April 2023

Supporting CO₂ reduction strategies

Daniele Sciuto, Euromecc s.r.l.,
describes the design process of a new facility for receiving, storing, dosing, and conveying granular calcined clay to support production at one of the world’s oldest cement factories.

Aalborg Portland (AP) in Denmark is the world’s oldest cement factory still in operation with more than 130 years of activity, since being founded in 1889. It remains one of the largest plants in Europe with 4 kilns and an annual cement production capacity of approximately 2.5 million t. Located near the city of Aalborg, in the Nordjylland Region, it is the largest industrial enterprise in the region, employing hundreds of people in the company itself and at local sub-suppliers. In 2004 Aalborg Portland, together with Unicon A/S, were acquired by the Cementir Group.

Aalborg Portland committed to a sustainability strategy aiming to reduce its annual fossil CO₂ emissions to 600 000 t by 2030. Three main levers are pursued to accomplish this:

– Transition to new composite cement types (FutureCEM) with reduced clinker contents.

– Fuel switching from fossil coals to biogenic fuels.

– Implementation of carbon capture, and storage (CCS).

Euromecc has joined Aalborg Portland’s green roadmap for FutureCEM^® with an EPC contract for the supply of a complete solution for receiving, storage, dosing, and conveying calcined clay.

The feasibility phase
Walking through the architecture of Aalborg Portland A/S, people are fascinated by the mixture of ancient buildings, green spaces, and cutting-edge equipment.

Calcined clay emerged as a new supplementary cementitious material at the Aalborg Portland cement plant in 2021 when the new cement type FutureCEM was introduced. Initially, the calcined clay was sourced from an external supplier, where it was produced in rotary kilns. This material has a granular nature; hence it is referred to as granular calcined clay (GCC). In the longer term, as production volumes increase, AP may insource the production of calcined clay – in which case the material characteristics would most likely change from granular to a powder.

Once the material data sheet was clear, Euromecc became involved in supporting the customer with its experience in the bulk materials storage and handling industry.

The initial requirement was for 10 000 t of storage capacity for calcined clay to be built in two steps with two identical silos of 5000 t. Looking at the site and the viability of its layout, a potential location for the new facility was identified close to the road fence. This location required few modifications, considering that clay is delivered by lorries.

However, the main challenge to this solution was related to the pneumatic transport of granular materials from silos to mills, which according to some suppliers required the provision of a crusher to make the material suitable for use. From the very first day, this proposal appeared to be both complex and expensive, with several pieces of equipment involved, such as crushers, elevators, screens, pumps, cyclones, and filters.
With this in mind, the possibility of having a crusher for a limited period of operations appeared to be suboptimal.

Following internal review in Aalborg Portland, the scope of the calcined clay storage system was revised to two smaller silos with 3000 t capacities and a mechanical conveyor belt transport system to the cement mills.

The solution
All preliminary aspects were evaluated over a six month discussion, which led to consider another location for the silos as well as a different means of transportation.

A suitable new location was identified, nearly 80 m south of the previous one, closer to the two cement mills, thus facilitating mechanical transportation system.

For the new location a concept was then developed comprising two steel silos with capacities of 3000 t each, to be installed in two stages, with stage 2 being optional:

– Silo 1 is to be installed towards the first step, with a simple, straight 100 m long conveyor belt.

– Silo 2, which may come at a later stage, will be installed with a double curved pipe conveyor and a short drag chain.

Both silos are designed to accommodate a retrofit aeration system on the silo bottom cone for future conversion, making them suitable for initial operation with a variety of materials. Once the configuration was agreed, the technical discussions focused on the surroundings: Operations, environment, layout viability and so on.

The Euromecc proposal developed the mandatory requirements to design a surface feeder, which is expected to empty up to 6 trucks per hour (capacity 250 tph), sending the material to a belt bucket elevator which feeds the silo. The material is then emptied via gravity onto an extremely accurate dosing belt able to regulate the flow before it goes with a group of conveyors into an existing drag chain. The full proposal was designed with a major focus on dust and noise emissions, in order to comply with regulations and minimise the environmental impact, introducing insulated cladding and closing all the transfer points.

After being awarded the project, it was time to develop the proposal and explore any particular details. The Euromecc team worked very closely with their Aalborg Portland counterparts in order to deepen every aspect of daily operations, access and maintenance routines, truck access, interferences, best practices, and standards.

For instance, it was found that the initial proposal for the receiving station was oversized, so it was replaced with a more compact design in order to avoid hindering truck traffic on nearby busy roads as well as keeping standard maintenance operations feasible without requiring a major operation. Once every technical detail was finalised, both AP and Euromecc teams focused on the complex itself, exploring a finish which would merge with its surroundings and make the installation visually unobtrusive. A suitable colour palette was found for each piece of equipment, starting with a chequered pattern on the silo body, made up of different shades of blue and white.

Starting site
After several months spent in design activities, to develop the project under every aspect (civil, mechanical, electrical, and so on), on 16 November 2022, the Euromecc team began work on the site. The final layout consists of a large main concrete slab to support the silo, including a staircase and bucket elevator, plus a second slab for the feeder with its ramp, and seven small concrete bases to support the main conveyor. Despite the challenging weather conditions and reduced daylight hours, it took less than 11 weeks for the Euromecc site team to carry out all the excavation, ground stabilisation, steel formworks, and casting of civils. Everything went smoothly and was overseen by local contractors to regularly inspect the quality of the work’s execution, in compliance with the Danish building regulations.

The first phase involved approximately 400 m3 of concrete with different classes and slumps, and was completed right before New Year’s Eve.

After that, early in January, the team went back to Aalborg to finalise the details and curbs, paving most of the area and finalising the grouting before the first set of deliveries reached the site.

Due to the rather limited construction site area, as well as the ongoing operations of the surrounding cement plant, the whole design and manufacturing processes has been performed to facilitate the installation. Therefore, the first component to be shipped was the main loading conveyor, expected to be put in position by mid-February together with the steel legs of the silos, in order to allow the tailored-engineering of interface connections to the existing drag chain conveyor.

Conclusion
This project is going to represent a key milestone in Aalborg Portland’s green roadmap. At the time of writing this article, the first civil construction phase was just completed, and the next phase of assembly is about to start. The main belt is being assembled together with the silo substructure, while the following phases will be executed over next couple of months.

View the full article