The selective catalytic reduction of nitric oxide in the bead string reactor

For many gas/solid reactors pressure drop is a cost-determining factor. A striking example is flue gas treatment, with a financially tolerable pressure drop of only 10 - 20 mbar. This has led to the development of structured catalytic reactors like the Monolithic Reactor, the Parallel Passage Reactor and the Lateral Flow Reactor and more recently the Bead String Reactor. In the Bead String Reactor the catalyst is fixed on strings parallel to the flow. This new arrangement results not only in a low pressure drop but also a dustproof operation, an adjustable voidage (10% - 100%) and lateral mixing. This paper presents the results of the selective catalytic reduction of nitric oxide with ammonia in the Bead String Reactor on a V/Ti/Si catalyst. The primary purpose of the experiments was the validation of mathematical models for the design of this novel reactor type for a potential industrial application. A comparison of the experimental results and the mathematical models is given for different arrangements of the strings. The experiments have shown that this flexible reactor configuration performs indeed well and that the present models predict both the pressure drop and the conversion of nitric oxide accurately. Though the Bead String Reactor might not be able to compete with monolithic reactors for exhaust gas treatment from vehicles, it is on the threshold of industrial application in power plants for flue gas treatment.