Hydrothermal liquefaction (HTL) is an excellent technique to treat industrial wastes as well as wastewaters simultaneously to produce fuels and chemicals. Two separate studies, involving black liquor from paper and pulp mills, and textile/chemical wastes from tube manufacturing plants will be discussed during the presentation.
Black liquor is a complex aqueous by-product from the paper and pulp industry comprising of lignin residues and inorganic chemicals such as NaOH and Na2S. Valorization of black liquor through HTL is a sustainable alternative to the current practice of burning it in boilers to generate bioproducts and biochemicals. In this experimental study, HTL experiments on hardwood black liquor from Eucalyptus were carried out, and the influence of process variables such as temperature (250 – 400 oC), biomass loading (7.5 – 30 wt.%), and residence time (15 – 60 min) on yield and quality of the products is studied. Phenols, aliphatic hydrocarbons and ketones were the major organic compounds detected in the liquid product. Increasing the operating temperature led to enhanced selectivities to phenol, cresols and xylenols. Maximum selectivity to phenol (23.7%) was obtained at 350 oC, 30 min and 15 wt.% solid loading.
In a separate study, a mixture of industrial wastes containing textile and chemical wastes were co-liquefied using industrial wastewater from at different compositions and temperatures (300 – 350 oC) to produce bio-crude. The bio-crude was further distilled between 150 and 350 oC, and the physicochemical and thermophysical properties of the distillate was characterized. The distillate was rich in C13 – C24 aliphatic hydrocarbons with a H/C mole ratio of 1.86. The distillate is then blended with commercial diesel at 5 and 10 vol.%, and the blends were tested in IC engines, and their performance and emission characteristics were benchmarked with commercial diesel. More details to follow during the presentation.