US 4,765,258 AGranted

Method of optimizing combustion and the capture of pollutants during coal combustion in a cyclone combustor

AssigneeCoal Tech Corp.

InventorBert Zauderer

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Abstract

Coal combustion and the capture of pollutants are optimized by a method which applies two mechanisms for sulphur capture, one in which pulverized coal particles suspended in the gas stream in the injection zone of the combustor are affected by reaction with a suspended sorbent, and another in which the particles are reentrained in the gas stream by a "sand storm" effect near the wall of the combustor. Use of the two mechanisms results, in commercial scale cyclone combustors, in 70 to 90% sulphur capture at economical Ca/S ratios. The method also minimizes emission of ash by removal from the pulverized coal fuel particles too small to be retained in the combustor and too large to be completely burned in the combustor, minimizes reevolution of sulphur compounds from slag by rapid and continuous removal of slag from the combustor, minimizes emission of NO.sub.x pollutants by maintaining a favorable overall fuel-rich stoichiometry.

Claims14

Dependent claims

A method for the combustion of coal in a slagging cyclone combustor while minimizing the emission of ash particles and other pollutants, comprising the steps of:

pulverizing a quantity of coal;
removing from the pulverized coal particles too large to readily be burned in the combustor;
injecting the remaining pulverized coal particles into the combustor adjacent to a closed end wall of the combustor together with a stream of primary combustion air so as to form an air-fuel stream;
injecting into the combustor adjacent to the closed end wall a stream of secondary air in such a manner as to cause said air-fuel stream to flow helically within the combustor;
maintaining the velocity of said secondary air stream such that centrifugal force on said coal particles due to tangential gas velocity drives said particles toward the cylindrical wall of the combustor so that combustion of said coal particles is apportioned between and occurs both in the gas stream and on the walls of the combustor with most of said combustion occurring in the gas stream;
injecting into the combustor adjacent to the location at which the fuel-air stream is injected a pulverized sorbent capable of capturing sulphur compounds, whereby the sorbent being injected into a region within the combustor in which the local gas conditions are oxidizing and the temperature is lower than the average temperature of the combustor, the average stoichiometry of said combustor being reducing;
maintaining a liquid slag layer on the cylindrical wall of the combustor, the sulphur captured by the sorbent being removed from the cyclone as a result of the impingement and retention thereof on the slag layer, and the further steps of controlling by air cooling the temperature of the slag layer, and removing slag from the combustor in a time less than the time required for evolution of sulphur gas from the slag.

4 more elements

A method for the combustion of coal in a slagging cyclone combustor while minimizing the emission of ash particles and other pollutants, comprising the steps of:

pulverizing a quantity of coal;
removing from the pulverized coal particles too fine to be retained in the combustor and too large to readily be burned in the combustor;
injecting the remaining pulverized coal into the combustor adjacent to a closed end wall of the combustor together with a stream of primary combustion air to form an air-fuel steam;
injecting into the combustor adjacent to the closed end wall a stream of secondary air in such a manner as to cause said air fuel stream to flow helically within the combustor with said secondary air stream surrounding said air-fuel stream so that centrifugal force on said coal particles drives said particles toward the cylindrical wall of the combustor;
maintaining the velocity of said air-fuel stream such that gasification of the coal particles is apportioned between and occurs both in the gas stream and on the walls of the combustion chamber;
gasifying most of the injected coal while the coal is suspended in the gas stream, said step of gasifying in the gas stream being performed under fuel rich conditions of about 50 to 70% stoichiometric conditions;
and gasifying substantially all of the remainder of the coal on the wall of the combustor so that the ash is retained in slag on the wall of the combustor;
and the further step of removing the slag from the combustor, said step of removing being performed in a time less than the time required for the revolution of sulphur gas from the slag.

5 more elements

Dependencies are inferred from the claim text.