and the problems described below become even more pronounced.

First, in the raw material short-circuit supply method in the second conventional example, when trying to increase the temperature of the exhaust gas introduced into the waste heat boiler 27 by 80°C, 10% of the raw material supplied to the preheating device 3
%~20% is supplied from the first supply device 4a to the gas duct) 11a that constitutes the uppermost heat exchanger 2)H+, and 80%~
90% is transferred from the second feeder 4b to the second stage heat exchange unit)H
It is necessary to distribute and supply the gas to the gas duct Llb constituting the gas duct Llb. At this time, in this raw material short-circuit supply method, the calcining furnace 21
The entire amount of hot gas discharged from the firing device rises and passes through the preheating device 3, and the amount of hot gas increases as the amount of fuel used in the firing device increases.

In addition, the temperature of the exhaust gas passing through the preheating device 3 decreases in the second and third heat exchange units H2 and H3 due to the short-circuit supply of the powder raw material, but
At I, the temperature rises by 60°C. Therefore, if we focus on the pressure loss in the top stage cyclone CI, we can see that the pressure loss significantly increases not only due to a rise in the processing gas temperature, but also due to an increase in the unit processing gas amount and a decrease in the raw material concentration in the processing gas. do.

As a result, the pressure loss of the preheating device 3 as a whole increases even if the reduction in pressure loss due to the influence of the temperature drop in the second and third stage heat exchange units H2 and H3 is subtracted. Along with this,
The driving power of the exhaust gas induced draft fan 14 increases, and a portion of the extra power generated by improving the efficiency of the waste heat power generation equipment is wasted.

In addition, in the first conventional example in which the raw material is not short-circuited, the uppermost cyclone C! Also, the exhaust gas duct 15 is not lined with fireproof material. However, in the preheating device 3 using the raw material short-circuit supply method as in the second conventional example, since high-temperature hot gas flows through the exhaust gas duct 15 leading to the uppermost cyclone C1 and the exhaust heat boiler 27, both of these are lined with refractory material. It becomes necessary. For this reason, when the lining is made of refractory material, the load on the upper part of the preheating device 3 increases, which causes the disadvantage that the weight of the support bridge for the component parts of the preheating device 3 increases.

Next, in the gas short circuit induction method in the third conventional example, the temperature of the exhaust gas introduced from the preheating device 3 to the waste heat boiler 27 is increased to 8.
If you try to raise it by 0℃, the bottom heat exchange unit)
It is necessary to bleed 20% to 30% of the amount of high temperature gas of 850'C to 900C passing through the gas outlet side gas duct 1Lc of the cyclone C9 constituting H4. In this case, in the preheating device 3 above the oil position of the high-temperature gas, not only the amount of passing gas decreases, but also the gas temperature decreases.
For example, in the top heat exchange unit H+, it is 50°C to 60°C.
The temperature will drop, and the actual air volume and speed will decrease by 30% to 40%. For this reason, there is a possibility that some of the powder raw materials supplied from the raw material supply device 4 and the upper stage cyclones C, C2 to the gas ducts lla to llc cannot survive the rising gas discharged from the lower stage cyclones. In this case, the powder raw material supplied to each of the gas ducts lla to llc will fall directly into the cyclone below, which causes the disadvantage that the operating state of the preheating device 3 becomes unstable.

Furthermore, since the amount of short-circuited gas is relatively large, the dust collector 32 for collecting the powdered raw material scattered along with the short-circuited gas becomes large in size and difficult to arrange.

(Purpose of the Invention) This invention was made in view of the above-mentioned circumstances, and aims to improve the energy economy of the entire firing apparatus including the waste heat power generation equipment, and to reduce the heat passing through the preheating device. The purpose is to enable this preheating device to operate in good condition by being able to adjust the amount of gas suitable for preheating.

(Structure of the Invention) A feature of the present invention for achieving the above object is that the raw material supply device is connected to each of a plurality of heat exchange units including at least the uppermost heat exchange unit, and The middle part of the gas duct of the heat exchange unit 7) and the middle part of the exhaust gas duct are connected by a short-circuit gas conduit, and a dust collector is interposed in the middle part of this short-circuit gas conduit.

(Example) Hereinafter, an example of the present invention will be described with reference to FIG. Note that this embodiment has the same basic configuration as the first to third conventional examples. Therefore, the same parts are given the same reference numerals, and the explanation thereof will be omitted.

On the exhaust gas duct 15 from the preheating device 3, a venturi flow meter 35 and a pressure gauge 36 for exhaust gas are provided on the uppermost cyclone C1 side from the connection portion between the exhaust gas duct 15 and the short-circuit gas conduit 31. On the other hand, a thermometer 37 is provided on the exhaust gas tough) 15 closer to the exhaust heat boiler 27 than the connecting portion.

When operating this firing device, the amount of short-circuit gas extracted through the short-circuit gas conduit 31 is adjusted so that the amount of gas passing through the upper stage of the preheating device 3 is optimal for the operating state of the preheating device 3, and The second feeder 4 of the raw material feeder 4 is adjusted so that the temperature of the gas introduced into the heat boiler 27 is optimized.
The quantitative ratio of the powder raw material short-circuited and supplied from b to the lower stage of the preheating device 3 is adjusted.

That is, the greater the amount of short-circuit gas, the less the amount of exhaust gas passing through the upper stage of the preheating device 3. Therefore, the amount of gas passing through the upper stage of the preheating device 3 can be adjusted by opening and closing the damper 34 using the indicated value of the flow meter 35 or the pressure gauge 36 as a guide.

In addition, in the case of a predetermined amount of short-circuit gas, the temperature of the exhaust gas from the uppermost cyclone C1 changes depending on the distribution ratio of the powder raw materials supplied from the first and second feeders 4a and 4b. The exhaust gas temperature decreases, and conversely, if the supply amount ratio to the gas duct 11b is increased, the exhaust gas temperature increases. Therefore, by changing the distribution ratio from the first and second supplies fi4a and 4b using the indicated value of the thermometer 37 as a guideline, the temperature of the exhaust gas introduced into the waste heat boiler 27 can be adjusted.

Exhaust gas duct from the lower stage of the preheating device 3 by the above method) 1
The temperature of the exhaust gas introduced into the waste heat boiler 27 and the amount of hot gas passing through the preheating device 3 can be adjusted by adjusting the short-circuit hot gas amount to the preheating device 5 and the raw material distribution ratio between the uppermost stage and the lower stage of the preheating device 3. Both can be adjusted together, and both the waste heat power generation equipment and the sintering device can be operated in an optimal state.

In the example shown above, the powdered raw material is distributed and supplied to the gas duct lla that constitutes the uppermost heat exchange unit H1 and the gas duct llb of the next stage. It may be distributed and supplied to units H3 and H4, or it may be directly supplied to the lowermost calcination furnace 21 or firing furnace 1.

In addition, the feeding position of the distributed powder raw material is not at each gas duct, but at the raw material chute 17a to 1 of each heat exchange unit.
7c, or directly to the cyclones C2 to C4, or a combination of these may be used.

As mentioned above, there are various possible positions for distributing and supplying the powder raw material to the heat exchange units other than the uppermost heat exchange unit HI, but as shown in the example shown in the figure, the second supply chute 29 from the raw material supply device 4 is When connecting to the second stage heat exchange unit/ ) H2, transfer the entire amount of powder raw material to the second heat exchange unit as necessary.
It may also be supplied to the stage heat exchange unit H2. In this case, the top cyclone C1 is used exclusively for powder collection.

Therefore, the amount of powder raw material flowing into the waste heat boiler 27 can be minimized, which is particularly preferable in such a firing apparatus.

Further, the location of the hot gas from the preheating device 3 is not limited to the example shown in the drawings, and may be extracted from a gas duct) or from multiple locations as necessary. In this case, the hot gas temperature is higher as the hot gas is extracted from the upstream side in the flow direction, so the amount of oil needed to raise the exhaust gas temperature to a constant level can be reduced. Therefore,
It is particularly effective to extract air from the gas outlet side gas duct lie of the lowest stage cyclone C4.

On the other hand, since a dust collector 32 is provided in the middle of the short-circuit gas conduit 31, the fine powder flowing along with the hot scum inside this short-circuit gas conduit 31 is captured by the dust collector 32, and the raw material chute 33 can be returned to the inlet end cover 12 of the firing furnace l through the inlet end cover 12 of the firing furnace l. Therefore, it is possible to prevent the powder raw material from being discharged from the preheating device 3 into the exhaust gas system along with the short-circuiting gas. Note that a plurality of dust collectors 32 may be arranged in series to improve the collection function.

In addition, when using the above-mentioned calcining apparatus, the calcining furnace 21 equipped with the fuel supply device 5b is connected to the gas duct 13 on the gas inlet side of the cyclone C4 at the lowermost stage of the preheating device 3, as in the illustrated example. It is preferable to absorb the temperature change of the entire preheating device 3 by adjusting the operating conditions of the calcination furnace 21 and stabilize the operating conditions of the calcination furnace 1, but it is preferable to stabilize the operating conditions of the calcination furnace 1. It can be easily applied to equipment and existing preheating devices.

Furthermore, we will discuss not only the types and structures of the powder collector and gas tact that make up the heat exchange unit, but also the specific four types of waste heat boilers.
The Ij configuration etc. may be changed as necessary.

(Effects of the Invention) According to the present invention, the raw material supply device is connected to each of the plurality of heat exchange units including at least the uppermost heat exchange unit, and the intermediate part of the waste gas duct of the heat exchange unit located below and the exhaust gas duct are connected to each other. The gas conduit is connected to the gas conduit in the middle by a short-circuit gas conduit, and a dust collector is installed in the middle of this short-circuit gas conduit, so that the raw material supply device supplies the heat exchange unit at the top stage and the heat exchange units at the lower stage. By adjusting the distribution ratio of powdered raw materials to be processed and the amount of short-circuit hot gas flowing from the lower stage heat exchange unit of the preheating device to the exhaust gas duct, the amount of gas passing through the preheating device and the amount of exhaust gas introduced into the waste heat boiler can be adjusted. Both the temperature and temperature can be adjusted over a wide range. Therefore, the amount of hot gas passing through the preheating device can be set to an amount suitable for preheating the powder raw material, and the preheating device can be operated in good condition. By effectively recovering the waste heat in the heat boiler, it is possible to improve the energy economy of the entire firing apparatus including this waste heat power generation equipment.

In this case, the distribution ratio of the powder raw material that is short-circuited and supplied to the lower stage of the preheating device for raising the exhaust gas introduced into the waste heat boiler to a predetermined temperature is based on the raw material short-circuit supply method shown in the second conventional example. will be less than. Moreover, the amount of hot gas short-circuited and induced from the lower stage of the preheating device to the exhaust gas duct is also smaller than in the case of gas short-circuit induction method 1 shown in the third conventional example.

Further, as a result of the above, the firing apparatus according to the present invention also has the following effects.

(1) As the amount of gas passing through the preheating device is reduced, the pressure loss in the preheating device is reduced.

(2) Since the gas temperature in the uppermost heat exchange unit and the exhaust gas duct from this heat exchange unit to the connection with the short-circuit gas pipe is approximately the same level or lower than the first conventional example, these are especially fireproof. Does not require wood lining.

(3) Since the amount of short-circuit gas is smaller than the third conventional example,
The dust collector can be made compact, and the dust collector can be easily arranged.

(4) Because high-temperature gas passes through the short-circuit gas pipe and precipitator, they must be lined with fireproof material, but because they are installed at a low location within the preheating device, the weight of the support structure increases. is small.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a powder raw material firing apparatus showing an embodiment of the present invention, and FIGS. 2 to 4 show first to third conventional examples, each corresponding to FIG. 1. 1. Firing furnace, 4. Raw material supply device, 11a. To 11b, llc...Gas duct, 15.Fist exhaust gas duct, 17a, 17b, 17ca*Raw material chute, 21...
Calcining furnace, 27φ exhaust heat boiler, 31... short circuit gas pipe,
32... Dust collector, CI. C2, c3 +C4...Cyclone (powder collector)
, H+, H2, H3, H4...Heat exchange unit.

Claims (1)

[Scope of Claims] 1. A firing furnace for firing powder raw materials, and four or more stages of heat exchange that are vertically stacked and connected to each other and that introduce exhaust gas from the firing furnace and preheat the powder raw materials with the exhaust gas. unit, and a raw material supply device for supplying powder raw materials to the heat exchange unit, and each of the heat exchange units is provided with a powder collector,
Powder raw material sintering is composed of a gas duct and a raw material chute connected to this powder collector, and a power generation waste heat boiler is connected to the exhaust gas outlet of the heat exchange unit located at the top of the heat exchange units by the exhaust gas duct. In the apparatus, the raw material supply device is connected to each of the plurality of heat exchange units including at least the uppermost heat exchange unit, and a short-circuit gas A powder raw material firing apparatus characterized in that the apparatus is connected by a conduit, and a dust collector is interposed in the middle of the short-circuit gas conduit. 2. The powder raw material firing apparatus according to claim 1, wherein the raw material supply device is connected to the uppermost heat exchange unit and the second heat exchange unit from the top. 3. A calciner equipped with a fuel supply device is installed in the gas duct on the gas inlet side of the powder collector constituting the lowest stage heat exchange unit, and a midway part of the gas duct on the gas outlet side of the powder collector and the exhaust gas 3. The powder raw material firing apparatus according to claim 1 or 2, wherein the duct is connected to a midway portion thereof by a short-circuit gas conduit.