NO342601B1 - Process and plant for producing biogas - Google Patents
Process and plant for producing biogas Download PDFInfo
- Publication number
- NO342601B1 NO342601B1 NO20151467A NO20151467A NO342601B1 NO 342601 B1 NO342601 B1 NO 342601B1 NO 20151467 A NO20151467 A NO 20151467A NO 20151467 A NO20151467 A NO 20151467A NO 342601 B1 NO342601 B1 NO 342601B1
- Authority
- NO
- Norway
- Prior art keywords
- biogas
- digester
- flow
- process water
- gas
- Prior art date
Links
- 238000000034 method Methods 0.000 title claims abstract description 71
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 32
- 239000010802 sludge Substances 0.000 claims abstract description 8
- 238000001556 precipitation Methods 0.000 claims abstract description 7
- 239000002245 particle Substances 0.000 claims abstract description 5
- 238000000746 purification Methods 0.000 claims abstract description 5
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 15
- 238000004519 manufacturing process Methods 0.000 claims description 9
- 238000000926 separation method Methods 0.000 claims description 7
- 230000005611 electricity Effects 0.000 claims description 5
- 239000003337 fertilizer Substances 0.000 claims description 5
- 239000011368 organic material Substances 0.000 claims description 2
- 239000011343 solid material Substances 0.000 claims 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 13
- 239000007789 gas Substances 0.000 description 9
- 239000007788 liquid Substances 0.000 description 7
- 229910002092 carbon dioxide Inorganic materials 0.000 description 6
- 239000007787 solid Substances 0.000 description 6
- 239000002699 waste material Substances 0.000 description 5
- 235000015097 nutrients Nutrition 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 239000000446 fuel Substances 0.000 description 2
- 239000010815 organic waste Substances 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 239000002253 acid Substances 0.000 description 1
- 239000002154 agricultural waste Substances 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 239000012620 biological material Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 230000002301 combined effect Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 230000029087 digestion Effects 0.000 description 1
- 238000010494 dissociation reaction Methods 0.000 description 1
- 230000005593 dissociations Effects 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 210000003608 fece Anatomy 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 239000010808 liquid waste Substances 0.000 description 1
- 239000010871 livestock manure Substances 0.000 description 1
- 239000002754 natural gas substitute Substances 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 230000020477 pH reduction Effects 0.000 description 1
- 230000001376 precipitating effect Effects 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 238000011144 upstream manufacturing Methods 0.000 description 1
- 239000002351 wastewater Substances 0.000 description 1
- 238000004065 wastewater treatment Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/66—Treatment of water, waste water, or sewage by neutralisation; pH adjustment
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F11/00—Treatment of sludge; Devices therefor
- C02F11/02—Biological treatment
- C02F11/04—Anaerobic treatment; Production of methane by such processes
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F9/00—Multistage treatment of water, waste water or sewage
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E50/00—Technologies for the production of fuel of non-fossil origin
- Y02E50/30—Fuel from waste, e.g. synthetic alcohol or diesel
Abstract
Process and plant for producing bio gas in a digester (21), wherein bio sludge (6) leaving the digester (21) is subjected to at least one step of purification (25) to thereby produce a flow of process water (10), while biogas flow (2) produced in the digester (21) is subjected to at least one process step from which at least one flow of CO2 containing gas (7) is discharged. At least one CO2 containing gas (7) is combined with the process water (10) to reducethe pH thereof to enhance particle precipitation in the process waterfor subsequent removal.Process and plant for producing bio gas in a digester (21), leaving bio sludge (6) leaving the digester (21) is subjected to at least one step of purification (25) thereby producing a flow of process water (10), while biogas flow (2) produced in the digester (21) is subjected to at least one process step from which at least one flow of CO2 containing gas (7) is discharged. At least one CO2 containing gas (7) is combined with the process water (10) to reduce the pH thereof to enhance particle precipitation in the process water for subsequent removal.
Description
Process and plant for producing biogas
The present invention concerns a method for the producing bio gas in a digester as defined by the preamble of claim 1.
According to another aspect the present invention concerns a biogas plant as defined by the preamble of claim 7.
Background
Biogas is formed by processing organic waste in the absence of free oxygen. Unlike the traditional incineration plants converting the waste into low quality energy in the form of heat, biogas can be converted to a natural gas substitute and could be used as a vehicle fuel amongst other things. The biological residues from the process are rich in nutrients and could be used as a fertilizer. With increasing amounts of waste produced from both households and industry, biogas production could be an important option for waste handling.
A prominent issue in biogas production is the biological residue, which constitutes a dry and a wet fraction. The dry fraction, digested solids, is currently used as a fertilizer whereas the wet fraction, digested liquids, is usually sent to sewerage system and waste water treatment. The wet fraction may be rich in nutrients currently not applicable as a fertilizer, due to geographical and transport constraints. It may further contain particulates and other compounds with attributes that induce clogging of sewerage pipelines and treatment systems. It is therefore of interest to reduce the level of particulates and other compounds in the wet fraction.
US patent application No 2004/0164021 describes a method in which CO2is used to reduce pH in digested liquids. The process involves removal and recovery of nutrients and recycling of water from digested manure or other organic wastes. A first step involves separating waste from an anaerobic digester into digested liquids, digested solids, and biogas. A second step involves precipitating solids from the digested liquids. A third step involves stripping ammonia from the digested liquids. A fourth step involves injecting an exhaust stream of carbon dioxide drawn from the co-generator into the digested liquids to reduce pH and raise the temperature of the digested liquid. There is, however, not indicated any step of precipitation of solids subsequent the step of injecting CO2.
JPS 5926195A describes a method for treatment of an alkaline cellulosic aqueous liquid waste in which the alkalinity is neutralized by the addition of CO2.
Thus, while it is known to adjust pH in process water handling system in a number of ways, including the addition of CO2, no such adjustment has to our knowledge been suggested or applied to enhance processes of purification of process water.
Objects of the invention
It is thus an object of the present invention to provide an improved process and apparatus for the generation of biogas from biologic material and for optimization of such processes, exemplified as processes and plants for the production of substantially pure methane and processes and plants for generation of electric power in a biogas energy plant based on conventional organic material such as waste from households and from industrial and agricultural processes as well as from agricultural waste .
It is a particular object to provide an improved process as indicated above in which particle precipitation from waste water is improved.
The present invention
The above object(s) are achieved by a method or process according to the present invention as set forth in claim 1.
According to another aspect the present invention concerns a bio gas power plant as set forth in claim 7.
Preferred embodiments of the invention are disclosed by the dependent claims.
By “purification” as used herein is understood and process for removing undesired matter or separating different matters, desired or undesired, from one another.
The indication herein that a matter “is useful for” a particular application or use, means that it is suitable for such use, directly or indirectly, but that the actual use does not constitute part of the present invention.
Below the invention is described in terms of a couple of non-limiting embodiments with reference to the enclosed drawings, where:
Figure 1 is a simplified process flow scheme of a traditional process for generation of electricity and steam in a biogas plant.
Figure 2 is a simplified process flow scheme of an embodiment of a process for generation of electricity and steam in a biogas plant according to the present invention.
Figures 3 and 4 show an embodiment different form the embodiment shown in Figure 2.
Figure 5 shows a variant of the embodiment shown in Figures 3 and 4.
Figure 1 shows a flow of raw material 1 into a digester 21 in which anaerobic digestion takes place, typically operated at mesophile or thermophile temperature, resulting in a desired biogas product flow 2 rich in methane and also containing substantial amounts of CO2, while a second process flow is a bio-sludge 6 that needs to be taken care of. Minor amounts of other gases will also be present in the resulting biogas product flow 2 from the digester 21.
The biogas product flow 2 is typically divided into plural partial flows 3, 4 and 5. Two of these partial biogas flows 3 and 4 are shown fed into generators 22, 23 for production of electrical power 12, 13 for use in any convenient manner, e.g. for delivery to a grid of electric power.
Off-gas 7 consisting mainly of CO2may be released to atmosphere due to the fact that the production of biogas from organic raw material is CO2neutral as such. In conventional processes for production of electricity from bio-gas produced as described above, the CO2has typically been vented off to atmosphere.
One partial flow 5 of biogas product flow, typically one third, is shown fed to a gas fuelled steam boiler 24. The steam boiler generates hot water and/ or steam 14, e.g. to an upstream process for feedstock hydrolization or for use in any other suitable application.
The bio-sludge 6 is fed to a decanter centrifuge 25 for dewatering. The dewatered sludge 11 may be sold for use as a fertilizer while the process water 10 separated therefrom is taken care of as explained below.
Reference is now made to Figure 2. In the process according to the present invention, at least some of the CO2discharged from the generators 22, 23 and/ or the steam boiler 24, is combined at 26 with the flow of process water 10 separated from the bio-sludge, to thereby reduce the pH level in the process water 10, resulting in a reduced pH process water 16.
CO2injected into water leads to a pH reduction due to the formation of carbonic acid, H2CO3and its dissociation. While being a comparatively weak acid, the pH is readily brought into the range of 7.0 - 7.2.
Particles 18 are separated from this reduced pH process water 16 in at least one precipitation step 27, providing a purified process water flow 17. This has the combined effect of enhancing precipitation of solid matter from the process water, while reducing direct release of CO2to the atmosphere.
Process flow 19, indicated by dotted line, illustrates that part of the process water is optionally recycled for reuse in the process.
Precipitated particles are filtered from the process water with conventional filtering techniques whereafter the process water may be subjected to further treatment not constituting part of the present invention.
Figure 3 and 4 illustrate a different embodiment of the present invention. According to this embodiment there is no energy production in the process; instead the bio-gas is run through a separation unit 220 in which the methane 120 is separated from the other gases and delivered as pure product for subsequent use. The methane gas may still be used as a fuel, but not as an integral part of the present process. There is neither any step of (energy demanding) steam boiler in this embodiment, while the combination of CO2with the process water, which is the core of the present invention, naturally is present. Figure 3 provides an overview allowing comparison with the previous embodiment while Figure 4 shows the elements of this embodiment only.
Figure 5 discloses yet another embodiment which may be seen as a variant of the embodiment of Figure 4. According to this embodiment the biogas formed in the digester 21 is directed in part to a separation unit 220, as in the case of Figure 4, but also in part to a boiler 24 which generates hot water and/ or steam 14 like explained in relation to Fig.1 and Fig.2. The discharge flows from the upgrading unit are substantially pure methane labelled 120 and CO2labelled 7. The core of the present invention is fulfilled by adding CO2from process flow 7 to the process water 10 as in the previous examples. A difference from the embodiment of Ft of figures 3 and 4 is that a boiler is involved. This particular embodiment may be useful in situations where there is no need for produced electricity but a significant need for heat in the form of hot water and/ or steam.
Final comments
As indicated the core of the present invention is the combination of CO2 with the process water in order to facilitate precipitation of solid matter from the latter.
A person skilled in the art will readily understand that desired amounts of the CO2generated or released in the present process, may be subjected to additional treatment processes and/ or subsequent use, none of which constitute direct part of the present invention.
The embodiments described in relation to the enclosed drawings represent preferred embodiments of the invention, the scope of which solely being defined by the accompanying claims.
Claims (10)
1. Process for producing bio gas in a digester (21), wherein bio sludge (6) leaving the digester (21) is subjected to at least one step of purification (25) to thereby produce a flow of process water (10), while biogas flow (2) produced in the digester (21) is subjected to at least one process step from which at least one flow of CO2containing gas (7) is discharged, characterized in that at least one CO2containing gas (7) is combined with the process water (10) to reduce the pH thereof to enhance particle precipitation in the process water for subsequent removal.
2. Process as claimed in claim 1, wherein the at least one process step (220) from which at least one flow of CO2containing gas (7) is discharged, is a step involving separation to produce substantially pure methane (120)
3. Process as claimed in claim 1, wherein biogas (2) produced in the digester (21) is split into at least two parallel biogas flows (3, 5) and charged to at least one generator (22) and at least one steam boiler (24) respectively, wherein at least one CO2 containing process flow (7, 9) from said generator (22) or steam boiler (24) is combined with the process water (10)
4. Process as claimed in claim 2, wherein the biogas flow (2) from the digester (21) is split into three partial flows (3, 4, 5), two of which are fed to generators (22, 23) arranged in parallel while the third is fed to a steam boiler (24).
5. Process as claimed in any one of the preceding claims, wherein the one step of purification (25) of the bio sludge (6) is a step involving use of a centrifuge to mechanically separate process water (10) from solid materials (11).
6. Process as claimed in any one of the preceding claims, wherein the solid material (11) separated from the process water (10) is useful as a fertilizer
7. Bio Gas plant for the production of biogas from organic material comprising a digester (21), separation means (25) for mechanical separation of solid material from produced bio sludge (6) to thereby produce process water (10); at least one reactor unit (22, 220) for further processing of biogas formed in the digester (21), further comprising required conduits from the digester (21) to the at least one reactor unit (22, 220 and to the separation means (25), characterized in that at least one conduit 15 is arranged to combine at least one CO2containing process flow (7) from the at least one reactor unit (22, 220)) with the process water (10) in a CO2/ process water combiner (26).
8. Biogas plant as claimed in claim 7, wherein the at least one reactor unit (22, 220) is a unit (220) for separation of biogas (2) to produce substantially pure methane (120).
9. Biogas plant as claimed in claim 7 or 8, wherein the at least one reactor unit (22, 220) further comprises at least one generator (22, 23) for production of electricity.
10. Biogas plant as claimed in claim 7, 8 or 9 wherein the at least one reactor unit (22, 220) further comprises steam boiler (24) for generation of steam.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NO20151467A NO342601B1 (en) | 2015-10-28 | 2015-10-28 | Process and plant for producing biogas |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NO20151467A NO342601B1 (en) | 2015-10-28 | 2015-10-28 | Process and plant for producing biogas |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| NO20151467A1 NO20151467A1 (en) | 2017-05-01 |
| NO342601B1 true NO342601B1 (en) | 2018-06-18 |
Family
ID=61800067
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| NO20151467A NO342601B1 (en) | 2015-10-28 | 2015-10-28 | Process and plant for producing biogas |
Country Status (1)
| Country | Link |
|---|---|
| NO (1) | NO342601B1 (en) |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5926195A (en) * | 1982-08-02 | 1984-02-10 | Agency Of Ind Science & Technol | Treatment of cellulose-contg. waste matter |
| US20040164021A1 (en) * | 2003-01-20 | 2004-08-26 | Xiaomei Li | Process for removal and recovery of nutrients from digested manure or other organic wastes |
| WO2012040880A1 (en) * | 2010-09-30 | 2012-04-05 | General Electric Company | Membrane filtration process with high water recovery |
| WO2014096527A1 (en) * | 2012-12-21 | 2014-06-26 | Upm-Kymmene Corporation | Method of treating primary effluent of a pulp, paper or plywood mill by introducing exhaust gas comprising carbon dioxide |
-
2015
- 2015-10-28 NO NO20151467A patent/NO342601B1/en unknown
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5926195A (en) * | 1982-08-02 | 1984-02-10 | Agency Of Ind Science & Technol | Treatment of cellulose-contg. waste matter |
| US20040164021A1 (en) * | 2003-01-20 | 2004-08-26 | Xiaomei Li | Process for removal and recovery of nutrients from digested manure or other organic wastes |
| WO2012040880A1 (en) * | 2010-09-30 | 2012-04-05 | General Electric Company | Membrane filtration process with high water recovery |
| WO2014096527A1 (en) * | 2012-12-21 | 2014-06-26 | Upm-Kymmene Corporation | Method of treating primary effluent of a pulp, paper or plywood mill by introducing exhaust gas comprising carbon dioxide |
Also Published As
| Publication number | Publication date |
|---|---|
| NO20151467A1 (en) | 2017-05-01 |
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