Indi an Jou rn al of Chemical Technology Vo L6 , Jul y 1999,p p. 185- 193 Rheological properties of concentrated distillery spent wash and some metal corrosion studies Jagdish Thampi & A niruddh a B Pandit" Division of Che mi ca l Engineering, Department of Chemical Technolo gy, University of Mumbai, Matunga , Mumb ai 400019, In dia Received 3 July 1998; accept ed 14 June 1999 Spent wash generated by the alcohol distilleries is a major so ur ce of ground water pollution. Various treatment strategies. whi ch include aerobic, anaera bic digestion, thermal treatment and incinera ti on have been adopted with reasonable success. For th e rigorous engi neering ana lysis of any of th ese processes, the information regarding the physico-chemical prop erties of this eflluent such as density, surface tension and viscosity lire essentia l. The rheological properties of concentrat ed distillery wastes at room temperature and elevated temperatures were measured. The rheological properties have been correlated to so lid concentration of the waste in the dissolved and suspended state at room tempe rature. For highly concentrated wastes (viz. 50 % and 60 % by weight of solid co ncentrati on) the va ri a ti on in rheological properties with temperature were also studied. A rheological model has been used to explain the observed results. Th e Bingham model was found suitable to ex pl ai n the rheological properties of the co ncentrated distillery wastes at ambie nt temperature and elevated temperatures. Th e corrosion rates of different materials during evaporation of distillery waste were also measured in order to find out a suitable mate ri al of construction to handle distillery waste during co ncentration. Spent wash originating from sugar cane molasses distillery is a major source of ground water pollution in tropical countries like India and Brazil where cane molasses is the main raw material for ethyl alcohol production. Various treatment strategies, which include aerobic, anaerobic digestion, thermal treatment and concentration/incineration have been adopted with reason abl e success. For the rigorous engineering analysis of any of these processes, th e information regarding the physico-chemical properties of the effluent such as density, surface tension and viscosity are essential. For incineration of this waste (spent wash) it is necessary first to concentrate the waste, so that its ignition tS sustained and continuous. This concentration is usually carried out in multiple effect evaporators. Due to acidic pH and chloride contents of the spent wash, these multiple effect evaporators are prone to severe corrosion. Thu s to design an effective in c in eration system including concentration, or for that matter any form of treatment the following information/characteristics of the effluent are required : a) Boiling point and Ignition temperature i.e. flash point and fire point and so li d concentration relation to 'For maintain the required furnace temperature. b) Rheological properties of the waste (spent wash) at various solid concentrations and at different temperatures, required for an efficient atomizer an d burner design to bum the concentrate in a suitably designed furnace. Also for the estimation of th e heat transfer characteristics during evaporation! concen- tration. c) Corrosion rates of various metals in the spent wash during the concentration of the same. d) Density and surface tension to accurately estimate the expected heat transfer coefficients in the concentration/evaporation. This will allow the estimation of the required heat transfer area accurate I y. The information regarding the rheological properties could also be effectively used for th e design of aerobic, anaerobic treatment schemes as the rates of gas transfer, be it oxygen during aeration or methane and carbon dioxide during anaerobic digestion, are strongly influenced by the rheological properties of the liquid. The distillery waste is a complex, structured fluid. Rheological analysis of this multiphase system can provide information au o ll t eac h phase. as well as about the interaction between solid and li quid phases.