EXHAUST GAS TREATMENT SYSTEM

Abstract

An exhaust system for the treatment of a humid exhaust gas comprising a species to be treated, the system comprising: a dehumidifier system comprising a humid air inlet for providing a flow of humid exhaust gas; a first gas inlet for providing a flow of dehumidified exhaust gas; a second gas inlet for providing a flow of heated gas; a plurality of sorbent beds for releasably storing the species; a treatment unit comprising either: one or more catalysts for decomposing the species; or a condensing unit for recovering the species in liquid or aqueous form; 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 dehumidified 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 the treatment unit 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; wherein the flow of dehumidified exhaust gas provided by the first gas inlet is received from the dehumidifier system.

Claims

1. An exhaust system for the treatment of a humid exhaust gas comprising a species to be treated, the system comprising: a dehumidifier system comprising a humid air inlet for providing a flow of humid exhaust gas; a first gas inlet for providing a flow of dehumidified exhaust gas; a second gas inlet for providing a flow of heated gas; a plurality of sorbent beds for releasably storing the species; a treatment unit comprising either: one or more catalysts for decomposing the species; or a condensing unit for recovering the species in liquid or aqueous form; 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 dehumidified 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 the treatment unit 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, at least one other sorbent bed is in the second configuration; wherein the flow of dehumidified exhaust gas provided by the first gas inlet is received from the dehumidifier system.

2. The exhaust system according to claim 1, wherein the dehumidifier system comprises: a humid air inlet for providing a flow of humid exhaust gas; a further gas inlet for providing a further flow of heated gas; a plurality of water-sorbent beds, comprising a water storage material, for releasably storing water; a further gas outlet in fluid communication with the first gas inlet; an external gas outlet; and a dehumidifier valve system configured to establish independently for each water-sorbent bed fluid communication in a first or second dehumidifier configuration, wherein: i) in the first dehumidifier configuration the flow of the humid exhaust gas from the humid air inlet contacts a water-sorbent bed for storing water and then passes to the further gas outlet; and ii) in the second dehumidifier configuration the further flow of heated gas from the further gas inlet contacts a water-sorbent bed for releasing the water to form a heated humidified gas which then passes to the external gas outlet; wherein the dehumidifier valve system is configured to ensure that at least one water-sorbent bed is in the first dehumidifier configuration and, preferably at least one other water-sorbent bed is in the second dehumidifier configuration.

3. The exhaust system according to claim 1, wherein the dehumidifier system comprises: a humid air inlet for providing a flow of humid exhaust gas; a water storage material arranged to receive the humid exhaust gas from the humid air inlet; a further gas outlet for receiving dehumidified exhaust gas passing through the water storage material, which is in fluid communication with the first gas inlet; an external gas outlet arranged downstream of a selected portion of the water storage material; and a further gas inlet for providing a further flow of heated gas arranged to pass through the selected portion of the water storage material to release water stored therein and to form a heated humidified gas which passes through the external gas outlet; wherein the dehumidifier system is configured so that the selected portion of the water storage material changes over time.

4. The exhaust system according to claim 1, wherein: i) the species is ammonia, the catalyst is an ammonia oxidation catalyst and wherein each sorbent bed comprises an ammonia storage material; or ii) the species is formaldehyde, the catalyst is a formaldehyde oxidation catalyst and wherein each sorbent bed comprises a formaldehyde storage material; or iii) the species is methane, the catalyst is a methane oxidation catalyst and wherein each sorbent bed comprises a methane storage material; or (iv) the species comprises VOCs, the catalyst is an oxidation catalyst and wherein each sorbent bed comprises a VOC storage material.

5. The exhaust system according to claim 1, wherein the humid exhaust gas comprises from 1 to 5000 ppm of the species.

6. The exhaust system according to claim 1, wherein the humid exhaust gas is at a temperature at least 25° C. below an effective catalyst treatment temperature.

7. The exhaust system according to claim 1, wherein the second gas inlet incorporates a heating device for providing the flow of heated gas.

8. The exhaust system according to claim 7, wherein the heating device is configured to provide a flow of gas at a temperature of from 100 to 600° C. .

9. The exhaust system according to claim 1, wherein dehumidified exhaust gas is supplied to both the first and second gas inlets, or wherein the second gas inlet is an air inlet.

10. The exhaust system according to claim 1, wherein the system further comprises one or more material filters to pre-filter the exhaust gas.

11. The exhaust system according to claim 1, 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.

12. The exhaust system according to claim 1, 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.

13. The exhaust system according to claim 1, the system further comprising one or more sensors for the species in communication with each sorbent bed to determine a species loading status .

14. (canceled)

15. The exhaust system according to claim 1, wherein the treatment unit comprises one or more catalysts for decomposing the species, and wherein a further heater is provided immediately upstream of the one or each catalyst.

16. The exhaust system according to claim 1, 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.

17. The exhaust system according to claim 1, wherein the treatment unit comprises one or more catalysts for decomposing the species, and wherein the flow of heated gas is heated with heat obtained from the catalytic treatment of the species, whereby the system can be maintained in an autothermal condition.

18. (canceled)

19. The exhaust system according to claim 2, wherein the dehumidifier system further comprises means for recovering heat from the heated humidified gas.

20. The exhaust system according to claim 19, wherein the means is a heat exchanger and the heat exchanger is used to provide heat to another part of the exhaust system, preferably to provide the further flow of heated gas.

21. A livestock house, HVAC installation, waste water treatment plant, or a mine, comprising the exhaust system according to claim 1.

22. A method of treating a humid exhaust gas comprising a species to be treated, the method comprising passing the humid exhaust gas through the exhaust system according to claim 1.

Description

[0146] The invention will now be described in relation to the following non-limiting figures, in which:

[0147] FIG. 1 shows a schematic of an exhaust system according to claim 1.

[0148] FIG. 1 shows an exhaust gas system 1 as described herein. The exhaust gas system 1 is configured to process a humid exhaust gas 5 from a livestock house 10. The humid exhaust gas 5 passes through an exhaust gas inlet 15 into the exhaust gas treatment system 1.

[0149] The humid exhaust gas 15 passes through a coarse material filter 20 to remove matter such as poultry feathers and then through a H.sub.2S sorbent filter 25. The humid exhaust gas 5 then passes to a dehumidifier system 26 so as to remove the moisture from the humid exhaust gas 5. The dehumidifier system 26 comprises an outlet 27 through which a flow of dehumidified exhaust gas is communicated with the remainder of the exhaust system 1. The dehumidified exhaust gas passes through a first gas inlet to either a first sorbent bed 30 or a second sorbent bed 35, depending on a valve system comprising valves 40.

[0150] 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. Similarly, in one embodiment the dehumidifier system comprises an independent dehumidifier valve system configured to direct gases (e.g. humid exhaust gas 5 and heated fresh air) through a plurality of water sorbent beds (not shown).

[0151] 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.

[0152] 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). Similarly, a flow of heated gas supplied to the dehumidifier system may be directed via valves to contact a water saturated sorbent bed to liverate the water stored therein and which then passes to external gas outlet 38.

[0153] 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.

[0154] 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.

[0155] 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.