Ecocem opened its Dunkirk slag grinding plant in 2018. Global Cement visited before the coronavirus shutdown to see the plant and speak with its manager Anne Debenath...
Global Cement (GC): Can you introduce the plant?
Anne Debenath (AD): The Dunkirk plant was established by Ecocem France, a joint-venture between Ecocem, based in Ireland, and ArcelorMittal (AM), It was conceived after the success of its sister plant in Fos-sur-Mer in the south of France, which celebrated its 10th Anniversary in late 2019. Construction began in the Port of Dunkirk in 2016. I began my role as plant manager in September 2017 and was the first person on site!
GC: How was the commissioning process?
AD: Any plant commissioning is always a huge undertaking and is dependent on a lot of people with different specialities. From September 2017 to January 2018, I hired staff to run production, logistics and the laboratory. It was too early for most of the staff to come to work here, so they were trained at the Fos-sur-Mer plant for a minimum of three months. There they learned their craft so that they all knew their role ‘inside out’ by the time we started production. This was particularly important for this site, as we recruited people from a wide range of backgrounds. Most had never seen a vertical roller mill before.
Once training was completed we could start up parts of the plant. This involved people from Ecocem in Ireland, from AM, Loesche, other suppliers and more. The plant was fully commissioned on 2 May 2018.
After commissioning, one of the shift operators from Fos-sur-Mer came to Dunkirk for several months to help bed in the plant and further train our workforce once the plant was up-and-running.
GC: What was the biggest commissioning issue?
AD: We had no big issues, just a few surprises. The worst time was Christmas 2017 when we hadn’t been able to install the roof due to high winds. It snowed on the mill and water got into some of the electronics. Some parts were damaged but we were very careful to check each component, repair and/or replace, and then continue with commissioning afterwards.
GC: What is the plant’s production process?
AD: The Dunkirk plant is Ecocem’s most recent project and as such is the most advanced in the group. It is very similar to the Fos-sur-Mer plant, albeit with some improvements. Both of these have vertical roller mills, unlike the Dublin (Ireland) and Moerdijk (Netherlands) plants, which have ball mills. Slag is sourced from two of AM’s three blast furnaces at its Dunkirk steel works, which is around 500m away. Every morning I receive the chemical analysis of the slag and we ‘order’ what we need. It comes to the site via truck and we mix it using a front-end loader in our open-air yard. The front-end loader feeds an 80t hopper. This is a very important job, not only for consistent chemical composition but for constant moisture. The slag arrives with 8% moisture but, over time, it becomes wetter at the bottom. This helps the mill to operate smoothly. We keep track using a moisture sensor to ensure a constant 8% moisture level in the feed material.
From the hopper, the slag is conveyed to the top of a 100t/hr Loesche vertical roller mill, with a 4.6m table diameter and a 3.1MW drive. It has two main rollers and two auxiliary rollers. I would say that it is the best available technology for slag grinding. On the way it passes a cross-belt analyser and magnet array to remove any remaining ferrous material. There’s a weighfeeder to regulate the mill feed. The mill grinds the slag to around 4300 - 4500g/cm3 (Blaine).
To dry the slag while grinding, we need hot air, which is present in the mill at around 200°C. This is supplied by a burner from Loesche. The fuel is predominantly blast furnace gas, a byproduct from the blast furnaces that is high in carbon monoxide (CO). The use of this fuel is facilitated by a dual fuel burner, which is unique to Dunkirk within the Ecocem group. Dunkirk only uses natural gas for start up, which takes only a few minutes. This is great because we can use two by-products from AM, the slag and the gas. After the classifier, there is a big bag filter from Scheuch. Some of the hot air from the bag filter can be fed back to the mill, depending on what is required.
Slag is then transported up by Aumund bucket elevator to two IBAU Hamburg storage silos (one concrete and one steel) with a total capacity of 11,000t. There are then two options. We can dispense slag directly to silo trucks or vessels or divert it to the blending building. In this facility, we mix the slag with CEM I and other ingredients to produce CEM III and other binders that contain high levels of slag.
GC: When you look at the data from AM in the morning, what are the most important factors?
AD: I look at chemical properties, predominantly the basicity index, i.e. the main element ratios (aluminium, silicon, magnesium, calciumium) and the titanium content. It is not that physical parameters are unimportant, but rather we know from experience that AM’s granulated slag is >99% amorphous, the form required for slag to be an hydraulic binder.
GC: Is the plant operating at full speed?
AD: We had a really quick start-up, which was fantastic. In 2019, our first full year, we processed 0.55Mt. In the early part of 2020 we turned the plant up to maximum speed and had planned to produce 0.7Mt before the onset of the coronavirus outbreak. We have a weekly maintenance programme but this is just for checks, small tasks, lubrication and so on. All maintenance work is carried out by our 12 operators. There is no separate maintenance team, so the operators really know the machinery that they are using. We made a lot of tweaks at the start but are now in a stable place after a couple of very busy years. It is nice to have reached this point.
GC: What products were made in 2019?
AD: The vast bulk of our output was pure slag, with a minority of CEM III products. The slag has an embodied CO2 emissions in the region of 20kg/t, around 30 - 40 times less than a traditional cement-based binder. This is a major advantage for Ecocem, particularly in northern Europe as environmental awareness rises. It is the right time to come to market with this kind of product, especially with major works like the Grand Paris infrastucture improvements in Paris.
GC: What markets are supplied?
AD: As mentioned earlier, this plant is ideally located to serve the north of France, as well as some areas in the west of Belgium. In 2019 around 40% of our product left in trucks, with more than half of the trucks heading to Paris. Around 60% of our product was sent out in vessels, either directly to customers in and around the North Sea or to Ecocem terminals in Runcorn (UK), Sheerness (UK) and Gavle (Sweden). Marine dispatch is carried out by Dunkirk Multibulk Terminal (DMT), which loads vessels from an adjacent wharf.
GC: Have you noticed any changes in dispatch patterns since the UK left the EU on 31 January 2020?
AD: We have not seen any changes in the routes so far. Even if the UK Transition Period ends in a ‘crash-out’ I don’t think the civil works in London will stop!
GC: Are there any plans to increase capacity at Dunkirk? There’s certainly a lot of space available...
AD: From the outset Ecocem planned two lines to operate at the Dunkirk site. Now that the first is well established in a strong and growing market, I think it will be only a matter of time before work commences on the second line. I look forward to this development, whenever it may transpire.
GC: Thank you for your time today Anne.
AD: You are very welcome indeed.
Plant profile
Location | Dunkirk, Northern France |
Main market | Paris / N France / N Sea |
Construction | Late 2016 - September 2017 |
First product | 2 May 2018 |
Capacity | 0.7Mt/yr |
Fuels | Blast furnace gas |
Natural gas (start-up) | |
Staff | Operators = 12 (6 teams of 2) |
Laboratory = 4 | |
Plant Manager & Deputy = 2 | |
Logistics, Sales & Administration = 7 | |
Total = 25 |