- Surface Treatment Technology
- Wire Plating Technology
- Recycling Technology
- Flue Gas Purification
Catalyst System for HF/NOx / Combined HF/NOx Abatement Systems
We are one of the world’s leading suppliers of combined NOx/HF abatement systems for the stainless steel industry; worldwide there are over 20 of our reduction plants in operation right now.
The exhaust air containing NOx and HF is generated during the treatment of stainless steel surfaces
by using a mixed acid solution (composed of hydrofluoric acid and nitric acid) in order to remove the
scale and any impurities such as grease / lubricants from steel surface. Before being discharged into
the atmosphere this exhaust air has to be sucked off from the pickling process and purified in the ex- haust air treatment system.
At first the acidic droplets contained in the exhaust air are removed via a demister. Then the cold raw
gas is heated in counter flow to the hot pure gas by a heat exchanger. In order to avoid incrustations
and to eliminate the risk of corrosion the raw gas is preheated to over 70°C before entering the heat exchanger. After passing heat exchanger the raw gas is supplied to HF dry sorption system. This HF reactor is equipped with several layers of honeycomb lime modules featuring a low pressure loss. The
Ca(OH)2 modules react with the hydrofluoric acid contained in the exhaust air and calcium fluoride
(CaF2) is produced as end product.
The partly purified exhaust air is heated to the operating temperature required for the SCR process by means of a burner. Directly after burner a 40% aqueous urea solution (or 25% ammonia solution) is injected into exhaust air flow via nozzles. To achieve a finest spraying compressed air
is mixed. Thus a homogenous distribution of the reducing agent in the exhaust air is ensured. The exhaust air mixed with the reducing agent is supplied to the downstream SCR reactor filled with the SCR catalyst modules where NOx and the injected ammonia react on the catalyst surface reducing the NOx to harmless nitrogen and water.
These generated reaction products can be discharged into the atmosphere via stack.
NOx sampling and monitoring system:
After passing the SCR catalyst an exhaust air sample is taken and supplied to a NOx analyzer which determines the residual content of NOx. The fully automated process uses the analyzer output to adjust the rate of ammonia/urea injected into exhaust air flow to an optimum level. Hence
it is guaranteed that our plants meet the requirements of the regulatory authority at any time.
The main benefits are:
— High degrees of decomposition
— The produced reaction products (water and nitrogen) are natural constituents of the atmosphere and therefore they are harmless to the
— No waste material, because the SCR-catalysts are recyclable
— PIC-controlled; simple and user-friendly user interface because of a SCADA (Supervisory Control and Data Acquisition) system
— In order to reduce the NOx emission values even further our plants can be easily retrofitted and upgraded