The catalyst AOK-78-55 for selective reduction of NOx has successfully passed pilot testing on operation under conditions of nitric acid production AK-72 unit

The catalyst AOK-78-55 for selective reduction of NOx has successfully passed pilot testing on operation under conditions of nitric acid production AK-72 unit

Specialists of Katalizator JSC performed pilot testing of catalyst for selective reduction of NOx with ammonia under high temperatures. The test results confirmed laboratory research and hereby open the opportunity for customers of Katalizator JSC to use this catalyst under working conditions of AK-72M unit, and to decrease their operation costs consequently.

In industrial units for production of non-concentrated hydrogen nitrate after the absorption of nitrogen oxides by water the preheated waste gas enters the catalytic purification reactor. There with the help of catalyst the selective reduction of nitrogen oxides takes place until the generation of harmless products: nitrogen and water. Traditional catalysts for this process can be nominally divided into three groups: high-temperature – palladium containing catalysts, medium-temperature – copper-zinc containing catalysts, and low-temperature – aluminum-vanadium catalysts. The choice of catalyst is based on the technology and consequently working temperature range. Large-scale nitric acid production AK-72 units use expensive catalyst containing precious metal – palladium. It requires high operating temperature, which accordingly affects the operating costs. By the way some АК-72 units have been updated into AK-72M. Modernization took place also for catalytic purification reactors, where copper-zinc catalysts were used under medium temperatures.

Specialists of Katalizator JSC analyzed performance figures and operating conditions of catalyst, performed laboratory research of catalyst’s physical and chemical characteristics and estimated possibility of applying aluminum-vanadium catalysts under AK-72M units’ operating conditions.

The result of this research work confirmed the possibility of applying catalyst AOK-78-55 with high strength retention under high temperatures and loading with the following destruction efficiency:

• 99.36 % under 350оС;
• 99,86 % under 360 оС.

Based on the data from laboratory research of catalyst AOK-78-55 pilot testing under industrial conditions took place.

The aim of this testing was to measure exhaust gas purification efficiency and to estimate industrial applicability the possibility of applying this catalyst for industrial operation in AK-72M units. According to the results of pilot testing in industrial reactor NOx removal efficiency achieved 99.3 %. This result displays excellent effectiveness while maintaining standards of process parameters.

The important criterion for industrial applications of aluminum-vanadium catalysts is minimization of so called “vanadic corrosion” which is possible to appear with the presence of vanadium oxide in gas composition after reactor. According to our data, entrainment of vanadium oxide from catalyst was associated with using of aluminum vanadium catalysts with inadequate actual abrasive resistance, the index of which is shown by some manufacturers as 22.7%. These catalysts lost their strength and were damaged during operation.

However, a totally different technology is used for catalyst AOK-78-55 production to ensure extremely high strength and thermal resistance during industrial operation. During the process of AOK-78-55 catalyst development, the specialists of Katalizator JSC initially put emphasis on high strength and thermal stability while maintaining high catalytic activity. It eliminates entrainment of catalyst fines and risk of vanadic corrosion. Many years’ experience of applying catalyst AOK-75-88 in many industrial units UKL-7confirms high consumer appeal of our product.

At the present moment the Department of Chemical Engineering, Katalizator JSC is ready on a timely basis to provide assistance to nitrogen industry enterprises in switching to the catalyst AOK-78-55 for selective reduction of nitrogen oxides, including all necessary investigations and calculations, and engineering support for catalyst operation.