PROCESS AND APPARATUS FOR IN-SITU CLEANING OF A GAS SEPARATOR IN AN ANAEROBIC BIOREACTOR

Abstract

The present invention relates to a process for in-situ cleaning of a gas-liquid separator of an anaerobic bioreactor, comprising directing a gas flow in the bioreactor in order to create a scouring effect from turbulent fluid flows resulting in the cleaning of at least a part of the gas-liquid separator. The invention further relates to a process for treating a fluid aqueous waste stream, wherein use is made of the in-situ cleaning process. The invention further relates to a bioreactor suitable for carrying out a process according to the invention.

Claims

1. A process for in-situ cleaning of a gas-liquid separator of an anaerobic bioreactor, comprising directing a gas flow in the bioreactor in order to create a scouring effect from turbulent fluid flows resulting in the cleaning of at least a part of the gas-liquid separator.

2. The process of claim 1, wherein the gas-liquid separator comprises a gas collector which is fluidly connected to a closable gas pipe, which gas pipe is further fluidly connected to an open-ended chamber of the reactor vessel, which in-situ cleaning process comprises a step of closing the gas pipe, thereby allowing gas to release from underneath the gas collector, thereby causing the scouring effect from a turbulent fluid flow resulting in the cleaning of at least a part of the gas-liquid separator.

3. The process of claim 1, wherein the gas-liquid separator comprises a gas channel, which gas channel is provided with a closable gas pipe adapted to allow passage of a gas from the gas channel to a headspace of the reactor vessel, which in-situ cleaning process comprises opening the gas pipe, thereby allowing gas to release into the headspace, thereby causing a scouring effect from a turbulent fluid flow resulting in the cleaning of at least a part of the gas channel and the gas pipe.

4. A process for treating a fluid aqueous waste stream comprising a biodegradable organic substance, comprising feeding the aqueous waste stream into an anaerobic bioreactor; reacting the biodegradable organic substance with the biomass in the bioreactor under essentially anaerobic conditions, thereby forming biogas; said process comprising carrying out a process for the in-situ cleaning claim 1, whilst continuing the treatment of the waste stream.

5. The process of claim 1, wherein the gas pipe is a branched pipe having at least two gas outlets, connected to different parts of the reactor vessel.

6. The process of claim 5, wherein at least one gas pipe branch is adapted to allow passage of the gas from the gas pipe to the headspace of the reactor vessel and the second gas pipe branch is connected to the open-ended chamber of the reactor vessel.

7. The process of claim 1, wherein the gas pipe is reversibly closable by one or more valves or other closing means present in or at an end of the said gas pipe.

8. The process of claim 1, wherein the gas used in said cleaning process essentially consists of biogas produced by the anaerobic conversion of the organic substance in the bioreactor.

9. The process of claim 1, wherein the gas used in said cleaning process comprises biogas and further comprises an external gas source.

10. The process of claim 1, wherein the bioreactor comprises a plurality of gas-liquid separators, wherein the gas-liquid separators are arranged in multiple staggered levels in the reactor vessel of the bioreactor.

11. The process of claim 1, wherein the gas pipe is automatically closable and openable.

12. The process of claim 1, wherein the gas pipe is closed and re-opened intermittently, thereby providing a preventative cleaning whereby excessive buildup of solids is at least substantially avoided.

13. The process of claim 1, wherein the bioreactor is an upflow reactor.

14. A bioreactor suitable for the process of claim 1, wherein said bioreactor comprises: a reactor vessel for containing at least a fluid; an influent inlet for introducing a flow of a fluid aqueous waste stream comprising a biodegradable organic substance into the reactor vessel; an effluent outlet for withdrawing an aqueous effluent flow from the reactor vessel; a gas outlet for withdrawing gas from the reactor vessel; a gas-liquid separator present in the reactor vessel, wherein the gas-liquid separator comprises a gas collector and a gas channel; and, a gas pipe which is connected to the gas-liquid separator, which gas pipe is further adapted to allow the passage of a gas from the gas channel to a headspace of the reactor vessel, or, is fluidly connected to an open-ended chamber of the reactor vessel.

15. The bioreactor of claim 14, wherein the gas pipe is a branched pipe having at least two branches with an outlet, wherein the outlet of the first branch is connected to a different part of the reactor vessel than the outlet of the second branch.

16. The bioreactor of claim 15, wherein the first gas pipe branch is adapted to allow passage of the gas from the gas pipe to the headspace of the reactor vessel and wherein the second gas pipe branch is connected to the open-ended chamber of the reactor vessel.

17. The bioreactor of claim 14, wherein the gas pipe is reversibly closable by one or more valves or other closing means present in or at an end of said gas pipe.

18. The bioreactor of claim 14, wherein the closing means of the gas pipe are one or more automatic open/close valves or other closing means.

19. The bioreactor of claim 18, wherein the one or more valves or other closing means are provided with a controller to allow automated intermittently opening and closing the gas pipe.

20. The bioreactor of claim 14, wherein the bioreactor comprises a plurality of gas-liquid separators, which are arranged in multiple staggered levels in the reactor vessel of the bioreactor.

21. The bioreactor of claim 14, wherein the influent inlet for the bioreactor is an influent distribution system.

22. The process of claim 7, wherein said one or more valves or other closing means present in or at an end of the said gas pipe are present outside of the bioreactor.

23. The process of claim 9, wherein the external gas source is selected from the group consisting of methane and nitrogen.

24. The process of claim 13, wherein the upflow reactor is selected from the group consisting of upflow anaerobic sludge blanket reactors, expanded granular sludge blanket reactors, internal circulation reactors, fluidized bed reactors, anaerobic baffled reactors and anaerobic filters.

25. The bioreactor of claim 21, wherein said influent distribution system is present in a lower part of the reaction vessel.

Description

[0065] The various aspects of the invention are now illustrated on the basis of the Figures, wherein the gas-liquid separators are provided in two levels, of which one level is optional.

[0066] FIGS. 1a and 1b show different cross sectional views, which are 90 degrees horizontally rotated with respect to each other, of a bioreactor and gas-liquid separator in normal operation,

[0067] FIGS. 2a and 2b show different cross sectional views, which are approximately 90 degrees horizontally rotated with respect to each other, of a bioreactor in the cleaning mode for the gas-liquid separator (corresponding to the first aspect of the invention and first preferred embodiment),

[0068] FIGS. 3a and 3b show different cross sectional views, which are approximately 90 degrees horizontally rotated with respect to each other, of a bioreactor in cleaning mode for the gas channel and first gas pipe of the bioreactor (corresponding to the first aspect of the invention and the second preferred embodiment).

[0069] FIGS. 1a and 1b show a bioreactor (1) according to the invention in normal operation, which bioreactor (1) comprises the reactor vessel (2) containing a fluid aqueous waste water which is fed into the reactor vessel via an inlet (not shown). The waste water rises in the reactor vessel (2), wherein a sludge bed is present consisting of mainly granular sludge. Due to the anaerobic breakdown of the (biological) contaminants in the waste water biogas (such as methane) is formed and a mixture of solid, liquid and gas develops. The fluid, such as a gas-liquid mixture, passes (flows) upwards and enters the submerged gas-liquid separator (5), where the gas is separated from the mixture via a titled baffle (plate) arrangement (10). The separated gas is collected by the gas collectors (gas hoods) (6), which gas is indicated by the dotted shading in FIGS. 1a and 1b. The collected gas is then transported via the gas channel (11) to the branched gas pipe (7, 7a, 7b). The valve on the gas pipe (7b) is closed, while the valve on the gas pipe (7a) is open, which allows the gas to escape via the outlet of the gas pipe (7a) into the fluid contained in the open-ended chamber (9) of the reactor vessel (2). This enables the gas-fluid interface level inside the gas-liquid separator (5) to be maintained. The gas released into the open-ended chamber (9) causes an in the fluid level in the open-ended chamber (9) of the reactor vessel (2), since the fluid becomes less dense. An anaerobic effluent flow (cleaned effluent) is withdrawn through the effluent discharge pipe (3) present in the upper part of the reactor vessel (2). The (bio)gas produced is removed from the headspace (8) of the reactor vessel (2) via the gas discharge pipe (4) present at the top of the bioreactor (1).

[0070] FIGS. 2a and 2b show a bioreactor (1) in cleaning mode for the gas-liquid separator (5) of the bioreactor (2). The difference between FIGS. 1a and 1b and FIGS. 2a and 2b, is that in FIGS. 2a and 2b the valve of the gas pipe (17,17a) is closed. Optionally, the gas pipe (17,17a) comprises a gas pipe branch (17b) indicated by a dashed line, which gas pipe branch (17b) also has a closed valve. By closing the valve(s) of the gas pipe (17,17a,17b), gas is prevented from escaping into the open-ended chamber (9) of the reactor vessel (2) and the gas pressure builds up underneath the gas collector (gas hoods) (6). This gas pressure build-up continues until the pressure is sufficient to lower the gas-fluid interface level in the gas-liquid separator (5) leading to the gas escaping causing a turbulent fluid flow resulting in the cleaning of at least part of the gas-liquid separator (5).

[0071] FIGS. 3a and 3b show a bioreactor (1) in cleaning mode for the gas channel (11) and gas pipe (27,27b) of the gas-liquid separator (5) of the bioreactor (1). The difference between FIGS. 1a and 1b and FIGS. 3a and 3b, is that in FIGS. 3a and 3b, the valve of the gas pipe (27,27b) is open, which gas pipe (27,27b) has an outlet fluidly connected to the head space (8) of the reactor vessel (2). The gas pipe (27,27b) optionally comprises gas pipe branch (27a) indicated by the dashed line, which gas pipe branch (27a) is fluidly connected the open-ended chamber (9) of the reactor vessel (2) via an open valve. By opening the valve(s) of the gas pipe (27,27b,27a), the gas is allowed to escape directly upwards to the headspace (8) of the bioreactor (1) and this causes the gas-fluid interface level in the gas channel (11) to rise, thereby causing a turbulent fluid flow resulting in the cleaning of at least part of the gas channel (11) and the gas pipe (27,27b,27a).