US1973517A - Radiant and convection superheater - Google Patents

Description

Sept} 1934- I w. H. ARMACOST 1,973,517

RADIANT AND CONVECTION SUPERHEATER Origirial Filed'Sept. 29. 1931 3 SheetS Sheet 2 f 2km ATTORNEY Sept; 11, 1934. w H. ARMACQST 1;973,517

RADIANT AND CONVECTION SUPERHEATER Original Filed Sept. 29, 1931 Sheets-Sheet 3 INVENTOR Wdlbur Hjirmacos BY QZYLMK ATTORNEY Patented Sept. 11, 1934 PATENT OFFICE RADIANT AND CONVECTION SUPERHEATER Wilbur H. Armacost, New York, N. Y., assignor to The superheater Company, New York,

Application September 29, 1931, Serial No. 565,793

Renewed Februaryl'i', 1934 3 Claims. (Cl. 122-479) My invention relates to superheater boilers and aims to provide an arrangement whereby a high constant superheat may be obtained without endangering any of the superheater elements.

It is common practice to build the superheater for a boiler so as to utilize heat from the boiler furnace. Since, however, the fire in the furnace cannot always be regulated in exact proportion to the draft of steam from the boiler, the metal of the superheater elements may sometimes become overheated tosuch an extent as to materially shorten the life of suchelements. Furthermore, a superheater built into a boiler in agiven location does not yield ordinarily a constant temperature at-different loads or rates of steam flow even when the fire is regulated carefully in proportion to thesteam flow. In other words, the ordinary superheater boiler has either a rising-era falling temperature characteristic.

- It is theobject of my invention to provide a novel-arrangement whereby the temperature of steam delivered by a superheater boiler may be maintained substantially constant. over a wide range of load, while at the same time radiant superheater elements used with such boiler may be protected from overheating.

The novel features of my invention are pointed out in the appended claims. The invention itself, howeventogether with its objects and advantages, will best be understood from a detail description, taken in connection withthe accompanying drawings, of several arrangements of superheater andboiler selected by way of example froma number of possible embodiments of the invention. In said drawings,

;Fig. -1 is an elevation, partly in section, of a superheater boiler in accordance with the invention- Fig. 2 is adiagrammatic view illustrating the method of operation of the apparatus shown in Fig. 2.

Figs. 3, 4 and 5 are diagrammatic views illustrating additional superheater arrangements within the invention.

In. the arrangement illustrated in Fig. 1 thereis a boiler 10 having a slag screen bani; 12.and an upper generating bank 14 together with the usual steam drum 16. Between the banks 12 and 14 is a convection type superheater 18. Steam for the superheater 18 is taken off the drum 16 through a pipe 20 whiclr delivers to an inlet header 22. The steam pipe 20 is, moreover, extended beyond the header 22 by branch 21 so as to deliver to an inlet header 24 of a radiant type superheater 26. Steam passes from the header 22 through the alewhich delivers into a branch outlet pipe 30. Similarlythe steam from header 24 passes through elements of superheater 26 into an outlet header- 29 andthence thru a branch conduit 31 to a point 69;; 32 at which branches 30 and 31 unite in a main steam delivery pipe 34 for superheated steam. I It will be seen therefore that superheaters 18 and 26 are connected so that steam from the boiler 10 passes through them in parallel. It is assumed moreover that, in the apparatus of Fig. 1, the steam will divide equally between the two superheaters. ,The parts can readily be designed to accomplish this. Moreover, it is assumed that the- superheaters 18 and 26 are so designed that, to when each is passing one-halfithe steam flow at full load and with normal fire in the furnace 11, the temperature atthe outletof eachof the superheaters lsand 26 will besuch that the temperature at the inlet of pipe 34 will be that desired. As convectiontypesuperheaters suchas 18 have ordinarily arising temperature characteristic with increaseof load and radiant type superheaters suchas 26 have ordinarilyv a falling temperature characteristic with increase of load, the 8,0 temperature at the intake of pipe 34 will remain substantially constant with changes in load. I do not limit myself to such proportions of superheaters 18 and 26. However, the radiant type superheater26oftenreceives almost as much heat at times of low load on boiler 10 as at times of high load so that there may be danger of overheating-the metal in its elements. i r

To'avoid this, difiiculty, ,Ihave illustrated herein a means whereby a greater proportion of the V steam' flow may be caused ordinarily to pass through superheater 26. For this purpose a thermo-couple 36 is placed-in pipe 31 near the outlet of superheater 26 and a thermo couple 38 is placed in pipe 30-near the outlet of superheater 18. The 5 Wires 37 from the thermo-couple 36 and the wires 39.from the thermo-couple 38 are'conducted to a relay contained in box 40 and there employed to operate relay means controlling the circuit of the motor in the casing 42 which is arranged to operate butterfly valve 44 near the inlet of radiant superheater '26 forcontrolling the flow of steam thereto. As the temperature at the thermo-couple 36 increases relative .to that of .thermo-couple 38, valve 44 is operated in a man- 105 er well understood by those skilled in the art to admit a greater proportion of the steam flow to superheater 26. In order to accentuate the action of valve 44 I prefer to place cooperating means in pipe 30 also. In Fig. 1 I have illustrated 1 10 such means in the form of an orifice plate 46 adapted to create a slight drop in pressure of the steam in passing through the orifice so that there is normally some back pressure on the superheater 18 available to force an additional amount of steam through the superheater 26 as the valve 44 is opened more widely.

Fig. 2 is merely a diagrammatic showing or the apparatus shown in Fig. 1 to make the method of operation more plain.

Fig. 8 is a diagrammatic illustration of'an apparatus similar in most respects to that shown in Figs. 1 and 2, but in which a valve 48 is placed in the intake line of the convection type superheater 18 to assist the valve 44 in controlling the relative proportion of steam flowing into the superheaters. In Fig. 3, the orifice plate 46 is dispensed with, its function being carried out by butterfly valve 48. It will be seen that, in'the arrangement shown in Fig. 3, the valve 44 has a lever 50 fixed to its spindle and connected to a lever 52 on the spindle of valve 48' by a rod 54 so'th'at valves 44 and 48 may both be operated by the same motor in the casing 42; It will be seen, moreover, from Fig. 3 that valves 44 and 48 are set to work oppositely, valve 48 being nearly'closed at thetime valve 44 is Wide open.

Inthe arrangement illustrated in Fig. '4, a single fiap valve'5'6-is placed at the junction point 32 and so operated by a motor in the casing 42b as to control the relative flow through the superheaters'18 and 28 by choking more orless the outlet of either the conduitBO or the conduit 31 depending on which way the valve is turned from its central position. The motor in box 42b will beunderstood to be controlled by the relay box 40' which is controlled in turn by the thermocouples 36 and 48, as described above in connection with Fig. 1. In other respects, the arrangement shown in Fig. 4 is so similar to'that of Figs. 2 and 3 that it needs no further description.

1 Fig. 5 illustrates diagrammatically an arrangement in which separate motors contained in cas-- ings 42a and 420 control the valves 44 and 48 in response to the relay mechanism in box 40. The separate-motor in casing 42c is provided in this arrangement in order-that valve 48 may be controlled independently of the 'thermo- couples 36 and 38 when desired, and for this purpose a second relay mechanism is provided in a box 44 which is controlled by a push button 58. It will be understood therefore'that by pushing the button 58 the operator may control the valve 48 to substantially cut off the flow through the convection superheater 18, irrespective of the action of couples 36 and 38. This maybe desirable at times when the boiler is being started up as the fire at this time is often brought up rapidly so that the radiant superheater is exposed to high temperature. On the other hand, the convection type superheated 18 is protected by the generating tubes at such times for the reason that they are cooler than normal until the boiler pressure has been brought up to that of the line. During starting, however, special means may be used to provide a flow of steam through superheater 26 and in such case relay box 41 and pushbutton 58 may be omitted.

In each of Figs. '2, 3, 4 and 5, I have shown one of thethermo couples at" the outlet of the convection superheate'rk' I donot limit myself to this, however, as one of the thermo couples may be omitted. If only one thermo-couple is used it may be in pipe 31. When two are employed, one may be in line 34 adjacent the junction point 32. Furthermore, I do not limit myself to thermo-couples, since other suitable thermostatic means are known which may be substituted for thermo-couples in the arrangement for controlling the proportion of the total steam flow passing through the radiant superheater.

While it is assumed that superheaters 18 and 26 in the arrangements described above have such proportions andare so arranged as to give the same degree of superheat at their outlets at normal full load, I do not limit myself to this. Whether or not the two superheaters are designed to give the" same temperature, the means for increasingthe proportional flow through one superheater or the other comes into play when the temperatures at the outlets of the superheaters change only slightly from those predetermined by the designer to thereby cause a difference be-. tween the temperatures at such outlets or. increasing the difference in temperature beyond that intended.

What I claim is:

1. The combination of 'aboiler, 'a furnace therefor, a radiant and a convection type super'-' heater arranged to utilize heat from said boiler I, p and connected to the boiler so-that the steam 206 flow in one is parallelto that in the other, said superheaters having relative proportions' and positions such that the desiredtotal su'perheat is attained-in the neighborhood of normal full load and when'the steam'flows in them are equalr10 means for diverting a greater or'lesser portionof the total steam flow through one superheater or the other, and means for controlling-said means to increase the proportion or steamflowing through the radiant superheater in response 5 to increase'intemperature of steam at its outlet.

2. The combination of a boiler, afurnace therefor, a radiant and a convection type superheater arranged to utilize heat from said furnace v and so connected to said boiler that the steam; 1 20 flow in one isparallel to that in theother, said superheaters having relative proportions and positions such that the desired total superheat is attained in the neighborhood of normal full load and when the steam flows in them areequal 1-25 and means'for diverting a greater portionof the total steam flow through the radiant superheater when the temperature at the outlet of the radiant superheater is greater than that at the oulet'of the convection superheater.

3. The combination of a boiler, a furnace therefor, a radiant and convection type superheater arranged to utilize heat from said furnace and connected to said boiler so that steam [flow in one is parallel to that in the other, said superl3'5 heaters having relative proportions and positions such that the desired total superheat is attained in the neighborhood of normal full load and when the steam flows in them are equal means for diverting a greater or lesser portionof the steam 140 flow through one superheater or the other, and means for controlling said means to maintain the steam temperatures substantially equalat the outlets of the two superheaters.

- r45 WILBUB} -H. ARMACQST.

Images