DE2635557A1 - METHOD FOR GENERATING HEAT USING AN ABSORPTION THERMAL TRANSFORMER - Google Patents

Description

Method for generating heat by means of an absorption thermostat

motransformators

The invention "relates to a method for producing Heat by means of an absorption thermal transformer.

It often happens that significant amounts of heat are lost due to the fact that the temperature level at which they are made available is too low. A refinery, for example, emits a large part of the heat that it generates at a temperature level that, for example ^{, can comprise 50 to 150 0} G and which is considered to be too low to reuse this heat. Geothermal energy can also raise the problem of using warm water, which comes from underground water sources and whose temperature is below the desired useful temperature.

The need to use energy economically means that in all of these cases it is desirable to have a means of increasing the To use the temperature at which these calories are available. To achieve this, it is possible to use a heat pump

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work, the heat pump allows the use of calories at a higher temperature than the temperature at which they are initially available, but on condition that there is a job W = Q / η, where Q is the amount of heat available and η is the coefficient of performance of the heat pump. -. The work W is. even in the majority of cases based on the heat of combustion obtained with an efficiency that is well below 1, e.g. on the order of 0.3. A system operating as a heat pump sets in under these conditions an interesting solution from the standpoint of the economic use of energy only if the system is equipped with an increased Coefficient of performance works.

Another solution is to use a trithermal cycle to proceed through the realization of a thermal transformer. The possibility of realizing a thermal transformer is theoretically shown by R.Vichnievsky (Thermodynamic ^ appliquee aux machines - Masson et Gie 1967).

Such a heat exchange system with a cold source with an absolute temperature T, operating under reversible conditions, allows the transformation of an amount of heat Q at the absolute temperature T into an amount of heat Q ¹ with the temperature T ¹ , where the process of equation Q (1 - _o_) = Q ¹ (1 - o).

T! F

In particular, it is therefore possible to transform an amount of heat Q at temperature T into a smaller amount of heat Q ¹ at temperature T ', which is above temperature T ,? where the ratio 8 - necessarily below the theoretical ratio -

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nisses from (1 - jo) / (1 - ^ o).

T T '

The possibilities opened up by such systems are in the Practice not yet fully explored. It has been found that it is possible to use an absorption system to produce a thermo to realize a transformer that allows the temperature level of low-level heat by making the system work in a distinctly isobaric cycle, which is no-up technology known today is possible and what it allows, only one to apply a very small amount of mechanical energy.

The invention is therefore based on the object of providing a method create, which makes it possible, with the smallest possible amount of mechanical energy to be put in, an amount of heat lower temperature levels to raise to a higher temperature level.

The invention relates to a method for generating heat at a temperature A based on within a temperature range B available heat, the temperature A being above the temperature range B.

The solution to the problem is that according to the invention a one brings a gaseous fraction of a working fluid into contact with a liquid phase which is used as a solvent in order to add at least a portion of the gaseous phase to the liquid phase dissolve by releasing heat of temperature A, b: The according to The solution obtained in step a is brought into contact with a stream of a transport gas, so as to at least partially desorb said gaseous working iTuid fraction and to a

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gaseous mixture of the working fluid fraction and the transport gas the heat of desorption being the range of temperature B is removed. <j: The gaseous mixture thus obtained is subjected to fractionation by at least partial liquefaction, phase separation and evaporation to at least two to obtain different, gaseous fractions G and H, the evaporation by removing the heat from the temperature range B is accomplished and d: The gaseous fraction G becomes the stage a as the gaseous working fluid fraction and the gaseous fraction H becomes stage b as a transport gas stream sent back·

The heat of absorption generated in the step a is not necessarily recovered directly in the absorption zone. It can also serve to use one of the existing liquid components to evaporate, the subsequent condensation of which enables heat to be produced at an increased level (see example 3). Likewise, the heat of desorption in the course of stage b is not necessarily directly through the external heat source in the Desorption zone supplied.

A temperature may comprise a range between 80 and 250 ⁰ G, for example. The temperature (or the temperature range) B can be between 20 and 150 ^° C., for example.

If the exchange of heat is carried out in a temperature range and not under a fixed temperature, it is evident that that the temperature interval A is at least partially above the temperature interval B.

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The solvent can usually be a polar solvent such as water, dimethylformamide, dimethyl sulfoxide, n-methylpyrrolidone, tributyl phosphate, ethylene glycol, diethylene glycol, Benzyl alcohol or aniline. In certain cases it is equally possible to use a "hydrocarbon" as solvent, for example selected from paraffins.

The absorbed fraction G-, which will be called dissolved or working fluid, can, for example, by ammonia, an alcohol such as methanol, a ketone such as acetone or by a paraffinized hydrocarbon such as butane or propane or by an aromatic hydrocarbon such as benzene or more be formed by a chlorinated and / or fluorinated hydrocarbon vapor from the range of the freons such as fluorotrichloromethane or difluorodichloromethane. In general terms, any gas which is chemically stable under the temperature and pressure conditions under which one operates may be appropriate, provided that the gas is heat dissolvable in the solvent, for example 50 cal / g and preferably as high as possible.

The desorption is carried out by introducing a gaseous purge stream H. The purge stream H can be formed by a gas which does not condense at the temperature at which the desorption is brought about, such as nitrogen or hydrogen, for example. In this case, a gaseous mixture is obtained, formed by the flushing stream H and the desorbed solution fraction G, and the solution fraction G is separated by passing the mixture through a condenser, which is caused, for example, by the external cooling medium such as

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Water or air is cooled. This is how you get at the exit of the! Condenser a liquid solution fraction G, which is finally evaporated, thereby removing the heat from the range of temperature B takes out.

The purge stream H can likewise be formed by a vapor of a component which can be "condensed at the system pressure and at the cooling temperature of the condenser", the component being, for example, a hydrocarbon such as butane if a light gas such as ammonia is desorbed. The gaseous mixture formed by the flushing stream and the desorbed portion of the solution is in this case separated by passing through a cooled condenser, for example through the external cooling medium. At the outlet of the condenser, either (a) a liquid fraction H is obtained, which is finally evaporated by removing heat from temperature range B and again results in a gaseous purge stream, and (b) a gaseous fraction G, or two liquid fractions G and H, which are finally evaporated separately and take the heat of evaporation from temperature range B.

The fractionation of the gaseous mixture can equally be carried out by any other known method such as, for example, distillation.

The contact between the liquid phase and the gaseous phase in the course of the desorption is preferably carried out in a countercurrent process in order to achieve as complete a desorption as possible obtain. The absorption and desorption ovens are preferred

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wisely carried out in columns in the manner most frequently used can be used in chemistry to carry out this procedure, but other devices, in particular Means involving mechanical movement can be used.

The invention is illustrated by the following examples which show how such a system can be implemented.

example 1

The example is explained by FIG. One sends through

3. Hour *
line 1 23m / ^{v of} a gaseous mixture at the pressure of 4 atm and the temperature of 35 ° C, the following composition being present in molar fractions:

η-butane - 0.906

Ammonia - 0.077

Water - 0.017

This mixture is cooled down to a temperature of 25 ° C in the water-cooled condenser 01. A partial one is thus obtained Liquefaction of the butane and the mixture is passed via line 2 into the decanting vessel B1. From this container occurs through line 3 a flow line of 1,698 kg / shmde of liquid butane and, through line 4, a gaseous mixture which has the following composition in molar fractions Has:

η-butane - 0.575

Ammonia - 0.348

Water - 0.077

This gaseous mixture passes the exchanger E3, from where it ^{exits via line 5 at a temperature of 54 0} C to in

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a tray column T2 to be sent. The tray column T2 has has a diameter of 10 cm and comprises 15 perforated floors. In this column, the gaseous mixture is in countercurrent with a brought into contact water-containing phase, which flows in via line 9. The flow rate of the water-containing phase is

■ hour . ,
241 1 / Y. The ammonia contained in the gaseous mixture is absorbed by the water and a gaseous mixture emerges from the column via line 8, which has the following composition in molar fractions:

η-butane - 0.882 water - 0.118

This mixture passes through the heat exchanger E3, which it uses .Line 12 leaves, then the condenser G2, in which the mixture is condensed with heat dissipation through indirect contact with the cooling water of the condenser. This gives two liquid fractions, which are separated in the container B2.

ι hour i A flow rate of 9 l / .v water is obtained through line 16, which is taken up by pump P4 and mixed in line with the aqueous solution, originating from column 11 and supplied via line 21. Via the line 15 wins

/ Hour / ^ butane, which by the

Pump P5 is added, which it sends via line 17 to to mix it in line with the butane flowing in via line 14.

The tray column T2 operates at a head pressure of 3.8 atm and the soils are at a clearly constant temperature

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of 80 ⁰ C. The heat of solution is removed dtirch indirect contact exchanger with a stream of n-pentane, which enters via line 6 and exits via line 7 and is completely vaporized during the exchanges. This gives 4.5 kcal / s at 80 ^° C.

The aqueous ammonia solution is drawn off via line 10, taken up by pump P1 and finally passes exchanger E2, which it ^{leaves at a temperature of 51 °} C., after which it is sent via line 11 into tray column T1. The tray column T1 has a diameter of 10 cm and comprises 15 perforated trays.

The liquid butane contained in the container B1 is supplied via the line 3 fed to the exchanger E1, which it receives via line 13 at ■ Leaves a temperature of 35 ° C and is by the pump P2 added, which enters the liquid butane into line 14. The butane arriving via line 14 and that via the line

17 incoming butane are mixed in line and over the pipe

18 to the evaporator R1, in which the butane evaporates under a pressure of 4.2 atm with absorption τοη 39.9 kcal / s at a temperature of 43 ⁰ C at the heat source of the evaporator. The vaporous butane is fed via line 19 to the tray column T1. In column T1, the ammonia contained in the aqueous solution, which flows in via line 11, is then desorbed by the butane stream. The tray column T1 operates with a tray pressure of 4.2 atm and the trays are at a clearly constant temperature of 40 ^° C. The heat of desorption - 4.6 kcal / s - is supplied by an isopentane stream that enters through line 24 and via line 23 under complete

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Condensation emerges in the course of the exchange.

This system has thus delivered heat of 80 ⁰ O on the basis of an absorbed heat between 40 and 43 ⁰ O.

Belsplel. 2

Example 2 is illustrated in FIG. One sends over

VS hours ,
of your gas mixture with the pressure of 10 atm

and the temperature of 24 ⁰ C, the following composition being present in molar fractions:

Nitrogen - 0.73 η-butane - 0.27

This mixture is cooled to a temperature of 15 ° C. in the condenser 01. This gives a liquid fraction of butane and the mixture is sent via line 2 to the decanting tank B1. From this container comes from the line 3 a

ν hours . ,

Flow rate of 33.1 kg / V liquid butane and via the line 4 a gaseous mixture with the following composition in molar fractions:

Nitrogen - 0.83 η-butane - 0.17

The liquid butane emerging from the vessel B1 passes the exchanger E1, which it leaves via the line 14 at a temperature of 75 ° 0, is then taken up by the pump P2 and sent to the evaporator R1, in which the butane is under pressure of 9.8 atm and taking up τοη 638 oal / »fcti a tem-

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temperature of 79.5 ⁰ O evaporated at the heat source of the evaporator, after which the butane vapor is sent via line 5 into the column T2. The column T2 is a packed column with a diameter of 10 cm and filled with Raschig rings with a diameter of 0.6 cm. The column T2 operates at a pressure of 9.9 atm at its base and with a clearly constant temperature of 120 ^° C. The butane dissolves in a stream of n-decane which circulates in countercurrent and via line 9 into the column T2 is directed. The flow rate of the n-decane is

eat hour.
414 kg / ^v . The heat of solution of the butane is dissipated via a stream of water which enters through line 6 and exits through line 7 and is completely evaporated in the course of the exchange. Is obtained as 187 cal / s at 120 ⁰ O. Through line 10, the butane solution is withdrawn within the n-decane was added by the pump P1 and passes through the exchanger E2, after which the solution is passed through the line 11 into the column 11 . The column T1 is a packed column with a diameter of 10 cm and filled with Raschig rings with a diameter of 0.6 cm. The gaseous mixture of nitrogen and butane, which leaves the container B1 through the line 4, enters the exchanger E1, which it leaves at a pressure of 9.7 atm and then through the compressor K1 to a pressure of 10.5 atm is compressed, then the mixture is introduced through line 19 into column T1. In the column T1, the butane contained in the n-decane is partially desorbed by the gas stream. The column operates at a temperature T1 which is considerably constant at 80 ⁰ C, the heat of desorption - 374 cal / s - is provided by a Heptanstrom available, the vapor through the

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Line 22 enters and completely condensed in the course of the exchange exits through line 23 again.

The system has thus delivered a heat of 120 ⁰ ″ when absorbing 80 ⁰ O.

Example 5

Example 3 is illustrated in FIG. Through the line

/ Hour /
^v Steam, formed from 79 wt .- # ammonia and 21 wt .- # water, into the absorption column 52 at a temperature of 100 ° C. and a pressure of 4.5 kg / cm. In the head of the absorption column 21 a liquid appears through the line 32

^ Hour, flow rate of 10 tons / ^V , formed from water which contains 0.2 wt .- # ammonia and has a temperature of 113 ° O. The column T1 is adiabatic and as a result of the heat released by the absorption of the ammonia, the water is evaporated. In the top of the column, the temperature is 140 ⁰ O at a pressure of

P »hour;

4 kg / cm and one receives through the line 33 1 ton / ^V steam, formed from 95 wt .- ^ water and 5 wt .- ^ ammonia. This steam condenses between 140 and 130 ⁰ O in the exchanger E4 and delivers

^ Hour,

525 kcal / ^v of an external fluid which flows in through line 34 and flows out via line 35, after which it leaves exchanger E4 via line 37. Via line 36 to taps into the column by means of the pump P1, a liquid flow rate of 7.2 tons / ^V from the column at a level having a temperature of 120 ⁰ C. This liquid flow rate is sent into line 38 by pump P1 and mixed in line with the liquid flow rate supplied by line 37

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originates, the mixture thus obtained through the line 39 is added to exchanger E5.

A solution of 15% is taken from the bottom of the column Ammonia at a temperature of 100 ° O. This solution is over led away line 40 and mixed in line with the liquid flow rate resulting from line 41. The so The resulting mixture is introduced into the top of the stripping column T1 through line 42.

In the bottom of the column T1 is added via line 43

^ Hours,

151 K moles / leg of transport steam, its composition in molar Fractions the following is:

n-butane 0.30 Isopentane 0.45 n-hexane 0.25

This vapor allows the ammonia contained in the solution to be carried along. The heat of desorption is generated by the supply of

■ hour /
646 Kcal / ^V , obtained by cooling an external fluid flowing in through line 25 and exiting through line 26. The temperature in the column is 100 ^° C. at the bottom and 80 ^° C. at the top. A vapor is withdrawn through line 44, the composition of which in molar fractions is as follows;

Hydrocarbons - 0.67 ammonia - 0.26

Water - 0.07

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, Hour,

This steam is mixed with 1.13 tons / V of solvent, which flows in through line 25, in order to bring the weight ratio ammonia / (water + ammonia) to 0.45. The mixture is sent through line 66 into exchanger E8, then through line 47 into condenser 01. At the outlet of the condenser "the temperature is 30 ⁰ O and the mixture" forms two liquid phases, a hydrocarbon fraction and an aqueous fraction, formed by an ammonia solution. These two liquid fractions are added to container 331 through line 48. The hydrocarbon phase leaves the container B1 through the line 49 and is then fed by the pump P2 through the line 50 into the exchanger E8, then through the line 51 into the exchanger E7. In the exchanger B7 it is heated by an external fluid which flows in through the line 52 and through the

^ Hour>

Line 53 flows off and its cooling yields 856 Kcal / * ". Completely vaporized, it leaves exchanger E7 through line 43 at a temperature of 10O ⁰ O. The aqueous phase leaves container B1 through line 54" and is pumped via pump P3 passed through line 55 into exchanger E8 and then through line 56 into exchanger E6. In the exchanger E6, it is heated by an external fluid which flows in through the line 57 and flows out via the line 58 and cools it down

i hour
158 Kcal / ^V supplies, then it is given through line 59 into container B2. Been in the container B2, the temperature is 10O ⁰ C and to obtain a vapor which is sent through the line 31 into the column T2 and contains a liquid fraction of 16 wt .- ^ ammonia supplied through line 60 via the column T1 is.

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A solution of 0.2 is obtained at the bottom of column T1 Ammonia, which is drained from the column through line 61. This solution is taken up again by the pump P4 and sent through line 62 into exchanger E5, from where it is sent through line 32 into column T2.

In the exchanger E5, on the other hand, flows through the line 39 the Head solution. This solution is through the line 63 in the container B3 given, from where one anticipates the flow through line 45, which serves to dilute the vapor which is at the head the column 11 exits. 7.07 tons of solvent are passed through line 64 from which is given by the pump P5 through the line 65 in the head of the column 11.

Finally, heat between 130 and 140 ° 0 (temperature range A) was generated by ^{consuming heat between 80 and 100 0} G (temperature range B).

It will be seen from these examples that the method allows heat to be generated at relatively elevated temperatures and with the use of reduced pressure, which allows the cost of the apparatus to be reduced. It is also shown that the absorption stages and the desorption stages can be carried out at clearly the same pressures, which makes it possible to avoid a high expenditure of compression work. According to Example 3, it is no less obvious that it is in certain cases to facilitate ^he ^ desorption possible to De sorpt ions stage carried out under a pressure which is lower than the pressure at which the absorption step is carried out.

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Claims (17)

Claims Method for generating heat from a temperature A based on within a temperature range B is available provided heat, the temperature A being above the temperature range B, characterized in that a gaseous fraction of a working fluid is in contact brings with a liquid phase, which is used as a solvent, to at least part of the gaseous To dissolve the phase in the liquid phase by releasing heat at temperature A, b the solution obtained according to step a is brought into contact with a stream of a transport gas in such a way as to at least partially to desorb said gaseous working fluid fraction and to form a gaseous mixture of the Working fluid fraction and the transport gas to be obtained, the heat of desorption being the range of temperature B is removed, The gaseous mixture thus obtained undergoes a fractionation subjected by at least partial liquefaction, phase separation and evaporation to at least two to obtain different, gaseous fractions G and H, the evaporation by removing the heat from the Temperature range B is accomplished and d the gaseous fraction G becomes stage a as gaseous Working fluid fraction and the gaseous fraction H is sent back to stage b as a transport gas stream. 703808/0835 2. The method according to claim 1, characterized in that the fractionation stage c is realized by partial liquefaction, whereby one of the fractions G- and H in the gaseous and the other is recovered in the liquid state, followed by a separation of the gaseous fraction G or H and the liquid Fraction H or G and an evaporation of the separated liquid fraction to produce a second gaseous fraction H or G to deliver, this evaporation is carried out by removing the heat from the temperature range B. 3. The method according to any one of claims 1 or 2, characterized in that that the liquefaction of stage c by cooling the gaseous mixture in indirect contact with an external Cooling medium is carried out, which is available in temperature range B. 4. The method according to any one of claims 1 to 3, characterized in that that the desorption of stage b is carried out by a countercurrent contact between the solution and the transport gas stream will. 5. The method according to any one of claims 1 to 4, characterized in that that at least one of the components of the gaseous fraction, which in step a with the release of heat of the temperature A is absorbed is ammonia. 6. The method according to any one of claims 1 to 4, characterized in that that at least one of the components of the gaseous fraction, which in stage a with the release of heat of the temperature 709808/0835 for A is absorbed is a hydrocarbon. 7. The method according to any one of claims 1 to 4, characterized in that that at least one of the constituents of the gaseous fraction, which absorbs the temperature A with the release of heat is a chlorinated and / or fluorinated hydrocarbon. 8. The method according to any one of claims 1 to 7, characterized in that that the transport gas stream which is used to carry out the desorption of stage b is a gaseous hydrocarbon contains. 9. The method according to any one of claims 1 to 7, characterized in that that the transport gas stream which is used to carry out the desorption of stage b contains nitrogen or hydrogen. 10. The method according to any one of claims 1 to 9, characterized in, that at least one of the components of the liquid phase, which is used as a solvent, is a polar solvent is. 11. The method according to any one of claims 1 to 9, characterized in that that at least one of the constituents of the liquid phase used as the solvent is water. 12. The method according to any one of claims 1 to 9, characterized in that that at least one of the components of the liquid phase, which is used as a solvent, is a hydrocarbon 709808/0835 fabric is. 13. The method according to any one of claims 1 to 12, characterized in that that the pressure within the system is between 1 and 50 bar absolute. 14. The method according to any one of claims 1 to 13, characterized in that the temperature A ^{comprises a range between 80 and 250 0} G and the temperature interval B comprises a range between 20 and 150 ⁰ O. 15. The method according to any one of claims 1 to 14, characterized in that that fraction H is liquefied in the course of stage c, then the fraction is separated from the non-liquid fraction G- and then fraction H is evaporated by removing the heat from temperature range B. 16. The method according to any one of claims 1 to 14, characterized in that that fraction G is liquefied in the course of stage c, after which it is separated from the non-liquid fraction H. and the fraction G- is evaporated by removing the heat from temperature range B. 17. The method according to any one of claims 1 to 14, characterized in that that in the course of stage c the fractions G and H are liquefied, then these are evaporated separately and separately by taking the heat from temperature range B. 709808/0835 Blank page