GB1600500A - Method of feeding steam into a continuous open flame - Google Patents

Abstract

Although it is known to improve the efficiency of combustion by feeding steam into an open flame, the present invention achieves an extraordinary increase in efficiency by feeding steam from the vicinity of the burner directly into the flame at a controlled rate such that the steam exceeds 15% (and preferably is 60% to 90%) of the oxygen theoretically required for complete combustion, but less than the rate at which the flame would be extinguished.

Description

(54) A METHOD OF FEEDING STEAM INTO A CONTINUOUS OPEN FLAME (71) 1, LESLIE HERSCHEL GROVE, a citizen of the United States of America, of 707 East Hoyt Avenue, St. Paul, Minnesota 55106, United States of America, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to a method of improving efficiency of an open flame and to a furnace burner which can be operated with a continuous open flame and means for feeding steam directly into the flame.

It is known from U.S. Patents Nos.

643,269 and 1,966,591 that the efficiency of combustion of a continuous open flame can be improved by feeding steam directly into the flame. By "continuous" is meant a flame which usually burns continuously for at least one minute at a time.

The present invention provides a method of improving the efficiency of a continuous open flame of a burner of a furnace comprising feeding steam from the vicinity of the burner into helical flow patterns directly into the flame at a controlled rate such that the oxygen of the steam exceeds 15",, of the oxygen theoretically required for complete combustion but less than the rate at which the flame would be extinguished.

In another aspect the present invention provides in a furnace, a burner which can be operated with a continuous open flame and means for feeding steam from the vicinity of the burner into helical flow patterns directly into the flame at a controlled rate such that the oxygen of the steam exceeds 15Go of the oxygen theoretically required for complete combustion but less than the rate at which the flame would be extinguished.

It appears that optimum results are attained when the rate is such that the steam furnishes 60 to 90",, more oxygen (as steam) than the oxygen (as air) which is theoretically required for complete combustion of the fuel. When the steam supplies more than 100% additional oxygen, the flame might be extinguished if the temperature of the steam is near 100"C before it is exposed to the heat of the flame.

If its temperature is higher, the steam may be fed into the flame at even greater rates without extinguishing the flame.

When the flame is shut off, the flow of steam should be interrupted until after the flame is re-ignited. Usually a delay of 5 to 10 seconds after reignition should be sufficient to insure against accidentally extinguishing the flame.

Where the fuel is gas, it is desirably mixed with the steam before being fed directly into the flame. Where the steam is generated from water, a fuel such as alcohol may be dissolved in the water. Where the steam is generated in drying a substance, the volatile matter may be a gaseous fuel.

The present invention also provides, in another aspect, drying apparatus comprising a furnace with a burner which can be operated with a continuous open flame, a drying chamber, means for applying heat from the furnace to the drying chamber, means for collecting volatiles emitted from the drying chamber and steam feeding means as defined above, for feeding the volatiles comprising steam directly into the open flame in use of the apparatus When the steam is first fed into a continuous open flame, any yellow or red colour disappears, and the entire flame becomes blue and lengthens in a pulsating manner. The maximum length of the pulsating flame substantially exceeds that of the unmodified flame. If the flame tends to grow to a length exceeding that of the combustion chamber. the flame should be directed into a devious (e.g., helical) path.

The invention is applicable to a variety of fuels including methane, petroleum oil, wood, coal and alcohol. Where the fuel contains significant amounts of water, its water content should be taken into account in calculating the maximum rate of adding water in the form of steam without danger of accidentally extinguishing the flame.

Under conditions of high ambient humidity, it may be desirable to take into account the quantity of water in the combustion air and to reduce the rate of applied steam accordingly to insure against extinguishing the flame. Under conditions of high humidity, the combustion air for natural gas may contain water in an amount furnishing oxygen (as water) about equalling 5"b of the oxygen (as air) theoretically required for complete combustion.

Depending upon the choice of fuel, a typical installation in the prior art may call for about 200 ó excess combustion air for maximum fuel efficiency. In the practice of the present invention, it is generally possible to reduce the combustion air to the theoretical level or even below. This by itself produces considerably increased heating efficiency, especially where the combustion air is supplied at ambient temperature. In a heating plant which draws combustion air from the area being heated, there is less danger of suffocation and less waste since the combustion air normally goes up the chimney.

In the practice of the present invention the elimination of excess combustion air is believed to provide greater assurance against accidentally extinguishing the flame when steam is being fed into the flame at very high rates.

For installations in which it would be inconvenient to reduce the flow of combustion air mechanically, part of the steam may be fed directly into the combustion air line to replace part of the combustion air.

When steam was applied at an optimum rate to the flame of a conventional alfalfa drier, the fuel consumption was reduced about 20to. By recirculating the steam emitted from the drying alfalfa to the flame, the total reduction in fuel consumption was about 35%, the additional saving apparently being due to combustion of gaseous fuel emitted from the alfalfa. Comparable savings in fuel consumption should be realized in the drying of other materials which evolve water, e.g., cotton, grain, milk, fish, eggs, wood, textiles, faeces and latex paint.

It is theorized that when the steam strikes the flame, some of the water disassociates into hydrogen and oxygen, and combustion of the hydrogen and the availability of nascent oxygen enhances the heat output.

Whether or not that theory is correct, the degree of increased efficiency of combustion is startling and of tremendous significance in this era of fuel shortages.

The present invention is further illustrated in the accompanying drawing wherein: Figure 1 is a schematic elevation, partlv cut away to a central section. of a rotary alfalfa drier; and Figure 2 is an enlarged cross section along line 2-2 of Figure 1.

As seen in Figure 1, a cylindrical hot-air furnace 10 which is lined with fire brick is connected to the central flue of a conventional drum-type alfalfa drier 12.

Alfalfa entering a belt-fed hopper 14 is drawn through the drier 12 in an S-shaped path by a thermostatically controlled blower 16 and through a duct 18 to a conventional cyclone separator 19. The dried alfalfa drops through a chute 20 while water and other volatiles from the alfalfa in the form of steam rise to a skimmer 22 and are drawn by the suction of a fan 24 through a conduit 26 and fed directly into the flame of the furnace 10. A humidistat (not shown) in the conduit 26 controls an intake 28 of additional steam as required to supply the furnace at the desired rate.

As seen in Figure 2, the furnace 10 is equipped with five gun-type burners 30. A series of vanes 32 directs the steam from the conduit 26 into helical flow patterns and thence directly into the flame of the burners.

The helical flow of the steam redirects the flame into a helical path, thus insuring good circulation both within the furnace 10 and within the flue of the drier 12.

Example In an experimental operation of apparatus as illustrated in Figures 1 and 2, the combustion chamber of the furnace was 1.07 m in diameter and 6 m in length.

Initially, alfalfa was fed into the hopper 14 at a rate of 3000 kg per hour and the blower 16 was operated at about 225 m3 per minute.

The steam produced reached a temperature of about 130"C in the duct 18 and about 115"C in the conduit 26.

As the steam began to be fed into the flame, the temperature of the drier 12 increased. The thermostatic controls had been -pre-adjusted to respond to such increase in temperature by reducing the ratio of combustion air to natural gas. That ratio was initially 34:1 and was gradually reduced to the theoretical 17:1, thus diminishing the cooling effect of the combustion air. The ability to operate at the theoretical ratio was deemed to be due in part to the effect of the steam feedback and in part to better mixing by virtue of greater turbulence. Before reaching the 17:1 ratio, two of the five burners had been shut off, and additional steam was being added through the intake 28. In steady operation, the total steam being fed into the flame was 0.74 kg per m3 of combustion air.

Before any steam was generated, the temperature of the furnace 10 was 20900 C.

After two burners had been shut off and additional steam was being added. the furnace temperature was 20700 C. The flame slowly pulsated to a maximum length extending well into the drier 12, thus substantially increasing the temperature in the drier. The rate at which the alfalfa was fed into the hopper was gradually increased to 4500 kg per hour and was dried at that faster rate as effectively as it was initially without any steam feedback. The more rapidly dried alfalfa reportedly had substantially higher protein content than was obtained using an unmodified, but otherwise identical drier. The operator of the equipment reported that the modified drier required only 2.59 joules/kg of water driven off as compared to 4.05 joules/kg without any feedback.

WHAT WE CLAIM IS: 1. A method of improving the efficiency of a continuous open flame of a burner of a furnace comprising feeding steam from the vicinity of the burner into helical flow patterns directly into the flame at a controlled rate such that the oxygen of the steam exceeds 150d of the oxygen theoretically required for complete combustion but less than the rate at which the flame would be extinguished.

'. A method as defined in Claim I wherein the steam includes gaseous fuel.

3. A method as defined in either of claim 1 or 2, wherein the rate is 60 to 90 O.

4. In a furnace, a burner which can be created with a continuous open flame and means for feeding steam from the vicinity of the burner into helical flow patterns directly into the flame at a controlled rate such that the oxygen of the steam exceeds 15 O of the oxygen theoretically required for complete combustion but less then the rate at which the flame would be extinguished.

5. A burner as defined in claim 4, wherein the rate for the means for feeding steam is 6U to 90o.

6. Drying apparatus comprising a furnace with a burner which can be operated with a continuous open flame, a drying chamber, means for applying heat from the furnace to the drying chamber, means for collecting volatiles emitted from the drying chamber and steam feeding means as defined in claim 4 means for feeding the volatiles comprising steam directly into the open flame in use of the apparatus.

7. Apparatus as defined in claim 6 and further including means for feeding additional steam into the open flame.

8. Apparatus as defined in claim 7 wherein the means for feeding the volatiles and the means for feeding additional steam together feed steam into the open flame at a rate such that the oxygen of the steam furnishes 60 to 90 Ó of the oxygen theoretically required for complete combustion.

9. Apparatus as defined in any of claims 6 to 8 wherein the flame of the furnace is at one end of a cylindrical combustion chamber, the other end of which is connected to a flue in the drying chamber.

10. Apparatus as defined in any of claims 6 to. 9 useful for drying an agricultural commodity in the drying chamber wherein the drying chamber is connected to means for separating the agricultural commodity from the volatiles and there is a conduit for carrying the volatiles from the separating means to the furnace.

11. Apparatus as defined in claim 10 wherein the separating means is a cyclone separator.

12. Drying apparatus according to Claim 6, substantially as described therein with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (12)

**WARNING** start of CLMS field may overlap end of DESC **. the total steam being fed into the flame was 0.74 kg per m3 of combustion air. Before any steam was generated, the temperature of the furnace 10 was 20900 C. After two burners had been shut off and additional steam was being added. the furnace temperature was 20700 C. The flame slowly pulsated to a maximum length extending well into the drier 12, thus substantially increasing the temperature in the drier. The rate at which the alfalfa was fed into the hopper was gradually increased to 4500 kg per hour and was dried at that faster rate as effectively as it was initially without any steam feedback. The more rapidly dried alfalfa reportedly had substantially higher protein content than was obtained using an unmodified, but otherwise identical drier. The operator of the equipment reported that the modified drier required only 2.59 joules/kg of water driven off as compared to 4.05 joules/kg without any feedback. WHAT WE CLAIM IS:

1. A method of improving the efficiency of a continuous open flame of a burner of a furnace comprising feeding steam from the vicinity of the burner into helical flow patterns directly into the flame at a controlled rate such that the oxygen of the steam exceeds 150d of the oxygen theoretically required for complete combustion but less than the rate at which the flame would be extinguished.

'. A method as defined in Claim I wherein the steam includes gaseous fuel.

3. A method as defined in either of claim 1 or 2, wherein the rate is 60 to 90 O.

4. In a furnace, a burner which can be created with a continuous open flame and means for feeding steam from the vicinity of the burner into helical flow patterns directly into the flame at a controlled rate such that the oxygen of the steam exceeds 15 O of the oxygen theoretically required for complete combustion but less then the rate at which the flame would be extinguished.

5. A burner as defined in claim 4, wherein the rate for the means for feeding steam is 6U to 90o.

6. Drying apparatus comprising a furnace with a burner which can be operated with a continuous open flame, a drying chamber, means for applying heat from the furnace to the drying chamber, means for collecting volatiles emitted from the drying chamber and steam feeding means as defined in claim 4 means for feeding the volatiles comprising steam directly into the open flame in use of the apparatus.

7. Apparatus as defined in claim 6 and further including means for feeding additional steam into the open flame.

8. Apparatus as defined in claim 7 wherein the means for feeding the volatiles and the means for feeding additional steam together feed steam into the open flame at a rate such that the oxygen of the steam furnishes 60 to 90 Ó of the oxygen theoretically required for complete combustion.

9. Apparatus as defined in any of claims 6 to 8 wherein the flame of the furnace is at one end of a cylindrical combustion chamber, the other end of which is connected to a flue in the drying chamber.

10. Apparatus as defined in any of claims 6 to. 9 useful for drying an agricultural commodity in the drying chamber wherein the drying chamber is connected to means for separating the agricultural commodity from the volatiles and there is a conduit for carrying the volatiles from the separating means to the furnace.

11. Apparatus as defined in claim 10 wherein the separating means is a cyclone separator.

12. Drying apparatus according to Claim 6, substantially as described therein with reference to the accompanying drawings.