US1754965A

US1754965A - Oombttstion-contbol appabattts

Info

Publication number: US1754965A
Authority: US
Publication date: 1930-04-15
Anticipated expiration: 1947-04-15

Description

April 15, 1930. T A PEEB ES 1,754,965

COMBUST ION CONTROL APPARATUS Filed April 5, 1928 .INVENTOR.

Byfi z w ATTORNEYS.

Patented Apr. 15, 1930 UNITED STATES PATENT OFFICE Home A. P IOUN'I. LEBANON, PENNSYLVANIA, ASSIG'IQIOR '10 JOHN M. HOIWOOD, OI DOBMONT, PENNSYLVANIA COMBUSTION-CONTROL APPARATUS Application med April 5,

This invention relates to furnaces, and more particularly to a system for controlling and varying the combustion of fuel therein.

In furnaces burning combustible mixtures of fuel and'air'it is customa to vary the uantity of each delivered to t e combustion c amber in accordance with the demand for the furnace output, which may be steam. For n exam le, in the operation of a furnace usmg 'pow ered coal, it is frequently thecase that the supply of coal to thefurnace w1ll be re ulated by the flow of air thereto, and th1s,--1n turn, is controlled by the demand for steam or other furnace output, In such a case the draft loss through the boiler is relied upon as a measure of the air supply, for the purpose of controlling the delivery of coal, but it will .be apparent that this draft loss is dependent upon and will vary as a result of factors other than the volume flow of air, such as the condition of the bafiies, the accumulation of soot and the cooling of the gases, and hence this form of control is uncertain and variable,

An object of this invention is to provide an improved arrangement for regulating and controlling furnace combustion,

A further object is to provide an improved combustion control for furnaces burnin a mixture of fuel and air, of such construction and arrangement that the delivery of fuel is varied directly and proportionately to variations in the air flow.

A still further object is to provide a combustion control for furnaces-burning powdered fuel of such construction and arrangement that the delivery of fuel and air to the furnace chamber are coordinated and regulfated in'accordance with the demand thereor.

These and other objects which will be apparent to those skilled in this particular art are accomplished by means of the invention illustrated inthe accom anying drawing which shows a diagrammatic layout of a combustion control apparatus constructed in ac- 'cordance with one embodiment of this invention.

I The particular embodiment of this inven- 1928. Serial No. 287,828.

tion which has been chosen for the purposes of illustration is shown in connection with a steam generating powdered fuel boiler furnace 5, having an ofl'take header 6 for the steam generated in the boiler chamber. A burner 7 of any desired type is associated with the furnace in the usual manner and is adapted to receive powdered coal from any suitab e feeder 8 through a delivery line 9. The feeder is operated from any suitable source of power such, for example, as an electric motor 10 connected to an electric circuit 11. Air is delivered to the burner and furnace through a supply line 12- from a forced draft fan 13 driven from any suitable source of power such, for example, as the electric motor 14 connected to the electric circuit 15. The speed of the motor 14 and the blower 13 is directly controlled by a suitable rheostat 16 or similar mechanism. A rheostat 17 is associated with the coal feeder o crating motor 10 for controlling the speed tl'l feed of coal. The air blower 13 is provided with an intake line 18 and an inlet orifice 19 of definite size through which the air is drawn.

The present invention contemplates the provision of suitable mechanism for controlling the delivery of fuel and air to'the furnace in accordance with the demand for steam. In the illustrated embodiment of this invention this mechanism is of such arrangement that the operation of the air blower is varied and controlled by the steam pressure in the drum or oiftake header 6 which, in turn, depends upon the demand, and the operation of the coal feeder 8 is varied pro portionately with variations in the speed of the air blower, and directly as a result of such variations. As illustrated, this mechanism includes a pressure responsive regulator 20 of any desired type but, preferably, constructed in accordance with the regulator described in Patent No. 1,371,243, to Hopwood, issued March 15, 1921, and which is directly connected to the ofitake header 6 by a suitable pressure tap 21. A link 22 connects the vertically movable frame of the regulator to the operating arm 23 of the blower-controlling rheostat 16. It will be apparent that ereof and the the speed of the blower motor 14 and the volume of air delivered to the combustion chamber of the furnace will vary as a result of variations in the steam pressure of the oil'- take header, with the result that when the steam pressure falls during periods of high demand, the rheostat 16 is so operated by the regulator 20 as to increase the s eed of the motor 14 and the volume of air elivered to the furnace, and vice versa.

The s eed of operation of the coal feeder 8 is varie in accordance with and proportionately to the variations in the delivery of air, and the changes in speed of operation of the feeder are caused as a result of variation of air flow through the blower 13. The mechanism for accomplishing this result, as illustrated, includes a regulator 24 such, for example, as that described in Patent No. 1,338,923 of May 4, 1920, and which is operated by variations in the flow of air through the blower and for this purpose is connected to the air intake 18 through a suitable pressure tap 25. This regulator operates simi larly to the regulator 20, and the vertically movable frame 26 thereof is connected to a rack and pinion 27 for operating a cam 28 which is associated with a lever 29 normally held in contact with the cam by weights 30, or the like, and connected by a link 31 to the operatin arm 32 of the rheostat 17, which controls tl ie speed of operation of the coal feeder motor 10.

The operating arm 33 of the furnace outlet damper 34 is connected by a link 35 to the vertically movable frame 36 of another regulator 37 adapted to be operated by the pressure in thecombustion chamber through a suitable pressure tap 38. As a result, a uniform draft 15 obtained in the combustion chamber even under the varying quantities of fuel and air fed thereto.

In view of the fact that the regulator 24 for controlling operation of the coal feeder 8 is operated in accordance with variations in the pressure in the fan intake 18, and that this pressure varies in accordance with the square of the air flow, it will be readily apparent that a direct connection between the regulator 24 and the rheostat 17 or motor 10 would provide too rapid an increase of fuel supply upon increase 1n operation of the blower, unless the rheostat 17 were so designed as to, in and of itself, counteract this condition. The

illustrated mechanism provides one convenient way of varying the feed of coal in direct proportion to variations in the supply of air. The cam 28 will be so formed as to reduce the relative movement of the regulator frame 26 and the rheostat arm 32 so as to overcome the above condition and cause the rate of coal feed to vary directly in accordance with variations in the rate of air flow. It will, of course, be readily understood that other forms of compensating mechanism can be employed.

- The regulator 24 is modified somewhat frbm the usual construction in that it is provided with a pendulum 40 and weight 41 which are rigidly attached to the float beam 42 of the regulator and that the weight 41 hangs perpendicularl when the float beam is at one end of its trave as illustrated. When it is in this position, the weight, of course, has no effect on the balancing of the float mechanism. After the left hand float is connected to the atmosphere and the right hand float is connected to the blower intake 18, as illustrated, a sub-atmospheric pressure under the right hand float caused by operation of the blower will move the right hand float downwardly and the counterweight will move to the left. The force required to move the counterweight from a vertical position will be determined by the sub-atmospheric pressure under the right hand float.

In operation, the speed of rotation of the blower 13 and, hence, the volume of air supplied to the burner 7 is controlled by the steam pressure in the ofi'take header 6, through the regulator 20 and the associated blower controlling rheostat 16. An increase in steam pressure in the header 6 will operate the regulator so as to decrease the speed of the blower motor 14 and reduce the volume of air supplied to the furnace. At the same time the coal feeder regulator 24 will be operated by the variations in pressure in the air intake 18 of the blower so as to control the coal feeder '8 through suitable compensating mechanism, such as that illustrated, to simultaneously and proportionately reduce the supply of coal to the furnace. During periods of high demand the s eed of operation and supply of both air an coal is increased in the same manner. It will, of course, be understood that coal is conveyed from the'feeder 8 to the burner by an air flow and it will also be understood by those skilled in the art that, if there is a constant amount of coal conveying air supplied, the adjustments are such that when no air is being delivered by the blower 13, the feeder is operating at such a speed that the air required for conveying the coal to the furnace is the correct amount for burning such coal.

Although I have described a preferred embodiment of this invention in specific detail, it will be apparent that various changes, additions, omissions and substitutions can be made therein without departing from the spirit of the invention or the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent is:

1. The combination with a boiler furnace for generating steam, of means for delivering fuel thereto, a blower for delivering air thereto, a constant size air inlet to said blower, a pressure responsive regulator operated by variations in the pressure of the steam outsteam,

- a constant size air inlet put of the boiler for varying the speed of operation of said blower, a pressure responsive regulator operated by variations in the air inlet of said blower for controllin the speed of operation of said fuel delivery means, a damper located in the furnace outlet and a pressure responsive regulator oper- I ated by the variations in the furnace pressure built up by the air and fuel feeding devices for controlling the position of said damper.

2. The method of regulating combustion in a boiler furnace generating steam, which consists in controlling the admission of air to said furnace through variations in the in controlling the admission a blower for supplying air thereto, a con stant size air inlet for said blower, a pressure responsive regulator operated by variations in steam pressure for controlling the speed of said blower for regulating admission of air to said furnace, a pressure responsive regulator attached to the air inlet pipe for controlling the fuel delivery means regulating the admission of fuel to said furnace, and means connected with said last mentioned regulator for controlling the fuel delivery means so that the fuel. will be introduced to said furnace in direct proportions to the variations in the supply of an.

4. The combination in a combustion control system for a boiler furnace generating of means for delivering fuel to said furnace, a blower for sup lying air thereto, or said blower, 'a pressure responsive regulator operated by variations in steam Eessure for controlling the admission of air to said furnace, and a pressure responsive regulator attached to the air inlet of said blower for controllin the admission of fuel to said furnace; sai last mentioned regulator being provided with a rack, a pinion having a cam thereon operated by said rack, whereby the relative movement of the regulator is reduced, to cause the rate of the coal feed to Vary directly in accordgnce with the variations in the rate of air In testimony whereof, I have hereunto subscribed my name this 3rd day of April,,1928.

THOMAS A. PEEBLES.