US1929532A - Adjustable boiler superheater - Google Patents

Description

Filed Feb. 25, 1935 2 Sheets-Sheet l INVENTOR Oct. 10, 1933. w. A. JONES ADJUSTABLE BOILER SUPERHEATER Filed Feb. 23, 1953 2 Sheets-Sheet 2 INVENTOR Mam WW Patented Get. 10, 1933 UNITED STATES PATENT OFFICE Application February 23, 1933. Serial No. 657,957 10 Claims. (01. 122-4514) My invention is adapted to heat a liquid to its boiling temperature, evaporate the liquid into a vapor and then superheat the vapor above the boiling temperature of the liquid for any given pressure, by an amount which can be readily adjusted while the apparatus is in service. The outlet temperature will then be automatically maintained, within limits, for variations of load and furnace conditions.

The invention may be used for generating saturated or superheated steam or for,other vapors such as mercury vapor.

The liquid to be evaporated is forced upward through a tube forming a vertical helical coil in which the liquid is separated by centrifugal force from the vapor as it is generated.

A thermostatic valve maintains a difference in pressure between the inlet and the outlet of the vertical helical coil and thereby the velocity of flow through the coil and thus controls the height of the liquid within the coil and the part of the total length of the tube which is filled with vapor and acts as a superheater to maintain the desired outlet temperature.

The fact that mercury vapor and other vapors have less heat per pound than water vaporof the same density, makes it necessary to circulate many more pounds of such a vapor for a given total energy and this in turn makes it advisable to have a greater flow cross section for a given heating surface.

This greater flow cross section may be conveninetly obtained by using multiple tubular helixes having two or more times as much flow cross section and a shorter path of fiow for a given heating surface and diameter of tube.

Hot gas surrounding the helical coil may flow upward from below or downward from above. When the flow is downward from above, the increasing density of the gases as they are cooled tends to make the flow uniform and the gases to be at the same temperature throughout any horizontal plane.

The downward flow also permits the gases to be cooled to nearly the temperature of the feed and it permits the vapor to be heated to nearly the temperature of the inlet gas which is desirable especially for boilers receiving waste heat gases whose temperature is not high. It is desirable also where a high temperature of outlet vapor is required.

v Upward flow of gases however is sometimes more convenient and in some cases is permissible.

Differences in temperature of metal of boilers with pressure parts of rigid construction has often resulted in temperature strains which finally caused leakage. The use of a helical coil gives great flexibility and avoids strain due to differences in expansion due to differences in temperature.

For ratings below that at which the resistance of vapor flow through a foot of height of the coil is less than the pressure due to a foot of height of the liquid, several coils operating in parallel will tend to distribute the flow equally between them and the rate of flow for them all can be determined by the difference in pressure governed by one thermostatic valve.

Referring to the accompanying drawings;

Fig. 1 is a part vertical section showing single tube helixes.

Fig. 2 is a part vertical section showing double tube helixes.

Figs. 3, 4 and 5 are progressively higher sections through the tube of a helix where progres- 15 sively greater volumes of vapor and higher speeds result in greater and greater centrifugal force for separating the liquid from the vapor.

Fig. 6 is a part plan view partly in section with single tube helixes.

Fig. 7 is a part plan view partly in section with double tube helixes.

Like reference characters indicate like parts in the several views.

In the boiler superheater shown, which I have chosen forpurposes of illustration, feed pipe, 1, supplies liquid to float valve, 2, maintaining level, 3, of liquid in container, 4, having a horizontal part, 5, supplying liquid to headers, 6, from which vertical downcoming tubes, 7 or 7', conduct liquid to the lower ends, 8 or 8', of vertical helixes, 9 or 9'.

Upper ends of helixes, 9 or 9', are connected to headers, 11, which discharge into drum, '12, at one side of thermostatic vapor valve, 13, whose function it is to maintain such a pressure in space, 14, above the pressure in space, 15, as will cause the level, 16, of the liquid in the" helical coil to be sufliciently below the level, 3, to give the required superheat.

The thermostatic valve, 13, is represented as formed of the following parts; I

A plate, 17, with hub, 18, slides on feed pipe, 1.

A spring, 19, is on the pipe, 1, between the hub, 18, and a second hub, 21, which is attached to the pipe. I

A plate, 23, is fastened to the shell of the vapor drum, 12, by bolts, 24.

Circular grooves, 25, and

holes, 26, are formed 11o in plate, 17, and circular grooves, 27, and holes, 28, are formed in plate, 23.

With a space, 29, between the plates, 1'7 and 23, vapor can pass through the valve from space, 14, to space, 15.

Feed pipe, 1, whose temperature is limited to about that of the liquid feed to the boiler does not expand endwise as much as does the drum, 12, with increase of temperature, with the result that as the drum grows longer, with increase of temperature, the plate, 23, moves with respect to the hub, 22, so that at a definite temperature the space, 29, between the plates is increased, thus increasing the valve flow area and limiting the difference in pressure to that which will depress the liquid in the coil just enough to give the required superheating surface to give the required superheat.

Feed pipe, 1, and hubs, 21 and 22, can be moved by differential screw, 31, so that with the boiler cold the hub, 22, will be at a small distance, 32, to the right of the plate, 1'7. Stuffing box, 33, permits pipe, 1, to be moved without leakage.

Set screws, 34, determine the minimum distance between plates, 17 and 23, and prevent the complete closing of the thermostatic valve. Lock nuts, 35, hold these set screws after they are set.

Nozzle, 36, connects to safety valves above the pressure space, 14, of drum, 12.

Nozzle, 37, above space, 15, of the drum, 12, discharges superheater vapor from the boiler.

Drum head, 38, held by bolts, 39, may be removed giving access to the interior of the drum and permitting inner parts of the apparatus to be removed.

U bolts, 41, suspend headers, 11, from beams, 42.

Hot gas may flow from space, 43, downward between the helixes to space, 44, or in the reverse direction.

In Figs. 3, 4, and 5, arrows, 45, 46, and 47, represent force of gravity, arrows, 48, 49 and 51, represent centrifugal forces and arrows, 52, 53, and 54, represent the resultant forces, available for separating the liquid from the vapor within the tube of the helix.

Very moderate velocities result in relatively large centrifugal forces and a very thorough separation of the liquid from the vapor.

Liquids like pure mercury or pure water of course leave no deposit or dust when they are boiled away. Modern practice "in steam plants resu ts in nearly pure feed water and in general most of the impurities which accompany the moisture in the saturated steam which enters the superheater is carried out as dust in the superheated steam, sometimes giving trouble in steam turbines.

A blow off valve, 55, attached to the drum, 12, may be opened when required, reducing the pressure in space, 14, so that water'in helixes, 9 or 9, will partly flash into steam forcing some of the water to rise into the drum, 12, and flow out through the blow ofi valve, 55, washing out the coil and the drum.

As shown the upper part, 56 or 56', of tubes, 9 or 9', are welded to headers, 6, and suspend these headers from headers, 11, above. Evidently headers, 6, can be supported below helical coils permitting the coils to be drained if desired, without other change.

The advantages of this invention include; 'l'he ability to change the temperature of superheat while in service and then automatically maintain it.

Flexibility avoiding temperature stresses.

Combination of economizer, boiler and superheater in one simple apparatus.

Possibility of increasing surface by lengthening coil with relatively small expense.

Adaptability for down flow of gases and counterflow of fluid with coolest gases in contact with coolest fluid tube which is particularly advantageous for boilers receiving waste heat of low temperature.

The small diameters of pressure parts are advantageous for high pressures and for. expensive fluids such as mercury.

Cheapness and lightness and compactness.

Other obvious advantages such as relatively low feed pressure.

The apparatus described may be varied without departing from my invention.

I claim;

1. An adjustable boiler superheater having one or more vertical helical coils of tube surrounded by hot gas and supplied with liquid at the lower end and with the upper end discharging vapor into a space in which the pressure is maintained by a thermostatic valve responsive to the temperature of the vapor discharged in said space, thus depressing the liquid within the coil enough to give sufficient vapor filled surface to give the required outlet temperature of vapor above the boiling temperature.

2. An adjustable boiler superheater having one or more helical coils of tube surrounded by hot gas and with a thermostatic valve at the outlet 110 thereof responsive to the vapor discharged therefrom controlling the relative pressures at the inlet and at the outlet so that only so much liquid is supplied to one end of the coil as will be discharged as vapor of the desired temperature at the other end.

3. An adjustable boiler superheater having one or more vertical helical coils of tube surrounded by hot gas and with the lower end of the coil fed with liquid through a float valve and its upper end discharging vapor into a space in which the pressure is maintained, somewhat above the pressure at the surface of the liquid at the float valve, by an amount determined by the temperature of the vapor compared to the temperature of the feed as described.

4. An adjustable boiler superheater having one or more vertical helical coils of tube surrounded by hot gas and with the lower end of the coil fed with liquid through a float valve above it, and with the upper part of the coil discharging vapor into a space in which the pressure is maintained, by a thermostatic valve responsive to vapor discharge temperature somewhat above the pressure at the surface of the liquid at the float valve, depressing the liquid within the helical coil such a distance as will give a vapor filled part of the coil suflicient to impart the required temperature to the outgoing vapor.

5. An adjustable boiler superheater having one or more vertical helical coils of tube whose lower part is filled with liquid receiving heat from hot gas and whose upper part is filled with vapor being superheated by hot gas and with automatic apparatus responsive to the vapor discharged from said tubes for depressing the liquid enough to give the required outlet temperature of vapor.

6. An adjustable boiler superheater having one or more vertical helical coils of tube whose lower part is filled with upward flowing liquid receiving heat from hot gas and whose upper part is filled with vapor evaporated from that liquid and being superheated by hot gas and with automatic apparatus responsive to the vapor discharged from said tubes for depressing the liquid within the coil, decreasing the liquid cooled surface and increasing the vapor cooled surface enough to give the required outlet temperature of vapor. I a

7. An adjustable boiler superheater having one or more vertical helical coils of tube, surrounded by hot gas, and supplied with liquid at its lower end through a float valve above it, and with the coil discharging vapor into a space in which the pressure is controlled by a thermostatic valve adjusted to pass only vapor of a temperature above that of the boiling liquid at that pressure. 8. In combination, a vertical helical coil of 'tube to the lower end of which liquid is'supof the boiling liquid and maintaining a pressure at the outlet of the coil intermediate between that at the float valve and that at the bottom of the coil.

9. In combination, a vertical helical coil of tube to the lower end of which liquid is supplied, hot gas surrounding the coil and imparting heat to it and a thermostatic valve at the upper end of the coil opening at a temperature above that of the boiling liquid.

10. In combination, a float liquid feed valve, a vertical helical coil of tube receiving liquid from the feed valve, hot gas surrounding the ,coil and a thermostatic valve formed of an outer disc positioned by a shell in contact with the outlet vapor and an inner disc positioned by a pipe in contact with the inlet feed liquid, so that the space, between the two discs, through which the vapor passes is determined by the difference in expansion, due to heat, of the shell and the feed pipe and increases with the temperature of the vapor.

'VWLLIAM ANTHONY JONES.

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