MSW is a poor-quality fuel and its pre-processing is necessary
to prepare fuel pellets to improve its consistency, storage and handling
characteristics, combustion behaviour and calorific value. Technological
improvements are taking place in the realms of advanced source separation,
resource recovery and production/utilisation of recovered fuel in both existing
and new plants for this purpose. There has been an increase in global interest
in the preparation of RDF containing a blend of pre-processed MSW with coal
suitable for combustion in pulverised coal and fluidised bed boilers.
Pelletization of municipal solid waste involves the processes of
segregating, crushing, mixing high and low heat value organic waste material
and solidifying it to produce fuel pellets or briquettes, also referred to as
Refuse Derived Fuel (RDF). The process is essentially a method that condenses
the waste or changes its physical form and enriches its organic content through
removal of inorganic materials and moisture. The calorific value of RDF pellets
can be around 4000 kcal/ kg depending upon the percentage of organic matter in the
waste, additives and binder materials used in the process.
The calorific value of raw MSW is around 1000 kcal/kg while that
of fuel pellets is 4000 kcal/kg. On an average, about 15–20 tons of fuel
pellets can be produced after treatment of 100 tons of raw garbage. Since
pelletization enriches the organic content of the waste through removal of
inorganic materials and moisture, it can be very effective method for preparing
an enriched fuel feed for other thermochemical processes like pyrolysis/
gasification, apart from incineration. Pellets can be used for heating plant
boilers and for the generation of electricity. They can also act as a good
substitute for coal and wood for domestic and industrial purposes. The
important applications of RDF are found in the following spheres:
·
Cement kilns
·
RDF power plants
·
Coal-fired power
plants
·
Industrial steam/heat
boilers
·
Pellet stoves
The conversion of solid waste into briquettes
provides an alternative means for environmentally safe disposal of garbage
which is currently disposed off in non-sanitary landfills. In addition, the
pelletization technology provides yet another source of renewable energy,
similar to that of biomass, wind, solar and geothermal energy. The emission
characteristics of RDF are superior compared to that of coal with fewer
emissions of pollutants like NOx, SOx, CO and CO2.
RDF production line consists of several unit operations in
series in order to separate unwanted components and condition the combustible
matter to obtain the required characteristics. The main unit operations are
screening, shredding, size reduction, classification, separation either metal,
glass or wet organic materials, drying and densification. These unit operations
can be arranged in different sequences depending on raw MSW composition and the
required RDF quality.
Various qualities of fuel pellets can be produced, depending on
the needs of the user or market. A high quality of RDF would possess a higher
value for the heating value, and lower values for moisture and ash contents.
The quality of RDF is sufficient to warrant its consideration as a preferred
type of fuel when solid waste is being considered for co-firing with coal or
for firing alone in a boiler designed originally for firing coal.
About Salman Zafar
Salman Zafar
is a renowned expert in waste management, biomass energy, waste-to-energy and
sustainable development. He is proactively engaged in creating mass awareness
on renewable energy, waste management and environment. Salman is the CEO of
BioEnergy Consult, apart from being the Founder of Cleantech Solutions and
EcoMENA. Salman has successfully accomplished a wide range of projects in the
areas of biogas technology, biomass energy, waste-to-energy and solid waste
management. He has participated in numerous national and international
conferences and has authored many articles in reputed journals and magazines.
Salman can be reached at salman@bioenergyconsult.com or
salman@cleantechloops.com.
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