US2243909A

US2243909A - Means for controlling superheat

Info

Publication number: US2243909A
Application number: US201073A
Authority: US
Inventors: Kruger Theodore
Original assignee: Combustion Engineering Inc
Current assignee: Combustion Engineering Inc
Priority date: 1938-04-09
Filing date: 1938-04-09
Publication date: 1941-06-03
Anticipated expiration: 1958-06-03

Description

June 3, 1941;. 1-. KRUGER MEANS FOR CONTROLLING SUPERHEAT Filed April 9, 1938 3 Sheets-Sheet 1 INVENTQR mla/w/fliqger ATTORNEY June 3, 1941. KRUGER 2,243,909

MEANS FOR CONTROLLING SUP-ERHEAI Filed April 9, 1938 3 Shets-Sheet 2 0 000OOO QOQQOOOOOQOOOOMOOOO r INVENTOR 7711 0091? finger BY Q/% ATTO R N EY June 3, 1941. T. KRUGER I 2,243,909

MEANS FOR CONTROLLING SUPERHEAT Filed April 9, 1938 3 Sheets-Sheet 5 55 'IMINIH 1 w INVENTOR ATTORNEY Hwdurr [17M '0' Patented June 3, 1941 UNETE ATS PATENT OFFICE MEANS FOR CONTROLLING SUPERHEAT Application April 9, 1938, Serial No. 201,073

3 Claims.

The present invention relates to boilers equipped with superheaters and has for its object the provision of improved means for regulating the degree of superheat. More specifically the invention relates to boilers in which so-called tangential firing is employed and in which the superheater receives all or a very substantial part of its heat by convection from gasesafter they have left the furnace, the furnace itself having its walls lined with water-cooled tubes.

The invention will be described with reference to the accompanying drawings in Which it is shown by way of illustration as applied to a Water tube boiler, Fig. 1 showing such boiler in vertical longitudinal section and Figs. 2 and 2a being sectional views on line 2-2 of Fig. 1. Figs. 3, 4 and 5 are detail sectional views illustrating two forms of pulverized fuel burners adapted to be used in the practice of my invention.

The setting I encloses the furnace 3, all of the walls of which are lined with water tubes 99 which are tied into a circulation system with the upper drum 5 and lower drum 1. The particular system of connections for supplying these tubes with water and to take off from them the steam generated together with the unevaporated Water is immaterial and it is therefore believed unnecessary to describe it. The firing is tangential, this term being used herein with the usual well understood meaning which will be more fully stated below in connection with descriptions of Figs. 2 and 2a.

The gases generated in the furnace are directed by baffling ll over the convection boiler surface 13 and superheater Iii and so ultimately to the stack.

The tangential firing spoken of above implies the use of pulverized fuel or liquid or gaseous fuel and the invention is applicable no matter which of these three fuels is used. The fuel is injected into the furnace by means of burners arranged preferably adjacent to each corner as illustrated at It in the horizontal sections in Figs. 2 and 2a and in general in a direction tangent to an imaginary horizontal circle whose center lies in the central vertical axis of the furnace. This circle is in Fig. 2 shown at H. The burning fuel and products of combustion describe a circular or spiral path as they move upward in the furnace roughly tangent to this circle I1.

I have discovered that the degree of superheat can be materially affected by altering the angle at which the fuel and air are injected relatively to the adjacent water-cooled walls while keeping other conditions constant. The amount by which the heat imparted to the superheater can be altered in this manner is sufiicient to answer the degree of regulation ordinarily required with a, correctly proportioned superheater.

In Fig. 2 the direction of injection of fuel is indicated by the arrows l9-- |9 and it will be noted that each arrow isroughly parallel to the adjacent wall or at any rate forms a rather acute angle with it. In Fig. 2a the arrows l9a-I9a indicate the direction at which the fuel and air are injected into the furnace to effect a change in the degree of superheat and. it will b seen.

that these lines l9a form a larger angle witlf the adjacent walls than do the arrows l9--|9 of Fig. 2. The result of this alteration in the direction of injection is that the circle l'ia about which the gases in the furnace now gyrate as they move upward is smaller than the circle I! of Fig. 2. A concomitant result is that the gas currents do not sweep as closely along the walls or, in other words, do not scrub the walls as effectively as they do under the conditions indicated in Fig. 2. While the greatest part of the heat absorbed by the water walls in the furnace is radiant heat, yet a not inconsiderable amount is absorbed by convection. The heat absorbed by radiation under the two conditions shown in Figs. 2 and 2a may be substantially th same but the heat absorbed by convection is reduced in the case of Fig. 2a as compared with that of Fig. 2.

As a result the gases leaving the furnace and entering the superheater l5 are of higher tem-,

perature under conditions such as those of Fig. 2a than they are under conditions such as indicated in Fig. 2. They are therefore able to deliver more heat to the superheater and the degree of superheat attained by the steam while flowing through the superheater will be higher.

I have found that the amount of variation possibie to obtain by these means is suificient for the amount of regulation usually required. With a correctly proportioned superheater it is possible under ordinary conditions to remain within 15 or 20 degrees either Way of a predetermined final su-perheat temperature. This, however, may not be quite satisfactory for turbine opera.- tion or other uses and by means of my invention the additional regulation required is easily obtaihed.

The particular means employed for making the motion about the vertical axis required in the burners possible may be any desired by the designer. The maximum angle through which the burners have to swing is not of any considerable size. Figs. 3 to 5 illustrate two forms of pulverized fuel burners for this purpose.

In the form of Fig. 5, the whole burner housing can be swung about a vertical axis, whereas in the form of Figs. 3 and 4 the housing remains fixed and the change of direction of the fuel jet is accomplished by other means. These means comprise vertical plates 31-41, which are for this purpose pivotally mounted at 39-39. The fuel is delivered, together with the air conveying it, through nozzle 4|, additional air from box 43 being delivered in a stream surrounding the nozzle. This additional air is delivered through duct 40, controlled by dampers 42. The'angle with respect to the adjacent wall, at which this combined fuel and air stream enters the furnace can'be altered by swinging the plates 31-3? about the centers 39-39. The plates'are connected by one or more links 45 so they will move in unison. A shaft 47, rotatably mounted and connected to one of the plates 31 by link as effects the swinging of the plates. As indicated in Fig. 4, there may be a plurality of nozzles mountedvertically one above the other at each corner, in the case shown three such nozzles being used. The'shafts 47 are worked in unison by means of the rod 48 and links 50.

Preferably the burners at all four corners are adjusted simultaneously by suitable linkage, not shown, connecting therods 48.

In Fig. 5 the entire housing 3| can be swung about vertical axis 25. 'The two plates 2121 of the casing have, for this purpose, cylindrical outer surfaces whose axis is at 25, and engage complementary cylindrical surfaces of fixed plates 2929 of the furnace setting. Fuel is delivered by fuel delivery pipe 33, and air, in addition to that bringing in the fuel, by damper controlled duct 35. The fuel and air lines must of course be connected flexibly to their supplies to permit the swinging of the burner housing about the axis 25.

" 'I realize that when the gases are delivered to the superheater at a somewhat higher temperature they may likewise leave that structure at a higher temperature than under other conditions. The difierence, however, is not very large and inasmuch as the final temperature of the gases before discharge to the stack is ordinarily reduced by the use of economizers or air preheaters or analogous heat absorbing structures to about a constant point, the variation at the point Where they leave the superheater is of no significance.

It is understood that the particular form of the invention shown and described herein is merely illustrative and should not be taken as limiting the invention in any way. Variations in the manner of practicing the invention from that "above described will readily occur in practice without sacrificing its essence.

What I claim is:

1. The method of regulating the temperature to which steam is superheated in a superheater receiving its heat mainly by convection from a furnace whose walls are lined with water cooled tubes comprising; introducing fuel and air into the furnace from a multiplicity of points in directions substantially tangential to an imaginary circle in'the furnace for creating a turbulent rotating' gas mass in the furnace transmitting heat to the water tubes therein; maintaining; for a given load, a substantially uniform rate of fuel firing at each point of admission; and. altering the angle relatively to the furnace walls at which the fuel and air are injected to thereby alter the extent to which gases are cooled before reaching the superheater.

2. The method according to claim 1 the fuel and air being injected roughly parallel to the walls when it is desired to lower the degree of superheat and at an angle away from the walls when it is desired to raise the degree of superheat.

3. The method according to claim 1, the fuel and air being injected tangentially to a larger imaginary circle when it is desired to lower the superheat and to a smaller imaginary circle when it is desired to raise the superheat.

' THEODORE KRUGER.