FORM 2
THE PATENT ACT 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)

1. TITLE OF THE INVENTION : A municipal waste disposal system and the
production of a high calorific value Green !
Coal as a fuel'

2. APPLICANT
(a) NAME:
(b) NATIONALITY
(c) ADDRESS:

Future Fuels (International) Limited
United Kingdom
Future Fuels (International) Limited 2 & 3 Church Street, Beckley, Oxford, OX3 9UT,United Kingdom

3. PREAMBLE TO THE DESCRD7TION
COMPLETE SPECD7ICATION The following specification particularly
describes the invention and the manner in which it is to be performed

TITLE
A municipal waste disposal system and the production of a high-calorific value
'Green Coal' as a fuel.
FIELD OF THE INVENTION
The invention relates a process for treating mixed municipal waste and specifically to
manufacturing high calorific fuel through aerobic digestion of the same.
1.0 STATE OF THE ART IN THE FIELD
1.1 Composting is simply the method of breaking down organic materials in a large container or heap, and the decomposition occurs because of the action of naturally occurring microorganisms such as bacteria and fungi. Composting can convert organic waste into rich, dark colored compost, or humus, in a matter of a few weeks or months. Compost production only treats the separated organic fraction or waste and requires up to 12-13 weeks for completion and is accompanied by CO2 production, thus adding to the global warming.
1.2 OBJECT OF THE INVENTION
The primary object of the present invention is to devise a process for treating municipal waste and a method for manufacturing high-calorific value fuel from the said municipal waste.
1.3 STATEMENT OF THE INVENTION
The development of a process to treat delivered mixed municipal waste in India offers a long-term guarantee to local and government authorities for the disposal of wastes. The process combines drying of the mixed incoming municipal wastes, screening, blending and using the biologically generated heat in drying to produce a stable low-grade fuel with constant thermal characteristics.

The Table - 1 below of the waste composition is an average of all samples taken in Ulhasnagar, Kalyan and Thane (over 100) during the past 6 years. The variation relating to seasonal and area of collection is also indicated. It should also be noted that up to 50% of the plastic content and similar proportion of metal and glass is scavenged by gangs operating on landfill sites and this also has to be taken into the account.
Table-1

Type of waste % range as received Weighted average %
Paper, Cardboard 25-45 36.0
Dense Plastic 3-8 5.0
Light Plastic 2-6 3.0
Glass 1-3 2.0
Metal (ferrous) 1-4 1.5
Metal (aluminum) 0.5-1.0 0.6
Organic 5-12 7.0
Miscellaneous 35-50 45.0
The present invention offers the following distinct advantages over the prior art, namely: i) The process and apparatus can treat mixed municipal waste having a very variable
moisture level and physical composition, ii) It yields a relatively homogeneous product as a fuel for boiler, iii) It generates no obnoxious gases and rids the surrounding area of foul smells, iv) Biologically generated heat is effectively utilized for drying, obviating thereby
externally heating the municipal waste, v) The net calorific value of the treated waste remains above 12500 KJ/kg and has a
competitive commercial value as a replacement, recycled non fossil fuel for
boiler with its homogeneous character, controlled ash content, calorific value,
moisture level and density.

vi) The process reduces the mixed municipal waste by 50% in volume, yielding
dry and dense mass. The present invention thus provides heat generated for breaking down the mixed municipal waste and for drying it. The process is controlled by taking different feeds of waste having different average moisture levels being treated and blending them before the recycling aerobic drying process. 1.4 DESCRIPTION OF THE INVENTION
1.4.1 Mixed municipal waste having a variable moisture level and composition is received at Point 1 in drawing # 2 and the non-combustible material is separated before treatment.
1.4.2 The waste is checked to have moisture content of 45% by weight, but not exceeding 60% by weight.
1.4.3 The waste is fed through Conveyors 2 and 3 to Primary Crushers 4 and 5 (drawing # 2). The crushed waste is transported through conveyors 6 and 7 to Final Crushers 8 and 9.
1.4.4 The finely crushed waste is fed though conveyors 10 and 11 to bio-reactors-
dryers 12-13 and 14-15 respectively, where rotary drying of the product to average
moisture content of less than 15% by weight is carried out by combining the aerobic
drying with the conventional rotary drying of the mass. It is capable of handling
the mixed municipal waste having an organic waste component that biologically decomposes. The biological deowmjositionujs cjuried^ ojutjunder aerobic conditions, /using bacteria inyie thermophilic phase in the temperature range of above 45°C to the upper limit of 63-70°C. In this phase, very rapid decomposition occurs with the rapid production of heat. The reaction in the thermophilic phase results in the natural

regeneration of heat that breaks down the mixed municipal waste. The reaction almost always generates sufficient heat to maintain temperature at the required level without any addition of supplementary heat. The oxygen level in the gas in contact with the mixed solid waste being treated is maintained above 5% by volume and the moisture content of the gas in contact with the mixed solid waste is maintained at a level below its dew point. This ensures that water is continuously removed from the mixed solid waste being treated into the gas space by evaporation. Instrumentation and controls are provided to monitor the oxygen and the moisture levels of the gas in the Bio-Reactors-Dryers. The flow of air and gas through the Bio-Reactor-Dryer removes heat generated by biological degradation within the concentrated mass of mixed solid waste, thereby achieving heat balance and the temperature is maintained at a desirable level.
1.4.5 Conveyors 16,17 (diagram # 2) feed the discharge mass of the Bio-Reactor Dryers to Homogenizers 18-19 respectively, which facilitate digestion in a rotating action of speed of 1 revolution per 10-15 minutes that facilitates uniform exposure of the mass to gas and dissipation of heat to the gas. Drum is rotated during feeding and discharge at the higher speed of 1 revolution per minute. The Homogenizer drum is a circular section cylinder and has its axis inclined to the horizontal at an angle in the range of 5-8 degrees, to provide gravitational flow through the drum. For a processing rate of 250 tons per day, two drums of diameter in the range of 3.5-4 m should be used. The length should be in the range from 4-6 times the diameter. Up to 1000 t/d of mixed municipal waste will require 4 separate lines. For tonnage in the excess of 10 tonnes/day, the rotary homogenizer will go up to 5 m in diameter. The drum is made of mild steel and has an advantage that it is mechanically simple. The

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agitation caused by the rotation leads to attrition of the solid waste, further contributing to its breakdown. The drum is filled initially to 75-90% full by volume. This leads to increased attrition, rapid heat generation and also to efficient use of the plant. Average residence time of mixed municipal waste in the treatment vessel is suitably in the range of 36-48 hours i.e. to process the daily input to the plant. Loading and unloading occur substantially simultaneously, with fresh mixed solid waste being loaded at the loading end and the mixed solid treated waste being removed at the unloading end. The new daily input is fed as the rotary homogenizer discharges the previous days waste. The waste material is discharged from the treatment vessel at a stage at which the treated waste material is sufficiently digested and sufficiently dry. This typically occurs after a period of about 48 hours. By restricting residence time to 48 hrs or less, additional loss of carbon is reduced. 1.4.6 Conveyors 20-21-22-23 transport the homogenized mass to Dryers 24-25 and sent through conveyors 26-27 to Bailing Press 28-29. 1.5 OPERATION OF THE INVENTION
In the first place, the delivered mixed municipal waste is preferably treated in a first process before aerobic digestion to remove more preferably 50 mm material. This process may comprise a first step in which very large objects are removed, for example by hand or by screening and a second step in which the remaining material is treated to reduce its particle size, for example by shredding. The shredding operation is particularly significant, as it mixes the material thoroughly, spreading the active bacteria culture throughout the material and generating the necessary thermophilic reaction very rapidly. If the municipal waste after mixing is low in organic content or moisture level, water may be preferably added in controlled quantities. This process

water is preferably waste water from water treatment, most preferably dewatered sewage sludge. This material has high nitrogen content and acts as a catalyst for the biological reaction. According to the first aspect of the present invention, control of the moisture level is obtained by blending mixed municipal waste with other waste of a lower average moisture level. It is found that the mixed domestic waste typically has
a moisture level in excess of 40% by weight. Agriculture waste may have a moisture
i level in excess of 75% by weight and sometimes 80% by weight, particularly in
tropical and subtropical countries for crops such as banana and pineapples. Finally
commercial waste from offices and factories is typically much drier, having a
moisture level in the range of 10-30% by weight.
The moisture level of waste fed to the digester may be manipulated by altering the
mixing ratios of different types of waste. It is required that the organic fraction of the
waste fed to the digester has a moisture level in the range of 40-75% by weight,
preferably 55-65% by weight in order to promote the faster thermophilic reaction.
However part of the waste fed to the digester may comprise a relatively dry !
commercial waste. The heat generated by the digestion of the moist waste is sufficient
to treat the whole of the waste fed to the treatment vessel. However, during the
agitation process, the commercial and domestic wastes are slowly mixed together
reducing the overall moisture content of the mixture, so that at the end of the initial
blending processing, the moisture level does not exceed 50% by weight.
Solid waste with higher moisture level may be blended with solid waste with lower
moisture level in blending apparatus in a controlled manner. The relative quantities of
different types of waste are controlled so that the desired average moisture level over
the combined masses of mixed municipal wastes is obtained as explained above.

The blending step also allows absorbent material such as paper and paper based material (which is particularly common in commercial waste) to be blended with moist waste (such as agricultural waste). The absorbent material absorbs liquid rich in bacteria, providing a substrate for the bacteria to grow on and allowing the bacteria to be spread throughout the waste being processed. This promotes reaction and mixing, leading to an improved reaction. Further, the wetting of the paper helps it to be broken down.
In processing mixed municipal waste it is particularly important to produce a product that is substantially homogeneous, and is less than 50 mm in particle size. The blending step helps to improve the homogeneity of the product. The pH of the mixed municipal waste is suitably in the range around 6.8 Nitrogen level has an impact on the microbial activity, and adjustment of pH and nitrogen content can be advantageous. The density of the mixed organic waste fed to the treatment vessel for digestion process is not less than 450 gm per liter. Again, the blending step is particularly useful here. Mixed municipal waste can have a relatively low density but at input of 45% blended will be between 400 and 600 gm per liter. It is the initial treatment to remove objects that are not combustible, such as stone, concrete, metal, old tyres, etc. Objects having a size in excess of 100 mm or more may also be removed. The process can be carried out on a stationery surface, such as a picking floor. Alternatively or additionally, the mixed municipal waste may be loaded onto a moving surface such as a conveyor and passed through a picking station in which mechanical or manual picking of the material takes place.
2. Shredding Shredding is an essential preferred step. It is carried out to reduce the average particle

size. It can also be used to increase blending of waste from different sources. It also makes the treatment process more effective. It is found that, during the shredding process, biological activity may commence and rapidly raises the temperature passing very quickly through the mainly anaerobic mesophilic phase the aerobic thermophilic phase.
3. Screening
The mixed organic waste may be mechanically screened to select particles with size in a given range. The given range may be from 10 mm to 50 mm. Material less than 10 mm in size comprises dust, dirt and stones and is rejected. The mixed organic waste may be treated to at least two screening processes in succession, each removing progressively smaller fractions of particles. Material removed in the screening process as being too large may be shredded to reduce its average size. Material which is classified by the screen as being of acceptable size and where applicable, the shredded material can then be fed to the treatment vessel.
4. Subsequent Treatment
The treated material may be subjected to a number of steps after the treatment process. These steps may include any of the following:
a) Grading
The material may be screened to remove particles in excess of a given size. For example, particles in excess of 50 mm may be rejected. They may be subsequently shredded to reduce their size, returned to the aerobic digester or simply rejected.
b) Metal separation
Relatively small metal particles such as iron or aluminum may have passed through the system. They can be removed, for example by a magnetic or electromagnetic

remover in a subsequent step. Metal particles removed from the system may be then passed to a suitable recycling process.
c) Drying
After hand separation and shredding to a particle size less than 50 mm, the mixed municipal waste is contained in a large intermediate storage area that is constantly aerated and blended. The intermediate storage area will be designed to receive two days input shredded screened product and this will raise the average temperature to above 55°C before being fed to the rotary homogenizer. Since the process is now thermiphillic, no unpleasant odours are produced. Rotary drier
After the rotary homogenizer, the product is suitable for further drying using conventional rotary dryer. It is finally dried to 15% moisture, resulting in a stable fuel that has low density i.e. less than 200 k/m3 and is ideal to be used in a fluidized bed boiler for the commercial sale of process heat and/or electricity.
d) Pelletiser
If required, the final product can be pelletised to allow transportation costs to be
reduced if suitable available boilers can be identified.
The method and apparatus of the invention can be used to produce a product that is
suitable for subsequent storage, transportation or sale.
It has been found that the method of the invention can provide a fuel, referred to as
Green Coal, that has a calorific value in the order of 14,500 kJ/kg which is about half
that of the industrial coal. The material has an ash content of less than 20% by weight
and has the additional advantage that it will contain relatively low levels of sulphur
and chlorine, so reducing pollution due to acid rain from the gases of combustion.

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By blending different sources of waste material, fuel produced at different times or
i with waste from different locations can be relatively homogeneous in terms of:
1. Calorific value - suitably in the range 13,000 to 16,500 kJ/kg
2. Density - suitably in the range 150-300 g/1
3. Moisture level - Around 15% by weight
This fuel can be used either on its own or as a supplementary fuel. The apparatus and method of the invention may alternatively form a part of a plant or system. The apparatus and method of the invention can be used to supply fuel in a plant or system. Example
A process according to figures 1-3 was operated with a feed comprising 250 t/day of > mixed municipal waste. The average moisture level of waste input to the rotary aerobic digester was 45% by weight, with some batches having higher moisture level and some batches having lower moisture level. The initial hand separation is followed by mechanical shredding to reduce particle size below 50 mm and further assist in blending the received mixed municipal waste. Additional available mixed waste can be blended in at this stage e.g. suitable commercial waste or dewatered sewage sludge that can adjust the moisture content of resultant mix to the required 40-50% H2O, preferably 45%.
An intermediate area suitable to take two days supply of screened and shredded mixed municipal waste is provided. This intermediate storage area is contained by 6 m concrete walls over an area of 150 m2. The bulk density at this stage will vary between 350-450 kg/m3. This area will be continuously turned using mobile shovel and air will be injected to ensure the correct aerobic conditions apply. The temperature will raise throughout the 48 hours to exceed 55°C ready for the rotary
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homogenizer drier. Moisture loss of between 4% and 8% can be realized in this
intermediate storage area.
Treated waste collected from rotary aerobic homogenizer, after unloading and fan
drying had a moisture level of about 30% by weight. Additional drying with
conventional rotary dryer reduces the moisture to 15%.
From an input annually of 75,000 tones of combined waste materials, 40,000 tones of
green coal can be produced, having a calorific value equivalent to 15,000 tones of fuel
oil.
The final product was found to have constant thermal characteristics and to be
suitable for use as a supplementary fuel, going by the description of green coal. It had
a minimum calorific value 14,000 kJ/kg. It has an ash content of less than 20% by
weight and very small quantities of sulphur and chlorine.
DETAILED DESCMPTION OF THE INVENTION WITH REFERENCE TO
THE DRAWINGS
The process flow for 240 t/d of mixed municipal waste can be described as follows.
Waste is delivered by municipalities to the weigh-board and tipped at the covered
area reception. This area is spacious (40 m x 60 m) to allow adequate 'hand sorting'
to remove non-combustible material before passing to the shredder. Included in this
important stage of separation is the ferrous and aluminum separation (magnetic and
reversed eddy current technology). These systems are now well established in modern
waste processing front-end technology.
The Shredder is a rotary hammer design and will process an average of 15 t/hr of the
delivered screened waste. The particle size will be reduced to less than 50 mm (95%)
and delivered to aerobic storage. Again this capacity is covered with provision for

sunlight to reach the material It is very important to ensure the build-up of processing temperature to ensure it is above 55°C before passing to the homogenizer drier.
The homogenizer drier is 4 ni diameter by 20 m and the process requires two to meet
i a 24 hr input flow balance. The drums are initially rotated at speeds between 1 rev/10
min or 1 rev/15 min and when 75% full are slowed down to 1 rev/10 min or 1 rev /15
min. After the shredding and initial aerobic drying and the blending and distribution
of \he organic moisture, Ihe tfrateriai is Yfra^amed at f&^WC foi 1A \ai>. Dry amfcrerft
air is fed into the drum and exhausted through a biofilter. The conditions in the rotary
homogenizer are such that saturated air is exhausted continually and as a result the
tonnage is reduced to loss of water content. Again importantly the constant rotary
agitation provides for further blending of the material to ensure the final Green coal is
homogeneous - thus ensuring a constant fuel with established and uniform thermal i
characteristics.
After 24 hours, the blended material is passed through a conventional rotary dryer
after storage for up to 24 hrs in the intermediate storage area. This reduces the
moisture to approximately 30%. The rotary drier is maintained at 90°C for up to 10
hrs and this reduces moisture content to an average of 15%.
There is a provision for an air classifier that can be added which will remove dense
(non-combustible material) that enhances the net calorific value should it be required.
Finally for power/process heat generation, the Green coal is passed to the fluidized
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boiler. This type of boiler is well established and is ideal to burn either in combination with other fuel or can be designed to burn Green coal as a prime fuel. These boilers can be designed with complete environmental controls and are much less expensive to build and operate than incineration plant used in mass incineration.

We claim:
1. A process for waste disposal of mixed municipal waste (90) comprising: (i) initial screening in rotary screen (50) for non-combustible material (91) from
delivered municipal waste (90); (ii) controlling variable moisture content of the said waste readied (92) for treatment at 45% level by weight but not exceeding 60% by weight by inter¬mixing of the municipal waste;
(iii) feeding the said municipal waste (92) through conveyors (2,3) to primary crushers (4,5) for primary stage crushing (93);
(iv) feeding the said primarily crushed waste (93) to final crushers (8,9) through conveyors (6,7) for final stage crushing (94), whereby temperature of the said crushed waste (94) reaches 60 degree C and initiating decomposition of the said final stage-crushed municipal waste (94) by thermophyllic bacteria;
(v) feeding the said finally crushed waste (94) through conveyors (10, 11) to bio- reactors-dryers (12,13) and (14,15) respectively, where the said waste (94) is continuously agitated in rotary motion of the said bio-reactors-dryers (12, 13) and (14,15);
(vi) drying in aerobic conditions the said finally crushed waste (94) to final product -green coal - having moisture content of less than 15% by weight (95) in presence of counter-current hot air having temperature of 70-90 degree Centigrade;
(vii) compressing the said final product (5) - green coal - into cubes.

2. A process for waste disposal of mixed municipal waste as claimed in claim 1,
wherein speed of rotation of the said bio-reactor- dryers (12, 13) and (14,15) is
maintained at one rotation every 10 to 15 minutes along a horizontal axis of the
said bio-reactor-dryers (12,13) and (14,15).
3. A process for waste disposal of mixed municipal waste as claimed in claim 1,
wherein the said speed of rotation for the said bio-reactor-dryers (12, 13) and
(14,15) is increased to one revolution per minute for loading and unloading
operations on the said bio-reactor-dryers.
4. A process for waste disposal of mixed municipal waste as claimed in claim 1,
wherein the said the said bio-reactor-dryers (12, 13) and (14, 15) have
their axes inclined with the horizontal by an angle of 5 - 8 degrees with the loading at the elevated end and unloading at the lower end of the said bio-reactor-dryers (12, 13) and (14, 15).
5. A process for waste disposal of mixed municipal waste as claimed in claims 1 and
2, wherein the said bio-reactor-dryers are cylindrical drum-shaped of suitable
length such that residence time of the said final stage-crushed municipal waste in
the said bio-reactor-dryers (12, 13), (14, 15) is between 36 to 48 hours.

6. A process for waste disposal of mixed municipal waste as substantially described herein before and illustrated in drawings # 1 and 2.
Robin Robins, Director Future Fuels Limited, Applicant