New technologies from FLSmidth are helping to maximise waste heat recovery for today’s cement producers – without compromising recuperation efficiency.
As cement producers are continually looking to improve the performance of their existing assets, many are seeing the upsides of bringing waste heat recovery into the production process. In particular, integrating a waste heat recovery system (WHRS) into the clinker cooler is highly attractive, providing compelling reasons for retrofitting and upgrading the clinker cooler.
But producers face several challenges if they are to get the full benefit, including the need to balance specific fuel consumption against waste heat recovery power generation. The key is to maximise waste heat recovery, while maintaining high recuperation efficiency.
Seeking greater productivity
Coolers are often the cause of operational bottlenecks. Reduced recuperation efficiency, increased vent losses, high clinker temperature and insufficient heat input to the WHRS boiler are just a few. These bottlenecks add to the complexity of day-to-day operations and maintenance, creating inefficiencies in the pyro processing systems and ultimately undermining the plant’s commercial performance.
Fortunately, coolers that include waste heat recovery technology are providing cement producers with compelling opportunities to improve equipment efficiency and plant productivity. Cooler performance is to be optimised prior to WHRS integration.
The performance of clinker coolers is not just about recuperation efficiency and energy ; it is also necessary to consider maximum heat recovery for WHRS generation. A common assumption is that an efficient cooler can only support higher recuperation and, in turn, provide lower heat for the WHRS. But it is possible to improve cooler recuperation efficiency and WHRS performance via FLSmidth Cross-Bar® cooler – through supplying more heat to the WHRS boiler – by using innovative cooler concepts, such as hot air recirculation from the cooler stack.
Solution for maximising WHRS
Applying innovative technologies to achieve energy-efficient pyro processing solutions is a key focus area for FLSmidth, which has supplied equipment and services to the cement industry for more than 135 years. FLSmidth has pioneered the development of WHRS to optimise heat recuperation and energy efficiency in clinker cooler systems.
Integrating WHRS into the FLSmidth
Cross-bar® cooler is ideal for either new coolers or retrofits. This combined solution sets industry benchmarks in recuperation efficiency, power consumption, maintenance costs and overall reliability. It enables the recirculation of hot air, maximising heat recovery from mid-air for WHRS generation.
Hot air recirculation concept
The cooler’s hydraulic cylinders can be relocated such that hot air recirculation is made available to most of the compartments as necessary to improve mid-air temperature and volume. All under-grate components, including support rollers, bearings, seals and lamps, are designed to operate at a hot air recirculation temperature of approximately 130°C.
The hot air is recirculated into selected cooling fans supplying air to the mid-air zone. There are no hazards associated with hot air recirculation into the cooler’s compartments, and this concept can be easily integrated into the cooler layout.
All essential safety aspects and operational parameters have been considered in the design. This includes hot air fans being placed on one side, careful duct routing to avoid unwanted pressure drop, and the shut off and bleed air dampers being positioned correctly at the hot air recovery duct. The recirculation of hot air provides approximately 15-20 percent more heat for mid-air.
FLSmidth has successfully delivered solutions for recirculating hot air to clinker coolers since the early 1980s.
Through the years, different solutions have been developed depending on the specific needs of the facility. Especially for coolers in the US and Canada, the driving force is to meet emission regulatory requirements, where emissions of cooler vent air – both partial and full – are highly undesirable. Essentially, solutions here involve reintroducing the vent air into the cooler compartments as well as modifying the ducting and cooler control scheme to allow hot air recirculation. For coolers in Korea, India and Nepal, the main objective is to maximise WHRS generation.
Crucially, any FLSmidth cooler can be upgraded to include hot air recirculation. The solution can either have partial or 100 percent recirculation, depending on the project’s specific needs and maximising waste heat recovery potential.
Making the best even better
FLSmidth Cross-Bar® cooler design alongwith WHRS integration have made it possible to meet customer demands like reduce vent losses, improve recuperation efficiency, and maximise WHRS generation.
Cement producers choose to implement innovative technology, consider hot air recirculation from stack to cooler compartment’s so as to maximise waste heat recovery without compromising efficiency of clinker cooler.
Author: G Renga Prasad, Product Line Manager-Pyro, FLSmidth.