Off-seasonal fuels for Co-generation plant



 Introduction

 
Sugar industry being a seasonal industry, running a co-generation plant in off-season is not feasible, unless sufficient bagasse has been saved in off-season. Otherwise bagasse has to be purchased from outside, which is always a costly affair. Now days a lot of work is being done world wide on co-generation-technology and equipments, also research is going on to search a suitable ( Commercially and Technically ) alternate fuel.

There are many types of biomass residues that are generated during the normal processes of agriculture farming . These are presently being used for various purposes depending on the local culture, necessities, environment, etc. In India, these generally go either as cattle fodder, for thatching rooftops, for covering the fields to prevent moisture absorption by the agricultural produce, but they also possess sufficient heat value to serve as biomass fuels and are as good as any other fuel for combustion and production of heat. Following list shows some of such alternate fuels which are seen as potential alternate fuel for Co-generation plants:-

Availability of biomass fuels

Type of Agro waste

Quantity (Million tonnes / annum)

Straws of various pulses & cereals

225.50

Bagasse

31.00

Rice Husk

10.00

Groundnut Shell

11.10

Stalks

02.00

Various Oil Stalks

04.50

Others

65.90

Total

350.00

 

 Cane trash for use as boiler fuel 

 

Of the other biomass fuels for a typical sugar plant, cane trash offers a very good scope as alternate fuel. Basically, it is present along with the sugarcane and its availability is assured. It is available @ 8-15 dry tonnes per hectare at harvest. It also dries up to 15% moisture and has a better heat value than bagasse(see table below)

 Analysis of various biomass fuels

 

Bagasse

Cane Trash

Cotton Stalk

Moisture (%wet basis)

50.00

20.00

9.50

Volatile Matter

41.50

51.00

77.14

Fixed Carbon

7.00

19.00

10.30

Ash (% dry basis)

1.50

10.00

3.06

Gross heat value (MJ/kg; dry basis)

9.50

15.05

17.37

The only problems that need to be sorted out are its transportation and storage. Cane trash has been effectively burnt along with bagasse in a sugar plant in Brazil to the extent of 15%. The  cane trash can be baled with the help of hay balers and delivered to the mill. The cost of baled trash is reported to be about half the cost of oil fuel. The baled trash has also been stored for upto six months with no appreciable degradation. With these experiences, it is believed that for Indian conditions, cane trash offers good scope as an alternate fuel along with bagasse for year-round operation of the cogen plant.