Digester Heating - Revision history

Ranisha: /* Influencing Factors */

2016-04-28T06:18:18Z

‎Influencing Factors

Ranisha: /* Combined Heat and Power (CHP) */

2016-03-14T10:14:11Z

‎Combined Heat and Power (CHP)

Wiki Gardener at 10:20, 4 November 2014

2014-11-04T10:20:53Z

Ranisha: /* References */

2014-10-31T13:39:31Z

‎References

Ranisha at 08:49, 20 March 2014

2014-03-20T08:49:32Z

Ranisha at 08:49, 20 March 2014

2014-03-20T08:49:21Z

Ranisha at 15:24, 19 March 2014

2014-03-19T15:24:41Z

Wiki Gardener at 16:11, 30 August 2012

2012-08-30T16:11:56Z

Michel andre at 15:20, 21 February 2011

2011-02-21T15:20:57Z

Michel andre at 10:18, 9 February 2010

2010-02-09T10:18:02Z

@@ Line 73: / Line 73: @@
 |-
 ! 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>
 |}
@@ Line 83: / Line 83: @@
 <br/>
 = Internal and External Heating Systems<br/> =

@@ Line 103: / Line 103: @@
 Combined heat and power (CHP), or cogeneration, refers to the simultaneous generation of both heat and electricity. Depending on the circumstances, a distinction can be drawn between power-led and heat-led CHP plants. The heat-led type should normally be<br/>chosen, because of its higher efficiency. In almost all cases this means using small-scale packaged CHP units with internal combustion engines coupled to a generator. The engines run at a constant speed so that the directly coupled generator can provide electrical energy that is compatible with system frequency. Looking into the future, for driving the generator it will also be possible to use gas microturbines, Stirling engines or fuel cells as alternatives to the conventional pilot ignition gas engines and gas spark ignition engines.
 <br/>
 == Flare Systems ==

@@ Line 7: / Line 7: @@
 <u>In principle, one can differentiate between:</u>
-*'''direct heating''' in the form of steam or hot water, and
+*'''[[Digester Heating#Direct Heating|direct heating]]''' in the form of steam or hot water, and
-*'''indirect heating''' via heat exchanger, whereby the heating medium, usually hot water, imparts heat while not mixing with the substrate
+*'''[[Digester Heating#Indirect Heating|indirect heating]]''' via heat exchanger, whereby the heating medium, usually hot water, imparts heat while not mixing with the substrate
 = Direct Heating =
@@ Line 15: / Line 17: @@
 The injection of hot water raises the water content of the slurry and should only be practiced if such dilution is necessary.
 = Indirect Heating =
@@ Line 27: / Line 31: @@
 While in Northern countries, often a substantial amount of the produced biogas is consumed to provide process energy, in countries with higher temperatures and longer sunshine hours, solar-heated water can be a cost-effective solution for heating. Exposing the site of the biogas plant to sunshine, e.g. by avoiding tree shade, is the simplest method of heating.
 = Costs<br/> =
-{| class="IMGright" cellpadding="10" align="right" border="0" style="width: 239px;"
+{| cellpadding="10" border="0" align="right" class="IMGright" style="width: 100%"
 |-
-| style="width: 211px;" |
+| style="width: 356px" | 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.
-[[File:Digesterheating.jpg|208px|RTENOTITLE]]
+| style="width: 361px" |
+Photo<ref name="Krieg (TBW)">Krieg (TBW)</ref>: Heating system for a biodigester under construction (Germany)[[File:Digesterheating.jpg|none|192px]]
-<small class="IMGLEGEND">'''Photo<ref name="Krieg (TBW)">Krieg (TBW)</ref>: Heating system for a biodigester under construction (Germany)'''</small>
 |}
-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.
 <br/>
@@ Line 55: / Line 60: @@
 <u>Following figures are for heating systems with a heating water temperature difference of 20 K:</u>
-{| cellpadding="5" border="1" style="width: 100%;"
+{| cellpadding="5" border="1" style="width: 100%"
 |-
 ! hydr. retention time
-| style="text-align: center;" | 40 days
+| style="text-align: center" | 40 days
-| style="text-align: center;" | 30 days
+| style="text-align: center" | 30 days
-| style="text-align: center;" | 20 days
+| style="text-align: center" | 20 days
 |-
 ! temperature difference
-| style="text-align: center;" | 20 K
+| style="text-align: center" | 20 K
-| style="text-align: center;" | 20 K
+| style="text-align: center" | 20 K
-| style="text-align: center;" | 20 K
+| style="text-align: center" | 20 K
 |-
 ! heating power
-| style="text-align: center;" | 150 kW/m<sup>3</sup>
+| style="text-align: center" | 150 kW/m<sup>3</sup>
-| style="text-align: center;" | 210 kW/m<sup>3</sup>
+| style="text-align: center" | 210 kW/m<sup>3</sup>
-| style="text-align: center;" | 270 kW/m<sup>3</sup>
+| style="text-align: center" | 270 kW/m<sup>3</sup>
 |}
@@ Line 95: / Line 100: @@
 = Heat Transport in Biogas Plants =
-== CHP ==
+== Combined Heat and Power (CHP) ==
 Combined heat and power (CHP), or cogeneration, refers to the simultaneous generation of both heat and electricity. Depending on the circumstances, a distinction can be drawn between power-led and heat-led CHP plants. The heat-led type should normally be<br/>chosen, because of its higher efficiency. In almost all cases this means using small-scale packaged CHP units with internal combustion engines coupled to a generator. The engines run at a constant speed so that the directly coupled generator can provide electrical energy that is compatible with system frequency. Looking into the future, for driving the generator it will also be possible to use gas microturbines, Stirling engines or fuel cells as alternatives to the conventional pilot ignition gas engines and gas spark ignition engines.
@@ Line 101: / Line 106: @@
 <br/>
-[http://de.slideshare.net/CENERGY/chp-biogas-cogeneration-the-2-g-difference Have a look at this presentation on CHP engines.]
+[http://de.slideshare.net/CENERGY/chp-biogas-cogeneration-the-2-g-difference ►][http://de.slideshare.net/CENERGY/chp-biogas-cogeneration-the-2-g-difference Presentation on CHP engines.]
 <br/>
@@ Line 111: / Line 116: @@
 <br/>
-High Temperature Flares have to be obligatory not only for CDM projects to destroy surplus biogas which cant be utilised due to technical problems or overproduction. Investment costs about 1% of the total investment. (Mang).
+High Temperature Flares have to be obligatory not only for CDM projects to destroy surplus biogas which cant be utilised due to technical problems or overproduction. Investment costs about 1% of the total investment.<ref name="Mang">Mang</ref>
 = References<br/> =
@@ Line 117: / Line 130: @@
 <references />
 [[Category:Biogas]]

← Older revision		Revision as of 13:39, 31 October 2014
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	<references />		<references />

−	~~<br/>~~
−
−	~~[[Construction of a Biogas Plant\|-> Back to "Construction"]]~~
−
−	~~[[Category:Biogas]]~~
	[[Category:Heating]]		[[Category:Heating]]
		+	[[Category:Biogas]]

← Older revision		Revision as of 08:49, 20 March 2014
Line 120:		Line 120:

	[[Construction of a Biogas Plant\|-> Back to "Construction"]]		[[Construction of a Biogas Plant\|-> Back to "Construction"]]
		+
		+	[[Category:Biogas]]
		+	[[Category:Heating]]

@@ Line 92: / Line 92: @@
 <br/>
 = References<br/> =
@@ Line 100: / Line 120: @@
 [[Construction of a Biogas Plant|-> Back to "Construction"]]

@@ Line 1: / Line 1: @@
-To achieve the optimum biogas yield, the anaerobic digestion needs constant environmental conditions, preferably close to the [[Parameters and Process Optimisation for Biogas|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.
+= Overview<br/> =
-{| width="348" cellpadding="10" border="0" align="right" class="IMGright"
+To achieve the optimum biogas yield, the anaerobic digestion needs constant environmental conditions, preferably close to the [[Parameters and Process Optimisation for Biogas|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.
 |-
+|
-[[Image:Digesterheating.jpg]]
+[[File:Digesterheating.jpg|RTENOTITLE]]
-<small class="IMGLEGEND">'''Heating system for a biodigester under construction (Germany)'''<br> </small><small class="IMGSOURCE">''Photo: Krieg (TBW)''</small>
+<small class="IMGLEGEND">'''Photo<ref name="Krieg (TBW)">Krieg (TBW)</ref>: Heating system for a biodigester under construction (Germany)'''</small>
 |}
 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.
-A guiding figure for a digester with a hydraulic retention time of 20 days is 270 W/m<sup>3</sup> digester volume. The increasing of the hydraulic retention time makes it possible to reduce the heating power per volume. With a hydraulic retention time of 40 days the digester needs only 150 W/m<sup>3</sup>.
+= Influencing Factors<br/> =
-Following figures are for heating systems with a heating water temperature difference of 20 K:
+The mean surrounding temperature and it's seasonal variations are very important. Biogas plants without heating system work, therefore, only in warmer regions for the whole year. In regions with extreme temperature variations, for instance in Turkey (hot summer, cold winter), the biogas plant should be built under the stable. Hence the biogas yield would be lower in summer, but constant over the year and at the end higher. Before implementation, at least an approximated average temperature profile and expected extremes over the year should be available for the site.
-{| width="100%" cellpadding="5" border="1"
+A biogas plant with heating system and co-generation can be operated with process energy. Nevertheless the dimensioning of such a heating system is difficult, as the substrate, which has to be heated up, is not homogenous.
 |-
 ! hydr. retention time
 | align="center" | 40 days
 | align="center" | 30 days
 | align="center" | 20 days
 |-
 ! temperature difference
 | align="center" | 20 K
 | align="center" | 20 K
 | align="center" | 20 K
 |-
 ! heating power
 | align="center" | 150 kW/m<sup>3</sup>
 | align="center" | 210 kW/m<sup>3</sup>
 | align="center" | 270 kW/m<sup>3</sup>
 |}
 A heating system located in the digester produces a thermal circulation, which is, especially for non-agitated digesters, very important.
-An indirect energy transfer by heat exchanger is most common. Exceptions are steam injection, liquefying of solid manure with heated water and the heating by pre-aeration.
+Under-floor heating systems have been very popular, as they have no disturbing parts in the digester itself. Due to sedimentation and the resulting worsening of heat transportation into the digester, under-floor heating is no longer recommended. With the growth of digester volumes and the need of bigger heating systems, it is also more difficult to build under-floor heating big enough to provide the necessary heat.
-== Internal and external heating systems  ==
+Heating coils installed at the inner wall of the digester are a rather new practice. Heating coils made out of steel are much more expensive than heating coils out of '''plastic material (PE)'''. Materials developed during the last years make such a system more stable while not increasing the costs of the heating system.
-External heating systems have a forced flow on both sides. Due to the turbulent flow patterns of both media, a very good heat transportation can be reached. Therefore, the surface of the heat exchanger can be comparatively small. Nevertheless those systems cannot be recommended for non-agitated digesters.
+Another option is to construct two digesters connected in series, the first heated, the second unheated. The first digester can be used as sedimentation tank , in which the substrate is heated up. The second digester is well isolated to reduce loss of heat.
-Heating coils installed at the inner wall of the digester are a rather new practice. Heating coils made out of steel are much more expensive than heating coils out of plastic material (PE). Materials developed during the last years make such a system more stable while not increasing the costs of the heating system.
+= References<br/> =
-Another option is to construct two digesters connected in series, the first heated, the second unheated. The first digester can be used as sedimentation tank , in which the substrate is heated up. The second digester is well isolated to reduce loss of heat. <br>
+<references />
-[[Construction of a Biogas Plant|Back to "Construction"]]
+[[Construction of a Biogas Plant|-> Back to "Construction"]]
 [[Category:Biogas]]