production and use of biogÁs - fenix.ciencias.ulisboa.pt · 1859: first biogas ... produção de...
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MESTRADO INTEGRADO EM ENGENHARIA DA ENERGIA E DO AMBIENTE
Aula N
Production and use of
BIOGÁS
Doutor Santino Di Berardino
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Biogas - important data
1776: Discovery of the gas Methane (Alessandro Volta).
1859: First Biogas Application biogás, leprosarium (Bombay)
1895: First European application Street lighting Exeter (England).
1895-1940: Small specific applications
1940-1945: Use in heating, lighting and municipal trucks (Second World War).
1945-1972: Abundance of conventional energy. No use in developed countries. Use in China and India) in small communities
1973 – 2004 - After the first Energetic crises methane from anaerobic digestion is more and more used.
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Biogas Composition
BIOGAS COMPOSITION % Methane (CH4) 55 - 80
Carbon dioxide (CO2) 20 - 40
Hydrogen (H2) 1 - 3
Nytrogen (N2) 0,5 - 2,5
Oxygen (O2) 0,1 - 1
Hydrogen sulphide (H2S) 0,1 - 0,5
Amonia (NH3) 0,1 - 0,5
Carbon Monoxide (CO) 0 - 0,1
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.PARÂMETROS
ANALISADOS
ETAR de Loures
(Lamas )
Suinicultura Efluente rico
em sulfatos
Fábrica de
Lacticínios
CH4 (%)
CO2 (%)
H2S (mg/l)
73
27
0,9
80
20
3,4
55
38
70000
93
7
--
Gas Composition-Portuguese Digesters
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Biogas Characteristics
Not visible gas
Low toxicity. It contains, normally, low percentage of Carbon monoxide and sulphide
Heat value between 5000 to 7 000 kcal/m3
depending on CO2 percentage
Lower explosion risks than butane or propane due to low density
Corrosive, depending on H2S content
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Características do Biogás
Componente Gás Natural
Gás de aterro
Gás de ETAR
Gás Agropecuária
Metano (%)
90-99
40-55
50-65
50-80
CO2 (%)
0-5
35-50
35-50
20-50
H2S (ppmv)
< 15
< 200
500-3000
< 3000
Poder Calorífico
(Kcal/m3)
9300-10300
4000-5500
4000-6500
5000-8000
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Biogas – Actual and Future Use
Biogas was essentially produced for environmental purposes - Treatment of organic residues (Industrial, domestic, agricultural solid wastes etc).
Methane from anaerobic digestion is a renewable energy and a clean and economic domestic combustible.
Today can play a role more important, also agricultural crop, energetic cultures and forest residues can be used to feed digesters, for energy production.
The amount of methane gas produced varies with the amount of organic waste fed to the digester
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Impact of biogas
Biogas energy has interesting aspects, as it is a renewable source and contributes to the reduction of fuel imports. Methane gas is the cleanest and most economical domestic fuel.
At the national level biogas can be produced for environmental reasons and/or for energetic purposes. The byproduct of waste and effluent treatment.
When is intensively produced, it can only replace more than 10 % of natural gas consumption.
However, it is a virtually inexhaustible source when, in addition to being generated from waste, sewage and other organic waste, it is produced from plant crops planted for that purpose and constitutes an energy alternative
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Prevision
In the current phase of the world economy, the alternative ofrenewable sources has short, medium and long term prospectsfrankly positive.
The global energy crisis has highlighted the energy vulnerabilityof the European Union, which relies heavily on oil in the MiddleEast, the most explosive area in the world.
It is therefore essential to diversify the sources and nature offuels in order to ensure survival, development and continuity,and to increase research into alternative sources of energy, inthe substitution of oil and oil products.
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Biogas Production process
Energia da biomassa
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Use of products
Energia da biomassa
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Biomass gasification
Energia da biomassa
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Power to methane (P2G or P2G)
Energia da biomassa
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Scheme of a agricultural biogas plant
15Energia da biomassa
16Energia da biomassa
17Energia da biomassa
18Energia da biomassa
19Energia da biomassa
20Energia da biomassa
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Biogas Plants In Europe
Energia da biomassa
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Estimate biogas production with COD
Chemical/Oxygen Demand
•Measures amount of oxygen required to oxidiseorganic matter
•Used widely in aerobic water treatment
•Characterizes wastewaters and organic feedstocks
•Estimates energy content of substrate
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Biogas Production-calculation
COD is used to evaluate the Methane production, according to relation:
CH4 + O2 = CO2 + H2 O
At 0ºC e a 1 atmosphere 1 kg of COD (to oxidizeMethane) corresponde a 0,35 m3 de CH4.
Or 1 mol of Methane takes 64 g of COD to be oxidised
COD
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Net COD levels for aerobic and anaerobic wastewater treatment
(Quaiser, 2013)
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Methane production from COD
If you Know the COD of your material you can estimate methane production.
COD = COD biodegradable + COD not biodegradable
COD biodegradable generates methane, neworganisms and allows respiration
Energia da biomassa
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Production of methane from complete anaerobic degradation of 1 kg of COD under standard conditions:
1 – COD equivalent to CH4
CH4 + 2O2 ------------------> CO2 + 2H2O16 g e 64g => 16 g CH4 ~ 64 g O2 (CQO)
=> 1 g CH4 ~ 64/16 = 4 g CQO ------------ (1)
2: Conversion of CH4 in equivalent volumeAccording to the gas laws, 1 mole of gas at Standard Temperature and Pressure (TPS occupies a volume of 22.4 L. =>1 Mole CH4 ~
22.4 L CH4
=> 16 g CH4 ~ 22.4 L CH4
=> 1 g CH4 ~ 22.4/16 = 1.4 L CH4 -- (2)
Methane Production from COD
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3 – Production of CH4 por unit of removed COD
From eq. (1) and eq. (2),,=> 1 g CH4 ~ 4 g COD ~ 1.4 L CH4
=> 4 g COD ~ 1.4 L CH4
=> 1 g COD ~ 1.4/4 = 0.35 LCH4
or 1 Kg COD ~ 0.35 m3 CH4 ----------- (3)
Anaerobic degradation of 1 Kg de COD produces 0.35 m3
CH4 a TPS excluding the losses and the growth of new cellules.
.
Methane Production from COD
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Total Solids, Volatile Solids
Total Solids (TS)= Dry weight of substrate
Volatile Solids (VS)= organic matter. Combustible (weight of solids volatile at a temperature of 550° C) proportion of TS,
Non-volatile Solids (Ash) = Minerals etc. left over from combustion
Methane production is often evaluated from the amount of SV in a given substrate
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Production of Volatile Solids
Cow = 10 kg VS por dia
Swine = 8.5 kg VS por dia
Chicken = 12 kg VS por dia
(for 1000 kg of living weight)
Approximately just 40-60% of VS in converted into biogas (biodegradable fraction), dependin on the substrate and digestion type and regimen.
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Gas production from some compounds
Fats have the major energy potential.
Than Proteins and carbo-hydrate
Matter CH4 Specific production (m3/kg SV)
Carbo-hidrates 0,5
Proteins 0,7
Lipids 1,2
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Biogas Yield
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Biogas production-mixed wastes
Composição Carbo-hidrate
Proteína Lípidos Produtividade de gás
(m3/kg)
Resíduos com alta produção de gás
12% 38% 50% 1,020
Resíduos com média produção de gás
15% 54% 44% 0,980
Resíduos com baixa produção de gás
24% 50% 26% 0,880
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Animal Nº Produção Biogás (m3/(animal.dia)
vacas 1 1,3
bezerros 1,5 0,85
suinos 9,6 0,135
homens 65 0,02
galinhas 150 0,009
Equivalence of biogas production in wastes
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Energy and fertilizing property of cropBiomassa Agrícola produzível Colheita por M O Produção CH4 Azoto
hectare metano[t/ha/a] (%) [Nm³/kgMO) (%) kgN/t
Alfa-alfa erba medica 30 30 290 56 7Cereais-grãos 1 84,39 365 53 12Silagem cereais -toda a planta 35 35,34 260 52,5 4Silagem erva de cobertura 25 30,1 330 56 8Milho-grãos secos 11 85,26 365 52,8 10Milho-grãos molhados 15 58,8 372 53 7Silagem de milho 45 31,68 330 52,5 3stelo do milho 1 61,92 468 52 0Ensilado de feijões 30 37,6 265 54,6 9Silagem de beterraba 90 10 468 53 1,7Silagem de ervilhas 30 29,9 294 55,8 0Silagem de beterraba açucareira 50 20,5 400 53 1,6Silagem de forragem ervas 35 33,82 330 54 7,5Podas de verdes 15 55 80 53 0segala não madura-intercalar 25 22,25 310 54 4Culturas intercalares gerais 5 32 300 54 2,5Aveia -graõs 6 84,13 320 54,1 12Silagem de aveia - 18 29,7 320 53,5 4,2Colza 3,5 83,6 500 65,7 -Silagem de colza 11 13,12 380 55,5 3,2trifoglio vermelho silagem 30 26,1 300 55,3 5,8segala-grãos 7 85,26 365 52 11Silagem ervas segala (lolium) 35 30,1 320 54,6 6,25Palha 6 80,84 200 51 3,5Silagem de erva do sudan 50 20,5 254 52 3Ensilado de girassol (planta) 9 20,1 230 55 3,5Tritical grãos 8 85,76 360 52,4 12Silagem de tritical inteira 20 31,7 300 53 6,3Silagem de rape geral 60 12,75 365 54 2,2Grãos de milho 7 85,26 369 52,75 13,5Ensilado de cevada (toda a planta) 32 35 300 53 4,4Mistura milho-tutoli 20 59 350 52,7 Azoto
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Energy and fertilizing potential of some crops
Prod. Espec.t/ha
Prod espe. Biogásm3/t
Prod biogás(m3/ha/dia)
Azoto fixado(kg/ha/ano)
Aveia 40 96 12 200
Tritical 30 110 9 225
Luzerna 50 90 12 219
Alfa-alfa 35 87 8 210
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Evolution of biogás production
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Biogas from some substrates
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Tipo de resíduo Matéria orgânica (ton/dia)
Lixos urbanos 4 000
Lamas de ETAR’s 625
Excreta de suiniculturas 750
Excreta de bovinos 2 300
Excreta de aviários 400
TOTAL 8 075
ESPÉCIE 1989
Bovinos 1 401 340
Ovinos 2 921 113
Caprinos 719 755
Suínos 2 423 957
Cavalar 36 246
Muares 37 129
Asininos 77 515
Perus 1 168 243
Galináceos 28 320 020
Potencial em Portugal
3939
Biogas Use
Domestic use (Cooking, lighting etc.)
Heating
Supplement to natural gas
Combined Heat Power (CHP)
Vehicle fuel
Fuel Cells
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•Requirements to remove gaseous components depends the biogas utilisation.
•Basic compounds to remove are: Water, Suspended Solids H2S and, eventually, CO2
Biogas Treatment
4141
Biogas Treatment Technologies
Many technologies are available to remove specific compounds
COMPOUND TO REMOVE
TECNOLOGY PRINCIPLE
Water Demister Physic Cyclone separator Physic
Moisture trap Physic
Water tap Physic
Adsorption to silica Physic
Glycol drying unit Physic
H2S Air oxygen dosing Biologic FeCl3 dosing to digester slurry chemical Adsorption to Fe2O3 pellets Physico-chemical Absorption with caustic solution Physico-chemical Absorption with iron solution Physico-chemical Absorption closed loop systems Physico-chemical Membrane separation Physic Biological filters Biologic Activated carbon Physico-chemical Molecular sieves Physic
CO2 Pressure swing adsorption Physico-chemical Membrane separation Physic Absorption techniques Physico-chemical
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Power Equivalences of Biogas
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Combustível Poder calorífico(kCal/m3)
Biogás 5 130
Biogás purificado 7 600
Gás de cidade 4 000
Propano 22 000
Butano 11 000
Gasóleo, fuel-óleo, etc. 8 545
Gasolina 7 280
Carvão 6 600
Electricidade 860 kcal/kWh
Metano puro 8 500
Gás natural 9 400-19 500
Poderes caloríficos
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Combustível Quantidades Gás de cidade 1,28 m3
Propano 0,23 m3
1 m3 de biogás 0,46 kg
equivale a: Butano 0,183 m3
0,475 kg
Gasóleo e fuel-óleo 0,6 l
Álcool 1,3 l
Gasolina 0,7 l
Electricidade 6 kWh
Equivalence between biogas and
commercial fuels
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Carbon dioxide
Carbon dioxide (CO2) is an inert, colorless, odorless, heavier gas than air. It is medically toxic, asphyxiant, and has a standard Occupational Exposure (OES) of 5,000 ppm. The high CO2 content in the biogas leads to a low calorific value.
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Hydrogen sulphide (H2S)
It is the most dangerous gas contained in Biogas.
It is a colorless gas, heavier than air
It is very toxic to microorganisms, plants and man even at low levels.
It smells very strongly of rotten eggs.
It constitutes the form of the sulfur energetically more stable and is very reactive (Widdel, 1988).
The limiting concentration of the odor is only 0.00047 ppm (EPA, design manual 625/1, 1985).
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Water dissociation
At high concentrations does not stink. It causes death in man from concentrations of 300 ppm in the air.
Due to its toxic properties, hydrogen sulfide has a standard occupational exposure (OES) of 10 ppm.
Hydrogen sulfide is a weak, sparingly soluble acid in water, where it is dissociated into the ionic forms H2S, HS-, S = according to the following reactions
(H2S (l) HS- + H+
HS- S= + H+
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Dissociation of H2S in water
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Toxicity
The toxicity of the sulfiphide depends essentially on its ionic form which can pass through the cell membrane (Speece, 1983).
The relative amount of molecular hydrogen sulphide and its ionic form depends on the pH value. At pH = 7 the molecular hydrogen sulfide is about 50%.
The molecular form prevails in the acidic form and, at pH = 6, about 90% of all the hydrogen sulphide is in the molecular form that escapes into the gas phase, giving rise to a toxic gas with bad smell. Above a pH of 8-9, practically all of the dissolved hydrogen sulfide is present in the ionic form.
At neutral pH, about 50% of the dissolved hydrogen sulfide is present in the form of H2 S
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Solubility
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Temperature (ºC) Solubility (mg S/l)
0 6648
5 5646
10 4810
15 4150
20 3618
25 3175
30 2806
35 2491
40 2221
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Amonia (NH3)
.
O (NH3) is a more aggressive and tear gas lighter in air with an OESof 10 ppm. It is generally in very weak concentrations, it can becorrosive to copper. Nitrogen oxides released during combustion(NOx) are also toxic
The water vapor present in the gas becomes corrosive incombination with NH3, CO2 and especially the H2S of the biogas.The maximum content of water present in the biogas depends onthe temperature, being in the values of saturation in the gas ofexit of the digester. The cooling of the biogas allows itscondensation and also of hydrogen sulphide, which becomesmore soluble at low temperatures.
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Carbon Monoxide
Biogas, under normal production conditions, has a low carbon monoxide content (less than 0.1%) and is non-toxic, in contrast to, for example, city gas, which accounts for about 20% of this gas, is fatal .
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Biogas Properties.typical composition
is not normally toxic due to the reduced content ofcarbon monoxide and hydrogen sulphide
It has corrosive power and characteristic odor (due tothe sulfidric), being very aggressive for equipment withcomponents in copper, brass or steel.
Due to the presence of methane, a combustible gas withits lower calorific value (P.C.I.) is about 5500 kcal / m3,when the proportion in methane is approximately 60%.
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Properties
The other gases contained in the biogas do not pose problems in terms of toxicity or harmfulness.
Carbon dioxide, in a significant proportion (35%), occupies a perfectly dispensable volume and requires, if not suppressed, an increase in storage capacities.
Water vapor can be corrosive to the pipes after condensation.
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Pipes and accessories
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Water traps
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Gas dome details
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Biogas storage
It compensates for fluctuations between the production and use of biogas, allowing continuous operation
It allows to use the motors in hours of greater price
It consists of a reservoir capable of varying the storage volume and pressures slightly higher than atmospheric
Fixed volume reservoirs are generally hazardous because they allow air to infiltrate during times of low pressure and form explosive mixtures of ar-methane.
Nowadays, for reasons of cost, flexible gasometers are used in plastic,
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Armazenamento do biogás
The maintenance of the exercise pressure in these units is done by compression or by structures with weights that compress the reservoirs.
As an alternative, storage medium (about 40 kg / cm 2) or high pressure (200-300 kg / cm 2) can be adopted, little applied for reasons of cost.
The compression of the gas implies loss of energy, which is of the order of 10% in the case of medium pressures and 20% in the high pressures.
To improve compression yield and to avoid corrosion it is generally advantageous to purify the gas by eliminating water, carbon dioxide and hydrogen sulphide.
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Gasholders
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Low Pressure Biogas Storage
There are many possibilities to store Biogas at low pressure (<50 mBar)
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Floating gasometer
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Double chamber gasholder
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Biogas treatment layout for biomethane
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Membrane purification
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Heat balance of a cogeneration system
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Uso do Biogás
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Uso Característica Quantidade degás (m3/h)
Iluminação Lâmpada de 100 velas 0,13Lâmpada "Amanchon" 0,017
Cozinhar Queimador de 5 cm 0,330
10 cm 0,450
15 cm 0,650Por pessoa/dia 0,34-0,42
Aquecimento EsquentadorPor pessoa/m3/h 0,34-0,42Esquentador 125 kCal/mm 1,7Esquentador 320 kCal/mm 4,2Caldeira para 200 l 0,3Caldeira para 200 l comelevação até 85C
2,5
Caldeira (n = 0,15) 10 000kCal/h
2,3
Irradiador para aquecervolume de 100 m
1
Refrigeração Refrigerador (por 1 m2 deparede)
0,008
Incubador Por m3 de ar 0,05 -0,07
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Biogas Utilisation
Microturbines
Fuel Cells
Motores de
C.I.
Gas turbine
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MOTOR GERADOR
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Biogas Consume
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Tipo de Uso Consumo
Combustão 0,45 m3 por CV/h;
0,31 m3 por CV/h (biogás purificado)
Motor agasolina
1,35 - 1,9 m3 por dm3 de cilindrada e por hora
1,2 m3 por dm3 de cilindrada e por hora(biogás purificado)
Motor diesel 1,5 - 2 m3 por dm3 de cilindrada e por hora
1,1 - 1,4 m3 por dm3 de cilindrada e por hora(biogás purificado)
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Biogas burning-emissions
Item
Tocha
Motor de C.I.
Turbina a Gás
Micro- Turbina
Fuel Cells
Heat Rate (Btu/kwhr)
NA
10-11,000
10-12,000
12-13,000
9-10,000
NOx lb/MMBtu
0.05
0.22
0.07
0.02
0.0005
CO lb/MMBtu
0.19
0.67
0.10
0.10
0.002
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Gas Burners
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Benefits from Biogas
Benefits of producing electricity in isolated areas
Environmental Benefits
Reduction of soil pollution
Reduction of methane emissions
Reduction of Nox Emissions in Quantity Dependent on Device
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Bibliography
•(USEPA (1979). Sludge Treatment and Disposal. U.S. Environmental Protection Agency. Washington, DC.
• Stronach S.M., Rudd T. and Lester J.N. Anaerobic digestion processes in industrial wastewater treatment, Springer-Verlag, Berlin,1986.
• Wheatley A., Anaerobic Digestion: a waste treatment technology, from Critical Reports on Applied Chemistry vol 31, Published for SCI by Elsevier applied science, 1990
• Zehnder A. J. B., Biology of Anaerobic Microorganisms,Agricultural University , Wageningen, The Netherlands, John Wiley and Sons Inc, 1988.
• Henze M. and Harremoes P., Anaerobic treatment of wastewater in fixed film reactors- A literature review, wat.Sci.Techn.,vol15,1983,1-101
• Tchobanoglous, G.; “Wastewater Engineering - Treatment, Disposal, Reuse”; Metcalf & Eddy, Inc., 3rd Edition, McGraw-Hill Publishing Company, 1991 ISBN 0-07-100824-1.a)
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Internet resources
• www.britishbiogen.co.uk/gpg/adgpg/adgpgfront.htm
• www.adnett.org/
• www.uasb.org/SCIENCE/data_page_biodegradability.htm
• www.epa.gov/agstar/library/
• www.eere.energy.gov/consumerinfo/refbriefs/ab5.html
• www.ias.unu.edu/proceedings/icibs/
• www.bioenergyupdate.com/
• www.biogas.ch/
• www.cogen.org/
• www.energiasrenovaveis.com/
• www.novaenergie.ch/iea-bioenergy-task37/Dokumente/Biogas%20upgrading.pdf
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