Improved waste heat recovery through surface of kiln using phase change material

Abstract

The heat losses that occur from the surface of the rotary kilns during calcination process are a major source of waste heat in cement production industry. In order to recover this heat, a multi-shell heat exchanger that forms an annular duct over the high temperature zone of the kiln is used. The phase change material (PCM) paraffin wax with a melting point of 68 °C is filled in between the gap of the two concentric annular steel shells which are thermally insulated from the outside. In order to draw a comparison and to establish that phase change material improves the waste heat recovery, the heat exchanger model made up of mild steel, which extracts waste heat from a kiln, is experimentally investigated with and without the tertiary shell that contains the phase change material. The outer surface of the heat exchanger is insulated by glass wool, and to facilitate the passage of air between the shells for heat transfer, a variable speed centrifugal fan (for variable flow rate) is installed. The results show that the waste heat recovery rate is increased by 3% to 8% (depending on different air-flow rate) with the use of phase change material. This implies that phase change materials such as paraffin wax can be used in heat exchangers to obtain an improved waste heat recovery rate.

Energy Recovery in Air Conditioning Systems: Comprehensive Review, Classifications, Critical Analysis, and Potential Recommendations

“…Phase change material (PCM) is a method of thermal storage that uses sensible heat, latent heat, and thermochemical reactions to absorb and release heat [74]. Recently, PCM has acquired high interest among researchers, and a considerable amount of research has demonstrated the potential of PCMs [75].…”

Preparation and thermal properties analysis of fatty acids/1-hexadecanol binary eutectic phase change materials reinforced with TiO2 particles

“…PCM utilizes its properties of high latent heat and stable phase transition temperature during the thermal energy storage/release process to achieve high density energy storage and reduce temperature fluctuation [5][6][7]. Therefore, the PCM is widely used in various applications such as building energy conservation [8,9], waste heat recovery [10], solar energy utilization [11], energy storage system [12,13] and fabrics [14][15][16].…”

Dynamic modeling of the heat transfer process in rotary kilns with indirect oil heating: Parametric analysis of gypsum calcination case

“…In many studies, they used numerical computer simulations, which can reduce costs and time to execute engineering projects [8]. Approaching the analysis of the calcination process in rotary kilns, the literature reports many works related to the formation of cement [9], including those related to energy recovery and increased system efficiency [10] and almost nothing when the objective is to obtain plaster, where studies concentrate on its basic thermochemical aspects [11], on the dynamics of operation control [12] and exergoeconomic analysis of the kilns [13].…”