Displaying items by tag: Slag

Charah Solutions has been steadily building up its fly ash distribution business in recent years with an eye on the supplementary cementitious materials (SCM) market. This week it opened the third of its new series of SCM grinding plants, at Oxnard in California, US. The unit sticks out because it is focusing on grinding natural pozzolans. The plant will receive natural pozzolan by truck and rail and then use Charah’s patented grinding technology to produce pozzolan marketed under its MultiPozz brand. The previous plants in this series mentioned natural pozzolans but this is the first to promote it explicitly.

The change is potentially telling because global demand for granulated blast furnace slag (GBFS) outstrips supply. Both performance benefits and environmental regulations are pushing this. It’s a similar situation for fly ash, also driven by trends to close coal-fired power stations in some countries. As Charles Zeynel of SCM trading firm ZAG International explained in the March 2019 issue of Global Cement Magazine, “...volcanic pozzolans are a potential SCM of the future. This is gaining traction, but it’s slow progress at the moment. This will be the answer for some users in some locations.”

The problem though is that natural pozzolans are down the list of preferred SCMs for their chemical properties after silica fume, GBFS and fly ash. The first is expensive but the latter two were traditionally cheap and easy to obtain if a cement or concrete producer had access to a source or a distribution network. Natural pozzolans are very much subject to variations in availability.

It’s no surprise then that Charah is promoting natural pozzolans in a Californian plant given that state’s environmental stance. It’s unclear where Charah is sourcing their pozzolan from but they are not the only company thinking about this in the US. Sunrise Resources, for example, is working on the environmental permits for a natural pozzolan mine near Tonopah in Nevada. As it described in its company presentation, California and Nevada are the most affected states in the fly ash supply crisis because they are, “...at the end of the line when it comes to rail deliveries from power stations in central and eastern USA.” It also estimated that California used 0.9Mt of pozzolan in its cement production of which about 90% is fly ash. The state produced 9.6Mt in 2015. Other companies are also mining and distributing natural pozzolans in the US as the website for the National Pozzolan Association (NPA) lists. Although, if this line-up is comprehensive, then the field is still fairly select. Most of these companies are based in the west of the country.

One last thing to consider is that various groups are tackling a potential future lack of SCMs for the cement industry by making their own pozzolanic materials through the use of calcined clay. These groups include the Swiss-government backed LC3 project and Cementir’s Futurecem products. Using clay should bypass the supply issues with natural pozzolans but the cost of calcining it requires at the very least an investment to get started.

As concrete enthusiasts often point out, a variant of pozzolanic concrete was used by the Romans to build many of their iconic structures, some of which survive to the present day. To give the last word to the NPA, “What is old is new again: natural pozzolan is back!” If environmental trends continue and steel and coal plants continue to be shut then it might just be right.

Spain: Endesa sold 0.3Mt of fly-ash from its Carboneras power plant in Almeria to cement companies in the UK and North America in 2018. The energy company also sold fly-ash to the nearby LafargeHolcim Carboneras cement plant, according to La Voz de Almería newspaper. The company has also sold 30,00t of slag and 60,000t of gypsum from its limestone plant.

Ukraine: Germany’s HeidelbergCement is selling its assets according to sources quoted by Interfax-Ukraine. It is reportedly selling to local investment group Concorde Capital and the deal will be completed during March and April 2019. The building materials local subsidiary, HeidelbergCement Ukraine, has not commented on story. The company operates integrated plants at Kryvyi Rih and Amvrosiyivka and a slag grinding plant at Kamyanske. Its loss rose by 14.4% year-on-year to around Euro14m in 2017.

France: Hoffmann Green Cement Technologies has inaugurated its pilot plant at Bournezeau, Vendée. The 50,000t/yr unit will manufacture cement products using metakaolin and blast-furnace slag, according to the L'Usine Nouvelle magazine. It says it will produce cement with reduced CO₂ emissions up to 250kg/t using a flash-calcined process down from 900kg/t in the normal clinker production process. The project had investment of Euro10m.

India: Jindal Steel & Power (JSP) plans to build a 2Mt/yr slag cement plant at Angul in Odisha. The US$68m unit will use ground granulated blast furnace slag sourced from a nearby steel plant operated by JSP, according to the Business Standard newspaper. A recent expansion at the steel plant to 6Mt/yr has allowed it to support a cement plant of this size. Land for the project has been acquired and the company hopes to obtain it from the state government by early 2019.

India: A joint-venture project involving the Steel Authority of India (SAIL) to build a new cement plant at Sundargarh in Odisha has stalled. Following support by local politicians for the plans in February 2017 no further action has been taken, according to the New Indian Express newspaper. SAIL originally made plans in 2006 to use blast furnace slag from the Rourkela Steel Plant and fly ash of NTPC-SAIL Power Company for the unit. It also intended pick up the lease for a limestone mine at Purunapani. However, it later ran into troubles securing state agreement to use the mine.

France: Hoffmann Green Cement Technologies’ pilot plant at Bournezeau, Vendée is set to start commercial production of low-carbon cement products in January 2019. Construction of the 50,000t/yr unit is due to be completed in October 2018 with its inauguration scheduled for late November 2018, according to Batiactu. The plant will employ 10 workers initially and this will rise to 15 – 20 as production ramps up.

The producer intends to make cement products using metakaolin and blast-furnace slag. If the pilot plant is a success it then intends to raise funds to build a 0.5Mt/yr plant.

Italy: Cemitaly has been allowed to use slag and ash in cement production at its Taranto plant following an investigation, according to the Il Fatto Quotidiano newspaper. The former Cementir unit was investigated in 2017 as part of an illegal waste probe that examined whether the Taranto plant purchased ‘illegal’ by-products from Enel and the ILVA steel plant to produce cement.

There is lots to mull over for the cement industry from last week’s Global Slag Conference that took place in Prague.

One striking map from Michael Connolly, TMS International, showed the status of slag and steel products in the US. It was a multi-coloured patchwork of different regulatory statuses from approval to be used as a product to regulatory exclusion. This won’t come as a surprise to many readers but even within one country the way slag can be used legally varies.

As this column reported last year after the Euroslag Conference, the European Union can be presented in a similar way. The irony here is that increased use of slag and other secondary cementitious materials (SCM) is exactly the kind of change the cement and concrete industries need to make to decrease their carbon emissions. Constant quibbles over whether slag is a product or a waste undermine this. Happily then that Connolly was able to report progress in the US as lobbying by industry and the US National Slag Association have led to more states legally accepting slag as a product.

However, cement producers have other concerns in addition to environmental ones when it comes to slag usage as Doug Haynes from Smithers Apex explained. Haynes, a former UK steel industry worker turned consultant, spoke around a market report on the future of ferrous slag. His take on Basic Oxygen Furnace (BOF) slag was that despite fuel savings, decreased CO₂ emissions and the benefits of embodied iron when it is used as a raw material for clinker production, it is in the interests of cement producers for slag to be a waste because they then get it for free or at a reduced rate. It’s a similar story to the use of waste-derived fuels powering cement plant kilns where producers want lower fuel costs but waste collectors want value for their product. Unsurprisingly, Haynes wanted cement producers to accept the value embodied in BOF slag.

Charles Zeynel of ZAG International, an SCM trader, then laid out the situation where global SCM supplies are remaining static but cement demand is growing. Coal-fired power station closures are reducing supplies of fly ash, another SCM, placing pressure on existing granulated blast furnace slag (GBS) slag supplies. The message was very much in a slag trader’s favour but instructive nethertheless. If slag is in demand then the price will rise. Anecdotally, the increased number of cement producers at the conference seemed to indicate increased interest of the cement industry in the product.

Lots more speakers followed on topics such as slag beneficiation, grinding advances and new innovations. On grinding, one surprise that popped up was that Spain’s Cemengal has sold a Plug & Grind Vertical mill to CRH Tarmac’s cement plant at Dunbar in Scotland. It is the first such sale of this product in Europe. The last speaker, Jürgen Haunstetter of the German Aerospace Centre, stuck out particularly with his presentation on using slag as a thermal energy storage medium in a concentrated solar power (CSP) plant. This may not seem connected to the cement industry but it is along similar lines to Italcementi’s project at the Aït Baha cement plant in Morocco, which uses a CSP process that can be used with the plant’s waste heat recovery unit.

The Global Slag Conference will return in April 2019 in Aachen, Germany.

Read the full review of the 13th Global Slag Conference 2018

India: Wonder Cement has ordered two vertical mills from Germany’s Gebr. Pfeiffer for its Nardana plant in Rajasthan. The order includes a MVR 6000 C-6 mill for grinding slag cement and a MPS 3070 BK mill for grinding fuel. Delivery is scheduled for early 2019 and mid-2019 respectively.

The MVR mill will feature a total drive power of 5820kW. Mixed cements will be be ground to a fineness of up to 5% R 45µm. The grinding plant will be designed to process granulated blast-furnace slag with a target fineness of approximately 4500 cm²/g Blaine and blast-furnace cements with different proportions of granulated blast-furnace slag, fly ash and gypsum and different product fineness degree. Wonder Cement has requested the option to grind relatively hot clinker in the mill while at the same time being able to reduce the cement temperature, and alternatively to use cold clinker from stockpiles.

The core components such as the tension system and the grinding rollers will come from Gebr. Pfeiffer in Germany. The grinding bowl and the gearboxes for the mill and classifier will also be delivered from Europe. Gebr. Pfeiffer’s subsidiary, Gebr. Pfeiffer India, will provide the housing parts, the foundation parts and supports of the rollers as well as almost the entire high-efficiency classifier type SLS 5600 BC. Gebr. Pfeiffer India scope of supply will incorporate most of the equipment to complete the grinding plant including the plant fan.

The MPS mill will grind petcoke with a capacity of 40t/hr to a product fineness of 2% R 90µm. It will come with a SLS BK classifier, allowing both coal and petcoke to be ground in the mill, dried with process gases and then classified in the integrated classifier. Due to the high abrasiveness of Indian coal, the mill will be designed with appropriate wear protection.

Most components of the coal mill will be supplied by Gebr. Pfeiffer India. The housing and foundation parts, the grinding bowl and a large part of the power-transmitting parts will be manufactured in India. Setting up the new MPS mill is planned to coincide with the commissioning of the entire kin line.