Effect of different washing parameters on the fuel properties and elemental composition of wheat straw in water-washing pre-treatment. Part 2: Effect of washing temperature and solid-to-liquid ratio

Abstract

The present work is the second part of a study conducted to evaluate the effect of basic parameters on the efficiency of water washing pre-treatment. As per the results of Part-1, large sizes and shorter washing durations are favourable for industrial applications, yet low to moderate fouling and corrosion can be expected from them on combustion. The aim of the present study was to further improve the efficiency of the washing pre-treatment for rather short washing durations (5 and 10 min) and a large feedstock size (3 cm) by optimizing the temperature and solid-to-liquid (S:L) ratio. The washing temperatures considered were 20 °C, 40 °C, 60 °C, and 80 °C, while the S:L ratios considered were 1:15, 1:20, 1:30, 1:40, and 1:50. Fuel composition, heating values, energy loss, and fouling and slagging propensity were evaluated. Increasing the washing temperature resulted in the greater removal of ash (25–37%), K (42–55%), Cl (60–81%), S (32–61%), Mg (52–68%), N (17–25%), P (11–37%), and Ca (14–29%). On increasing the S:L ratio, improvement in the removal of ash (27–35%), Cl (73–84%), S (41–59%), and N (21–40%) was also observed. For practical applications, an S:L ratio of 1:15 was found adequate compare to higher S:L ratios. The washing of 3 cm sized wheat straw for 10 min at 40 °C with a 1:15 S:L is recommended for industrial applications, as it shows the least fouling propensity and energy loss.