Success for the new multi-fuel kiln burner

October 7, 2016 Carsten Damslund Jensen

FLSmidth’s new JETFLEX® burner has helped improve plant operation and alternative fuels usage at the Rohoznik Cement Plant.

At CRH’s Rohoznik Cement Plant in Slovakia, the JETFLEX kiln burner has now been in operation on the plant’s 3500 tpd clinker line since early February 2016. The many features built into the burner for optimising reliability, availability and fuel substitution have been tested with solid and convincing results. This has contributed to meeting Rohoznik’s goal of high alternative fuels substitution, and improved clinker quality and energy efficiency.

The project at Rohoznik was managed by Mads Nielsen from FLSmidth R&D and Przemek Bochen, Production Manager at Rohoznik. Thanks to good collaboration between them and their teams, the project has been highly successful.

Baseline tests
Before installation of the JETFLEX burner, a series of baseline tests were performed on Rohoznik’s existing multichannel burner in order to obtain performance data. The tests were conducted using a special high-temperature camera that provided video footage helping to understand flame and fuel behaviour inside the flame.

Figure 1. Flame footage of Rohoznik’s old burner (1 and 2) and the JETFLEX® burner (3). Footage 1 and 3 is shown in the visual spectrum. And no. 2 in the infrared spectrum. Cold, unignited fuel appears black. All footage is taken with the petcoke temporarily shut off to get a better view of the SRF

Figure 1 shows the footage in the visual (#1) and infrared (#2) spectra, where the cold alternative fuel appears black. The solid alternative fuel was poorly suspended and dropped out of the flame into the charge.

A fast start
The JETFLEX burner was started up on 8 February 2016 after being installed during the plant’s winter shutdown. Re-using many of the plant’s existing burner parts, the JETFLEX prototype installed at Rohoznik is designed for 100 percent coal/petcoke and natural gas firing, though natural gas is mainly used for heating up.

The burner can operate with a high percentage of waste fuels – up to 100 percent depending on fuel quality. According to the plant operators, it proved easy to start and gave them excellent flame control from the very beginning. Changes to burner settings were observed immediately, and the operators could transition smoothly from gas to petcoke and then to alternative fuels firing.

Focus on alternative fuels
The Rohoznik plant has an excellent track record in its use of alternative fuels, such as Solid Recovered Fuel (SRF). Consequently, alternative fuel substitution is a key performance parameter, in addition to capacity, clinker quality and energy efficiency. The operators and the project team spent the first months of operation testing and optimising the burner and kiln performance, improving the overall performance.

Improvements in burner performance are shown in Figure 1 (#3), which shows how well the JETFLEX burner can mix and suspend the fuel in the flame centre with a strongly reduced tendency for the fuel to drop into the kiln charge.

Figure 2. Alternative fuels substitution and clinker quality

Figure 2 indicates the JETFLEX burner fuel flows, the petcoke substitution (measured as energy share), and the clinker Alite  (C3S) content over a 24-hour period. A substitution of approximately 80 percent was achieved with a 14-20 MJ/kg SRF (Solid Recovered Fuel) at 10-24 percent moisture, while maintaining good clinker strength. At 20 and 22 hours, the SRF dosing unit experienced a blocking tendency forcing a reduced SRF flow from approximately 12 tph to 8.5 tph.

The average kiln inlet NOx emission was recorded well below 700 mg/Nm3 @ 10% O2 during the same period.

Inspection after first run
The JETFLEX burner was in operation for 106 days without any issues. The plant was then shut down according to plan for two days which was ample time for a thorough inspection of the burner. The front of the burner appeared in excellent condition and the adjustable air nozzles were in good condition and could easily be adjusted. Following the inspection, the burner was put back into operation.

A bright future
Production Manager Przemek Bochen at Rohoznik says: “We faced an increasing need to bring alternative fuels into our production, and we saw a good opportunity to do this with a new burner. We have been pleased with the performance of the JETFLEX burner.”

The JETFLEX burner is now available for use with any kiln fuel.

See the animated movie of the JETFLEX® burner here >

Mads Nielsen

Carsten Damslund Jensen

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