One of the products the shaft kiln calcination plant in Sasolburg produces is PROCARB SG, a carbon raiser used in the steel industry and by ductile and grey iron foundries. The innovative plant is the first of its kind to be erected in this country and in fact the first plant to be erected outside of China by the Chinese process engineering company, SAMI.

Due to a joint study with the Foundry Institute of the University in Freiberg/Germany and field trials in European and Far Eastern foundries, UK-based the Durrans Group decided to commission a calcination plant in Sasolburg in the province of the Free State, five years ago.

The project was assigned to Durrans Group company Carbon International Limited, a UK-headquartered supplier of carbon-based products to the world’s manufacturing industries. Carbon International Limited processes and manufactures high purity and granular carbonaceous materials. It offers medium sulphur and low sulphur carburisers, metallurgical coke, machined graphite and slag coagulant. The company was incorporated in 1991 and is based in Bilston, United Kingdom. Carbon International Limited operates as a subsidiary of James Durrans and Sons Limited.

The Durrans Group purchases green coke from Sasol Secunda refinery and calcined the product in China. The Group approached Sasol with the view to beneficiating the product in South Africa for the obvious reason of eliminating the extended logistics and process costs.

The construction of the calcination plant in the ChemCity industrial complex began once the company had obtained all the study findings and complied with the regulatory requirements. Permission was then given for Carbon International to proceed with construction of the plant by DESTEA in April 2017. The civil construction phase began in December 2017 and the fabricators commenced erection of the plant in May 2018. The company began producing product in 2019.

The initial stages of the project was project managed by Durrans RMS (a joint venture between the Durrans Group and Resistant Materials Services (Pty) Ltd) personnel to assist in procurement, administration and financial control of the project.

In his address to guests who attended the 5 year anniversary function held at the plant in Sasolburg Chris Durrans, Managing Director of Sheffield, UK-headquatered James Durrans & Sons Limited made particular mention of Kevin Nesbitt and Mike Robinson, Directors of Resistant Materials Services and Durrans RMS. “They had to do some lengthy and demanding engineering research and make challenging decisions on the site where the plant has been built and also on the construction of the plant. I can’t thank them enough. Without them we might not be standing here today.”

The calcination plant
The main components of a calcination plant include a green coke delivery and storage area, a vertical shaft kiln/calciner, a calcined coke storage-silo, calcined coke crushing, screening and bagging facility and a storage area for the products of the calcination process.

Carbon International successfully operates the 16-Shaft, Vertical Shaft Calciner to produce a variety of high-quality calcined petroleum and pitch cokes. The vertical shaft calciner or kiln, often referred to as a “VSK”, has a calcined coke capacity of approximately 15 000 metric tons per annum.

State-of-the-art laboratory
Last year Carbon International commissioned and built a state-of-the-art laboratory at their facilities to ensure that their product always remains in the customer requested specifications.

The laboratory can carry out a range of tests, such as, but not limited to, ash and volatile matter making use of muffle furnaces, moisture with an oven, sulphur and nitrogen with equipment and particle size distribution using a mechanical sieve shaker. There is also a laboratory scale crusher which brings the material into the correct size specification for the respective tests.

The laboratory is built on land purchased that is adjacent to the existing facility.

“It is the only VSK of its kind in Africa, and outside of China it is one of only a few VSK’s in the world. Calcining coke in a VSK is truly unique and boasts many environmental, commercial, as well as product benefits,” explains Stefan Pfeffer, a Carbon International Trading (Pty) Ltd Director.

“The plant is extremely energy efficient and self-sustaining, requiring no external sources of energy, such as electricity or gas to provide the required thermal input. Furthermore, the indirect heating of the green coke material removes the potential of finer material burning away, thus improving product yield and minimising the calcining losses. In addition to not combusting the fines, the fines also agglomerate in the VSK, further increasing the overall yield of calcined coke and of coarser grading compared to the green coke feed.”

“Carbon International has the ability to produce customised raw material blends to meet chemical and physical calcined coke properties required by a diverse spectrum of industries. Green coke material is received on site in bulk by means of a tipper truck. The material is fed into the process manually using a front-end loader. From there the material is transferred into the VSK shaft hoppers automatically via a charge car.”

“Once the green coke enters the material channels it is exposed to an indirect heat at calcining temperatures and begins to release its inherent moisture and volatile matter. The volatile matter is captured and introduced into an air rich environment, where it spontaneously combusts. The flow of air, volatile matter and flue gas is carefully controlled and the combustion channels of the VSK are constantly kept under a slight negative pressure.”

“Although the process is completely automated, it is controlled by a skilled and experienced furnace operator. The operator has the ability to manually operate the VSK in upset or in emergency conditions.”

“Prior to being cooled down and discharged from the VSK into a common hopper, the material will have undergone a fifty-two-hour indirect heat soak.”

“Once the material exits the VSK it can be sold directly as a run-of-kiln product, alternatively, further value can be added in our crushing, grading and packaging plant. In this facility Carbon International has the ability to produce a range of customer requested gradings, in a variety of packaging configurations. The packaged material is taken by road truck to the end user directly or to the nearest seaport for export.”

The state-of-the-art laboratory can carry out a range of tests, such as, but not limited to, ash and volatile matter making use of muffle furnaces, moisture with an oven, sulphur and nitrogen with equipment and particle size distribution using a mechanical sieve shaker. There is also a laboratory scale crusher which brings the material into the correct size specification for the respective tests. The laboratory is built on land purchased that is adjacent to the existing facility

“Carbon International is ISO9001:2015 certified and has a rigorous quality management system. We adhere to stringent health and safety protocols on all operations and are fully compliant with the Occupational Health and Safety act, as well as global safety standards. Carbon International prides itself in providing a safe and comfortable workspace environment, as well as being an employer of choice; we truly value our employees.”

“Furthermore, we pride ourselves in creating a sustainable operation, through making a positive impact on the surrounding community, being more energy efficient, producing less waste, as well as reducing the company’s carbon footprint. The operation currently produces no process waste and a large portion of the electricity consumed by the facility is produced from our own PV Solar Plant.”

For further details contact Carbon International Limited on TEL: 016 100 5255 or email info@cit-za.com or visit www.durransgroup.com