Furnaces – Process – Burning pulverized fuel
Patent
1985-06-24
1986-11-11
Favors, Edward G.
Furnaces
Process
Burning pulverized fuel
110214, 110259, 110269, 110329, F23D 100
Patent
active
046215840
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention refers to a method and a device for firing solid fuels, substantially in the form of lumps or pieces, in a furnace having a combustion chamber with a substantially horizontal bottom, upon which is maintained a fuel bed with relatively great thickness while supplying fuel within the very bed, through which bed primary combustion air is fed from below through mutually spaced primary air passages in the combustion chamber bottom, the combustion gas which leaves the chamber furthermore being subjected to a subsequent secondary combustion in a secondary combustion chamber after addition of secondary combustion air.
Combustion methods and devices of this kind are previously known and it is also known to fire such furnaces with insufficient supply of primary air, which implies that above the fuel bed is formed an energy-rich gas which after admixing with secondary air is burnt in a secondary combustion chamber. A problem in connection with firing methods and devices of this kind resides in the removal of ash and slag from the combustion chamber. Conventionally, the bottom of the combustion chamber is constituted by a grid-like grate through which primary air is supplied. Ash and slag have to be removed by hand after stopping the fuel supply and complete down-burning of the fuel bed.
Another problem in connection with previously known firing methods and furnaces of the above-stated kind is that it is extremely difficult to obtain a uniform distribution of the primary air flow over the entire cross section of the combustion chamber. This leads to a non-uniform combustion and impaired efficiency.
Partly, the above-stated problems are dependent on each other since the formation of slag within one area of the combustion chamber cross section causes an impaired air flow within said area such that the air distribution becomes non-uniform. This causes an unsuitable combustion temperature and slag formation.
SUMMARY OF THE PRESENT INVENTION
The main object of the present invention is to eliminate the above problems and to provide for effective removal of ash and other combustion residues and provide uniform distribution of the primary air flow of the entire cross section of the combustion chamber. According to the method of the present invention this is obtained by supplying fuel into the bed positively and intermittently at a position on an end wall of the combustion chamber at a vertical height spaced above the bottom of the latter but below the upper surface of the fuel bed during operation of the furnace and substantially in horizontal direction, whereby at each occasion newly supplied fuel provides an agitation of the bed such that a concentrated combustion zone is obtained at the upper portion of the bed while finally combusted fuel in the form of ash is progressively moved towards the opposite end wall of the combustion chamber and downwards and along the combustion chamber bottom, wherefrom the ash is moved in horizontal direction during furnace operation.
The invention also provides for a device for carrying out the inventive firing method in a furnace having a substantially horizontal bottom, upon which is maintained a fuel bed with relatively great thickness. Fuel is supplied within the bed, and primary combustion air is fed from below through the combustion chamber bottom. The chamber bottom consists of a plurality of mutually substantially parallel beams, which extend over the whole width of the combustion chamber and which are mutually spaced so as to form gaps therebetween. The combustion chamber in its upper portion furthermore has an orifice for admixing secondary air to the combustion gas leaving the combustion chamber in order to carry out a subsequent secondary combustion in a secondary combustion chamber. According to the present invention the device is distinguished in that the fuel supply inlet is located at a position on an end wall of the combustion chamber at a vertical height spaced above the bottom of the latter but below the upper surface o
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patent: 1960718 (1934-05-01), Standifer et al.
patent: 2476567 (1949-07-01), Sparks
patent: 2592730 (1952-04-01), Perkins
patent: 3358625 (1967-12-01), Jones
patent: 3599610 (1971-08-01), Spector
Asplund Frank E. W.
Jantze Ulrika M.
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