INTRODUCTION TO SUBCOAL, THE RECENT SUBCOAL TRIALS AND THE FUTURE Neville Roberts - Managing director N+P Alternative Fuels Ltd Dr. Iakovos Skourides Production Process Manager Vassiliko Cement February 2018
WHAT IS SUBCOAL? An N+P patented waste derived pelletised fuel. High CV, low moisture, high bulk density. Subcoal is odourless, dust free and hydrophobic. Subcoal can be co-milled on a vertical Loesche fuel mill and now it is felt it can be milled on a conventional horizontal mill. Alternatively Subcoal can be milled using a dedicated mill to achieve very high substitution rates (up to 99%) Subcoal is also fed direct into the pre calciner or riser duct in a similar way to tyre chips Used in various forms at different applications, including cement, lime, power and steel industries
LABORATORY WORK WITH LOESCHE In December 2015 laboratory trials carried out at the Loesche Dusseldorf R&D plant. Managed to co-mill coal and Subcoal easily up to a mixture of 30% Subcoal. Loesche predicted that we could easily achieve 50% substitution and that even 100% is achievable. The finished Subcoal product was 99% less than 5mm. Clearly this would burn very well on a cement kiln especially when considering a volatiles in excess of 60%. By this time we had sold out the Dutch production plant but we were still looking for a good client to carry out full commercial trials.
THE SEARCH FOR A COMMERCIAL PARTNER TO BURN CO-MILLED SUBCOAL WAS OVER Together with Loesche we searched for an appropriate partner. Eventually we decided upon the partly owned Heidelberg plant at Vassiliko in Cyprus. The factory has a history of being innovative and had burnt up to 45% alternative fuels. N+P carried out a technical audit of the plant and concluded that following some improvements the plant would be a suitable site to carry out trials. The plans were therefore agreed upon to undertake the trials in the first half of 2017 depending upon clinker stocks.
Industrial trials of Subcoal co-grinding and utilization in a 6000 tpd precalciner kiln Dr. Iakovos Skourides February 2018
Presentation outline Brief description of VCW history and clinker production line. Major challenges of co-grinding petcoke with Subcoal - results of preliminary trials. Grinding results after process and mechanical modifications. Results from 1 week trial in the kiln- impact on pyro process and clinker quality 6
Vassiliko Cement Works at a Glance Established in 1963 First production in 1967 2 nd Lepol Kiln line in 1969 3 rd Lepol Kiln line in 1975 4 th Lepol Kiln line in 1985 New BAD 2-string 5 stage Pre-Calciner Kiln 2011 Cement Plant Location : Vassiliko, Cyprus Raw materials : Main quarry 7 km from plant Kiln capacity : 2 m tpa clinker Grinding capacity : 2,4 m tpa cement Other infrastructure : Vassiliko port 7
Milestones since year 2000 Loesche vertical cement mill installation 60 tph 90k tons Clinker Silo Loesche vertical cement mill installation 200 tph New clinker production line Dedicated system for feeding alternative fuels New cement silo 25,000 tns. Debailing system for RDF 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 8
Clinker production Line at Vassiliko Cement Works Ltd Commenced operation on 2011 Raw Mill (LM 60.4)- capacity 520 t/h Rotary kiln- 2 string 5 stage precalciner kiln- capacity 6000 t/day Coal Mill (L.M 30.3) In 2017 thermal substitution with alternative fuels was higher than 30 %. Main fuels RDF/SRF, chopped tyres, sewage sludge, MBM Substitution rates with AF up to 50 % have been tested successfully. However, substitution with AF is maintained at lower level to ensure optimum clinker quality.
Coal mill- off gasses to thermal oxidation during subcoal grinding
Co grinding Subcoal in a Loesche Mill (LM 30.3)- Major challenges during first trials Petcoke requires fine grinding- fine grinding of Subcoal is not feasible since it is a fibrous material. Ignition point of Subcoal is considerably lower compared to petcoke (due to high volatiles content)- risk of fire. Mill capacity reduced significantly during the initial grinding tests. The residue of the final product was very high (R90 >20 %) with 8-10% Subcoal grinding. Two weeks of trials grinding only calciner fuel since the final product was not suitable for the main burner.
Co grinding Subcoal in a Loesche Mill (LM 30.3) after process modifications Dual control loop for mill inlet temperature and mill outlet temperature minimized risk of fire. Adjustment of piston accumulators to enable grinding with lower counter pressure-higher grinding force. Tuning of PXP expert system for sub-coal operation (efficient ΔP control of the mill) Efficient ΔP control improved mill productivity and fineness of the final product Mill operation with increased speed on the main drive Increased speed normally results in high vibrations, subcoal reduces vibration levels enabling operation with higher grinding force and main drive speed. Grinding 10-15% in the main burner for 1 week Grinding 15-20% on the calciner for 1 week
Co grinding subcoal in a Loesche Mill (LM 30.3) Preliminary trials Trials after mechanical and process modifications Preliminary trials Trials after miil and process modifications Preliminary trials Trials after mechanical and process modifications Petcoke (100 %) 30 30 2 2 26 25 Subcoal 5 % 18 25 20 3 30 28 Subcoal 10 % 15 23 24 5 34 30 Subcoal 15 % 12 22 26 8 37 32 Subcoal 20 % Not tested 20 Not tested 10 Not tested 36 * Residue of petcoke above 90 after substracting subcoal % Mill capacity (t/h) R90* (%) kwh/t Table 1. Effect of Subcoal on coal mill performance
Effect of sub-coal on pyro-process- results from 1 week trial at VCW 6000 tpd kiln Subcoal was utilized in the calciner during the first two weeks of trials. Other alternative fuels were fed to the calciner through a dedicated feeding system (see table 2). In the last week of trials subcoal was utilized both on the main burner and the calciner. No negative impact was observed on kiln capacity or on clinker quality (according to XRD analysis and clinker microscopy- results are summarized on table 2 and table 3)
Effect of Subcoal on pyro-process- results from 1 week trial at VCW 6000 tpd kiln % Thermal substitution calciner % Thermal substitution main burner % Thermal substitution with subcoal Total % Thermal substitution with AF total Average C3S content in clinker Average free lime (fcao) % Subcoal Calciner * % Main burner Kiln daily capacity (tpd) 0 0 0 0 0 35 68.5 0.8 6100 10 2.5 5 3 3.8 38 69 0.7 6050 15 3.8 10 7.24 5.2 42 68.5 0.6 6080 * % compared to petcoke fed on calciner Table 2. Effect of Subcoal on the pyro process and clinker quality
Sample Name Very short=5-10μm Very slow=amber *Clinker with 0 % subcoal 19.59 0.0083 25.19 Clear-Faint Yellow Clinker with 3.8 % subcoal 21.27 0.0089 23.88 Clear-Faint Yellow Clinke with 5.2 % subcoal 22.13 0.0106 25.25 Clear-Faint Yellow Typical Quality of CLOP 19.92 0.0082 24.64 Clear-Faint Yellow * % subcoal is % thermal substitution Alite Size - Heating Rate Fast=15-20μm Moderate=20-30μm Slow=30-40μm Very slow=40-60μm Alite Birefringence - Max Temperature High=0.01-0.008 Good=0.007-0.006 Average=0.006-0.005 Low=0.005-0.002 Belite Size - Burning time Overburning>40μm Long=25-40μm Medium=20-25μm Short=15-20μm Belite Colour - Cooling rate Fast=Clear Moderate=Faint Yellow Slow=Yellow Table 3. Effect of Subcoal on clinker microscopy
NEW TRIALS USING A HORIZONTALL BALL MILL Initial trials have now taken place in milling Subcoal on a conventional horizontal ball mill in Greece. Achieved milling 10-15%. Inlet temperature of 380 0 C but no indication of CO in the milling system. No evidence of fouling or blockages in the milling system. Bottleneck was related to separator operation. This now needs further optimization work. Now preparing for the second trial.
NEW SUBCOAL FLUFF QUALITY N+P have successfully produced 6mm diameter pellets Very low moisture levels <3% Developed for usage in the steel industry Very short pellets have proven to be very useful as a cement kiln main burner fuel Up to 75% substitution was realized at a kiln in Europe Loose transport using sea containers, no debaling is required Density typically 250-300 kg/m³
SUBCOAL USAGE IN THE STEEL INDUSTRY N+P have been trialing the use of Subcoal pellets at an Austrian steel plant blast furnace for some 12 months. Supply by train is being developed throughout Europe The utilization of Subcoal in blast furnaces is being followed by various universities in Europe We are also in discussion with various other steel producers in the world Patents are now pending for this application. So far the use of Subcoal on steel blast furnaces has been very successful with potential high volumes
SUBCOAL USAGE AT POWER STATIONS Subcoal has been used on coal fired power stations in the Netherlands and Germany but only at low levels of substitution. A major investor into the coal fired power industry sector is now looking to convert coal fired power stations to biomass with Subcoal being the sole fuel. This will be another major development for Subcoal with potential volumes of well over 1 million tonnes per year
NEW SUBCOAL PRODUCTION FACILITY: Subcoal Production TSP Ltd Currently N+P have one production facility in the north of Holland. The plant is running at maximum production and is now fully sold out. N+P are therefore building the second production facility in North East England at Teesside. The plant will supply domestic need and can be used for exporting purposes. The plant will produce circa 180kt/yr of Subcoal pellets and high quality SRF (all over 20 GJ/ton). Commissioning will be completed in Q4 of 2018. It is believed that this will be the first of many Subcoal plants that will be built in the UK and elsewhere.
CONCLUSIONS The development of the various applications of Subcoal are moving at some pace. Trial at Vassiliko was well prepared, and after some modifications the results were very positive The cement applications are well developed and the steel and coal fired power station applications are progressing with great speed. These developments further underline the view that N+P is now an energy supply company and not just a waste management company. In addition, as can be seen from the presentation, N+P are also advising consumers on the use of their fuel and so providing more added value to their offering.