Ingenious absorption system

For normal wet de-sulphurisation of flue gases the limestone is dissolved in water, therefore the sulphur oxides have to diffuse through a water phase to enable the reaction between them and the limestone to take place. However if flue gases are brought in contact with a slightly damp, gypsum-free limestone surface, the sulphur oxides will react instantly.

"Total cleaning" of sulphur oxides

The Intervex process takes place in a counter flow reactor with central top feeding of limestone. The reaction zone is designed as a conical bed, through which the flue gases flow vertically upwards. Due to an even distribution of the flue gases over the entire reactor surface, via radial "spokes" from a ring shaped chamber at the periphery, it is equally distributed through the bed.

The reaction between limestone and gas is dependent on moisture. Water is therefore sprayed over the bed. Alternatively, the flue gases are cooled by alternating between two reactor beds. These beds are in turn cooled by air, whereby the water vapours from the flue gases will condense on the cold limestone surfaces.

With the Intervex reactor, the emissions of sulphur oxides and hydrogen chlorides can be so low such that detection by common measuring methods is not possible.

Intervex lime stone reactor

Optimal utilisation of limestone

Due to the clever design of the reactor the downward, slow and continuous movement of limestone will flow equally and controlled in all parts of the bed.

From the reactor bed the limestone is fed to a tumbler where the formation of Gypsum is removed from the limestone surface. The limestone is then conditioned with water and transported back to the inlet funnel at the top of the reactor.

The lime is added to the process as pebbles with an initial diameter less than 30 mm and is in this form easily available and inexpensive. Due to the controlled and efficient naturalisation process and the re-circulation of limestone, over 90% utilisation of the limestone can be achieved.

Low system-operating costs

As already explained the cost of the absorbent will be very low. Also the pressure drop over the bed normally can be kept as low as 500 - 1000 Pa, such that the system losses will be low when compared with conventional systems. This provides additional economies.

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