US2308762A

US2308762A - Superheater arrangement and support therefor

Info

Publication number: US2308762A
Application number: US322298A
Authority: US
Inventors: Krug Julius; Braun Georg
Original assignee: Combustion Engineering Inc
Current assignee: Combustion Engineering Inc
Priority date: 1939-03-06
Filing date: 1940-03-05
Publication date: 1943-01-19
Anticipated expiration: 1960-01-19

Description

Jan. 19, 1943- J. KRUG ETAL' 2,308,762 SUPERHEATER ARRANGEMENT'AND SUPPORQI' THEREFOR Filed March 5; l940 I 2 Sheefos-Sheet 1 INVENTOR JUL/U6 Aeuq. ,k Games Emu/N.

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Jan. 19, 1943. v J. kRu ETAL S UPERHEATE R ARRANGEMENT AND SUPPORT THEREFOR Filed March 5, .1940 2 Sheets-Sheet 2 INVENTOR JuL/z/a K1906. Gama BEAU/V.

NEY

Patented Jan. 19, 1943 were SUPER-HEATER ARRANGEMENT AND SUPPORT THEREFOR Julius Krug,

Berlin-Wilmersdorf, and Georg Braun, Berlin-Baumschulenweg, Germany, assignors to Combustion Engineering Company,

Inc, New York, N- Y.

Application March 5, 1940, Serial No. 322,298 In Germany March 6, 19.39

3 Claims. (o1. 257- 241 The invention relates to super-heaters for steam boilers and particularly those fired with pulverized fuel and having a furnace lined with water tubes.

In such boilers, especially those of high ratings, the usual convection type of superheater sometimes has insufficient heat absorbing surface to attain high superheat temperatures. Therefore, in some installations a portion of the superheater surface has been installed as a radiant heating surface, i. e., it has been located within the furnace. When this is done, however, complex pipework is required outside of the boiler setting which occupies space and special heat resistant metals are required for the superheater. firing certain kinds of coal in steam boilers, particles of fuel are carried up with the gas stream and deposit upon the heat absorbing surfaces of the boiler. It has now been discovered that within a certain temperature range of the furnace gases, the aforementioned fuel particles deposit particularly upon superheater tubes, while water tubes remain practically free. This may be because the outer surface of a water tube is too cold for an intimate building up of these fuel particles whereas the higher temperature of the superheater tubes is favorable to particle adherence thereon. It/ has also been found that the adhesion of these fuel particles no longer occurs when the fuel particles and likewise the carrying gas stream are cooled below a certain temperature.

According to this invention, more favorable circumstances are attained by locating the superheater, or a substantial part thereof, close to the furnace in the offtake therefor as a radiant superheater and arranged in the form of tube walls parallel to the flow of furnace gases and distributed across the flow of furnace gases in spaced relation at substantial distances apart. The remaining part may be retained as a convection superheater located in a zone where the gas has been cooled to such an extent that the fuel particles do not adhere thereto. In this way the furnace walls may be utilized for steam generating surfaces and this part of the boiler may be limited to the furnace. Even so a substantial portion of the heat will be transmitted to the superheater by radiation since between the superheater tube walls there flow gas layers of one-half meter or more in thickness. Also a substantial part of the heat is transmitted to the superheater tube walls by convection. By this arrangement the spaces between the superheater tube walls offer an opportunity for replacement I When and external cleaning thereof which is of importance when the boiler is being fired with pulverized fuel. The ash deposit on the tube walls when firing with pulverized fuel will be small in amount because the gas flow occurs in thick layers.

structurally, each of the superheater tube walls is made up of several sinuous tube coils interwoven within a single vertical plane and connected in parallel with regard to steam flow. It is desirable to have the tube coils arranged substantially vertically in order to provide for draining the superheater.

It is of particular importance for this type of superheater arrangement and construction to have the superheater tube coils safely supported since the superheater tube walls are located in agas stream of very high temperatures. According to the invention, this is accomplished in a very simple manner, the superheater tubes being carried by adjacent vertical riser tubes which are connected into the circulation system of the boiler. These carrier tubes, being simultaneously utilized as boiler surface, remain cool because of their capacity for heat absorption. They are arranged to embrace the tube walls at right angles to the superheater tubes, so that they prevent a sideward bowing of the superheater tubes. For this purpose the carrier tubes may consist of tube coils suspended from above and having vertical portions embracing the tube walls and bends passing under the tube walls. This type of carrier tube is particularly applicable when the boiler is a forced circulation or oncethrough type in which there is a forced water stream available for the carrier tubes. For boilers of natural circulation, it is recommended to use suspended carrier tubes which enclose the tube wall in pairs and which are bent across in pairs to the opposite sides of the tube walls so that the pair form a support for the tube coils. The carrier tubes may be built up as bifurcated tubes between which the superheater tubes are carried.

In all these means of support the lowermost superheater tube rests upon the bend of the carrier tube and the remaining tubes are supported from the lowest tube by intermediate spacers. In thisway it becomes unnecessary to weld any kind of members, supports, etc., to either the superheater tubes or to the carrier tubes. The supported tube coils are free to expand upwardly and longitudinally. Likewise, the construction provides a simple assembly, since the tubes are readily pushed into the needle eyes, as it were,

of the carrier tubes. 7

These arrangements for supporting tube coils may be used also for the support of boiler coils or economizer coils.

The invention is illustrated in the accompanying drawings in which? Figure l is a diagrammatic view, partly in verv tical section, of the upper part of a steam boiler embodying the invention; Figure 2 is a section on line 2-2 in Fig. 1;

Figure 3 is a' sectional elevation of a modified form of tube support shown on an enlarged scale;

Figure 4 is a fragmentary side view corresponding to Fig. 3;

Figures 5 and 6 are a sectional side view of a further form of the superheater support. The boiler shown in Fig. 1 consists of a furnace I provided with wall tubes 2, a radiant superheater 3, an economizer 4, a convection superheater 5, an econornizer 6 and an air heater 1, all of which are'heated by the furnace gases in V the order named. The generating tubes 2 sup- 'across'thefiow of furnace gases and spaced a substantial'distance apart. Each wall [9 is made up of several sinuous tube coils 20-24 connected in parallel with respect to steam flow and interwovenpr nested in a vertical 'plane as shown in Fig. 1. Generating tubes 26 rise upwardly at right angles to and closely adjacent the superheater tube walls and are arranged in pairs to embrace a superheater tube wall. Tubes 26 receive water from drum I 4 via a header 2'! and discharge into drum II. By such connection a complete water circulation within tubes 26, from and backto drum I 4 occurs in accordance with the amount of heat absorbed by the tubes26 from the flue gases. At intervals the tubes 26 are arranged in bifurcated relationship, being joined to common connectors 26a. At points where thebifurcations arelocated a tube of one coil as 20, rests upon the bifurcation 29, and the remaining tubes, those of thecoils 2l24 are supported on each other by meansof the intermediate spacers 25 which may be loosely inserted. It is advantageousto have thespacers 25 located between the carrier tubes 26 so as to protect them from the hot gases by surrounding them on all sides with heatv absorbing tubes. At their upper ends the carrier tubes 26 are suspended from the boiler framework 3| by means of hangers 30, so that the weight of the superheaters is carried by the frame work. I r 7 What weclaim is:

' l. A superheater comprising tubes'intercona nected by return bends and disposed'inv'ertical rows spaced at intervals'greaterthan twice the tube diameter; and a pair of water'tubeslyingj alongside of and embracing each row of superheater'tubes and having portions thereof -'ofiset to form a rest on which at least. the lowest one of several superheater tubesin each row; are

7 supported.

2. A superheater in accordance with claim' 1,- characterized in that supporting tubes embrace the tube walls in pairs offset at intervals toward opposite sides of the tube wall so that a pair form a support for the tube wall. A

3. A superheater iii accordance ith claim 1, characterizedin that a superheater wall is sup ported by bifurcated tubes with superheater'tubes restingin the crotches of the bifurcations.

JULIUS KRUG. GEORG BRAUN. 7