DE949061C - Steam power plant - Google Patents

Description

Steam power plant Dia invention aims to create a steam power plant, which is superior to the previously known in that it meets the requirements for a power machine with the best possible efficiency due to the thermodynamic Requirements met to a greater extent than those currently used or proposed Steam power plants that is the case.

In this context, steam is preferably understood to mean: water vapor., But the system according to the invention can also be used with other vapors, e.g. B. with C 02 or N H3 or S 02 or a freon or any other suitable substance will..

A well-known Idtal process for steam power plants is the Clausius-Rankine process. In it, the preheating of the water under pressure is followed by evaporation in one Boiler at constant temperature, then overheating, then adiabatic Expansion up to the condenser pressure and condenser temperature, then the condensation, whereupon the process repeats itself. This although sometimes referred to as ideal Process can achieve the Carnot efficiency, which is the aim must become, however not achieve. It can only be realized if only warmth supplied at a constant highest temperature and only at a constant lowest temperature is discharged. In the Clausius-Rankine process, however, only heat dissipation takes place lowest temperature, the heat supply, however, predominantly in the steam boiler, i.e. at a much lower temperature than the final temperature of the superheater.

The Rankine process has been improved by has used tap steam to preheat the water. This becomes the opposite in itself Heat dissipation in the condenser that is too great for the work done is somewhat reduced, however the incorrect supply of heat at a temperature that is much too low was not corrected.

With modern. Steam power plants also determine the steam pressure in the boiler elevated. That brings an improvement, because it is also the main heat input takes place at a higher temperature level, but even then this is still Temperature always significantly below the maximum temperature.

A further approximation to the Carnot efficiency brings to a certain extent Also meaning a multi-stage intermediate heating of the steam with the one in between adiabatic expansion. Even with full isothermal expansion achieved - and a very multi-stage reheating is nothing else - except for Condenser pressure and use of a connected heat exchanger between the hot, but relaxed, exhaust steam and the live steam to be heated becomes the Carnot efficiency not yet achieved because the essential heat input is at the temperature of the steam boiler takes place that compared to the maximum temperature. is relatively low. The combination such a system has not yet been shown, but can be found in the References to their individual elements.

Attempts have also been made to switch off the steam boiler, so to speak, that he. with steam pressure and steam temperature goes to supercritical values. Even this measure, even in combination with the aforementioned, does not yet lead to ideal machine, apart from the inconvenience of the extremely high pressure, because the supercritical isobars: point in the TS diagram at the level of the critical Temperature inflections to the horizontal, which means that still a lot Heat can be supplied at this temperature, which is still far too low. got to.

It has therefore also been proposed to use steam cycle processes with gas cycle processes or to combine superheated steam compression cycle processes. The compressor used for this The gas cycle process then creates heat that is used for preheating the water or for evaporation or can be used for overheating. All of these suggestions have so far been possible do not bring the desired success, because the compression heat after the previous Proposals are not produced in the quantity and not at the temperature at which they are is needed, and heat drops from, a temperature level. on the other without full work excludes the Carnot efficiency.

So is z. B. has been proposed to a steam power plant with approximately Carnot efficiency at low temperatures. To be connected directly to the hot gas cycle. However, since this combination is a side-by-side arrangement in the TS diagram instead of a This proposed process remains from the ideal Carnot process quite far away.

It has also been suggested to use dry steam for another Working medium as water vapor partly in the temperature range of the critical To condense the pressure again, namely after an adiabatic. This recompression, too in no way leads to Carn.ot efficiency, since with it the heat by no means in the required temperature level occurs.

It has also been suggested a primary. A steam process overlay secondary with multi-stage expansion. However, since this is the expansion is partly done at low temperature and also preheating and overheating takes place through direct firing, this PrOZeß also remains of the Carnot efficiency very far away.

Evaporation has also been proposed by atomizing nozzles and compressor cooling. Here, too, there are considerable drops in heat suggest that the Carnot efficiency cannot be achieved by far :; aside from that the use of a cold, low pressure turbine causes the need for a substantial adiabatic recompression, and as a result of the inevitable losses the gain, more than outweighed.

The invention, however, has the goal of a pure steam cycle superimpose one or more superheated steam cycle processes with recompression in such a way that that the Carnot efficiency is achieved for the lossless machine. Actually executed machine will of course stay below this, but will come closer to it than all previously known steam power plants.

Of the. primary steam cycle on which the invention is based exists from isothermal condensation with a subsequent pressure increase in the condensate a pump, preheating of the water with subsequent evaporation, overheating, approximate isothermal expansion, and subsequent cooling of the relaxed; but still hot Steam in, a heat exchanger. The approximately isoth, erme expansion can; in this can be achieved e.g. B. by multi-stage reheating in a known manner or by expansion in the presence of a liquid in a known manner or by heating of the turbine blades. or in some other way.

In this primary process, some of the heat is supplied along the isothermal expansion, i.e. at the highest temperature, which is correct, but then for evaporation at a lower temperature and for water preheating at still lower temperature, which is undesirable in itself. The overlying, Cycle processes are now chosen and carried out in such a way that the resulting compression heat deliver the full water heat and the full heat of evaporation, with avoidance of temperature jumps, exactly at the temperature and to the extent required will.

To generate the heat of vaporization is therefore according to the invention part of the steam exactly. at the evaporation temperature and as precisely as possible isothermally compressed, be it through multi-stage compression or through compression when cooling by a liquid or with paddle cooling or according to some other known. Art. The amount of compressed steam is. then. chosen so large that the waste heat of the isothermal compressor the heat of vaporization on the same isotherm exactly covers.

To generate the water preheating, however, according to the invention Another superheated steam cycle is superimposed on the basic process in such a way that compression runs along the right limit curve in the TS diagram. So she's not there either adiabatically still isothermal; but lies podytropically in between, begins steeply and then runs, always flatter. This happens from the knowledge that the right Limit curve in the TS diagram in the relevant temperature range is quite rough is a mirror image of the left limit curve and compression along that curve around it exactly covers the heat demand along the other curve.

These two superheated steam cycles become the basic process, if the machine is assumed to be lossless, is supplemented exactly to the Carnot efficiency. depending on the distance between the evaporation and the critical point, the first or the second superheated steam cycle is important. Will be near or above the critical. Point worked, the process that is supposed to evaporate the water can be omitted .; will worked much below the critical point, so the process for water preheating fall away.

In this way, heat from the outside is only available at a constant highest level Temperature supplied, namely only in, the turbine, and heat to the outside only at constant lowest temperature dissipated, namely only in the condenser. But with that meets the conditions according to which the lossless machine is exactly with the Carnot efficiency have to work. Another advantage here is that you can use relatively little Steam pressures, what can get by with cheaper investment, and simpler operation results.

The schematic drawings serve to explain the invention with Figs. i to B.

Fig. I shows the. Cycle process according to the invention in the TS diagram; Fig. 2 shows a. Circuit diagram for this; Fig. 3 to 8 show the in TS diagrams. Structure of the proposed cycle from its elements. D: e line of the left limit curve (water-liquid) a meets the line of the right limit curve steam-gas) b at the critical point Kr.

From i to 2, the condensation takes place in the condenser 15, from. 2 to 3 the pressure increase by the pump 17. The liquid, e.g. B. water, is heated from 3 to 4 in the heat exchanger 16 and then evaporates, from 4 to 5 in the boiler 16. From 5 to 6 the overheating takes place in the heat exchanger 13. From 6 to 7 the heat supply Q1 takes place in a multi-stage turbine ir or otherwise isothermally at a constant high temperature. From. 7 to 8 the cooling takes place in the heat exchanger 13. This is where the current divides. One part flows via the compressor 12 along the line 8 according to FIG. 5, that is to say isothermally, to the heat exchanger 13 again. The compression heat of the multi-stage or the internally cooled compressor 12, namely Q2, flows to the boiler 14 as Q3. The other part flows again via the heat exchanger 16 to the condenser 15 along the line 8 to i. The partial currents are matched to one another in such a way that Q2 is equal to Q3. It takes place. therefore from the outside the heat supply is only as Q, and the heat dissipation to the outside is only as Q4. The condenser pressure is z. B. 0.024 ata at 20 ° C, the boiler pressure 2o ata at 21i ° C, the temperature at the turbine ii 500 ° C. If there is friction in the turbine ii, the equivalent of heat supply is saved. Although friction in the compressor 12 worsens the process, it is not lost, but is used again as heat to evaporate the water in the boiler. The performance is z. B. abgenämmen on the generator io, which is on the same shaft 9 with the turbine ii and the compressor 12.

To avoid high vacuum, you can use water instead of water Kind of also use another substance. Instead of the turbine, in special cases a piston engine can be chosen.

If you want to work under supercritical conditions, it is advantageous to perform the compression up to the critical point Kr along the right limit curve b and thereby to heat the liquid along the limit curve a, since the heat of the exhaust steam is not sufficient for preheating the water.

In the Clausius-Rankine process according to Fig. 3, the work done is namely the line from, i to 2 to 4 to 5 to 6 to i, significantly smaller than in the Carnot process with the same heat dissipation.

In the basic process of the invention. 4, however, already takes place significant part of the heat input along the line from, 6 to 7, which increases the efficiency considerably increased compared to the Clausius-Rankine process. Be in the heat exchanger the relaxed, but still hot exhaust gases along line 7 to i first the steam and then warm the water in countercurrent .. Because line 7 to i is steeper if ace is from 2 to 4, this waste heat is sufficient to preheat the water not. Because of this, with a small amount of steam, the superimposing process becomes carried out according to Fig. 5, so from point i to 5 to 6 to 7 to i. The compression so will be along the right. Limit curve from i to 5 controlled so that the still, the heat required for preheating the water is made up.

The further superimposition process of FIG. 6 lies between the points 8, 5, 6, 7, B. Here the compression is as largely isothermal as possible from 8 to 5 carried out, with such a large amount of steam that the full heat of vaporization from point 4 to point 5 of FIG. 4 is thus covered. There compressions and evaporation here at the same temperature level and both run isothermally, this is how therefore no loss due to temperature gradients.

Fig. 7 shows the processes in combination., The basic process of Fig. Fig. 4 represents the area Ff, den, one superimposing process of Fig. 5, F2 and the other Overlay process according to FIG. 6 represents the area F3. All three areas together result the area F. Since the content of a rhomboid is now equal to that of a square Base line and the same height, the area F can also, as shown in Fig. 8, being represented. But that is exactly the Carnot process.

The superposition processes according to FIGS. 5 and 6 are thus according to the invention exactly so that it changes the basic process of Fig. 4 to the Carnot process of Fig. 8 add to.

In practice, both superimposition processes will usually be used, However, if you work near the critical point, you only need that Process according to Fig. 5 and with a large distance only the superposition process according to Fig. 6th

. The steam power plant according to the invention thus allows the To get quite close to the Carnot process, without the use of high pressure or High pressure steam. The fact that because of the isotherms has a particularly favorable effect the frictional losses, which are transformed into heat, are only slightly harmful.

Claims (1)

PATENT CLAIMS: i. Steam power plant, in which the primary circuit of a steam part, consisting of isothermal condensation in the condenser, pressure increase of the condensate by a pump, water preheating in a heat exchanger, evaporation at a constant temperature, overheating in a heat exchanger, approximately isothermal expansion at the highest temperature in an engine, cooling in countercurrent with the heat exchangers mentioned., Secondary circuits are superimposed with recompression of the steam, the steam of the primary circuit and that of the secondary circuits having the engine and the heat exchanger upstream of it in common isothermal (8 to 5) at the evaporation temperature (between 4 and 5), on the other hand (r to 5) along the right limit curve (b) up to the evaporation temperature (5) and the steam quantities for the secondary circuits. (Fig. 5 and 6) are chosen so large that the basic process (Fig. 4) is supplemented to the Carnot process (Fig. 7 and 8), and thus no heat from the outside except during the approximately isothermal. Expansion (6 to 7) supplied and no heat is removed to the outside except in the condenser at the lowest temperature (i to z). z. Steam power plant according to claim i, characterized in that for working with vapors under supercritical conditions. the isothermal compression (8 to 5) with the associated cycle (Fig. 6) is omitted. Documents considered: German Patent No. 903 818; Belgian Patent No. 493,624; Glaser's Annalen, April 1954, pp. 90 to 94.