A HYBRID HOMOGENOUS-CATALYTIC COMBUSTION SYSTEM

Abstract

The present invention relates to a hybrid combustion system (1) wherein rich homogeneous combustion and lean catalytic combustion are carried out consecutively, which results in zero NO.sub.x emission and is used for obtaining domestic hot water. The present invention relates to a combustion system wherein two serially connected heat exchangers units, which are located in the outlets of the rich homogeneous combustion unit and the lean catalytic combustion unit, transfers the heat generated during combustion reactions into domestic radiator heating water and/or tap water for hot water generation.

Claims

1. A combustion system essentially comprising: a body; a surface-type burner which is located on a lower part of the body where a rich fuel air mixture is burnt; an ignition electrode which ignites the rich fuel air mixture; a fuel valve whereby natural gas required for the surface-type burner is given; a compressor (or fan) whereby air required for the surface-type burner is provided; an air valve which is located downstream of the compressor; wherein a primary heat exchanger, where exhaust gases, which are-generated as a result of a combustion occurring in the surface-type burner, enter and heat water passing through; a pump to pressurize the water passing through the primary heat exchanger; a heat exchanger valve which is located in front of the primary heat exchanger and a flow meter (rotameter, etc.) which measures water flow; a tubular secondary heat exchanger which is positioned on an upper part of the primary heat exchanger, passing through a jacket part of the tubular secondary heat exchanger, thereby heating secondary air pumped for the combustion through the tubular secondary heat exchanger; a secondary heat exchanger air valve which controls the air passing through the secondary heat exchanger; a gas distributor plate which is located on an upper part of the secondary heat exchanger and generates poor gas mixture by mixing the exhaust gases and the air exiting the secondary heat exchanger; a moisture trap where the poor gas mixture exiting the gas distributor plate enters; a catalytic burner which is located on an upper part of the moisture trap wherein a flameless combustion occurs; a tertiary heat exchanger where gas leaving the catalytic burner is released to atmosphere by passing through a jacket part and water exiting the primary heat exchanger passes through and heated for the last time before leaving the system; a gas outlet exhaust pipe where the gas leaves the body.

2. The combustion system according to claim 1, wherein an ionization electrode controls a presence of a flame in the surface-type burner continuously.

3. The combustion system according to claim 1, wherein a thermocouple a measures the flame temperature on the surface-type burner.

4. The combustion system according to claim 2, wherein a control unit triggers the ignition electrode in order to ignite the rich fuel air mixture in the surface-type burner.

5. The combustion system according to claim 1, wherein in the surface-type burner, a rich natural gas-air mixture is generated by means of the fuel valve and the air valve and the rich natural gas-air mixture is ignited by means of the ignition electrode.

6. A The combustion system according to claim 1, wherein a pipe line is provided in order to deliver the water between the primary heat exchanger and the tertiary heat exchanger.

7. The combustion system according to claim 1, wherein the gas distributor plate does not entirely extend inside the body from an end to an other end therefore forming an opening wherein the poor gas mixture can pass throughout the body.

8. A The combustion system according to claim 1, wherein the gas distributor plate has a hollow structure.

9. The combustion system according to claim 1, wherein in the moisture trap, the poor gas mixture passes both during start-up and normal operation of the combustion system.

10. The combustion system according to claim 2, wherein a thermocouple measures the flame temperature on the surface-type burner.

11. The combustion system according to claim 2, wherein in the surface-type burner, a rich natural gas-air mixture is generated by means of the fuel valve and the air valve and the rich natural gas-air mixture is ignited by means of the ignition electrode.

12. The combustion system according to claim 3, wherein in the surface-type burner, a rich natural gas-air mixture is generated by means of the fuel valve and the air valve and the rich natural gas-air mixture is ignited by means of the ignition electrode.

13. The combustion system according to claim 2, wherein a pipe line is provided in order to deliver the water between the primary heat exchanger and the tertiary heat exchanger.

14. The combustion system according to claim 3, wherein a pipe line is provided in order to deliver the water between the primary heat exchanger and the tertiary heat exchanger.

15. The combustion system according to claim 2, wherein the gas distributor plate does not entirely extend inside the body from an end to an other end therefore forming an opening wherein the poor gas mixture can pass throughout the body.

16. The combustion system according to claim 3, wherein the gas distributor plate does not entirely extend inside the body from an end to an other end therefore forming an opening wherein the poor gas mixture can pass throughout the body.

17. The combustion system according to claim 2, wherein the gas distributor plate has a hollow structure.

18. The combustion system according to claim 3, wherein the gas distributor plate has a hollow structure.

19. The combustion system according to claim 2, wherein in the moisture trap, the poor gas mixture passes both during start-up and normal operation of the combustion system.

20. The combustion system according to claim 3, wherein in the moisture trap, the poor gas mixture passes both during start-up and normal operation of the combustion system.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0028] FIG. 1 is a schematic view of the inventive hybrid homogenous-catalytic combustion system.

[0029] The components illustrated in the figures are individually numbered, where the numbers refer to the following: [0030] 1. Combustion system [0031] 2. Body [0032] 3. Surface-type burner [0033] 4. Electrode [0034] 5. Fuel valve [0035] 6. Compressor [0036] 7. Air valve [0037] 8. Primary heat exchanger [0038] 9. Pump [0039] 10. Heat exchanger valve [0040] 11. Flow meter [0041] 12. Secondary heat exchanger [0042] 13. Secondary heat exchanger air valve [0043] 14. Gas distributor plate [0044] 15. Moisture trap [0045] 16. Catalytic burner [0046] 17. Tertiary heat exchanger [0047] 18. Exhaust pipe [0048] 19. Ionization electrode [0049] 20. Thermocouple [0050] 21. Control unit [0051] 22. Pipe line

DETAILED DESCRIPTION OF THE INVENTION

[0052] A Hybrid Homogenous-Catalytic Combustion System realized to fulfil the objectives of the present invention is illustrated in the accompanying figures, in which:

[0053] The inventive hybrid homogenous-catalytic combustion system (1) essentially comprises: [0054] at least one body (2); [0055] at least one surface-type burner (3) which is located on the lower part of the body (2) and wherein the rich fuel air mixture is burnt; [0056] at least one electrode (4) which ignites the fuel air mixture; [0057] at least one fuel valve (5) whereby the natural gas required for the surface-type burner (3) is given; [0058] at least one compressor (or fan) (6) whereby the air required for the surface-type burner (3) is provided; [0059] at least one air valve (7) which is located upstream of the compressor (6); [0060] at least one tubular primary heat exchanger (8) where the exhaust gases, which are generated as a result of the combustion occurring in the surface-type burner (3), enter and the heating water passes through; [0061] at least one pump (9) to pressurize the water passing through the primary heat exchanger (8); [0062] at least one heat exchanger valve (10) which is located in front of the primary heat exchanger (8) and at least one flow meter (rotameter, etc.) (11) which measures the water flow; [0063] at least one tubular secondary heat exchanger 12) which is positioned on the upper part of the primary heat exchanger (8), where the exhaust gases exiting the primary heat exchanger (8) passes from the heating jacket and the air pumped for combustion passes through thereof by being heated; [0064] at least one secondary heat exchanger air valve (13) which controls the air passing through the secondary heat exchanger (12); [0065] at least one gas distributor plate (14) which is located on the upper part of the secondary heat exchanger (12) and generates the poor gas mixture by mixing the exhaust gas and the air exiting the secondary heat exchanger (12) [0066] at least one moisture trap (15) where the poor gas mixture exiting the gas distributor plate (14) enters; [0067] at least one catalytic burner (16) which is located on the upper part of the moisture trap (15) and wherein flameless combustion occurs; [0068] at least one tertiary heat exchanger (17) where the gas leaving the catalytic burner (16) is released to the atmosphere by passing through the jacket part and the water exiting the primary heat exchanger (8) passes through for the last time before leaving the system; and [0069] at least one gas outlet exhaust pipe (18) where the gas leaves the body (2).

[0070] The inventive combustion system (1) also comprises at least one ionization electrode (19) which controls presence of flame in the surface-type burner (3) continuously. Apart from this, the combustion system (1) comprises at least one thermocouple (20) which measures the flame temperature on the surface-type burner (3). The system (1) also comprises at least one control unit (21) which triggers the ignition electrode (4) in order to ignite the rich fuel-air mixture in the surface-type burner (3).

[0071] In a preferred embodiment of the invention, combustion occurs in the surface-type burner (3) at lambda values under stoichiometric conditions. In the said burner (3), rich natural gas-air mixture is generated by means of the fuel valve (5) and the air valve (7) and it is ignited by means of the ignition electrodes (4). In the surface-type burner (3), a rich combustion is realized in the range of stoichiometric combustion wherein lambda is 1 and rich combustion wherein lambda is 0.6. A gas mixture having a content of minimum 4% carbon monoxide and 4% hydrogen in volume is obtained as a result of the homogenous rich combustion (partial oxidation) occurring in the surface-type burner (3).

[0072] In the inventive combustion system (1), there is a pipe line (22) which is provided in order to deliver the water between the primary heat exchanger (8) and the tertiary heat exchanger (17). Thus, the water heated by the surface-type burner (3) in the primary heat exchanger (8) is delivered to the tertiary heat exchanger (17) to realize further heating by means of the catalytic burner (16). In a preferred embodiment, while the water passes through the pipes of the primary and tertiary heat exchangers (8, 17), the air generating the poor gas mixture is supplied to the catalytic burner (16) from the secondary heat exchanger (12) by being mixed with the exhaust gas.

[0073] In the invention, the water flow heated by the combustion gases in the primary and tertiary heat exchangers (8, 17) is used as domestic heating water. A thermal load of 5 kW.sub.t to 20 kW.sub.t is transferred to the said water in the primary heat exchanger (8).

[0074] In a preferred embodiment of the invention, the gas distributor plate (14) does not entirely extend inside the body (2) from one end to the other end and form an opening wherein the gas mixture can pass (2). In addition, the said plate (14) has a hollow structure. Thus, the gas mixture reaches the moisture trap (15) easily from both the holes and the aperture and proceeds to catalytic burner (16) through here. The gas mixture reaching the catalytic burner (16) contains hydrogen and carbon monoxide (H.sub.2CO) generated as a result of rich combustion in the surface-type burner (3). The exhaust gas of the catalytic burner composed of carbon dioxide, oxygen and nitrogen as a result of flameless combustion occurring in the catalytic burner (16). The achieved temperature of the gas with poor fuel content through the gas distributor plate (14), is the minimum temperature required for initiation of catalytic reaction.

[0075] In a preferred embodiment of the invention, the gas mixture passes through the moisture trap (15) both during the start-up and normal operation of the system (1). The moisture trap (15) captures the water condensing during the start-up of the system (1). Whereas during continuous operation, the moisture kept by the ambient temperature vaporizes and becomes regenerated.

[0076] The gas mixture, which is burned by means of flameless combustion in the catalytic burner (16), gives thermal energy of between 5 kW.sub.t and 15 kW.sub.t to the inventive combustion system (1). By means of the serially interconnected primary and tertiary heat exchanger units (8, 17) in series, the water flow leaves the hybrid combustion system (1) by extracting thermal energy of between 10 kW.sub.t and 30 kW.sub.t. In a preferred embodiment of the invention, thermal energies of the primary, secondary and tertiary heat exchangers (8, 17) vary depending on the amount of fuel, air and water supplied to the combustion system (1). The inventive combustion system (1) provides a modulation range of 10 kW.sub.t to 30 kW.sub.t. Depending on the place and purpose of use of the combustion system (1), the modulation range and the minimum/maximum thermal loads extracted can vary and this is included within the scope of the present invention.

[0077] In the inventive combustion system (1), firstly natural gas is supplied to the system (1) by means of the fuel valve (5). Whereas the air required for combustion is sent to the surface-type burner (3) by the compressor (6) and the air valve (7) positioned upstream the compressor (6). Using the fuel valve (5) and the air valve (7), a rich natural gas-fuel mixture is generated in the inlet of the burner (3). This mixture is burned in the surface-type burner (3) and a partially oxidized gas comprising H.sub.2, CO and low amount of unburned CH.sub.4 is generated. Initiation of the combustion is ensured by the ignition electrode (4). Presence of continuous flame is controlled by the ionization electrode (19) in the invention whereas flame temperature is measured by means of a thermocouple (20). The exhaust gas generated in the surface-type burner (3) heats the water flow passing through the pipes while it passes through the jacket part of the primary heat exchanger (8). The water to the primary heat exchanger (8) is pumped by means of a pump (9) and flow is controlled by the valve (10). Flow of the water to be given to the heat exchanger (8) is adjusted by the flow meter (1) and the water heated is transferred to the tertiary heat exchanger (17) over the pipe line (22). The exhaust gases leaving the primary heat exchanger (8) pass through the jacket part of the secondary heat exchanger (12). Exhaust gases heat the air supplied to the secondary heat exchanger (12), by means of the compressor (6), and the amount supplied is adjusted by means of the secondary heat exchanger air valve (13). The air heated is mixed with the combustible exhaust gas passing through the secondary heat exchanger (12) and thus the gas mixture with poor fuel content is composed in the zone remaining under the gas distributor plate (14). The gas mixture reaches the moisture trap (15) by passing through the holes of the distributor plate (14) and the aperture. The gas mixture with H.sub.2 and CO content passing through the moisture trap (15) burns by flameless combustion the exhaust gases generated pass through the jacket part of the tertiary heat exchanger (17) and released to the atmosphere by means of the exhaust pipe.

[0078] In the inventive system (1), NO.sub.x emissions of the homogenous type combustion reaction occurring in the surface-type burner (3) in the exhaust gas released to the atmosphere reduce to trace amounts as it is proceeded from the stoichiometric combustion (lambda value 1) to the rich combustion (lambda value 0.6). Whereas the water flow exiting the primary heat exchanger (8) leaves the system (1) upon being heated further in the tertiary heat exchanger (17).

[0079] Part of the heat released as a result of rich combustion by the inventive combustion system (1) is used to obtain hot water using the heat exchangers (8, 17), in other words for obtaining 50 C. domestic radiator and/or tap water. Both at the surface-type burner (3) outlet and the catalytic burner (16) outlet, there are heat exchangers (8, 17) interconnected in series. Water flow to be delivered to the radiators for the purpose of domestic heating extracts a heat of 20 kW.sub.t in average from the primary and tertiary heat exchangers (8, 17). Approximately half of this thermal load is provided from the heat of the gases of the partial oxidation product as a result of rich combustion and this heat is transferred to the water over the primary heat exchanger (8). Whereas half of the thermal load obtained in the combustion system (1) is obtained in the catalytic burner (16) and the heat obtained is transferred to the radiator side over the tertiary heat exchanger (17) which is connected to the primary heat exchanger (8) in series. In the inventive combustion system (1), the primary heat exchanger (8) and the tertiary heat exchanger (17) are used for the purpose of water heating whereas there is a secondary heat exchanger (12) used for the heat exchange between the gas and the secondary air. The combustion air passing through the secondary heat exchanger (12) is heated in the tubular-type heat exchanger by the heat of the partial oxidation product leaving the rich combustion zone.

[0080] The gas with H.sub.2CO content released as a result of the rich combustion by means of the inventive combustion system (1) is mixed with the combustion air pumped by the compressor (6) in the outlet of the secondary heat exchanger (12) and poor fuel combustion mixture is obtained. By adjusting the heat extraction capacity of the primary heat exchanger (8) used for water heating the thermal load of the secondary heat exchanger (12) used for air heating could be adjusted to achieve the minimum temperature of the air-fuel mixture transferred to the catalytic burner (16), where catalytic combustion can initiate.

[0081] Besides, according to demand hot water required for radiator domestic heating systems operating between the inlet/outlet temperatures of 30-50 C/60-80 C. can be provided by the combustion system (1). In addition to production of domestic hot water, the present invention is also used as an initial burner or as a couple of initial burner-final burner in systems generating hydrogen from natural gas by catalytic reforming methods.

[0082] It is possible to develop various embodiments of the inventive hybrid homogenous-catalytic combustion system (1) therefore it cannot be limited to the examples disclosed herein, the system is fundamentally as it is described in the claims