3rd Global Cement EnviroCem Conference on Environmental Technology for Cement & Lime
10 - 11 May 2016 - London, UK
By Robert McCaffrey, conference convenor
• Good conference - very smoothly run;
• Great technical talks and networking opportunities;
• Good cross-section of subjects and technical information;
• Well organised time schedule;
• Like the speed-dating sessions;
• Conference was very nice and detailed;
• Very good time management and spirit;
• Very good discussions;
• Very well organised and managed - Congratulations!
The third Global EnviroCem conference started with a presentation by Philippe Fonta of the Cement Sustainability Initiative (CSI), speaking about the impact of the Paris Climate Change Agreement on the cement industry. The Paris Agreement aims at a comprehensive decarbonation of the worldwide economy by the end of the century. Adaptation and mitigation are considered at the same time as finance in the agreement, with a proposed new mode of international cooperation, including states and non-states (including businesses and NGOs). The legally-binding agreement will involve nationally-determined contributions (NDCs) for all countries (both developed and developing), financial and technological packages and an agenda of solutions. The agreement is both applicable immediately and is subject to continuous ratification, entering into law once at least 55 states representing at least 55% of CO2 emissions have ratified the agreement. The agreement seeks to limit the rise in global temperatures above pre-industrial levels to less than 1.5°C. Regular inventories of greenhouse gases from individual countries will be required, while there are also accounting checks on the large flows of money that are expected to take place (US$100bn/year), as well as other transparency measures. The NDCs themselves are to be revised every five years. Philippe suggested that cement will have a role in the future due to its ability to build robust structures that can resist harsher climatic conditions. The CSI has presented the Low Carbon Technology Partnership Initiative for the cement sector: a ‘statement of ambition’ by the CSI suggests that CO2 emissions may be reduced by 20-25% by 2030 compared to business as usual, if the use of alternative fuels is maximised, if the clinker ratio is reduced as far as possible and if new clinkers and cements are developed. In addition, enhanced energy efficiency in the cement manufacturing process and carbon capture and storage will be used to reduce emissions. If the Paris Agreement is finally ratified, very great changes are in store for the cement industry around the world.
Jan Theulen of HeidelbergCement next spoke about his company’s approach to current environmental challenges. “Coal-fired power production is out,” stated Jan at the start of his presentation, suggesting that fossil-fuel based investments will become ‘stranded assets’ in the future (and provoking the related question, could the same happen to CO2-intensive cement production?). The cement industry produces a large amount of CO2, but the cost of capturing this CO2 is relatively high, compared to other industries. HeidelbergCement believes that carbon capture and storage (CCS) is required for full de-carbonisation of the cement industry, that it will need financial support to be competitively feasible, as well as currently lacking public acceptance. Carbon capture and utilisation (CCU) is commercial today for small and high-value end-products and CCU has the potential to significantly contribute to CCU/S for the cement industry. Jan stated that the cement industry in Scandinavia could have a zero net CO2 emission by 2030, if governments ‘co-operate.’ Jan gave details of a number of different technologies that are in the process of development for the cement industry. An amine-scrubbing system and three other technologies were tested by Gassnova at the Norcem Brevik cement plant. A CO2-based cooler will be installed at HC’s Hanover cement plant. The LEILAC CO2 project involves the indirect heating of the raw materials, so that exhaust gas and decarbonation-generated CO2 are not mixed and CO2 can be more cheaply captured - and a pilot plant is now under construction at the Lixhe cement plant in Belgium. In terms of the use of captured CO2, algae can be grown using exhaust gases, the algae then being used for bulk materials, transport fuels and even for neutraceuticals. Modified cyanobacteria can be used to produce ethanol, for example by US company Joule Inc. Another use can be to use low- or negative-cost surplus ‘green’ electricity (for example surplus electricity from wind turbines) to electrolyse water, using the oxygen for combustion and using the hydrogen to combine with CO2 to produce methane as a fuel. CO2 can also be used to ‘cure’ ash, bypass dust and quarry fines (for example as accomplished by UK-based company Carbon8) to produce artificial aggregates. Jan Theulen concluded that HeidelbergCement is testing and implementing CCS/U and that in this area it is providing leadership in the cement industry.
Next Albrecht Keiser for STEAG Powitec GmbH spoke about the implications for selective non-catalytic reduction (SNCR) of Germany’s latest NOx/NH3 regulations, which inevitably involve ever-more stringent and lower limits. Albrecht suggested that hitting some targets is simple with a good temperature window, but hitting both NOx and NH3 targets, all the time using a ‘better’ temperature window, is that much harder. By 2019, no allowance will be made in the regulations for ammonia slip (excess, unreacted ammonia) from SNCR, meaning that a ‘perfect’ (higher) temperature window will need to be hit every time for NOx and NH3. This can be a challenge with fluctuating process conditions (O2, gas speed, fluctuating AF compositions) and with older or ‘idiosyncratic’ plants. Albrecht’s company can supply an on-line computational fluid dynamics (CFD) calculation system to allow optimised reagent injection, in order to create the best possible set points for the ammonia injection nozzles.
Matthias Mersmann of aixergee process optimisation GmbH continued on a similar theme, about how to achieve low levels of NOx and NH3 without the use of a catalyst. Both SNCR and selective catalytic reduction (SCR) use injected ammonia or urea to reduce NOx levels, but in higher-capex SCR a catalyst is used to transform NH3 to N2 and water. With lower-capex SNCR, temperature, retention time and mixing can be limiting factors of process efficiency. Ammonia must be injected at temperatures of 850-1050°C, retention time must be above 0.5-1 second, while there should be intense mixing immediately after injection. The burnout of solid fuels should have been completed by the injection point, while there should also be low levels of CO, which otherwise delays the kinetics of the SNCR reactions. CFD-based SNCR optimisation provides information on temperatures, NOx and CO concentrations, turbulence, retention times and fuels burnout, while at the same time calculating the optimum injection point for reagents. Matthias gave an example of a European cement plant which had NOx emissions of 500-600mg/m3N, which has successfully used SNCR to reduce NOx emissions levels to the legal limit of 400mg/m3N at the stack. However, the situation was not ‘future-proof’ in that it would not cope with forthcoming lower emission level regulations. The system was extensively modelled with CFD, with gas measurements backing-up the modelilng. A new injection point was added to the calciner, on the basis of the CFD modelling. The new injection station brought about a reduction in NOx, down to a minimum of 200mg/m3N, without recourse to SCR.
Georg Lechner of Scheuch GmbH went on to give details of his company’s technologies for particulate matter (PM), NOx, volatile organic compounds (VOC) and mercury reduction. The catalyst in SCR reduces the activation energy for reactions, in this case down to 200-400°C, leading to high efficiencies and lower reagent costs, as well as reducing the possibilities for ammonia slip. Scheuch can provide SCR installations for both high-dust and low-dust positions, as well as the proprietary DeCoNOx process, which combines regenerative thermal oxidation (RTO) with a low-dust SCR to also reduce CO and VOCs. Such a system has been installed at the Kirchdorfer Zement plant in Austria, combined with a waste heat recovery (WHR) system, with all project guarantees met, including <200mg/m3N NOx and 99% reduction of CO (with the high CO levels allowing the system to run autothermally, without additional fuel). In addition, Scheuch now offers the ‘Xmercury’ system to ‘break’ the mercury cycle. Filter dust from the kiln/mill filter, which is highly contaminated with mercury, is sent to the split preheater (a separate smaller preheater located beside the standard preheater tower). Dust is heated up and releases gaseous mercury. Afterwards the 'mercury-free dust' is captured by the hot gas filter. Mercury-laden gas passes this hot gas filter. Afterwards water is injected to cool down the gas, at the same time as sorbent is injected. At a lower temperature the mercury 'connects' with the sorbent. This mercury-laden sorbent is finally captured by the sorbent bag filter. Sorbent is disposed-of to bins, while mercury-free exhaust gas is put back to the system. The Xmercury system has been installed at the Wietersdorfer Zement plant and the system has achieved mercury reduction of around 80%, “with low disposal costs, no thermal losses and easy operation.”
Mats-Ove Eriksson of Höganäs Bjuf AB next spoke about the possibility of reducing energy consumption through the use of advanced-concept insulating refractory linings in the cement industry. Corrosion problems have previously been caused by condensation of alkalis behind refractory linings, particularly when using alternative fuels, often leading to the failure of refractory anchors and eventual refractory failure. Mats-Ove suggested that a double-layer insulation/refractory lining can lead to energy savings, reduced kiln shell temperatures and reduced corrosion, particularly in the cooler sections of the pyro-system.
Ullrich Speer of Lechler GmbH spoke about how gas-to-liquid interactions can be optimised to increase gas cleaning efficiency in the cement industry. Lechler’s spray nozzles and lances are used in various places in the cement plant, for SNCR, in gas conditioning towers and in various cooling applications. Lechler Laval nozzles are particularly suitable for the cement industry, being clog-resistant and allowing both air and liquids to be independently adjusted. The level of sophistication of SNCR systems can now be very high, including the possibility of individually controllable nozzles, the use of CFD and online coating detection. Through these approaches, the best gas cleaning can be achieved with the lowest possible use of water and of expensive air and reagents.
After the end of the first day of the conference, discussions continued at a social evening at a local hostelry, with traditional British beer and ‘bangers and mash.’
Conference second day
On the second day of the conference, Carl-Henrik Persson of Yara Environmental Technologies continued on the subject of SNCR, in which Yara has over 100 references in the cement industry worldwide. Carl-Henrik revealed a series of tests with a mobile SNCR unit, to find out the optimum position of lances, the best dosage rate and the most effective reagent. Ammonium hydroxide, NH4OH, (rather than urea) is Yara’s preferred reagent, since the reaction is more direct, the reaction time is quicker, there is a higher level of reduction (typically in the region of 85%, compared to 29% with urea), there is a lower level of ammonia slip and there is a lower operational expenditure. It was found that the best place for injections was just after the goose-neck, for example on the top level of a five-cyclone preheater tower. Carl-Henrik reminded listeners that SNCR is a reducing reaction and may cause an increase in CO formation, although this varies from plant to plant.
Steve Werrell of PCME Ltd next spoke about using predictive emission monitoring systems (PEMS) to reduce particulate emission ‘events’ and to ensure compliance. PCME manufactures all of the main technologies for particulate monitoring (opacity, laser scattering and probe electrification), each of which has its own advantages and disadvantages. Many bag houses are now obliged to fit burst-bag detectors, but these detectors can also be used to provide remote observation of the baghouse performance, to find the exact location of any burst bags, to allow preventative maintenance and to save money through improved filter performance.
Richard Lydon of Clear Edge Filtration next spoke about hot gas filtration using ceramic filters. Ceramic or mineral fibre filter candles are employed like fabric bags in the filter housing and are capable of operating at high temperatures up to 900°C. The candles have high efficiency, with emissions down to 2mg/m3N and are corrosion-resistant. The candles are cleaned in the same way as filter bags, using a pulse of cleaning air. Clear Edge candles tend to have long life-spans, of three years or more, partly because these ceramic filters now use a denser outer layer which reduces dust penetration so that performance is retained for longer. Richard finished by giving details of the TopKat catalyst-coated ceramic candle, which can reduce NOx, SOx, HF, HCl and dioxins through a combination of SCR, direct solvent injection (DSI) and dioxin cracking. The first major (non-catalytic) ceramic filter installation has now taken place in the cement industry (in Italy), with good dust removal efficiency, low capex and low opex as well.
Mark Tilley of Lixivia Inc. next told delegates about the use of stabilised basic oxygen furnace (BOF) and ladle slag for use as fillers in cement. Lixivia’s offering is the separation and purification of calcium from lime contained in slag using an ion-exchange approach, which generates a more stable aggregate material, as well as producing valuable purified calcium products such as precipitated calcium carbonate, magnesium oxide and rare earths and at the same time sequestering carbon dioxide. The company is currently operating at the laboratory scale, but is preparing for a scale-up stage.
Dan Summerbell of the University of Cambridge next asked the question, “Can we reduce CO2 from the cement industry by 20% - for free?” Dan pointed out that cement plants have a day-to-day variability in fuel consumption, whereby they might be able to perform at a 20% better level around 10% of the time. Dan asked whether the plants could be made to perform at this better level 100% of the time. After visiting a number of plants, he came to the conclusion that the majority of the variability came from fuel mix and quality variations and from process operational changes, particularly the level of excess O2 (above 2% or so) in the flue gas. Changing operational set-points might indeed bring about reductions in emissions, but the final question posed was whether the changes would be financially worthwhile for the cement industry.
The penultimate presentation at the conference was given by Thomas Binninger of CTP of Graz, Austria, on advanced emissions control. Thomas pointed out that the further down the regulation route that legislation passes, the less ‘wriggle room’ there is, so that the time to influence ‘best available technology’ BAT regulations is at the start, at the EU level, rather than at the national level. CTP offers thermal, catalytic and hybrid systems to address CO, TOC/VOCs, NH3 and NOx. Thomas mentioned a regenerative thermal oxidation unit with an integrated catalytic system, which can achieve very high performance levels, albeit with a significant pressure drop (35mbar) and medium maintenance costs. Such a unit has been installed at the Wopfinger Baustoffindustrie plant at Waldegg, Austria, while another is currently being built in the US.
The final presentation was given by Peter Brealey, on opportunities in the Sudanese cement industry. Peter mentioned a cement factory that had just been built and was undergoing commissioning, whereupon a power cut stopped progress dead. Renewables such as solar may be part of the answer: six 34MW solar parks are planned to provide power for the cement plant, on a cost basis that is competitive with coal-fired generation, in the region of US$0.06/kWh. Peter suggested that the Sudan solar park might send electricity to Khartoum and might even export electricity to Europe, along a line akin to the 2375km-long 600kV (DC) Rio Madeira electricity transmission line in Brazil.
Awards and Farewells
Delegates voted for their favourite presentations at the conference: Jan Theulen of HeidelbergCement received a special mention. However, in third place was Philippe Fonta of the CSI for his paper on the Paris Agreement and its implications for the cement industry; in second place was Matthias Mersmann of aixergee process optimisation GmbH for his paper on how to achieve 200mg/m3N of NH3 without using a catalyst; while the winner was Dan Summerbell of the University of Cambridge for his paper suggesting that the cement industry can gain a 20% performance improvement - for free. The gentlemen are pictured at the top of this article - (left to right, Philippe Fonta, Dan Summerbell, Matthias Mersmann).
Delegates strongly praised the conference for its ‘collegiate,’ friendly and informal atmosphere, for its networking opportunities and also for the technical content of both the presentations and general discussions with delegates.