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Méthanisation: Processus, condition,étapes..
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Dimensionnement du modele: Fonctionnement : 91% environ 8000 heures par an. Quantité de matieres premieres: 12 060 tonnes. Quantité de biogaz Produit : 916 822 m3/an(54.3% de méthane). Quantité de digestat : 10 869 m3. Eng; Model sizing: Operation: 91% approximately 8000 hours per year. Quantity of raw materials: 12,060 tons. Quantity of biogas produced: 916,822 m3/year (54.3% methane). Quantity of digestate: 10,869 m3. Bilan des matieres: 
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Systemes de production du biogaz:
les intrants peuvent etre de deux types :
Les intrants solides ( fumiers, matieres vegetales) Les intrants liquides sont pompés vers le digesteur et devont etre agitée. Les substrats solides sont introduits dans le digesteur a l'aide d'un dispositif specialement concu. Ce dispositif a une capacité suffisante pour contennir l'équivalent d'un a deux jours d'intrants. Une isolation des parois diminue les besoins en chauffage du systeme. Les substrats sint infinement melangé pour éviter la formation des croutes et pour favoriser l'expulsion du gaz. Eng: Inputs can be of two types: EVEB liquid inputs Solid inputs (manure, plant matter) Liquid inputs are pumped to the digester and must be agitated. Solid substrates are introduced into the digester using a specially designed device. This device has sufficient capacity to contain the equivalent of one to two days of inputs. Insulation of the walls reduces the heating needs of the system. The substrates are finely mixed to avoid the formation of crusts and to favor the expulsion of gas.
Digesteur: Systeme de pompage pour introduire les matieres liquides dans le digesteur . Eng:
Digester: Pumping system to introduce liquid materials into the digester.A 160mm diameter polyethylene pipe will be connected to the pump and the digester to introduce the solid inputs. Une canalisation en polyéthyléne de diametre 160mm sera raccordée a la pompe et au digesteur pour introduire les intrants solides. Le systeme de brassage: agitateur a pales 4 pales placées sur un axe en rotation génerent des courants de sens différent a haute teneur en matiere seche et empeche ainsi la formation de couche de surface. La faible vitesse de rotation permet de preserver la population bacterienne. Eng: The stirring system: paddle stirrer 4 blades placed on a rotating axis generate currents in different directions with a high content of dry matter and thus prevent the formation of a surface layer. The low rotation speed preserves the bacterial population.
La membrane pour le stockage du biogaz:2mm d'épaisseur EPDM En caoutchouc EPDM de haute qualité, élastique, résistante (aux UV et a l'Ozone). Eng: Membrane for biogas storage:2mm thick EPDM In high quality EPDM rubber, elastic, resistant (to UV and Ozone).
maintenir le biogaz Le systéme de chauffage des fosses de digestion: Réseau de tubes en matiere composite fixée sur le paroi interne de la fosse . Le passage d'eau chaude permet de maintenir le digestat a la température adéquate. Eng: Digestion pit heating system: Network of tubes in composite material fixed on the internal wall of the pit. The passage of hot water keeps the digestate at the right temperature.
les fosses de digestion (digesteur): Fosse en béton armé avec un pilier central supportant une charpente en bois (supporte la membrane de stockage de biogaz EPDM, et offre une grande surface de colonisation pour des bacteries qui transforment l'hydrogéne sulfuré H2S en soufre qui se dépose sur la charpente en bois). Eng: Reinforced concrete pit with a central pillar supporting a wooden frame (supports the EPDM biogas storage membrane, and offers a large colonization surface for bacteria that transform hydrogen sulphide H2S into sulfur which is deposited on the wooden frame ).
Un diamétre de dsigesteur de 19 m permet en temps de retention hydraulique de 44.1 jours - Durée de production du méthane:Diametre= 19m => 44.1 jours. Charge maximale = 3.7kg MO/m3/jour Eng: A digester diameter of 19 m allows a hydraulic retention time of 44.1 days - Duration of methane production: Diameter= 19m => 44.1 days. Maximum load = 3.7kg MO/m3/day
Dimensions: Φ=19m, h= 6m Volume brut : 1701m3 Volume net = 1 474 m3 Eng: Dimensions: Φ=19m, h=6m Gross volume: 1701m3 Net volume = 1,474 m3
étapes:
1) Hydrolyse :
2) Acidogénese:
3)Acetogenese:
4)La methanogenese:
Il est necessaire de chauffer le méthane: -Zone mésophile:35° -Zone thermophile: 55 a 60°C Note bien: Le biogaz diminue l'effet de serre. Limite la nuissance de l'environnement. Le digestat: Desodoris, nuissance olfactives sont detruites dans le digesteur. Sa valeur fertilisants est ameliree, la quantité en nutriments sont conserves mais l'azote intialement organique se retrouve sous forme ammoniacales. Il est donc assimilable pour les plantes. Cet épandage améliore l'activité microbienne et la respiration des sols par rapport aux epandages de fumiers ou lisiers. L'epandage est réalisée grace a un pendillard. It is necessary to heat methane: -Mesophilic zone: 35° - Thermophilic zone: 55 to 60°C Note well: Biogas reduces the greenhouse effect. Limits environmental damage. The digestate: Deodoris, olfactory nuisance are destroyed in the digester. Its fertilizer value is improved, the quantity of nutrients is preserved but the initially organic nitrogen is found in ammoniacal form. It is therefore assimilable for plants. This spreading improves microbial activity and soil respiration compared to spreading manure or slurry. Spreading is carried out using a dropper.
1m3 =9Kwh Vt=π(r)2.H=π(1500)2.2000=14.130 ρeau=m/v m=ρ.v=1*7065=7.065kg ρw=m/v m=ρ*v=1.5*6065kg mt=mw=ml=7065=10600=17.665kg Caracteristiques de l'agitateur Gas separation:
Physical Scrubbing: -Wprking principe *CO2 is more soluble than CH4 according to Henry's law. *Raw biogas flow through a counter flow of a liquid in a column. *Liquid absorb CO2 leaving biogas with high content of CH4. -Type of liquid: *Water for water scrubbing. *Ployethylene glycol(PEG)/ selexol and Genenrob for organic scrubbing. --System upgrading: *Absorption column filled with packing material to increase mass transfer. *Flash tank installed to recover trace of CH4. *Water/PEG regeneration to remove CO2 for reuse purpose. -Advantages: *Simple process *High methane purity *Less methane loss. *Low operation and maintenance cost. -Disadvantages: *Required huge amount of water. *High energy needed *Chances of biological contamination. *Required external heat.
2) Cryogenic separation: -Working principe: *Different gases condense at different temperature-pressure domains. *Boiling point of CO2 was higher than the CH4 thus allowing the separation. *Biomethane produced by gradued decrease of temperature and compressing the biogaz. *Equipement: compressor-turbine-heat exchanger and cooler. -Post treatement: *Final product is in accordance with the quality standards gor liquified natural Gas (LNG). *Further cooling for purification will produced liquid Biomethane(LBM). -Advantages: *High gaz quality *Low methane losses *Environmentally friendlly *Produce LBM with low extre-energy -Disadvantages: *High investment operatonal cost *Pre-treatment needed *High energy required for cooling *Technology is still under development.
3) Membrane seoaration: -Working principale: *Separation of biogas components using membrane as permeable material. *The selection of permeability propreties of membrane is crucial. *Ascending order of permeation rate: CH4, CO2, H2S,N2 and H2O. -Separation techniques: -Gas-gas separation(dry) *H2S and oil vapours were first removed. Biogas is pressurized and injected into membrane. -Gas-liquid separation:(wet) *Liquid and gases separated by membrane. *Impurity is the gases absorbed by the counter current flows of liquid. -Increasing efficiency: *Enhanced the CH4 purity by using two or three stage performance. *Ideal membrane must have high permeability difference between CO2 and CH4. -Advantages: *Environmentally friendly *Low energy comsumption *Low cost *Simple process. -Disadvantades: *Low membrane selectivity *Pre-treatment necessary *Low CH4 purity
Requirements: Physical srubbing -Polyethylene glycol - Selexol and Genesorb Chemical Scrubbing -Mono ethanol amine or di-methyl ethanol amine -Alkaline solution -Different type of solution resulting in diffrenet CH4 purity
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Systéme de brassage; agitateur a 4 pales
Membrane en Caoutchouc pour
Systéme de chauffage de digesteur
Charpente en bois
