JPS58110904A - Exhaust gas circulating combustion of rotary kiln - Google Patents

Abstract

PURPOSE:To prevent an oversupply of combustible substance to the rear stage of the kiln and to decrease combustion volume by a method wherein a part of the exhaust gas in the rotary kiln which contains unburnt substance is extracted so as to be utilized as a fuel for a burner and also as a heat source for preheating combustion air. CONSTITUTION:A part of the exhaust gas G in the rotary kiln 1 which contains unburnt substance is extracted by an exhaust gs duct 4, and thus extracted gas G1 is led to an air preheater 6 through a lagging pipe 5 for use in preheating the combustion air for the burner 3. Further the gas G1 is sent via a circulation fan 7 to the burner 3 as fuel for it. In the burner 3, the gas G1 having a low heating value is added with fuel F to increase the heat value and burning characteristics, and thus obtained mixture is burnt with the combustion air A which is preheated by the preheater 6.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rotary kiln exhaust gas circulation combustion method.

As shown in FIG. 1, in the rotary kiln 1, a carbonaceous material C having volatile components (hereinafter referred to as V and M) such as coal or petroleum coke is preheated in a preheater or an incinerator 2. It is charged into the kiln 1 from the bottom of the furnace. The supplied carbon material C is V, M in section IA.
, a reduction reaction of the pellets (Pe) is performed in section IB (large amount of CO gas) and section IC (small amount of CO gas) to generate CO gas, and the remaining gas is discharged from the front of the furnace. The generated V, M and combustible gas (e.g. C
Most of the O gas) is combusted by the combustion air A injected into the kiln 1, but a portion is not combusted and is discharged from the kiln 1 as unburned gas contained in the exhaust gas G. This is because the generation of V and M occurs in a narrow section, so it is very difficult to achieve complete combustion within this section, and when complete combustion occurs, there is a drawback that the temperature is too high.

Therefore, in the past, exhaust gas containing unburned matter was
The afterburner completely burns it and uses it as a heat source for the preheater 2, but it is VoM.

When a large amount of combustible materials such as combustible materials are generated, excessive heat generation may occur. On the other hand, since there are few combustible gases such as V, M, and CO gases generated in front of the furnace, heating by the burner 3 is required as a heating source.

This invention was proposed in view of the above circumstances, and its purpose is to provide a rotary kiln that can prevent excessive supply of combustible materials to the rear stage of the kiln and improve the effective frequency rate of energy. The object of the present invention is to provide an exhaust gas circulation combustion method.

The exhaust gas circulation combustion method according to the present invention extracts a part of the rotary kiln exhaust gas containing unburned matter, uses this extracted gas as fuel for a burner in front of the furnace, and uses the heat of the extracted gas to fuel the burner. This preheats the combustion air, prevents excessive supply of combustibles to the latter stage of the kiln, and reduces the amount of pre-furnace burner O fuel, thereby improving the effective utilization rate of energy in the kiln.

The present invention will be described below based on an illustrated embodiment.

Incidentally, parts that are the same as or modified from the conventional ones are given the same reference numerals and explanations are omitted. As shown in FIG. 2, a part of the exhaust gas GO containing unburned gas is extracted in the exhaust gas duct 4, and the extraction gas G is heated at a temperature of 800 to 1000°C.
The combustion air A of the burner 3 is guided to the air preheater 6 through the heat insulation pipe 5 and preheated to 400 to 500°C.

The bleed gas G1, now at a temperature of 400 to 500°C, is sent to the burner 3 as fuel for the burner 3 via the circulation fan 7. In burner 3, the calorific value Q) is small, the bleed gas G
, is added with fuel F to increase its calorific value and combustibility, and is combusted using combustion air A preheated to 200 to 300° C. in a preheater 6.

By bleeding and circulating the exhaust gas and combusting it in this manner, it is possible to reduce the amount of fuel added to the burner 3 and to recover heat from the exhaust gas.

Note that the operating temperature of the circulation fan 7 is 400 to 500°C, so if the preheater 6 lowers the bleed gas at 800 to 1000°C to 400 to 500°C and keeps the fan 7 at a low temperature, the heat will be preheated to 4. It will be recovered as preheated air heat by the vessel 6.

As described above, according to the present invention, excessive supply of combustible material to the latter stage of the kiln is prevented, and the amount of fuel in the front burner is reduced by circulating combustible gas, thereby greatly improving the effective utilization rate of energy in the rotary kiln. .

[Brief explanation of the drawing]

1 is a schematic diagram showing a conventional exhaust gas utilization method, and FIG. 2 is a schematic diagram showing an exhaust gas circulation combustion method according to the present invention. 1. Rotary kiln, 2. Preheater or incinerator, 3. Burner, 4. Exhaust gas duct, 5. Heat insulation piping, 6. Air preheater, 7. Circulation fan. , C...charcoal material, P@...pellet, G...exhaust gas,
G...Bleed gas, A...Combustion air, F...Fuel.

Claims (1)

[Claims] (1) A part of the exhaust gas of the rotary kiln containing unburned matter is extracted, and this extracted gas is used as fuel for the exhaust gas in front of the furnace, and the combustion air of the burner is generated by the heat of the extracted gas. A rotary kiln exhaust gas circulation combustion method characterized by preheating.