Material and heat flow analysis in thermal energy storage and transport system utilizing unused heat from bagasse boiler

Abstract

Sugar production is the main industry in Tanegashima, Japan. Whilst the sugar mill recycles sugarcane bagasse as a fuel, it concurrently generates large amounts of unused 200 °C heat during operation. Raw sugar is shipped to a refinery in Osaka for the final stages of production, which uses a city gas boiler to continuously generate a large quantity of 150 °C heat. However, factories in Tanegashima need a continuous supply of process steam at temperatures of up to 120 °C. To resolve this spatial and seasonal mismatch of heat, we propose a thermal energy storage and transport system using a zeolite adsorption/regeneration cycle. A process flow diagram of the sugar mill has been developed, and the amount of available heat, the potential storage capacity, and the transportable amount of heat have been calculated. Two scenarios were analyzed, in which the stored heat is shipped to Osaka, or used on the island. This was achieved by calculating the rate-based storage capacity of zeolite, based upon an adsorption and regeneration test. The transportable quantity of zeolite determines the feasibility of using waste heat. In the first case, transport of heat to the sugar refinery in Osaka has little possibility of being implemented. In the second case, transport of heat to a liquor factory in Tanegashima can potentially reduce its usage of heavy oil by 83 %, equivalent to 33 kL/year.

Keywords

• heat storage
• biomass energy
• zeolite adsorption and regeneration cycle
• sugarcane bagasse
• sugar milling process
• unused heat utilization