Furnaces – Including noncombustible fluid supply means
Reexamination Certificate
2000-09-14
2001-12-25
Bennett, Henry (Department: 3749)
Furnaces
Including noncombustible fluid supply means
C110S301000, C110S302000, C110S308000, C126S077000, C126S146000
Reexamination Certificate
active
06332411
ABSTRACT:
TECHNICAL FIELD
The invention is intended for burning solid fuel (mainly fire-wood, e.g. woodworking waste products), in continuous mode of operation, with significant amount of heat released in the form of hot combustion products usable in wood-drying installations, for house heating, etc.
THE BACKGROUND ART
Fronted solid fuel furnaces with fire-grates have been known thus far: e.g., see U.S. Pat. No. 4,316,445, FR 2 482 702, GB 2 253 050, GB 2 089 969, GB 2 251 302, RU 2 027 953, RU 2 031 315. The presence of grates in those furnaces results in a complicated design and inconvenient maintenance. Besides, obtaining high temperatures in grate-equipped furnaces is prevented by the fact that such temperatures may destroy grates. Fronted charging used in those furnaces leads to excessive air inflow through the furnace door when new portions of fuel are charged. This, in turn, results in a lower temperature in the combustion chamber and, therefore, in an incomplete fuel combustion. Apart from that, a sharp increase of the volume of furnace gases leads to an increasing loss of heat carried away with outgoing gases. The above-listed imperfections bring down the efficiency of fuel combustion and power density of such furnaces and thus prevent them from being extensively used in industry.
There exists another type of solid fuel furnaces, with vertical shaft fuel charging into the combustion chamber. In such furnaces, the ashtray is located under the combustion chamber: see, e.g., EP 0 046248, DE 196 12 403.
To improve the burning efficiency, some types of furnaces provide for air supply to the combustion chamber. The air can be previously heated for an even greater efficiency: see, e.g., GB 1 569 696, DE 32 00 194, DE 32 45 587, EP 0124 945. The air thus supplied is called primary, secondary, or even tertiary air, depending on where and at which stage of burning it is supplied. The air-supply process is thoroughly monitored and controlled to ensure the necessary and safe burning. For this purpose, various auxiliary devices are used, which have to be permanently monitored by operating stuff. The slightest breakdown of these devices can upset the process of burning which, in turn; can result in various undesirable situations, and even in an emergency. Although such furnaces offer more efficiency that those listed above, it is clear that they have a more complicated design and are inconvenient for maintenance. They require special personnel training, and they do not allow for high-efficiency and high power-density burning.
SPECIFICATION
The object of the present invention is to get rid of the aforementioned imperfections found in analogous furnaces, i.e. to create a furnace simple in design and production, inexpensive, reliable, and convenient in service at all stages of maintenance, and featuring high efficiency of fuel burning and high power density. This purpose in ensured by the invention's features described below. Each of those features serves for a specific function, whereas taken together and interacting, they provide a solution to the problem.
In the furnace proposed, a shaft-loading hopper located over a combustion chamber is used. An expansion chamber is located behind the combustion chamber so that their long axes are coincident, the cross-section area of the expansion chamber exceeding the cross-section area of the combustion chamber. The furnace is provided with an exhaust pipe with forced ventilation serving for air exhaust. The heated air supply to the combustion chamber is effected in such a way as to provide for the suplied air temperature as close as possible to that of the expansion chamber gases and includes frontal, lateral and lower air supply. The frontal air supply to the combustion chamber includes several pipes located in the internal space of the expansion chamber; one end of each pipe is open to the atmosphere, while the other communicates with an inlet of the corresponding through channel, which is located inside the combustion chamber and along its walls; the outlet of the channel communicates with the internal space of the combustion chamber. The lateral air supply to the combustion chamber is designed in the form of through holes in the combustion chamber's lateral walls, which communicate with the internal space of the combustion chamber and with the through channels for frontal air supply. The lower air supply to the combustion chamber includes several channels located inside the combustion chamber and along its lower wall; similar to the frontal air-supply channels, one end the lower air-supply channels communicates with special pipes put in the expansion chamber for that purpose; the pipes, in turn, are open to the atmosphere. Each of those channels communicates with the internal space of the combustion chamber via through holes located in between. The common long axis of the combustion chamber and the expansion chamber can simultaneously be their symmetry axis. The long axes of the pipes located in the expansion chamber and those of the through channels located inside the combustion chamber and along its lateral and lower walls and communicating with the pipes, coincide and are parallel to each other and to the combustion and expansion chambers' common symmetry axis. The through holes providing for lateral air supply into the combustion chamber are grouped in pairs so that the axes of the holes in each pair intersect within the bounds of the neighboring half of the combustion chamber's internal space. The long axes of the through holes providing for lower air supply can be parallel to each other and at the same time perpendicular to the long axis of the channels located in the combustion chamber's lower wall. The loading hopper is provided with a cap installed with a clearance ensuring air access for the exhaust of water vapor and hot volatile fractions that form during wood pyrolysis. In case of the optimal furnace design the amounts of air entering the combustion chamber via frontal and lateral supplies are related as 10:1, while for frontal and lower supplies, this ratio is 100:1. These ratios should be taken into consideration when calculating the diameters and numbers of the through holes and channels via which the air is supplied into the combustion chamber. The lower air supply into the combustion chamber rules out ash caking. Inside the combustion chamber, between the outlets of the through channels (located inside the chamber and along its lateral walls) and the internal space of the combustion chamber's front wall located opposite to the outlets, a clearance is arranged serving for frontal air passage from the through channels to the combustion chamber. In the lower part of the expansion chamber there is a door for ash removal. To lower the combustion products' stream speed and to ensure ash settling in the expansion chamber, the cross-sectional area of the expansion chamber can be made significantly greater than that of the combustion chamber. The planes of the above-mentioned cross-sections of the combustion and extension chambers are perpendicular to their common axis of symmetry. The proposed furnace design allows for modular production using readily available and inexpensive materials, e.g., high-temperature ceramics. Pipes located in the expansion chamber are made of a material with a high heat transmission coefficient; the pipes' material, diameter and wall thickness should be taken into consideration when optimizing for suplied air temperatures as close as possible to those of the expansion chamber gases. Forced oxygen-enriched air can be supplied into the combustion chamber through the channels located in the lower wall of the latter to create special short-time high-temperature conditions. A maximum heat-insulation of the combustion chamber and expansion chamber is provided.
Shaft charging used in the proposed furnace ensures stable burning. A loading hopper located directly over the combustion chamber allows to prepare the fuel for combustion since in that way the fuel passes the stages of
Skrotskaya Olga P.
Skrotskaya Olga Panteleimonovna
Skrotsky Viktor Georgievich
Bennett Henry
Collard & Roe P.C.
Rinehart K. B.
Skrotskaya Olga P.
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