The great advantage of the new system lies in its integration into the existing preheating process. During cement production, raw meal is ground in the raw mill and dried. The meal then moves into the preheater tower. Until now the isolated filter dust was fed back into the preheater tower. As a result, the concentration of mercury steadily increased with each cycle. The new xmercury system interrupts the circulation of mercury in an innovative way.
The filter dust enters the split preheater. There, the filter dust is reheated, as is already the case in the usual preheater tower. This causes the mercury bound to the dust to escape. The hot, mercury-free dust is then separated in a high-performance cyclone and the newly developed hot-gas filter. The dust is eventually guided to the main preheater tower and remains in the actual clinker burning process without losing any heat.
Next, the mercury-laden, dust-free exhaust gas is cooled to the final temperature of 100–120 °C. This enables energy to be recovered from the process at low cost. The sorbent is then added (for example, activated carbon), which binds to the mercury. A bag filter then separates the additive from the clean-gas stream. When the sorbent is recirculated, it is enriched with an unusually high concentration of mercury. This in turn ensures maximum usage of the sorbent and leads to extremely low consumption. As a result, the disposal volume of the mercury-laden, enriched activated carbon is very low.
Ultimately, an extremely high degree of separation can be achieved in the main kiln with the small xmercury system.