Stoker grates for circulating burning-up

Abstract

The invention relates to a stoker grates for circulating burning-up, wherein the existing reciprocal-type or chain-type grates are designed to be a long annular-shape with front and rear ends closed, resulting in burning-up of coal and thus overcoming the following defects of the existing coal-firing stokers: the coal remains on the grate shortly and can not be completely burn up, causing a waste of coal and low combustion efficiency.

Description

FIELD OF THE INVENTION [0001] The invention relates to a boiler stoker, specially, to the grate of horizontal circulating burning-up. DESCRIPTION OF THE PRIOR ART [0002] At present the grates for stoker-fired boiler can be classified in structure into two kinds, i.e. the reciprocating grate and the chain grate. The fuel is fed continuously to one end of the grate surface and travels horizontally across the grate as it burns. The residual ash is discharged from the opposite end. The above mentioned stoker grates have the following defects: 1) the coal is ignited mainly by means of the heat radiation from the furnace arch, the ignition begins from the upper layer towards the lower layer of the coal bed in a direction which is opposite to the direction of air flow, resulting in an unfavorable burning state and cause incomplete combustion; 2) the resident time of coal burning on the grate can not be long as the grate has a limited length, so the coal can not be fully burn up; and 3) the...

AI Technical Summary

Benefits of technology

[0003] An object of the present invention is to provide a boiler stoker for horizontal circulating burning-up, which overcome the following defects of the reciprocating and chain grates used for the existing coal-fired stokers: the resident time of coal burning on the grate is insufficient, the ignition of coal mainly by means of the heat radiation from the furnace, so the coal can not be fully burn up, and the fine coal particles in the bottom layer is easy to leak out from the vent slits of the grate and lead to a remarkable coal loss.

[0009] The invention, as compared with the existing art, has the following features: the grate has a long annular shape structure, the coal can be circulated and burned on the grate, the resident time of coal burning on the grate can be much longer, the bottom burning coal layer forms a sufficient ignition heat source, the new feeding coal covers on the circulating burning coal layer, the combustion begins from the lower layer towards upper layer and keeps the same direction as that of the air flow, so as to form a complete combustion state. The invention has the following benefit effects: 1) the coal can be totally burning up and combustion efficiency can be remarkably improved, (increased by more than 11% as compared to the conventional coal-firing stoker); 2) the blackness and the dust emission in the flue gas can be much lower; 3) combustion can be performed at low temperature (900° C.), desulphurization and the lower concentration of harmful NOx in the flue gas are achieved, and the effect can be corresponding to that of the circulating fluidized-bed furnace; 4) the coal of low heating value (as low as 12.56 MJ / kg) can be burnt; and 5) the comprehensive operation cost is only a half of that of a circulating fluidized-bed furnace.

Problems solved by technology

The above mentioned stoker grates have the following defects: 1) the coal is ignited mainly by means of the heat radiation from the furnace arch, the ignition begins from the upper layer towards the lower layer of the coal bed in a direction which is opposite to the direction of air flow, resulting in an unfavorable burning state and cause incomplete combustion; 2) the resident time of coal burning on the grate can not be long as the grate has a limited length, so the coal can not be fully burn up; and 3) the bottom layer of the coal is ignited at last, resulting in the fine coal particles to leak out from the vent slits of the grate and cause a big loss of coal.

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