Biomass Densification : Biomass Densification N.KANAGARAJ
BSC[FORESTRY] Slide 2: Historically, biomass briquetting technology has been developed in two distinct directions.
Europe and the United States has pursued and perfected the reciprocating ram/piston press while Japan has independently invented and developed the screw press technology.
Although both technologies have their merits and demerits, it is universally accepted that the screw pressed briquettes are far superior to the ram pressed solid briquettes in terms of their storability and combustibility. Slide 3: Biomass densification refers to the process
whereby biomass in the form of small particles, like
straw, sawdust or chips, is concentrated by
machines into small pellets or briquettes.
Depending on the particular machine used, this
process increases the bulk density of the biomass by
about 10 to 12 times its original bulk density.
The moisture content of the compacted biomass
generally should be between 7% and 14%. If higher,
the biomass will not compact easily, if lower it will not
bind together as well. Slide 4: At present two main high pressure technologies:
1. Ram or piston press and
2. Screw extrusion machines, are used for briquetting.
2. Size reduction (to small particles: chop/hammer-mill/sieve) BIOMASS DENSIFICATION : BIOMASS DENSIFICATION Densification is the process of compacting low a bulk
density material into a product of high density
Densification has stimulate a great deal of interest
worldwide in recent years as a technique of beneficiation of residues for utilization as energy source.
Densified biomass is mostly in the form of briquettes
in developing counties and in the form of pellets in
developed countries. Screw Press and Piston Press Technologies : Screw Press and Piston Press Technologies High compaction technology or binderless technology consists of the piston press and the screw press.
Most of the units currently installed in India are the reciprocating type where the biomass is pressed in a die by a reciprocating ram at a very high pressure.
In a screw extruder press, the biomass is extruded continuously by a screw through a heated taper die.
In a piston press the wear of the contact parts e.g., the ram and die is less compared to the wear of the screw and die in a screw extruder press. Slide 7: The power consumption in the piston press is less than that of the screw press.
But in terms of briquette quality and production procedure screw press is definitely superior to the piston press technology.
The central hole incorporated into the briquettes produced by a screw extruder helps to achieve uniform and efficient combustion and, also, these briquettes can be carbonised. Piston presses : Piston presses The piston presses which are currently operating in India are also known as ram and die technology.
In this case the biomass is punched into a die by a reciprocating ram with a very high pressure thereby compressing the mass to obtain a briquette.
The briquette produced is 60 mm in external diameter. Slide 9: This machine has a 700 kg/hr capacity and the
power requirement is 25 kW.
The ram moves approximately 270 times per minute in this process.
The moisture content of the raw material should be less than 12% for the best results. Slide 10: Simple briquetting press Screw press technology : Screw press technology In the screw press technology, the biomass is extruded continuously by a screw through a taper die which is heated externally to reduce the friction. Advantages : Advantages The output is continuous and the briquette is uniform in size. .
The outer surface of the briquette is partially carbonized facilitating easy ignition and combustion.
This also protects the briquettes from ambient moisture. . A concentric hole in the briquette helps in combustion because of sufficient circulation of air. .
The machine runs very smoothly without any shock load. Slide 13: The machine is light compared to the piston press because of the absence of reciprocating parts and flywheel. .
The machine parts and the oil used in the machine are free from dust or raw material contamination. .
The power requirement of the machine is high compared to that of piston press. Densification In Developing Countries : Densification In Developing Countries Heated-die screw press technology is most common in
countries east of India, e.g. Korea, China, Taiwan,
Vietnam, Thailand, Malaysia, Philippines, Bangladesh,
etc. where heated-die screw-press briquetting
machines are almost exclusively.
The design of screw-press briquetting machines
appears to have evolved and been adapted to suit
local conditions in different countries. Slide 15: Heated-die Screw press (Japanese design) Slide 16: Thai Heated-die Screw press briquetting machines Slide 17: Bangladesh Vietnam Slide 18: The raw materials commonly used for briquetting are ricehusk, sawdust and agricultural residues.
About 1000 briquetting screw-press machines appear to be operating in Bangladesh. The technology appears to have been developed by the local entrepreneurs
without any support from the government or donor agencies.
Currently, there are about 600 biomass briquetting machines operating in China.
At present only six briquetting plants are in operation all of screw-press type. Slide 19: The piston press technology is the dominant technology in India, Brazil and Africa.
Piston presses are locally made in India and Brazil, the African machines appear to be mostly imported.
Compared to piston-press machines (440-1500kg/hr), heated-die screw press machines have smaller capacity (75-150 kg/hr) but produce stronger and denser briquettes.
In India, the number of machines installed so far: piston press machines ~ 150 and heated-die screwpress briquetting machines ~ 60. Slide 20: Mobile piston press briquetting machine (Sudan) Slide 21: Briquette made of coal, biomass and slaked lime has been introduced by a Japanese company in two Asian countries China and Indonesia. Slide 22: Small-scale carbonization-briquetting appears to be popular
in some places in Nepal. Pelletizing : Pelletizing Pelletizing is the major densification technology employed in developed countries. Capacity of these plants is much larger, being in the range 1-30 tons per hour Briquette : Briquette A briquette (or briquet) is a block of flammable matter which is used as fuel to start and maintain a fire.
Common types of briquettes are charcoal briquettes and biomass briquettes. Biomass briquettes : Biomass briquettes Biomass briquettes are made from agricultural waste and are a replacement for fossil fuels such as oil or coal, and can be used to heat boilers in manufacturing plants, and also have applications in developing countries.
Biomass briquettes are a renewable source of energy and avoid adding fossil carbon to the atmosphere.
The use of biomass briquettes is predominant in the southern parts of India, where coal and furnace oil are being replaced by biomass briquettes Wood briquettes : Wood briquettes Wood briquettes are made of dry, untreated wood remainders, like sawdust.
The chips are compressed, without add-ons like binders, to become hard briquettes.
Because of this high compression, the wood burns similarly to brown coal.
The difference is that the wood briquette has less sulphur and ash content compared to fossil fuels, and doesn't contribute to build-up of CO2 in the atmosphere, as burning wood releases CO2 recently absorbed by the tree. Wood briquettes : Wood briquettes Constituents Of Charcoal Briquettes : Constituents Of Charcoal Briquettes Wood charcoal (fuel),
mineral char (fuel),
mineral carbon (fuel),
Limestone (ash colorant),
Borax (release agent),
Sodium nitrate (accelerant),
Sawdust. Charcoal Briquettes : Charcoal Briquettes