METHOD AND DEVICE FOR CONDITIONING OF A GAS

Abstract: Method and device for conditioning of a gas which passes through the treatment zone in a regenerative moisture exchanging apparatus (10, 16) for instance a rotor for exchanging moisture with an absorbing bed in the exchanging apparatus. In order to regenerate the bed, a regenerant gas, such as air, is passed through the exchanging apparatus in a further treatment zone which is separated from the first-mentioned zone. The regenerant air, is passed in a closed circuit (3-7) after the passage through the exchanger apparatus. The circuit comprises an evaporator (E) in a heat pump circuit by means of which the regenerant air is cooled and its moisture content is decreased. The regenerant air is then passed over a condenser (K) in the heat pump circuit by means of which the regenerant air is heated before being passed to the regenerating zone of the exchanger apparatus.

Description: Method and device for coπditioniπo cf a gas. Conventional sorption dehumidifiers are usually re¬ generated in a so-called open system, i.e. the regenerating air is taken from surrounding outside air and returned to the surroundings after it has passed the sorption mass and has driven the moisture out of it. It is often a disadvantage to need duct connection to the surroundings, and a so-called closed regeneration sys¬ tem is then selected, in which,after passage through the sorp¬ tion mass, the regenerating air is allowed to pass a cooler or condenser, in which this air is cooled so that the absorbed moisture is dispelled before the air is taken back to the sorp¬ tion mass via the heater, which is to give the regenerating air the correct high temperature for enabelling it to drive the moisture out of the mass. In its turn the condenser is then cooled by a secondary air stream from the dehumidified enclo¬ sure which is then in turn supplied with the heat taken from the regenerating air. This process is also burden with disadvantages. One such is that the energy requirements compared with the open system will be higher. In addition the amount of heat which is supplied to the dehumidified enclosure via the secondary air through the condenser gives the enclosure a temperature increas which can be troublesome. In certain cases when the dehumidifie enclosure, and thus also the cooling air supplied to the conden- ser, has a temperature lying below 0° C there is a risk that the condensate will freeze in the condensor, so that it will become blocked and no longer function. The object of the present invention is to remove the above-mentioned disadvantages, by lowering the energy require- ment considerably, by reducing the amount of heat transferred from the condensor to the dehumidified enclosure and by allow¬ ing condensation to take place at a temperature independent of the temperature in the dehumidified enclosure, this tempera¬ ture being sufficient high for preventing the condensate from freezing. This object is achieved in accordance with the inven¬ tion by the method and apparatus having been given the distingu¬ ishing features disclosed in the accompanying claims. The invention will now be described in more detail in connection with an embodiment example illustrated on the drawing, where Figure 1 schematically illustrates an embodiment of an appa¬ ratus for carrying out a method in accordance with the in¬ vention. Figure 2 illustrates in a psychrometric chart a dehumidifying and regenerating sequence in the method according to the invention. Figure 3 is another dehumidifying and regenerating sequence which can be carried out with the method and apparatus accor- ding to the invention. Figure 4 is a perspective view of a method of arranging dehumi¬ difying components in the sequence according to figure 3. It is assumed in the following that the gas which is to be treated in accordance with the invention is air which is t be dried (dehumidified) and also that the regenerating gas is air, although the invention is not restricted in these respects. Figure 1 solely illustrates the parts of the appara¬ tus which are vital for explaining the invention, while other parts such as casings, fans etc. are excluded. The sorption apparatus as illustrated in figure 1 is thus illustrated as essentially including a regenerative drying rotor containing a mass having the ability to absorb moisture. The rotor can be implemented conventionally, and comprise such as alternatingly flat and corrugated layers of suitable material, e.g. glass fibre "paper" with hygroscopic additives. The layers are reeled one upon the other to form a large number of axial ducts which are open towards the end surfaces of the rotor. A recovery apparatus 12 is also illustrated in Figure 1, and this apparatus can either be a temperature or a moisture exchanger. This recovery apparatus is not necessary for the function of the regeneration sequence, but lowers the energy requirements considerably, and is included in the sequences illustrated in figures 2 and 3 for this reason. In the sequen¬ ce according to figure 2, the recovery apparatus 12 is a tem¬ perature exchanger, and in the sequence according to figure 3 it is a moisture exchanger. By "moisture exchanger" is inten- ded here an apparatus of conventional kind, e.g. of the same kind as the drying rotor 10, which can transfer moisture from one air stream to another without notably changing the heat content of the air streams. In the apparatus illustrated in figure 1, outside air is caused by the state denoted by ' the point or numeral 1 to pass through the drying zone of the rotor 10 for dehumidi¬ fying the air, which is then given the state denoted by 2. As will be seen from the psychrometric charts in figure 2 and 3 the moisture content of the main air streams will de- crease simultaneously as the air temperature increases from the point 1 to the point 2. After the drying zone, the slowly rotating heat ex¬ changing mass of the rotor 10 comes into a regeneration zone, in which the absorbed moisture is removed with the aid of pre-heated regenerating air, which is in counterflow to the main air stream in the drying zone. In accordance with the invention a closed regene¬ ration circuit is used for treating the regenerating air and the necessary heating and cooling for the treatment of the regenerating air is achieved with the aid of a heat pump. In the heat pump circuit there is included the vaporizer E and the condenser K as well as remaining parts necessary for the function, such as compressor, valve system etc. (not illustrated) . In the embodiment according to figure 2 the regene¬ rating air leaving the regeneration zone of the rotor 10 in the state 6 after having been cooled from the state or point 5 before the rotor 10, i.e. from about 60° C to about 40° C (and thus having absorbed a corresponding moisture amount, as will be seen from the psychrometric chart in figure 2) is taken to a temperature exchanger 12 in the regeneration circuit. The temperature exchanger 12 is divided into two zones where 40-degree air from point 6 is cooled in a first zone to such as 20°C (point 7 in figure 2) by heat exchange with regenera¬ ting air which is cooled in a method which is described in the following. After the point 7 the regenerating air is allowed to pass over the outside of the vaporizer E which is connected in a heat pump circuit of conventional kind and which is therefore not described in any more detail. In the passage over the vaporizer E, the regenera- ting air will be cooled to the state at point 3, i.e. to about 10° C, simultaneously as the moisture removed from the rotor 10 is dispelled so that the moisture content of the regenerating air is reduced between the points 7 and 3 as will be apparent from figure 2. After the air has left the vaporizer E, it is taken into the second zone of the temperature exchanger 12 and is there heated to the state 4 by heat exchange with the 40-degree air at point 6 as mentioned above. The air temperature is thus raised from 10 C at point 3 to about 30 C at point 4, as will be seen from the chart in figure 2. With the aid of the schemati¬ cally illustrated fan or pump 14, which provides the move¬ ment in the regenerating air, the air is taken to the above- -mentioned condenser K in the heat pump circuit, the air tem¬ perature being raised from 30 C at point 4 to about 60 C at point 5 by heat exchange in the condenser, before the regenerating air is once again supplied to the drying zone of the drying rotor for dehumidifying the mass in the rotor 10. The temperature exchanger 12 can be of the regenera¬ tive type with a rotor as temperature transferring mass, but it can also be of the recuperative type with a stationary exchanger body. When the exchanger (recovery apparatus) 12 is a moisture exchanger, it can, as mentioned above, be of the same kind and have the same type of sorption mass and the same opera¬ tion as the rotor 10. It may then be advantageous to build the two units together into a common rotor, and this is what has been shown in the apparatus according to figure 4. Irrespec¬ tive of whether such building together of the moisture exchanging units takes place or not, the thermodynamic sequence will be the same, i.e. that depicted in the psychrometric chart in figure 3. This is therefore described with reference to the mechanical implementation illustrated in figure 4. In the embodiment of an apparatus for carrying out the method of the invention illustrated in figure 4, the parts in this figure have been given the same reference characters as like parts in the apparatus according to figure 1. The numeral 16 denotes a drying rotor which, as with the rotor 10 in figure 1, is used for dehumidifying a main air stream. In contradistinction to the embodiment in figure 1, a central part of the rotor 16 is separated from the remainder of it with the aid of suitable partition walls, which also divides this central part into two separate zones 18 and 20. The surfaces on the rotor against which these walls seal are illu¬ strated in the figure by the full lines dividing the rotor into corresponding zones. The central rotor part is used -for moisture exchange between the streams of regenerating air before and after it has passed over the outer surfaces of the vaporizer E and has been cooled by it. The sequence in ' . this embodiment is as follows: The main air stream is dried from the state 1 to the state 2 during passage through the drying zone of the drying rotor 16, as will be seen from the psychrometric chart in figure 3, and its temperature simul- taneously increases by about 8° C. The drying rotor mass is regenerated in the regeneration zone downwards in figure 4, preheated regenerated air in the state 5 being humidified to the state 6 simultaneously as it is cooled from about 50° C to about 34° C. The regarerating air is now led back again through the zone 18 in the central part of the rotor 16 and is there humidified further by moisture exchange between regenerating air which has passed the vaporizer E, as is described in the following. Simultaneously with the humidi- fication there is a further temperature drop from point 6 to point 1 , see figure 3. The air then passes the vaporizer E, through its lower and upper portion in the illustrated case, this vaporizer being included in a heat pump system described in connection with figure 1. During the passage through the vaporizer E there is cooling of the air and deposition of moisture so that the temperature falls and the moisture content decreases, as will be seen from figu- re 3. After passage through the vaporizer E, the air is taken through the zone 20 in the central part of the rotor 16, the moisture content further decreasing by moisture exchange with the air stream in the zone 18, which has been described above, simultaneously as the air temperature is raised between the points 3 and 4. Using a fan or pump 14 to maintain circulation in the closed regeneration circuit, the dehumidified and preheated air is supplied to the condenser K of the heat pump system, this condensor raising the tem¬ perature of the regenerating air from state 4 to the state 5, i.e. to about 50° C. In this state the air is taken once again to the regeneration zone of the drying rotor 16 for removing the moisture taken up by the mass in the rotor 16 in the drying zone. In both the described thermodynamic sequences according to figures 2 and 3, the final temperature of the air is about 10 C after passage past the vaporizer E. The vaporizing temperature in the vaporizer E is sufficient¬ ly high for the risk of freezing to be non-existent. Even though the point 1 were to be displaced towards colder tempera- tures, the vaporizing temperature remains at a level such that no freezing takes place. The closed regeneration circuit sequence has thus been made independent of ambient climate. The heat which is taken away in the vaporizer and which, in a conventional system, would be transferred to the dehumidified enclosure, now remains in the regeneration circuit and is utilized via the heat pump arrangement for regenera¬ ting the rotor. This results in a heavily lowered energy requirement, as well as avoiding an often undesired heating of the dehumidified enclosure. Lowing the energy requirement compared with a conventional closed regeneration system can be considerable, 3-5 times, when recovery in either of the given types will be utilized. The invention is, of course, not restricted to the illustrated and described embodiments, but can be varied within the scope of the concept forming its foundation, as defined in the following claims. Accordingly, the sorption apparatus 10 can be of the so-called stationary type, i.e. it can have a sorption mass in one or more stationary con¬ tainers, which are alternatingly regenerated and utilized for drying. It is also possible to use the described regene- rating method when contaminations other than water vapor are to be removed, e.g. paint solvents and the like.

Claims: CLAIMS 1. Method for conditioning a gas which is caused to pass through a treatment zone in a regenerative exchange appara¬ tus such as a rotor, for exchanging moisture with a sorption mass in the exchanger apparatus, the mass being regenerated by a regenerating gas, such as air, being caused to pass the exchanging apparatus in a further treatment zone which is se¬ parate from the first mentioned zone, c h a r a c t e r i z e d in that the regenerating air is taken into a closed sequence circuit in which, after passage through the exchanger apparatus, the regenerating air is led over the vaporizer in a heat pump circuit so that the regenerating air is cooled and its mois¬ ture content decreases, this air being subsequently led over a condenser in the heat pump circuit, whereby this air is heated before it is supplied to the further treatment zone of the exchanger apparatus. 2. Method as claimed in claim 1, c h a r a c t e r i z e d in that temperature or moisture is exchanged between the regenerating air streams before and after the passage over said vaporizer, with the aid of a recovery apparatus for obtaining the desired state of the regenerating air before it is supplied to the regenerating zone in the exchanger apparatus after said preheating in the condenser. 3. Method as claimed in claim 2, c h a r a c t e r i z e d in that the exchange between said regenerating air currents is a temperature exchange which lowers the temperature in the air streams to the vaporizer and raises the temperature in the air stream from the vaporizer. 4. Method as claimed in claim 2, c h a r a c t e r i z e d in that the exchange between said regenerating air currents is a moisture exchange which lowers the temperature and in¬ creases the moisture content in the air stream to the vapo¬ rizer and raises the temperature and lowers the moisture content in the air stream from the vaporizer. 5. Method as claimed in anyone of claims 2-4, c h a r a c t e¬ r i z e d in that a rotating exchanger is used for the exchange of temperature or moisture between the regenerating air current 6. Method as claimed in claim 2 or 3, c h a r a c t e r i z e d in that a stationary exchanger is used for exchanging tempera¬ tures between the regenerating air currents. 7. Apparatus for carrying out the method in accordance with any of the claims 1 to 6, for conditioning a gas passing through the treatment zone in a regenerative moisture exchan¬ ger apparatus (10, 16), such as a rotor, which also includes a regeneration zone in which a regenerating gas, such as air, passes for regenerating the moisture absorbing mass in the exchanger apparatus, c h a r a c t e r i z e d by a closed circuit sequence (3-7) for the regenerating air, said circuit including a heat pump circuit with a vaporizer (E) for cooling regenerating air and a condenser (K) for heating this air. 8. Apparatus as claimed in claim 7, c h a r a c t e r i z e d in that it includes an exchanger (12; 18, 20) with which tempe¬ rature or moisture is exchanged between flows of regenerating air to and from the vaporizer (E) . 9. Apparatus as claimed in claim 8, c h a r a c t e r i z e d in that said exchanger (18, 20) for the regenerating air streams is implemented in a central portion of the regenerative mois¬ ture exchanger apparatus (16) which has the form of a rotor, two zones (18, 20) being defined in the central part thereof for the flow of air to and from the vaporizer (E).

Inventors: NORBAECK PER, VON DOEBELN ERNST GUNNAR WILHE, NORBAECK, PER, VON DOEBELN, ERNST, GUNNAR, WILHELM
Applicants: MUNTERS AB CARL, AB CARL MUNTERS
Application year: 1988
Main classification: F24F3
IPC codes: F24F3