Claims:WE CLAIM:

1. A method for converting wet municipal solid waste to dried fuel pellets, the method comprising the steps of:
• receiving a calculated quantity of wet municipal solid waste in segregated form;
• removing non biodegradable matter from the wet municipal solid waste;
• shredding the wet municipal solid waste into fine particles using a shredder;
• blending the shredded wet municipal solid waste with dried biomass using a blender;
• breeze drying the blended waste using a vibrating tray type dryer; and
• compacting the breeze dried waste to any one of pellets and briquettes, the pellets/briquettes capable of being used in biomass stoves as cooking fuel for cooking food as well as into biogas digesters to produce biogas.

2. The method (100) as claimed in claim 1, wherein the wet municipal solid waste is shredded to a reduced particle size of about less than 10 mm.

3. The method (100) as claimed in claim 1, wherein the dried biomass is selected from any of rice straw and sawdust.

4. The method (100) as claimed in claim 1, wherein the dried biomass is mixed with the shredded wet municipal solid waste at a concentration of about 20% by weight.

5. The method (100) as claimed in claim 1, wherein the blending is carried out at a speed of 8 revolutions per minute using a stirred type blender to reduce initial moisture content of about 75% to about 45%.
6. The method (100) as claimed in claim 1, wherein breeze drying the blended waste comprises the steps of:
• spreading a thin film of blended waste on a plurality of trays mounted on a frame of the vibrating tray type dryer;
• putting the vibrating tray type dryer into a drying chamber;
• lifting the frame in the air using a spring arrangement of the vibrating tray type dryer;
• vibrating the frame using a vibrator motor of the vibrating tray type dryer;
• forcing ambient air, using a fan, continuously over the thin film of blended waste spread on the plurality of trays to breeze dry the blended waste in the drying chamber; and
• collecting the dried waste for being compacted.

7. The method (100) as claimed in claim 1, wherein breeze drying of the blended waste is carried out without using an external heat source and reduces the moisture content of the blended waste from about 45% to about 20% only.

8. The method (100) as claimed in claim 1 comprises measuring the weight and moisture content of the wet municipal solid waste before and after breeze drying.

9. The method (100) as claimed in claim 1, wherein the wet municipal solid waste is selected from a group consisting of organic waste including kitchen waste, hotel waste, food waste, vegetable market waste, fruit market waste and mixtures thereof. , Description:METHOD FOR CONVERTING WET MUNICIPAL SOLID WASTE TO DRIED FUEL PELLETS

FIELD OF THE INVENTION

The present invention relates to processing of organic waste and more particularly, to a method for converting wet municipal solid waste to dried fuel pellets.

BACKGROUND OF THE INVENTION

Normally, the conversion of wet organic waste into fuel pellets requires moisture content of the waste to be reduced from 80-85% to 20-25%. Conventional drying systems have following drawbacks:
• Mechanical dryer consumes large energy in terms of electricity and heat that increases the cost of the process.
• Some systems take long time for moisture reduction rendering its use non-feasible.
• Other available systems results in production of effluent along with the dried biomass. The effluent needs a separate treatment/disposal scheme that again increases the time and cost.
• In conventional drying, heating or hot air is normally used to dry the biomass. Though it is quite faster method, unfortunately it is very costly method.

Hence, there exists a need to provide a method for converting wet municipal solid waste to dried fuel pellets that overcome the above mentioned drawbacks of the prior art.

OBJECT OF THE INVENTION

An object of the present invention is to achieve complete conversion of wet organic waste into dried pellets at lower cost, in reduced time and without producing effluent.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides a method for converting wet municipal solid waste to dried fuel pellets. The wet municipal solid waste is selected from a group consisting of organic waste including kitchen waste, hotel waste, food waste, vegetable market waste, fruit market waste and mixtures thereof.

The method comprises receiving a calculated quantity of wet municipal solid waste in segregated form and removing non biodegradable matter therefrom. The method further comprises shredding the wet municipal solid waste into fine particles using a shredder to a reduced particle size of about less than 10 mm.

The method further comprises blending the shredded wet municipal solid waste with dried biomass such as rice straw and sawdust using a blender for example a stirred type blender. Typically, the dried biomass is mixed with the shredded wet municipal solid waste at a concentration of about 20% by weight and blending is carried out at a speed of 8 revolutions per minute to reduce initial moisture content of about 75% to about 45%.

The method further comprises breeze drying the blended waste using a vibrating tray type dryer without using an external heat source and reduces the moisture content of the blended waste from about 45% to about 20% only. The breeze drying of the blended waste includes the steps of spreading a thin film of blended waste on a plurality of trays mounted on a frame of the vibrating tray type dryer. The breeze drying further includes putting the vibrating tray type dryer into a drying chamber, lifting the frame in the air using a spring arrangement of the vibrating tray type dryer and vibrating the frame using a vibrator motor of the vibrating tray type dryer. The breeze drying step further includes forcing ambient air, using a fan, continuously over the thin film of blended waste spread on the plurality of trays to breeze dry the blended waste in the drying chamber and collecting the dried waste for being compacted. The method comprises measuring the weight and moisture content of the wet municipal solid waste before and after breeze drying.

The method further comprises compacting the breeze dried waste to any one of pellets and briquettes capable of being used in biomass stoves as cooking fuel for cooking food as well as into biogas digesters to produce biogas.

BRIEF DESCRIPTION OF DRAWING

Figure 1 is a flowchart illustrating a method for converting wet municipal solid waste to dried fuel pellets, in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The foregoing objects of the present invention are accomplished and the problems and shortcomings associated with the prior art, techniques and approaches are overcome by the present invention as described below in the preferred embodiment.

The present invention provides a method for converting wet municipal solid waste to dried fuel pellets. The method achieves complete conversion of wet organic waste into dried pellets at lower cost, in reduced time and without producing effluent.

The present invention is illustrated with reference to the accompanying drawing, throughout which reference numbers indicate corresponding parts in the various figure. These reference numbers are shown in bracket in the following description.

Referring now to figure 1, a method (100) for converting wet municipal solid waste to dried fuel pellets, in accordance with the present invention is described. The method (100) is carried out using a system (not shown) comprising of a shredder, a blender, a dryer and a compactor. The wet municipal solid waste (herein after ‘the MSW)’ is selected from a group consisting of organic waste including but not limited to kitchen waste, hotel waste, food waste, vegetable market waste, fruit market waste and mixtures thereof.

In an embodiment, the method processes less than 500 kg of MSW per day. In a preferred embodiment, the method processes about 25 kg to 50 kg of MSW per day with a possibility of scaling up to 100 kg/day and 250 kg/day. The method is also capable of disposing up to 1.0 ton of MSW per day thus providing the much needed wet waste MSW disposal solution at decentralized locations.

The method begins at step (10). At step (20), the method (100) involves receiving a calculated quantity of wet MSW in segregated form. In an embodiment, the quantity of wet MSW is calculated using a weighing balance (Range 0-200 kg LC 200 gm). At step (30), the method (100) involves removing non biodegradable matter such as metal, plastic and the like from the wet MSW.

At step (40), the method (100) involves shredding the wet MSW into fine particles using the coarse and fine shredder without water. In an embodiment, the wet MSW is shredded to a reduced particle size of about less than 10 mm.

At step (50), the method (100) involves blending the shredded wet MSW with dried biomass using the blender. In an embodiment, the dried biomass for example rice straw/ sawdust is mixed with the shredded wet MSW at a concentration of 20% by weight and is blended at a speed of 8 revolutions per minute (RPM) using a stirred type blender in such a way that the initial moisture content of about 75% is reduced to about 45%. Blending is carried out to make the waste ready for drying. A sample from the blended waste is taken for moisture content determination.

At step (60), the method (100) involves drying the blended waste using the dryer. Specifically, the blended waste is breeze dried using a vibrating tray type dryer. The vibrating tray type dryer includes a frame, a spring arrangement, a vibrator motor and a plurality of trays. In an embodiment, the vibrating tray type dryer includes a total of 12 thin trays. The plurality of trays is mounted on the frame to be coated with a thin film of blended waste. The frame is lifted into air using a spring arrangement so as to achieve a dancing position. The frame is kept in vibrating motion using the vibrator motor attached thereto. Specifically, the vibrator motor power is 0.5 Hp that works 2 min in one hour. Thus, total energy consumed is less than one unit per day. The vibratory tray type dryer uses ambient air having specific heat at particular temperature and pressure. The air is forced continuously, using a fan over the thin film of organic wet waste material to supply specific heat thereto. The electric fan is kept operational, for round the day, that creates air draft, which helps in breeze drying the wet biomass. The power of fan is 50 W, running for 24 hours. Thus, energy consumed by fan is 1.2. This heat assists in vaporization and reduction of the moisture content of the biomass without the need of external heat supply/ hot air or heat source. In an embodiment, breeze drying reduces the moisture content from about 45% to about 20% only and thus achieves about 20 kg water removal per unit of air supply.

Specifically, the breeze drying step includes spreading a thin film of blended waste on each tray of the plurality of trays evenly, putting the plurality of trays into a drying chamber, lifting the frame in the air using the spring arrangement, vibrating the frame using the vibrator motor, setting a time for the vibrator motor on a control panel as 1 min ON, 59 min OFF, starting the fan to continuously force the ambient air over the thin film of blended waste spread on the plurality of trays to breeze dry the blended waste in the drying chamber. After 23 hours of drying, the trays are removed to collect dried waste therefrom. A sample from the dried waste is taken for moisture content determination. Thus, the method involves measuring the weight and moisture content of the wet municipal solid waste before and after drying. In an embodiment, the moisture content is measured using an infra red moisture balance.

At step (70), the method (100) involves compacting the breeze dried waste to pellets or briquettes. The pellets or briquettes are capable of being used as cooking fuel in biomass stoves for cooking food or are put into biogas digesters to produce biogas. The method (100) ends at step (80).

EXAMPLE:

The method of the present invention will be described in more details below by means of examples. The following example is provided in order to demonstrate and further illustrate certain preferred embodiments and aspects of the present invention and is not to be construed as limiting the scope thereof.

The quantity of waste, about 40 kg, to be processed was calculated. The waste after removal of non-biodegradable matter was shredded. The shredded waste was blended with dried biomass, about 10 kg. Initial weight (in Kgs) and initial moisture content (in %) were measured. The blended waste was spread on 12 trays of the vibrating tray dryer maintaining 5 kg loading capacity per tray. After 23 hours of breeze drying using air forced continuously over the blended waste spread on 12 trays, the breeze dried waste was collected and final weight (in Kgs) and final moisture content (in %) were measured. Thereafter, the breeze dried waste was compacted to form dried pellets/briquettes.

Observations Datasheet:

Expt. No. Weight of RM (Kg) Weight of dried biomass (Kg) Initial weight of blended waste (Kg) Initial moisture content of blended waste (%) Final weight of dried waste (Kg) Final moisture content of dried waste (%) Moisture removed (Kg)
1 50 10 60 44 43.13 36 16.87
2 23 4 27 43 13.79 37 13.21
3 50 5 55 47 33.13 36 21.87
4 50 5 55 48 29.61 35 25.39
5 50 5 55 44 35.18 20 19.82
6 50 10 60 36 32.64 17 27.36
7 50 10 60 36 27.4 18 32.6
8 25 10 35 33 21.15 16 13.85
9 25 10 35 30 18.66 17 16.34
10 25 10 35 27 18.5 17 16.5
11 25 10 35 23 15.88 19 19.12
12 25 10 35 20 14.66 14 20.34
13 25 10 35 23 17.2 19 17.8
14 25 10 35 26 18 14 17
15 25 10 35 26 15.6 18 19.4
16 25 10 35 26 14.9 14 20.1
17 25 10 35 27 13.42 11 21.58
18 25 10 35 27 17.1 17 17.9
19 25 10 35 30 18.6 15 16.4
20 40 10 50 37 25.5 29 24.5
21 35 10 45 31 27.5 26 17.5
22 40 10 50 31 19.3 23 30.7
23 40 10 50 39 25.8 24 24.2
24 40 10 50 29 27.7 30 22.3
25 40 10 50 28 23.1 26 26.9
26 40 10 50 36 27.4 24 22.6
27 40 10 50 26 27.3 21 22.7
28 40 10 50 31 18.4 22 31.6
From the above table, it was observed that when 25 kg of the RM drying material was used, the average moisture removed per day was 19.8 kg, say 20 kg and when 40 kg of the input drying material (dried biomass) was used, the average moisture removed per day was 24.33 kg, say 25 kg.
ADVANTAGES OF THE INVENTION

1. The method is carried out in 24 hours of operation, i.e. in one day with shredding, blending and pelleting steps taking about 1 to 2 hours each and the drying step taking about 16 to 24 hours.
2. The method is carried out at ‘in door ‘operations and hence is functional in all seasons.
3. The biomass/ fuel pellets are capable of being used as cooking fuel in biomass stoves and also capable of being used in biogas digesters to produce biogas.
4. The method is a highly energy efficient and a cost effective way of drying biomass. The drying step uses very less quantity of electrical energy to effectively remove larger quantity of moisture from the biomass. Conventionally, only one unit of electrical energy, in the form of heat energy evaporates about 1.0 lit of water whereas same one unit of electrical energy, in the form of wind used in the present method, evaporates about 20 lit of water. Thus, the method achieves about 20 kg water removal per unit of air supply.
5. Also, the wet MSW, the so called ‘Garbage’ is converted to ‘Product’ that can be used as fuel that resolves the challenge of waste dumping and the nascence of foul odor.
6. The method is carried out without requiring larger space.
7. The capital cost and the operation cost of the whole operations is quite less, as compared to other ways of waste processing.
8. The final product is salable, thus this method of waste to energy is economically viable and environmentally sustainable.

The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, and to thereby enable others skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omissions and substitutions of equivalents are contemplated as circumstances may suggest or render expedient, but such omissions and substitutions are intended to cover the application or implementation without departing from the spirit or scope of the claims of the present invention.