Page 155 - Energy from Toxic Organic Waste for Heat and Power Generation

Hazardous Waste and Its Treatment Process 135

Table 9.4 Comparison of three thermal processes
Pyrolysis process Gasification process Combustion process
No air is passed Substoichiometric range Excess air is passed
of air
Only heat in internal or Minimum total Maximum volumetric
external side volumetric flow flow
Liquid, gases not desired Minimum fly ash carry Fly ash carry over
over
Pollutant in compact Pollutant in compact Pollutant in oxidized
form form form
Maximum char Char at minimum Bottom ash
temperature verified
slag at high
Range: 10 tons/day Range: 100 tons/day Range: 1500 tons/day
No additional oxygen Some additional oxygen More additional oxygen
only heat or air or air

9.4.3 Biochemical Process
a. Transesterification: Transesterification is the process of removal of
wastes present or MSW. In the process, some amount of catalyst or
alcohol is added; triglyceride in which reacts with the MSW and pro-
duces biodiesel. The catalyst is NaOH or KOH which finally forms
municipal ester oil or glycerol. Let’s take a sample with some limited
quantity of waste and add methanol or ethanol into 250–300 mL of
methanol and then heat at 60–70°C and maintain with a room tem-
perature. This process can be done continuously and maintained five
to eight of time and stirrer ling the process continuously. After the
completion of this process, we get a final solution which is nearly
85%–90% of pure methyl ester. Simply, the process is called transester-
ification. The process can produce purest form of ester or biodiesel.
b. Fermentation: Fermentation is the process of converting the organic
waste into acid or alcohol, ester. In the process, oxygen is not used and
instead hydrogen is used; it can liberate the nutrients and also heavy
residue ratio. Yeast fermentation process is the combination of both
batch and continuous fermentation [25]. The materials are ethanol
plants or materials larger in size. It can deposit at a time two to three
lacks of tons as collected per day. Sugar wastes are more suitable for
preheating and cellulosic materials are collected from different sources
like thermal treatment and acid treatment. Enzymatic processes are