Furnaces – With control means responsive to a sensed condition – Feed control
Patent
1985-09-24
1987-01-13
Makay, Albert J.
Furnaces
With control means responsive to a sensed condition
Feed control
110104B, 110265, 236 15BA, 236 15BD, F23N 518
Patent
active
046355677
DESCRIPTION:
BRIEF SUMMARY
In a known form of furnace, several burners are provided with pulverized fuel from a single source, such as a mill, being conveyed from the source in primary air through a single duct to a splitter. Further ducts lead from the splitter, one to each of the burners. The splitter is intended to divide the fuel that flows through it into two or more constant (usually equal) proportions. The division may turn out to be not quite what was intended and might, in any case, vary during operation of the furnace and for the efficient control of the combustion and the maximum efficiency of the plant, particularly with low NO.sub.x combustion systems, it is desirable to know what the fuel flow to each of the burners is.
By means of the present proposal, it is possible to determine the pulverized fuel flow to each burner by reference to the total fuel to a splitter from which the burners depend for, say, a plant that is being commissioned.
According to the present invention, there is provided in the operation of a burner connected in parallel with one or more other burners to a splitter to which pulverized fuel is supplied in a stream of primary air, supplying secondary air to each of the burners so that combustion of the fuel supplied by the burner occurs in optimum conditions, deriving a measure of the total air supply to each of the burners, measuring the total supply of fuel to the splitter, and deriving from that and the ratio of the air supplies the amounts of fuel that are supplied to each of the burners.
In apparatus by which that method may be carried out, there is a plurality of burners supplied in parallel by a single splitter with pulverized fuel entrained in primary air, means by which the flow of fuel to the splitter may be measured, means by which the flow of primary air to the splitter may be measured, means for determining when the flame at each burner is burning under optimum conditions, means for providing a variable supply of secondary air to each burner so that optimum conditions may be established, means for measuring the secondary air supply at optimum conditions and means for deriving from a ratio of the air supplies to each burner and the total fuel supply the amounts of fuel that are supplied to each burner.
By way of example, an embodiment of the invention will now be described with reference to the accompanying schematic drawing in which:
FIG. 1 indicates a three-way splitter;
FIG. 2 indicates apparatus associated with one of the three burners that are supplied by the splitter; and
FIG. 3 indicates apparatus from which information about the flow of fuel to a burner may be obtained.
In FIG. 1, the numeral 1 indicates a splitter of known kind to which are connected, by pipes I.II and III, burners of which one, IIA is denoted in FIG. 2. The splitter is intended to divide the fuel supplied to it in three equal parts. The fuel is pulverized coal; coal is supplied at a known rate TF (measured by known techniques) to the mill 3 through a supply duct 4 and the coal that is pulverized in the mill 3 is entrained in primary air led to the mill through duct 5. The duct 5 contains an aerofoil insert; using a known technique, pressures pa1 and pa2 at the aerofoil insert are taken to enable a measure to be derived of the amount of primary air flowing to the mill 3 and thence through the splitters. In has been found that while the division of fuel at the splitter may vary, the air is divided into its intended portions (in this case, thirds) with adequate consistency.
Each burner is provided with its own adjustable supply of secondary air, flowing to the burner through a duct 10. The duct 10 includes a venturi section 11; again it is known how to deduce air flow from the pressures taken at, and downstream of, the venturi.
In operation of the burners, the supply of secondary air to each is varied until they are operating under optimum conditions.
To tell whether or not the burner is operating under optimum conditions, a known technique is used. This includes introducing intermittent and transient variations in
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Coleman Colin R.
Haftke Jozef J.
Warris Anne-Marie
Worley Norman G.
Babcock Power Limited
Kemon Solon B.
Makay Albert J.
Warner Steven E.
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