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 60

Sugarcane 0.4% 0.07 0.21 58

Cellulose 1% 0.084 0.21 53

Sugarcane 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

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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