WO1998026221A1

WO1998026221A1 - Ambient air heating system

Info

Publication number: WO1998026221A1
Application number: PCT/GB1997/003393
Authority: WO
Inventors: Joe Knowles
Original assignee: AIRCOGEN Ltd
Current assignee: AIRCOGEN Ltd
Priority date: 1996-12-12
Filing date: 1997-12-09
Publication date: 1998-06-18
Anticipated expiration: 1999-06-12
Also published as: ZA9711165B; GB9625799D0; AU7849398A

Abstract

A system (10) for providing electrical power and heating for an industrial process comprises a housing (24) having an air inlet (26) for external air and an air outlet (28) for connection to an industrial process. The housing contains a generating system (12) for generating electrical power, and means for drawing air (30) from the air inlet (26) to the air outlet (28) past the generating system (12) so that the air is heated by waste heat from the generating system (12). The system additionally has heat transfer means (14) for transferring heat from the generating system (12) externally of the housing (24). This reduces the amount of heat available for transfer to the air drawn past the generating system (12) so that the temperature of air exiting through the air outlet (28) can be controlled.

Description

Title: Ambient Air Heating System

The present invention relates to a combined heat and power system for generating electrical power and heat for an industrial process.

Accordingly, the present invention provides a system for providing electrical power and heating for an industrial process, comprising:

a housing having:

an air inlet for the inlet of external air and an air outlet for connection to an industrial process;

wherein the housing contains:

a generating system for generating electrical power;

means for drawing air from said housing air inlet to said housing air outlet past said generating system whereby said air is heated by waste heat from said generating system;

and heat transfer means for transferring heat from said generating system externally of said housing;

and control means for controlling said heat transfer means for adjusting the temperature of air exiting through said air outlet.

In a preferred form of the invention, an exhaust system of said generating system has a mixing device for mixing exhaust gases with the said air flowing past said generating system, and control means are provided in the exhaust system upstream of the mixing means for exhausting exhaust gases to atmosphere, the control means being adjustable to vary the amount of exhaust gases passed to the mixing means.

In a further form of the invention an exhaust system of the generating system has heat exchanger means for transferring heat from exhaust gases to the air passing through the housing, and the exhaust system has control means upstream of the heat exchanger means for exhausting exhaust gases to atmosphere, the control means being adjustable to control the amount of exhaust gases passed to the heat exchanger means.

In some embodiments , the temperature of air leaving the outlet can be controlled by the export of heat from a heat exchanger as hot water.

The system also allows fine control of the process air temperature over a wide range of operation.

The present invention is further described hereinafter, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a schematic diagram of a preferred form of combined heat and power system according to the present invention; and

Figure 2 shows a modification to the system of Figure 1 ; and

Figure 3 shows a further modification to the system of Figure 1.

Referring firstly to Figure 1, this shows a combined heat and power system 10 which has a power generating system 12 providing electrical power for an industrial process such as a rotary kiln, whilst providing hot process air for the industrial process. The power generating system 12 may conveniently be a combustion engine and generator or a combustion turbine and generator or a fuel cell. Heat transfer means in the form of a fluid circuit 14 is used to cool the generating system 12. The fluid circuit 14 uses water as a coolant (or any other suitable thermal fluid such as oil) which is pumped round the circuit, through heat exchangers 16 and 18, by a pump 20. The heat exchanger 16 transfers heat to a low pressure hot water system 22 whilst the heat exchanger 18 transfers heat to the surrounding air. The heat exchanger 16 is coupled to the heat exchanger 18 by a valve 19 which also connects with a bypass 21 in parallel with the heat exchanger 18. The valve 19 controls the flow of fluid from the heat exchanger 16 to the heat exchanger 18 and bypass 21 and can be used to divert a portion of the fluid into the bypass 21 in order to reduce the heat transferred by the heat exchanger 18 to the surrounding air.

An alternative or additional bypass 23 can be provided to bypass both the heat exchanger 16 and the heat exchanger 18 and a further bypass 25 bypassing the heat exchanger 16 can also be provided. The bypasses 23, 25 can be controlled by suitable valves 27, 31 in the same manner as the bypass 21. The bypasses can be provided in any combination with any one or any two or any three being provided.

The power generating system 12 and the fluid circuit 14 are contained within a housing 24 which has an inlet 26 at one end and an outlet 28 at the other.

Cool air is drawn in through the inlet 26 and through a filter 29 by one or more fans 30 positioned between the inlet 26 and the power generating system 12 and fluid circuit 14. The fans 30 may be variable speed fans. The air drawn in by the fan 30 is normally atmospheric air and is passed around the power generating system 12 and the fluid circuit 14, collecting heat from all the available surfaces and from the heat exchanger 18.

Exhaust gases from the power generating system 12 are passed through an exhaust system 32 which includes a sound damping means in the form of a sound attenuator 34. A particle collection or filtration system may also be included in the exhaust system, where required. After passing through the sound attenuator 34 the exhaust gases are mixed with the air passing through the housing in a mixing means or device 36. The resulting combined atmospheric and exhaust gases then pass through the air outlet 28. A control valve 38 is positioned in the exhaust system upstream of the mixing device 36 and controls the amount of exhaust gases passed to the mixing device 36, unwanted exhaust gases being exhausted to atmosphere through an outlet 40.

Obviously, the mixing of exhaust gases with the air drawn through the housing by the fan 30 can only take place where contamination of the air is of no consequence. Where the atmospheric air must not be contaminated with exhaust gases then the mixing device 36 is replaced by a heat exchanger 42 (Figure 2) which transfers heat from the exhaust gases to the atmospheric air drawn through the housing 24.

The heat exchanger 42 may be a condensing heat exchanger where appropriate.

After passing through the heat exchanger 42 the exhaust gases are exhausted to atmosphere.

Figure 3 shows a further modification of the system of Figure 1. Like parts are given like reference numbers.

In the system of Figure 3 a boost heater means 50, preferably in the form of a gas burner, is provided in the housing 24 downstream of the mixing device 36, between the mixing device 36 and the outlet 28 and a second outlet 52.

A filter 54 is also provided in the housing 24 between the exhaust gas mixing device 36 and the boost heater 50.

The boost heater 50 serves to increase the temperature of the passing air to provide an increased flexibility. The second outlet 52 is formed in the side of the housing 24 and allows the hot air to be exhausted to atmosphere. The outlet 52 is controlled by damper means 56 which control the amount of air exhausted through the second outlet 52.

A further damper means 58 is provided in the outlet 28 to enable control of the amount of air passing through the outlet 28.

The damper means 56 and 58 may be formed by baffle plates which can be rotated between closed and open positions to vary the degree of opening of the outlets.

The provision of the damper means allows operation of the system for generation of electrical power by the generating system 12 when no hot air is required by the industrial process, for example when maintenance of the industrial process (e.g. a rotary kiln) is required. The baffle plates 58 can be closed whilst the baffle plates 52 opened to dump the hot air to atmosphere.

In conjunction with the variable speed fan or fans 30 the damper means 56, 58 and the boost heater 50 allow fine control of the process air temperature over a wide range.

The systems described above with reference to Figures 1 to 3 provide energy production for an industrial process which is more efficient, more flexible and environmentally acceptable. Under full load conditions, all of the input energy can be utilised effectively where the products of combustion can be tolerated by the process. Where these must be segregated, efficiencies of 90% to 95% are achievable.

Each of the above-described systems applies all or some of the waste heat of power generation to heat or preheat a flow of ambient air which may be used in an industrial process, for example in automotive industry vehicle paint booths, rotary kilns and flash powder drying. The temperature of air leaving the outlet 28 can be controlled closely in order to vary precisely the amount of heat used in the subsequent industrial process. Each of the systems illustrated in the drawings achieves this in several stages. One stage is the export of heat from the heat exchanger 16 as hot water for use in supplementing or replacing other hot water heating sources, or for rej ection to atmosphere via an external heat exchanger. Another stage is the direct exhausting to atmosphere of unwanted exhaust heat which is accomplished via the valve 38. At this stage, up to 90% of the heat has been drawn from the system.

It will be appreciated by those skilled in the art that any of the features of the above- described embodiments may be interchanged as desired.

Claims

1. A system for providing electrical power and heating for an industrial process, comprising:

a housing (24) having:

an air inlet (26) for the inlet of external air and an air outlet (28) for connection to an industrial process;

wherein the housing (24) contains:

a generating system (12) for generating electrical power;

means (30) for drawing air from said housing air inlet (26) to said housing air outlet (28) past said generating system (12) whereby said air is heated by waste heat from said generating system;

and heat transfer means (38, 40; 16; 52, 56) for transferring heat from said generating system (12) externally of said housing (24) ;

and control means (60; 23, 27; 25, 31, 38, 40; 52, 56; 58) for controlling said heat transfer means for adjusting the temperature of air exiting through said air outlet.

2. A system as claimed in claim 1 wherein said heat transfer means (38, 40; 16) is operable to reduce the amount of heat available for transfer to said air drawn past said generating system.

3. A system as claimed in claim lor 2 wherein said generating system (12) has an exhaust system which has a mixing means (36) for mixing exhaust gases with the said air flowing past said generating system;

and control means (38) are provided in the exhaust system upstream of the mixing means (36) for exhausting exhaust gases to atmosphere, the control means being adjustable to vary the amount of exhaust gases passed to the mixing means.

4. A system as claimed in claim 1 , 2 or 3 wherein the generating system exhaust system has heat exchanger means (42) for transferring heat from exhaust gases to the air passing through the housing (24);

and wherein the exhaust system has control means (38) upstream of the heat exchanger means (42) for exhausting exhaust gases to atmosphere, the control means being adjustable to control the amount of exhaust gases passed to the heat exchanger means.

5. A system as claimed in claim 3 or 4 wherein said exhaust system has a sound attenuator.

6. A system as claimed in any of the preceding claims wherein said generating system (12) has a fluid circuit (14) for cooling said generating system.

7. A system as claimed in claim 6 wherein said heat transfer means comprises said fluid circuit (14) and a heat exchanger (16) in said fluid circuit for transferring heat externally of said housing (24).

8. A system as claimed in claim 7 wherein said heat exchanger (16) transfers heat to a low pressure hot water system (22).

9. A system as claimed in claim 6 wherein said fluid circuit (14) has a heat exchanger (18) for transferring heat from said generating system to said air from said housing air inlet (26).

10. A system as claimed in claim 9 wherein said fluid circuit (14) has a bypass (19) for bypassing said heat exchanger (18) and control means (19) for controlling the flow of coolant through said heat exchanger (18) and said bypass (19).

11. A system as claimed in any of the preceding claims wherein said means (30) for drawing air from said housing air inlet (26) to said housing air outlet (28) comprises at least one fan.

12. A system as claimed in claim 11 wherein the speed of said at least one fan is variable.

13. A system as claimed in any of the preceding claims further comprising boost heater means (50) in said housing (24) for boosting the temperature of said air in the housing.

14. A system as claimed in claim 12 wherein said boost heater means (50) is positioned in said housing (24) downstream of said generating system (12).

15. A system as claimed in claim 13 or 14 wherein said boost heater means (50) is a gas burner.

16. A system as claimed in any of the preceding claims wherein said air outlet (28) has damper means (58) for controlling the flow of air through said outlet.

17. A system as claimed in any of the preceding claims further comprising a second outlet (52) connecting said housing (24) with atmosphere for enabling the dumping of hot air from said housing to atmosphere.

18. A system as claimed in claim 17 wherein said second outlet (52) has damper means (56) for controlling the passage of air therethrough.

19. A system as claimed in any of claims 16 to 18 wherein said damper means (56, 58) comprises a plurality of baffle plates adjustable between a fully closed position wherein said air outlet (52, 28) is fully closed and a fully open position wherein said air outlet is fully open.