EXHAUST GAS TREATMENT SYSTEM

Abstract

An exhaust system for the treatment of an exhaust gas comprising a species to be treated, the system comprising: a first gas inlet for providing a flow of exhaust gas; a second gas inlet for providing a flow of heated gas; a plurality of sorbent beds for releasably storing the species; one or more catalysts for decomposing the species; first and second exhaust gas outlets; and a valve system configured to establish independently for each sorbent bed fluid communication in a first or second configuration, wherein: i) in the first configuration the flow of the exhaust gas from the first gas inlet contacts a sorbent bed for storing the species and then passes to the first gas outlet; and ii) in the second configuration the flow of heated gas from the second gas inlet contacts a sorbent bed for releasing the species, passes to one of the one or more catalysts and then passes to the second exhaust gas outlet; wherein the valve system is configured to ensure that at least one sorbent bed is in the first configuration and, preferably at least one other sorbent bed is in the second configuration.

Claims

1-16. (canceled)

17. An exhaust system for the treatment of an exhaust gas comprising a species to be treated, the system comprising: a first gas inlet for providing a flow of exhaust gas; a second gas inlet for providing a flow of heated gas; a plurality of sorbent beds for releasably storing the species; one or more catalysts for decomposing the species; first and second exhaust gas outlets; and a valve system configured to establish independently for each sorbent bed fluid communication in a first or second configuration, wherein: i) in the first configuration the flow of the exhaust gas from the first gas inlet contacts a sorbent bed for storing the species and then passes to the first gas outlet; and ii) in the second configuration the flow of heated gas from the second gas inlet contacts a sorbent bed for releasing the species, passes to one of the one or more catalysts and then passes to the second exhaust gas outlet; wherein the valve system is configured to ensure that at least one sorbent bed is in the first configuration and, preferably at least one other sorbent bed is in the second configuration.

18. The exhaust system according to claim 17, wherein the species is ammonia, the catalyst is an ammonia oxidation catalyst and wherein each sorbent bed comprises an ammonia storage material.

19. The exhaust system according to claim 17, wherein the species is formaldehyde, the catalyst is a formaldehyde oxidation catalyst and wherein each sorbent bed comprises a formaldehyde storage material.

20. The exhaust system according to claim 17, wherein the species is methane, the catalyst is a methane oxidation catalyst and wherein each sorbent bed comprises a methane storage material.

21. The exhaust system according to claim 17, wherein the species is the species comprises VOCs, the catalyst is an oxidation catalyst and wherein each sorbent bed comprises a VOC storage material.

22. An exhaust system according to claim 17, wherein exhaust gas comprises from 1 to 5000 ppm of the species.

23. An exhaust system according to claim 17, wherein the exhaust gas is at a temperature at least 25° C. below an effective catalyst treatment temperature and preferably is at ambient temperature.

24. An exhaust system according to claim 17, wherein the second gas inlet incorporates a heating device for providing the flow of heated gas.

25. An exhaust system according to claim 24, wherein the heating device is configured to provide a flow of gas at a temperature of from 100 to 600° C., preferably 100 to 350° C.

26. An exhaust system according to claim 17, wherein an exhaust gas is supplied to both the first and second gas inlets, or wherein the second gas inlet is an air inlet.

27. An exhaust system according to claim 17, wherein the system further comprises one or more material filters to pre-filter the exhaust gas.

28. An exhaust system according to claim 17, wherein the system comprises a contaminant sorbent material upstream of the plurality of sorbent beds, wherein the contaminant is selected from one or more of As, SO.sub.2, SO.sub.3, H.sub.2S, Hg and Cl.

29. An exhaust system according to claim 17, wherein the valve system is configured to ensure that one sorbent bed is in the second configuration, and the remainder of the plurality of sorbent beds are in the first configuration.

30. An exhaust system according to claim 17, the system further comprising one or more sensors for the species in communication with each sorbent bed to determine a species loading status, preferably one or more ammonia sensors in communication with each sorbent bed to determine an ammonia loading status.

31. An exhaust system according to claim 17, wherein the heater is a gas burner, preferably a propane, natural gas or biogas burner.

32. An exhaust system according to claim 17, wherein a further heater is provided immediately upstream of the one or each catalyst.

33. An exhaust system according to claim 17, wherein the valve system is further configured to establish independently for each sorbent bed fluid communication a third configuration for cooling of the sorbent bed, wherein gases are prevented from leaving the sorbent bed.

34. A livestock house comprising the exhaust-gas system according to claim 17.

35. An HVAC installation comprising the exhaust-gas system according to claim 17.

36. A waste water treatment plant comprising the exhaust-gas system according to claim 17.

37. A mine comprising the exhaust-gas system according to claim 17.

38. A method of treating an exhaust gas comprising a species to be treated, the method comprising passing the exhaust gas through the exhaust-gas system according to claim 17.

Description

[0074] The invention will now be described in relation to the following non-limiting figures, in which:

[0075] FIG. 1 shows a schematic of an exhaust system according to claim 1.

[0076] FIG. 1 shows an exhaust gas system 1 as described herein. The exhaust gas system 1 is configured to process an exhaust gas 5 from a livestock house 10. The exhaust gas 5 passes through an exhaust gas inlet 15 into the exhaust gas treatment system 1.

[0077] The exhaust gas 15 passes through a coarse material filter 20 to remove matter such as poultry feathers and then through a H.sub.25 sorbent filter 25. The exhaust gas 5 then passes to either a first sorbent bed 30 or a second sorbent bed 35, depending on a valve system comprising valves 40.

[0078] A source of fresh air 45 is fed through a fresh air inlet 50 to a propane heater 55. Depending on the valve system, the heated fresh air passes to either the first sorbent bed 30 or the second sorbent bed 35.

[0079] The valves 40 of the valve system is configured so that one of the first sorbent bed 30 and the second sorbent bed 35 receives the exhaust gas 5 and the other receives the fresh air 45.

[0080] A further valve system comprising further valves 60 is provided to direct the gas leaving the first sorbent bed 30, via an electrical heater 65 to an ammonia oxidation catalyst 70 and to a catalyst-treated exhaust gas outlet 75, or directly to a further exhaust gas outlet 80. At the same time the further valves 60 are configured to direct the gas leaving the second sorbent bed 35 to the other outlet (80, 75).

[0081] In one embodiment gas leaving the catalyst-treated exhaust gas outlet 75 or the further exhaust gas outlet 80 may be recycled to the heater 55 as a combustion gas.

[0082] In one embodiment gas leaving the sorbent bed 30, 35 may be recycled into the house 10. In one embodiment gas leaving the catalyst-treated exhaust gas outlet 75, together with a larger exhaust mass flow towards 80 may be recycled into the house 10 if the mixing temperature of both streams permit.

[0083] The invention will now be described in relation to the following non-limiting example.

EXAMPLE 1

[0084] NH.sub.3 in a poultry coop with 30,000 broilers is taken here as a model pollutant. Typical NH.sub.3 concentrations are around 15 ppm. The inside air in the barn will be polluted with 2700 grams of NH.sub.3 per hour. Assuming a two-leg installation (i.e. 2 sorbent beds) and a loading time of 30 minutes for either NH.sub.3 storage, 60 kg of active charcoal or 20 kg of zeolite per leg would have to be used for the sorption phase.

[0085] In the desorption phase of each leg, a relatively small fresh air stream is heated to 250° C., resulting in desorption peak concentrations of, for example, 1000 ppm NH.sub.3. This pollutant-laden, small gas stream is then directly fed to a catalytic reactor in which an ammonia oxidation catalyst (AMOX) is placed. An AMOX converts part of the NH.sub.3 to NO. Subsequently, NH.sub.3 and NO react with each other to form air-borne, harmless nitrogen and water. At aforementioned reaction conditions, NH.sub.3 conversions of over 95% were experimentally proven.

[0086] Although preferred embodiments of the invention have been described herein in detail, it will be understood by those skilled in the art that variations may be made thereto without departing from the scope of the invention or of the appended claims.