US1604280A - Steam generating and superheating plant - Google Patents

Description

2 Sheets-Shea?l l Oct.` 26 1926.

J. HAAG STEAM GENERATING AND SUPERHEATING PLANT Filed March 3l, 1924 FIG. 1.

Oct. 26 1926. 1,604,280

.HAAG

STEAM GENERA'IING AND SUPERHEATING PLANT Filed March 3l. 1924 2 SheecS-Shee. 2

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, UNITED STATES A 1,604,280 PATENT Ormes.

JACOBUS HIAAGy F AMSTERDAM, NETHERLANDS.

STEAM GENERATING AND SUPERHEATING PLANT.

Application led March 31, 1924, Serial No. 703,218, and Netherlands April 25, 1923.

It is well-known in'the art that Water in the form of steam can advantageously be used in a closed system for heat transmitting purpo es. For the same purpose other iiuids such s carbonio acid, ammonia and sulphurdioxide are often used, especially in refrigerating machinery.

- A power plant has been proposed in which a heavy hydrocarbon oil was vaporized, the

said vapour being used to drive an engine of any type, the latent heat of the exhaust va' pours therefrom being utilized to generate steam available for use in another engine.

A steam supply system has also been proposed comprising a steam generator and a steam accumulator containing water or other liquid, steam generated at substantially constant pressure from the :generator being supplied to the accumulator directly or indi rectly for instance in the same manner as in asurface condenser, said steam giving up its latent heat to the liquid contained in the accumulator, which thereby became superheat ed and gave up steam for use when, due to increased consumption of steam from ,the

xbciler, a decrease of pressure inthe accumulator took place. v

The present inventionconsists in a plant comprising a steam generator and a steam superheater, characterized by an evaporator in which a heat transmitting fluid is adapted to be heated by combustion gases, said evaporator being so arranged that the fluid vapours flow directly from the' evaporator in contact with the superheater and with the steam generator and that the condensate returns to the evaporator, the vapourpressure being kept substantially at atmospheric pressure.

40 Other features of the inventionare hereinaften fully described and claimed in the l ap ended claims.`

t goes without-saying that both the steam f v generator and the steam superheater may be composed of a plurality of units without departing from' the spirit and the scope of my invention.

The advantages of my novel plant are,

inter alia, thatcno excessive heating of Vparts having to stand a high pressure canjoccur and that the degree of superheating, or the maximum temperatureor pressurein any lpart of the installation can be predetermined without there beig any danger of these limits being excee ed such'as with steam generators which are directlyheated by combustion gases.

heater, and a' vapour collector.

The surface which yis d1- rectly subjected to the heat of the fire or the vcombustion gases has to stand a pressure,

for instance atmospheric pressure, which is f independent of the pressure of the generated steam. vThis is a decided advantage, espe-v cially when steam of exceptionally high pressure is to be produced.

By way of example only lI would state 66 that suitablev fluids for transmitting heat to the steam. generator and the steam superheater are aliphatic hydrocarbons of the paraiiine series.

The drawing illustrates two embodiments N of my invention.

vFigure 1 is a vertical sectional view of a plant comprising side byy side an 4evaporator enclosing a steam superheater, a steam generator, a buier drum associated with the 'Il steam generator and concurrently actingas a water level governor and as a feed water Figure 2 is a vertical sectional view of a I cylindrical steam superheater witli evapo- I0 rator gnclosing a steam generator, .and a vapour collector.

Field-tubes 4' secured in and to the bottom of asuperheater drum 6 extend downwardly into a' tlue 3, said bottom being conveniently i rectangular. Inside the drum 6 is a superheater coil or serpentine 8 provided with a saturated steam inlet ipe 7 and a superheated steam outlet plpe 9. In operation the Field-tubes 4 and the lowerportion of 00 the drum 6 are filled with a suitable boiling liquid 5 (for instance a hydrocarbon with a boiling point of say 400 0.), the vapour of which fills the remainder of the drum and v, other parts to be described presently. The

vapour transmits part of its heat to the coil or serpentine 8 so as to partly condense and the remainder of the vapour flows mto a second drum 10 enclosing a steam generator 11, which absorbs the rest of the latent heat 19g -forsuperheating andgenerating the steam is consequently reached without the fluid pressure being appreciably raised above atmospheric pressure. vention is to prevent any steam containing part of the plant from being subjected to a dangerously high temperature. In order to also avoid inconvenient pressures in the fluid, the vapour space communicates with the atmosphere. For this purpose the vapour space of Idrum 10 Acommunicates through a pipe 13 a vapour collector 14 opening into the atmosphere through' an aperture 15. Said collector may be provided with a nest of cooling tubes 16, one of which only is illustrated in Figure 2. Any condensate that may be formed in collector 14 may be returned through a pipe 17 into the drum 10, it being understood that the op valve in said pipe is normally closed Should the systemjly 6 and 10 which contains the heat transmitting fluid, be closed, it is evident that owing to thedirect heating thereof by the combustion gases dangerous pressures might occur in such system. This danger can be avoided by simply putting the system (i. e. the vapor space thereof) into open communication with the atmosphere. Since the heat transmitting medium has a high boiling point (about 400 0.), its vapor will have the same high temperature `although its pressure will be only equal to and -cannot exceed that of the atmosphere. This high temperature, which tis .necessary inL ordery that a sufficient heat trans- -fer can vtake place from the vapor to the steam in the superheater and to the water in the steam generator, cannot be exceeded. The l'luid vapour flowing into drum 10 condenses on the water'tubes of steam generator 11. After said Water tubes have absorbed the heat of evaporation of the condensing vapour, they also take up part of the calories of the condensate itself. Normally the steam generator should be so dimensioned as A oilers directly heated by combustion gases.

The specific evaporation is substantially constant throughout the heating surface in contact with the vapour seeing that the -vapour is not cooled down on its way along the water tubes, such as is the vcase with combustion gases. By specific evaporation meant the evaporation per unit of heat- 111g surface. It will be readily understoodthat .this specific evaporationl must be substantially constant throughout the heating surface in contact with thev vapor of the heat transmitting fluid because the temperature 1n the vapor space is substantially constant and is equal to the temperature of the liquid One object of the in-- 5 in drum 6. Vapor of a lower temperature cannot exist inthe system but condenses on the tubes of the superheater and of the steam generator and such condensate flows down and is again heated in the drum 6.

In an ordinary boiler, wherein the water is heated by combustion gases, the gases are free to cool down on their way to the stack, without condensing. Where the gases are relatively hot the specific evaporation is, of course, greater than where the gases are comparatively cool.

The amount of heat transmitted by condensing vapour through a metal wall to a boiling liquid is many times the amount transmitted by a gas of equal temperature, so that when allowance is made for the smaller difference between the temperatures at both sides of the wall the heating surface in my novel plant needs only be say one tenth of the heating surface of an ordinary directly heated boiler for the same .steam production. This is of special importance for the design of boilers relied upon to generate great quantities of steam of exceptionally high pressure.

Owing to the fact that the vapour will quickly condense upon the outer walls of the water tubes there will be a distinct plane of demarcation between the vapour in the upper portion and the air in the lower portion of drum 10, this plane being lowered (and the evaporation in the boiler being consequently raised) when the amount of vapourowing to increased heating of the Field-tubes 4 or decreased heat transmission to thesuperheater 8 is increased, and vice versa. The 'air in drum 10 follows these movements of the plane of demarcation because of its communication with the atmosphere as at 15.

Owino' to the actthat the system, in which the heat transmitting medium circulates, is open to the atmosphere, and assuming the liquid 5 to be kept at its boiling point, say 400 C., it is clear that the vapor in said systemmust also have a temperature of 400 C., for as soon as the vapor cools down, it condenses and its space is occupied by air or nitrogen. It depends entirely upon the amount of heatsu plied by the combustion gases and upon tlie amount of heat absorbed by the superheater and by the steam generator, whether a small or a large part o'f the vapor space of system 4, 6 and 10 is filled Wlth vapor. If but a small amount of heat be supplied and much heatl is absorbed, ity may be that the vapor will condense almost immediately after it has been formed by evaporation. In the reversecase, it may be that almost thewhole system is filled with vapor.

That ortion ofthe system, which is not occupiedp by vapor, is filled with air entering through 15. A

Now suppose drum 6 to be filled with vapor and drumlO to be filled with air. If the temperature of the superheated steam flowing through the superheater rises, the vapor in drum 6 loses less heat by heat transference to said steam. Consequently, the condensation in drum 6 decreases and as the amount of heat supplied by the combustion gases remains constant, the amount of vapor is increased and vapor enters into the upper portion of drum 10, where it begins to heat the steam generator 11, an equivalent amount of air being expelled from drum 10 through the outlet 15.

'1t may be remarked here that by heating surface of the steam generator is meant that portion of the 'surface of the generator, which is in contactwith the vapor which is at a temperature of 400 C. The remaining portion of the surface of the boiler is in contact with airof comparatively low temperature, but even if the temperature of this air should considerably exceed that of the boiler water the heat transfer would be so small as to be negligible.

As long as the temperature of the steam flowing through the superheater remains above normal, anexcess of vapor is formed in drum 6, i. e. the level of the air inthe lower portion of drum 10 is lowered and the heating surface7 of the steam generator is increased. Owing to this increased heating surface a greater amount of saturated' steam is raised in the generator, whereby the temperature of the superheated steam is lowered, more heat is extracted from the. vapor in drum 6, the condensation in drum 6 1s increased and the level of tlmA air in drum 10 rises again. Thus, thestempera-v ture of the su` erheated steam is automaticallycontrolle It should be noted that the superheater 8 can be used for superheating the steam raised in ordinary boilers and that -i1 this case the saturated steam of generator 11 serves only to cool down the superheated steam as required.

From the above it follows that the superheating temperature is constant. This is another important feature of the invention because it renders the plant perfectly safe and safeguards the engines driven by the vsuperheated steam against damage.

If the vapour of the heat transmitting fluid should be specifically heavier than air at the normal operating temeperatures, the vapour from the evaporator 6 may be introduced near the bottom instead of near the top of drum 10.

In order that the chemical composition of the eirclating hydrocarbon may remain unaltered the air 1n the plant maybe substituted by a more inert gas. yThe inert gas may be kept in the vessel 14 at a substantially constant pressure by leaving open: a

communication with the free air and in order to. reduce diffusion to the minimum the said communicationmay have the form of a labyrinth. l

' A small quantity of nitrogen and carbon-dioxide drawn from the waste gases of combustion and led into the4 collector 14 will y relatively pure state in the upper portion of collector 14.

When the evaporator 6 must be inspected or repaired moderate heating of the fluid 5 suffices to convey said fluid to the collector 14 which, in this case, acts as anv air conkdenser for the vapour. To this effect vthe steam generator isl first blown off so that the vapor cannot condense on its water tubes.

If desired additional steam may be introduced into the superheater from some sourcev other than the boiler 11 through the pipe 2, Figure 2.

If it is required for the whole steam production to be generated through' the medium of the heat transmitting fluid the stem genf erator 11 then supplies the whole 'of the 'steam to the plant. In -accordance `with Figure 1, the steam generator 11 'is provided with a bufferv drum 18 which also acts as a i water level governor. The steam from the generator passes through a nozzle 19 into 'the buffer drum 1 8 and rises through the water therein into a dome 20 whence itv flows through pipe 7 to the steam superheater 8. The lower edge of the nozzle 19 determines the water level inthe steam generator.

- In order that the steam from the nozzle .can fiow through the Water against the water pressure in the reservoir it must overcome the pressure of the steam and of the column of water in the reservoir above the'mouth of the nozzle. The pressure i11^tlie steam space of the boiler must, therefore, be greaterthan the pressure in 'the steam space of the reservoir by an amount equal to the pressure of .said column of water. This diference in'pressure just suffices to'prevent the ,water which flows from the reservoir into the; boiler from rising in the boiler to a higher level than that of the mouth Vof the nozzle. This action isA independent of the height of the column of water. Consequently, as'long as Ithere is water above the mouth of the nozzle, the water level the boiler will be constant. The water reservoir is arranged in such a manner with respect to the boiler that .the mouth ofthe nozzle is on a;

level with the desired water level in the boiler. It will thus be understood that the reservoir acts as an ordinary bottle of Mariotte. n

As it is impossibleor the steam containing parts' of my ovel plant to be excessively heated, said plant is particularly suitable for exceptin'allyhigh steam pressures. Owing to thlff'slf1, antially uniform heating feature of my invention.

Should the Water level in the steam generator fall below a given limit, this is at once manifested by the escape of heat transmitting fluid through the opening of collector 14. But even absence of any water 1n the steam generator cannot give rise to explosion, irrespective of whether or not the )(r generator is connected with other boilers and consequently has to withstand the full steam pressure, and neither can the generator joints then become untight as no worse conditions then prevail in the generator than in the superheater.

Seeing that no appreciable overpressure can occur in the evaporator 6 ythis element cannot explode if it should be excessively heated in the absence of heat transmitting fluid therein.

What I claim is 1. A steam generating and superheating plant, comprising, two individual communieating casings, regulating means for causin the casings to have their interiors subjecteld` to substantially no superatmospheric pressure, a steam superheater in one casing, a steam generator in the other casing, an evaporating member, .means for conducting a heat transmitting vapor from the evaporating member, into, and serially through, the casings and successively past first the superheater, and then the generator and means for returning vapor condensate to the evaporating member.

2. A steam generating and superheating plant, comprising, two individual communieating casings, regulating means for causinr the casings to have their interiors subjecte to substantially no superatmospheric pressure, a steam superheater in one casing, a steam generator in the other casing, an evaporating member, means for conducting a heat transmitting vapor from the evaporating member, into, and serially through, the casings and successively past first the superheater, and then the generator and means for returning vapor condensate to the evaporating member, the regulating means including, a vapor collector open to atmosphere, and a connection placing the vapor collector in communication with the casings at a point beyond the steam generator.

In testimony whereof I alix my signature.

J ACOBUS HAAG.

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