DE3122674A1 - Steam power plant with complete waste heat recirculation - Google Patents

Abstract

A so-called "gas-steam cycle" is proposed which can be operated between the superheated and saturated states of a superheated or cold steam and thus avoids the heating and vaporisation of the feed liquid via the boiler or vaporiser. The compression and hence recirculation of the working medium including the waste heat can thus be carried out virtually without problems by means of a turbocompressor, spiral compressor or piston compressor (Figs. 1 and 2). Complete utilization of the primary heat fed to the cycle is possible here because, upon expansion, the working process makes a transition from the gas phase to the vapour phase (1->2, Fig. 4) and, during the subsequent compression (2->3, Fig. 3), the wet steam can be compressed isothermally and then adiabatically (isentropically) and the heat of compression in the range of the isotherm ( chi = 1) can be absorbed by the working medium itself in the form of heat of vaporisation, i.e. does not have to be carried away to the environment. It is hence possible to state the following "new finding": heat can be converted completely into mechanical work. It is irrelevant here whether the temperature of the heat energy to be converted is above, at or below the ambient temperature level. This gives an intrinsically continuous (perpetual) circulation of the energy in the two states: Heat -> mechanical work -> heat With multiple resuperheating, a high heat transformation in the superheating region and hence a high performance per expansion stroke are achieved even at relatively low operating temperatures (practical application in particular in cold-steam power plants). <IMAGE>

Description

Steam power plant with complete waste heat recovery

The invention relates to a steam power plant with complete waste heat recirculation in hot and cold steam power plants, especially in thermal power plants (fossil and Nuclear power plants).

In the case of steam power plants with complete waste recovery, it is it is necessary that the working material carried out in the cycle process during the relaxation (expansion) runs through a steeper pressure-volume curve (adiabatic) than during compression (Compression) without waste heat during compression (compression waste heat) must be discharged. This is only possible if the substance used is in accordance with Expiry of the expansion respectively. at the beginning of the compression a physical one that has been modified in this way Property shows in which the increasing pressure-volume curve (adiabatic) is clear is traversed flatter than the curve previously falling during the expansion.

For the isentropic change of state in the overheating and saturation area of a vapor or gas, the purely empirical relationship P applies in general. v = constant, (Poissong's law) where the exponent is the deviation from the isothermal change of state indicates.

In the saturation area isentropic compression is close to the upper limit curve (dew line in the T, s diagram) between 1 and 25 bar for water vapor X = 1.135 and with isentropic expansion in the overheating area X = 1.3) R. C. M. Heck Mech. Engng. Vol. 52 (1930) p. 133.See also R. Plank, Thermodynamic Basics, Berlin / Göttingen / Heidelberg 1953, p. 141, Fig.64a.

This different behavior in the event of an adiabatic change of state when running through the pressure-volume characteristics in the saturation and overheating area enables mechanical work to be obtained from heat in a cycle without that heat has to be dissipated to the environment. That way, it's basically possible the primary heat supplied to the cycle completely (100%!) in mechanical To convert work and thus primary energy, e.g. B. from fossil and nuclear ares Saving fuels on a large scale (up to about 70%).

Since refrigerants (= low-boiling liquids) in the overheated and saturated state show similar deviations in their pressure-volume curve like that of water vapor, it is basically possible to use low-temperature Primary heat, e.g. B.; Water, air and ground heat, by means of cold steam engines to use and thus an inexhaustible regenerative energy source with relative to tap high energy density.

The smaller exponent X for saturated steam is due to the much greater heat absorption capacity (heat of vaporization!) compared to that of superheated steam. As the temperature of saturated steam when compressing consequently rises less sharply at the same pressure, results for the to be returned saturated steam a correspondingly smaller volume (z 23 ° ffi) and thus also a correspondingly smaller amount of work compared to the previous expansion obtained from the superheated steam (at a higher temperature and larger volume) Job.

This results in a positive differential work from both work processes the overheating heat supplied to the cycle from outside (= primary heat) is equivalent.

To as much mechanical work as possible as a result of this difference To be able to gain behavior from the heat of the working material, it is necessary to that the differences between the exponents are as large as possible. The size of the exponent in the overheating area can not be significantly.

change, but the one in the saturation area. The deeper you get into the saturation area expands, the more condensate precipitates and the smaller the exponent and becomes thus the greater the gain in work. The gain in labor is greatest when the Vapor is completely condensed, so it is returned in the form of liquid. In in this case X is between 1.135 and zero: 1.135 Do X> O There now in the present mode of operation with superheated steam, the work output in is essentially denied from the overheating, is the desired liquid The state is easy to achieve because the heat of condensation to be extracted is in this Trap is relatively small. Thus it is z. B. also with a heat pump at relative With little effort, the saturated exhaust steam can be completely converted into the liquid State of boar feed, with the heat of condensation on the condensate at the same temperature can be delivered at higher pressure (after the feed pump) 0 So that's it also possible in this way, one operated primarily with superheated steam Thermal power plant with this "environment-independent cooling system" at relatively to operate with little effort and thus primary energy on a large scale to save.

Five exemplary embodiments of the invention are shown in the drawings and are described in more detail below. Fig. 1 shows the basic circuit diagram the steam power plant with superheater when using flow machines (steam turbine and turbo compressor) with status information of a possible operating status and use of water vapor as a working substance (hot steam power plant) Fig. 2 the same as Fig. 1, however, use of a piston machine with status information of a possible operating status with cold steam (R 14 = CF4) as the working medium (cold steam engine) Fig. 3 the (idealized) pressure-volume diagram (P, v diagram) for fig. 1 and 2 fig. 4 the (idealized) temperature-entropy diagram (T, s diagram) for Figs. 1 and 2 Fig. 5 an embodiment with additional condensate separation and separate Return of condensate and dry steam Fig. 6 a condensate separator (to Fig. 5) in the form of a pipe bend with centrifugal separation effect Fig. 7 the (idealized) pressure-volume diagram (P, v diagram) for Fig.

Fig. 8 a further embodiment for the return of waste heat by means of a separate heat pump Fig 9 desglç as Fig. 8, but with an in the cycle process directly integrated heat pump Fig. 10 Vapor pressure curves of some Refrigerants (halogen hydrocarbons for use as working materials in operation as a refrigeration machine (especially for the versions according to Fig. 1 and 2) and Supply with low-temperature heat, especially ambient heat (air, water or ground heat) The basic design of the thermal power plant for hot or cold steam operation, according to the circuit diagram Fig. 1 and 2, consists of the following Components: a steam generator (boiler) b superheater .t turbine (expansion machine ) at Fig. 1 k compressor t / k piston machine (Fig. 2) with inlet and outlet valve EV, AQ r Check valve For starting up the thermal power plant (Fig. 1 and 2) is initially more saturated in the steam generator a by the addition of heat of evaporation qr Steam from state 3 is generated and then via the valve v the superheater b so much Steam supplied that with further heating in the superheater b with superheating heat qü the operating pressure P remains constant. This is achieved by the inflowing Steam is heated to state 1 with increasing volume increase in the run " and the steam extraction - if started beforehand - via the expansion and Compression machine t and k respectively. t / k (in Fig. 2) is maintained.

The status values (temperature and pressure) of a possible operating status sinc in Fig. 1 for water vapor and in Fig. 2 for the refrigerant R 14 (CF4, boiling point: -1280C at 1.013 bar). Both versions can be operated both with superheated steam and with cold steam, in each case the optimal working temperature of the working material used depending on the available one Temperature level of the primary heat source (source of work) is to be adjusted.

In Fig. 3 is the (not to scale and idealized) P, v diagram for the thermal power plant of the embodiments shown in Fig. 1 and 2.

The exponents AC given in Fig. 3 apply to overheated and saturated water vapor in the pressure range of 1-25 bar. The adiabats 1- * 2 with X = 1.3 applies to the expansion in the overheating area and the adiabats 2 -3 with SC = 1,135 applies to the compression in the saturation region. With the specified exponents one obtains for v3 a volume reduced by about 23% 1) compared to V1 for the same Pressure P1 = P3 The temperature profile can be seen from the T, s diagram in Fig. 4.

The useful heat qü in the area 1-2'-3-1 (Fig. 4) corresponds to the useful work W1,2 - W2 3 = Weff in the area 1-2-3-1 (Fig. 3).

The useful gradient that can be achieved with the cold steam power plant (Fig. 2) = = 650C, Sp = 7 bar can be obtained from the vapor pressure curve (Fig. 10) for the refrigerant R 14 (CF4) can be taken. The overheating temperature of the working substance was for reasons of the use of water heat including its latent heat on the door = -200C reduced, i.e. adapted to the temperature level of the work source.

The exponent is used to obtain mechanical work from the circular process X must be larger for expansion than is possible for compression (1o2> X 2 + 3) show that a plant alone in the overheating area or alone in the saturation area is not possible because in each of these two operating cases both P, v curves are congruent and thus no differential work occurs.

In order to enable optimal operation, there is no need for adaptation of the working substance to the given work source temperature - especially towards it Make sure that there are no vapors or gases other than the actual in the circuit Working material are included, such as air pockets. These would be the performance of the thermal power plant. All parts of the system, except the heat-absorbing one Evaporator 1 / x 1) Calculated using the equation: v2 / v1 = (pl / p2) At P1 / P2 = 10/1 is v2 = 0.773 v1 and superheaters as well as their supply and discharge lines, must against internal heat emission (with the superheated steam power plant) respectively. against external Heat absorption (in the case of the cold steam power plant) must be well insulated.

Since in isentropic expansion the superheated steam is below normal Conditions very quickly gets wet (because of the relatively low heat content and therefore rapid cooling) and the formation of liquid droplets for the blades the fluid flow machines (here for the turbo compressor) have a detrimental effect (high wear I) it is advisable to remove the condensate after it has escaped to be removed from the steam turbine via a condensate separator from the wet steam flow and the condensate obtained and the saturated steam separated from each other in the Pump back the evaporator and superheater X Fig. 5 shows such a design.

As can be seen from Fig. 5, between the turbine t is the compressor k and the feed pump s connected to a condensate separator r, which separates the carries out both states of the working substance (mist droplets and saturated steam). The condensate separator used for this is a so-called centrifugal separator (Fig, 6). In its simplest form it consists of a pipe elbow with a relatively narrow and in the area of the pipe bend with a wedge-shaped recess Outflow pipe, as can be seen from the sectional drawing "to Fig. 6" in Fig. 7 the (idealized) P, v diagram associated with Fig. 5 is shown. Because of that separately returned condensate from 2-3 to 3, the pressure-volume area and thus the usable working area is somewhat larger than that in Fig. 3, in which this separate return of the working substance has not been made. From 1 kg of emerging from the turbine Wet steam (1 dD.) Kg of steam are deposited as a liquid and transferred to the boiler a pumped back. The rest of the wet steam of (1 - 6 F.) kg is in the form of saturated Steam is pumped back into the superheater b. As can be seen from Fig. 7, the effective useful work results as Weff = W1 2 + (W3,4 + W3 ', 41). Herein mean: W1 2 = turbine work, W3 4 = compressor work, W3, = feed pump work.

As can be seen from the P, v diagram (Fig. 7), the usable working area becomes the greater, the closer the state 3 moves to 3, d. H. the more condensate at the expense of saturated steam is obtained. The maximum of the pressure-volume-area - and with it the maximum of the useful work - is thus only with complete condensation of the exhaust steam (Wet steam) and you get the usual for steam engines P, v diagram with the largest possible work in the area 1-2-3X-4-1.

Since the proposed thermal power plant predominantly with overheated Steam works and consequently only relatively after expansion via the steam turbine little heat of condensation has to be dissipated until condensation is complete occurs, and only a relatively small temperature gradient has to be overcome, is it z. B. by means of a heat pump with relatively little work and relatively small exchanger surfaces possible to bring about the necessary condensation and to transport the heat of condensation into the liquid circuit.

In Fig. 8 such a thermal power plant is shown, which with a separately working heat pump the condensation heat from the condensation vessel and in the same temperature high pressure liquid circuit (after the feed pump) transported and thus brings about the condensation of the residual steam. It goes the work Wk also with the heat of condensation qO on the high pressure liquid circuit over, the temperature of the liquid increasing accordingly.

The effective useful work results here from Weff = Wt - (Wk + W5), as can be seen in Fig. 8. Here too, as with the previous explanations According to Fig. 1, 2 and 5, - the heat transferred to the cycle is theoretically complete Converted into mechanical work: Weff + 9r '. Herein-mean: Weff = that of the Thermal power plant mechanical work dissipated to the outside, qü = overheating heat, qf = heat of liquid, qr = heat of evaporation (Fig. 8) of a "thermal power plant with a cooling system integrated into the cycle" regardless of the environment (temperature and pressure) and therefore with a single upper Warming container "operable.

In Fig. 9 another thermal power plant is shown that also predominantly superheated steam is used as a source of work. Here is the expansion machine divided into individual stages t1 - t4, which is the rule anyway with steam turbines. The condensate that accumulates between the individual stages is passed through the centrifugal separator r1 - r3 separated and via feed pumps s1 - s3 in a common collecting line pumped and fed to the boiler a. Due to the interim separation that is present in each case at r1 - r3 the turbine blades remain from the harmful influence, which on impact the excreted fine droplets of liquid can be spared. the Condensation of the remaining steam at the end is here with one in the cycle directly integrated heat pump done, d. H. with the same substance which also flows through the turbines. About the workload for the compressor k to keep the heat pump small from the outset is between the outputs of the Turbines t3 and t4 a heat exchanger c / c 'installed, with which in the maximum case the Half of the steam emerging at t3 condenses and can be discharged via r3. The residual steam emerging from t4 is replaced by the heat of condensation removed at the heat exchanger c heated at the heat sensor c 'in the teDurchlaufl' at constant pressure p (e.g. at Fig. 9 to maximum t = 2000C) and the compressor k for further compression and Heating supplied. The remainder of the condensation takes place in the condenser, respectively. Heat exchanger w, whereby the heat of condensation is due to the lower temperature condensate (the one on Separator r3 occurs and is pumped into the collecting line via the feed pump s3) is transmitted. The remaining condensate at the condenser w is discharged via the feed pump s4 is also pumped into the common manifold and the evaporator a at relative high temperature fed together.

In this embodiment (Fig. 9), as with the previous ones Versions according to Fig. 1, 2, 5 and 8, the total heat transferred to the cycle (qü- + + qf + qr) theoretically completely converted into mechanical work. ~ With that this thermal power plant is also independent of the environment and therefore with a single one 'Upper heating tank' operable.

Since in the case of the thermal power plants described here in the ideal case (that is, without heat losses in the cycle) all supplied to the cycle from the outside Primary heat is converted into technical (mechanical) work (by Supply of pure exergy and return of the ~ anergy) is the thermal efficiency each of these thermal power plants (Fig. 1,2,5,8,9) always 100%: qth plant = Wab / Qzu = 1 and thus on the level of the temperature gradient present on the expansion machine independent. The height of the temperature gradient used on the expansion machine only affects the amount of heat converted per unit of time and thus on the performance of the entire thermal power plant. This is of course the thermal efficiency on the expansion machine itself in each case <1 and reaches at best that of CARNOT: #c = 1 - T2 / T1 (T1 = upper, T2 = lower temperature) These relationships can best be overlooked using an energy flow diagram.

The waste of energy previously operated in thermal power plants has its cause is not the incomplete convertibility of the heat in the turbines, but in the release of the heat of condensation to an outside of the cycle located cooling system Blank page

Claims (4)

Claims steam power plant with complete waste heat recovery in hot and cold steam power plants, especially for thermal power plants (Fossel and Nuclear power plants), characterized in that a high or low boiling liquid is passed into the overheated gaseous state (state 1) that the gas is a Expansion machine (steam turbine or piston steam machine) flows in and in this adiabatically expanded to the saturation area (state 2) that the obtained Saturated steam is adiabatically compressed by a compressor up to the operating pressure and the resulting dry saturated steam (state 3) at a lower starting temperature and a smaller output volume is pumped back into the superheater. 2. Steam power plant with complete waste heat recirculation according to claim 1 characterized in that the wet steam flowing out of the expansion machine is preferably passed through a centrifugal condensate separator and the separated Condensate separately via a feed pump to the evaporator and the saturated Residual steam is fed to the superheater via a compressor0 3. Steam power plant with complete waste heat recirculation according to claims 1-2, characterized in that that the wet steam emerging from the expansion machine is fed to a condenser vessel and brought to condensation in this by means of an externally arranged heat pump and the condensation heat in the bypass to the feed pump from the condenser vessel to the the same temperature high pressure liquid circuit is transported 4. Steam power plant -with complete waste heat recirculation according to claims 1-3, characterized in that that a pre-condensate separation on the existing of several steam turbines Steam power plant with one condensate separator each connected between two steam turbines is made and that the condensation of the residual steam by means of a heat loss section (which is effected at the outlets of the last two steam turbines via a heat exchanger is) and a heat pump connected directly to the cycle at the end of the Steam cycle is made.