1st Global Synthetic Gypsum Conference & Exhibition 2015
20 - 21 April 2015, Chicago, US
Review by conference convenor Dr Robert McCaffrey
The first Global SynGyp Conference on wet scrubbers and synthetic gypsum has taken place in Chicago, on 20 - 21 April 2015, attracting around 115 delegates from 15 countries. The second Global SynGyp Conference is planned to take place in Germany in 2017.
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The conference started with an evening welcome reception in the exhibition area, where many new contacts were made. The next day the conference started in earnest, with a presentation by conference convenor Robert McCaffrey giving the basics on synthetic gypsum.
The first full-scale air-scrubbers installed on a coal-fired power station were on the Battersea Power Station in London in the early 1930s but now nearly half of the wet scrubbers in operation on coal-fired utilities are in the US, with another 25% operating in Germany and nearly 20% in Japan. Wet scrubbers are expected to be progressively installed in pollution-hit China in the coming years. Wet scrubbers produce synthetic gypsum by reacting a solution of limestone or lime in a fine spray with sulphur-bearing boiler exhaust gases in a scrubber tower. The sulphur and calcium-containing droplets fall into a tank at the bottom of the scrubber where air is blown in to force oxidation to create needle-like crystals of gypsum, which are then removed from the bottom of the tank and are dewatered, typically on a vacuum belt. The vast majority of synthetic gypsum-producing wet scrubbers use some variant of this limestone forced oxidation (LSFO) technology, which has been found to be cost-effective and reliable.
Rob Crangle of the USGS next spoke about US synthetic gypsum production, value and usage trends. The Clean Air Act of 1970 reduced the amount of sulphur emitted to air, but, Crangle pointed out, did not tell power stations to produce synthetic gypsum - it is a by-product. In the US, Appalachian and Illinois coal basins have high sulphur levels and are contained in thin seams. Western coal basins including the Powder River Basin (PRB) are low in sulphur and occur in thick seams, but are typically far from power generation stations. Flue-gas desulphurisation (FGD) gypsum will be made whether it is used or not and much more is produced than is consumed: 22.1Mt was produced in 2013, with only 49% consumed by industry (up from 2% in 1975).
Around 35 different states allow the use of FGD gypsum for agriculture and this is a strongly growing area. There have been some concerns about FGD gypsum composition when it is used for agriculture, with regards to heavy metals, chloride content and/or fly ash content. Up to the early 2000s, FGD gypsum was typically sold at US$1 - 2/t, and has now, perhaps, risen to approximately US$5/t, although pricing is opaque. Transportation costs are potentially the crux factor in whether the FGD gypsum is used or stockpiled (or landfilled). Conversion of coal-fired power stations to gas, as well as consolidation among energy companies, is starting to impact on long-term supply of FGD gypsum. The Tennessee Valley Authority (TVA) Kingston slurry spill of 2008 (even though it was a fly ash slurry lagoon that failed) has led to increased oversight of coal co-combustion products (CCPs). The TVA has started to convert its facilities to dry storage of fly ash and FGD gypsum, at a cost of US$2bn.
Bill Stanley of ZAG International next spoke about supply trends in CCPs in the US and worldwide. Bill forecast that cement demand in the US will continue to increase, that environmental regulations will become more stringent, that there will be major changes in the supply of CCPs, that raw material sourcing including alumina, iron and gypsum will become more critical and that a long term approach will be crucial. Stanley suggested that a 'perfect storm' is forming, with increasing costs of compliance with EPA regulations including NESHAP, aging coal-fired power stations becoming more expensive, deregulation, uncertainty of future greenhouse gas regulations and the very low cost of natural gas all conspiring towards the closure of coal-fired generating stations and the reduction of the availability of CCPs. The closure has been announced of over 400 units in 25 states, counting for 25% of national generating capacity but accounting for around 40% of capacity in the east of the US. New regulations on mercury emissions are also complicating decisions on future generating capacity.
Joerg Demmich of Knauf, speaking on behalf of Eurogypsum, spoke about future FGD gypsum supply trends in Europe, in the light of shifting energy policies. Eurogypsum's members have a turnover of around Euro7.7bn per year in Europe, with 154 quarries and 164 plaster, block and plasterboard factories, employing 28,000 people directly. EU28 FGD gypsum production is currently around 18 - 20Mt per year, of which 7Mt is produced in Germany, the vast majority of German synthetic gypsum being used or stockpiled for later use.
Demmich stated that the common objective of European energy policy is to reduce greenhouse gas (GHG) emissions by 20% by 2020 and to increase the share of renewables to 35% by 2030, to achieve a competitive low-carbon economy by 2050, with a reduction in GHG emissions of 80-95%. The energy-mix picture varies from country to country in the European Union (EU), with Hungary currently using only 6% renewables, to Austria using 65% renewable energy, mainly from hydropower. Coal and lignite share in the energy-mix varies from 1% in Sweden to more than 90% in Poland, with an EU average of 27%.
Uniquely, Germany has a clear 'roadmap' for energy generation until 2050, with reducing dependence on coal and lignite and increasing reliance on renewables including wind and solar. In September 2010, the German government decided to increase the proportion of renewables in electricity generation, to 35% by 2020 and 80% by 2050. According to the plan, only around 4% of German electricity will be produced by coal-fired power stations in 2050, while at the same time the overall power consumption will be reduced compared to 1990. In spring 2011, the German government decided, post-Fukushima, to eliminate nuclear power from the national power mix, from 23% currently, to zero by the mid-2020s. With these changes in mind, Demmich forecast that FGD gypsum production in Germany will progressively reduce, increasingly quickly after 2030, to between 0.3 - 2.2Mt by 2050.
Using a variety of studies, the suggestion is that coal and lignite share in electricity generation in the EU28 will reduce progressively, with FGD gypsum production dipping to between 7.8 - 11.7Mt in 2030. To counter these trends it will be necessary to increase the recycling rate of gypsum to create a new source of gypsum (perhaps supplying up to 2Mt/year in Germany) and also to increase the supply of quarried natural gypsum.
Robert Morrow of Innogyps next spoke about the challenges of negotiating a long-term supply agreement for synthetic gypsum. Morrow wanted to dispel two 'myths:' that the gypsum wallboard industry has a lot of money, and that FGD gypsum is a 'waste.' Freight is the number one cost that producers and users have to take into account. The quality of the synthetic gypsum is critical, and largely involves ensuring that unwanted components are not present. The physical characteristics of the synthetic gypsum, in terms of handling and storage properties, can be crucial to its value. FGD gypsum from different sources will vary in its composition and its handling characteristics. Morrow said that producers generally want a guaranteed 'take' for the FGD gypsum and typically want to publicise the deals. A consumer of gypsum such as a wallboard company wants a guaranteed 'supply,' without a guaranteed 'take' clause, and contract value secrecy. These two approaches are diametrically opposed and are difficult to square. It is in the interests of both parties to go with a long term deal - typically beyond 25 years - up towards the lifespan of the factory - because the costs to change are so high.
For users, the gypsum purity is critical, as are the absence of contaminants, its particle shape and size, and its moisture content. The parties to any agreement must be able to agree on the quantities to be provided and taken, with provisos for production interruptions. To a power company, price of FGD gypsum is a political issues - they cannot give it away - but from the gypsum company's viewpoint it is a commercial issue. Robert suggested that contracts should have a 'reset' clause that allows renegotiation should circumstances change. Communication between the synthetic gypsum producer and user is crucial, with daily, weekly or at the least monthly meetings taking place. Local government departments are typically very helpful in putting together agreements and in helping to sort out logistics. Robert concluded in saying that agreements are best conducted in a cooperative environment, rather than in a competitive or combative atmosphere.
Operation modes and FGD gypsum quality session
The first speaker in the FGD gypsum quality session was Harald Schmidt of Knauf, who said that his company started working with FGD gypsum as far back as 1977. The company now processes around 7Mt of synthetic gypsum each year, the majority of it FGD gypsum from 65 different power plants around the world, including in China. Harald started by saying that the quality of the limestone is the first determinant of final FGD gypsum quality. Less than 2% MgCO3 is critical. Hydrocyclones can be used to effectively reduce water content of the stream of gypsum from the scrubber bottom and also has the effect of selecting a larger crystal size: smaller crystals and impurities tend to be recirculated in the hydrocyclone overflow. Fresh wash water is used on the vacuum belt filter where FGD gypsum moisture content is reduced to 10%. The pH value of the slurry in the scrubber is critical in determining its performance and the quality of the gypsum produced, and should typically be between pH 5 - 6. Eurogypsum's quality criteria for FGD gypsum include <10% moisture, better than 95% purity, less than 0.1% magnesium salts, less than 0.5% hemihydrate, neutral or near-neutral pH, no smell and non toxic, among other criteria. 'Perfect gypsum' is blocky and with a d50 value of more than 32um.
The composition of the coal will also affect the FGD gypsum: three times as much lignite must be burned for the same amount of coal power, so big absorbers are used, leading to large crystal sizes. Plants with lower running hours per year will tend to have larger and more needle-like FGD gypsum crystals. The time of residence of incipient gypsum crystals in the scrubber will control their crystal morphology. Water-soluble salts must be reduced to practically zero if the FGD gypsum is intended for wallboard use, since they will tend to migrate to the board-paper interface, ruining the board. The more that the coal-fired power station and its scrubber is stopped and started, typically due to economic constraints and fitting in with sporadic renewable energy supply, the greater will be the impact on the produced gypsum quality, when there also tends to be a wider particle size distribution.
Bruce Keiser of Nalco next spoke on the topic of mercury emissions from coal-fired power stations. Where does the mercury go if it is not going out the stack? Mercury will occur in the flue gas from the boiler, and if it is in elemental form it will pass through the scrubber unaffected and will be emitted from the stack. Reduction of Hg2+ in the scrubber through the addition of an additive that blocks it from being reduced into elemental Mercury, such as an additive available from Nalco - MerControl 8034 Plus - can lead to lower mercury emissions from the stack and an increase in mercury in scrubber wastewater. There is no significant change in the physical form of the FGD gypsum produced in the presence of the additive. The TCLP Mercury leaching test is essentially unchanged and well-within compliance limits after additive addition. "In wet FGD gypsum systems, it has generally been observed that mercury is enriched in fine (<20um-diameter) solids and occurs in lower concentrations in larger solids in the presence of the additive," according to Keiser.
Complete release of mercury from gypsum will occur at temperatures greater than 600C, but flash calcination, processing in a gypsum kettle and board drying in dryers will be at a temperature lower than 200C. The use of the additive makes no difference to mercury stability in FGD gypsum. Mercury halides will tend to give up their mercury at temperatures at around 125°C. Process parameters such as ORP (oxidative reduction potential) may favour the transfer of the mercury into the liquid phase of the scrubber, as opposed to the solid gypsum phase. Nalco's additive can allow a scrubber to operate at a high ORP, producing high quality FGD gypsum with lower Hg content, while still being compliant with EPA regulations and not sending Hg up the stack.
Scott Miller of Aecom spoke about requirements for producing wallboard-quality synthetic gypsum. Scott pointed out that utilities have to operate the scrubber in a manner that is most effective in sulphur reduction, but that also minimises the presence of impurities, that generates a gypsum crystal size that is applicable for wallboard product, that ensures adequate oxidation but not over-oxidation and that adequately reduces soluble salt content, while allowing efficient dewatering without affecting production. Using a high quality limestone with low Mg content, ground to the correct size, will optimise limestone use and will reduce the amount of unreacted limestone in the produced FGD gypsum.
Fly ash in the scrubber will have effects through complexing of aluminium-fluoride or sulphide with limestone, reducing its reactivity. The solids content of the scrubber liquor must be managed to the optimum level, in order to manage crystal development. Natural oxidation relies only on the oxygen in the flue gas, but is affected by the temperature and pH of the flue gas, and by the ORP at which the scrubber is operated. Wastewater regulations are going to change so that the plants will not be able to dispose of water without pretreatment. The pH of the water may be altered through the addition of lime, forcing heavy metals to precipitate out, with solids filtered and disposed of as a sludge, while the resulting effluent stream may require additional treatment, perhaps biological treatment through anaerobic bacteria, or through ion exchange. The sludges produced may be mixed with other CCPs to form a material with pozzolanic properties. Brine concentrators and crystallisers can also be used to treat wastewater solids. Another zero-liquid-discharge option would be the use of an in-duct waste heat evaporation system, or slipstream waste heat evaporation. Scott finished with a detailed list of potential scrubber/FGD gypsum problems and their potential origins and solutions.
At the end of the first day of the conference delegates enjoyed a sunset meal at the Cité restaurant at the top of the Lake Point Tower skyscraper, with stunning views of both the city and the picturesque Lake Michigan shoreline.
Conference second day
On the second day of the conference, Joe Sprigg of Alabama Power Company spoke first, about a recurring crystal shape challenge at his scrubber unit at the Plant Miller unit. The 130,000t/year of gypsum produced at the unit is around 96% pure. However, in spring 2011 there was a sudden increase in FGD gypsum moisture to above 15% the majority of the time, which caused buyers to start to reject the product. The change coincided with a change at the plant from full base load operation to a minimum operational mode. Sprigg said that money spent on improving gypsum quality is not money that will ever see a return on investment. Sprigg said that the gypsum was plate-like or flaky, with few rod-shaped crystals, and some penetration twinning caused by crystal lattice defects.
However, no 'smoking gun' cause was found for the moisture increase. A lower-magnesium limestone was tried, with no effect, and careful tuning of limestone grinding size was tried, with some decrease in moisture content when using slightly coarser limestone. A surfactant dewatering-aid was tried that allowed the vacuum filter to work better, but it was costly and its environmental performance could have been improved. A system reset using cleaned tanks and fresh water gave blocky crystals with lower moisture content, but within a week the flat disc-like crystals were back. Sprigg suggested that the cycling operation of the boiler may have meant that the pre-scrubber-ESP was not operating optimally, with relatively high levels of fly ash making it through to the scrubber unit. There was also a suggestion that there may have been some contamination of the open scrubber tanks by airborne particulates. Since the replacement of one of the electrostatic precipitators, moisture levels have mainly stayed below 10%, which is an acceptable level for FGD gypsum customers.
During discussions, it was suggested that Sprigg try operating his scrubber liquor tank at a lower solids content level, perhaps at lower than 20% compared to the current level of above 30%. We look forward to hearing about his progress.
John Glasscock and Lam Thai of Synthetic Materials/Superior Belt Filter next spoke on recent developments in synthetic gypsum dewatering. A belt filter has a moving filter cloth sitting over a vacuum box which sucks the water out of the filter cake. A traditional full scale dewatering system might cost US$30 - 120m, with a two to four year construction period, typically with fully redundant systems and requiring significant staffing, and chemical testing to ensure product quality. However, a newly-developed trailer-mounted vacuum belt filter can sit on the back of a semi-trailer truck, has a 1m-wide belt and can produce FGD gypsum at 28t/hour at 8 - 12% cake moisture: the slurry dewatering capacity is around 150 gallons per minute at 20 - 50% solids content. The new portable system can be started within days if a utility requires new or additional flue gas desulphurisation capacity, or in the case of pond closure or other process requirements.
Ed Kercher of Lancaster Products, on behalf of Keith Day of Beneficiate North America, spoke about the possibility of pelletising FGD gypsum, making it more readily transported and stored, after using high-shear mixing technology to form fertiliser pellets. A high-shear mixer provides a consistent mix quality, with all internal surfaces of the mixer continually cleaned to prevent build-up, and providing a homogenised mix while minimising the amount of additives required. A counter-current rotating pan mixer is a rotary vessel which has both a very high speed primary mixing rotor, and a secondary slower mixing plough inside the vessel to effect the mixing action. A typical mix pelletising cycle would proceed as follows: charge the solids; dry the mix and de-lump; add the liquid; form the seeds; granulate; discharge. A door-to-door cycle time would be between three to ten minutes. FGD gypsum should ideally have a moisture content of around 10% for optimum pelletisation. A binder such as starch may be required to stabilise the pellets, while at the same time allowing any fertiliser release as quickly as possible when the pellets are applied to the land.
Jody Saiia of Sparstane next spoke about a new technology for converting FGD gypsum into ammonium sulphate fertiliser and high quality finely divided calcium carbonate. Saiia suggested that converting gypsum into fertiliser has not historically been economically viable since the need for sulphur is low, there is a long reaction time in the process and potentially the freight cost is too high. Saiia's technology has decreased the reaction time to as low as five minutes, allows control of crystal morphology and creates valuable precipitated calcium carbonate as a by-product, which has turned the economics of the process on its head.
Partly due to the reduction of the prevalence of acid rain, the value of the addition of sulphur to farm land is increasing. Ultra-fine precipitated calcium carbonate (PCC) can be used in the paper industry, plastics, paints, carpets, pharmaceutics and other products. For example, the paper industry annually uses 30Mt of PCC each year, with plastics accounting for around 25Mt each year.
Saiia's technology has been awarded a patent after a lab-scale pilot plant, and the company is now working with a large power utility on a second pilot plant in Alabama. A commercial demonstration plant is under preparation. Ammonia is one of the inputs into the process and is available at the power plant from the SNCR system, while the process also captures some of the CO2 that would otherwise have been emitted by the utility. The PCC can also be re-used in the scrubber. Saiia claimed that the process will be "strongly profitable."
Graham Cooper of Schenck Process next spoke about guidelines for feeding, pneumatic conveying and storage of dry DSG. In contrast to natural gypsum, FGD gypsum will have a much smaller size distribution variation, forming a 'mono-size' material, and creating some handling difficulties. Cooper suggested that FGD gypsum should respond well to aeration, but the narrow grain size distribution makes it difficult to discharge since the material de-aerates very quickly and this means that the flow is relatively slow compared to other materials. Hopper geometry is critical in order to achieve the required flow rates: an outlet cone should be at an angle of 60 degrees with aeration to ensure discharge, with a minimum discharge size of 200mm to avoid bridging. Very often the aeration air is only turned on when the hopper must discharge. However this frequently causes poor aeration because the air escapes through the outlet and does not aerate the material.
Essentially, Cooper suggested that aeration must begin around 10 minutes before the hopper needs to be discharged. For pneumatic conveying of DSG (desulphurisation gypsum), the material must be dry, since wet material will block any system, but otherwise offers convenience, reliability and high availability. For smaller systems and for shorter distances, a dilute phase (low operating pressure, high velocity) system may be the best choice. Higher tonnages and greater conveying distance would tend to suggest the use of a dense phase conveyor system. AutoFlow conveyor pipes have a smaller inner pipe with intermittent 'flutes' to allow the equalization of pressure along the pipes in order to make the system work more smoothly.
Blaz Jurko of Gebr. Pfeiffer started a series of three presentations at the conference on grinding and calcination of FGD gypsum by speaking about a modular/mini mill solution for simultaneous synthetic/natural gypsum milling and calcination. Jurko said that companies generally wish to reduce their risks by decreasing contractor liabilities, and he said that the new modular mill decreases the risk to a minimum by prefabrication of the standard-container size modules for the calciner. Low-cost break-bulk transport is used for module transport to the job site. The modules are then assembled at the job site, mainly horizintally but also on-end if required, using welding or bolts. The system uses a Gebr. Pfeiffer vertical roller mill for milling/calcining. A hot gas generator would be used for material transport within the mill. The system can be used for gypsum processing, as well as for grinding of limestone, cement, slag, pozzolan, and/or coal grinding.
Michale Chen continued on the topic of synthetic gypsum grinding and calcination, speaking on the use of pendulum mill grinding to improve stucco quality. The Raymond roller mill includes a dynamic classifier for product particle size distribution control. The Raymond Cage Mill incorporates an impact mill and a flash calcination process that is popular for synthetic gypsum and which produces wallboard-standard-quality stucco.
The Raymond Impact (or 'Imp') Mill dries, grinds and calcines in one system. Impact grinding helps to disperse the gypsum, with an air-swept grinding zone leading to very effective mixing. However, the Imp mill has a tendency towards variable stucco quality, since larger particles will not necessarily be dried and calcined as thoroughly as smaller particles. In order to achieve a uniform calcination, a longer residence time in the hot airflow is required. In two stage systems, pre-drying with a cage mill can reduce moisture variations into the impact mill, and can lower the gas inlet temperature to reduce overburning, but in this case the particle size distribution will still be quite wide.
Chen spoke about a new two-stage system that uses a pendulum grinding system with an air-swept grinding zone that dries and grinds to create a narrow particle size distribution before a calcination stage to optimise the gypsum flash calcining process for stucco homogeneity. A stucco cooler is being developed to provide waste heat recovery and to lower total power consumption.
Lars Roettger of Claudius Peters spoke about his company's new approach to gypsum calcination. The 'classic' Claudius Peters gypsum calcining ball mill can cope with up to 30% synthetic gypsum. The new FGD gypsum calcining system uses a horizontal impact calciner and homogeniser. Instead of grinding balls in a mill, a disagglomeration disc spins at high speed to break up the already fine FGD gypsum particles. The calcined gypsum particles take on a cracked appearance, with a high specific surface area, but this can lead to a high water demand. The homogeniser is a vertical cylinder with a fluidised bottom and agitators that perform a thorough mixing of the calcined stucco, with a retention time of 30 minutes on average and a throughput rate of 15t/hour. The effect of the homogeniser is to reduce the water demand of the produced stucco and to extend the setting time, while at the same time improving the product strength.
A new version of the homogeniser uses a higher pressure and steam input to further improve the produced stucco's characteristics and to reduce water-soluble anhydrite content to below detection levels. The reduced water requirement of the stucco will mean that the wallboard factory drier will need to evaporate less water, around 100L less water per tonne of stucco produced, reducing energy consumption by 62.7kWh per tonne of stucco.
In discussion, Bob Bruce of Innogyps note that Claudius Peters' homogeniser is strikingly similar to the patented homogeniser offered by the NuGyp company of which he is a co-owner.
Luca Plakopitis of Fluorsid next spoke about the use of fluorogypsum, such as from his company's factory for fluorochemicals for the aluminium industry, situated on Sardinia. Fluorogypsum is derived from the production of gaseous hydrofluoric acid, through the reaction of dry fluorspar and sulphuric acid in a rotary kiln at around 300°C. The fluorogypsum produced needs to be neutralised with limestone after production to modulate its pH, leading to a gypsum purity of around 96.5% with around 1.5% CaF2. The fluorogypsum can be produced as a milled powder or as pellets.
The milled fluorogypsum tends to be used by the construction industry, for self-leveling floors, plasters, masonry products, AAC and blocks for fire systems (which also have good insulating properties). A fluorogypsum mortar can achieve a compressive strength of 40MPa after 28 days, with very low shrinkage. The water-resistance of fluorogypsum can be improved through mixing it with other materials, such as flyash, silica fume, blast furnace slag, metakaolin or Portland cement, of the use of additives such as siloxanes, methylsiliconates, resins, calcium stearate or asphalts. Fluorogypsum concrete has the same physical and mechanical strength as standard concrete, while at the same time suffering no sulphate attack, no alkali-silia reaction and no damage from de-icing agents. The pelletised gypsum is also used by the cement industry.
Gary Albarelli of the Florida Industrial and Phosphate Research Institute finished up the technical programme at the conference with a presentation on the (re)emergence of phosphogypsum. In Florida naturally-occuring sedimentary fluorapatite is mined and reacted with sulphuric acid to create via phosphoric acid a phosphate-based fertiliser, with a phosphogypsum by-product. Five tons of phosphogypsum is produced for every tonne of phosphate-based fertiliser and around 185Mt of phosphogypsum is produced worldwide each year. Around the world the synthetic gypsum is stacked, but in Morrocco it is pumped into the Atlantic Ocean. More than 5.6Bt of phosphogypsum now exists in stacks in 52 countries, growing at perhaps up to 250Mt per year, and with the total stockpiled set to double between 2015 and 2040.
The stacks have been known to cause environmental disasters if they fail or if wastewater dams fail. Phosphate minerals contain naturally occurring radioactive materials including uranium and radium and these radionuclides pass into the phosphogypsum. The US EPA has regulated the use of phosphogypsum based on exposure to radon generated by radioactive decay of radium 226. Albarelli suggested that these regulations were 'a bit on the strict side' and that they made 'absolutely no sense.' However, phosphogypsum is now being used worldwide and the US standpoint is now fairly unique.
Phosphogypsum can be used for agriculture and as a soil conditioner, for road building, as a construction material, as landfill cover, in the glass or ceramic industry, for marine projects and as a raw material for sulphur and cement and also for its rare earth element content. Albarelli suggested that phosphogypsum performs very well in agricultural applications: In Brazil, which is a major phosphogypsum producer, 100% of the material is used for agricultural applications. In addition, a test house has been constructed in Brazil from phosphogypsum-based panels, and no elevated levels of radon were detected. Starting from 'year zero' in 2008, around 35Mt of phosphogypsum is now used each year around the world. In Belgium wallboard is being produced from phosphogypsum, due to a low-radon magmatic source of fluorapatite being available. Phosphogypsum costs vary, but, for example, peanut farmers in north Florida pay around US$8.50/t for phosphogypsum. In comparison, sulphur costs around US$160/t.
Prizes and farewells
At the conference farewell party a number of prizes were given, for the best presentations according to delegate votes. In third place was Rob Crangle from the USGS for his paper on US gypsum trends, and in second place was Jody Saiia for his paper on new technology for making valuable fertiliser and PCC from synthetic gypsum and ammonia. However in joint first place were Joerg Demmich on behalf of Eurogypsum and Harald Schmidt from Knauf, tied on the same number of votes.
Delegates at the first Global SynGyp Conference were very strongly appreciative of the conference, both for its technical content and for the excellent networking opportunities. It was agreed that the conference should take place on a two-yearly basis, and that in 2017 the conference should take place in the European bastion of synthetic gypsum production, Germany. We hope to see you there!