Maximising waste heat recovery with FLSmidth Cross-Bar® Cooler
Energy-related expenses in the cement sector, mostly on fuel and electricity, account for 30 to 40 percent of the industry’s cash costs. As cement producers are on the look-out to improve the efficiency of their equipment and reduce the energy costs, the utilisation of heat from clinker cooler to the waste heat recovery systems (WHRS) has become highly significant and an attractive proposition.
WHRS are revolutionary, energy-saving power generation systems that recover and reuse energy which enables greater energy security for cement companies in addition to adhering to the regulatory norms and policies.
The major challenge that comes along with WHRS via clinker cooler arrangement is to maintain maximum efficiency in both systems – power generation through WHRS as well as the specific fuel consumption (SFC) in the pyro system. Hence, the performance of clinker coolers is not just about high recuperation efficiency anymore. With the experience and know-how of the FLSmidth cooler experts, the latest generation Cross-Bar Cooler has been developed with innovative features and has achieved many proven results for maximising heat recovery together with highest recuperation to the pyro process, enabling cement producers to achieve lowest operating costs.
A significant factor to optimising the WHRS-clinker cooler system is the positioning of the mid-air/hot air tapping between the recuperation and the cooler vent. As indicated in the below diagrams, if the tapping is placed too close to tertiary air duct (TAD) in the recuperation zone for higher temperature hot air and hence higher heat recovery, it will take a toll on the recuperation temperatures and the cement producer will have to bear the hidden penalty of additional specific fuel consumption. As the tapping point cannot be altered, the consistency in the recuperation efficiency is another key to maximum heat recovery. FLSmidth Cross-Bar Cooler separates the clinker conveying and air distribution systems. Reciprocating bars effectively convey, mix and shear the clinker within the cooler and as the bars gradually wear over time, there is no effect on cooler operation and the thermal efficiency stays high. This also means that the heat output from mid-air tapping will be high and consistent. With the help of mid-air tapping, ~ 0.80-1 kg/kg cl at 390-415 degree centigrade heat can be utilised considering 76 percent thermal recuperation efficiency and 95kcal/kg cl standard cooler loss at grate loading ≤42 tpd/m²*.