In the past few years, FLSmidth has launched a series of specialised fabric filters designed to cope with the frequent variations of plant and process conditions. Yet, as cement producers are constantly looking to squeeze more out of their capacity, bottlenecks occur as a higher output is forced through a filter system that was not designed to deal with such loads. This compromises the system’s filtering efficiency and places cement plants at risk of steep fines. Adding further to this cost is the need to replace damaged filter bags that have been pushed beyond their limits.
Many years of research and experience in cement mill filter applications has made it possible to redesign a number of parameters in the fabric filter and to refine the control of fabric filter systems. In an effort to meet the needs of modern cement mills, FLSmidth sought input from cement producers, who aimed to increase efficiency and reduce the operational costs of filter systems.
Cement producers clearly required efficiently-controlled fabric filters with low energy consumption and long filter bag lifetime. In response to this demand and the input received from producers, FLSmidth further developed the design of the fabric filter. This resulted in the release of the FLSmidth SmartBag®, which allows up to 15% more filtration area in the same fabric filter. In addition, the filter’s steel weight is up to 7% lower, yet it retains the same performance capability of its predecessor.
While the technology backing the fabric filter is important, an equally important factor is the way in which the filter system is controlled. Today's fabric filter controllers normally only adjust to the differential pressure (dP) across the entire filter. This means that the filter system maintains a certain dP. without consideration for filer bag conditions and actual dust load from the cement mill. This is not ideal, as the main fan will have to maintain one pressure at all times despite fluctuating work conditions and loads. Under such conditions, the main fan consumes an undesirable amount of energy.
As filter bags age, the amount of dP required to flow through them is often higher. However, traditional controllers do not recognise changes in filter bag condition and will not adjust accordingly. The results the requirement of constantly cleaning the filter system, compromising the length of filter bag life and energy consumption levels.
FLSmidth recognize this challenge and has developed a next generation of air filter controllers. The SmartPulse EVO II controller continuously analyses specific filter operating conditions, based on the rate of change of differential pressure across the filter, which is driven by the load from the cement mill.
The SmartPulse EVO II adjusts filter cleaning parameters to cater for fluctuating plant operating conditions. This ensures that only the minimal required cleaning is carried out at any given time. This smarter way of cleaning reduces costly compressed air usage and extends filter bag life.
Figure 2 shows the SmartPulse EVO II following the actual load from the cement mill. The dP settings in the filter controller will always follow the actual dP, as indicated by the red line.
“We have noted performance improvements in the mill’s inlet pressure, as a result of the new smart bags’ increased filtration area,”