NOx-separation        back to index         to range of washers 

    Products – Washer programme
  NOx separation from waste air   
   Method of recovery of raw materials from waste gas without any origin of waste
1. Process description
2. Purification processes
3. DGE- recovery process
5. Literature
4. Example of the use:
For pickling bath with a volume of 24 m³a closed process control has been implemented. The flow-rate of air drawn off by a fan is reduced with a measuring orifice plate. The drawn off air flow-rate can by adjusted continuously to a value of about 500 m³/h without any occurrence of negative effects to the pickling process. A NOx - loading is of about 1 000 – 5 000 ppm, in peak conditions 10 000 ppm at a NO/NO2- ratio of 1:10 . In this way the following raw gas doses are given :
NO 909 ppm 1.217 mg/m³ 608,5 g/h 20,28 mol/h
NO2 9090 ppm 18.659 mg/m³ 9.329,5 g/h 202,8 mol/h
Total 10999 ppm 19.876 mg/m³ 9.938,0 g/h 223,08 mol/h
4.1 Conventional NOx separation

The drawn off air with NOx content which has to be purified is fed in five washers installed in series, with a diameter of 950 mm, filled with small solid bodies with a height of the filling bed of 5 600 mm. The washing circuit is in operation with the use of 20% caustic soda lye. In accordance with the process described under paragraph 2.1 – Alkaline washers the following reductions in NOx content take place in single columns:

NOx- inlet NOx-outlet
mg/m³ mg/m³
Column 1 19.876 10.733
Column 2 10.733 5.425
Column 3 5.425 2.410
Column 4 2.410 1.150
Column 5 1.150 480

Alternatively, it is possible to use also a smaller number of columns; in that case, however, it is necessary to use columns of a larger diameter.

As a waste product it results an amount of 218.3 kg/d of NaNO2and 187.7 kg/d of NaNO3 respectively, i.e. in total of 406 kg/d of salts which shall be liquidated. For the process control from the practical point of view the concentration in the washing circuit shall not be chosen as a too high because it could result in crystallization and clogging. If we start from a maximum salt amount of 10% the flow-rate of waste water which has to be liquidated is 4 mł/d. Necessary caustic soda lye consumption is about 860 l/d for 25% solution. A reaction heat which should be dissipated is of 7.5 kW.

The following operating costs result from it :

Electric power for fans and pumps 420    kW/d 100,8    DM/d
Caustic soda lye 860    l/d 146,2    DM/d
Service water 3,2    m³/d 9,2    DM/d
Cooling water 16    m³/d 4    DM/d
Waste water liquidation


m³/d 4.000    DM/d
In total 4.260,2    DM/d
The specified legal values of the purified gas 500 mg/m³ have been maintained.
4.2  DGE processes :                

4.2.1 L-NOx-Process         4.2.2 G-NOx-Process         4.2.3 DGE - instrumentation

NOx-separation        back to index         to range of washers