SU1751599A1 - Fluid bed combustion furnace firing-up method - Google Patents

Abstract

Use: when burning solid fuel in fluidized bed furnaces. SUMMARY OF THE INVENTION: The consumption of a liquefying agent after mixing the fuel with the bed is increased to the nominal value while maintaining the oxygen concentration in the flue gases of 2-4% by volume. When implementing this method, an additional effect is achieved by reducing the duration of the firing operation; moreover, the implementation of the method permits the ignition of the fluidized bed furnace to be organized in an explosion-proof mode and in a relatively short time.

Description

The invention relates to energy and can be used in the combustion of solid fuels in fluidized bed furnaces.

There is a known method of igniting a fluidized bed furnace, according to which the air is supplied periodically, alternating it with feeding portions of the layer material, the volume of each portion being 3-5% of the volume of the combustion chamber. Above the layer of inert material creates an ignition zone and a duration the air supply is matched to the flame penetration time in the lower part of the bed.

The disadvantage of this method is high metal consumption, since its implementation requires an additional hopper and a metering device for feeding inert material. In addition, this

The method does not preclude the formation of agglomerates from the bed material due to its local overheating at the moments when the air supply is stopped.

There is also known a method of igniting a fluidized bed furnace by heating the bed material to the ignition temperature of the fuel and then supplying the latter with the bed material while simultaneously supplying a liquefying agent with a constant flow rate and not less than the initial velocity of fluidization and removal of flue gases. Due to the fact that the heating of the material of the layer and the solid fuel mixed with it is carried out directly in the furnace, the need for additional devices is eliminated. At temperatures above the temperature of

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The fuel lamination layer is in a fluidized state, which reduces the possibility of its agglomeration.

However, when implementing this method, it is possible to release into the gas phase products of pyrolysis and incomplete combustion (H2, CO, CH-3). This is especially true for the period of heating the mixture of fuel with the material of the layer before ignition. In addition to the fact that the release of these objects into the atmosphere is an environmental hazard, their release can lead to a serious accident. The mixture with air containing a total of 5-6% H2, CO and Chk is explosive.

The closest to the proposed method is the ignition of a fluidized bed furnace by heating the bed material to the ignition temperature of the fuel and then supplying the latter with the bed material while simultaneously supplying the fluidizing agent with a constant flow rate and not less than the initial fluidization rate. During the ignition process, the oxygen content in the air at the beginning of the kindling is maintained in the range of 25–50%, which ensures an explosion-proof state.

However, a high concentration of oxygen in the furnace, if it burns there completely, cannot guarantee explosion safety in the convective part of the boiler.

The purpose of the invention is to increase explosion-proof and environmental cleanliness.

This goal is achieved in that according to the method of igniting a fluidized bed furnace by heating the bed material to the ignition temperature of the fuel and then supplying the latter with the bed material while simultaneously supplying the fluidizing agent with a constant flow rate and not less than the initial fluidization rate, and withdrawal the flue gases, the flow rate of the fluidizing agent after mixing the fuel with the bed is increased to the nominal value, while maintaining the oxygen concentration in the flue gases 2-4% by volume. Due to the fact that this oxygen binds combustible gases emitted during fuel heating, their concentration is reduced. Thus, its explosive limit is not reached and emissions of harmful gases into the atmosphere are reduced.

The operation of igniting the fluidized bed furnace consists in heating the bed material to the operating temperature of 800-1000 ° C.

The experiments were carried out on a machine with an air distribution grill area of 0.05 m2 and a height of 1.7 m. As

The material of the layer used fireclay chips of a fraction of 1-2 mm. The fuel is Kansko-Achinsk brown coal fraction of 0.5-3.0 mm.

Example 1. Layer material and fuel

mixed in a cold state, then heated. At the moment when the layer reaches the ignition temperature, the air flow rate is 70 m / h. In this period

the oxygen content in the exhaust gases is about 8% by volume. Then the temperature of the bed spontaneously rises, and the oxygen content decreases. When it reaches 2%, the air flow is gradually increased and brought to the nominal 180 m / h. There are no combustible components in the gases at the outlet of the furnace; ignition time is 42 minutes.

Example 2. The experiment was carried out analogously to example 1, but with a minimum oxygen concentration of 2%, and a maximum of 4%. Those. This example corresponds to the claims. The operating temperature (800 ° C) was reached after 4 cycles of increasing air flow. Combustible components in gases are absent, ignition time 28 min.

Example 3. The experiment makes analogies but, but the range of oxygen concentrations

shifted to a larger direction (4-6%). Combustible components in gases are absent, ignition time is 32 min.

Example 4. The experiment was carried out according to example 2, but the range of oxygen concentrations is shifted to the lower side (1-2%). At the outlet of the furnace, the gases contained 3% of combustible components, the ignition time was 27 minutes.

The presented examples show

that when the oxygen content in the flue gases is more than 2 vol.%, the combustible gases at the outlet from the furnace are practically absent. However, an increase in the oxygen concentration of more than 4 vol.% Leads to an increase in the duration of the ignition operation, which is inexpedient. Therefore, the proposed method makes it possible to realize the process of ignition of a fluidized-bed furnace in an explosion-proof mode without releasing combustible gases into the atmosphere in a relatively short time.

Claims (1)

The invention of the method of igniting a fluidized bed furnace by heating the bed material to the ignition temperature of the fuel and then supplying the latter with the bed material while simultaneously supplying the fluidizing agent with a constant flow rate and not less than the initial rate of fluidization and removal of the smoke agent after mixing the fuel with the bed exhaust gases, characterized in that, they increase to the nominal value at to increase explosion safety and to maintain the oxygen concentration in environmental cleanliness, consumption of fluidized-flue gases 2-4%.