Thermo and Bio-chemical Conversion Technologies
OLADE
ALFREDO BARRIGA, PHD
ESPOL – ECUADORSeptember 2011
Biomass Natural Cycle
Rice Husks Cane Bagasse Oil palm husks
Biomass in Ecuador
RESIDUAL BIOMASS FROM PLANTS
BIOMASSAnimal or vegetal
MoistObtained with moisture
content above 60%
DryObtained with moisture
content below 60%
Physical Precesses Biological Processes
Thermochemical Processes
CombustionPyrolisisGasificationLiquefaction
Fermentation (alcohol)Bacterian digestion
Drying-CompacChoppingMechanical Press
PATHS FOR UTILIZATION OF BIOMASS FOR ENERGY
Typical residual Biomass Crop residues, stalks and branches, etc.
Bagasse from the process of extracting sugar cane juice (sugar production, alcohol, etc.).
Rice hulls.
Shell and oil palm bundle branches.
Remains of wood industrialization bark, side cutting damaged planks, etc.
Sawdust and wood shavings in a production of wooden elements.
Biomass Characteristics Bagasse
Chips from Olive tree(db) Cotton(db) Pine bark(db) Oak bark(db)
Redwood bark (db)
Ultimate analysis Carbon 23,4 49,52 47,03 53,40 49,70 51,90Hydrogen 2,8 5,90 5,42 5,60 5,40 5,10Nitrogen 0,1 0,39 1,04 0,10 0,10 0,10Sulphur 0,6 <0,05 0,13 0,10 0,20 0,10Ashes 1,7 1,74 5,37 2,90 5,30 0,40Oxygen 20,0 42,45 41,01 37,90 39,30 42,40
Immediate analysis Moisture 52,00 -- -- -- -- --Volatile 40,20 81,79 73,78 72,9 76,00 72,60Fixed Carbon 6,10 16,47 20,85 24,2 18,70 27,00Ashes 1,70 1,74 5,37 2,90 5,30 0,40 HHV (kcal/kg) 2 224 4 610 4 297 5 021 4 654 4 643
Ash Analysis SiO2 25,21 39,00 11,10 14,30Al2O3 6,59 14,0 0,10 4,00Fe2O3 2,98 3,0 3,30 3,50P2O5 2,61 -- -- --SO3 2,36 0,30 2,00 7,40
Biofuels Comparison Chart
Gasoil Fuel Oil Natural Gas CoalBiomass (typical)
Ultimate analysis Carbon 86,0 84,6 72,8 75,8 50,0Hydrogen 11,1 9,7 22,6 5,1 5,5Nitrogen 1,0 1,0 4,6 1,5 1,0Sulphur 0,8 1,5 0,0 1,6 <0,2Ashes 0,1 0,5 0,0 5,0 2,0-5,0Oxygen 1,0 2,7 0,0 8,2 40,0
Proximate analysis Moisture 1,0 1,5 0,0 5,0 variableVolatile 35,0 65,0Fixed Carbon 50,0 20,0Ashes 10,0 2,0-5,0 HHV (kcal/kg) 10 300 10 100 12 450 7 500 4 500
Thermochemical processes (pyrolysis, gasification and combustion) consist on the organic components decomposition of biomass at high temperatures.
Main thermo-chemical processes are:CombustionPyrolysisGasification
THERMO-CHEMICAL PROCESSES
Thermal Decomposition Processes for Biomass
LIGNOCELLULOSE IN AIR SCHEME COMBUSTION
- DRYING
- ROASTING
- PYROLYSIS
COMBUSTION
AIR
ASH
FLAME
CHAR
WOOD
VOLATILE
CHARCOAL
PyrolysisIs the incomplete combustion of biomass at elevated temperatures in the absence of oxygen, around 500 degrees celsius. Charcoal is obtained by heating wood until its complete carbonization occurs, leaving only carbon and inorganic ash. In many parts of the world, charcoal is still produced by burning a pile of wood that has been mostly covered with mud or bricks during a lot of time, even days to relatively low temperatures (350 °C)
BIOMASS + HEAT Carbon + Liquid + gaseous
Gaseous fuel combustion (Methane)
Liquid fuel combustion (fuel oil)
Biomass fuel combustion (wood)
Technology Residence
time
Maximum Temperature
(°C) Main
Product
Calorific value(Dry basis)
Carbonization Hours-days 300-500 Charcoal 30 MJ/ Kg
Slow 5-30 min. 400-600
Bio-óil. Coal. Gas
20 MJ/ Kg 30 MJ/ Kg 5-10 MJ/Nm3
Fast ≤1s 450-600 Coal Gas
30MJ/ Kg 10-20 MJ/Nm3
Fast ≤1s 700-900 CoalGas
30 MJ/ Kg 15-20 MJ/Nm3
Pyrolysis Technologies
When biomass is subjected to pyrolysis, products obtained are such as:
Solid (Charcoal)Liquid (Bio-fuel oil) (Bio-oil)Gases (Gaseous fuel with low or medium calorific value)
Basic products in pyrolysis depend on:•Reactor temperature.•Heating rate related to the particle size.•Residence time of products inside reactor.•Technology and its operational parameters.
COMBUSTION
Combustion is a process in which biomass is oxidized to carbon dioxide (CO2), water. The overall equation of combustion reaction is the reverse of photosynthesis.
BIOMASS + O2 CO2 + H2O + HEAT + (Other species)*
* CO, HC, Soot, Oxidized minerals , tar, moisture and other
Types of Biomass Combustion Chamber
Main combustion technologies for biomass
Biomass Combustion Technologies
Grate combustion.of the following types: fixed bed, horizontal and inclined grate, mobile grate and vibrating grate.
Fluidized bed: is based on the combustion reaction in a fluidized bed in which the fuel particles move similarly to those of a liquid.
Moving Grate
Fuente: Manual de Energía Térmica con biomasa
Inclined Grate Furnace
Fluidized bubbling bed furnace
Operating Temperature in ChamberOperating temperature depends on several factors such as:
Fuel Calorific Value.
Biomass moisture.
Excess Air Percentage.
Heat transfer to the chamber walls.
Heat loss to the outside.
Combustion completion.
Humidity effects on biomass calorific value
Fluid Dynamic Effects of Particles
Particles to fall freely in a fluid environment (air or combustion gases for example) fall at a rate dependent upon fluid forces (drag).
These drag forces depend on the viscosity fluid, and the particle shape. In the case of irregular shaped particles, as are most of the biomass "chopped" as bagasse, husks, etc.. the drag coefficient depends on the wake formed by the passage downstream of the particle.
Influx of chipped biomass through inlet
Flame Shape in Biomass Combustion
Flame shape depends on:
Ratio of gas-phase combustion of pyrolysis products to rate of burning of the carbonaceous residue.
Relative position of the biomass at the time of combustion.
Geometry and distribution of air supply: from below the grate, and above it.
Presence of vortex effects which are induced by tangential entry of air.
Process Energetic content on initial
biomass (%)
Intermediate Fuel Heat Electricity or
mechanic work
Combustion 65-95 20-35 Pyrolysis
(Carbonization) 70-75 60-70 22-30
Gasification 65-80 22-27
Efficiency of various thermal processes with Biomass
The main problems of residual biomass operation are:
Formation of agglomerates and slag on the grate (slagging).
Fouling on interior surfaces.
Metal surfaces corrosion.
Industrial Combustion Problems of Residual Biomass
Slag formed in Biomass Combustion
Fouling on boiler tubes
Control and EmissionsCombustion plants produce effluent gases, solids and liquids. Particles are one of the most important emissions on biomass combustion.
GAS TREATMENT SYSTEMS
•CYCLONIC SYSTEMS•BAG FILTERS•WET SCRUBBER•ELECTROSTATIC FILTERS
BIOGAS
Biogas is the gaseous product of anaerobic digestion of organic waste under appropriate conditions of temperature, dilution, residence time, and others. It comprises approximately 60% of CH4 and CO2 rest, with small amounts of other gases. Organic substrates are used such as manure mixed with straw and agricultural residues and agro-industrial production.
BIOGAS GENERATION PROCESS
The raw material for biogas generation can be processed in either batch or semi continuous production. Reactors are built using metal, plastic or masonry components.
Gas begins to appear a short time after initial loading of the reactor, first slowly, and not always generating combustible gases., Methane starts to appear under the right conditions, along with carbon dioxide in the form of biogas.
The biogas generated is stored within the digester or in a separate container (GASHOLDER) which can be use outside the digester. The effluent contains some of the organic compounds and nutrients, which can be used as fertilizer. It also forms some bottom sludge, which need to be removed periodically.
Stage 1•Hydrolysis or
liquefaction•The hydrolytic
enzymes produced by bacteria. Hydrolysis is therefore the conversion of polymers into their monomers.
Stage 2•Acido-genesis•The hydrolysis
products are converted into organic acids such as acetic, propionic and butyric acids.
Stage 3•Aceto-genesis•The products
concerned are converted to acetic acid, hydrogen and carbon dioxide.
Stage 4•Methano-genesis•At this stage
metabolic CH4 is generated from acetic acid or mixtures of H2 and CO2, may also be formed from other substrates such as formic acid and methanol.
STEPS IN THE PRODUCTION OF BIOGAS
Flash Point 700 º C (350 º C Diesel, gasoline and propane close to 500 º C).
The flame temperature reaches 870 º C.
Biogas typically contains:
60% methane (CH4)40% of carbon dioxide (CO2).
The longer the retention time, the higher the methane content, and that the calorific value.
CHARACTERICTICS OF BIOGAS
•Daily amount of total solids.
•Retention time.
•Specific production of gas per day, depending on the raw material.
•Mass temperature of the digester agitation.
•Physical and chemical characteristics of the raw material.
•Level of pH.
•Presence of harmful elements.
PARAMETERS AFFECTING THE OPERATION OF BIODIGESTOR
PRODUCTIVITY OF BIOGAS SYSTEM WITHOUT AGITATION
Product Temperature (oC) Productivity (m3/kg)
Content of methane %
Retention Time (days)
Cattle dung (India)
11-31 0.23 – 0.50 -- --
Cattle manure (Germany)
15.5 – 17.3 0.20 – 0.29 -- --
Chicken Manure 34.6 0.31* 60 30
pig manure 32.6 0.7 60 15
* Based on volatile solids
Reference: Methane generation from human, animal, and agricultural waste. USA, Academy of Science, 1977
COMPARISON OF PRODUCTIVITY AND RETENTION TIME WITH CATTLE MANURE MIXTURES AGRICULTURAL WASTE
Waste mixed with manure
Production at 24 days
(m3/kg)
Production at 80 days (m3/kg)
Content of methane at 21
days %
None 0.063 0.21 60Sugarcane 0.4% 0.07 0.21 58Cellulose 1% 0.084 0.21 53Sugarcane 1% + Urea 1% 0.087 0.26 68
Leaves 20% no pulses 0.081 0.22 68
Reference: Methane generation from human, animal, and agricultural waste. USA, Academy of Science, 1977
BIOGAS PRODUCTION FROM COW MANURE: Temperature and retention time
Author’s own elaboration based on data from multiple sources
NITROGEN CONTENT AND C/N
Raw Material N (%) C/N
Animal urine 15-18 0.8Animal blood 10 14 3Cow dung 1.7 18Horse manure 2.3 25Pig manure 3.8 --Farm manure 2.15 14Amaranth 3.6 11
Reference: Methane generation from human, animal, and agricultural waste.
All materials are composed of fermentation mostly of carbon (C) and contain nitrogen (N). The C / N ratio influences the production of gas, this is optimal when C / N ranges between 20:1 and 30: 1.
For example, chicken manure (high N) mixed with rice chaff, is a high gas production.
If you suspect that digestion is being disturbed by toxic substances, add water or fermenting material, thus decreasing the concentration.
NITROGEN CONTENT AND C/N
PREPARATION OF THE MIXTURE
SOURCE: ENYA
AUXILIARY ELEMENTS FOR BIOGAS
SOURCE: ENYA
51
ANAEROBIC DIGESTION OF BIOMASS
NATURAL
SYNTHETIC
• DESCOMPOSITION OF TERRESTRIAL VEGETATION • DESCOMPOSITION OF ORGANIC MATTER ON WATER BODIES
ANAEROBICS DIGESTER• Agricultural waste• Urban waste
LANDFILLS• Agricultural waste• Urban waste
PRODUCTS
BIOGASCH4 50-75%CO2 25-50%
CompostWASTE
FUEL• Home• Transport• Electricity Generation
COMPOST• Agricultural use• High nutrient content
BIOMASS AS RENOVABLE SOURCE OF ENERGYDr. Roberto Best y Brown
ANAEROBIC DIGESTION
Anaerobic digestion and biogas anaerobic microbiological process is linked to the treatment of biodegradable waste and yielding as end product called "biogas", which is formed from organic matter biomass. It is therefore an environmental echnology energy component with an interesting
www.energianatural.com.ar/biogas02.html
BIODIGESTORS
• Hindu Type
Biodigestor Hindú Model
www.energianatural.com.ar/biogas02.html
BIODIGESTORS
• Chinese type
Biodigestor Chinese Model
www.energianatural.com.ar/biogas02.html
Biodigestors• MODERN TYPE - Has 2 Flexible membrane - Superior black membrane
http://www.ruralcostarica.com/biodigester.html
Horizontal Digestor, Plastic Cover
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