The semi-dry process is a proven and well-established solution for the removal of pollutants such as SO2, SO3, HCl, HF, dioxins, furans and heavy metals including mercury. It uses hydrated lime or quicklime as the primary reagent and is typically supplemented with activated carbon or HOK® activated lignite.

We offer the dry FER-DI® process (Flexible Economic Reagent Direct Injection) as a straightforward and costeffective solution for applications with moderate pollutant concentrations. This technology reliably removes acidic gases — including SOₓ, HCl and HF — as well as dioxins, furans and heavy metals such as mercury. Sodium hydrogen carbonate is used as the main additive and is injected together with activated carbon or HOK® activated lignite.

Depending on the size of the plant and individual requirements, electrostatic precipitators, high-pressure pulse jet fabric filters (HPPJ) or low-pressure pulse jet fabric filters (LPPJ) are used – each with high efficiency for separating dust particles.

Wet scrubbers utilize consecutive acidic and alkaline stages to maximize pollutant removal. In the acidic stage, contaminants such as HCl, HF, NH3 and mercury are efficiently separated from the flue gas, while the subsequent alkaline stage primarily removes SO2, SO3 and remaining residual substances. Commonly used as an additional flue gas cleaning step, wet scrubbers enable the achievement of very low emission limits with moderate consumption of reagents.

In addition, limestone scrubbers are commonly employed to remove acidic pollutants, especially in flue gas cleaning downstream of sewage sludge incineration plants.

In addition to primary combustion controls, proven secondary processes such as selective non-catalytic reduction (SNCR) and selective catalytic reduction (SCR) are used to effectively lower NOₓ emissions. In SNCR, ammonia water (NH4OH) or urea (CO(NH2)2) is injected into the flue gas stream at high temperatures, where it reacts with nitrogen oxides. SCR, on the other hand, employs a catalyst, enabling higher NOₓ reduction efficiencies and allowing the reaction to proceed within a lower temperature range.

Advanced systems for heat recovery from the flue gas stream enable the captured energy to be reused in internal processes or supplied to external applications. This makes a significant contribution to the overall energy efficiency of the plant.