2nd Global Synthetic Gypsum Conference & Exhibition 2017
30 - 31 March 2017, Düsseldorf, Germany
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The 2nd Global SynGyp Conference on synthetic gypsum has successfully taken place, in Düsseldorf on 30-31 March 2017, with 80 delegates from 20 countries in attendance. 16 papers were presented at the event, alongside an exhibition of syntheic gypsum-related products and services. The next Global SynGyp Conference will take place in 2019, with the location to be announced.
The first speaker at the conference was Jörg Demmich of Knauf, speaking on behalf of Eurogypsum, on trends in synthetic gypsum in Europe to 2050. European energy policy is now aiming at a ‘completely carbon-free’ energy supply by 2050. The level of renewable energy supply ranges from 9% in Czechia to more than 80% in Austria (30% in Germany). Sweden’s coal-fired energy production is only 0.3% of its total, but is 81% of Poland’s supply (40% in Germany). European production (EU15, ECOBA figures) of FGD gypsum is around 18-19Mt, of which 7Mt is from Germany. Around 60% of the supply of gypsum for German wallboard production is synthetic gypsum, with the remainder natural gypsum. Starting in 2010, the German Climate Protection Plan started to reduce the carbon intensity of electricity production in Germany. Under any of the various scenarios that have been put forward, Germany will eliminate its coal-fired power generation by 2050, while also eliminating its nuclear energy sector by 2022. Depending on the scenario, German FGD gypsum production will reduce to lower than 2Mt by 2040. At the same time, a wide variety of options have been published for energy policy in Europe to 2050. However, on the most authoritative studies, coal and lignite fired power production will reduce to 2-15% of the total in Europe by 2050, from 25% in 2014. On this basis, European FGD gypsum production will fall to around 5Mt/year in 2050, with Poland becoming the largest producer. In response, the German and European wallboard industry will increase its recycling activities. Recycled gypsum will partially replace the ‘lost’ FGD gypsum, but natural gypsum will be the main source of replacement material. 0.15-0.3Mt of recycled gypsum is produced in Europe today, but Jörg suggested that the maximum production in the EU would only amount to 2Mt/year, partly due to technical limitations.
Thomas Duve of ZAG International next spoke about gypsum use in North America. Circulating fluidised bed coal-fired generating stations tend to produce anhydrite, which cannot be used for plasterboard production. Historically, US natural rock gypsum supplies reduced as synthetic gypsum supplies increased. Now, however, the main trend of relevance in the US is that energy production has switched over to cheap natural gas, rather than using relatively expensive coal. Coal-fired power production and FGD gypsum supplies have dropped and will continue to fall, despite promises to bring back coal. Gypsum imports into the US have increased to around 4Mt/yr and are set to increase further.
Joe Harder of OneStone consulting next spoke on behalf of UK-based consultancy Smithers-Pira, on synthetic gypsum supply and markets to 2027. In 2017, the global supply of synthetic gypsum is estimated at 150Mt, rising to around 220Mt in 2027. The value of the gypsum is estimated at US$1.1bn in 2027. Modest growth is forecast in the US, decline in Europe and growth in Asia, particularly in China. In 2014, these three regions accounted for 96% of global synthetic gypsum supply, with Asia alone accounting for 65%. By 2027, Asia will account for 73% of global supply. According to Smithers-Pira, of synthetic gypsum that is utilised, 93% is used in plasterboard production, with only 3% used in cement, and 2% used as a soil conditioner. Coal-fired power generation is expected to grow rapidly in Asia, particularly in India, Vietnam and Indonesia, as well as in Turkey, although the production of synthetic gypsum may not match these power production growth rates. Environmental regulations are a strong driver in synthetic gypsum supply, but perhaps the strongest factor is the relatively low cost of natural gas, which is undercutting the use of coal. Globally, there are around 6700 coal fired power stations, with another 4300 in development. However, in 2010-2016, plans for over 900 proposed coal-fired power plants were cancelled. Sectors that have the most potential for increased use of synthetic gypsum are agriculture and as a setting control agent for self-leveling floor screeds.
Arno Wess of Envigo next spoke about the toxicology of gypsum and of FGD gypsum. He pointed out that the calcium and sulphur in gypsum are not toxic, but that any toxicological effects will come from any impurities that may be present. In his study, Arno Wess studied 17 metals or semi-metals that have been found at very low levels in gypsum. Skin exposure has been shown to be safe, while calcium sulphate is a widespread food additive. The only relevant exposure is via dust or aerosol inhalation, since impurity metals have no significant vapour pressure, so that repeated low dose chronic exposure was used as a dosage basis for the study. Producers and consumers are likely to have different exposure profiles, with a gypsum industry worker on an eight hour shift exposed to a high concentration of gypsum dust and with no respiration being the worst possible likely exposure. Mercury is the only metal that has a significantly different concentration in natural gypsum and synthetic gypsum - all other impurities exist at comparable levels. However, even for mercury in synthetic gypsum, the overall risk is exceptionally low. The highest risks come from manganese and arsenic, but again, at relatively very low levels. Essentially, even in the worst-case scenario, gypsum and synthetic gypsum are safe.
Thomas Schröder of Lechler GmbH next spoke on the influence of spray nozzles on FGD system efficiency. Thomas pointed out that every FGD unit can be improved through optimising the gas distribution and by improving the surface area of droplets for chemical reactions. By imparting a swirl to droplets discharged from spray nozzles, gas distribution can be improved, particularly when pairs of nozzles are set up to impart opposite counter-rotating swirl directions. This process also leads to a secondary atomisation of droplets due to drop collisions and an increase in droplet surface area for reactions. The paired nozzles allow creation of turbulent but swirl-free flue gas flow, which avoids the concentration of airflow along the walls of the reaction vessel. In a case study of a power station in Turkey, it was found that a higher concentration of counter-swirling spray nozzles allowed the power plant to either increase its flue gas cleaning efficiency, or to use higher-sulphur, lower-cost coal.
Next up was Tarja Korhonen of Valmet Technologies Oy. In semi-dry FGD, the feed chemical is hydrated lime or quicklime, with a hemihydrate end product that contains variable quantities of lime. The lime stoichiometry increases with the degree of desulphurisation, typically in the range of 1.2-2. This semi-dry process end product may have 20-30% content of ‘available’ lime and is currently landfilled. The quality of the product is variable and it may also contain a high amount of sulphate and soluble salts, but it is more reactive than commercial limestone and has the advantage of being free. Some limited redesign of a wet-scrubber system is required to be able to use this by-product, but using the material as a reagent in a subsequent wet FGD system has the advantage of converting the material into high quality synthetic gypsum.
Yilmaz Sakilli of the University of Siegen next spoke about the influence of seed crystals on the hydration of hemihydrate. Gypsum (dihydrate) seed crystals are generated from a super-saturated solution formed from the dissolution of hemihydrate crystals. The seeding process is influenced by the calcium and sulphate concentration in the solution, while Yilmaz reminded listeners that the solubility of all calcium-sulphate-based minerals reduces with increasing temperature.
Christian Prizel, also from the University of Siegen, pointed out that a variety of materials can be used as precursors for the production of hemihydrate or anhydrite. Christian explained in detail the chemical and mineralogical changes that occur with increasing dehydration of dihydrate, through to the production of anhydrite I and anhydrite II.
Richard Ellis of Schenck Process UK finished the programme on the first day with a presentation on the differences between synthetic and natural gypsum with regards to pneumatic conveying. Richard pointed out that it might take two or even three times as much air/energy to convey the same amount of uncalcined synthetic gypsum compared to conveying natural gypsum due, he explained, to the amount of air that passes through the synthetic gypsum without doing useful conveying work, due in turn to the crystal morphology. After calcination, the energy penalty still exists, but to a lesser extent. Characterisation of the material before designing the pneumatic conveying system is critical. The minimisation of bends and the optimisation of conveying speed (as well as deciding on whether to use lean, medium or dense phase conveying) can help with optimisation of the system design.
Conference dinner
The conference dinner took place at the Classic Remise car centre in Düsseldorf, with delegates enjoying smooth jazz while dining surrounded by tens of millions of Euros-worth of classic cars. ‘Look but don’t touch!’
Second day
Michael Jakob of LECO Europe started the second day with a presentation on quality control of FGD gypsum using a macroTGA system. Thermo-gravimetric analysis (TGA) is a well-known approach to mineralogical analysis - macroTGA uses larger sample sizes of around 5g. Alumina crucibles are heated to around 1000°C on a balance and the weight change is measured. For samples of ‘gypsum,’ free moisture is driven off at up to 50°C, dihydrate breaks down at up to 240°C, hemihydrate at up to 400°C and calcium hydroxide up to 550°C. From the progress and proportions of weight change at each temperature, the detailed composition of the original sample can be calculated.
At the start of the next session, on applications, handling and processing, Michael Gramling of MHC Engineering Foerdertechnik GmbH spoke about silo extraction and handling of poorly-flowing synthetic gypsum. Michael pointed out that synthetic gypsum is sticky due to its high content of fines and moisture content, and that it tends to consolidate and harden over time, exacerbating flow problems. Extensive testing of the material in question is required before the design of the silo and extractor can be finalised.
Jaap Ruijgrok of ESI Eurosilo next spoke in depth on silo design, particularly with regard to time consolidation of synthetic gypsum. Water can be used to convey the water to the top of the silo as a liquid sludge and dewatering can be effected at the top of a storage silo using a vacuum filter. A subsequent spreader-auger is used to spread thin layers of synthetic gypsum at the top of the silo, which then also allows some evaporation to take place, further reducing moisture content. Augers are then used to recover the material to a hollow central column and chute. A drainage system at the bottom of the silo can deal with any moisture which is pressed out of the gypsum during its time in the silo. Jaap suggested that synthetic gypsum should not stay in a silo for more than three months.
Nik Velten of Aumund Foerdertechnik GmbH further spoke about the challenges of handling and storing synthetic gypsum. Since 1922, the company has installed over 1000 machines for handling natural or synthetic gypsum and, through a process of company acquisitions over the years, now has a complete array of material handling solutions. Nik mentioned that there are not many new projects around the world and that Aumund is now concentrating on upgrades and retrofits, as well as on worldwide service and spare parts provision, including the improvement of the equipment of its competitors.
Evgeniy Torochkov of the Russian Research Institute for Fertilisers, part of the PhosAgro group, started the next session with a presentation on phosphogypsum. His institute uses a two-stage wet process of phosphoric acid (fertiliser) production, which creates five tonnes of phosphogypsum (PG) for each tonne of P2O5 acid, which is the intermediate chemical in fertiliser production. Around 6Bnt of PG has been created worldwide up to 2014, with 1.8-3Bnt discharged to water bodies and 2.6-3.7Bnt stored in stockpiles. Only around 13.4% of the PG created each year is actually used. Naturally occurring radioactive minerals occur in phosphate ores, some of which will end up in the PG by-product. Evgeniy pointed out two reports that indicated that phosphogypsum is essentially safe to use as a by-product in a number of applications. For example, China has stipulated that 15% of PG must be used as a mineral resource already, rising to 30% by 2025. In the former USSR, PG use was concentrated in the agricultural sector, while in Japan the majority of PG was used as gypsum plaster. The Prayon Engis plant in Belgium uses the two-stage phosphogypsum process, manufacturing a high-quality PG by-product that is widely and commercially used. China, the US, Russia, India and Brazil are the leading manufacturers of PG, although China alone currently produces around one third of the world’s PG. Evgeniy suggested that PG is on the edge of ‘respectability’ once more.
Luca Plakopitis of Fluorsid gave the penultimate presentation at the conference, on fluorogypsum (FG), of which around 3Mt is produced annually around the world. FG is produced as anhydrite and is used mainly in the building industry, whereas pelletised FG is mainly used in the cement industry. FG is a byproduct of the reaction of dry fluorspar with sulphuric acid for the production of hydrofluoric acid; a synthetic calcium phase is produced which is then neutralised with calcium hydroxide to achieve a product with a pH of around 12. FG can be used as a binder in indoor applications, with a compressive strength of 25MPa after three days and 40MPa after 28 days, as well as low shrinkage. FG is best suited as a self-leveling floor screed, although it can also be used as a binder of mineral-based blocks. When combined with ammonium nitrate, the FG can be pelletised and used as a setting time modifier in the cement industry. Luca gave details of some new applications for FG; when combined with milled tyres and acrylic resin, the material can be used for cycling or jogging tracks; when mixed with milled recycled glass, panels can be formed with very high fire-resistance and no cracking after a fire test of 30 minutes. When combined with water-proofing agents such as soaps, siloxanes and resins, FG may increasingly be used in outdoor applications. Indeed, FG has now been used in outdoor concrete applications. FG-based concrete exhibits no differential cracking, no shrinkage, no frost expansion, no alkali-silica reaction and no damage from de-icing agents.
David Sevier of Carbon Cycle Ltd gave the final presentation at the conference, on a new low-cost method to purify gypsum to high-whiteness fillers, with equal or higher whiteness values than for precipitated calcium carbonate (PCC) or even titanium dioxide. Essentially, ground gypsum is mixed with a liquid complexing solution; pure gypsum settles out as a complex, separated from larger particles of non-gypsum mineral contaminants, finer particles of non-gypsum contaminants and a separate layer of paper fibres if they are present. This can be achieved at a cost of around Euro5/t, using a vat-based process, and with the complexing chemicals being recycled. PCC typically sells at around Euro200-500/t and David suggested that his process could eventually produce ‘the filler of choice.’ The high-whiteness gypsum is soluble, so that it would have to be coated to be usable in paper manufacturing, but David suggested that even with a stearic coating, his product would undercut PCC in terms of cost of production and potential sale price. David finally suggested that his process could be used to separate rare earth elements (and uranium) from phosphogypsum, to form a concentrate that would be more than twice as rich as commercial ores.
Prize-giving and farewell
At the end of the conference a number of prizes were awarded. ESI Eurosilo won the ‘best exhibition stand.’ Christian Pritzel of the University of Siegen won third place in the best presentations awards, while David Sevier of Carbon Cycle was second. Luca Plakopitis of Fluorsid won the prize for the best presentation, for his paper on fluorogypsum technical properties and markets.
Delegates rated the conference highly, for its technical content and for the quality of networking.
Delegate comments:
• The organisers are highly knowledgeable;
• Compliments on the organisation;
• Perfect organisation;
• As gypsumboard manufacturers (based on FGD gypsum) it was very interesting to us to hear new info!;
• It is quite perfect;
• Good organisation and good connection possibilities;
• My favourite thing about the conference was the high quality of the delegates;
• Good balance between various topics;
• Networking was good, organisation was good;
• Balance between papers and discussion time was very good;
• Nice job!
