IE912356A1

IE912356A1 - Mixtures of substances for absorption heat pumps and¹absorption heat transformers

Info

Publication number: IE912356A1
Application number: IE235691A
Authority: IE
Original assignee: Hoechst Ag
Priority date: 1990-07-06
Filing date: 1991-07-05
Publication date: 1992-01-15
Also published as: DK0464840T3; EP0464840A2; PT98239A; DE4021582A1; JPH04226585A; DE59101547D1; EP0464840A3; EP0464840B1; ES2055490T3

Abstract

In the mixture of media for absorption heat pumps and absorption heat transformers, the operating medium comprises at least one tertiary amine and the solvent medium comprises at least one aliphatic monocarboxylic acid of 8 - 18 carbon atoms.

Description

Description Mixtures of substances for absorption heat pumps and absorption heat transformers The present invention relates to mixtures of substances, which can be used in absorption heat pumps and absorption heat transformers for raising the temperature of heat flows to a higher temperature level.

By means of the absorption heat pump, a heat flow of low 10 or medium temperature level can be transformed to a higher temperature level by supplying energy. In the converse absorption cycle namely the heat transformer, the temperature rise takes place without a significant supply of energy, solely by the utilization and quasi disproportionation of a heat flow arising at a medium temperature level. Correspondingly, the output figures of an absorption heat pump, i.e. the useful effect relative to the heat supplied, are always > 1; those of the absorption heat transformer are < 1. The synproportiona20 tion of waste heat and supplied energy in the heat pump is contrasted by the disproportionation without a large need for additional energy of waste heat in the heat transformer.

For both processes, mixtures of substances are already known. They are as a rule based on a non-ideal physical solubility of a low-boiling component in a high-boiling component. The heat gain in the absorption process thus results almost completely from the released heat of condensation of the low-boiling component. For the transfer and transformation of large heat flows, those mixtures of substances have hitherto been selected which are composed of a low boiler with the greatest possible heat of condensation, dissolved in a high boiler which permits the greatest possible degassing widths (ammonia/ water, water/lithium bromide, mixtures of halogenated hydrocarbons, methanol/polyethylene glycol dimethyl ether).

Because of its high vapor pressure, ammonia is restricted 5 to a relatively low temperature range (126.5eC at 100 bar). At higher temperatures, the cost in safety engineering and equipment is no longer tolerable economically.

The water/lithium bromide mixture is suitable for the working range below 150 °C. Above this temperature, corrosion and the risk of crystallization can no longer be controlled. Mixtures of substances with organic components such as methanol or trifluoroethanol as the low boiler and polyethylene glycol dimethyl ether as the high boiler are likewise suitable only for the tempera15 ture range up to about 160°C, because of the solubility conditions (degassing width). The use of halogenated hydrocarbon mixtures is also restricted to operation at relatively low temperatures, because of the solubilities in conjunction with relatively small heats of condensa20 tion.

Accordingly, the invention is based on the object of providing mixtures of working substances for absorption heat pumps and absorption heat transformers, which mixtures can be desorbed and condensed in vacuo or at normal pressure and at a medium to relatively high temperature (100-160°) and can be vaporized and absorbed at a maximum of 12 bar and at a relatively high to high temperature (140-240°) and transport more heat per specific working medium cycle than the known mixtures of substances. Further demands, such as low corrosivity, thermal stability and availability in sufficient quantities for industrial units, should also be met.

It has now been found that mixtures of substances which are composed of at least one tertiary amine as the working medium and at least one aliphatic monocarboxyl ic acid having 8 to 18 carbon atoms as the solvent meet these demands.

The tertiary amine can be selected from the group comprising triethylamine, pyridine, N-methylpyrrolidine, lime thyl pyrrole, N-methylpiperidine, N-methylmorpholine and 2-,3- or 4-methylpyridine, and the aliphatic carboxylic acid can be selected from the group comprising isononanoic acid, caprylic acid, pelargonic acid, capric acid, lauric acid, myristic acid, palmitic acid or stearic acid.

The working medium can be an amine or a mixture of the abovementioned tertiary amines and, likewise, the solvent can be an aliphatic monocarboxylic acid or a mixture of those mentioned above.

The advantage of the mixtures of substances according to the invention essentially is that, in the absorption of the amine, a considerable amount of heat of solution is released in addition to the heat of condensation so that, per kg of working medium, considerably more heat than in the case of the known pairs of substances can be released, whereby the quantity of substance to be circulated is reduced. As a result, smaller equipment can be used, which lowers the investment costs.

In Table 1, the proportions of heat of condensation and heat of solution in the total useful heat for a heat transformer process are listed for the triethylamine/ isonanoic acid pair of substances for various waste heat temperatures and use temperatures. At higher temperatures, the proportion of the heat of solution can be up to about 70% of the useful heat.

Table 1 Waste heat temperature (stripper) °C Useful heat Useful Heat of Heat of Specific circulation of solution f temperature (absorber) •c heat % conden- solution sation % % 100 120 100 74 26 2 100 140 100 58 42 3.5 10 100 160 100 47 53 6 120 140 100 77 23 2 120 160 100 60 40 2.5 120 180 100 47 53 4 120 200 100 38 62 6 15 140 180 100 59 41 2 140 200 100 46 54 3 140 220 100 36 64 4.5 140 240 100 29 71 7 160 200 100 59 41 2 20 160 220 100 45 55 2.5 160 240 100 35 65 3 160 260 100 26 74 4.5 The advantage of utilizing the heat of solution is demonstrated in a comparison of various mixtures of substances in an example of a cyclic process (Table 2). Φ a •P Ό •P £1 CM Ό •P U <0 u •P a c o a o CO •P Ό •P ϋ <ΰ in cn in m rd o o m (N • • • 10 dt cn rd © cn o rd CN 1 1 1 1 1 I • cn n o o m CN X • o 00 CN (β o • rd e o Table 2 MeOH/ TEA/ ο Ή Ο Α (0 A ο A ο (0 •Η o m CN w ft P Φ P Λ £ Id « •H ο ο ο to m rd CN I I f ooo O rd m σι n • o m I I CN · rd X (0 o o CO o CN m co o r* m • • • rd rH I o cn I o I O 1 O( m m • 1 rH 1 CN r* cn rd X • (β o g m m · rd rd Ο I in I r-~ χ o fd 6 o o I CN o o U o φ φ Md P P P Φ o id fl fl P Φ co co 9 Id c x co co P Φ o Φ Φ m N u •P Φ P P P •P 0 <*> P P ft ft Φ P id co ft 0 Φ X rd a 6 g e ft P P fl Φ Φ φ id fl σ O P P P > P •P P P co co id •P id ►t >1 P P 4*-*k u >d Φ co CQ id P $ P O’ u X Φ Φ 6 Φ c ο a fl P P X ft Λ •P •P o Φ rH Φ Φ ft Φ P (0 Md •P •P fl X P ft P Φ •P P 0 (0 •P P u Md P id ft id P P CO id ο fl •P Φ 0 X •P X) CO P Φ η O' Φ rd Md co co P id (0 «0 id Φ ft 0 Md fl X c P fl SE »-r Q co co M *2 •H co •P P Φ Λ P Φ £ +j a> Ό O’ 0 c •H $-1 Φ g Λ rd 3 rd >1 rH g o X >1 p fl P X •H id Φ P ♦d X >1 Φ 4J P r—1 •H •H Φ Q P g ft P II II II II P 8 ! a o o •P Φ M ω XI se ft The invention is explained below reference to the figures, in which: Figure 1 shows the absorption heat simplified, 5 and Figure 2 shows the absorption heat highly simplified. in more detail by pump process, highly transformer process, The heat flow into the system and out of the system is marked Q in both processes and indicated by the direction of the arrow. The location of the centers of the diagrammatically shown parts of the unit, namely stripper, condenser, vaporizer and absorber, in the coordinate system drawn, roughly illustrates the working conditions with respect to the pressure and temperature levels for the particular process.

In the absorption heat pump process (Figure 1), the working medium of the mixture of substances is stripped out of the mixture of substances by supplying heat (for example steam or electrical energy) of 140°C to 240°C, preferably of 160eC to 200°C, and at pressures of 4 bar to 12 bar, preferably 5 bar to 8 bar, by vaporization in the stripper 1. The working medium vapor passes via line 12 into the condenser 2, where the working medium vapor is liquefied, with removal of heat, at unchanged pressure at temperatures of 150°C to 200*C, preferably at 160 C to 180°C. The liquefied working medium passes via line 11 and expansion valve 5 into the vaporizer 3, where it is vaporized by a supply of waste heat of 100eC to 160°C, preferably of 120eC to 140’C, and at pressures of 1 bar to 6 bar, preferably of 2 bar to 3 bar. The solvent depleted of working medium is passed via line 9 and expansion valve 6 from the stripper 1 into the absorber 4. Via line 10, the working medium vapor reaches the absorber 4, where it is absorbed with removal of heat at temperatures of 150°C to 200°C in the solvent expanded to the same pressure. The solvent enriched in working medium is delivered via line 8 and pump 7 into the stripper 1. A new working cycle starts.

In the absorption heat transformer process (Figure 2), the working medium is vaporized in the vaporizer 3 by absorption of heat at temperatures of 100’C to 160°C, preferably of 120“C to 140°C, and pressures of 1.3 bar to .5 bar, preferably 2.3 bar to 3.5 bar. The working medium vapor passes via line 12 into the absorber 4 and dissolves there in the solvent at the same pressure with release of useful heat at temperatures between 140 °C and 240°C, preferably between 160’C and 220eC. The solvent enriched in working medium passes via line 8 and expansion valve 13 into the stripper 1. The stripping of the working medium out of the mixture of substances takes place with supply of waste heat at temperatures of 100°C to 160°C, preferably of 120’C to 140°C, and pressures of 0.1 bar to 0.4 bar, preferably of 0.1 bar to 0.2 bar. The desorbed working medium passes via line 10 into the condenser 2, where the working medium vapor is liquefied at temperatures of 0°C to 30eC, preferably room temperature, and pressures of 0.1 bar to 0.4 bar. The heat of condensation thus released is lost and forms the driving force of the heat transformer. From the condenser 2, the liquid working medium is pumped by pump14 with raising of the pressure via line 11 into the vaporizer 3. The solution depleted of working medium in the stripper 1 by the desorption of working medium is pumped by pump 15 with raising of the pressure via line 9 back into the absorber 4 and, in the latter, can absorb again working medium vapor from the vaporizer 3.

Claims

1. Patent Claims:

1. A mixture of substances for use in absorption heat pumps and absorption heat transformers, composed of at least one tertiary amine as the working medium 5 and at least one aliphatic monocarboxylie acid having 8-18 carbon atoms as the solvent.

2. A mixture of substances as claimed in claim 1, wherein the tertiary amine is selected from the group comprising triethylamine, pyridine, N-methyl10 pyrrolidine, N-methylpyrrole, N-methylpiperidine, Nmethylmorpholine and 2-, 3- or 4-methylpyridine.

3. A mixture of substances as claimed in claim 1 or 2, wherein the aliphatic carboxylic acid is selected from the group comprising isononanoic acid, caprylic 15 acid, pelargonic acid, capric acid, lauric acid, myristic acid, palmitic acid or stearic acid.

4. A mixture of substances as claimed in claim 1, wherein the working medium is composed of a mixture of tertiary amines and/or the solvent is composed of 20 a mixture of aliphatic monocarboxylic acids.

5. The use of a mixture of substances composed of at least one tertiary amine as the working medium and at least one aliphatic monocarboxylic acid having 818 carbon atoms in an absorption heat transformer. 25

6. The use of a mixture of substances composed of at least one tertiary amine as the working medium and at least one aliphatic monocarboxylic acid having 818 carbon atoms in an absorption heat pump.

7. A process for raising the temperature of a waste 30 heat source to a higher level by means of an absorption heat pump, using a mixture of substances as claimed in claim 1, composed of working medium and solvent, which comprises stripping the working medium out of the mixture of substances by vaporization by means of supplying heat of 140 e C to 240*C at pressures of 4 to 12 bar, liquefying the working 5 medium vapor with removal of heat at temperatures of 150°C to 200°C, expanding the liquid and vaporizing it by means of supplying waste heat of 100°C to 160°C at pressures of 1 bar to 6 bar, absorbing the vapor in the expanded solvent with removal of heat 10 at temperatures of 150 e C to 200°C and feeding the solvent enriched in working medium to the stripper while raising the pressure to 4 bar to 12 bar.

8. A process for raising the temperature of a waste heat source to a higher level by means of an absorp15 tion heat transformer, using a mixture of substances as claimed in claim 1, composed of working medium and solvent, which comprises vaporizing the working medium of the mixture of substances by supplying waste heat of 100°C to 160°C at pressures of 1.3 to 20 5.5 bar, absorbing the vapor in the solvent with heat removal at temperatures of 140°C to 240°C, expanding the solvent enriched in working medium, stripping the working medium out of the enriched solvent by supplying waste heat at temperatures of 25 100°C to 160 e C and pressures of 0.1 bar to 0.4 bar and condensing it with removal of heat at temperatures of 0°C to 30 e C, feeding the liquid working medium to the vaporization while raising the pressure to 1.3 bar to 5.5 bar and feeding the solvent 30 depleted of working medium to the absorption while raising the pressure to 1.3 bar to 5.5 bar.

9. The process as claimed in claim 7, wherein triethylamine and isononanoic acid are used as the mixture of substances.

10. The process as claimed in claim 8, wherein triethylamine and isononanoic acid are used as the mixture of substances.

11. A mixture of substances as claimed in claim 1, substantially as hereinbefore described.

12. A process as claimed in claim 7, substantially as hereinbefore described .

13. A process as claimed in claim 8, substantially as hereinbefore described .