Preconditions:
An incineration plant followed by exhaust gas cleaning is used for the disposal of residues from various chemical production plants. Different harmful impurities exist in the exhaust gas owing to the wide range of materials used for the combustion, with some of them occurring in very high concentration. In particular, the emission of halogens and their compounds as well as dust and very fine aerosol particles are expected. The purification values of the gas that are to be achieved must satisfy the requirements according to 
17. BImSchV (German law). The plant must provide an availability and uptime of more 
than 99 %.

Concept:
The exhaust gas leaves the combustion chamber at a temperature of 1000-1100 °C and is then cooled in a quench that is flanged to the combustion chamber. The exhaust gas, which is then cooled to almost the saturation temperature, enters a two-stage packed tower from below, in which it is cleaned - especially of the gaseous impurities - in a counter-flow of washing fluid. Quenching and the first stage in the tower packing piling have a common water circuit, which is supplied from the sump of the packed tower and run at a pH-value of 0. The second tower packing stage is operated by adding caustic soda with a washing fluid in a slightly alkali pH-value range. At the top of the packed tower, a droplet separator prevents discharging of liquid. For separating the residual dust and the fine aerosol particles, a two-stage condensation-agglomeration process is used. The gas is locally over-saturated in co-current flow through two-component jets. The over-saturation is degraded by heterogeneous condensation at the dust and aerosol particles, which grow as a result. In an inverse-flow agglomeration track, the enlarged particles are separated in a sort of drop separator. An intake draught pushes the cleaned exhaust gas to the chimney.

Technology:
The process and plant technology distinguishes itself because of the following points:

• The hot gas quench is made of graphite and in the transition zone "hot/cold", has a protective jacket of high-quality steel. The addition of liquid takes place in multiple stages via nozzles, which form both a protective film on the walls of the equipment as well as a fine body of spray in the middle of the equipment. As a result, the gas is almost instantaneously cooled to saturation temperature, the equipment is protected from the attack of corrosive materials and the formation of hot gas streaks is avoided.

• The packed tower is fitted with modern high-performance tower packings, which are extremely resistant to dirt, have a very low pressure loss and nonetheless have a high separating capacity.

• Optimum separation with minimum operating materials consumption can be achieved by regulating the pH-value.

• The condensation agglomeration process described is a particularly cost-effective method, in terms of pressure loss, to separate even the finest aerosol particles effectively. The investment costs are at least one order of magnitude below those for a wet electric filter, which would come into question here as an alternative.

• The waste water generated in the condensation agglomeration stage is fed to the quench and evaporated there. This optimizes the generation of waste water in the plant.

Result:
The plant concept presented above facilitates, for the residue incineration described, adherence to the limiting value according to 17. BImSchV (German law) even under extremely widely varying entry conditions of the impurities. The plant is of very compact construction and because of the choice of equipment, involves a comparatively low investment cost. Owing to the low loss of operating pressure, the condensation-agglomeration process is very affordable even in terms of running costs.
A very high availability can be guaranteed by redundant design of the components that are susceptible to faults.