FLUE GAS HEAT RECOVERY
FERGY AS in cooperation with Save Energy AB is offering flue gas condenser which is a highly efficient system that recovers the sensitive, latent heat from polluted flue gas.
The heat from the flue gas is extracted via the injected process water. In doing so, the sum of all water droplet surfaces creates a heat exchanger.
This results in heat exchange surfaces that are the size of several football pitches. The water droplets continuously reform. The SaveEnergy heat exchanger (water droplets) can neither become soiled nor corroded. This results in low-maintenance, robust operation and sets top standards regarding availability and durability.
The technology in detail
In the SaveEnergy flue gas condenser, the sensitive, latent heat from the flue gas is recovered. In doing so, the heat from the flue gas is extracted via the injected process water. The surfaces of the many small water droplets assume the function of a mechanical heat exchanger. The heat from the flue gases is absorbed by the liquid and emitted via a plate heat exchanger to the heat consumer (e.g. fed into the heating network). The large heat exchanger surface (the sum of all droplet surfaces) guarantees a high level of efficiency in heat recovery. The flue gas is cooled down to 2–3°C above the temperature of the heat consumer. As there is no mechanical heat exchanger in the flue gas, the SaveEnergy condenser is not subject to soiling.
The SaveEnergy dry electrostatic precipitator is designed as a plate separator. A controlled high-voltage field of up to 70 kV is generated at the discharge electrodes. A high field-strength is created directly around the discharge electrodes. In this active zone, the free electrons are highly accelerated (gas discharge). This so-called ionisation is associated with a slight glow, which is known as a corona. The corona discharge at the ends of the discharge electrodes creates gas ions which adhere to the dust particles and impart an electrical charge to them.
The charged particles are then drawn into the separating chamber through which the gas is flowing, and transported, across the direction of the gas stream, between the discharge and collecting electrodes to the electrically earthed collection plates (anodes), and thus separated from the gas stream. This flow, which moves from the active zone through the passive zone to the collecting electrode, is known as “electric wind”.
The separated particles form a layer of dust on the collecting plates. Since the collecting plates are earthed, the dust particles lose their charge and can be cleaned away mechanically. Hammer blows from two rappers are delivered at differing pre-set intervals to both the collecting plates and the discharge electrode frames. The dust particles are loosened by the mechanical shock waves and fall into the collecting hoppers. The heating system operates continuously throughout the whole process, thus ensuring very high availability.