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When deciding on the most suitable flue gas desulphurisation technology, the location is sometimes the key. Flue gas desulphurisation plants based on seawater offer a proven and economical technology that is suitable when the plant is located on the coast. Instead of the limestone that is normally used in wet scrubbing processes, seawater is the only absorbent used. The principle is impressively simple: The sulphur dioxide from the flue gas is dissolved in the seawater and forms sulphite and hydrogen sulphite. These compounds are neutralised by carbonates and bicarbonates, which are present as natural components of seawater. Oxygen is then added in an oxidation basin, the sulphur compounds oxidise into sulphate, a natural component of seawater too. Normally, seawater from the cooling water circuit of the power station is used. After the treatment in the oxidation basin, the water can be released again into the sea. Naturally, all stipulated discharge conditions are met by the process. The method does not create any residues. Despite the astonishing simplicity of the method, we achieve sulphur dioxide separation rates of up to 99 %.
The seawater desulphurisation technology by Steinmüller Babcock Environment uses a spray tower as an absorber. All that is installed in the spray tower are the spray levels with the spray nozzles, and the droplet separator before the scrubber outlet; there are no additional turbulence units or stages with packings, through which the flue gas is led. Refraining from installing these additional units minimises pollution from seawater components or from biological vegetation. The pressure losses are also extremely low. The spray levels for dispersing the seawater are integrated in the upper section of the spray tower.
We choose the number of spray levels depending on the seawater characteristics and the level of desulphurisation required. By means of CFD (Computational Fluid Dynamics) we optimise the distribution of gas and seawater in the absorber. Each spray level is fed by its own individual pump, so that the desulphurisation capacity can be adjusted to the requirements or plant load at any time. This allows extremely energy-optimised operation for the entire load range. In the upper section of the spray tower we install a multi-layer droplet separator, which prevents the droplets produced in the spraying area from being carried out of the absorber. Due to the process control and the special design of the droplet separator, no separate rinsing of the droplet separator is necessary.
The oxidation basin can be placed either directly beneath the spray tower, or externally at a site of your choice. If the basin is integrated beneath the spray tower, the first oxidation stage can be integrated in the absorber. We have developed our own design that allows a space-saving installation with controlled water inflow and the staged, controlled addition of oxidation air. The optimised oxidation and effective CO2 stripping (transfer of carbon dioxide to the gas phase) guarantees safe compliance with required oxygen concentration and pH values in the drained seawater, with the best possible utilisation of the alkalinity of the water for flue gas desulphurisation.
The external basin, with a similar process control, is installed as a rectangular basin at a site of your choice and connected to the spray tower by means of a connecting pipe.
Advantages of seawater FGD