Wet Electrostatic Precipitators

Two convincing systems

With the SENA and SEKA processes, SCHEUCH is able to offer two state-of-the-art exhaust gas cleaning systems based on the principle of wet electrostatic separation. Both systems use the same operating principle.

Wet Electrostatic Separation:
Basic Principle and Process Overview

Injecting water from the system’s process loop causes the crude gas to cool to its saturation point inside the gas pipe. The crude gas then enters the filter, where it is uniformly distributed across the entire filter cross-section. In the downstream gas washer, particulate and gaseous organic compounds are removed

• The pre-cleaned crude gas now flows into the wet electrostatic precipitator. This filter consists of a high voltage field with collecting electrodes and a centrally located discharge electrodes. The particles and aerosols still present in the gas become negatively charged and wander through the electrical field to the collecting surfaces. Periodic rinsing ensures that the collecting surfaces and discharge electrode remain clean.

• The rinse water remains in a closed loop system that includes an internal water-processing unit. Sedimentation of solids in the water is made possible by special, built-in patented sedimentation surfaces in the water collection container. This sedimentation sludge is removed via a screw conveyor and a downstream dewatering unit. The use of additives ensures a uniformly high standard of water quality.

SENA is a single-stage wet ESP equipped with honeycomb collecting electrodes in the high voltage field. It offers compact construction with respect to the utilization of the ratio between its cross-sectional area and the size of the collecting and separation surfaces. SEKA is a further development that — in contrast to SENA — requires a smaller base but a greater height including, under some circumstances, a higher exhaust outlet with improved dispersion characteristics.

The SEKA system is different from conventional wet ESP in many important ways. SEKA is an electrostatic condensation filter featuring a nested pipe design. In comparison to conventional wet ESP, SEKA was expanded to include:

Two-stage design
Condensation system
Vapor removal

• SEKA’s decisive system improvement is the two-stage design, which ensures redundancy during the rinsing phase as well as in the event of a failure in a high voltage unit. Pre-cleaning of the unit’s first stage ensures precision high voltage adjustment.

• In the case of the condensation system, the collecting electrodes are configured as pipes. Hot dryer exhaust gas travels vertically on the inside of the pipes, while cold ambient air is suctioned horizontally on the outside of the pipes. This cooling causes a condensation film consisting of saturated dryer exhaust gas to form on the inside of the pipes. This film prevents the direct contact of the sticky resin particles with the metallic surface. In this way the water film almost totally excludes the possibility of caking.

This leads to additional advantages:

Because no layer of sediment can form and grow, the operating conditions in the high voltage field remain the same. This ensures a continuous and constantly high rate of separation. The frequency of manual cleaning periods is greatly reduced. In addition, the dripping condensation film leads to a drastic reduction in fresh water consumption, which in turn translates to clearly reduced operating costs when compared to other wet separation systems. In another important advantage over conventional wet ESP, the SEKA system offers vapor removal. The vapor removal system mixes the ambient air warmed by the heat exchange in the condensation system with clean exhaust air in the exhaust stack. This eliminates the visible steam vapor trail. Both exhaust gas cleaning systems — SENA and SEKA — are equipped with a powerful internal water treatment unit that guarantees safe and reliable operation. In the meantime, these technologies from SCHEUCH are widely used in the particle and fibre board industries, where they are making an important contribution to clean air standards around the globe.