US2548656A - Furnace for burning low-grade fuel, including air-cooled partition walls - Google Patents

Description

April 10, 1951 2,548,656

R. DOLEZAL FURNACE FOR BURNING LOW-GRADE FUEL, INCLUDING AIR-COOLED PARTITION WALLS Filed Oct. 22, 1948 IN! 'EN TOR.

Patented Apr. 10, 1 951 FURNACE FOR BURNING Low-GRADE FUEL, INCLUDING AIR-COOLED PAR- TITION WALLS Richard Doleial, Vitkovice, Czechoslovakia, as-

signor to Vitkovick ZelezarnyKlementa Gottwalda, Narodni Podnik, Ostrava, Czechoslovakia, a corporation of Czechoslovakia- Application October 22, 1948, Serial No. 56,031 In Czechoslovakia October 25, 1947 3 Claims. (01. 110 2s) My invention relates to a furnace of high efficiency which may be used with advantage for burning therein poo coal having a high water content and ashes of a high melting point.

The object of my invention is to attain the highest possible temperature in the furnace to effect a perfect smelting of the coal ashes. For this purpose combustion air is used for cooling the walls enclosing the flames within the combustion chamber, and the heat taken from said 'walls is returned with the combustion air into the combustion chamber. Consequently the degree of cooling of the chamber walls has practically no effect on the final temperature of the gases at their discharge from the combustion chamber. To make possible the use of commonly used materials for the construction of these air-cooled walls, it is imperative that the temperature of these walls does not exceed 1000 C. To that end it is necessary to increase the coeflicient of heat transfer to the cooling air, e. g. by increasing the air speed, and to reduce the coefiicient of heat transfer from the flame, which heat transfer results predominantly from radiation (90% or more) at high temperatures (1600 to 1800 0.). v

The reduction of heat transfer by radiation from the flue gases is achieved according to my invention by partitioning the combustion chamber into smaller combustion spaces by a plurality of walls, thus reducing the radiating portion of the flame for it is well known that the radiation intensity of a flame and of gases in general is linearly dependent on the thickness of the radiating layer. Thereby the coefficient of heat transfer by radiation is reduced and the surface temperature of the walls and of the partitions decreases in the direction of the temperature of the cooling air. By these means the radiation coefficient C in the Stefan-Boltzmann equation expressed in kcal./m. h.K. (i. e. kilo-calories per square meter per hour and degree Kelvin to'the fourth power, degrees Kelvin equals degrees C.+2'73 or absolute temperature), is reduced from a value of :3.5 kcal./m. h.K. common to wide combustion chambers, to a value of (3:1 kcaL/mFhPK. even in the region of a luminous unspent flame.

The objects of my invention will be fully understood from the following specification taken with the accompanying drawing in which one embodiment is illustrated.

Fig. 1 shows a longitudinal section along l--I in Fig. 2, and

Fig. 2 across section along 2-2 in Fig. 1.

The combustion chamber is surrounded by a jacket 0 and is divided into five narrow combustion channels I) by means-of air-cooled hollow or channeled partition walls a. The combustion air, supplied by compressor or pump d, flows as indicated by dotted arrows along baffles i through the hollow jacket walls and partition walls a, is heated and finally mixed with the coal dust from burners e. The combustion in the narrow spaces 1) takes place at very high temperatures, since the amount of heat transferred by radiation to the walls a is reduced to a minimum by the narrowing of the radiating layer of the flame in the channels b which acquire the characteristics of a non-cooled combustion chamber. The melted ashes from the hot heating gases settle out on the partition walls a and flow downward until they drop to the bottom; there the layer of slag g exercizes a further beneficial insulation effect on the partition walls. The slag g may be removed from the combustion chamber through the bottom opening h into a water channel 7c or the like.

The combustion gases are discharged through the outlet 1 and may be further utilized, for example in steam boilers or the like. A regulation of the furnace may be accomplished by turningoff some of the burners e as the load decreases by shut-off devices such as valves 0; cooling air is then also prevented for example by shutting flaps not shown in the drawing from entering the air channels in the jacket walls and in the partition walls which encompass the combustion space into which the turned-off burner was previously blowing its flame. Thus the ratio between fuel and air as required for economical combustion remains constant and adecrease in the rate of flow of the air in the remaining wall channels, a diminution of the heat transfer coefficient on the side of cooling air, and arise in the wall temperature are prevented.

The partition walls built in the manner described above have an-effect opposite to thatof similar division walls constructed with boiler or super-heater tubes, which are used with the object of a more eflicient exploitation of the combustion or cooling chamber space; in the latter case, the distance between the partition Walls rand thus the thickness of the divided stream is selected with the view of obtaining thehighest radiation coefficient possible under the circumstances, and achieving the maximum heat transfer by radiation, so that the wall temperature also reaches its maximum, the latter increasing linearly with the quantity of heat passing through the surface. By installing partition walls made of boiler or super-heater tubes in the combustion chamber it is also sought to increase its cooling and thus to reduce the temperature of heating gases in order to preclude any possible smelting of the ashes; it is, therefore, apparent that the function of these Walls is difierent from the function of the partitions used in my new furnace.

Although only one embodiment of my invention has been shown and described by way of illustration, it will be understood that it may be constructed in various other embodiments which come Within the scope of the appended claims.

What I claim as my invention is:

l. Furnace for burning dust from poor coal comprising in combination walls forming a combustion chamber, a plurality of air-cooled channeled partitions traversing said chamber in one direction and dividing the same into narrow essentially vertical channels, at least one burner for the coal dust mounted on top of each of said channels, means supplying coal dust to said burners means to force combustion air through the channeled partitions, means forming a collecting conduit for the combustion air beyond said channeled partitions, said collecting conduit leading back into the combustion chamber and enclosing in its end portion the said burners.

2. Furnace for burning dust from poor coal comprising in combination walls forming a combustion chamber, a plurality of air-cooled channeled partitions traversing said chamber in one direction and dividing the same into narrow essentially vertical channels, air-conducting channels in the combustion chamber walls which are parallel to said partitions, at least one burner for the coal dust mounted on top of each of said channels, means supplying coal dust to said burners, means to force combustion air through said channeled walls and partitions, means forming a collecting conduit for the combustion air beyond said channeled walls and partitions, said collecting conduit leading back into the combustion chamber and enclosing in its end portion the said burners.

3. Furnace for burning dust from poor coal comprising in combination walls forming a combustion chamber, a plurality of air-cooled chal neled partitions traversing said chamber in one direction and dividing the same into narrow essentially vertical channels, air-conducting channels in the combustion chamber walls which are parallel to said partitions, at least one burner for the coal dust mounted on top of each of said channels, means supplying coal dust to said burners, means to force combustion air through said channeled walls and partitions, means forming a collecting conduit for the combustion air beyond said channeled walls and partitions, saidcollecting conduit leading back into the combustion chamber and enclosing in its end portion the said burners, means to individually shutofi each burner from the coal dust supply, and means to individually shut-off the air flow from each channeled Wall and partition.

RICHARD DQLEZAL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 577,240 Edgar Feb. 16, 1897 924,548 Gerdes June 8, 1909 1,828,839 Hawke Oct. 27, 1931 2,096,821 Noble Oct. 26, 1937

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