Cement baking equipment

Abstract

[Problem] To more effectively denitrify a cement-kiln discharge gas in an RSP-type burning device for cement. [Solution] A burning device 1 for cement comprises: a rotary kiln 2; a mixing chamber 4 disposed between the rotary kiln and a lowermost cyclone; a flash- and swirl-type calciner 3 disposed between the mixing chamber and a second-lowest preheater cyclone; a clinker cooler 6 for cooling a cement clinker discharged from the rotary kiln; and a gas duct 7a for introducing a discharge gas G2 from the clinker cooler into a region located after the outlet of the mixing chamber, instead of a gas duct for directly introducing the discharge gas G2 into the calciner. A gas duct 7b which branches off from the gas duct 7 and introduces the discharge gas from the clinker cooler into a burner 3a disposed in the calciner may be disposed, and burners 8 (8A, 8B) for denitration may be disposed between the end 2b of the rotary kiln and the inlet 4a of the mixing chamber.

Description

[Technical Field]

[0001] The present invention relates to a technology for reducing the concentration of nitrogen oxides (hereinafter referred to as "NOx") in combustion gas emitted from a cement calciner having an RSP calciner (hereinafter referred to as "RSP cement calciner"). [Background technology]

[0002] There are various types of NSP cement kiln-equipped calciners, but in all of them, the exhaust gas from the cement kiln contains NOx resulting from the high temperature range of the calcination zone. When the NOx concentration is high, denitrification agents such as urea or ammonia are added, or the NOx concentration is reduced by the reduction effect of combustion in the calciner.

[0003] Various measures have been adopted to reduce NOx in the exhaust gas from the RSP (product name, manufactured by Kawasaki Heavy Industries, Ltd. and Taiheiyo Cement Corporation) cement calciner, which is a type of NSP cement calciner.

[0004] As shown in Figure 2, a typical RSP cement firing apparatus 21 includes a rotary kiln 22, an airflow and vortex-type calciner 23, a mixing chamber 24, a loop duct 25, a clinker cooler 26, etc. Primary air A1 is blown into the rotary kiln 22 from a kiln burner 22a of the rotary kiln 22, secondary air A2a from the clinker cooler 26 is blown into the rotary kiln 22 via the kiln burner 22a, secondary air A2b from the clinker cooler 26 is blown into the calciner 23 from a calciner burner 23a via gas ducts 27 and 27b, and tertiary air A3 from the clinker cooler 26 is introduced into the calciner 23 via the gas ducts 27 and 27a.

[0005] In a cement burning apparatus 21 having the above configuration, in order to reduce NO in the exhaust gas G1 of the cement burning apparatus 21, for example, as shown in Figure 3, a portion A3b (approximately 80% of the tertiary air A3) of the tertiary air A3 (see Figure 2) is supplied to the outlet 24b of the mixing chamber 24 and beyond without being introduced into the calciner 23, or denitration burners 28 (28A, 28B) are installed between the kiln end 22b of the rotary kiln 22 and the inlet 24a of the mixing chamber 24 to denitrify the cement kiln exhaust gas. Summary of the Invention [Problem to be solved by the invention]

[0006] However, the method of bypassing a portion A3b of the tertiary air A3 beyond the outlet 24b of the mixing chamber 24 has little effect on reducing NOx in the cement kiln exhaust gas, and even when a denitrification burner is installed, the reduction remains at around 70 ppm.

[0007] The present invention has been made in view of the above points, and has as its object to more effectively denitrify cement kiln exhaust gas in an RSP-type cement firing apparatus. [Means for solving the problem]

[0008] In order to achieve the above object, the present invention provides a cement firing apparatus comprising: a rotary kiln; a mixing chamber disposed between the rotary kiln and a lowest-stage cyclone; an airflow type and a vortex type calciner disposed between the mixing chamber and a preheater cyclone second from the bottom; a clinker cooler that cools the cement clinker discharged from the rotary kiln; and a gas duct that does not directly introduce exhaust gas from the clinker cooler into the calciner furnace, but introduces the exhaust gas into a region subsequent to the outlet of the mixing chamber.

[0009] According to the present invention, exhaust gas from the clinker cooler is introduced into the region after the outlet of the mixing chamber rather than directly into the calciner furnace, thereby forming a wide denitrification region that extends from the end of the rotary kiln to the outlet of the mixing chamber, and reducing NOx by approximately 100 ppm compared to conventional cement firing equipment.

[0010] The cement burning apparatus may further include a gas duct branching from the gas duct and directing exhaust gas from the clinker cooler to a burner installed in the calciner.

[0011] Furthermore, by providing a denitration burner between the bottom of the rotary kiln and the inlet of the mixing chamber, the denitration effect can be further enhanced.

[0012] Furthermore, the present invention provides a method for operating a cement calcination apparatus including a rotary kiln, a mixing chamber disposed between the rotary kiln and a lowest-stage cyclone, an airflow type and a vortex type calciner disposed between the mixing chamber and the second-lowest preheater cyclone, and a clinker cooler for cooling cement clinker discharged from the rotary kiln, characterized in that exhaust gas from the clinker cooler is introduced into a region subsequent to the outlet of the mixing chamber rather than being introduced directly into the calciner.

[0013] According to the present invention, a wide denitrification region is formed that extends from the bottom of the rotary kiln to the outlet of the mixing chamber, making it possible to reduce NOx by approximately 100 ppm compared to conventional methods.

[0014] In the method for operating the cement burning apparatus, 90% or more of the exhaust gas from the clinker cooler can be introduced into the region after the outlet of the mixing chamber.

[0015] In addition, 10% or less of the exhaust gas from the clinker cooler can be introduced into a burner installed in the calciner.

[0016] Furthermore, by injecting fuel between the end of the rotary kiln and the inlet of the mixing chamber and gasifying the fuel in an area with a low oxygen concentration, the denitrification effect can be enhanced and the decarbonation efficiency of the cement raw materials can also be improved. [Effects of the Invention]

[0017] As described above, according to the present invention, denitration of cement kiln exhaust gas can be carried out more effectively in an RSP cement firing apparatus. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is an overall configuration diagram showing one embodiment of a cement burning apparatus according to the present invention. [Figure 2] 1 is a schematic diagram showing the main parts of a conventional RSP-type cement burning apparatus. [Figure 3] FIG. 1 is an explanatory diagram of a conventional method for reducing NOx in an RSP-type cement calciner. DETAILED DESCRIPTION OF THE INVENTION

[0019] Next, embodiments of the present invention will be described in detail with reference to the drawings.

[0020] 1 shows one embodiment of a cement firing apparatus according to the present invention, and is equipped with a rotary kiln 2, a mixing chamber 4 connected to the end 2b of the rotary kiln 2, a loop duct 5 located above the mixing chamber 4 and leading to a lowest-stage cyclone (not shown), an airflow-type and vortex-type calciner 3 located between the second-lowest preheater cyclone (not shown, hereinafter referred to as the "two-stage cyclone") and the mixing chamber 4, and a clinker cooler 6 for cooling the cement clinker discharged from the rotary kiln 2. The RSP cement firing apparatus 1 is characterized by the addition of a gas duct 7 that guides exhaust gas G2 from the clinker cooler 6 to a kiln burner 2a, a region after the outlet 4b of the mixing chamber 4, and a calciner burner 3a. The gas duct 7 branches into a gas duct 7a leading to the region after the outlet 4b of the mixing chamber 4 and a gas duct 7b leading to the calciner burner 3a installed in the calciner 3. Furthermore, denitration burners 8 (8A, 8B) may be provided between the kiln end 2b of the rotary kiln 2 and the inlet 4a of the mixing chamber 4. The cement firing apparatus 1 according to the present invention does not have the gas duct 27a that is provided in the conventional cement firing apparatus 21 shown in FIG.

[0021] Next, the operation of the cement burning apparatus 1 having the above configuration will be described.

[0022] Fuel such as pulverized coal, primary air A1, and secondary air A2a from the clinker cooler 6 are blown into the kiln burner 2a of the rotary kiln 2, and a preheater located after the loop duct 5 preheats the cement raw materials using combustion gas G1 from the rotary kiln 2. Meanwhile, exhaust gas G2 from the clinker cooler 6 is introduced via gas duct 7 to the burner 3a installed in the calciner 3 and to the area after the outlet 4b of the mixing chamber 4 (in this embodiment, the inlet of the loop duct 5). In other words, exhaust gas G2 from the clinker cooler 6 is not introduced directly into the calciner 3 as in the conventional system, but is used as secondary air A2b for the burner 3a and tertiary air A3 for the area after the outlet 4b of the mixing chamber 4. In addition, all preheated raw materials R from the two-stage cyclone are introduced into the calciner 3.

[0023] In the calciner 3, fuel such as pulverized coal supplied from the burner 3a is partially burned using a portion (A2b) of the exhaust gas G2 and is gasified using the high-temperature preheated raw material R supplied to the calciner 3. The preheated raw material R prevents tar and other contaminants from adhering to the walls of the calciner 3, and the fuel is introduced into the mixing chamber 4. This reduces NOx in the exhaust gas G1 from the rotary kiln 2 inside the mixing chamber 4. After the NOx has been reduced, the exhaust gas is completely combusted in the loop duct 5 using tertiary air A3, and is then introduced as exhaust gas G3 into the subsequent preheater.

[0024] Furthermore, fuel is injected from denitration burners 8 (8A, 8B) between the end 2b of the rotary kiln 2 and the inlet 4a of the mixing chamber 4 to promote gas mixing and reduce NOx in the exhaust gas G1 from the rotary kiln 2 in the low-oxygen region of the mixing chamber 4. Furthermore, by burning a portion of the fuel in the calciner 3, the decarbonation efficiency of the cement raw materials can also be improved.

[0025] According to the cement burning apparatus 1 having the above configuration, as shown in FIG. 1, a wide denitrification zone DZ can be formed that includes the end 2b of the rotary kiln 2 and the outlet 4b of the mixing chamber 4, and NOx can be reduced by approximately 100 ppm compared to the conventional cement burning apparatus 21 shown in FIG. 2.

[0026] In the above embodiment, the exhaust gas G2 from the clinker cooler 6 is used as the partial combustion air A2b in the calciner burners 3a and as the tertiary air A3 to the outlet 4b and beyond of the mixing chamber 4, but the exhaust gas G2 may not be used for the partial combustion air A2b in the calciner burners 3a, and may be used only for the tertiary air A3. Regardless of whether the exhaust gas G2 is used for the secondary air A2a and the calciner burners 3a, the present invention introduces all of the exhaust gas G2 from the clinker cooler 6, which was conventionally introduced directly into the calciner 3, into the region of the mixing chamber 4 to the outlet 4b and beyond. [Explanation of symbols]

[0027] 1 (RSP type) cement baking equipment 2. Rotary kiln 3. Calciner 4 Mixing chamber 5 Loop Duct 6 Clinker Cooler 7 Gas Duct 8 (8A, 8B) Denitrification burner

Claims

1. Rotary kiln and a mixing chamber disposed between the rotary kiln and the lowest cyclone; an airflow type and vortex type calciner disposed between the mixing chamber and the second-lowest preheater cyclone; a clinker cooler that cools the cement clinker discharged from the rotary kiln; A cement burning apparatus characterized in that it does not have a gas duct that directly introduces exhaust gas from the clinker cooler into the calciner furnace, but has a gas duct that introduces it into a region subsequent to the outlet of the mixing chamber.

2. 2. The cement burning apparatus according to claim 1, further comprising a gas duct branching from the gas duct and directing exhaust gas from the clinker cooler to a burner installed in the calciner.

3. 3. The cement burning apparatus according to claim 1, further comprising a denitration burner provided between the bottom of the rotary kiln and the inlet of the mixing chamber.

4. A cement burning apparatus comprising: a rotary kiln; a mixing chamber disposed between the rotary kiln and a lowest-stage cyclone; an airflow type and vortex type calciner disposed between the mixing chamber and a preheater cyclone second from the bottom; and a clinker cooler for cooling cement clinker discharged from the rotary kiln, A method for operating a cement burning apparatus, characterized in that exhaust gas from the clinker cooler is introduced into a region subsequent to the outlet of the mixing chamber rather than being introduced directly into the calciner.

5. 5. The method for operating a cement burning apparatus according to claim 4, wherein 90% or more of the exhaust gas from the clinker cooler is introduced into the region downstream of the outlet of the mixing chamber.

6. 6. The method for operating a cement burning apparatus according to claim 4, wherein 10% or less of the exhaust gas from the clinker cooler is introduced into a burner installed in the calciner.

7. 7. A method for operating a cement burning apparatus according to claim 4, 5 or 6, characterized in that fuel is injected between the end of the rotary kiln and the inlet of the mixing chamber, the fuel is gasified in an area with a low oxygen concentration, and NOx in the exhaust gas from the rotary kiln is reduced.

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