12th Global CemFuels Conference 2018
20 - 21 February 2018
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The Global CemFuels Conference has successfully taken place in Berlin, with 160 attendees from 30 countries, 31 exhibitors and 20 presentations. The conference covered all aspects of alternative fuel use in the cement and lime sectors. The 13th Global CemFuels Conference will take place in February 2019 in Amsterdam, Netherlands.
Frank Brannvoll of Cembureau kicked-off the conference with a panoptic overview of the global fuels markets. In the EU28, the thermal substitution rate (TSR) is 43% on average, with around 11Mt of alternative fuels (AF) used each year. Frank pointed out that many countries are below average, with a small number of large countries (Germany, France, UK) at above average TSR and with many countries, notably Ireland and Italy, with huge potential for increased AF use. Frank pointed out that when the US dollar is weak, then fossil fuel energy costs are generally lower in non-dollar local currency terms. This means that the strength of the dollar has a big effect on the choice of fuels used worldwide in the cement industry, particularly with regard to the fossil fuel/AF mix. He suggested that OPEC has decided that US$60-70/barrel is a level that they can ‘live with,’ which is just as well, since as the oil price rises above this level, the Americans can bring more shale gas rigs on line to take advantage of the higher prices, naturally capping global energy prices. Frank Brannvoll also pointed out that Chinese coal consumption dwarfs all other coal markets on the planet, but that the Chinese authorities have been trying to exert greater control over the industry and over pricing: mines have been closed or are now more highly regulated, while there has also been a clampdown on coal price speculation, in order to bring coal prices into a preferred price range. However, coal is trading at above the preferred range and the authorities have now stipulated a maximum price (of RMB750/t, US$118/t). Globally, petcoke prices are strongly correlated with coal prices, but at a discount (otherwise industrial users would just use coal). India has partially banned the use of petcoke, on environmental grounds. There is normally a US$10/t spread between 4.5% sulphur and 6.5% sulphur petcoke. “Higher prices for petcoke mean shorter payback periods for AF projects,” concluded Frank Brannvoll.
The next speaker was Andy Hill of SUEZ Recycling and Recovery UK Ltd, who started off by saying that Brexit will not have a major effect at its start date in March 2019, but that uncertainty is a crucial factor, particularly over the future trading situation and the imposition of tariffs at borders. Andy pointed out that RDF is a lower calorific value fuel, whereas SRF is more highly processed and has higher calorific value. Andy pointed out that environmental taxes have been implemented around the world, but that there is a long way to go to complete coverage. The EU ETS has not been a success so far, with the CO2 price languishing at under Euro10/t for years. However, the EU ETS Phase 4 is forecast to raise the level to beyond Euro20/t (at which point European cement becomes uncompetitive) to as high as Euro40/t. The Chinese, for environmental reasons, are closing coal, cement and steel plants and are banning the import of many categories of recyclables. This has created massive bottlenecks in European recycling flows. Alternative markets (Turkey, Malaysia, Vietnam) have also pushed up prices and quality standards: “It’s a buyers market.” Andy suggested that this might signal the ‘death’ of co-mingled municipal waste collections, in order to force up the quality of waste and recycling streams. In the meantime, there will be a greater volume of RDF and SRF, with price implications for buyers. In the medium term, there is likely to be a marked change in consumer behaviour which will drive recycling flows.
André Van Steenberge next spoke on behalf of HeidelbergCement and pointed out that the company has a target TSR of 30% worldwide. This target has already been met in Europe, but is at only 10% in North America, only 7% in Africa/Eastern Mediterranean and only 3% Asia-Pacific. New management initiatives have been put in place worldwide in order to push AF use, including a dedicated board member. André pointed out that although some AFs are common around the world, others are more local, such as rice husks, so that development of local markets for AF streams will be critical. André pointed out that Italcementi was more advanced in some areas when HeidelbergCement took it over and the combined group has learned from the purchased company in order to roll out best practice. For every waste stream that the company is contracted for, there is always a Plan B,’ and sometimes plans C, D and E, for alternative destinations and users for each material if the first plant cannot accept the material. André suggested that the Chinese ban on impure recycling fractions will lead to a greater requirement for better sorting and that this sorting process might happen in Asia, rather than in the higher-cost EU. Again, less intensive use of plastics is the likely final outcome.
Ed Verhamme of Alternate Resource Partners next gave a global overview of AF trends. He suggested that AF has the potential of abating 750Mt of CO2 per year by 2050 if current trends continue. If all EU countries had a 60% TSR, 26Mt of CO2 emissions would be avoided each year, 15.Mt of waste would be processed, 11.1Mt of coal use would be avoided and Euro12bn of investment in Waste to Energy plants could also be avoided. Ed suggested that global coal production peaked in 2013-2014 and has been steadily declining since then, but that there is still strong underlying demand, for instance from India. A ban on landfilling, or at least strenuously applied and punitive landfill taxes, will strongly encourage both recycling and the development of a supply of waste-based AF. Southeast Asia and Central America are among those areas with the greatest potential for increase in use of AF. In the longer term, Africa is almost totally undeveloped.
Hansjörg Diller next spoke for MVW Lechtenberg, on how to improve quality of alternative fuels. “Quality management always starts at the source,” suggested Hansjörg. At the RDF plant, the incoming waste must be fully characterised. Different categories of waste must be stored separately and any foreign objects must be pre-sorted and removed. Sampling and continuous analysis of waste and product characteristics must be performed and action taken on the results. Materials that are considered to reduce RDF quality should be excluded from AF production, including chlorine-containing and heavy metals-containing materials, as well as those materials with high moisture content and low calorific value. Specific and systematic methods have been stipulated to try to ensure reproducible and representative sampling methods, but with such inhomogeneous materials, this can be difficult. The RDF producer should make a declaration of the composition of the RDF at regular intervals, perhaps after every 1000 or 4000t produced, including stating the measured limits on minor metals, sulphur, chlorine, moisture content and CV of the AF. In such a case, the recipient of the fuel can accept or reject the shipment of AF.
In the next conference session, on case studies in AF, the first speaker was Matthias Mersmann of aixergee Process Optimisation, speaking on the successful optimisation of a secondary-fuel-fired calciner. The calciner in question had fall-out of material in the TAD ‘knee,’ coatings and blockages in the bottom stage cyclones and frequent CO peaks. The plant wanted to safely combust up to 100% of AF in the calciner and at the same time to increase production by 200t/day, while fitting into the same space and reusing the existing ID fans. Trial-and-error can be used to determine the correct engineering approach, but the smarter method is to use a model-based approach, using a virtual model of the process. Matthias pointed out that the complete characterisation of the RDF is critical, in terms of particle shape, density, calorific value and burn-out behaviour, in order to be able to correctly model the process. Matthias showed that a ‘pumping’ or periodic purging of material from the calciner in this case was unavoidable due to the calciner’s design, leading to localised reducing conditions and breakthrough of CO-rich gas into the preheater, as well as a carry-over of unburned fuel into the cyclones which led to coating problems. A redesign of the calciner was simulated and perhaps unsurprisingly the most expensive suggested option was found to be the most effective solution, involving slimming the calciner and the introduction of a longer goose-neck. During a six-week kiln stop the designed solution was enacted and as a result, all process aims were met.
Michail Akritopoulos of Cinar Ltd next spoke on calciner upgrades to burn 100% AF and petcoke. Michail pointed out some of the unavoidable side effects of the use of AF, including an increased heat consumption and to a certain extent, a reduction in production rates. He pointed out that there is a limited potential for thermal substitution on the main burner, of around 40%, whereas on the calciner burner the TSR can be up to 100%: larger particle sizes can also be used in the calciner due to the longer residence times. Due to the wide variety of configurations of precalciners, calciners, preheaters, goose-necks, TADs, burners and other process parameters, each case must be scrutinised separately and a custom-solution applied and Michail gave a number of examples of successful calciner upgrades. He gave some details of the Polysius Step Combustor, as well as the FLSmidth Hotdisc, both of which can be used to combust bulky alternative fuels. AFS ‘skewers’ can be used to burn whole tyres, while the ‘compact calciner’ from PMTEchnologies has also successfully been used to improve AF TSR rates.
Taís Mazza of Loesche GmbH next spoke on an integrated approach to maximise the use of AF in cement plants. Countries in the OECD are responsible for 44% of the world’s waste, but the greatest future increase in waste production will be in poorer Asian countries. Taís suggested that a large cement plant can make about 80% of the value produced compared to a Waste-to-Energy plant, but at only 40% of the capex. She suggested that the first 5% TSR is the hardest, since it involves overcoming barriers in the mind, not just of the plant’s neighbours, but also in the operating paradigm of the cement plant’s personnel and cement company management. The progressive technical steps towards great AF use are now well-trodden by plants around the world, including the use of a chlorine bypass, perhaps precalciner modifications, the use of AF conditioning capacity (and here Taís suggested the use of the Rocket Mill) and finally modifications in the main burner. The Rocket Mill consists of fast-rotating horizontal chains in a chamber surrounded by a sizing screen, providing high-surface-area AF, with size reduction in a single step and with a moisture reduction of around 10% at the same time.
Next was a co-authored presentation by Neville Roberts of N+P and by Iakovos Skourides of Vassiliko Cement, on the results of burning SubCoal in a large precalciner kiln. SubCoal is a patented waste-derived pelletised fuel, with high CV, low moisture and high bulk density. The fuel is odourless, dust-free and hydrophobic. Neville presented results showing that SubCoal can be co-milled with coal, even at high levels of substitution. N+P eventually partnered with Vassiliko Cement (part-owned by HeidelbergCement) on Cyprus to try a full-scale trial for SubCoal, on the two-string five-stage precalciner kiln, commissioned in 2011. The cement plant already uses high levels of AF, of up to 50%, including RDF/SRF, chopped tyres, sewage sludge and MBM, although AF use is maintained at a lower rate of around 30% to optimise clinker quality. Thermal oxidation of coal mill off-gases has been used at the plant to control odours, after complaints from neighbours. Iakovos pointed out that SubCoal is milled to fibres, rather than to particulate dust and due to its high volatile content its combustion temperature is substantially lower than coal. He detailed some of the challenges of milling SubCoal that were encountered in the two week trial, but also pointed out that all of the challenges were overcome. The variable speed on the main drive of the coal mill was used to increase the mill speed: this actually decreased the level of vibrations on the mill and allowed a higher grinding force to be applied. During the trials the mill capacity was decreased and the specific power was increased. Alite content of the clinker was not influenced and nor were free lime or kiln capacity affected. The trials achieved an additional TSR of 5% on top of previous AF substitution rates. Neville Roberts pointed out that SubCoal can be used with next-to-no capital expenditure, allowing a cement-producer to try out AF for the first time at low cost.
Next up was Thomas Jennewein of FLS Pfister, who spoke about a case study at National Cement in Dubai, which has a production capacity of 1.5Mt/year, using primarily oil and gas. Increases in fossil fuel prices led to the company’s exploration of the use of ‘alternative’ fuels - originally in 2011 pulverised coal dust, but from 2015 carbon dust (from aluminium production) and tobacco dust (from cigarette production). To be able to dose each of these materials, two of Pfister’s rotor weigh-feeders were installed at the plant, while a 102MW FLS Duoflex burner was also installed. The systems enabled the substitution of 3960t/yr of coal, allowing a return on investment of less than three years. In a second case study at Arabian Cement Company in Egypt, FLS Pfister installed a fully-automatic multi-fuel facility for storage, handling and dosing of AF (dried sewage sludge, MSW, rubber, packing waste etc) for direct firing of the calciner, at a capacity of 10t/hour and a TSR of 30%.
The final presentation of the day was given by Samuel Zühlsdorf of thyssenkrupp Industrial Solutions, on the Prepol Step Combustor. Samuel pointed out that the world population will increase to 8bn by 2025, with 60% urbanisation and 6Mt of waste produced each day. To help the world cope with this diverse waste stream, Polysius developed the Prepol Step Combustor, with a combustion residence time of beyond 1000 seconds. The Combustor is shaped like a descending set of stairs, with combustion air provided from a cooler off-take. Fuel is introduced to the combustion chamber by feeder screws. Combusting fuel is then pushed slowly down the stairs using air cannons. Coarse fuel particles remain on the steps, but fines are entrained into the tertiary airstream, so that only non-‘flyable’ particles remain on the grate. Preheated raw meal passes over the Combustor in the process gas to effect heat exchange. Samuel outline an installation at the Lägerdorf cement plant in Germany, which has been online for more than four years. He stated that the use of municipal wastes is quite challenging, but offers the greatest economic benefit. It is possible to increase or decrease the size and number of steps in the Combustor to customise the degree of combustion: when configured with the least number of steps, the Combustor becomes a fuel pre-preparation, drying and pyrolysis unit, with only around three minutes of residence time. A Prepol SC has been installed at the HeidelbergCement Schelklingen plant in Germany and two other contracts are also underway one in Central America and one in South America.
Global CemFuels Awards Dinner
The Global CemFuels Awards Dinner took place at the Classic Remise Berlin, a classic car centre, with ‘Berlin flavours’ in music, food and drink. The Global CemFuels Awards were presented at the event: CRH was award AF-user of the year and N+P was awarded supplier of the year. Molinari won for technical innovation of the year for its TP series of shredders, while Vassiliko Cement (and N+P) won for AF project of the year. Samuel Zühlsdorf of thyssenkrupp took the prize for project manager of the year and Cembureau was awarded the prize for outstanding contribution to the use of alternative fuels. Con Manias of FCT, Australia, was awarded the Global CemFuels ‘Personality of the year’ award. It was announced that the next Global CemFuels Conference will take place in Amsterdam in February 2019.
Second day
Pietro Cella Mazzariol of Entsorga started the second day of the conference, by suggesting that “the waste drives the technology.” Municipal solid waste varies from country to country and from region to region and the approach to processing it should vary as well. Pietro said Entsorga’s main business is to provide mechanical-biological-treatment (MBT) plants, incorporating a bio-drying stage to reduce moisture content of the organic fractions. His main question was whether SRF can be produced economically through MBT in areas where landfill fees are low or non-existent. He concluded that SRF can be produced at a cost of around Euro1/GJ. It is up to the fuel markets to decide if that cost is acceptable.
Eric Plantié of Precimeca next gave a case-study on tyre-derived fuel preparation, using his company’s tyre shredding equipment. The tyres are actually sheared and no debeading (metal removal) is required: output is generally of chips of 25mm size, with no protruding exposed wire and with uniform size. Eric pointed out that tyres are usually among the first AFs to be used, since scrap tyres are generally ubiquitous, have low seasonality of supply, high bulk density and are not prone to water uptake, so that they can be stored outside. Crucially they have a CV of close to that of coal or petcoke, at 25-30MJ/kg. On average, tyres have a high biomass content, at around 30% and also supply iron to the material mix in the pyroprocess. Eric introduced Konya Cement in Turkey, which in 2013 wanted to start using tyres as an alternative fuel, with a target TSR of 30%. Precimeca provided a pragmatic solution suited to local solutions, which worked well enough that the plant ordered a clone plant in 2017, both operating at 5t/hour of 40mm chips, using three shifts and manual tyre handling, year-round.
How to mitigate the impacts of AF on pyroprocessing was the subject of the next presentation, given by Stéphane Poellaer of Alterline, who first pointed out that you will create a huge mess if you try to use AF on a kiln that is not already operating in a stable state. AF use will involve a higher heat consumption, a higher exhaust gas volume, a higher input of chlorine and changes in kiln operation and kiln behaviour (particularly the ‘speed of response’ of the kiln). AF has a higher moisture content compared to traditional fuels, while solid or pasty AFs have a higher ash content. Solid AF has a coarser granulometry than other fuels, leading to poor combustion, while the feeding of AF can lead to extra false air from additional feeding points. The potential inhomogeneity of AF can lead to thermal input fluctuations as well as feeding challenges. The higher chlorine content of AF can also lead to coating formation and blockages in the pyroprocessing system. AF will also change the nature of the kiln flame, in terms of temperature, radiance, length and other parameters. The use of AF also critically affects kiln capacity through the volume of flue gas that is required, but this may only be significant if the kiln is already being used at maximum capacity, for example in a sold-out market. Increased corrosion and thermal shocks due to unstable coatings may also be a consequence of AF use. There will also be an effect on the emissions from the kiln, but these are not always negative: NOx will decrease due to a cooler flame temperature and SO2 may also be reduced. The effects of AF on clinker quality are very specific to the conditions of the plant and can be either positive or negative (or neutral). Stéphane pointed out that “the higher the process complexity, the more important is the regularity and stability of the whole clinker process.” Before stating with AF, you should make an estimate of the effects on the pyro-system. Consider the lessons from other plants, both successful and unsuccessful. Always inject at the calciner first, since impacts are lower. Use the various ‘tools’ that will help with AF use, but always start with a stable and optimised kiln system.
Basri Ogut of ATS Group - Walter Materials Handling next spoke on best practices for AF dosing and feeding installations using case studies from Sharjah Cement (UAE), Holcim Ecuador, Cimentas Izmir (Turkey) and the Martres-Tolosane plant of LafargeHolcim in France. The project at the Holcim Guayaquil plant in Ecuador in particular was unusual, in that the AF was dosed into ‘Doseahorse’ dosing unit at the top of the preheater and thence into a double valve airlock, using an orange-peel grab system that dug into a storage pit at ground level, the entire handling system being enclosed in a full-height purpose-built tower.
The first paper in the session on AF preparation was given by Katrin Salbrechter of the Montanuniversität Leoben, Austria, on the theory and practice of the drying effects of the new Rocket Mill. The AF being dried in the mill contains moisture in a number of forms, including capillary water, absorbed water, pore water and internal micropore water, the first two being rather easier to eliminate that the pore water and internal micropore water. In the Rocket Mill, 67% of the energy introduced into the system is used up in shredding, while 27% is used in heating up the material and associated process air: 5% is considered as ‘loses,’ possibly due to radiative heat loss from the equipment. Katrin stated that in her experiments, input moisture was 11% and output was 7%, a reduction of 37% and comparable to other stated results on the mill which suggested a reduction - processing higher moisture material - from 25% to around 15% (a reduction of 40%).
Luigi Di Matteo of the Di Matteo Group of Beckum, Germany, next suggested an holistic approach to AF use in the cement industry. Luigi said that AF must be characterised not only in chemical, physical and thermal terms, but also in safety hazards. He pointed out that a particle goes through a number of steps during ‘combustion,’ starting with drying, passing through pyrolysis and the release of volatiles, thence to ignition, coke burnout and finally leaving behind the residual ash component. Luigi said that AF must be stored carefully, in order not to over-consolidate the materials and to avoid handling problems. He pointed out that for each important step in AF utilisation, from reception, preparation, storage and transport, to dosing and feeding, Di Matteo offers a variety of equipment solutions, depending on scale, material types and client requirements and budgets.
Felix Bartknecht of SICK AG next spoke on sensor solutions for AF usage. He gave details of a particular case with a belt scale being used with AF, which was prone to a variety of maintenance and usage problems. SICK offered a laser scanner for non-contact volume flow measurement, which also provides information on bulk height and on the centre of gravity of the material on the conveyor belt. The scanner can also be used for crusher, raw materials, coal, AF, clinker and stockpile monitoring and measurement. Another plant used a LiDAR instrument with image analysis to detect deformed tyres which would tend to block the tyre handling system. Felix finally outlined the use of the SCP3000/MCS300P hot-wet gas sampling and analysis system, which keeps the process gas at above 200°C so that there is no condensation and no gas cooler is required and which can be used to measure circulating elements and to control combustion, thermal conditions and fuel consumption.
The penultimate paper at the conference was given by Frank Thomasberger of Schenck Process Europe GmbH, looking at Multiflex precision dosing for alternative fuels. The Multiflex is a screw weighfeeder, fixed on load cells, where the dosage is proportional to the speed of the screw. Frank pointed out some of the challenges of obtaining an accurate value for dosing from a screw weighfeeder, particularly when dosing problematic materials like AFs. For example, the filling level of the screw must be known (or it must always be full, for instance with the use of a wide inlet into the screw), the system must be calibrated and shunt forces must be handled or avoided. The system is also designed to cope with explosion risks. Frank suggested that the measurement value accuracy of the system is 99% of the actual feed rate.
The final presentation at the conference was given by Oscar España of Vidmar Group, on a special belt weigh-feeder for alternative fuels. Oscar firstly pointed out Vidmar’s capabilities for AF in reception, classifying, storage and dosing. Oscar suggested that it is more sensible to think about dosing rates in terms of energy/time rather than mass/time, due to the wide variability of the CV of AF. Flexibility of feeding and dosing is required especially when feeding different AFs with different CVs. He suggested that the most important thing about a dosing system is that it should never stop and should have 100% reliability: repeatability is crucial, but accuracy - he suggested - is of lower importance, since the other components in the pyro-system will be tuned to deal with whatever the dosage system actually doses. He outlined the newly-designed AWF adaptive weigh feeder with integral lump breaker and double weigh bridge.
Conference prizes and farewells
At the conference farewell reception a number of prizes were awarded. SICK was awarded the best exhibition stand prize. Stéphane Poellaer of Alterline was awarded third place for his paper on mitigating the negative process effects of AF, Matthias Mersmann of aixergee Process Optimisation was awarded second place for his paper on calciner modifications to maximise AF use. The winner of the prize for best presentation was Luigi Di Matteo of Di Matteo Group for his paper on an holistic approach to AF use.
The conference was highly commended for its organisation and for its technical content and delegates agreed to meet again at the 13th Global CemFuels Conference in February 2019, in Amsterdam.
