2013 saw Scheuch bring the new SCR process for NOx separation – known as a semi-dust raw gas circuit – to life at Lafarge Perlmooser GmbH in Mannersdorf, Austria. The plant represents the world's first industrial-scale application of its kind to be used in the cement industry, and is designed for an NOx limit value of 200 mg/Nm³.
The furnace exhaust gas undergoes an initial dedusting process in a high-temperature dry electrostatic precipitator and then passes through the two-layer catalytic converter. An integrated gas conditioning tower below the catalytic converter for exhaust gas cooling ensures that the filter inlet temperature required during direct operation can be reached. The dust that is separated in the dry electrostatic precipitator is conveyed back to the exhaust gas flow by means of a pneumatic dust conveyor pump.
The catalytic converter was observed at regular intervals in order to check the effectiveness of the cleaning system and to ensure that the start-up and shut-down procedure was operating correctly. After the positive results in this phase, it was possible to carry out the planned performance test over a period of two weeks. The purpose of this was to check that the contractually specified parameters were being adhered to. The test revealed that the plant was continually demonstrating compliance with the specified value of 200 mg/Nm³ for NOx separation – and, where operational costs were concerned, was even undercutting values relating to energy and urea consumption.There are plant and process-specific parameters that can bring about dust properties that are difficult to deal with (such as very high dust resistance) and diminish the pre-separation performance by the electrostatic precipitator. As a consequence, the dust load for the catalytic converter elements increases and cleaning becomes less effective. The availability of the plant is not yet at a satisfactory level, which means that additional steps must be taken to optimise this; currently, the first stages in developing a solution are being worked out.
Thanks to the good degree of separation of the SCR plant (fine denitrification) – which alone is able to achieve the requisite clean gas value – the existing SNCR plant for preliminary denitrification is no longer necessary. This has resulted in yet more operational cost savings at a sizeable level. Initial catalytic converter analyses indicate a relatively low activity loss, although it will only be possible to be more specific on this subject once the plant has been operating for extended periods. Furthermore, a positive side-effect of this semi-dust circuit is that any organic compounds which may be present are broken down at the same time.