Combustion

There are two practicable ways of oxidizing or burnout systems. On the one hand there are purely oxidation and on the other hand catalytic units. On the oxidation side there are again two processes: thermal and thermal regenerative processes. At the beginning of developing thermal regenerative systems these were meant to be implemented whenever volume flows were high and concentration levels low. This principle, however, has long been abandoned and there is hardly any application today where the thermal regenerative alternative does not predominate over the purely thermal one. The advantage of regenerative processes as compared to the recuperative ones is that the unit can reach auto-thermal operating level with low loads - depending on pollutant concentration (no primary energy needed to keep combustion temperature level) - and at the same time the surplus of energy for higher concentration levels can be separated to be used for other heating purposes. Catalytic processes are used where (depending on the process) no catalytic converter toxics have to be taken into account now and for future developments. A clear advantage is that the process of oxidizing pollutants on a catalytic converter takes place at low temperatures. This significantly influences the size of these kinds of units.

Concentration

Concentration is used for high levels of exhaust gas with low concentration of pollutants. In combination with an oxidizing unit this system can be an alternative to pure oxidization. Its principle is rather simple: the pollutants in the flow settle down on a porous material/agent (absorption) and are carried off by means of a low-level hot air flow (desorption). As a consequence, this low-level flow of desorption bears a higher pollutant concentration, which means that on the one hand the oxidizing unit can consist of a smaller unit and on the other hand the probability to achieve the auto-thermal condition of combustion via this higher concentration is increased.

Denitrification

In general, there are two procedures available which can be implemented depending on flue gas conditions. Non-selective catalytic reduction processes are based on the injection of a reactive agent without using an activating catalytic converter. Selective catalytic reduction principles may on the one hand use the same reactive agent as mentioned before but here a catalytic converter to actively reduce NO and NO2 is needed. Limitations of both systems are quite obvious as they are limited by the reduction rate and in addition to that SNCR cannot achieve the same high-level separation rates as SCR.

Dust filter PF

In many industries dust levels can have various different consistencies and temperature levels, depending on production or unit processes. Dusts with a high-level humidity content have to be treated differently than those with high temperatures and high-level concentration. Applications for certain industries may be more or less characterized by similar preconditions but even there deviations from general conditions can be enormous.