WO2010020023A1

WO2010020023A1 - Equipment and process for the capture and purification of biogas and storage of purified gas.

Info

Publication number: WO2010020023A1
Application number: PCT/BR2008/000324
Authority: WO
Inventors: Daniel Camilotti; Flavio Camilotti; João CAMPOS
Original assignee: Daniel Camilotti; Flavio Camilotti; Campos Joao
Priority date: 2008-08-17
Filing date: 2008-08-17
Publication date: 2010-02-25

Abstract

The present invention concerns an equipment and a process for the capture and purification of biogas, and storage of purified gas, useful for the exploitation of the biogas generated by waste, avoiding its launching into the atmosphere, what would cause damage to the environment. The equipment comprises a series of filters to separate the gases contained in the biogas, and purify it, and compressors (5, 14) to compress it, so as to facilitate its storage.

Description

EQUIPMENT AND PROCESS FOR THE CAPTURE AND PURIFICATION OF BIOGAS, AND STORAGE OF PURIFIED GAS.

The present invention concerns an equipment and process for capturing and purifying biogas, and bottling the purified gas, useful for the exploitation of gases generated by waste, avoiding its launching into the atmosphere , what would cause damage to the environment .

In urban centers domestic garbage is collected and taken to landfills, where it is dumped so as not to pollute the environment. That garbage contains a significant amount of organic matter able to be biodegradable a process of anaerobic digestion, which, by the action of microorganisms transforms the organic matter, releasing gas.

The biogas generated in such locals is basically composed of methane (CH₄) , carbon dioxide (CO₂) , nitrogen

(N₂) , oxygen (O₂) and hydrogen sulfide gas (H₂S) . The proportion of each gas in the mixture depends on several parameters , such as the kind of garbage or degraded residues . One of the released gases is carbon dioxide (CO₂) , one of the responsibles for the phenomenon called greenhouse effect, that contributes to the warming up of the planet.

Aiming to avoid launching biogas in the atmosphere, presently it is simply drained and burned. That solution presents some inconveniences as it increases the air pollution, added to the fact that the burned biogas transforms the methane gas into carbon dioxide and water vapor, worsening the greenhouse effect.

Having in sight the elevated caloric power of the biogas, one alternative to the mere burning, has been the implementation of electric energy generation systems, as a means to take advantage of it, besides avoiding environmental pollution. Methane is a high value fuel which, isolated from the other substances present in the biogas, can be employed to power automotive engines, electric energy generators, hospital equipment, refrigeration equipment, etc. Besides those advantageous uses of biogas, the companies and institutions that reduce the emission of greenhouse effect-causing gases, may obtain financial resources' from the commercialization of carbon credits, according to the conditions established in the Kyoto protocol. Namely, once a carbon emission reduction certificate is obtained, resulting from the Clean Development Mechanism (CDM) , it can be traded with other institutions that need it to stay within the limits established in the Protocol. Nevertheless, despite those advantages, the energy generating systems existing in the prior art are associated with a very high cost for their implementation, making them unfeasible for small sized entities or developing countries . Also, those systems are designed with the specific aim of generating energy, and do not provide a production of methane from biogas, so as to allow its storage for any later use.

To solve the problems of the prior art, the present invention concerns both an equipment and a process to capture biogas, to purify biogas by extracting high value gases, and also to store the purified gas, storing it in cylinders, to allow its later use after capture.

The process of the invention offers environmental advantages, once it eliminates bad odors when biogas is kept from being released to the environment, and polluting gas - as carbon dioxide - emissions to the atmosphere that increase the greenhouse effect, are avoided. As the release of biogas to the environment is prevented, bad odors are decreased, thus allowing the economic development in the vicinities of the landfills, or manure deposits. The process is also beneficial in terms of energy, as it is a local source of fuel, trustworthy and renewable, decreasing the dependency from fossil fuels.

Additionally, gas from landfills or manure deposits is the only gas that, as it is utilized, reduces the atmospheric pollution.

To describe the present invention in more details, the attached figure is a schematic view of an equipment for the capture and purification of biogas, and storage of purified gas, according to the invention, whose breadth of protection is determined only by the scope of the attached claims .

According to the meaning used herein, the word garbage concerns any and all residue that, when dumped, generates gases, such as domestic and industrial waste, residues from animals, coal mines, etc.

In a first aspect the present invention concerns an equipment to capture and purify biogas, and to store such a purified gas, comprising a garbage gas capture element (1) ; a hydrogen sulfide gas retention desulfurizer (2) ; a humidity separating filter (3) that separates water from the gas,- a low pressure compressor (5) to pressurize the gas; a forced-ventilation pre-cooling condenser (6) to lower the gas temperature, and condense it; a bleeder (8) to extract condensed liquid; a coalescence filter (9) ; an activated carbon filter (10) , and a low pressure intermediary reservoir (11)

The gas capture element (1) preferably is a perforated probe which is immersed in the garbage site drainage or vertical well, for example of a landfill or a manure deposit, so as to capture the gas generated therein.

The desulfurizer (2) preferably is one that contains steel chips so as to retain hydrogen sulfide gas (H²S) , that reacts chemically with the iron oxide (Fe2O3) contained in the steel chips. Nevertheless, any other known means can be used, such as steel wool, or chemical agents, such as a solution of water and caustic soda

In the suite, the equipment comprises a humidity separating filter that withdraws water from the biogas , letting only a mixture of gases to continue to the compressor (5) .

The low pressure compressor (5) is used to suck and pressurize the gas mixture. The invention equipment preferably comprises a solenoid valve (4) that turns off the equipment for its maintenance, when the compressor (5) stops or condensed liquid returns through the duct (24) .

In the forced-ventilation pre-cooling condenser (6) the temperature of the gas mixture is lowered, so as to condense it, allowing the separation of water that is withdrawn by the bleeder (8) .

Preferably, the invention equipment comprises a buoyant filter (7) in the exit of the condenser (6) so that, when there is an excess of condensed liquid, it is eliminated, and returned to the separating filter (3) through the duct (24) . Advantageously, the buoyant filter (7) retains the excess humidity to be liberated when it is opened under pressure. The bleeder (8) extracts the remaining condensed liquid, which is sent along with the CO₂, to the separating filter (3) , that withdraws the remaining water, and redirects the CO₂ to the systems. The coalescent filter (9) is utilizes to eliminate humidity and oil aerosols, acting as an auxiliary in the purification of the biogas .

Preferably, for the coalescent filter (9) , there is at least one parallel coalescent filter (9) , each one of each is located between two valves (91) , for control of passage of the gas mixture. This disposition allows shutting down one line when the other is cleaned, avoiding the total interruption of the equipment. Each one of the coalescent filters comprises one reservoir to accumulate the condensed gas mixture, and one bleeder (92) to expel humidity directly to the separating filter (3) return drain (24) .

The use of the activated carbon filter (10) is adequate as it eliminates most of the lubricant oil commonly absorbed in the compressor (5) , besides removing odor, and being auxiliary to the drying the gas.

Preferably, for the activated carbon filter (10) , there is at least one parallel activated carbon filter (10) , each one positioned between two valves (101) that allow their alternate use in filtering water, allowing the cleaning of one filter (10) while the other is in use, avoiding total interruption of the equipment .

The equipment comprises a low pressure intermediary reservoir (11) to store the gas already clean and ready for consumption, or even to make it available for a second step of purification. Preferably, the reservoir (11) comprises a bleeder (111) to expel the humidity directly to the separating filter (3) return drain (24) . In the event a purer gas is needed, a secondary purification system is added to the equipment, comprising a solenoid valve (12) ; a retention valve with flow control

(13); a high pressure compressor (14); a heat exchanger condenser (15) to heat up the gas so as to improve its olphative identification, provided with a bleeder (151) to expel humidity directly to drain (24) ; an activated carbon filter (16) to filtrate the gas mixture; a refrigeration system (17) to cool the gas and increase its storage ability; a refrigerated drying filter (18); a plurality of activated carbon filters (19) to withdraw possible remaining hydrogen sulfide gas and drying of the gas; and a plurality of tanks (20) to store the purified gas. Preferably, for the activated carbon filter (16) , there is at least one parallel activated carbon filter (16) , each one of which is located between two valves (161) , that allow their alternate use in filtering water, allowing the cleaning of one filter (16) when the other is in use.

The activated carbon filters (19) are positioned in two parallel series, each one of which with two valves (191) , forming a bypass-type system, what allows its alternate use for cleaning, as one series is being cleaned, the other one is working.

Preferably, the internal surface of the equipment, in contact with the biogas, are treated with phosphate to avoid the corrosion caused by the gases, increasing its durability . Preferably, the equipment also comprises controls for pressure, temperature and flow, and one unit for monitoring and protection, offering security during the purification of the gas. In this particular embodiment, the electro- digital controls possess interfaces to personal computers, palm tops, and alike, with USB ports, internet or intranet. The equipment and the process of the invention are, preferably, automated and can be remotely controlled, by internet or intranet. The operator in control can visualize the process on an electric panel, and is able to interfere at any time as necessary.

The components of the equipment can be near or far from each other, interconnected for instance by means of energy conducting ducts.

In a further aspect, the present invention concerns a process to capture and purify biogas, and store the purified gas for use as necessary (later or not) , avoiding biogas to be released to the environment, where it would increase the greenhouse effect.

The process of the present invention comprises two phases of gas purification. Basically, in the first phase the biogas is treated so as to eliminate the hydrogen sulfide gas and water, while in the following second phase, a mixture of gases is treated so as to reach a higher purity, as required to its use in vehicles.

In the first phase, the process comprises the following steps: a. Capture of biogas; b. Desulfurization of biogas; c. Withdrawal of humidity from the mixture of gases; d. Compression of the mixture of gases; e. Cooling of the mixture of gases; f. Withdrawal of condensed liquid remaining from the cooling; g. Filtration to eliminate humidity; h. Withdrawal of sulfur compounds,- and i . Storage of mixture of gases .

The process is initiated with the introduction of an element (1) in a capture duct inside the garbage (as in fig. 1) in a landfill, a manure deposit or bio-digestion container, to capture the biogas resulting from the chemical reaction of the waste contained therein. The captured biogas is passed through a desulfurizer (2) where the hydrogen sulfide gas is withdrawn by way of a chemical reaction.

After the removal of the hydrogen sulfide gas, the mixture follows to a humidity separating filter (3) , where humidity is withdrawn from the mixture of gases,• that then goes to a low pressure compressor (5) , responsible for the compression of mixture of gases already de-humidified.

The low pressure compressor (5) is advantageous in view of the short distance to the probe (1) , as it is more efficient in the capture of gas, as compared to the performance a high pressure compressor would have in this situation.

In the following step after the compression, the mixture of gases is cooled in a forced-ventilation pre- cooling condenser (6) where the mixture of gases and the contained liquid are condensed, such that the liquid condenses with a portion of the gas, here referred to as condensed liquid, favoring the withdrawal of the condensed liquid, achieved by a bleeder (8) .

Bleeder (8) can be manually or electronically controlled. When electronically controlled, it is activated as a minimal percentage of humidity is detected at the bottom of the condenser, established according to the quality of the biogas, so as not to interrupt too often the working of the equipment. When manually operated, the control is achieved by time, also considering the quality of the biogas, and can be done for instance every 30 seconds . This step of withdrawing the condensed liquid can be achieved, additionally, in a buoyant filter (7) which, located before the bleeder (8) , withdraws the excess of liquid coming from the condenser (6) . The condensed liquid withdrawn from bleeder (8) and from the buoyant filter (7) is returned to the equipment through a duct (24) , being redirected to the humidity separating filter (3) , thus keeping the gas possibly mixed with the liquid from being released to the atmosphere. At this step of withdrawing the condensed liquid, the working of the equipment is interrupted by way of the solenoid valves (4) and (12) , making the condensed liquid return through the duct (24) until the separating filter (3) . The mixture of gases continues to a filtering step to eliminate humidity and oil aerosols in a coalescent filter

(7) , after what comes a step to remove sulfur compounds, in an activated carbon filter (10)

Free from sulfur and humidity, the mixture of gases, as the final step of the first phase, is stored in low pressure reservoirs (11) .

After the execution of the first phase the obtained product is a mixture of gases with high quality, which can be used, for instance, in industrial stoves, boilers, generator groups or any other equipment of immediate use.

That mixture of gases comprises about 87% methane, 2% carbon dioxide, 8% nitrogen, 3% oxygen, 8ppm hydrogen sulfide gas and 10 ppm water vapor (ppm = parts per million) . After the first phase, the process comprises a second phase that treats the gas so as improve its purity, such as for the VNG (vehicle natural gas) required to be used by vehicles, needing higher purity, i.e., the mixture of gases must reach the necessary purity and follow the norms established by the control authorities.

In the second phase, additional to the first phase, the process comprises the following steps: a. Compression of the mixture of gases; b. Heating the mixture of gases up to about 80⁰C; c. Withdrawal of odor from the mixture of gases; d. Cooling the mixture of gases down to about between -5⁰C and -35⁰C; e. Drying the mixture of gases by refrigeration f. Filtering the mixture of gases; and g. Storage of the mixture of gases.

In this second phase there is a solenoid valve (12) that, along with the retention valve with flow control (13) , allow the passage of the mixture of gases to be compresses in the high pressure compressor (14), that increases its pressure.

After the compression, the mixture of gases goes to a heat exchanger condenser (15) where it is heated, and goes to a third step of filtration in an activated carbon filter

(16) useful to eliminate sulfur compounds that might still be present in the mixture of gases .

After going through the filter (16) the heated mixture of gases is subject to a thermal shock when it is cooled in a refrigeration system (17) , increasing its storage capacity. This refrigeration system (17) comprises a chamber provided with a compressor (170) , an engine with forced ventilation (171) and an evaporator (172) , that make the temperature of the mixture of gases drop. Beside those components, the refrigeration system (17) also comprises a bleeder (173) to expel the humidity directly to the separating filter (3) return drain (24) .

In a particular embodiment, the mixture of gases is heated in the heat exchanges (12) to a temperature of about 80⁰C, and it is cooled in the refrigeration system (17) to a temperature of between about -5⁰C and -35⁰C, coming to a dew point state .

To eliminate the remaining impurities and lower the carbon dioxide (CO₂) content still present in the mixture of gases issued from the refrigeration step, the mixture goes through a refrigerated drying filter (18) provided with a bleeder (181) to expel humidity directly to drain (24) , followed by a plurality of activated carbon filters (19) .

After those filtration operations, the mixture of gases is pressurized in storage cylinders (20) , already with a methane purity of about 87% in volume of the purified mixture. Thus, the drying of the mixture of gases, which is in the dew point state of between about -5°C and -35°C, is done simultaneously to the concentration in a drying filter

(concentrator) (18) , to eliminate part of the remaining CO₂ from the filtering steps up to a final point of at least about 87% in volume purity of methane.

The methane gas obtained from biogas, through the process of the invention, can then be stored in bottles or tanks for later use.

With the present process one obtains a high quality product that can be used as fuel in replacement of alcohol, gasoline, diesel and acetylene, and its containment cylinders can be, for instance, connected to the vehicle distribution pumps (not illustrated) .

To obtain methane gas of lower quality, but still useful, it is not necessary to use the second phase as described above, the operation of first phase being sufficient .

In the same way, when gas is used for obtaining heat, in industrial stoves, boilers and energy generation, the process can be simplified, as high purity is not necessary, so the mixture of gases from the first phase of the present invention can be used.

The energy produced can be used by cities, rural properties, or commercialized, and in this sense presents a potential source of income, as already mentioned, in the sale of carbon credits, or carbon emission reduction certificates . To allow cleaning, maintenance or to give off excess production, without releasing the gas remaining in the equipment and ducts into the atmosphere, the equipment may additionally comprise a system to allow the burning of gas. For that, the equipment comprises a solenoid valve (21), a spark producer (22) and a burner (23) , respectively responsible for the release, firing and burning of gas.

Only when the equipment is turned off, the valve (4) disposed before the low pressure compressor (5) shuts down for the condensate to be directed for combustion (23) or capture (1) .

The equipment of the invention allows the retro- washing of the humidity separating filter (3) and of the desulfurizer (2) when one purges the condensed liquid. That is so because in the bleeder there happens the return of the condensed liquid by the drain (24) until the humidity separating filter (3) and desulfurizer (2), thus achieving the retro-washing. In this situation the equipment has its working interrupted by solenoid valves (4) and (12) disposed before the low pressure compressor (5) and the high pressure compressor (14) , temporarily closing the flow of biogas from probe (1) .

The gas generated by the present process can be used for the working of the components of the present equipment, making the system self-sufficient. One uses for that end a combustion engine coupled to an energy generator (not shown), that feeds said components.

The person skilled in the art will immediately perceive, from the description above, the many ways to work the invention without departing from the scope of the attached claims.

Claims

1. Equipment to capture and purify biogas, and store the purified gas, characterized by comprising a garbage gas capture element (1) ; a desulfurizer (2) for the retention of hydrogen sulfide gas; a humidity separating filter (3) to separate water from the gas; a low pressure compressor (5) to pressurize the gas,- a forced-ventilation pre-cooling condenser

(6) to lower the gas temperature, and condense it; a bleeder

(8) to extract the remaining condensed liquid; a coalescence filter (9) ; an activated carbon filter (10) , and a low pressure intermediary reservoir (11) .

2. Equipment according to claim 1 characterized by additionally comprising a solenoid valve (4) before compressor (5) .

3. Equipment according to claim 1, characterized by comprising a buoyant filter (7) between the condenser (6) and the bleeder (8) .

4. Equipment according to claim 1, characterized by the fact that gas capture element (1) is a perforated probe.

5. Equipment according to claim 1, characterized by the fact that the desulfurizer (2) comprises steel chips.

6. Equipment according to claim 1, characterized by the fact that it comprises, for the coalescent filter (9), at least one parallel coalescent filter (9) , both filters provided with bleeders (92) , each of the filters (9) positioned between two valves (91) .

7. Equipment according to claim 1, characterized by the fact that it comprises, for the carbon activated filter (10), at least one parallel carbon activated filter (10) , each of the filters positioned between two valves (101) .

8. Equipment according to claim 1, characterized by the fact that it comprises, for the bleeder (111) , at least one parallel bleeder (111) to expel humidity in a drain (24) .

9. Equipment according to claim 1 characterized by also comprising a secondary gas purification system comprising a solenoid valve (12) ; a retention valve with flow control (13) ; a high pressure compressor (14), at least one heat exchanger condenser (15) to heat up the gas; at least one activated carbon filter (16) to filter a mixture of gases; at least one refrigeration system (17) to cool the gas, increasing its storage capacity; at least one refrigerated drying filter

(18) ; a plurality of activated carbon filters (19) to withdraw odor and dry the gas; and a plurality of tanks (20) to store the purified gas.

10. Equipment according to claim 9 characterized by the fact that the heat exchanger condenser (15) comprises at least one bleeder (151) to expel humidity to a drain (24) .

11. Equipment according to claim 9 characterized by the fact that the activated carbon filters (19) are positioned in two parallel series, each one of which between two valves

(191)

12. Equipment according to claim 9 characterized by the fact that it comprises, for the activated carbon filter (16) , at least one parallel activated carbon filter (16) , each one of which is positioned between two valves (161) -

13. Equipment according to claim 9 characterized by the fact that the refrigeration system (17) comprises at least one chamber provided with at least one compressor (170) , at least on forced ventilation engine (171) , at least an evaporator (172) , and at least a bleeder (173) to expel humidity to a drain (24) .

14. Equipment according to claim 9 characterized by the fact that the drying filter (18) comprises at least one bleeder (181) to expel humidity to a drain (24) .

15. Equipment according to any one of claims 1 to 9 characterized by the fact that is comprises a solenoid valve (21) , a spark producer (22) and a burner (23) , respectively responsible for release, flame and burn of gas.

16. Equipment according to any one of claims 1 to 15 characterized by the fact that the internal surface of the components of said equipment are treated with phosphate

17. Equipment according to any one of claims 1 to 15 characterized by the fact that it also comprises pressure, temperature and flow controllers, and a unit for monitoring and protection, provided with interfaces to personal computers, palm tops, and alike, with USB ports, internet or intranet.

18. FOR THE CAPTURE AND PURIFICATION OF BIOGAS, AND STORAGE OF PURIFIED GAS characterized by the fact that it comprises the following steps : a. Capture of biogas; b. Desulfurization of biogas; c. Withdrawal of humidity from the mixture of gases; d. Compression of the mixture of gases; e. Cooling of the mixture of gases; f. Withdrawal of condensed liquid remaining from the cooling ; g. Filtration to eliminate humidity; h. Withdrawal of sulfur compounds; and i . Storage of mixture of gases .

19. Process according to claim 18 characterized by the fact that the capture of biogas step is achieved by way of a perforated probe (1) .

20. Process according to claim 18 characterized by the fact that the biogas desulfurization step is achieved by way of a desulfurizer (2)

21. Process according to claim 18 characterized by the fact that the withdrawal of gas humidity step is achieved with a humidity separating filter (3) .

22. Process according to claim 18 characterized by the fact that the compression of the gas step is achieved with a low pressure compressor (5) .

23. Process according to claim 18 characterized by the fact that the step of cooling of the mixture of gases is achieved with a forced-ventilation pre-cooling condenser.

24. Process according to claim 18 characterized by the fact that the step of withdrawal of condensed liquid remaining from the cooling is achieved with at least one bleeder (8) and at least one buoyant filter (7) .

25. Process according to claim 18 characterized by the fact that the step of humidity elimination filtration is achieved with at least one coalescent filter (9) .

26. Process according to claim 18 characterized by the fact that the step or withdrawing the sulfur compounds is achieved with an activated carbon filter (10) .

27. Process according to claim 18 characterized by the fact that the step of storing the gas is achieved with at least on lower pressure reservoir (11) .

28. Process according to claim 24 characterized by the fact that the liquid part withdrawn by bleeder (8) and buoyant filter (7) , is redirected to the humidity separating filter (3) , achieving the retro-washing of the filter (3) and of the desulfurizer (2) .

29. Process according to claim 18 characterized by comprising the following subsequent steps: a. Compression of the mixture of gases; b. Heating the mixture of gases up to about 80⁰C; c. Withdrawal of odor from the mixture of gases; d. Cooling the mixture of gases down to about between - 5⁰C and -35⁰C; e. Drying the mixture of gases by refrigeration; f . Filtration of the mixture of gases; g. Storage of the mixture of gases.

30. Process according to claim 29 characterized by the fact that the step of compression of the mixture of gases is achieved with a high pressure compressor (14) .

31. Process according to claim 29 characterized by the fact that the step of heating the mixture of gases is achieved with at least one heat exchanger condenser (15) .

32. Process according to claim 29 characterized by the fact that the step of withdrawal of odor from the mixture of gases is achieved with at least one carbon activated filter (16) .

33. Process according to claim 29 characterized by the fact that the step of cooling the mixture of gases is achieved with at least one refrigeration system (17) .

34. Process according to claim 29 characterized by the fact that the step of drying the mixture of gases is achieved with at least one refrigerated drying filter (18) .

35. Process according to claim 29 characterized by the fact that the step of filtration of the mixture of gases is achieved with activated carbon filters (19) .

36. Process according to claim 29 characterized by the fact that the storage of the mixture of gases is achieved in tanks (20) .