Energy Efficient Jaggery Making Using Freeze Pre-concentration of Sugarcane Juice

Abstract

Abstract Conventional jaggery making with a pan furnace consumes all bagasse for evaporation of water. Hot spots during boiling of juice causes caramelization of sugar. It gives dark brown colour to jaggery, which has low market value. Chemicals like lime, phosphoric acid and hydros powder are used as clarificant to enhance colour of jaggery. Traces of these chemicals in jaggery are harmful to human health. Freeze pre-concentration of sugarcane juice from 20Brix to 40Brix using a reversible heat pump saves bagasse during initial 63% water removal. Water is removed in the form of ice. It requires 335kJ/kg heat removal, which is equivalent to 15% of heat addition during evaporation. Recycling of saved bagasse in field improves the yield of sugarcane. Juice is exposed to -5C during pre-concentration. It reduces inversion of sucrose and expected to improve the quality of jaggery by reduced exposure time to high temperature. Simple cycle analysis for FPCS of juice shows that COP c is 18 with R22 as refrigerant at -8C evaporator and 3C condenser temperature. Overall system COP c is expected, to be in the range of 9 to 12 after accounting for losses like cycling of thermal mass and heat gain from ambient. Power required for 1.5 TR FPCS is 0.5 to 0.6 kW e , which is about 0.1 INR/kg of jaggery produced. Payback period for FPCS is one year. Sugar inclusion in ice is estimated using empirical correlations for flow of solution over flat surface and it is 19.1Brix. Energy consumption, sugar loss and cost of system are estimated. Ways of reducing sugar loss are investigated along with repercussion on energy consumption and system cost. Further experimental investigations on sugar inclusion in ice, which forms inside the tube needs to be experimentally tested.