Apparatus for continuously producing a cement clinker

A cement clinker is produced by utilizing a combustible waste material as a fuel for preheating or calcining a cement material, by using an apparatus comprising a cement material feeder, a preheater or calcinator, a rotary kiln, cooler and means for flowing an exhaust gas from the rotary kiln to the preheater or calcinator, which apparatus is characterized by a heat-decomposer which is located between the preheater or calcinator and the rotary kiln and in which a combustible material is heat decomposed with an exhaust gas from the rotary kiln and resultant combustible gas is burnt in the preheater or calcinator.

FIELD OF THE INVENTION 
The present invention relates to an improved method and apparatus for 
continuously producing a cement clinker. More particularly, the present 
invention relates to an improved method and apparatus for continuously 
producing a cement clinker by utilizing combustible waste materials as a 
heat source without causing any environmental pollution. 
BACKGROUND OF THE INVENTION 
It is known that various combustible waste materials, for example, used 
tires, organic material wastes and oil waste, are utilized for generating 
heat by heat-decomposing them and by burning the resultant combustible 
substances. However, this burning of the combustible substances results in 
generation of a combustion gas containing various harmful substances, for 
example, oxides of sulphur, their derivatives, chlorine, chlorine 
compounds and carbon monoxide. Therefore, in order to prevent 
environmental pollution due to the harmful combustion gas, it is necessary 
to treat the combustion gas to eliminate or convert the harmful substances 
to harmless substances. This treatment needs special treating equipment 
and is expensive. Also, the heat-decomposing of the combustible waste 
materials and the burning of the combustible gas produce various 
incombustible residues. Therefore, it is necessary to treat the residues 
in such a manner that no environmental pollution is caused by the 
treatment. 
Under the above-mentioned circumstances, it is strongly desired to provide 
a method and apparatus effective for treating the combustible waste 
materials without environmental pollution. 
It was discovered by the inventors of the present invention that not only 
the combustible waste materials can be utilized as a heat source for 
producing a cement clinker, but also, the incombustible solid residues and 
harmful gases generated from the combustible waste materials have no 
harmful effects on the resultant cement clinker. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a method and apparatus for 
continuously producing cement clinkers while utilizing combustible waste 
materials as a heat source without causing any environmental pollution. 
Another object of the present invention is to provide a method and 
apparatus for continuously producing a cement clinker, in which method, 
both a solid residue and harmful gas are generated from the combustible 
waste materials but which have no harmful effects on the resultant cement 
clinker and are introduced into the cement clinker. 
The above-mentioned objects can be attained by the method of the present 
invention which comprises the steps of: 
feeding a cement material into a preheating or calcining region; 
preheating or calcining said fed cement material in a predetermined 
temperature range; 
forwarding said preheated or calcined cement material into a heating 
region; 
heating said preheated or calcined cement material at a predetermined 
temperature to convert said cement material to a cement clinker; 
moving said cement clinker into a cooling region; 
cooling said cement clinker with cooling air to a decreased temperature, 
and; 
flowing an exhaust gas from said heating region through said preheating or 
calcining region, which method is characterized by the steps of: 
feeding a combustible material into a heat-decomposing region located 
between said heating region and said preheating or calcining region; 
introducing at least a portion of said exhaust gas from said heating region 
into said heat-decomposing region to heat-decompose said combustible 
material and to generate a combustible gas therefrom; 
introducing said combustible gas from said heat-decomposing region into 
said preheating or calcining region, and; 
burning said combustible gas in said preheating or calcining region to 
preheat or calcine said cement material. 
The above-mentioned method of the present invention can be carried out by 
using the apparatus of the present invention which comprises: 
means for feeding a cement material; 
means for preheating or calcining said cement material, which means is 
located downstream from said feeding means and is provided with a 
preheating or calcining chamber therein; 
a rotary kiln for converting said cement material to a cement clinker, 
which kiln is located downstream from said preheating or calcining means, 
and is provided with a heating chamber therein; 
means for cooling said cement clinker with air, which means is located 
downstream from said rotary kiln and is provided with a cooling chamber 
therein and an air-blowing means, and; 
means for flowing an exhaust gas from said heating chamber through said 
preheating or calcining chamber, which apparatus is characterized by means 
for heat-decomposing a combustible material, which means is located 
between said preheating or calcining means and said rotary kiln and is 
provided with a combustion chamber which is connected to means for feeding 
said combustible material thereinto, to said heating chamber in said 
rotary kiln and to said preheating or calcining chamber.

DETAILED DESCRIPTION OF THE INVENTION 
In the method of the present invention, a cement material is fed into a 
preheating or calcining region and preheated, for example, to a 
temperature of from 600.degree. to 1000.degree. C., or calcined, for 
example, at a temperature range of from 800.degree. to 1200.degree. C. The 
preheated or calcined cement material is forwarded to a heating region in 
a rotary kiln and converted therein into a cement clinker at a temperature 
range of, for example, from 1000.degree. to 1500.degree. C. That is, in 
the heating region the cement material is additionally preheated and 
calcined, and, then, the calcined cement material is sintered, to produce 
the cement clinker. Then, the resultant cement clinker is moved to a 
cooling region and cooled to a desired temperature, for example, from 
70.degree. to 150.degree. C. In the above-mentioned process, an exhaust 
gas generated in the heating region exhibits a temperature of from 
800.degree. C. to 1200.degree. C. which is sufficient to heat-decompose 
the combustible materials, such as used tires. This exhaust gas flows into 
the preheating or calcining region to preheat or calcine the cement 
material therein. 
In the method of the present invention, it is essential that a combustible 
material, for example, combustible waste material, such as used tires, 
organic material waste or oil shale, is fed into a heat-decomposing region 
located between the preheating or calcining region and the heating region, 
and at least a portion of the exhaust gas from the heating region is 
introduced into the heat-decomposing region to heat-decompose the 
combustible material at an elevated temperature and to produce a 
combustible gas from the combustible material. The combustible gas is 
introduced from the heat-decomposing region into the preheating or 
calcining region and burnt therein to preheat or calcine the cement 
material. 
In the above-mentioned method, a solid residue produced from the 
combustible material in the heat-decomposing region is mixed with the 
preheated or calcined cement material, and the resultant mixture is moved 
into the heating region. The solid residue contains, for example, metals 
such as iron, carbon, SiO.sub.2, CaO, Al.sub.2 O.sub.3, and Fe.sub.2 
O.sub.3. These substances are heated together with the cement material at 
an elevated temperature in the heating region, and the resultant products, 
which are harmless to the cement clinker, are uniformly contained in the 
resultant cement clinker. 
Also, a portion of the combustion gas generated from the combustible gas in 
the preheating or calcining region, such as oxides of sulphur, their 
derivatives, chlorine, chlorine compounds (HCl) and carbon monoxide, which 
are harmful to humans, reacts with a portion (CaO) of the cement material 
in the preheating or calcining region and the resultant reaction product 
is introduced into the cement material. 
The combustible material usable for the present invention can be selected 
from various combustible waste materials, for example, used tire wastes, 
rubber wastes, oil wastes, oil-containing sludges, asphalt wastes, pitch 
wastes, debris and organic compound wastes. The combustible material may 
be selected from oil shale, oil sand, coal, lignite and peat. 
When the cement clinker is moved from the heating region in the rotary kiln 
to the cooling region, a cooling air is introduced into the cooling region 
to cool the cement clinker. The exhaust air from the cooling region 
exhibits a temperature of from 100.degree. to 800.degree. C., which 
temperature is sufficient to thermally decompose the combustible 
materials, such as oil wastes, oil-containing sludges, polyethylene or 
polyvinyl chloride. Also, the exhaust air contains 15% by volume of 
molecular oxygen, while the exhaust gas from the heating region contains 
only 0.5 to 3.5% by volume of molecular oxygen. Accordingly, the exhaust 
air from the cooling region can be utilized not only to heat decompose the 
combustible material, but also, to burn a portion of the combustible 
material so as to accelerate the heat decomposition thereof. That is, a 
portion of the exhaust air may be introduced into the preheating or 
calcining region, to promote the combustion of the combustible gas 
therein. Also, another portion of the exhaust air from the cooling region 
may be introduced into the heat-decomposing region to promote the 
heat-decomposition of the combustible material. In this case, since the 
exhaust air contains molecular oxygen, a portion of the combustible 
material can be burnt in the heat-decomposing region, so as to accelerate 
the heat-decomposition of the combustible material. 
An exhaust gas from the calcining region may be utilized to preheat the 
cement material. The cement material may be in the form of grains or fine 
particles. 
The combustible material may be continuously or intermittently fed into the 
heat-decomposing region. However, it is preferable that the combustible 
material be intermittently fed into the heat-decomposing region, so as to 
control the preheating or calcining temperature. That is, it is preferable 
that the feeding stage and the feeding amount of the combustible material 
be controlled in response to the temperature of a portion of the 
preheating or calcining region in which portion the combustible gas is 
burnt. When the temperature becomes lower than a predetermined value, the 
feeding of the combustible material is effected and/or the feeding amount 
thereof is increased. 
The above-mentioned control is effective for maintaining the temperature of 
the preheating or calcining region substantially constant over the entire 
period of a cement clinker producing operation. 
In order to flow the exhaust gas from the heating region through the 
preheating or calcining region, a reduced pressure may be generated in or 
upstream from the preheating or calcining region. 
The apparatus of the present invention is provided with a feeding means for 
a cement material; a preheating or calcining means having a preheating or 
calcining chamber in which the fed cement material is preheated or 
calcined; a rotary kiln having a heating chamber for converting therein 
the preheated or calcined cement material to a cement clinker, a cooling 
means having a cooling chamber for the cement clinker and air-blowing 
means for feeding therethrough a cooling air into the cooling chamber, and 
flowing means for flowing an exhaust gas from the heating chamber through 
the preheating or calcining chamber. 
In the apparatus of the present invention, it is essential that 
heat-decomposing means, having a heat-decomposing chamber, is arranged 
between the preheating or calcining means and the rotary kiln. The 
heat-decomposing means is provided with feeding means for a combustible 
material and is connected to the heating chamber and the preheating or 
calcining chamber. 
The heat-decomposing chamber may be connected to the combustible 
material-feeding means through a conduit. That is, in this case, the 
combustible material is fed into the heat-decomposing chamber through the 
conduit. 
Also, the heat-decomposing means may be provided with an exhaust gas 
conduit extending from a bottom portion of the heat-decomposing chamber 
toward the heating chamber of the rotary kiln. This conduit is effective 
for introducing a portion of an exhaust gas from the heating chamber into 
the heat-decomposing chamber. 
Furthermore, the heat-decomposing means may be provided with a combustible 
gas conduit extending from an upper portion of the heat-decomposing 
chamber into the preheating or calcining chamber. This conduit is 
effective for introducing the combustible gas generated by the 
heat-decomposition of the combustible material, into the preheating or 
calcining chamber in which the combustible gas is burnt. 
When the combustible material is in the form of lumps or in a shaped form, 
for example, used tire waste, it is preferable that a grid is placed in 
the heat-decomposing chamber so as to place the combustible material on 
the grid. When the combustible material is heat-decomposed, the resultant 
combustible gas is separated from a solid residue remaining on the grid, 
and the solid residue is moved from the grid toward the heating chamber in 
the rotary kiln through the exhaust gas conduit. 
The cooling chamber may be connected to the preheating or calcining chamber 
through an exhaust air conduit. This conduit is effective for supplying a 
portion of an exhaust air from the cooling chamber to the preheating or 
calcining chamber. The exhaust air can promote the combustion of the 
combustible gas in the preheating or calcining chamber. 
The exhaust air conduit may be additionally connected to a bottom portion 
of the heat-decomposing chamber through a conduit branched from the 
exhaust air conduit. 
The means for flowing the exhaust gas from the heating chamber of the 
rotary kiln through the preheating or calcining chamber may be a fan 
located in or upstream from the preheating or calcining chamber. 
The features and advantages will be further illustrated by the following 
description with reference to the accompanying drawings. 
Referring to FIG. 1, a cement clinker-producing apparatus 1 is provided 
with a cement material feeder 2, a preheater 3, a rotary kiln 4 and a 
cooler 5. A cement material 6 is granulated by a granulator 7. The 
granulated cement material is fed into the preheater 3 through an endless 
conveyer 8. The preheater 3 has a first preheating chamber 9, a second 
preheating chamber 10 and a third preheating chamber 10a separated from 
each other by partitions 11a and 11b. The cement material 6 fed in the 
preheater 3 travels through the first, second and third preheating 
chambers 9, 10 and 10a by means of an endless conveyor 12. In the third 
preheating chamber 10a, a partition 11c projects downward from the ceiling 
of the third chamber 10a so as to divide the third chamber 10a into two 
sections, that is first and second sections 10b and 10c. Then, the 
preheated (calcined) cement material 6 is moved to a heating chamber 13 in 
the rotary kiln 4 through an inclined guide plate 14. In the heating 
chamber 13, the cement material 6 is converted to a cement clinker 15. The 
resultant cement clinker 15 is discharged from the heating chamber 13 into 
a cooling chamber 16 of the cooler 5, and cooled therein with a cooling 
air supplied from the atmosphere through air-blowing means which is 
provided with an inclined plate 35 having a number of perforations, at 
least one air chambers 36 and at least fan one 37 connected to each air 
chamber 36 through a conduit 38. 
The cement material fed into the heating chamber 13 is heated by a 
combustion gas generated by a burner 17 in which a mixture of a fuel and 
air is burnt. The cooling air supplied into the cooling chamber is also 
effective as secondary air to promote the combustion of the air-fuel 
mixture. 
The apparatus 1 of FIG. 1 is provided with a heat-decomposer 18 for a 
combustible material 19. The heat-decomposer 18 is provided with a 
heat-decomposing chamber 20, and a feeder 21 for the combustible material 
19. The feeder 21 is connected to the heat-decomposing chamber through a 
conduit 22 which is provided with one or more air seal gates 23. A grid 24 
is located in the heat-decomposing chamber 20. A bottom portion of the 
heat-decomposing chamber 20 is connected to an exhaust gas conduit 25 
extending into the second section 10c of the third preheating chamber 10a, 
and toward the heating chamber 13. Also, an upper portion of the 
heat-decomposing chamber 20 is connected to a combustible gas conduit 26 
extending into the first section 10b of the third preheating chamber 10a 
of the preheater 3. 
The combustible material 19 can be intermittently fed into the 
heat-decomposing chamber 20 from the feeder 21 through the conduit 22 by 
opening the air seal gate 23. The combustible material 19 placed on the 
grid 24 in the heat-decomposing chamber 20 is heat-decomposed by the 
exhaust gas introduced from the heating chamber 13 into the 
heat-decomposing chamber 20 through the exhaust gas conduit 25. The 
resultant combustible gas is introduced into the first section 10b of the 
third preheating chamber 10a through the conduit 26 and is burnt in the 
first section 10b, so as to preheat the cement material 6. A portion of 
the preheating gas in the third chamber 10a is sucked by producing a 
reduced pressure by means of a fan 27 through a collecting conduit 28 and 
a suction conduit 29, and, then, blown into the second preheating chamber 
10 through a conduit 30. A portion of the exhaust gas from the first and 
second chambers 9 and 10 is sucked by producing a reduced pressure by 
means of a fan 31 through a collecting conduit 32 and a conduit 33, and, 
then, discharged to the outside of the apparatus 1 through a conduit 34. 
The partition 11c in the third preheating chamber 10a is effective as a 
guide plate for smoothly introducing the exhaust gas from the heating 
chamber 13 of the rotary kiln 4 into the exhaust gas conduit 25 and the 
collecting conduit 28 and for preventing the direct introduction of the 
combustible gas in the first section 10b into the collecting conduit 28. A 
portion of the combustible gas introduced into the first section 10b and a 
portion of the resultant combustion gas generated in the section 10b are 
introduced into the second preheating chamber 10 through conduits 39 and 
39a, to preheat the cement material in the second chamber 10. 
Referring to FIG. 2, the apparatus 41 is provided with a suspension 
preheater 42, a calcinator 43 having a calcining chamber 58, a rotary kiln 
4, a cooler 5 and a heat-decomposer 18. In this apparatus 41, a portion of 
the exhaust gas from the heating chamber 13 of the rotary kiln 4 is 
introduced into the heat-decomposer 18 and another portion of the exhaust 
gas is introduced into a calcining chamber 58 through a conduit 44 and a 
mixing chamber 60. An exhaust gas from the calcining chamber 58 is 
discharged to the outside of the apparatus 41 through a cyclone 45, 
conduit 46, cyclone 47, conduit 48, cyclone 49, conduit 50, cyclone 51 and 
conduits 52 and 53 by means of a fan 54. 
A cement material is fed through an inlet 55 and travels toward the 
calcining chamber 58 in such a manner that the cement material fed through 
the inlet 55 is moved together with a flow of the exhaust gas through the 
conduit 50 to the cyclone 51, and separated from the flow of the exhaust 
gas in the cyclone 51, the separated cement material is fed through a 
conduit 56 into the conduit 48, moved together with a flow of the exhaust 
gas through the conduit 48 to the cyclone 49, and separated from the 
exhaust gas stream in the cyclone 49, the separated cement material is fed 
through a conduit 57 into the conduit 46, moved together with a flow of 
the exhaust gas through the conduit 46 into the cyclone 47 and separated 
from the exhaust gas flow in the cyclone 47 and, then, the separated 
cement material is fed into the calcining chamber 58. During traveling 
from the inlet 55 to the calcining chamber 58, the cement material is 
preheated by the flows of the exhaust gas flowing through the conduits 50, 
48 and 46. 
The combustible material 19 placed in the heat decomposing chamber 20 is 
heat-decomposed by the exhaust gas introduced thereinto through the 
conduit 25, and the resultant combustible gas is introduced into the 
calcining chamber 58 through the conduit 26. The combustible gas is burnt 
in the calcining chamber 58 to calcine the cement material. The calcined 
cement material is moved into the cyclone 45 and separated therein from 
the flow of the exhaust gas, and the separated cement material is 
introduced into the rotary kiln 4 through a conduit 59. 
In the apparatus 41 of FIG. 2, the cooling chamber 16 is connected to a 
mixing chamber 60, which is formed in the conduit 44 between the calcining 
chamber 58 and the heating chamber 16, through a conduit 61. A portion of 
the exhaust air from the cooling chamber 16 is introduced into the mixing 
chamber 60 and mixed with the exhaust gas from the heating chamber 13. The 
mixed gas is introduced into the calcining chamber 58. A cyclone 62 is 
used to separate the exhaust air from dust. The separated dust is returned 
into the cooling chamber and mixed with the cement clinker. 
Referring to FIG. 3, an apparatus 71 is provided with a heat-decomposer 72 
arranged between the heating chamber 13 and the calcining chamber 58, and 
having a heat-decomposing chamber 73 located just upstream from the 
heating chamber 13. The heat-decomposing chamber 73 is connected to the 
combustible material feeder 21 through a conduit 74. Accordingly, a 
combustible material 19, which is preferably in the form of lumps or 
shaped articles, for example, used tire wastes, is fed into the 
heat-decomposing chamber 73 from the feeder 21 through the conduit 74. In 
this case, the entire amount of the exhaust gas from the heating chamber 
13 is introduced into the heat-decomposing chamber 73 to heat-decompose 
the combustible material 19, and the resultant combustible gas is 
introduced together with the exhaust gas into the calcining chamber 58. 
The combustible gas and the exhaust gas may be mixed with the exhaust air 
which has been introduced from the cooling chamber 16 into the mixing 
chamber 60 through the conduit 61. 
It is preferable that the amount of the combustible material to be fed into 
the heat-decomposing chamber 73 be regulated to an extent that the heat 
energy generated from the combustible gas is in an amount corresponding to 
10% or less of the entire heat energy necessary for converting the 
calcined cement material to the desired cement clinker. Also, it is 
preferable that the intermittent feeding stage and feeding amount of the 
combustible material are controlled in response to both the temperatures 
of the heating chamber 13 and the calcining chamber 58. 
Referring to FIG. 4, an apparatus 81 is provided with a heat-decomposer 18 
in which a bottom portion of the heat-decomposing chamber 20 is connected 
to the mixing chamber 60 through a conduit 82. 
In the apparatus 81 of FIG. 4, a major portion of the exhaust gas is 
introduced into the mixing chamber 60 and mixed therein with the exhaust 
air introduced from the cooling chamber 16 through the conduit 61. 
A portion of the mixed gas is introduced into the heat-decomposing chamber 
20 and the remaining portion thereof is introduced into the calcining 
chamber 58. The portion of the mixed gas in the heat-decomposing chamber 
20 cannot only heat-decompose the combustible material 19, but also, burn 
a portion of the combustible material so as to promote the 
heat-decomposition. The resultant mixture of a combustible gas and a 
combustion gas is introduced into the calcining chamber 58 through the 
conduit 83, and burnt therein to calcine the cement material. 
Referring to FIG. 5, an apparatus 91 is provided with a heat-decomposer 92 
connected to a supply source 93 of a combustible material through a 
conduit 94. In this case, it is preferable that the combustible material 
is in the form of a liquid or slurry, for example, oil waste, 
oil-containing sludge or other liquid organic compounds. 
The exhaust gas from the heating chamber 13 of the rotary kiln 4 is 
introduced into the heat-decomposing chamber 92. Also, the exhaust air 
from the cooling chamber 16 is introduced into the heat-decomposing 
chamber 92 through the conduit 61. The combustible material fed into the 
heat-decomposing chamber 92 is heat-decomposed with the mixture of the 
exhaust gas from the heating chamber 13 and the exhaust air from the 
cooling chamber 16, and the resultant heat-decomposing mixture is 
introduced into the calcining chamber 58, and burnt therein to calcine the 
cement material. 
Referring to FIG. 6, an apparatus 101 is provided with a heat-decomposer 
102 having a heat-decomposing chamber 103, and a conduit 104 through which 
the calcining chamber 105 is directly connected to the cooling chamber 16. 
The heat-decomposing chamber 103 is provided with a combustible gas 
conduit 106 through which an upper portion of the heat-decomposing chamber 
103 is connected to the calcining chamber 105, and an exhaust gas conduit 
107 extending from a bottom portion of the heat-decomposing chamber 103 
toward the heating chamber 13 of the rotary kiln 4. Also, a bottom portion 
of the decomposing chamber 103 is connected to the exhaust air conduit 104 
through a conduit 108. 
The apparatus 101 is also provided with a first preheater 109 and a second 
preheater 110 arranged in parallel to each other. In the first preheater 
109, the exhaust gas from the heating chamber 13 flows upward through a 
conduit 111, a cyclone 112, a conduit 113, a cyclone 114, a conduit 115, a 
cyclone 116, a conduit 117, a cyclone 118 and a conduit 119 and, then, is 
discharged outside of the apparatus 101 by means of a fan 120. Also, in 
the first preheater 109, the cement material is fed through a first inlet 
121, travels together with a flow of the exhaust gas into the cyclone 118 
through the conduit 117 and is separated from the exhaust gas flow in the 
cyclone 118; the separated cement material is moved into the conduit 115 
through a conduit 122, travels together with a flow of the exhaust gas 
through the conduit 115 into the cyclone 116, and is separated from the 
flow of the exhaust gas in the cyclone 116; the separated cement material 
is introduced into the conduit 113 through a conduit 123, travels together 
with a flow of the exhaust gas through the conduit 113 to the cyclone 114, 
and is separated from the flow of the exhaust gas in the cyclone 114; the 
separated cement material is introduced into the conduit 111 through a 
conduit 124, travels together with a flow of the exhaust gas through the 
conduit 111 to the cyclone 112, and is separated from the flow of the 
exhaust gas in the cyclone 112, and; the separated cement material is fed 
into the calcining chamber 105 through a conduit 125. While the cement 
material travels from the inlet 121 to the calcining chamber 105, the 
cement material is preheated by the exhaust gas from the heating chamber 
13. 
In the second preheater 110, an exhaust gas from the calcining chamber 105 
flows upward through a conduit 126, a cyclone 127, a conduit 128, a 
cyclone 129, a conduit 130, a cyclone 131, a conduit 132, a cyclone 133 
and a conduit 134 and discharged to the outside of the apparatus 101 by 
means of a fan 135. The flow of the exhaust gas from the calcining chamber 
105 is utilized to preheat the cement material. 
The cement material is fed through a second inlet 136 into the conduit 132, 
travels together with a flow of the exhaust gas through the conduit 132 to 
the cyclone 133, and is separated from the flow of the exhaust gas in the 
cyclone 133; the separated cement material is fed into the conduit 130 
through a conduit 137, travels together with a flow of the exhaust gas 
through the conduit 130 to the cyclone 131 and is separated from the flow 
of the exhaust gas in the cyclone 131; the separated cement material is 
fed into the conduit 128 through a conduit 138, travels together with a 
flow of the exhaust gas through the conduit 128 to the cyclone 129 and is 
separated from the flow of the exhaust gas in the cyclone 129, and, 
finally; the separated cement material is fed into the calcining chamber 
105 through a conduit 139. 
When the cement material is calcined in the calcining chamber 105 by 
burning the combustible gas coming from the heat-decomposing chamber 103, 
the resultant calcined material is moved together with a flow of the 
exhaust gas from the calcining chamber 105 to the cyclone 127 and 
separated therein from the flow of the exhaust gas. The separated cement 
material is introduced into the heating chamber 13 through a conduit 140. 
The calcining chamber 15 may be provided with a supplementary burner (not 
shown in FIG. 6) for burning a fuel in the calcining chamber. This 
supplementary burner is effective to promote the calcination of the cement 
material.