Babcock has kept the Sappi Ngodwana Paper and Packaging Mill steaming ahead thanks to their ability to provide a swift and well-engineered solution for an application that saw two previous attempts fail. Equally noteworthy is the rapid pace at which Babcock achieved this, successfully delivering the project three months earlier than initially proposed.

The project required the replacement of an existing 1 100 kPa desuperheater in the steam plant at Sappi Ngodwana, a vital component in the production capacity of the plant as the majority of the mill processes requiring steam cannot operate if the desuperheater system is faulty or shut down. The desuperheater is a system that is used to reduce the temperature of superheated steam by injecting water into it. The water injection is controlled to reduce the steam temperature within close proximity of the saturation temperature of the steam. The two main reasons for lowering the steam temperatures are: (1) to permit operation of downstream process equipment that is designed for lower temperatures, and (2) to maintain a constant temperature for processes that require precise temperature control.

Babcock’s Project and System Engineering Manager, Etienne Wannenburg, explains that when Babcock submitted their proposal the current system was unreliable and not operating as required and that two previous attempts by other organisations to replace the desuperheater were unsuccessful.

“The client required a reliable, high performing system that included an accurate steam temperature control within a 10˚C range with a high turndown and quick response time. Furthermore, it could only allow for maintenance once a year, and we had the added challenge of completing the installation within 11 days,” says Wannenburg.

Despite the severely constricted time frame to commission the project, Babcock swiftly responded to the tightly scheduled brief and delivered an engineered solution not only within the specified time constraints, but which also exceeded the client’s expectations. “During our first proposal we put forward a period of eight months to design and supply the equipment. A delay in the placement of the order constricted our time frame; nevertheless, we were able to reduce the engineering and supply duration to five months through resource management, engaging with our suppliers and working through the year-end holiday period,” explains Wannenburg.

He says factors attributing to Babcock’s rapid turn-around time included:

• The design of the system – aided by Babcock’s in-house 3D scanning and modelling capacity to deliver accurate results;
• Ensuring that all the interfacing systems were properly defined and investigated during the design phase;
• Efficient interaction between Babcock and their equipment suppliers to ensure correct equipment selection and reduce the delivery period; and
• Effective design plans allowing for proficient and swift installation.

Wannenburg adds that during commissioning, it was established that the performance of the system exceeded their client’s requirements and that Babcock was able to deliver a system that effectively controlled the steam temperature throughout the required range.

More than a year later, the desuperheater system continues to operate without any failures, proving its reliability and attesting to Babcock’s proficient engineering skills. Babcock also continues to assist Sappi Ngodwana with general maintenance of the annual boiler shutdown.

Two years ago the Sappi Ngodwana Mill in Mpumalanga was expanded and modernised as it entered into an exciting new phase of growth and development including the introduction of 210 000 tpa of chemical cellulose production at the mill. The mill’s total production of chemical cellulose is expected to increase to over a million tonnes per year, entrenching Sappi’s position as a global leader in chemical cellulose production, a fast-growing, high-margin business serving the textiles, consumer goods, foodstuffs and pharmaceutical industries.

With more than 120 years’ experience in the steam generation business, Babcock is one of the most established and experienced suppliers in Africa. Supported by best in class technology, the company’s skilled workforce draws on decades of knowledge and experience, enabling Babcock to provide safe, effective solutions for the entire lifecycle of industrial plant, from design and build, through operation and maintenance, to decommissioning and remediation. Babcock’s engineering business specialises in the front end design of steam generation plant and associated equipment, construction concept generation and development of potential solutions in a business case environment, while focusing on feasibility of new build options, performance upgrades, efficiency improvements and emissions reductions.