Agriculture Reference
In-Depth Information
Gupta et al. (1968) were the first to combust vinasse in a fluidized bed. They
concentrated vinasse to 30 - 40 °Brix and burnt the vinasse in a fluidized bed at 700 °C by
spraying it from the top by a spray nozzle using cold compressed air. Hot flue gas, rich in
excess air, from a coke fired furnace was forced through the fluidized bed furnace to burn the
sprayed vinasse.Kujala et al. (1976) investigated and evaluated various options for vinasse
use including evaporation and fluidized bed incineration for crude potash production and ash
treatment for refined potassium salt production. They proposed to use a fluidized bed reactor
as a gasifier and perform the after burning in a waste heat boiler. The crude potash recovered
from the ash, separated by a cyclone, should have 40% K
2
O, 10% CaO, 19% SiO
2
and 31%
others. The potassium salts expressed as a percentage of ash should be in the following order
of composition: K
2
SO
4
56%, KCl 7% and K
2
CO
3
5%. This crude potash containing 65 - 70%
potassium slats can be used as a fertilizer. The ash thus produced can be further processed by
multistage leaching, filtering and neutralising with controlled injection of H
2
SO
4
to convert
carbonates to sulphates, evaporation and crystallisation.The finished product thus obtained at
92% dry solids should have 83% K
2
O
4
, 9% KCl (traces of sodium salt) and 8% moisture.
Basic research has been carried out by Cortez and Perez (1997), who have experimented
with incineration of pure and vinasse emulsions blended with heavy oils, as mentioned
earlier. Although vinasseincineration technology was already presented as being
commercially viable in the early 1980s by some companies, e.g., Alfa Laval and Hollandase
Constructive Group (HCG), in practice, it failed to live up to expectations. From the year
1950 onwards, the firm HCG installed boilers with special furnaces to burn concentrated
vinasse in Holland, Czechoslovakia and Thailand. One such plant is still working successfully
in the Banghikhan distillery in Thailand [Seebaluck, et al. 2008].
A project, started in 2003, for electricity generation from vinasse at Mumias Sugar
Company Limited (Kenya) is being carried out. Vinasse concentrated to 60% solids (wt/wt)
along with bagasse will be fired in a specially designed boiler to produce 22 tonne of steam
per hour at 45 bara and 400
°
C. The boiler will consume 7.54 tonne per hour (TPH) of
concentrated vinasse with 60% (wt/wt) solids. The boiler will use a special design traveling
grate Indian technology, and will burn mainly bagasse on the grate while the concentrated
Vinasse will be sprayed inside the furnace at a height of about 10 meters above the traveling
grate to ensure that all the Vinasse particles burn off in suspension. The steam raised in the
boiler is then expanded through a turbo-generator to generate electricity. The electricity
generating section will consist of a 2.1 MW back pressure turbo-generator with the inlet
steam at 40 bara and 398
°
C. The steam exhausted at 5 bara will be used in the distillery and
for the concentration of Vinasse [UNFCCC, 2011].
2.2. Raffinate
A further biomass material as a result of the sugar producing industry which received
limited attention by researchers is known as raffinate. Raffinate is similar to molasses in
appearance (dark brown) and is fairly sticky, slightly viscous liquid material. Raffinate is
similar to vinasse but with different properties depending upon the process of production.
Raffinate analyses from two different sources are given in Table 6.
