US2079420A - Burner for firing furnaces with powdered fuel - Google Patents

Description

E. H. NIELSEN BURNER FOR FIRING FURNACES WITH POWDERED FUEL Filed June 23, 1950 2 Sheets-Sheet l May 4, 1937. E. NlELsl-:N

l BURNER FOR FIRING FURNACES WITH POWDERED FUEL Filed June 25. 1930 2 Sheets-Sheet Patented May 4, 1937 UNITED STATES PATENT OFFICE BURNER FOR FIRING FURNACES WITH P'OWDERED FUEL Application June 23,

6 Claims.

The present invention relates generally to burners. More particularly the invention relates to that type of burner which is adapted for use in firing annealing furnaces or the like with 5= powdered fuel.

In the operation or ring of annealing furnaces with powdered fuel, it is desirable in the first stage of an annealing operation, initially to raise the annealing temperature to approximately 1500o Fahr. in the shortest possible time. During the second stage, it is necessary to hold the temperature at the desired point, with the minimum quantity of fuel, and for this purpose it is desirable to limit the supply of fuel to that required to compensate for radiation and stack losses. During the third stage the castings are permitted to cool, and no fuel is required.

One object of the invention is to provide a burner of the type under consideration which 20v comprises means whereby fuel with air under pressure from a common source, such as a fan, will be simultaneously delivered at different velocities to bring expeditiously the temperature to the desired point for the first stage of opera- 25- tion in the furnace in which the burner is employed. Another object of the invention is to provide a burner of this character having simple and improved means by which the furnace will be fired with powdered fuel delivered into it at 30 one of the velocities, but of a lesser volume, and only sullicient to hold the temperature at the desired degree during the second stage of operation, to economize in fuel consumption.

In annealing furnaces the front end thereof is usually provided with an opening and doors to permit the annealing pots and castings to be placed into the annealing chamber, and the flue openings as well as the burner for delivering powdered fuel for firing the chamber are disposed at the rear end. Another object of the invention is to provide a burner which is adapted to deliver, during the first stage of annealing, powdered fuel and air under pressure at a high velocity to carry the heat to the front of the oven where radiation is most rapid on account of deficiency in insulation and leaks, and so that the heat will travel back to the flue openings, usually located at the rear of the oven, and also at a lower velocity to produce combustion in the rear portions of the chamber, to bring expeditiously the temperature up to the desired point.

A further object of the invention is to provide a burner which is designed to deliver powdered u fuel'into the combustion chamber of a furnace 0") andA embodies means for controlling the streams 1930, Serial No. 462,995

of either high or low velocity fuel as may be desired.

Other objects of the invention and the various advantages and characteristics of the present burner construction Will be apparent from a consideration of the following detailed description.

The invention consists in the several novel features which are hereinafter set forth and are more particularly dened by claims at the conclusion hereof.

In the drawings which accompany and form a part of the present specification or description and in which like numerals and letters of reference denote corresponding parts throughout the several views: Fig. A1 is a sectional view of a furnace equipped with a burner embodying the invention. Fig. 2 is a longitudinal section of the burner. Fig. 3 is a horizontal section on the line 3-3 of Fig. 2. Fig. 4 is a perspective of the outer tubular burner member, the nozzle being separated therefrom. Fig. 5 is a perspective of the inner tubular burner member. Fig. 6 is a transverse section on the line 6 6 of Fig. 3. Fig. '7 is a transverse section on the line 'I-'I of Fig. 2.

The invention is exemplified in connection with a furnace or oven A which is provided with an annealing chamber a, a rear wall a', having an opening a2 through which the fuel will be delivered into the furnace, and a front having an opening d5 closed by a door a3, through which the annealing pots and castings can be placed into and removed from the annealing chamber. Coal is delivered into a hopper '12, from which it is fed into a pulverizer B which may be of any suitable construction, such as the centrifugal type. A suction fan C draws the pulverized coal from the discharge chamber in the pulverizer and forces the powdered coal with air under pressure through a pipe c into a burner D which is mounted to discharge into the oven.

The burner D comprises an outer tubular member d and an inner tubular member d', and is provided at its outer or inlet end with a flange II which is secured by bolts I2 to a flange I3 on the end of pipe c. The outer end portion of the outer member d adjacent flange I I, is cylindrical, as at I4, and this cylindrical portion merges into a square medial portion I5. From said square portion, the outer member is flared and merges into a cylindrical end portion I 6 which is provided with a flange Il'. A discharge nozzle d2 has a cylindrical portion i8 which forms a continuation of the outer member @and is provided with a flange I9 which is secured to ange I1 by bolts 20. The cross sectional area of inlet portion lll and the medial portion l5 is sufficient for unretarded passage of the powdered fuel and air forced from pipe c. The square portion l5 of the outer member and the portion lil are flared outwardly toward the furnace so that the area thereof gradually increases from the square portion l5 to the inner or discharge end of the outer member. The purpose of this formation of the outer member is to direct an annular stream of powder and air into the furnace at a relatively low velocity to cause combustion of the fuel in, and to heat more particularly the rear portion of, the annealing chamber. 'Ihe in# ner tubular fuel delivery member d has a rectangular portion 2l at its inlet or outer end, and

its extreme outer terminal is positioned inwardthe square portion l5 of the outer member. The inner member merges from its rectangular outer portion 2l to a cylindrical inner or discharge end 22 which is coaxial with the discharge portion of outer member d, and is conterminous with the cylindrical portion it of the nozzle d2. The cross sectional area` of the inner member d is substantiallythe same throughout its length so that the powdered fuel and air passing therethrough will beA delivered into the combustion chamber and at a higher Velocity than the annular stream entering the furnace through the flared outer member, to cause flame and the products of combustion and heat to be delivered to and raise the temperature at the front portion of the furnace, The rectangular terminal 2l is elongated trans- Versely and its side walls are secured, as at 22', to the inside of the side-walls of the square porm tion I5 of the outer member, leaving passages 2 le in the outer member above and below the inner end portion 2| of the inner member, through which fuel and air will pass into the annular space between the discharge portions of the inner and outer members.

A pair of valves c, c' are fixed to cross-shafts 23 respectively, and are adapted to be swung into position to cut off the passage of fuel and air through the passages 2 Ia into the outer member d of the burner. These valves may also be swung into alignment with the top and bottom walls of the outer end portion 2| of inner member d' to permit the powdered fuel and air to pass through both the inner and outer members d, d. 'Ih'ese valves may also be swung together, should it be desired for any special reason, to cut off the entry of powdered fuel into the inner member d. Shafts 23 are each provided on the outside of the outer member with an arm 24 carrying at its outer end a set screw 25 to permit the valves to be set and locked into any of their desired positions. A boss 26 is formed on the outside of member d and has recesses to receive the screws 25 and indicate the positions of the valves.

The operation will be as follows: After the annealing oven has been Vloaded with annealing pots and castings, the door 0,3 will be closed and the pulverizer B and fan C will be operated to deliver powdered fuel and air into the oven. During the first stage of an annealing operation., the valves e, e will be set into alignment with the top and bottom walls of the rectangular portion 2| of the inner burner member d', so that powdered fuel, entering the inlet portion le of the outer member, will pass through the inner member d and also through passages 2 la and around the outside of the discharge portion of the inner member. The inner member, being of substantially constant area, will deliver a central stream of fuel and air at a relatively high velocity into the combustion chamber of the furnace, so that the heat and gases of combustion will be proiected to the front portion of the annealing chamber. Simultaneously, the outer burner member, which is flared towards the furnace, will discharge an Vannular streamV of powdered fuel and air at a relatively lower velocity for combustion and to produce heat adjacent the rear portion of the annealing'chamber 0r at a point remote from the front. By discharging the powdered fuel from the burner in streams of high and low velocities, the temperature of the entire chamber will be quickly raised, which is a desideratum in annealing. As soon as the annealing temperature, approximately 1500 Fahr. has been reached, thel valves e, e will be set to cut oif the passage of powdered fuel and air through, and the discharge of the annular stream from, the duct around the inner member and inside of the outer member, so that there willbe no low velocity discharge from the burner. The volume of fuel delivered by the fan C to the-burner will be reduced. This makes it possible to carry on the second stage of the annealing process with a small amount of fuel to economize in fuel consumption. Preferably, during this second stage, the fuel will be discharged into the furnace at a high velocity, so that the heat will be projected to the fronty end of the furnace where the heat losses from radiation and leaks around the doors are greater than at the rear end of the furnace. The heat, travelling back from the front of the annealing chamber to the usual fuel openings at the rear of the oven, suiiices to keep the rear portion of the chamber at the desired temperature.

The invention thus exemplifies an annealing oven or furnace fired with powdered fuel, and into which the fuel and air are delivered at different velocities during the stage when the temperature of the annealing chamber is being brought to the annealing point; by which a lesser volume of the fuel and air will be delivered or discharged into the furnace at one of the velocities, preferably the high velocity, and sufficient in volume to compensate for the heat losses; in which the members for simultaneously delivering the fuel at relatively different velocities are combined in a l single burner which is simple in construction and can be easily manipulated. The invention also exemplifies an economical method of firing ovens with powdered coal. l

The invention is not to be understood as rev stricted to the details set forth, since these may be modified within the scope ofthe appended claims, without departing from the spirit and scope of the invention.

Having thus described the invention, what I claim as new and desire to secure by Letters Patent, is:

l. In a burner for use in firing a furnace or like heating apparatus, the combination of a pair of coaxially arranged tubular members adapted to discharge into the furnace, and means connected to the inlet end of the outer tubular member for delivering a mixture of powdered fuel and air under pressure from a common source into the inlet ends of both members for discharge into the furnace, one of the members being of substantially constant cross sectional area from one end thereof to the other so as to deliver the portion of the mixture passing therethrough into the furnace at a relatively high velocity and the other member being of increasing cross sectional area toward its discharge end so as to deliver the portion of the mixture passing therethrough into the furnace at a relatively lower velocity.

2. In a burner for use in firing a furnace or like heating apparatus, the combination of a pair of coaxially arranged tubular members adapted to discharge into the furnace, means connected to the inlet end of the outer tubular member for delivering a mixture of powdered fuel and air under pressure from a common source into the inlet ends of both members for discharge into the furnace, 'one of the members being of substantially constant cross sectional area from one end thereof to the other so as to deliver the portion of the mixture passing therethrough into the furnace at a relatively high velocity and the other member being of increasing cross sectional area toward its discharge end so as to deliver the portion of the mixture passing therethrough into the furnace at a relatively lower velocity, and valve means for cutting off the flow of the mixture through the said other member.

3. In a burner for use in firing a furnace or like heating apparatus, the combination of a tubular member adapted to discharge into the furnace, a second tubular member also adapted to discharge into the furnace and extending around and spaced from the rst mentioned member, and means connected to the inlet end of the second tubular member for delivering a mixture of powdered fuel and air under pressure from a common source into the inlet ends of both members for discharge into the furnace, said rst mentioned member being of substantially constant cross sectional area from the inlet end thereof to the discharge end so that the portion of the mixture passing therethrough into the furnace is delivered at a relatively high velocity and the second member being of increasing cross sectional area towards its discharge end so that the portion of the mixture passing therethrough into the furnace is delivered at a relatively lower velocity.

4. In a burner for use in firing a furnace or like heating apparatus, the combination of a tubular member adapted to discharge into the furnace, a second tubular member also adapted to discharge into the furnace and extending around and spaced from the rst mentioned member, means connected to the inlet end of the second tubular member for delivering a mixture of powdered fuel and air under pressure from a common source into the inlet ends of both members for discharge into the furnace, said first mentioned member being of substantially constant cross sectional area from the inlet end thereof to the discharge end so that the portion of the mixture passing therethrough into the furnace is delivered at a relatively high velocity and the second member being of increasing cross sectional area towards its discharge end so that the portion of the mixture passing therethrough into the furnace is delivered at a relatively lower velocity, and valve means for cutting off the flow of the mixture through said second member.

5. In a burner for use in firing a furnace or like heating apparatus, the combination of a tubular member having one end thereof adapted to discharge into the furnace and its other end substantially polygonal, a second tubular member surrounding and spaced from the rst mentioned member and having one end thereof adapted to discharge into the furnace, and a polygonal medial portion in which the polygonal end of the first mentioned member terminates, means connected to the other end of the second tubular member for delivering a mixture of powdered fuel and air under pressure from a common source into both of the members for discharge into the furnace, said first mentioned member being of substantially constant cross sectional area from one end thereof to the other so as to deliver the portion of the mixture passing therethrough into the furnace at a relatively high velocity and said second member being of increasing cross sectional area towards its discharge end so as to deliver its portion of the mixture into the furnace at a relatively lower velocity, and valve means in said other end of the second member for controlling the flow of mixture through either of the two members.

6. In a burner for use in firing a furnace or like heating apparatus, the combination of a tubular member adapted to discharge into the furnace, a second tubular member also adapted to discharge into the furnace and extending around and spaced from the rst mentioned member and having the inlet end thereof projecting beyond the inlet end of said rst mentioned member, means connected to the inlet end of the second tubular member for delivering a mixture of powdered fuel and air under pressure from a common source into the inlet ends of both members for discharge into the furnace, said first mentioned member being of substantially constant cross sectional area from the inlet end thereof to the discharge end so that the portion of the mixture passing therethrough into the furnace is delivered at a relatively high velocity and the second member being of increasing cross sectional area towards its discharge end so that the portion of the mixture passing therethrough into the furnace is delivered at a relatively lower velocity,

and valve means in the projecting portion of the inlet end of the second member for cutting off the iiow of mixture through either of the two mem-1 bers.

EMANUEL I-I. NIELSEN.

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