製糖工場の未利用熱蓄熱輸送システムにおける乾燥工程へのゼオライトボイラの適用

抄録

In Tanegashima, sugarcane cultivation and sugar manufacturing are main industry. The sugarcane bagasse from sugar manufacturing process is burned in bagasse boiler and supply heat and electricity demand in the sugar mill. The bagasse boiler exhaust unused heat about 200 °C during milling period due to combustion of excess sugarcane bagasse. In the island, there are some factories such as food processing factories consuming imported heavy oil to generate around 120 °C pressurized steam through a year for their processes. Thermochemical energy storage and transport system utilizing zeolite steam adsorption and desorption cycle can resolve this spatial and seasonal heat mismatch. The “Zeolite Boiler”, which can generate 0.2 MPa/120 °C steam continuously by employing moving bed and indirect heat exchanging process, requires adsorption steam generated by an existing boiler to release stored energy of zeolite. Thus, reduction of steam consumption from the existing boiler is essential to increase in revenue. Food processing factories use steam for their indirect drying process and exhaust high-temperature/humidity air which can be introduced into the Zeolite Boiler replacing boiler steam. A bench-scale Zeolite Boiler with 10 kg/h of mass flow rate of zeolite demonstrated the increase in heat increasing rate by introducing high-temperature/humidity air. A numerical model validated experimentally predicted the performance of a full-scale Zeolite Boiler and showed increase in fuel reduction rate by 32% point comparing the normal Zeolite Boiler without high-temperature/humidity air. While introducing high-temperature/humidity air increases fuel reduction, pressure drop in packed bed is expected to increase and increases corresponding power consumption of blower. By introducing RH=40% air into the Zeolite boiler, the revenue from fuel reduction is expected to overcome increase in electricity cost of blower.