Furnaces – Including means to feed solid fuel – Supply hopper; e.g. – magazine – etc.
Patent
1981-10-27
1983-12-20
Favors, Edward G.
Furnaces
Including means to feed solid fuel
Supply hopper; e.g., magazine, etc.
110108, 110116, 126 73, F23N 1300
Patent
active
044210400
DESCRIPTION:
BRIEF SUMMARY
The present invention is concerned with a furnace for combustion of wood fuel and other similar non-slagging bio-fuels like peat, etc., said fuels kept in a container. These fuels are characterized also by a low ash content and considerable production of pyrolysis gas during heating with limited supply of air already at comparatively low temperatures. The residues which are formed during the pyrolysis are also quite reactive in the final processes of gasification and combustion.
This category of fuels is potentially very attractive from an environmental point of view because of, among other things, a frequently very low sulphur content. On the contrary these fuels contain organic nitrogen which gives nitrogen oxides also at rather low temperatures of combustion.
The thermochemical properties which have been indicated above have, however, so far constituted a complication. The large production of pyrolysis gas already at low temperatures constitutes a risk for uncontrolled emissions of cancerogenic polyaromatic compounds as well as precipitation of so-called creosote or tar in the chimney. Chimney fires in houses with wood burners have caused considerable damage.
During the last years the attention has been focussed on the emissions of cancerogenic substances in the combustion of fossil fuels as well as bio-fuels such as wood and peat. The risk for such emissions because of incomplete combustion is probably not negligible in combustion on a small scale with large pieces of fuel, e.g. logs, in furnaces which are primitive from a combustion technical point of view.
A primary purpose with the present invention is to supply a furnace which permits complete and environmentally acceptable combustion particularly of wood, peat and lignite also on a small scale for residential heat etc. with small emissions of nitrogen oxides, cancerogenic substances and particulate matter at a small excess of air.
A second purpose is to supply fast control of the heating power within wide limits to suit the actual demand.
A third purpose is to supply a simple procedure for charging with fuel with possibility to do something with the fuel in the fuel container if something should go wrong.
A fourth purpose is to produce a high efficiency and a high final temperature of combustion at good fuel economy and efficient utilization of the fuel gas heat.
A fifth purpose is to create conditions for simultaneous delivery of different kinds of energy from one and the same central unit from hot air for driers heated with hot air and saunas to warm water and warm air for residential heat etc.
A sixth purpose is to achieve the advantages enlisted above and corresponding properties also when burning fuel in the form of larger pieces like logs, briquettes, wood rods (compacted wood), pellets etc.
The invention will also produce a number of other advantages which will be evident from the following description.
The furnace according to the invention has been developed particularly for bio-fuels like wood and peat but can also be used with other fuels like lignite, etc. The furnace is also particularly suited for burning of boiler wood and logs but may also be fuelled with chips and other fuels in a finely divided shape. The furnace and its grid can be dimensioned and designed in detail for the fuel to be preferred.
The invention relies on a unique combination of geometrical and combustion chemical principles. A new principle of design has been derived for the functional elements of the furnace to permit a new combustion process which is suitable for the special properties of said preferred fuels as well as satisfying the above requirements with respect to complete and efficient combustion etc.
Many attempts have been made to design furnaces for efficient and complete combustion of wood fuels frequently in connection with container burning. Natural measures have been pre-heating of the combustion air, supply of secondary air in a special flame space or a design which forces developed gases through the hearth.
The Swedish Patent No. 6251 thus describ
REFERENCES:
patent: 1723182 (1929-08-01), Kohout
patent: 2469639 (1949-05-01), Franklin
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