Page 106 - Energy from Toxic Organic Waste for Heat and Power Generation

Paper Industry Wastes and Energy Generation From Wastes 91

generation for the paper mill which will reduce its natural gas expenditure
3
by 18 Mm /year [19].
Supercritical water gasification (SCWG) is a variant in the gasification
theme, which is in fact a thermal decomposition and hydrolysis process
amalgamation. In addition to the conversion of organic material into syn-
thesis gas, it also acts as a parting process by permitting the inorganic mate-
rial recovery. The prime advantage is that the SCWG can be applied for wet
sludge without drying process and studies on its applications for the paper
industry wastes are in progress [20, 21].

7.4.3 Pyrolysis

Pyrolysis involves the process of organic matter decomposition in the ab-
solute absence of oxidizing agent that takes place in the temperatures of
280–850°C. With the difference in heating rate and residence time, reaction
temperatures, and the relative yields of the solid (bio-char), gaseous (biogas)
and liquid (bio-oil) products formed, this process is divided into three main
types, namely slow, intermediate, and fast pyrolysis.
In similar to the gasification process, pyrolysis also necessitates the low
moisture content feed material [16]. Pyrolysis is a way of thermally upgrad-
ing waste and biomass into higher calorific value fuels. Already, a pyrolysis
plant which uses plastic fraction of rejects from the recycling of beverage
cartons in paper and board industries as a fiber source was installed and is
operational for a number of years in Spain, and it delivers the end products
of pyrolysis also to clean aluminum for recycling.
Conversely, pyrolysis of sludge is still under development. Numerous
examples on this research can be identified in the literatures [22–25]. An
approach to incorporate it into paper mill energy system would be the use
of oil as fuel on-site and co-firing the gas and char for heat generation to
dry the sludge and using steam for generating electricity [16]. From this use
of natural gas for combusting, the sludge would thus be eliminated. Yang
et al. [26] found that the pyrolysis oil derived from deinking sludge has few
characteristics that could possibly restrict its application in diesel engines,
but also suggest that these could be toned down by blending with biodiesel.
It could also be likely transformed to other liquid fuels or chemicals, but
this should first need quality enhancement like sludge pretreating [27]. The
char could also find exterior uses in soil improvement or as fertilizer; for ex-
ample, char obtained from deinking sludge has confirmed its environmental
remediation ability on polluted soil with nickel [28]. The sludge pyrolysis
also acts as a technique for separation, presenting reclaimed inorganic fillers