| The resources of industrial waste heat in China is rich, but the recovery rate is very low, the recovery and utilization of waste heat resources is mainly concentrated in the high temperature region, causing a large number of low-temperature heat waste. On the other hand, due to the rapid development of the city and the increasing of strict air pollution control, small coal-fired boilers in urban areas are demolished compulsively, which results urban heating supply become tighter. Mobilized thermal storage technology is a promising solution for recovery of waste heat,can absorb and store waste heat source, then transport to the heat user to replace the end user-owned boiler. Phase change material(PCM) with high storage density, simple devices, small size, and constant approximation of the energy supply process, is the most suitable material for mobilized thermal energy storage. In this paper, for the waste heat below 100 ℃, Barium hydroxide octahydrate Ba(OH)2·8H2O is chose as the phase change materials in mobilized thermal energy storage.After the thermodynamic analysis, it is found that the influence of environment temperature on the thermodynamic properties could be negligible. The optimal final temperature is 87 ℃ base on the heat storage capacity and exergy efficiency, and the initial temperature of PCM can be defined according to get the maximum amount of stored heat.For the two fatal flaws of subcooling and phase separation of Ba (OH) 2· 8H2O, the experimental study results show that the iron, copper and KH2PO4 can effectively reduce the subcooling degree and the best weight addition is 1% to 3%, at the addition of 3%, the subcooling degree of Ba (OH) 2 · 8H2O are 4 ℃,2.5 ℃ and 2 ℃. The Sodium carboxymethyl cellulose (CMC), polyacrylamide, and magnesium oxide (MgO) can inhibit the phase separation phenomenon of Ba (OH) 2 · 8H2O. But the addition of the CMC and the polyacrylamide can increase the subcooling degree of Ba (OH) 2 · 8H2O, especially for the polyacrylamide. After adding the MgO, the subcooling degree of Ba (OH) 2 · 8H2O can further reduce. The subcooling degree of Ba (OH) 2 · 8H2O with 3% copper and 3% MgO is 1.5 ℃.Finally, the mobilized storage technology of thermal energy storage and economic benefit in the practical application is comparatively analyzed. It is found that using PCM is better than water of heat storage capacity and economic. Comparative analysis of mobilized thermal energy storage and conventional heating supply ways of the energy costs and environmental benefits. The energy costs of mobilized thermal energy storage is less than gas-fired boilers and electric heating boiler heating supply, but higher than coal-fired boilers. The CO2 and SO2 emissions of mobilized thermal energy storage decrease obviously, but the NOx emissions increases compared with coal and gas fired boilers. Total pollutant emissions of coal-fired boiler and gas boiler heating supply are 3.94 times and 2.44 times respectively compared with mobilized thermal energy storage. |
