GB2422652A

GB2422652A - Steam compressor and process for producing steam

Info

Publication number: GB2422652A
Application number: GB0501658A
Authority: GB
Inventors: Torben Boch Andersen; Ralf Matthias Schoth; Flemming Hansen
Original assignee: Danisco AS; Danisco US Inc
Current assignee: DuPont Nutrition Biosciences ApS; Danisco US Inc
Priority date: 2005-01-26
Filing date: 2005-01-26
Publication date: 2006-08-02
Anticipated expiration: 2025-01-26
Also published as: GB0501658D0; WO2006079635A2; WO2006079635A3; GB2422652B

Abstract

The steam compressor 20 includes a first container 1 which contains zeolite 2 that is capable of adsorbing vacuum water vapour 5. A second container 3, wherein water 4 can be fed during the adsorption and high pressure steam 15 can be fed during regeneration, includes at least one common surface 19 with the first container. Heat can be transferred by heat conduction between the two containers via the common surface. A tube 11 allows both the vacuum water vapour 5 in and steam 7 out. The water 4 is fed to the second container via inlet tube 9 and discharged through an outlet tube 10. The high pressure steam 15 is also fed via tubes 9 and 10. The compressor is used in an industrial process for producing live steam from vacuum water vapour that includes bringing the water vapour into contact with zeolite in the first container, wherein water is adsorbed to the zeolite, transmitting the heat produced to liquid water in the second container, and regenerating the zeolite by heating it in order to desorb the adsorbed water as live steam from the zeolite.

Description

PROCESS FOR PRODUCING STEAM AND A STEAM COMPRESSOR

FIELD OF THE INVENTION

The present invent ron relates to an industrial process for producing live steam from vacuum water vapour, and more particularly to a process for recovering heat energy from vacuum water vapour. The present invention also relates to a zeolite steam compressor.

BACKGROUND OF THE INVENTION

Vacuum vapours are generated in the evaporation of fluids or watercontaining materials in reduced pressure. The heat content of the vacuum Wa- ter vapour is significant, and various methods to reutilize it to improve the heat balance of the evaporation systems are in use.

Today the heat energy of vacuum water vapour is not effectively util- ized when considenng quantity and quality. Usually condensers condense the main part of the vacuum water vapour to condensate, which is cooled in the following cooling towers. A smaller part of the vacuum water vapour is reused in heat exchangers for heating. The condensate from an evaporating station, for instance in a sugar factory, is flashed over a condensate tank, where a part of it is reused as vapour in a following evaporator effect. The remaining con- densate is used for instance for the preheating of feed solutions in the heat exchangers. Heat is released from the evaporating station at about 80 to 100 C. This temperature level is often too low for process heat, since initial temperatures of between 100 and 150 C are often needed.

The heat of condensation can also be recovered if the vacuum vapours of a boiling chamber are compressed to a higher pressure by a re- compression system. One of the problems associated with the reuse of vac- uum water vapour is that with the existing steam compressors (mechanical or thermal) the possibility to increase the temperature of water vapour is limited, and thus, the water vapour at a lower pressure must be compressed over sev- eral effects in order to produce pressurised steam useful as a heat source for instance for an industrial-scale evaporator. Thermal compressors have the dis- advantage that they can compress only a part of the vacuum vapour from the evaporator for reuse.

Publication WO 03/097231 describes a method and an apparatus for drying a product using a regenerative adsorbent. According to said method, the product is dried by bringing it into contact with the adsorbent, water being taken up from the product by the adsorbent (for instance zeolite). Subse- quently, the adsorbent is regenerated with superheated steam, and steam is obtained, which steam comprises at least a part of said water. Thus, the su- perheated steam used in the regeneration is applied directly on the zeolite and as a result a stream of a steam "mixture" is formed, said stream comprising the water from the product and the high-pressure steam.

Publication DE 19 607 792 describes a process for adsorption cool- ing of foods which contain water In this adsorption cooling process, the combined vacuum cooling and adsorption process makes use of an adsorption agent (zeolite) together with energy recovery, by the partial recovery of steam condensation and adsorption heat in an adsorption vessel, comprising a vessel in contact with the product. The product is only cooled by vacuum chilling.

Zeolites and other regenerative adsorbent materials have also been used in several other types of drying processes as described in publications DE 19 641 404 and EP 0 435 301 These processes are used for drying agricultural crops, such as coffee extract, or raw or cooked fruits, vegetables or grain. These processes are not used for the production of steam as such.

Zeolite and other regenerative adsorbent materials have also been utilised in heat pump systems as descnbed in publications US 4 034 569, US 4 138 850, US 4 637 218, US 5 237 827 and US 5 729 988. The described methods and apparatuses are closed systems, wherein a working fluid, such as water, is circulated in the system. Low-grade heat, such as solar heat, is used for the regeneration of adsorbent materials. Heat pumps of this type are primarily used for heating and cooling buildings.

The use of zeohte for storing heat has also been described. US pat- ent 5 518 069 describes an apparatus and method for cooling and heating, wherein energy is converted by the sorption of an operating medium by a sorp- tion agent Again, this apparatus and method is not used for the production of steam US patent 6 412 295 discloses a sorption device for heating and cooling gas streams, with a sorberit container which contains a sorbent that takes up a working fluid. A separate working fluid is utilised in the device to activate the sorption agent, which causes the heating of the sorbent. The de- vice comprises a sorbent heat exchanger, which exchanges the heat between a sorbent and a gas stream Examples of the disadvantages associated with the above methods for utilizing a zeolite-type adsorbent for heat recovery from vacuum water va- pour are batch-type, small-scale and/or slow processing due to the use of low- grade heat for the regeneration, and high costs, when the regeneration is done with an expensive heat source such as electricity. A further disadvantage associated with one of the above methods is the mixing of the process gas with high-pressure gas, which causes that the whole adsorption vessel must hold pressures up to 50 bars.

BRIEF DESCRIPTION OF THE INVENTION

An object of the present invention is thus to provide a method and an apparatus for implementing the method so as to alleviate the above disadvantages The objects of the invention are achieved by a method and an arrangement, which are characterized by what is stated in the independent claims. The preferred embodiments of the invention are disclosed in the de- pendent claims.

The invention is based on the realization that zeolite has the prop- erty to attract water vapour and generates heat when adsorbing water vapour.

When zeolite is saturated with water, it can be dried (regenerated) by adding heat to it. Zeolite's ability to alternatively adsorb and desorb water while it emits and adsorbs heat can be utilized for recompressing vacuum water va- pour. The inventive concept is based on the idea of producing live steam in an efficient manner by utilising (a) the heat of a secondary steam stream (vacuum vapour) from the evaporation of water from fluid or water- containing materials, and (b) heat from the adsorption and high-pressure steam.

It is an advantage of the method and arrangement of the invention that in a zeolite compressor, the energy quantity used for regenerating zeolite is independent of the adsorption step. Thus, the pressure of the water vapour adsorbed in zeolite does not affect the energy consumption in the regeneration of zeolite. With existing mechanical steam compressors, the possibility to in- crease the temperature of water vapour is limited. Because of this low effi- ciency, vapour must usually be compressed by multiple compressors Further, the increase in temperature is dependent on the working pressure.

It is a further advantage of the method and arrangement of the in- vention that two different product streams of live steam can be obtained and these steam streams can be employed for conventional purposes in the proc- ess industry for instance for heating A first live steam stream is obtained in the adsorption step when adsorption heat is transferred to a liquid water stream, which is preferably condensate from evaporation at a temperature of from 50 to 100 C. This liquid water is boiled with the adsorption heat for in- stance at 115 C to produce the first steam stream A second live steam stream is produced during the desorption step (regeneration step). The second steam stream is formed of the water adsorbed in zeolite. This adsorbed water evapo- rates from zeolite during the desorbtion step. Even a third steam stream can be obtained if high-pressure steam is used for the regeneration. Then the third steam stream is obtained from the high-pressure steam fed to the heat ex- changer in the regeneration step. For instance, high-pressure steam of 250 C is used for the regeneration; the regeneration is carried out while the steam is condensated and the temperature falls to for instance 200 C. This condensate still has sufficient energy content for use elsewhere for process-technological purposes, for instance it can be flashed to form said third steam stream.

A still further advantage of the method and arrangement of the in- vention is that the process cycle can be shortened by the use of an efficient regeneration system.

DEFINITIONS RELATING TO THE INVENTION

In the specifications and throughout the claims, the following definitions have been used: Vacuum vapour refers to the vapour of water produced by boiling under pressure below the atmospheric pressure.

Zeolite compressor refers to equipment which is capable of raising the temperature of steam with the aid of zeolite.

Live steam refers to fresh steam produced by boiling.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention will be described in greater detail by means of preferred embodiments with reference to the attached drawings, in which Figure 1 is a schematic representation of a zeolite steam compressor; Figure 2 illustrates an example of a zeolite steam compressor (shelland-tube-type); Figure 3 illustrates an example of a zeolite plate heat exchanger (plate-type); Figure 4 is a flow diagram of an evaporator section; and Figure 5 is a flow diagram of a pan boiling section.

DETAILED DESCRIPTION OF THE 1NVENTION

The invention is directed to an industrial process for producing live steam from vacuum water vapour, characterized by the steps comprising a) bringing vacuum water vapour into contact with zeolite in a first container, wherein the water is adsorbed to the zeolite, b) transmitting the heat produced in the adsorption step a) from the zeolite to liquid water in a second container, and C) regenerating the zeolite by heating it in order to desorb the ad- sorbed water as live steam from the zeolite In an embodiment of the invention, the vacuum water vapour has a temperature of 50 to 100 C and a pressure of about 0.1 to 1.0 bara (for in- stance 70 C and about 0.3 bara). Here the absolute pressure is denoted as bara, i.e. "bar absolute". The vacuum water vapour preferably has a constant pressure during the adsorption step, and it can be supplied from an evaporator or pan boiler. In one embodiment, the vacuum water vapour originates from a fluid1 which may be concentrated by vapourizing water at a pressure below the atmospheric pressure. Simultaneous adsorption of water vapour by zeolite and generation of new water vapour by boiling from the fluid will occur to keep pressure and temperature conditions at a relatively constant and stabile level.

The fluid can be from a concentration process, for example juices from sugar processes, fruit juices, vegetable juices, milk products, extracts, hydrolyzates, or spent liquors from a pulp mill.

The liquid water used for the cooling of the zeolite in the adsorption step preferably has an initial temperature of 60 to 100 C, more preferably 90 to 100 C, and the adsorption heat is used for producing live steam by boiling this liquid water in the second container. The liquid water used for the cooling of the zeolite may be condensate water from an evaporator.

In one embodiment of the invention, high-pressure steam is used for the heating of the zeolite in the regeneration step. Said high-pressure steam is preferably used at a temperature of 200 to 300 C. The high-pressure steam can be saturated or superheated, and the pressure is preferably from 15 to 40 bara. The regeneration is carried out with indirect heating through a heat ex- changer. The hot condensate water formed from the high-pressure steam can be recycled to a steam boiler or it can be flashed for the production of steam that has a temperature of 120 to 140 C, for instance.

S In order to produce pressurised steam useful as a heat source for instance for an industrial-scale evaporator, the live steam produced according to invention has preferably a temperature of at least 100 C, more preferably to 120 C, and a pressure of 1.0-2.0 bara, respectively.

Zeolite's property to attract water vapour is so strong that it pro- duces a suction effect when a container containing zeolite is connected to a container with water vapour. As indicated above, when bringing vacuum water vapour into contact with zeolite, zeolite will adsorb the water. This adsorption reaction is exothermic, ie. a heat-generating reaction, in one embodiment of the invention, a heat exchanger is positioned in such a way that it is sur- rounded by zeolite, and the produced heat is transferred to a fluid (e g con- densate water) which is pumped through the heat exchanger. The pressure is kept constant on the condensate side (e.g. water at 115 C, about 1.7 bara).

Since the pressure is kept constant on the condensate side, the condensate on the cooling side starts to boil and 115 C steam is produced. This prevents the temperature of the zeolite from rising more.

In one embodiment of the invention, during the regeneration of the zeolite (desorption), high-pressure steam is fed through the heat exchanger.

Then the heat is transferred from the high-pressure steam to the zeolite by the heat exchanger. As the temperature of the zeolite rises, the water adsorbed to the zeolite starts to desorb. Here the energy transferred from the added high- pressure steam is utilised for the production of live steam, because the water from the zeolite is evaporated as water vapour which can be utilised as live steam. The pressure in the desorption chamber is kept at the desired level.

The produced live steam can be superheated.

In one embodiment, industrially useful steam is produced from vac- uum vapour or heat streams originating therefrom by a method, characterized by the steps comprising a) bringing vacuum water vapour from an evaporator into contact with zeolite in a first container, wherein the water is adsorbed to the zeolite, b) transmitting the heat produced in the adsorption step (a) from the zeolite to a secondary condensate stream from the evaporator in a second container and producing live steam therefrom, c) regenerating the zeolute by heating It with high- pressure steam in order to desorb the adsorbed water as Jive steam from the zeolite, thereby the high pressure steam condensates, and d) producing steam from the condensate in step C) by flashing it.

The invention is also directed to a zeolite steam compressor for heating water streams. Referring to Figure 1, the zeolite compressor 20 of the invention comprises a first container I which contains zeolite 2 that is capable of adsorbing vacuum water vapour 5, and a tube 11 connected to said first container 1 for feeding vacuum water vapour 5 therein, wherein the same tube 11 can be used as an outlet tube for steam 7; a second container 3, wherein an inlet tube 9 and an outlet tube 10 are mounted so that, during the adsorp- tion, water 4 can be fed to the second container 3 through the inlet tube 9 and discharged through the outlet tube 10, and, during the regeneration, the supply of water 4 can be stopped, and high pressure steam 15 can fed to the second container 3 through the inlet tube 9 and discharged through the outlet tube 10; wherein the first 1 and second 3 containers are arranged so that they have a common surface 19 through which heat can be transferred by heat Conduction between said first container 1 and said second container 3.

In an embodiment of the invention, the tube 11 connected to said first container I is a 1-tube with valves 6, 8, which are mounted so that during the adsorption, the valve 6 with vacuum water vapour can be opened, and the valve 8 for outlet steam can be closed and, dunng the desorption, the valve 6 with vacuum water vapour can be closed, and the valve 8 for outlet steam can be opened. In a further embodiment of the invention, the inlet tube 9 and the outlet tube 10 of the second container 3 are both mounted with a T-tube and valves 12, 14, 16, 18 so that, during the adsorption, water 4 can be fed to the second container 3 and discharged through the outlet tube 10, and, during the desorption, it is possible to reset the valves 12, 14. 16, 18 and thereby stop the supply of water 4 and, instead, add high pressure steam 15 to the second con- tainer 3. Preferably, the tube 11 connected to said first container I is equipped with a manifold for the distribution of the water vapour 5 in the first container 1.

Refer-ring to Figure 2, a zeolite compressor of the invention can be constructed as a closed tank 20, in which more layers of zeolite elements 2 and a heat exchanger 26 are placed. In a single zeolite element 2, zeolite is placed around the heat exchanger 26. The heat exchanger 26 can be made into a spiral tube or the like, and it forms the second container 3. The upper side and the lower side of the element 2 should be made with an open struc- ture as a screen or perforated plate for keeping the zeohte in place. This struc- ture allows good contact to the zeolite during adsorption with vacuum water vapour 5 and during desorption, when the water must be evaporated from the zeolite. In order to secure good contact of the vapour with all the zeolite (pow- der or extrudate), the size of the elements 2 is preferably not more than 60 mm.

In this zeolite compressor 20, a tube is connected to the tank for feeding vacuum water vapour 5, optionally with a manifold 27 for distribution of the vapour in the tank 20. By mounting a T-tube 11 and valves 6, 8, the same tube 11 can be used as an outlet tube for water vapour 7, when the steam compressor is to be regenerated. During the adsorption, the valve 6 with vac- uum water vapour is opened, and the valve for outlet vapour 7 is closed, The heat exchangers 26 in the single elements 2 are connected with a joint tube 9, which during the adsorption feeds condensate 4 into the heat exchangers 26.

In the heat exchangers 26, the condensate is heated, and it is discharged as vapour 13 in another joint tube 10 for live steam. Both the condensate 9 and the steam tube 10 are mounted with a T-tube and valves. During desorption it is possible to reset the valves 12, 14, 16, 18 and thereby stop the supply of condensate 4 and, instead, add high-pressure steam 15 to the heat exchanger 26 in order to dry the zeolite The tubes in the heat exchanger system, including the inlet and out- let tubes 9, 10, may be manufactured for a working pressure of at least 40 bar.

The tank 20 may for example be designed to maintain a working pressure of at least 2 bar corresponding to about 120 C saturated steam.

The zeolite steam compressor 20 could eg. also be constructed ac- cording to the same principle as a plate heat exchanger [Fig 3]. Through coat- ing with zeolite on one side of the plates 21, chambers with or without zeolite can alternately be placed through the heat exchanger. Between the plates there are gaskets 22.

The invention can be used in various evaporator installations which utilize steam as a heating medium on the other side of a heat transfer surface and in which evaporated water is removed in the form of water vapour. Some examples of evaporators are falling film evaporators, rising film evaporators, forced circulation evaporators, plate evaporators and pan boilers. Typical of these evaporators is a continuous removal of water steam by boiling under reduced pressure (vacuum). Relatively low pressure and low temperature is especially required when evaporating heat sensitive fluids, such as solutions containing sugars and proteins Due to the low temperature, the produced vac- uum vapour cannot be utilized as steam for boiling, for example, but requires temperature elevation by recompression.

The invention is suitable for evaporator installations which have a temperature difference of at most 50 C between live steam and vacuum water vapour, and this is the increase in temperature which zeolite can generate through the adsorption of water vapour. However, the saturation temperature of the live steam should not be higher than 150 C. As indicated above, it is an advantage of the invention, if the system has e.g. 250 C steam for the regen- eration of the zeolite, but alternatively electric energy can be used as well.

One example of an evaporator to apply a zeolite compressor is a vacuum pan used for the crystallization of sugar. To avoid burning and carmelization, the boiling and evaporation of the sugar liquor during crystallization is commonly carried out at a relatively low temperature and pressure in an ap- paratus known as a vacuum pan.

An example of the industrial application of the zeolite compressor is its use in a multi-stage evaporating section [Fig. 4] or in a pan-boiling section [Fig. 5J of a sugar factory. In one embodiment of the invention, the vacuum water vapour 5 originates from a vacuum evaporator 23 [Fig. 4]. In another embodiment of the invention, the vacuum water vapour 5 is from a pan boiler 25. Normally pan boilers leave some unused water vapour, which is con- densed in a condenser. It would be an advantage, if this water vapour (tem- perature e.g. 85 C) could be recompressed and reused in the pan boilers 25.

In the example illustrated in Figure 5, the process of the invention is utilised in a sugarhouse pan-boiling section so that the temperature of the recompressed water vapour 13 from a zeolite compressor 20 corresponds to the steam used from evaporators (e.g. 115 C). This steam stream 13 is connected to the tube with evaporator water vapour 24 from the evaporator section illustrated in Fig- ure 4. The condensate 4 for the evaporation in the compressor 20 can be sup- plied from the units in the evaporating station, where the condensate has a temperature of 90 to 100 C In the adsorption mode of Figure 5, the vacuum water vapour 5 (e.g. 70 C, 0.3 bara) is fed through a tube to the zeolite steam compressor 20, where through a manifold 27 [Fig. 2] it can be distributed to the chamber 1 and adsorbed by the zeolite 2. The condensate 4 is fed from an inlet tube through the single heat exchangers 26 (Fig. 2], where the generated heat from the zeo- lite vaporizes it With a pressure transmitter 28 [Fig. 5] on the outlet stream 13 and a control valve 12 on the condensate inlet stream 4, it is possible to keep a constant steam temperature by controlling the added condensate quantity.

For the regeneration (desorption) of the zeolite in the compressor 20, it is possible to feed e.g. 250 C high-pressure steam 15 directly from the boilers. The high-pressure steam 15 is fed through the heat exchangers 26 [Fig. 2], and these evaporate the water from the zeolite The inlet for vacuum water vapour 5 is closed with a valve 6, and, instead, the water vapour 7 from the zeolite is fed through the manifold 27 [Fig. 2] and through a branching to the tube with the evaporator steam 24 supply, where it is utilised as live steam.

With a control valve 8 on the branching, it is possible to control the pressure of the water vapour 7 at the right level (for example: 1.7 bara corresponding to a saturation temperature of 115 C; the vapour may be superheated). The con- densate 17 from the high-pressure steam 15 can be used for preheating the feed solution to the evaporator, for instance thin juice (a sugar factory interme- diate), before it enters the evaporating station. Here, the energy used for re- generating the zeolite is reused on one hand for producing live steam and on the other hand for preheating. After the regeneration of the zeolite, the zeolite can be further dried using a gas flow such as hot air. This can be done by blowing hot air through the container containing the zeolite.

it is also possible to use several parallel zeolite compressors 20 in order to smooth the steam flows for instance for continuous evaporation equipment. At least one compressor may then be operated in the adsorption mode and one in the regeneration mode at the same time [Fig 5] The variations in the steam flows depend on the number of compressors and on the re- generation time.

In the present invention, the combination of water and zeolite as sorbents is especially useful. Zeolites are crystalhne minerals which have a regular skeletal structure that contains silicon, aluminum and oxygen in their regular framework. The silicon and aluminum atoms are tetrahedrally coordi-.

nated with each other through a shared oxygen atom Although zeolites are natural minerals that are mined, most zeolites used commercially are produced synthetically. There are numerous naturally occurring and synthetic zeolites, each with a unique structure. Some of the commercial materials are' A, beta, mordenjte, Y and ZSM-5.

The skeletal structure of zeolite comprises a void space (i.e. cavi- ties channels or pores) that can host cations, water or other molecules. In these cavities, water molecules can be taken up while releasing heat. The commercially available pore sizes range from approximately 3 A to approximately 8 A (wherein A = angstrom = 0.i-iO m). Because of zeolites' regular and reproducible structure, they behave in a predictable fashion, it is also an advantage that zeolites are solid substances which do not expand as a result of heat during the adsorption and desorption reactions. The skeletal structure can be readily accessed from all sides by the water vapour molecules. These properties make it easier to design the adsorption/desorption device.

Within the skeletal structure of zeolite, the water molecules are subjected to strong field forces, which bind the molecules in a lattice and liquefy them. The strength of the binding forces that act upon the water molecules is dependent on the quantity of water that is already contained in the skeletal structure and on the temperature of the zeolite. Zeolites can remove water to very low partial pressure and they are very effective desiccants, with a capacity of up to more than 25% of their weight in water. However, for practical applica- tions, up to 25 parts by weight (pbw) of water can be taken up per 100 pbw of zeolite.

There are also a number of different ways that zeolites can be modi- fied. The framework (skeletal structure) of the zeolite can be modified by synthesising zeolites with metal cations other than aluminium and silicon in the framework. The framework can be modified by dealuminatior, to increase the silica and increase the hydrophobic nature of the zeolite. Commercial zeolites are available as powders or as formed products such as extrudates. Since es- pecially zeolite granules are poor heat conductors, the zeolite compressor should be designed so as to ensure that the average heat- conducting path for the transformed quantities of heat is no greater than 3 cm. In the present in- vention zeolites can be used in the form of powders or extrudates, or as a mix- ture of these.

It will be obvious to a person skilled in the art that, as the technology advances, the inventive concept can be implemented in various ways. The in- vention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.

Claims

1. An industrial process for producing live steam from vacuum water vapour, C ara rized by the steps comprising a) bringing vacuum water vapour into contact with zeolite in a first container, wherein the water is adsorbed to the zeolite, b) transmitting the heat produced in the adsorption step a) from the zeolite to liquid water in a second container, and c) regenerating the zeolite by heating it in order to desorb the adsorbed water as live steam from the zeolite.

2. A process as claimed in claim 1, wherein the vacuum water va- pour has a constant pressure.

3. A process as claimed in claim I or 2, wherein the vacuum water vapour has a temperature of 50 to 100 C.

4. A process as claimed in any one of claims I to 3, wherein the vacuum water vapour is from an evaporator.

5. A process as claimed in any one of claims I to 4, wherein the vacuum water vapour originates from a fluid.

6. A process as claimed in claim 5, wherein the heat of the live steam produced in the process is used for evaporating said fluid.

7. A process as claimed in claim 5 or 6, wherein the fluid is a juice from a sugar process, a fruit juice or a spent liquor from a pulp mill.

8. A process as claimed in any one of claims 1 to 7, wherein the adsorption heat is used for producing live steam by boiling the liquid water in the second container.

9. A process as claimed in claim 8, wherein the liquid water has an initial temperature of 60 to 100 C.

10. A process as claimed in claim 8, wherein the liquid water has an initial temperature of 90 to 100 C.

11. A process as claimed in any one of claims 1 to 10, wherein highpressure steam is used for the heating of the zeolite in the regeneration step.

12. A process as claimed in claim 11, wherein the high-pressure steam feed is saturated or superheated steam and has a temperature of 200 to 300 C and pressure of 15 to 40 bara.

13 A process as claimed in claim 11 or 12, wherein the high- pressure steam condensates as a hot condensate water during the regenera-.

tion step.

14. A process as claimed in any one of claims 11 to 13, wherein the condensate water formed from the high-pressure steam has a temperature of to 200 C.

15. A process as claimed in any one of claims 11 to 14, wherein the hot condensate water formed from the hugh-pressure steam is recycled to a steam boiler.

16 A process as claimed in any one of claims 11 to 15, wherein the hot condensate water formed from the high-pressure steam is flashed to produce steam.

17. A process as claimed in claim 16, wherein the produced steam has a temperature of 120 to 140 C.

18. A process as claimed in any one of claims 1 to 17, wherein the produced live steam has a temperature of at least 100 C.

19 A process as claimed in any one of claims 1 to 17, wherein the produced live steam has a pressure of at least 1.0 bara.

20. A zeojite steam compressor (20) for heating water streams, comprising a first container (1) which contains zeolite (2) that is capable of adsorbing vacuum water vapour (5) and a tube (11) connected to said first con- tainer (1) for feeding vacuum water vapour (5) therein, wherein the same tube (11) can be used as an outlet tube for water vapour (7); a second container (3), wherein an inlet tube (9) and an outlet tube (10) are mounted so that, during the adsorption, water (4) can be fed to the second container (3) through the inlet tube (9) and discharged through the out- let tube (10), and, during the regeneration, the supply of water (4) can be stopped, and high pressure steam (15) can be fed to the second container (3) through the inlet tube (9) and discharged through the outlet tube (10); wherein the first and second containers (1, 3) are arranged so that they have at least one common surface (19) through which heat can be transferred by heat conduction between said first container (1) and said second container (3).

21. A zeolite steam compressor (20) as claimed in claim 20, wherein the tube (11) connected to said first container is a T-tube with valves (6, 8) which are mounted so that, during the adsorption, the valve (6) with vacuum water vapour (5) can be opened, and the valve (8) for outlet vapour (7) can be closed and, during the desorption, the valve (6) with vacuum water vapour (5) can be closed, and the valve (8) for outlet vapour (7) can be opened.

22. A zeolite steam compressor (20) as claimed in claim 20 or 21, wherein the inlet tube and the outlet tube (9,10) of the second container (3) are both mounted with a 1-tube and valves (12, 14, 16, 18) so that, during the ad- sorption, water (4) can be fed to the second container (3) and discharged through the outlet tube (10), and, during the desorption, it is possible to reset the valves (12, 14, 16, 18) and thereby stop the supply of water (4) and, in- stead add high pressure steam (15)to the second container (3) 23. A zeolite steam compressor (20) as claimed in any one of claims to 22, wherein the tube (11) connected to said first container (1) is equipped with a manifold (27) for the distribution of the water vapour (5) in the first con- tainer (1).

24. A zeolite steam compressor (20) as claimed in any one of claims to 23, which comprises means for blocking solid material entering the first container (1) A zeolite steam compressor (20) as claimed in claim 24, wherein said means for blocking solid material comprise a demister, a filter, a sieve, or a combination thereof.

26. A zeolite steam compressor (20) substantially as described herein with reference to Figure 1 and/or Figure 2.

27. A process for producing steam from vacuum water vapour substantially as described herein with reference to Figures 4 and 5.