GB2032089A - Condenser apparatus - Google Patents

Abstract

A gas condenser apparatus is described employing two heat exchanger stages 10 and 12 for condensing water vapour and other containments, such as organic solvents, out of hot air or other treated gas by means of a cooling gas which is provided by feeding back the treated gas through the cooling passages 44 of such heat exchanger stages after removal of the water and solvents. The heat exchangers are of the counterflow type so that the treated gas and the cooling gas flow in opposite directions therethrough. Preferably, water vapour is removed from the treated gas by condensing it in the first stage 10 and the solvents are removed by condensing them in the second stage 12 thereby separating the condensed water and solvents. Auxiliary cooling coils 28, 38 are provided at the input of the first stage and at the output of the second stage for further cooling of the treated gas. A temperature sensor 22 at the output of the first stage controls the input cooling coil 28 in order to maintain the temperature of the treated gas at the output of the first stage above the freezing temperature of water. <IMAGE>

Description

SPECIFICATION Condenser Apparatus This invention relates generally to gas condenser apparatus employing heat exchangers having cooling gas passages to condense water and other containments such as organic solvents from the treated gas.

According to the invention, there is provided condenser apparatus including: first heat exchanger means for cooling input gas flowing through first passages in said first heat exchanger means, by causing cooling gas to flow through cooling passages separated by heat exchanger members from said first passages to provide a cooled gas: second heat exchanger means for condensing other material out of the cooled gas flowing through second passages in said second condenser means connected to the output of said first passages after water vapour has been condensed out of said input gas, by causing cooling gas to flow through cooling passages separated by heat exchanger members from said second passages which cools the second passages to a lower temperature than that of the first passages; cooling gas means for providing the treated gas supplied from the output of said second passages of said second heat exhanger means with a temperature below the condensation temperature of said other material to form the cooling gas; and feedback means for transmitting said cooling gas through the cooling passages of said second heat exchanger means and said first heat exchanger means in the order named.

Preferably, the treated gas is cooled sufficiently in the first stage to condense water vapour out of the gas in such first stage while the treated gas is further cooled in the second stage to condense the solvents. This separates the condensed water and solvents, enabling the solvents to be reused more readily.

Previously, it has been known to use counterflow type heat exchangers as condensers.

However, the cooling fluid has been a separate gas or liquid from the gas being cooled, as shown in U.S. Patent 3,827,343 or W.J. Darm, granted August 6, 1974, U.S. Patent 3,232,029 of W.R.

Evans, Jr., granted February 1, 1966 and U.S.

Patent 2,169,054 of J.J. Mojonnier, granted August 8, 1939. The second patent is not a counterflow heat exchanger and while it employs two heat exchanger stages, the second stage is a heater, not a condenser. Also, in none of these patents is the cooling fluid provided by feeding back the gas being treated after condensation of water vapour or solvent from such gas. As a result, the condensers of these patents are not as efficient as that of the present invention.

British Patent Specification No. 711 ,067 of Guinot, granted June 23, 1 954, shows a condenser system employing two heat exchanger stages for cooling. However, the second stage is employed for cooling the cooling liquid used in the first stage. In addition, this cooling liquid is separate from the treated gas which is condensed 'in the first state. Therefore, the present invention differs in several respects for this patent.

Furthermore, in none of the above discussed patents is the water condensed in one heat exchanger stage while the solvents are condensed in a second heat exchanger stage to separate the condensed water and solvent.

In order that the invention may be readily understood, an embodiment thereof will now be described, by way of example, with reference to the accompanying drawings, in which: FIGURE 1 is a schematic diagram showing one embodiment of the condenser apparatus of the present invention; and FIGURE 2 is a perspective view of a portion of the heat exchanger used in the apparatus of Figure 1.

As shown in Figure 1, a condenser apparatus embodying the present invention includes input heat exchanger stage 10 and an output heat exchanger stage 12 which may be of the counterflow type shown in U.S. Patent 3,912,004.

Each heat exchanger contains a first set of passages for the treated gas and a second set of passages for the cooling gas separated by heat exchanger plates, as hereafter discussed with reference to Figure 2. An input conduit 14 for transmitting hot air or other gas to be treated, is connected to the input of the first set of passages of heat exchanger 10. A connection conduit 16 is connected from the output of the first set of passages of heat exchanger 10 to the input of the first set of passages of heat exchanger 12 so that treated air is transmitted along paths 17 through both heat exchangers. Cooling gas is transmitted in the opposite direction through the second set of passages of heat exchangers 10 and 12 in order to cool the hot gas being treated.The treated gas is cooled to a lower temperature, typically about 320F at the output of such heat exchanger when it enters the connection conduit 1 6. As a result, water vapour present in the treated gas transmitted through input conduit 14 is condensed in the input heat exchanger stage 10.

The condensed moisture flows down the heat exchanger plates and is removed from such input stage through drain 20 at the output end of the first set of passages.

In order to prevent the condensed water from freezing in the heat exchanger 10, a temperature sensor 22 is provided in the connection conduit 16 and is connected electrically or pneumatically to a controller 24 which automatically controls a compressor 26 connected to a cooling coil 28 provided at the input of the heat exchanger 1 0 within conduit 14. This cooling coil is a conventional closed refrigeration coil which may be filled with gas refrigerant.Thus, the temperature sensor 22 measures the temperature of the cooled gas after it leaves the heat exchanger 10 and as such temperature reaches 320 F, the sensor 22 operates the controller 24 to cause the auxiliary cooling coil 28 to perform less cooling of the input gas, thereby maintaining the temperature of the cooled gas at the output of the heat exchanger above 320F, or other predetermined temperature at which frost forms or the condensed water freezes in such heat exchanger.In one typical example, when the hot air or treated gas in input confuit 14 is at a temperature of approximately +1 500 F, the cooling coil 28 is provided with a suction temperature of about +900 F, thereby cooling the treated gas to approximately + 1000 F to + 1 250F before it enters the heat exchanger 10 and maintaining such treated gas at an output temperature of about 320 F.

The second heat exchanger stage 12 further cools the treated gas from +320F to about -300F and causes organic solvents to condense out in such heat exchanger. The condensed solvents are drained from the first passages in exchanger 12 through drain 30 at the output end thereof. An output conduit 34 is connected from the output of the first passages in heat exchanger 12 to the inlet of a fan 36. The treated gas flowing through conduit 34 is further cooled by a second cooling coil 38 of similar type to that of coil 28 provided at the outlet of conduit 34.The low temperature cooling coil 38 is connected to another refrigerating apparatus 40 providing a suction temperature of about 600 F. As a result, the treated gas is cooled and transmitted from the output of the fan 36 at a temperature of about --500F. It should be noted that some additional condensation may occur in the conduit 34 so that a drain may be provided in such conduit between cooling coil 38 and fan 36.

A feedback conduit 42 is connected from the output of the fan 36 to the input of the second set of passages of the second heat exchanger 12, such second passages transmitting cooling fluid through the heat exchangers in opposite direction to the treated gas, as shown by the dashed line path 44 of the cooling gas through such second passages. Thus, the treated gas after it has been cooled, condensed and transmitted from the output of the second heat exchanger stage 12 is further cooled by cooling coil 38 and then fed back through the heat exchangers 12 and 10 in the order named, as the cooling gas of such heat exchangers. The temperature of the gas at the output of conduit 34 is not sufficiently low so that it can be used as a cooling gas without further cooling.Therefore, the cooling coil 38 is necessary to further cool the gas before it can be employed as the cooling gas of the heat exchangers.

A second connection conduit 45 is connected from the output of the second passages of the second heat exchanger stage 12 to the input of the second passages of the first heat exchanger stage 10 to supply cooling gas to the first stage.

This cooling gas flows in opposite direction to the treated gas flowing in stage 10 along path 17, as shown by the dashed line arrow 44 indicating the path of such cooling gas. The cooling gas is transmitted through a cooling gas outlet conduit 46 connected to the output of the cooling passages of stage 10 at a temperature which, for example given, is typically about + 1300 F. Thus, the temperature difference between the treated gas supplied to input conduit 14 and the cooling gas discharged through the outlet conduit 46 is only about 200 F. As a result, very little energy is consumed by the condenser apparatus embodying the present invention. This high efficiency is due in part to the feedback of treated gas through the cooling passages of both stages 10 and 12.In the example given, with an air flow through conduits 14, 16, 32, 42 and 44 of about 1900 cubic feet per minute, the compressors 26 and 40 may each by typically of a ten ton capacity. It should be noted that the controller 24 loads and unloads the compressor 26 in response to the temperature signal emitted by sensor 22 to vary the cooling effect of the cooling coil 28.

In the embodiment described, the drain 30 drains the solvent from stage 12 into a settling tank from where it can be removed off the top of the liquid in such tank while any small amount of water which might accumulate in the tank is drained from the bottom thereof. Thus, the solvents can be reused or they can be fed to a fractional distilling apparatus to separate the solvents into their basic components before reuse.

However, in some cases the solvents are not of sufficient value for reuse. In those cases it is not important to separate them from the water.

Therefore, the water and the solvent can both be condensed in the second heat exchanger unit 12 and drained through drain 30 to a suitable storage tank before being thrown away. In this latter case, the condenser apparatus of the present invention would normally be used in a manner to eliminate air pollution contaminants and thereby satisfy Environmental Protection Agency requirements, such as by being connected to the output stack of a wood venner dryer. In addition, rather than employing the auxiliary cooling coil 28, compressor 26, controller 24 and temperature sensor 22 to maintain the temperature of the gas above freezing, it is possible to eliminate these elements and simply provide an automatic shutdown of the condenser for a predetermined period in each eight hour shift to defrost the heat exchangers.

While other flow through type heat exchangers can be employed for the heat exchanger stages 10 and 12 in the condenser apparatus of the present invention, the split ended type heat exchanger 48 shown in Figure 2, described in U.S. Patent 3,912,004, is preferable. In this heat exchanger the opposite ends of the heat exchanger plates 50, 52, 54, 56 and 58 are split into two end portions which are joined to different ones of the end portions of the two heat exchanger plates on the opposite sides thereof. Thus, split end portion 58A is connected to split end portion 56A, while split end portion 56B is connected to split end portion 54B by means of riveted connecting member 60.

The split ends of the heat exchanger plates are separated by a divider plate 62 which are sealed to such heat exchanger plates by epoxy resin or other suitable airtight sealing material to provide a first set of passages 64 through which the treated gas flows, and a second set of passages 66 through which the cooling gas flows. This is a counterflow type heat exchanger so the treated gas in passages 64 and the cooling gas in passages 66 flow in opposite directions on opposite sides of the heat exchanger plates.

Spacer clips 68 may be provided across the top and bottom edges of the heat exchanger plates to hold them in spaced relationship, or spacer bumps may be provided on the surfaces of the heat exchanger plates for engaging plates on opposite sides thereof to maintain predetermined spaced relationship between the plates, as discussed in U.S. Patent 3,912,004. It should be noted that the housing for the heat exchanger has been removed in Figure 2 and would be bonded to the top and bottom edges of the heat exchanger plates by synthetic plastic material to seal the sides of the passages 64 and 66.

Claims (12)

1. Condenser apparatus including: first heat #exchanger means for cooling input gas flowing through first passages in said first heat exchanger means, by causing cooling gas to flow through cooling passages separated by heat exchanger members from said first passages to provide a cooled gas; second heat exchanger means for condensing other material out of the cooled gas flowing through second passages in said second condenser means connected to the output of said first passages after water vapour has been condensed out of said input gas, by causing cooling gas to flow through cooling passages separated by heat exchanger members from said second passages which cools the second passages to a lower temperature than that of the first passages; cooling gas means for providing the treated gas supplied from the output of said second passages of said second heat exchanger means with a temperature below the condensation temperature of said other material to form the cooling gas: and feedback means for transmitting said cooling gas through the cooling passages of said second heat exchanger means and said first heat exchanger means in the order named.

2. Condenser apparatus according to claim 1, in which the first heat exchanger condenses water vapour out of the input gas before it is supplied to the second heat exchanger, and which includes drain means for removing the condensed water and the other condensed material from the first and second heat exchanger means.

3. Condenser apparatus according to claim 1 or 2 in which the cooling gas means includes a cooling coil provided between the output of the second passages of the second heat exchanger means and the input of the feedback means.

4. Condenser apparatus according to any one of claims 1 to 3, which also includes a temperature regulation means for maintaining the temperature in said first passage of the first heat exchanger above the freezing temperature of water.

5. Condenser apparatus according to claim 4, in which the temperature regulation means includes a temperature sensor connected to the output of said first passages and a closed refrigeration system connected to said sensor and having a cooling coil positioned at the input of said first passages for cooling said input gas by an amount depending on the temperature detected by said sensor.

6. Condenser apparatus according to any preceding claim, which also includes flow means for moving said input gas, said cooled gas and cooling gas through said condensers.

7. Condenser apparatus according to claim 6, in which said flow means is a fan connected between the output of said second passages and the input of the cooling passages in said second condenser.

8. Condenser apparatus according to any preceding claim, in which the first and second heat exchanger means are counterflow heat exchangers in which the cooling gas flows in a general opposite direction to the gas on the other side of the heat exchanger members.

9. Condenser apparatus according to claim 8, in which the heat exchangers include heat exchanger plates whose opposite ends are split into two end portions which are connected to other heat exchanger plates on the opposite sides thereof and two divider members extend through the split end portions at the opposite ends of said plates to form two sets of passages on the opposite sides of said plates.

10. Condenser apparatus according to claim 8, or 9, in which the heat exchangers are supported so that said first and second passages extend in substantially a horizontal direction.

11. Condenser apparatus substantially as hereinbefore described with reference to the accompanying drawings.

12. Any novel feature or combination of features herein described.