Development of a rehabilitation system for the red mud waste generated at the Aughinish Alumina Bayer Plant

Aughinish Alumina Limited (AAL) have an obligation by terms of their Integrated Pollution Control Licence (IPCL) and Planning Permission to establish vegetation on the red mud stack at their plant at Aughinish, Co. Limerick. High pH and high exchangeable sodium percentage are the main known factors limiting the establishment of vegetation on red mud. Gypsum addition has been known to assist in alleviating these problems in other countries. However, there is no experience or published information on red mud rehabilitation under Irish conditions. Red mud with organic and inorganic waste-derived ameliorants as well as selected grassland species were examined under laboratory controlled environment conditions as well as in field plot trials. Also, in order that it would be economically achievable, the research utilised locally available waste products as the organic amendments. Screening trials found that physical constraints severely limit plant germination and growth in red mud. Gypsum addition effectively lowers pH, exchangeable sodium percentage and the availability of A1 and Fe in the mud. A strong relationship between pH, ESP and A1 levels was also found. Gypsum addition increased germination percentages and plant growth for all species investigated. Greenhouse trials demonstrated that organic wastes alone did not greatly improve conditions for plant growth but when used in conjunction with gypsum plant performances for all species investigated was significantly increased. There was a high mortality rate for grasses in non-gypsum treatments. An emerging trend of preferential iron uptake and calcium deficiency in non-gypsum treatments was found at pot screening stage. Species also displayed manganese and magnesium deficiencies.

Evaluation of the determinism of the actuator sensor interface (ASI) on programmable logic controllers (PLC), personal computers (PC) and real-time operating systems (RTOS)

The purpose of this study was to evaluate the determinism of the AS-lnterface network and the 3 main families of control systems, which may use it, namely PLC, PC and RTOS. During the course of this study the PROFIBUS and Ethernet field level networks were also considered in order to ensure that they would not introduce unacceptable latencies into the overall control system. This research demonstrated that an incorrectly configured Ethernet network introduces unacceptable variable duration latencies into the control system, thus care must be exercised if the determinism of a control system is not to be compromised. This study introduces a new concept of using statistics and process capability metrics in the form of CPk values, to specify how suitable a control system is for a given control task. The PLC systems, which were tested, demonstrated extremely deterministic responses, but when a large number of iterations were introduced in the user program, the mean control system latency was much too great for an AS-I network. Thus the PLC was found to be unsuitable for an AS-I network if a large, complex user program Is required. The PC systems, which were tested were non-deterministic and had latencies of variable duration. These latencies became extremely exaggerated when a graphing ActiveX was included in the control application. These PC systems also exhibited a non-normal frequency distribution of control system latencies, and as such are unsuitable for implementation with an AS-I network. The RTOS system, which was tested, overcame the problems identified with the PLC systems and produced an extremely deterministic response, even when a large number of iterations were introduced in the user program. The RTOS system, which was tested, is capable of providing a suitable deterministic control system response, even when an extremely large, complex user program is required.