(215a) Supercritical Water Oxidation: the Next Generation Process to Incineration

SUPERCRITICAL
WATER OXIDATION AS THE NEXT GENERATION IN HAZARDOUS WASTE TREATMENT

Bushra Al-Duri^1[*],
Faihan Alsoqyani¹ and Iain Kings¹

¹ School of
Chemical Engineering, University of Birmingham, Edgbaston
– Birmingham B15 2TT, UNITED KINGDOM. Email: B.Al-Duri@bham.ac.uk

Supercritical
water oxidation (SCWO) is an advanced technology, which represents a suitable
alternative to incineration for the destruction of chemically stable wastes.  SCWO is an intense, efficient and highly
rapid process that converts hazardous hydrocarbons to benign gases and liquid
water, with no emissions (dioxins, NO_x and SO_x), and no
ashes; eliminating the problem of landfill.  Compared to wet air oxidation it is
multifold more rapid and more efficient as it takes place in a one-phase
environment, based on the special properties of supercritical water ^[1].
  

Nitrogen
(N) containing hydrocarbons are frequently encountered in wastes.  Their abatement is specifically
challenging due to formation of the recalcitrant ammonia the reason why, this
work investigates the SCWO of N, N dimethyl formamide
(DMF); and aliphatic hydrocarbon found in chemical industries.  This work focuses on the finding that
under the same operating conditions alcohol addition improves the conversion of
organics and nitrogen towards benign gases^[2].
 SCWO of DMF in the presence of
isopropyl alcohol (IPA) is investigated under a range of temperatures (673
– 800K), oxidant ratios (0.8
– 3SR), initial DMF
concentrations (5 – 20mM) and
different IPA/DMF ratios. Results are presented in the form percentage organics
removal, and ammonium yield and total liquid nitrogen yield.  It shows the positive effect of alcohol
addition on the SCWO process.

The
reaction kinetics is also investigated, showing that the activation energy of
65 kJ/mol is significantly lower in the presence of
IPA than without (155 kJ/mol).  The reaction rate constants and global
rate expression, showing the reaction order is also given by:

-rA=3.15x107 exp64,9958.314TTOCO20.297

Figure 1: SCWO of 10mM DMF at 673K, 1SR adding 5, 10 and 20mM
IPA.

[1]
Verianshyah B. & Kim J. D.; Journal of Environmental Sciences, 19 (2007) 513–522.

[2]
Oe T; Suzugaki H; Naruse,
I; Quitain
A. T; Daimon
H & Fujie
K; Ind. Eng.
Chem. Res., 46
No. 11 (2007) 3566–3573.