WET ELECTROSTATIC PRECIPITATORS
Scheuch offers two Wet Electrostatic Precipitator (WESP) Systems
With the SENA and SEKA systems, Scheuch is able to offer two state-of-the-art exhaust gas cleaning systems based on the principle of wet electrostatic separation.
Basic Principle of Wet Electrostatic Separation and Process Overview
Injecting water (quenching) from the system’s process loop causes the crude gas to cool to its saturation point inside the inlet duct. The crude gas then enters the WESP, where it is uniformly distributed across the entire cross-section.
Prior to entering the electrostatic stage, the gases are further flushed with process water to remove coarse particles and some water soluble organic compounds.
The pre-cleaned crude gas now flows through the electrostatic precipitator stage. This stage consists of a high voltage field on a tensioned wire surrounded by a collecting surface. The particles and aerosols still present in the gas become negatively charged and while flowing through the electrical field they are attracted towards the collecting surface. Periodic rinsing ensures that the collecting surfaces and discharge electrodes remain clean.
The flushing water circulates in a closed loop system which includes an internal water processing component. Sedimentation of dissolved solids in the water is made possible by special surfaces inside the sedimentation tank. The resulting sludge can be removed by a screw conveyor and a downstream
dewatering device. The use of additives ensures high water quality.
SENA is a single-stage WESP equipped with honeycomb shaped collecting surface in the high voltage field. It offers compact design with respect to the ratio between the cross-sectional area and the size of the collecting surface. SEKA is a more sophisticated WESP which usually has a smaller footprint.
The SEKA system is different from a conventional WESP in many important ways. SEKA is a wet electrostatic precipitator featuring a pipe bundle condensation design. In comparison to a conventional WESP, a typical SEKA includes:
- Two high voltage stages
- Condensation system
- Plume removal system
SEKA’s unique system improvement is the two stage HV design, which ensures redundancy during the flushing cycle as well as in the event of a malfunction of one of the high voltage units.
In the condensation system the collecting surfaces are the internal surface of round tubes. Hot dryer exhaust gas travels vertically on the inside of the tubes, while cold ambient air flows horizontally around the outside of the tubes. This creates a cooling effect on the collector surfaces resulting in a condensation film forming on the inside of the tubes. This film prevents the direct contact of the sticky resin particles with the metallic surfaces. In this way the water film created on the inside of the tubes eliminates build-up on the WESP collector surfaces.
This leads to additional advantages:
Since no sediment can form and grow on the collector surfaces, the operating conditions in the high voltage field remain constant. This ensures continuous high removal efficiencies and the frequency of manual cleaning periods is greatly reduced. In addition, the condensation film leads to a drastic reduction in fresh water consumption, which in turn reduces operating costs compared to other wet separation systems. Another important advantage of the SEKA design is the plume removal system. The ambient air warmed by the heat exchange in the condensation system is mixed with clean exhaust air in the stack therefore eliminating the visible plume. Both exhaust gas cleaning systems - SENA and SEKA are equipped with an efficient internal water treatment unit that guarantees safe and reliable operation. These Scheuch technologies are widely used in the particleboard and fiberboard industries, where they are making an important contribution to clean air standards around the globe.