The 61st Annual IEEE-IAS/PCA Cement Industry Technical Conference and Exhibition took place in St Louis, Missouri, USA, on 28 April-2 May 2019. Under the theme of ‘Sustainable strength through innovation,’ the meeting attracted more than 900 industry specialists. Among the many highlights was an update of the status of the US cement industry, a panel session on experiences with large-capacity clinker coolers and a field visit to one of the world’s biggest single-kiln clinker production lines.

The IEEE-IAS/PCA Cement Industry Technical Conference and Exhibition returned

to St Louis, Missouri, USA, for technical discussions under the iconic Gateway Arch

Chris Macey, of Resco Products and IEEE-IAS Cement Industrial Committee  (CIC) chair, opened the 2019 IEEE-IAS/PCA Cement Industry Technical Conference by underlining that: “Cement is our future and the cement sector has to be ready for the challenges of tomorrow.” Setting the scene for the technical programme, he added: “It is the industry’s goal to forge ideas and concepts to reduce costs, increase competition and better understand the market while improving sustainability.”

During her welcome address, Corinne Fields, of Refratechnik and Conference Organising Committee chair, noted that much had happened in the cement sector since the technical conference was last held in St Louis eight years ago. Ms Fields was particularly encouraged to witness a new generation of industry professionals at the conference, bringing fresh ideas and perspectives – a point underscored by more than 300 first-time attendees.

Keynote presentation

CIC Vice Chair, Nathan Murphy, introduced keynote speaker LeRoy Stromberg, chief construction officer and COO of Alberici Construction Group. Founded in St Louis in 1918, the diversified company has a revenue of more than US$2bn and today ranks as the 37th largest construction firm in the USA.

Keynote speaker LeRoy Stromberg,

chief construction officer and COO of

St Louis-headquartered Alberici Construction Group

Alberici has worked with the cement sector for most of its history and over the past decade completed some of Missouri’s major industry projects, including LafargeHolcim’s Ste Genevieve plant and Buzzi Unicem’s Festus works. During his address, Mr Stromberg spoke about best practice and improvements in safety. In particular, he discussed ProCore project management, a software system used by Alberici so that engineers can tell exactly what is required on the ground where they have access to 3D models, architectural plans, stakeholder concerns, etc.

US industry update

In his traditional industry review, Ed Sullivan, chief economist and senior vice president of Market Intelligence for the PCA, looked back to 2017 and the many reforms that were put on the table when President Trump took office. Mr Sullivan stated that these reforms hyped up the economy and aggregated inflationary spirits, forcing interest rates up. While tax cuts have stimulated the economy somewhat, the US is still awaiting the infrastructure bill and therefore, some stimulus is yet to materialise.

Mr Sullivan also noted that new analysis suggests that the US economy will be much more placid than predicted two years ago. While continued, sustained growth is expected, it will be “gradual and modest.”

Key economic statistics include monthly job numbers, as the labour market reflects the strength of the economy and the performance of the construction sector. In the Great Recession 8.6m jobs were lost, but since then some 19.5m have been generated at a net rate of 235,000/month. In the next two years, a further 2m are forecast to be created.

In addition, some 70 per cent of the economy is tied to consumer spending and increasing willingness of consumers to spend has provided a positive impact on the economy. However, interest rates continue to rise, and their peak level and timing remain uncertain, putting a dampening effect on spending. Mr Sullivan suggested interest rates are likely to hit an apex in 2021 – at around the same time the supplemental infrastructure initiative is expected to materialise. While the PCA expects near-term cement to grow by 2.3 per cent, roughly the same pace as in 2018, the slowing economy will result in demand cooling further down the line. Per capita consumption is predicted to gradually rise as income grows, but the advance will be at a lower rate than in the past, given an ageing population with lower spending potential. 

The event featured many networking opportunities to meet industry colleagues and make new connections

The 10,000tpd clinker cooler panel

The General Practices Working Group featured a special session on experiences with large-capacity clinker coolers, where the key features and performance drivers of six different technologies were discussed by leading suppliers.

FLSmidth
Steven Miller of FLSmidth clarified the specific factors that large coolers require to be taken into account: fixed inlet design, dust recirculation, tertiary air take-off design and waste heat recovery.

The traditional fixed inlet design of lanes is not large enough for a 10,000tpd cooler. The area loading on a tpd/m2 basis is too high and the clinker cooling rate from the fixed inlet to the rest of the cooler is insufficient. Therefore, FLSmidth has modified the fixed inlet to have 10 rows.

At the drop zone, where clinker temperature is at its highest, the air must penetrate the area rather than bypass it. To ensure this type of constant air flow, FLSmidth has equipped the drop zone with a dedicated fan. In addition, snowman formation is prevented by a patented ABCTM cooler inlet that blasts air at a 100 per cent through the drop zone.

Large coolers can present issues such as dust recirculation back into the kiln and precalciner, but vents and a suitable over-grate velocity can prevent this, according to the equipment supplier.

In terms of tertiary take-off, a 10,000tpd cooler requires two take-offs – typically placed on either side of the ‘rabbit ear’ of the hood or the sides of the coolers. The cooler design is modified to move the hydraulic cylinders in the under-grate area to other locations to recirculate air at the highest temperature, approximately 130˚C continuously or 150˚C spikes.

Furthermore, in countries, such as those in Asia, where power costs are high and electricity supply is less reliable, waste heat recovery (WHR) is often used to ensure a more economical and reliable power supply. In these cases, a linear mid-air take-off will enable the operators to achieve the highest temperature possible while recirculating 100 per cent of the vent air.

IKN
Klaas Windmöller of IKN explained some of the modifications made by the company for its larger coolers. For a large 10,000tpd cooler, IKN’s Clinker Inlet Distribution System (kids®) section is 7.8m wide x 10 rows long. The cooler grate is supported by Linear Pendulum Support (LPS®) and is driven by four hydraulic cylinders. Clinker is distributed evenly by the kids onto the single grate. “IKN have dropped the idea of single-lane movement, as there is no need for this complication once the kids has been adjusted the right way,” said Mr Windmöller.

Moreover, as a safety device, the Tube Dust Extractor (TDE) keeps the confined space underneath the grate clean and the roll crusher is positioned at the end.

thyssenkrupp Industrial Solutions
Dr Uwe Maas of thyssenkrupp Industrial Solutions started by looking at what customers require from large clinker coolers. The major goals include a smooth operation, achieving the highest-possible production and being able to adapt to future operating conditions. A further key requirement is keeping maintenance costs low, in which not only technology but also operation plays a key role.

Therefore, the design must be sufficiently robust to enable easy adaptation to a range of operating conditions such as changes in temperature and grate locks, as well as changes in demand. More specifically, this also applies to the static grate and starts with a horseshoe shape at the clinker discharge. “We want 50 per cent of the width and this is gradually widened to the end of the cooler, allowing for better clinker distribution and countermeasures against snowmen formation,” said Mr Maas. Furthermore, there is no step between the static and moveable grate. The section is used as an arresting zone to prevent the static grate from running empty. This flexibility enables the cooler to adapt to a range of operational conditions.

Fons Technology International
Mogens Fons, owner of Fons International Technology, looked at the technical issues of achieving an efficient heat exchange in the cooler. “Normally, at the cooler we want to take off as high a temperature as possible to save fuel, but we must have enough air to cool the clinker,” he said.

Therefore, a uniform air flow is key to achieving an efficient heat exchange. “Air is lazy, it takes the path of least resistance,” said Mr Fons. To optimise air flow, the manufacturer includes a flow regulator for every grate plate and fixed inlet. If there is an easier path for the air, the regulator closes it to keep the air flow constant. This eliminates the need for the splitting of compartments by different fans, a concept used by some cooler suppliers.

KHD Humboldt Wedag
Andres Hand of KHD Humboldt Wedag explained that projects for large coolers start with specific requirements, which lead to corresponding design criteria such as a 12,500tpd capacity, a specific clinker size particle distribution, a clinker inlet temperature of 1450˚C or a clinker outlet temperature of 60˚C.

For example, the clinker inlet for KHD coolers is dimensioned at 4-4.5m/s for the transition area between kiln hood and cooler. In these cases, a larger cooler inlet section mitigates the effect of petcoke and alternative fuels, which can lead to high dust levels. In addition, large coolers should have a clinker bed velocity between 5-6m/s, according to KHD’s experience.

The KHD cooler’s high 12,500tpd capacity is ensured by two grate stages with a combined cooling area of nearly 320m2 (aerated area: 308m2) and an intermediate crusher. The first static grate covers an area of 31m2 and includes a horseshoe design, which is followed by 12 parallel moving lanes, an intermediate crusher consisting of six rollers (two crushing rollers and four are used for the transport). The cooler’s second stage starts with a second static grate and then another 12 parallel lanes.

The moving grate floor consists of several lanes, which are arranged parallel to the direction of the clinker transport.

Claudius Peters
Andre Vos of Claudius Peters highlighted the installation of a 12,500tpd ETA cooler in China, focussing on the principle of the moving floor and some of the benefits of the larger-capacity cooler. The 6m-wide lanes of the cooler are supported on rollers and driven by hydraulic cylinders. The current system can be extended from five to 12 lanes. Furthermore, this type of cooler operates with a high clinker bed (0.95-1.2m) where the air has more time to pick up the heat, enabling the plant to use less air and reduce fuel costs.

In addition, the cooler’s aeration system includes a longer static inlet – 13 rows for a typical 12,500tpd cooler.

The Chinese installation also includes an intermediate crusher, which cracks open bigger lumps of clinker to access the heat contained within and use it in the plant’s WHR system.

Site visit to LafargeHolcim’s Ste Genevieve cement plant

Delegates attending this year’s event were able to tour LafargeHolcim’s Ste Genevieve cement plant, which has one of the world’s largest-capacity single-kiln lines. Since 2011, when the IEEE conference was last held in St Louis, clinker production has been 12,000tpd (4Mta of cement). Ahead of this year’s visit, John Goetz, general manager of the Ste Genevieve plant, provided an overview of operations and recent achievements at the Missouri-based works, which employs 225 staff.

Among the site’s capabilities, it has some of the largest slipform silos ever built. The quarry has a 2600tph Fuller-Taylor gyratory primary crusher from which material is conveyed to a secondary crusher. The limestone dome has a stacker/reclaimer with a capacity of 65,000t, or three days of supply. There is a 60,000t raw material storage hall, with one stacker for the entire 350m-long building. The two identical Atox 50 VRMs for raw milling can produce over 500tph.

However, the focal point of the plant is the ⌀6.6m x 93m three-support kiln, which is preceded by a dual-string preheater tower. The ⌀10m calciner is currently burning coal in combination with petcoke and a small amount of liquid alternative fuels. To prepare the fuel, the petcoke and coal are ground by identical VRMs, both with 740kW drives. Petcoke is ground at 37tph at 45ACI and coal at ~70tpa. The prepared fuel is then sent to one of three bins, where it is fed to the calciner and primary kiln burner as required.

At the end of the pyroprocessing section, the 13,500tpd IKN cooler, installed in 2017, has a width of 7.8m and 119 rows in length (300m2 or 45t/m2 surface area). To store clinker, there are three 9000t silos and one 10,000t silo.

Finish grinding is carried out by four VRMs, which are rated at 165tph at 3800 Blaine. The mills have already completed 80-90,000h of service and therefore, will be due for maintenance soon. Cement storage capacity is 2660t with eight main silos and two silos at the plant’s 42-acre slack water harbour.

In terms of quality control, a fully-automated lab features two crossbelt analysers and 10 auto-field analysers. The first crossbelt analyser is located in the quarry to monitor potassium and calcium levels, while the second is on the raw mill feed and controls all the clays.

St Genevieve’s harbour has two unloading stations, one system unloads dry fly ash while the hydraulic crane unloads coal, gypsum and iron ore. A 750tph barge loading system enables the loading of 18,000tpd of material onto 132 barges. The harbour can also load rail carriages with up to 20,000tpd of product.

The cement works was built for low NOx and CO2 emissions with selective non-catalytic reduction (SNCR) dry line injection and NOx control. There are two main transformers in the substation, but one can power the entire facility, while incoming power is supplied by the grid.

With safety a core concern, the plant has surpassed three years without  lost-time injuries and will reach 2m man-hours in July. Electrical energy consumption has also reduced every year and is down to 87kW/t. Moreover, LafargeHolcim has 176 plants which the company rates. In 2018 the Ste Genevieve plant came top, scoring 99 out of 100 per cent.

Winning presentations

The winning presentation at this year’s Technical Conference, ‘A cement mill upgrade story reboot’, was part of the automation session. Presented by Alan Simmons, chief electrical engineer of CalPortland Cement, Gurjeet Sarao, Mojave plant engineer, and David Campain, FLSmidth product line manager, it highlighted the Mojave plant project to upgrade the vertical roller mill (VRM) circuit, improving mill stability and reducing energy consumption for the entire circuit.

In 2017 Mojave Cement initiated the project to replace the separator and install advanced process control (APC) software to improve efficiency. This included optimising the dimensions of the separator, including the housing diameter, static guide vane opening and rotor surface to better convey and distribute material with a high-velocity gas stream or low-velocity deadspots. Therefore, the mechanical portion of the upgrade required a new separator, but as the airflow remained unchanged, the existing mill fan was reused. A new 600hp gear unit was ordered to reduce the rotor speed. The outlet duct would also be modified for the larger separator dimensions.

A performance guarantee of 1.5kWh/st power savings at the same fineness (Blaine at 423m2/kg) and a grinding capacity of 156stph were guaranteed. The separator motor accounts for 50-55 per cent of the power savings with the fan contributing 35 per cent and the mill motor 15 per cent of total savings. Particle size distribution was also improved. The 325 mesh residue decreased from 2-3 per cent to consistently below one per cent, which meant a potential five per cent increase in cement strength.

FLSmidth then supplied its APC system  to connect with the plant’s Ethernet and communicate with the plant control system to read data input and setpoint changes. Secure remote access capability allows for remote viewing of system performance and remote engineering support by FLSmidth.

In second place was a power generation presentation – ‘Vintage low-voltage motor control centers – replace or upgrade?’ by David Durocher and Matthew Hussey of Eaton Corp. The paper discussed the need for some cement producers to upgrade low-voltage motor control centres and the alternatives, addressing the UL 845 North American industry standard requirements as well as giving a case study on a motor control centre replacement and upgrade project.

The third-placed presentation came from the maintenance and safety session and looked at ‘Improving coal mill fuel delivery through upgrades to the feed valve’. It was presented by Stephen Tyrell, maintenance manager at Mitsubishi Cement Corp, and Kevin Guay, Plattco Corp new product development manager. The paper reported on a project to replace a hydraulically-operated triple-gate valve with a pneumatically-operated double-gate valve for the inlet feed airlock for a coal mill. As a result of the project, efficiency savings of US$3500 per year were calculated.

The complete IEEE experience

As part of the extensive programme, delegates were able to participate in process training, professional development courses and tour the LafargeHolcim Ste Genevieve cement works (see box story). An exhibit hall with 160 stands displayed all the latest in product and service offerings to the cement industry, while delegates were invited to an Award Banquet to complete their IEEE-IAS/PCA experience.

 An exhibition hall with 160 booths displayed the latest product and service offerings to the cement industry

The 62nd IEEE-IAS/PCA Cement Industry Technical Conference and Exhibition will be held in Las Vegas, Nevada, USA, on 19-23 April 2020.

This article was first published in International Cement Review in July 2019.