As the world searches for less polluting sources of energy, a number of companies have built pilot plants to determine how best to manage the manufacturing processes for these new materials. The challenge for Leigh Creek Energy Limited was to design, build and commission a pilot plant to transform coal from its solid state into a gaseous form and monitor the technical and environmental performance of the process.
The in-situ gasification process (ISG) produces methane, hydrogen and other valuable components. The synthetic gas (syngas) can be used to produce electricity directly or further refined into a variety of products including synthetic methane and ammonia.
The ISG demonstration project was built to inform the design for a potential commercial facility. It involved the construction of an above-ground plant and a below-ground single ISG gasifier chamber. The pilot plant was built north of Adelaide, South Australia, in the Leigh Creek Coalfield. The site was selected as the result of a screening process using criteria that covered environmental, technical and commercial aspects to ensure it would be safe and minimize any environmental impact.
The pilot project operated 24/7 and has resulted in the successful production of syngas—with a peak flow rate of 7.5mmcf/day. “The success of this trial has effectively unlocked a large energy resource of huge value and captured key data that validates the fact that this proven ISG technology can be successful in a commercial application,” explained Phil Staveley, managing director of Leigh Creek Energy.
The ISG process is a chemical conversion from solid coal to gas. For the reactions to commence, air is introduced through the inlet well and an initiation device is used to create very high temperatures. As the temperature and oxygen concentration reach optimum levels, a series of reactions convert the solid fuel into syngas, which is then extracted through the outlet well.
The area in the coal seam where the gasification takes place is referred to as the gasifier chamber and the reactions that form syngas typically occur at temperatures of between 900?C and 1200?C. Given the process, safety and environmental considerations for the plant, the choice of control and automation system requirements was of paramount importance.
ATSys, a Rockwell Automation Recognized System Integrator, was commissioned to develop the control system for the plant. “We selected Rockwell Automation hardware and software for this project because it has been proven to be reliable and we could be confident that the technology would be fit for purpose for this project,” said Andre Tassone, managing director, ATSys.
The Leigh Creek Energy facility incorporates a number of Rockwell Automation products, including the PlantPAx distributed control system, Integrated Architecture with CompactLogix controllers and PowerFlex drives, and dashboard analysis using FactoryTalk View, VantagePoint and Historian software suite.
The PlantPAx distributed control system delivered advanced plant-wide control and optimization for the plant. By using a common automation platform, it enabled integration between critical process areas of the plant including use of Allen-Bradley CompactLogix controllers and PowerFlex drives with Safe Torque-Off.
This integrated architecture approach reduced engineering time associated with installation and commissioning—a key priority for the project. A key aspect of this architecture is the PlantPAx Library of Process objects—a pre-defined library of controller code (add-on Instructions), display elements (global objects), and faceplates that let ATSys quickly assemble applications with proven strategies, functionality and performance.
“We also decided to design all the equipment on skids to further reduce installation time on site,” said Phil Galbraith, principal control systems engineer at ATSys.
The FactoryTalk product suite provided real time visibility into the system for monitoring and controlling the plant. FactoryTalk View SE was used in a redundant configuration for visualization and control on a pair of PCs running in the control room onsite, helping to ensure reliability for critical control and monitoring functions. FactoryTalk Historian SE and FactoryTalk VantagePoint were used for logging of historical data and visualization on a cloud-hosted system.
Because the pilot plant was in operation 24 hours a day, seven days a week, it was important for operators to be able to access data remotely. In addition to having access to real-time data, it was critical to log data for analytics and reporting to analyze trends, investigate inefficiencies and monitor environmental KPIs.
There is always a risk that pilot projects like this may not be commercially feasible, but the success with the Leigh Creek Energy Project exceeded expectations with its peak flow rate of 7.5mmcf/day, which was higher than anticipated for the ISG process. In addition, the pilot study demonstrated that Leigh Creek Energy has operated the ISG gasifier safely through data analyzed from surrounding environmental monitoring wells before, during and after the trial.
The data recorded reveals that the size of the gas resource is significant, making it one of the largest undeveloped, uncontracted and undervalued gas resources within the east coast gas system in Australia.
