Biogas Recovery - Revision history

Ranisha: /* Digester Heating */

2016-04-28T06:36:14Z

‎Digester Heating

Ranisha at 09:35, 8 April 2015

2015-04-08T09:35:09Z

Wiki Gardener at 14:12, 13 October 2014

2014-10-13T14:12:31Z

Wiki Gardener at 14:05, 13 October 2014

2014-10-13T14:05:58Z

Wiki Gardener at 14:04, 13 October 2014

2014-10-13T14:04:54Z

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Fungai Cecilia Sandamu at 07:55, 15 May 2014

2014-05-15T07:55:01Z

Ranisha at 13:00, 20 March 2014

2014-03-20T13:00:06Z

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Ranisha: /* Thermal insulation */

2014-03-20T12:51:59Z

‎Thermal insulation

Frank Helbig at 19:52, 28 January 2014

2014-01-28T19:52:04Z

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Frank Helbig: /* Plug-flow process */

2014-01-28T19:45:23Z

‎Plug-flow process

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 |-
 ! heating power
-| style="text-align: center" | 150 kW/m<sup>3</sup>
+| style="text-align: center" | 150 W/m<sup>3</sup>
-| style="text-align: center" | 210 kW/m<sup>3</sup>
+| style="text-align: center" | 210 W/m<sup>3</sup>
-| style="text-align: center" | 270 kW/m<sup>3</sup>
+| style="text-align: center" | 270 W/m<sup>3</sup>
 |}
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 <br/>
 == Internal and External Heating Systems<br/> ==

← Older revision		Revision as of 09:35, 8 April 2015
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	= Overview =		= Overview =

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 Biogas plants with plug flow – the wet-digestion version is also known as a tank through-flow arrangement – use the expeller effect of fresh substrate infeed to create a plug flow through a digester of round or box section. Mixing transverse to the direction of flow is usually achieved by paddle shafts or specially designed baffles.<br/>Broadly speaking, there are horizontal and upright plug-flow digesters. Virtually all the digesters used in agricultural plants are of the horizontal type. At this time, upright digesters operating on the plug-flow principle are rare and they are not considered in this study.<br/>
-[[File:Plugflow digester.jpg|thumb|center|540px|Plugflow digester|alt=Plugflow digester.jpg]]<br/>
+[[File:Plugflow digester.jpg|thumb|center|540px|Plugflow digester|alt=Plugflow digester.jpg]]<br/>The digesters are usually horizontal steel tanks, factory-built and then delivered to site. This necessitates transport of the digesters to site, which is possible only up to a certain size of tank. Possible uses are as main digesters for small-scale plants or as preliminary digesters for larger plants with stirred-tank reactors (round tanks). Horizontal digesters arranged in batteries for parallel operation can increase throughput. The plug-flow principle reduces the possibility of unintentionally discharging undigested substrate from the reactor, and dwell time can be maintained very reliably for all the material<ref name="Jäkel, K.: Management document 'Landwirtschaftliche Biogaserzeugung und -verwertung', Sächsische Landesanstalt für Landwirtschaft, 1998/2002">Jäkel, K.: Management document 'Landwirtschaftliche Biogaserzeugung und -verwertung', Sächsische Landesanstalt für Landwirtschaft, 1998/2002</ref><span style="line-height: 1.5em;  font-size: 0.85em">.</span>
-−
-<span style="line-height: 1.5em;  font-size: 0.85em">The digesters are usually horizontal steel tanks, factory-built and then delivered to site. This necessitates transport of the digesters to site, which is possible only up to a certain size of tank. Possible uses are as main digesters for small-scale plants or as preliminary digesters for larger plants with stirred-tank reactors (round tanks). Horizontal digesters arranged in batteries for parallel operation can increase throughput. The plug-flow principle reduces the possibility of unintentionally discharging undigested substrate from the reactor, and dwell time can be maintained very reliably for all the material</span><ref>Jäkel, K.: Management document 'Landwirtschaftliche Biogaserzeugung und -verwertung', Sächsische Landesanstalt für Landwirtschaft, 1998/2002</ref><span style="line-height: 1.5em;  font-size: 0.85em">.</span>
 <br/>
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 == Batch Processes<br/> ==
-Batch processes use mobile containers or stationary box-type digesters. These processes have achieved commercial maturity in recent years and are established on the market. Reinforced-concrete box digesters are particularly common for fermenting bulk substrates such as maize and grass silage. In the batch process the digesters are filled with biomass and sealed airtight. The microorganisms in the seed substrate mixed through the fresh substrate to inoculate it heat the substrate in the first phase, in<br/>which air is fed into the digester. A composting process associated with the release of heat takes place. When the biomass reaches operating temperature, the supply of air is shut off. Once the supply of entrained oxygen has been consumed, microorganisms become active and convert the biomass into biogas as in wet digestion. The biogas is trapped in the gas headers connected to the digester and piped off for energy extraction <ref>Schulz, H.; Eder, B.: Biogas-Praxis: Grundlagen, Planung, Anlagenbau, Beispiel, 2nd revised edition, Ökobuch Verlag, Staufen bei Freiburg, 1996, 2001, 2006</ref>.<br/>Batteries with between 2 and 8 boxes have proved practical, and the most common arrangement is a 4-box battery. This arrangement suffices to achieve quasi-continuous gas production. A digester battery should also have a leachate tank to catch the seepage liquid from the reactors so that it too can be converted into biogas. The leachate is also sprinkled over the fermentation mass in the reactor to inoculate the material.
+Batch processes use mobile containers or stationary box-type digesters. These processes have achieved commercial maturity in recent years and are established on the market. Reinforced-concrete box digesters are particularly common for fermenting bulk substrates such as maize and grass silage. In the batch process the digesters are filled with biomass and sealed airtight. The microorganisms in the seed substrate mixed through the fresh substrate to inoculate it heat the substrate in the first phase, in<br/>which air is fed into the digester. A composting process associated with the release of heat takes place. When the biomass reaches operating temperature, the supply of air is shut off. Once the supply of entrained oxygen has been consumed, microorganisms become active and convert the biomass into biogas as in wet digestion. The biogas is trapped in the gas headers connected to the digester and piped off for energy extraction <ref name="Schulz, H.; Eder, B.: Biogas-Praxis: Grundlagen, Planung, Anlagenbau, Beispiel, 2nd revised edition, Ökobuch Verlag, Staufen bei Freiburg, 1996, 2001, 2006">Schulz, H.; Eder, B.: Biogas-Praxis: Grundlagen, Planung, Anlagenbau, Beispiel, 2nd revised edition, Ökobuch Verlag, Staufen bei Freiburg, 1996, 2001, 2006</ref>.<br/>Batteries with between 2 and 8 boxes have proved practical, and the most common arrangement is a 4-box battery. This arrangement suffices to achieve quasi-continuous gas production. A digester battery should also have a leachate tank to catch the seepage liquid from the reactors so that it too can be converted into biogas. The leachate is also sprinkled over the fermentation mass in the reactor to inoculate the material.
 <br/>
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 <br/>
-The fermenting substrate is minimally mixed by the introduction of fresh substrate, by thermal convective flows and by gas bubbles rising through the fermenting mass. This passive mixing, however, is not enough, so the mixing process has to be actively assisted.<br/>Mixing can be done mechanically by systems such as agitators inside the reactor, hydraulically by pumps sited in close proximity outside the digester, or pneumatically by blowing biogas into the tank. The last two of these methods are of lesser significance.<br/>In Germany, mechanical mixers or agitators are used in about 85 to 90% of plants <ref>Schulz, H.; Eder, B.: Biogas-Praxis: Grundlagen, Planung, Anlagenbau, Beispiel, 2nd revised edition, Ökobuch Verlag, Staufen bei Freiburg, 1996, 2001, 2006</ref>.
+The fermenting substrate is minimally mixed by the introduction of fresh substrate, by thermal convective flows and by gas bubbles rising through the fermenting mass. This passive mixing, however, is not enough, so the mixing process has to be actively assisted.<br/>Mixing can be done mechanically by systems such as agitators inside the reactor, hydraulically by pumps sited in close proximity outside the digester, or pneumatically by blowing biogas into the tank. The last two of these methods are of lesser significance.<br/>In Germany, mechanical mixers or agitators are used in about 85 to 90% of plants<ref name="Schulz, H.; Eder, B.: Biogas-Praxis: Grundlagen, Planung, Anlagenbau, Beispiel, 2nd revised edition, Ökobuch Verlag, Staufen bei Freiburg, 1996, 2001, 2006">Schulz, H.; Eder, B.: Biogas-Praxis: Grundlagen, Planung, Anlagenbau, Beispiel, 2nd revised edition, Ökobuch Verlag, Staufen bei Freiburg, 1996, 2001, 2006</ref>.
 <br/>
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 == Digester Heating<br/> ==
-The temperature inside the digester has to be uniform, in order to ensure an optimum digestion process. In this respect it is not so much maintaining the specified temperature to within one tenth of a degree that is important as keeping temperature fluctuations within tight limits. This applies to temperature fluctuations over time and also to temperature imbalance in different parts of the digester <ref>Jäkel, K.: Management document' Landwirtschaftliche Biogaserzeugung und -verwertung', Sächsische Landesanstalt für Landwirtschaft, 1998/2002</ref>. Severe fluctuations and excursions above or below certain temperature levels can impede the digestion process or even bring it to a complete standstill under worst-case conditions.
+The temperature inside the digester has to be uniform, in order to ensure an optimum digestion process. In this respect it is not so much maintaining the specified temperature to within one tenth of a degree that is important as keeping temperature fluctuations within tight limits. This applies to temperature fluctuations over time and also to temperature imbalance in different parts of the digester<ref name="Jäkel, K.: Management document 'Landwirtschaftliche Biogaserzeugung und -verwertung', Sächsische Landesanstalt für Landwirtschaft, 1998/2002">Jäkel, K.: Management document 'Landwirtschaftliche Biogaserzeugung und -verwertung', Sächsische Landesanstalt für Landwirtschaft, 1998/2002</ref>. Severe fluctuations and excursions above or below certain temperature levels can impede the digestion process or even bring it to a complete standstill under worst-case conditions.
 <u>The causes of temperature fluctuations are many and varied:</u>
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 <br/>
-The substrate has to be heated in order to achieve the necessary process temperatures and to compensate for heat losses; this can be done by heat exchangers or heaters either installed externally or integrated into the digester. <ref>Schulz, H.; Eder, B.: Biogas-Praxis: Grundlagen, Planung, Anlagenbau, Beispiel, 2nd revised edition, Ökobuch Verlag, Staufen bei Freiburg, 1996, 2001, 2006</ref> Integrated heaters heat the substrate inside the digester.
+The substrate has to be heated in order to achieve the necessary process temperatures and to compensate for heat losses; this can be done by heat exchangers or heaters either installed externally or integrated into the digester.<ref name="Schulz, H.; Eder, B.: Biogas-Praxis: Grundlagen, Planung, Anlagenbau, Beispiel, 2nd revised edition, Ökobuch Verlag, Staufen bei Freiburg, 1996, 2001, 2006">Schulz, H.; Eder, B.: Biogas-Praxis: Grundlagen, Planung, Anlagenbau, Beispiel, 2nd revised edition, Ökobuch Verlag, Staufen bei Freiburg, 1996, 2001, 2006</ref> Integrated heaters heat the substrate inside the digester.
 <br/>External heat exchangers heat the substrate before it is fed into the digester, so the substrate is preheated before entering the digester. This helps avoid temperature fluctuations associated with substrate infeed. When external heat exchangers are used, either substrate recirculation through the heat exchanger must be continuous or an extra internal heater inside the digester is indispensable, in order to maintain a constant temperature inside the digester.
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 [[File:Digesterheating.jpg|thumb|right|348px|Digesterheating]]
-To achieve the optimum biogas yield, the anaerobic digestion needs constant environmental conditions, preferably close to the [[Optimization of Biogas Production|process optimum]]. The digester temperature is of prime importance. In temperate areas, a heating system and an insulation of the digester is necessary. Hence, the needed temperature for digestion can be reached and a loss of energy by transmission is compensated.
+To achieve the optimum biogas yield, the anaerobic digestion needs constant environmental conditions, preferably close to the [[Optimization_of_the_Biogas_Production_Process|process optimum]]. The digester temperature is of prime importance. In temperate areas, a heating system and an insulation of the digester is necessary. Hence, the needed temperature for digestion can be reached and a loss of energy by transmission is compensated.
 Because of the high costs for material and installation of a heating system, a low-cost biogas plant, as needed in developing countries, can only be build without heating. To boost the biogas yield for those plants, the building of a bigger digester to increase the retention time would be cheaper. A bigger digester reduces the required maintenance, while a heating system, increases maintenance requirements. A bigger digester serves also as a buffer for sediments, pH-variations and gas storage. For example, a fixed dome plant sized 50% bigger, is only 10% more expensive.

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 = Overview =
-*[[Biogas_Technology|Biogas Technology]]
+*[[Biogas Technology|Biogas Technology]]
-*[[Biogas_Basics|Biogas Basics]]
+*[[Biogas Basics|Biogas Basics]]
-−
 = Digester Design<br/> =
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 <br/>
-[[File:Stirred tank biogas reactor properties.JPG|thumb|center|180px|Stirred tank biogas reactor properties]]
+[[File:Stirred tank biogas reactor properties.JPG|thumb|center|750px|Stirred tank biogas reactor properties]]
 === <br/>Plug-Flow Process<br/> ===
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 <br/>
-[[File:Plug flow biogas reactor properties.JPG|thumb|center|747px|Plug flow biogas reactor properties|alt=Plug flow biogas reactor properties.JPG]]
+[[File:Plug flow biogas reactor properties.JPG|thumb|center|750px|Plug flow biogas reactor properties|alt=Plug flow biogas reactor properties.JPG]]
 <br/>
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 *[[Portal:Biogas|Biogas Portal on energypedia]]
-*[[Biogas_Basics|Biogas Basics]]
+*[[Biogas Basics|Biogas Basics]]
-−
 = References =

← Older revision		Revision as of 07:55, 15 May 2014
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	= Digester Design<br/> =		= Digester Design<br/> =

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		+	[[Category:Biogas]]

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 = Heating =
-[[File:Digester insulation.JPG|thumb|right|180px|Digester insulation.JPG]]Thermal insulation of the digester Digesters require additional thermal insulation in order to reduce heat loss. Commercially available materials can be used for thermal insulation, although in terms of their properties the materials used should be selected to suit the location (close proximity to the ground, etc.) Trapezoidal metal sheeting or wood panelling is used to protect the insulating material against the effects of the weather.
+== Thermal Insulation ==
 <br/>
 == Digester heating<br/> ==

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 <br/>
 === <br/>Plug-flow process<br/> ===
-[[File:Plugflow digester.JPG|thumb|right|180px|Plugflow digester.JPG]]Biogas plants with plug flow – the wet-digestion version is also known as a tank through-flow arrangement – use the expeller effect of fresh substrate infeed to create a plug flow through a digester of round or box section. Mixing transverse to the direction of flow<br/>is usually achieved by paddle shafts or specially designed baffles.<br/>Broadly speaking, there are horizontal and upright plug-flow digesters. Virtually all the digesters used in agricultural plants are of the horizontal type. At this time, upright digesters operating on the plug-flow principle are rare and they are not considered in this<br/>study.<br/>The digesters are usually horizontal steel tanks, factory-built and then delivered to site. This necessitates transport of the digesters to site, which is possible only up to a certain size of tank. Possible uses are as main digesters for small-scale plants or as preliminary digesters for larger plants with stirred-tank reactors (round tanks). Horizontal digesters arranged in batteries for parallel operation can increase throughput. The plug-flow principle reduces the possibility of unintentionally discharging undigested substrate from the reactor, and dwell time can be maintained very reliably for all the material<ref>Jäkel, K.: Management document 'Landwirtschaftliche Biogaserzeugung und -verwertung', Sächsische Landesanstalt für Landwirtschaft, 1998/2002</ref>.
+Biogas plants with plug flow – the wet-digestion version is also known as a tank through-flow arrangement – use the expeller effect of fresh substrate infeed to create a plug flow through a digester of round or box section. Mixing transverse to the direction of flow is usually achieved by paddle shafts or specially designed baffles.<br/>Broadly speaking, there are horizontal and upright plug-flow digesters. Virtually all the digesters used in agricultural plants are of the horizontal type. At this time, upright digesters operating on the plug-flow principle are rare and they are not considered in this study.<br/>
-[[File:Plug flow biogas reactor properties.JPG|frame|center|Plug flow biogas reactor properties.JPG]]
+<br/>
 <br/>
 <br/>
 == Batch processes<br/> ==