JPH0310561B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention involves the catalytic conversion of SO ₂ to SO ₃ and the absorption of SO ₃ into concentrated sulfuric acid after cooling the SO ₃ -containing gas in multiple stages. sulfuric acid from an SO ₂ -containing gas, which is transferred to a cooling medium, which is guided into a circulation circuit, and from which heat is transferred by indirect heat exchange to heat utilization equipment. Regarding the manufacturing method. The catalytic conversion of sulfur dioxide (SO ₂ ) to sulfur trioxide (SO ₃ ) is actually vanadium pentoxide (V ₂ O ₅ ).
is carried out using a catalyst based on Since this reaction proceeds exothermically, the temperature of these gases increases. Furthermore, SO ₃ produced by concentrated sulfuric acid
The absorption of ions is also accompanied by heat generation, and the released absorbed heat must be dissipated. Utilizing the excess heat generated at this time is important from a thermoeconomic standpoint. However, this heat
It is difficult to use it economically because it occurs partly at very low temperature levels. Moreover, even the dried gas, although in very small quantities,
Since it still contains moisture, it must be ensured that the temperature of the SO ₃ -containing gas before entering the absorption device does not fall below the dew point. This applies not only in the case of intermediate absorption but also in the case of final absorption. It is known that the SO ₃ -containing gas leaving the first contacting stage is cooled in two stages prior to the intermediate absorption treatment, in which the first stage involves a heat exchange with the gas leaving the intermediate absorber. In the second stage, heat exchange with the supplied water takes place (German Patent No. 1186838,
(See specification No. 1567672). Furthermore, German patent no.
Specification No. 2529709 and German Patent Application Publication No.
It is already known from documents 2,529,708 and 2,824,010 that the heat leaving each acid cycle of the absorber is removed by indirect heat exchange with dilute sulfuric or phosphoric acid. This heat exchange can also be carried out by means of a closed circulation circuit of a cooling medium consisting of water, oil or other media. The relatively high temperature of the cooling medium necessitates relatively high costs for heat exchange of the acid. If the SO ₃ -containing gas is cooled in two stages before it enters the absorber, there is a risk that the gas temperature will fall below the dew point if the heat of the gas is not fully utilized for heating the cooling medium. The object of the invention is to increase the temperature of a liquid cooling medium with little outlay in a closed circuit for heat transfer located between the acid of the absorber and the heat utilization equipment. Alternatively, the temperatures may be approximately equal, thereby utilizing excess heat from the contacting system and ensuring that the SO ₃ -containing gas is prevented from dropping below its dew point. In order to solve the above problems, according to the present invention,
First, the SO ₃ -containing gas is cooled by indirect heat exchange before it enters the absorber, and then the SO ₃ -containing gas is cooled by indirect heat exchange with cooling medium A guided in a closed circuit. The sulfuric acid circulation stream of the absorber is cooled to a temperature slightly above the dew point and the heated liquid cooling medium B is cooled by indirect heat exchange with liquid cooling medium B guided in a closed circulation circuit. , the heated cooling medium A is further heated by indirect heat exchange with the heated cooling medium A, and the high temperature cooling medium B is cooled by indirect heat exchange with the heat utilization equipment. The SO ₂ -containing gas used in this case can be dry or humid. SO ₃ absorption always takes place after the last contact shelf. Note that intermediate absorption treatment can also be additionally performed. If this intermediate absorption treatment is carried out, the first contacting stage is usually followed by the intermediate absorption, and the second contacting stage is followed by the final absorption. However, it is also possible to carry out an intermediate absorption once after the first contacting stage and once after the second contacting stage, and then a final absorption after the third contacting stage. This mode of operation can be employed in the case of intermediate absorption, in the case of final absorption, or even if both absorptions are carried out. In the latter case, when the acid temperatures in the intermediate absorber and the final absorber are approximately equal, the liquid cooling medium circulation circuits between the absorber and the heat utilization equipment are each connected separately. If the acid temperature in the final absorber is lower than the acid temperature in the intermediate absorber, the liquid cooling medium B is first passed through the acid heat exchanger of the final absorber and then through the acid heat exchanger of the intermediate absorber. be able to. Furthermore, one partial stream of the heated cooling medium B is further heated by the cooling medium A of the intermediate absorber and another partial stream by the cooling medium A of the final absorber, and then both partial streams are heated. It is also possible to merge them again. In addition, the entire heated cooling medium B is sequentially heated by only one branched cooling medium A, or by both branched cooling medium A,
It is also possible to reheat. The liquid cooling medium B may consist of pressurized water or other liquids, such as oil. Cooling medium A may also consist of a liquid or a gas. As the heat utilization equipment, a process that requires only heat at the same temperature level, or a process that requires a higher temperature level, in which case reheating is performed, can be applied. In the first cooling stage of the SO _3- containing gas before the absorption process,
In the treatment of cold-obtained SO ₂ -containing gases, the SO ₂ -containing gas is heated prior to catalytic conversion. If intermediate absorption is carried out, generally in this cooling step the hot SO ₃ -containing gas leaving the contact reactor is cooled by heat exchange with the cooler gas leaving the intermediate absorber; The cold gas is heated to the operating temperature of the immediate next contacting shelf. For example, high temperatures generated by the combustion of sulfur
When treating SO ₂ -containing gases, the above-mentioned method of operation is generally followed in a first cooling step prior to intermediate absorption. A feed water preheater is generally provided before the final absorber. By adjusting the circulation rate of the cooling medium A in the circulation circuit, maximum heat extraction is controlled without the temperature level of this cooling medium falling below the dew point of the gas. The operation type of the heat exchanger may be a countercurrent type or a cocurrent type. According to a preferred embodiment of the invention, liquid medium B consists of pressurized water. This allows effective heat transfer at low costs. In this case the pressure in the cooling circuit is maintained at such a level that no evaporation occurs due to heating. Furthermore, according to a preferred embodiment of the invention, the cooling medium A consists of pressurized water. This ensures that the pressure in the cooling circuit is such that, upon heating, no evaporation of water occurs, or complete evaporation occurs.
It can be adjusted either way. The heat content of the steam is fully available for heating the cooling medium B. Furthermore, according to a preferred embodiment of the invention, the pressurized water as cooling medium A is completely evaporated by indirect heat exchange and its vapor is condensed by indirect heat exchange with cooling medium B. As a result, the amount of cooling medium A pumped in the circulation circuit is significantly reduced, and the energy required for the pumping operation is correspondingly reduced considerably. Furthermore, according to a preferred embodiment of the invention, the pressurized water as the cooling medium A is completely evaporated by indirect heat exchange, and its vapor is condensed by heat exchange with the second heat utilization device. , this high temperature condensate is used to heat the cooling medium B. This allows part of the heat of cooling medium A to be used at higher temperature levels. Further, according to a preferred embodiment of the present invention, 120
The cooling medium A at a temperature of 180° C. is subjected to an indirect heat exchange with the SO ₃ -containing gas and is guided countercurrently. This ensures a satisfactory heat transfer and prevents the sulfuric acid in the gas stream from condensing before entering the SO ₃ absorber. Furthermore, according to a preferred embodiment of the invention, the final absorption takes place in the cold, whereby the cooling medium B is first heated in the sulfuric acid recirculation stream of the intermediate absorber, and then the cooling medium A and the final absorption are heated in the intermediate absorber. It is further heated by the cooling medium A of the intermediate absorber. By this,
It is possible to easily bring the cooling medium to the maximum temperature before entering the heat exchanger of the heat utilization equipment. Absorption carried out in the cold is an absorption in which the temperature of the acid flowing out from the absorber does not become higher than the temperature of the cooling medium B after heat exchange with the heat utilization equipment. The heating of the cooling medium B by the cooling medium A can be carried out in series, in particular at different temperature levels of the cooling medium A, or the cooling medium B can be divided into sub-streams, These partial streams are conducted in parallel through both heat exchangers and are recombined before the heat utilization equipment. Furthermore, according to a preferred embodiment of the invention, the cooling medium B is first heated by the sulfuric acid recycle stream of the final absorber before being heated by the sulfuric acid recycle stream of the intermediate absorber. This also utilizes the heat generated at relatively low temperature levels in the acid circuit of the final absorber. Furthermore, according to a preferred embodiment of the present invention, the pressure of the heated pressurized water B is adiabatically removed in the heat utilization equipment, and the steam generated at this time is removed in the heat exchanger of the heat utilization equipment. Condensed. In this case, the adiabatic pressure relief is carried out at the point where the heat utilization equipment is located in such a way that the water vapor produced in this case passes through the shortest possible path. This achieves a more effective heat transfer than in contact with pressurized water, which results in a smaller heating area in the heating equipment or in reducing the amount of heat that tends to stick to the heating equipment. With certain media, the operating time of the heat utilization equipment before requiring heating surface cleaning can be longer than with a heating surface of comparable size. Furthermore, according to a preferred embodiment of the invention, the adiabatic pressure relief of the pressurized water is carried out in a plurality of stages connected in series in the water circulation circuit, the water vapor generated in the individual stages being It is condensed separately in separate heat exchangers in the utilization equipment. This allows the energy contained in the pressurized water B to be used in stages and in parts at relatively high temperatures. Furthermore, according to a preferred embodiment of the present invention, each heat exchanger in the heat utilization equipment is connected in series, and the thermal energy absorption medium of the heat utilization equipment is arranged such that the temperature of the thermal energy absorption medium increases. direction, countercurrently with medium B through a heat exchanger. Under such countercurrent flow between the pressurized water B and the medium of the heat utilization equipment, the temperature of the pressurized water after releasing energy to the heat utilization equipment becomes significantly lower than in the case of cocurrent flow. This provides the essential benefit of requiring relatively little pumping of pressurized water B and allowing the solution to be concentrated to a higher concentration when heat utilization equipment is used for evaporative concentration of the solution. . Furthermore, according to a preferred embodiment of the invention, the condensate occurring in the heat exchanger of the heat utilization equipment is collected;
Its purity is checked and the condensate is returned into the pressurized water B circuit only if it is pure. This ensures that in the event of a leak in the heat exchanger of a heat utilization appliance, the amount of contaminated condensate is relatively small and that the contaminated condensate can be drained separately. Large amount of pressurized water B due to leakage
is not endangered and it is ensured that damage in the pressurized water B circulation circuit can be avoided. Furthermore, according to a preferred embodiment of the present invention, a heat exchanger of the heat utilization device is used to heat an evaporator for concentrating an aqueous solution. In this case, as the aqueous solution, a solution containing sulfuric acid or phosphoric acid is particularly problematic. Furthermore, according to a preferred embodiment of the present invention, a steam condenser is connected before the heat exchanger in the heat utilization equipment. This makes it possible to increase the condensation temperature of the steam generated from the pressurized water B in order to reduce the heating area of the heat exchanger or to increase the temperature of the medium on the heat utilization equipment side. Next, the present invention will be explained in detail with reference to drawings and examples. In FIG. 1, SO ₃ -containing gas is conducted via conduit 1 into a first indirect heat exchanger 2 . Cooling medium is supplied via conduit 3 and discharged via conduit 4. The precooled SO ₃ -containing gas is led through a conduit 5 to a second indirect heat exchanger 6 into which the cooling medium A is introduced via a conduit 7 .
It is discharged through conduit 8. The cooling medium A is supplied to the pump 9
guided through the closed circuit. The SO ₃ -containing gas is led into an absorption device 11 via a conduit 10 .
After the SO ₃ it contains has been absorbed, this gas leaves the absorber 11 via conduit 12. Concentrated sulfuric acid is conduit 1
3 into the absorber 11 and discharged through the conduit 14 into the receiving tank 15, and further into the pump 16.
via conduit 17 to indirect acid heat exchanger 18 and from there into conduit 13. Cooling medium B
is led through a conduit 19 to a heat exchanger 18, then through a conduit 20 to an indirect heat exchanger 21 in the circulation circuit of the cooling medium A, and from there through a conduit 22 to an indirect heat exchanger of heat utilization equipment. from there to the conduit 19 by means of a pump 24. In the heat exchanger of the second heat utilization equipment 25, when the pressurized water A evaporates in the heat exchanger 6, the vapor condenses, and then the high temperature condensate is transferred to the heat exchanger 2.
Sent to 1. In FIGS. 2 and 3, the symbols with a prefix relate to intermediate absorbers, and the symbols without a prefix relate to end absorbers. In this case, the pump 24 first sends the cooling medium B through the conduit 19 to the acid heat exchanger 18 of the final absorber and then through the conduit 19a.
and then sent to the acid heat exchanger 18a of the intermediate absorber. In FIG. 2, one partial stream is conducted via conduit 20a to heat exchanger 21a of the intermediate absorber, and the other partial stream is conducted via conduit 20 to heat exchanger 21 of the final absorber. These two partial streams are combined upstream of the heat exchanger 23 via conduits 22, 22a, respectively. In FIG. 3, the cooling medium B is connected to the heat exchanger 18a.
through a conduit 20 to an indirect heat exchanger 21 located in the circulation circuit of the cooling medium A;
2 to the indirect heat exchanger 21a of the intermediate absorber, from there to the heat exchanger 23 of the heat utilization equipment via the conduit 22a, and from there to the conduit 19 again by the pump 24. In FIG. 4, heated pressurized water is introduced into conduit 2
2 to a pressure relief tank 26, where it is adiabatically pressure relieved. Pressurized water exiting pressure relief tank 26 via conduit 33 is pumped to pump 24.
is sent to the heat exchanger 18 via conduit 19.
The water vapor generated by the adiabatic expansion in the pressure relief tank 26 passes through the conduit 27 to the heat utilization equipment 2.
3, but a steam condenser 36 can be provided in the conduit 27 before this. The heat utilization equipment 23 is exhausted from the conduit 35, and supplementary water is supplied from the conduit 42 into the conduit 19 to supplement the amount of water discharged at that time. The steam condensate generated in the heat utilization equipment 23 passes through a conduit 28 to a purity tester 29.
sent to. This purity tester can function as a PH meter or a conductivity meter. The heat absorbing medium 38 flows through the heat exchanger of the heat utilization device 23 . The condensate is transferred from the purity tester 29 via conduit 30, pump 31 and conduit 32 to conduit 3 of the pressurized water circuit, unless it is contaminated by leakage in the heat utilization equipment 23.
It flows into 3. Alternatively, in the event of leakage contamination, the condensate is drained via conduit 34. FIG. 5 shows a multi-stage arrangement on the pressurized water side and the heat utilization equipment side. Although this figure shows an example of a three-stage arrangement, it is also possible to have more or fewer stages, and the number needs to be determined on a case-by-case basis. The heated pressurized water flows from heat exchanger 21a through conduit 22a and sequentially through pressure relief tanks 26a, 26b, 26c. These pressure relief tanks are connected to each other by water conduits 33a, 33b. From the last pressure relief tank 26c, pressurized water passes through conduit 33c to pump 24, which conveys cooled pressurized water through conduit 19 to heat exchanger 18. In the pressure relief tanks 26a, 26b, 26c, the pressure of pressurized water is adiabatically removed, and the water vapor generated at this time is sent to heat exchangers 23a, 23b, 23c for heating via conduits 27a, 27b, 27c. . These heat exchangers 23a, 23b, 23c
is exhausted from conduits 35a, 35b, and 35c. During this exhaust process, the conduits 35a, 35
To compensate for the amount of water discharged from b and 35c,
Replenishment water is supplied into the conduit 19 from a conduit 42 . The condensate generated by the condensation of water vapor in the heat exchangers 23a, 23b, 23c is transferred to each conduit 2.
It is discharged from these heat exchangers via 8a, 28b, and 28c, and is checked for purity in a purity tester 29. If the specified purity is detected,
The condensate is transferred from the purity tester 29 to the conduit 30 to the pump 3.
1 and conduit 32 to conduit 33 of the pressurized water circulation circuit.
c and if it does not reach the specified purity, it is discharged through conduit 34. Heat exchanger 23
a, 23b, 23c are evaporators 37a, 3, respectively.
7b, 37c, and the aqueous solution flows through these evaporators through pipe lines 38a, 38b, 38.
c, 38d, and flows in the above order. The energy supplied to the heat exchangers 23a, 23b, 23c by condensing the water vapor evaporates the water vapor from the aqueous solution, so that the evaporators 37a, 37b, 37
A suitable pressure is maintained within c. The water vapor is condensed by cooling water in condensers 39a, 39b, 39c, which are connected to conduits 40a, 4
It is exhausted from 0b and 40c. In this case, cooling water is supplied through conduit 41a and discharged through conduit 41b. If the cooling water flows through these condensers in sequence, the order of 39a, 39b, 39c:
It is expedient for the cooling water to flow through countercurrently to the solution and cocurrently to the pressurized water. By flowing the pressurized water, solution and cooling water in this direction, the existing temperature gradient is utilized to the maximum, i.e. the heat exchange area is reduced, since the boiling point of the solution increases as its concentration increases. It is based on the fact that it increases accordingly. The table shows four examples for FIGS. 1-3. These examples relate to a sulfuric acid production plant with a production capacity of 1000 tons/day of H ₂ SO ₄ . The table shows two examples for FIGS. 4 and 5. These embodiments relate to the configuration of heat utilization equipment. Example 1 is designed for a roasting gas containing 8 volume percent SO ₂ obtained in the cold,
and concerns conventional catalysts based on four-stage catalyst shelves. Example 2 concerns a dual catalyst for treating hot sulfur combustion gas containing 10 volume percent SO ₂ with three shelves in front of the intermediate absorber and one after it. It is based on a contact system with each shelf. Example 3 concerns a dual catalyst for treating a cold-obtained incineration gas containing 8 volume percent SO ₂ , also with three shelves before the intermediate absorber and It is based on a contact system with one shelf each at the back. Example 4 relates to a dual catalyst for the treatment of a cold-obtained incineration gas containing 16 volume percent SO ₂ with three shelves before the intermediate absorber; Based on a contact system with two shelves at the back. Example 5 shows that the available energy provided by pressurized water B is used to heat the inorganic acid. In Example 6, the available thermal energy provided by pressurized water B was converted to 27% P ₂ O ₅ phosphoric acid.
It has been shown to be used to concentrate P ₂ O ₅ up to 54% in a multistage configuration.

【table】

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【table】

The main advantage of the invention is that the temperature of the cooling medium B can be higher than the maximum temperature that can be reached in the acid heat exchanger, or can reach the same temperature with relatively little outlay. By using closed cooling circuit A and adjusting the circulation rate of the cooling medium, it is ensured that even if the operating conditions of the contactor change, the gas temperature will fall below its dew point before SO ₃ is absorbed. Avoided. Acid heat exchangers can be operated at relatively low temperatures. The invention can be summarized as follows. _SO2 contained in the gas is catalytically converted to _SO3 ,
The SO ₃ -containing gas is cooled by cooling medium A before the SO ₃ is absorbed, the absorbed acid is cooled by cooling medium B, and the heat of cooling medium B is transferred to the heat utilization equipment. In order to increase the temperature of the cooling medium B or reduce its cost and to prevent the temperature of the SO ₃ -containing gas from falling below the dew point, the SO ₃ -containing gas is first transferred by indirect heat exchange and then in a closed circuit. By a second indirect heat exchange with the cooling medium A guided through it, the sulfuric acid cooling circuit of the absorber is cooled to a temperature slightly above the dew point of the SO ₃ -containing gas.
This liquid cooling medium B, which has been cooled and heated by indirect heat exchange with the liquid cooling medium B guided in a closed circuit, is further heated by indirect heat exchange with the heated cooling medium A. The high-temperature cooling medium B is cooled by indirect heat exchange with heat utilization equipment.

[Brief explanation of the drawing]

FIG. 1 is a schematic representation of the mode of operation according to the invention for an intermediate absorber and a final absorber; FIG.
FIG. 3 is a schematic diagram illustrating a combination of operating formats in an intermediate absorber and a final absorber, such that two parallel sub-streams of the cooling medium B are further heated by the cooling medium A of the intermediate absorber as well as the final absorber; In Figure 3, cooling medium B is first cooled by cooling medium A in the final absorber,
The intermediate absorber and the final absorber are then heated in succession by the cooling medium A of the intermediate absorber, with the intermediate absorption taking place preferably in a bench-lily absorber used for high-temperature absorption in co-current flow. Figure 4 is a schematic diagram showing the combination of work formats in Figure 1, and schematically shows a work format based on adiabatic expansion of cooling medium B, and the water vapor generated in that case is used to heat the heat utilization equipment. The diagram of the type used for heating and in which the condensate of this water vapor is returned to the cooled cooling medium B via the test point, FIG. 5, complements FIG. Fig. 2 schematically shows the working mode by adiabatic expansion of pressurized water in stages, as well as the circuit of the heat utilization equipment; In addition, in the symbols used in the drawings, 1, 3, 4,
5, 7, 8, 10, 12, 13, 14, 17, 1
9, 20, 22... Conduit, 2, 6, 18, 21...
... Heat exchanger, 11 ... Absorber, 15 ... Receiving tank, 23, 25 ... Heat utilization equipment, 26 ... Pressure removal tank, 29 ... Purity tester, 36 ... Steam condensing device, 37a, 37b , 37c...evaporator, 3
8... Medium, 38a, 38b, 38c... Pipeline, 39a, 39b, 39c... Condenser,
A, B... cooling medium.

Claims (1)

[Claims] 1. Catalytic conversion of SO ₂ to SO ₃ , multi-stage cooling of the SO ₃ -containing gas, and absorption of SO ₃ into concentrated sulfuric acid, during which heat is indirectly exchanged from the sulfuric acid circulation stream performing the absorption. sulfuric acid from an SO ₂ -containing gas, which is transferred to a cooling medium by means of a cooling medium, which is led into a circulation circuit, and from which heat is transferred by indirect heat exchange to heat utilization equipment. In the production method, the SO ₃ -containing gas is first cooled by indirect heat exchange before it enters the absorber, and then the SO 3 -containing gas is cooled by indirect heat exchange with cooling medium A guided in a closed circuit. ₃ Cool the sulfuric acid circulation stream to a temperature slightly higher than the dew point of the gas it contains, and cool the sulfuric acid circulation stream that performs absorption by indirect heat exchange with liquid cooling medium B guided in a closed circulation circuit. Cooling medium B
A method for producing sulfuric acid, characterized in that the sulfuric acid is further heated by indirect heat exchange with a heated cooling medium A, and the high-temperature cooling medium B is cooled by indirect heat exchange with a heat utilization device. 2. A method according to claim 1, characterized in that the liquid cooling medium B consists of pressurized water. 3. The method according to claim 1 or 2, characterized in that the cooling medium A consists of pressurized water. 4. The method according to claim 3, characterized in that pressurized water as cooling medium A is completely evaporated by indirect heat exchange, and its vapor is condensed by indirect heat exchange with cooling medium B. . 5 Completely evaporate pressurized water as cooling medium A through indirect heat exchange, condense the vapor through heat exchange with a second heat utilization device, and use this high-temperature condensate to heat cooling medium B. The method according to claim 3, characterized in that: 6. According to any one of claims 1 to 5, the cooling medium A at 120° C. to 180° C. is subjected to indirect heat exchange with SO ₃ -containing gas and is guided countercurrently. Method described. 7. In the final absorption carried out cold, the cooling medium B is first heated in the sulfuric acid circulation stream of the intermediate absorber;
7. A method as claimed in claim 1, characterized in that further heating is subsequently carried out with the cooling medium A of the final absorber and the cooling medium A of the intermediate absorber. 8. Process according to claim 7, characterized in that, before heating the cooling medium B with the sulfuric acid recycle stream of the intermediate absorber, it is first heated with the sulfuric acid recycle stream of the final absorber. 9 Claim 2, characterized in that the heated pressurized water B is subjected to adiabatic pressure removal in a heat utilization device, and the water vapor generated at that time is condensed in a heat exchanger of the heat utilization device. ~The method according to any one of paragraphs 8. 10 Adiabatic pressure removal of pressurized water is carried out in multiple stages connected in series in a water circulation circuit, and the water vapor generated in each stage is condensed separately in separate heat exchangers in multiple heat utilization devices. 10. The method according to claim 9, characterized in that: 11 Each heat exchanger in a heat utilization device is connected in series, and the thermal energy absorption medium of the heat utilization device is made to flow countercurrently to the medium B in a direction that increases the temperature of this thermal energy absorption medium to exchange heat. 11. The method according to claim 10, characterized in that the method is passed through a container. 12 Claim 9, characterized in that the condensate generated in the heat exchanger of the heat utilization equipment is collected, its purity is inspected, and only when the condensate is pure, it is returned to the pressurized water B circulation circuit. The method according to any one of Items 1 to 11. 13. The method according to any one of claims 9 to 12, characterized in that a heat exchanger of a heat utilization device is used to heat an evaporator for concentrating an aqueous solution. 14. The method according to any one of claims 9 to 13, characterized in that a steam condenser is connected before the heat exchanger in the heat utilization equipment.