BIOMASS Animal or vegetal Moist Obtained with moisture content above 60% Dry Obtained with moisture content below 60% Physical PrecessesBiological Processes Thermochemical Processes Combustion Pyrolisis Gasification Liquefaction Fermentation (alcohol) Bacterian digestion Drying-Compac Chopping Mechanical 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.
Thermochemical processes (pyrolysis, gasification and combustion) consist on the organic components decomposition of biomass at high temperatures. Main thermo-chemical processes are: Combustion Pyrolysis Gasification THERMO-CHEMICAL PROCESSES
LIGNOCELLULOSE IN AIR SCHEME COMBUSTION - DRYING - ROASTING - PYROLYSIS COMBUSTION AIR ASH FLAME CHAR WOOD VOLATILE CHARCOAL
Pyrolysis Is 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
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- ói l. 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 Coal Gas 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 + O 2 CO 2 + H 2 O + 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
Operating Temperature in Chamber Operating 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.
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.
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 Combusti o n 65-95 20-35 Pyr o lysis (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
Control and Emissions Combustion plants produce effluent gases, solids and liquids. Particles are one of the most important emissions on biomass combustion. GAS TREATMENT SYSTEMS CYCLONIC SYSTEMS CYCLONIC SYSTEMS BAG FILTERS BAG FILTERS WET SCRUBBER WET SCRUBBER ELECTROSTATIC FILTERS 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 ProductTemperature (oC)Productivity (m3/kg) Content of methane % Retention Time (days) Cattle dung (India) 11-310.23 – 0.50-- Cattle manure (Germany) 15.5 – 17.30.20 – 0.29-- Chicken Manure34.60.31*6030 pig manure32.60.76015 * 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 0.0630.2160 Sugarcane 0.4% 0.070.2158 Cellulose 1% 0.0840.2153 Sugarcane 1% + Urea 1% 0.0870.2668 Leaves 20% no pulses 0.0810.2268 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 MaterialN (%)C/N Animal urine 15-180.8 Animal blood 10 143 Cow dung 1.718 Horse manure 2.325 Pig manure 3.8-- Farm manure 2.1514 Amaranth 3.611 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
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 BIOGAS CH4 50-75% CO2 25-50% Compost WASTE FUEL Home Transport Electricity Generation COMPOST Agricultural use High nutrient content BIOMASS AS RENOVABLE SOURCE OF ENERGY Dr. 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