Automation for an alternative waste technology plant

Western Metropolitan Regional Council (WMRC) is one of Perth's regional waste management groups comprising five members; namely Mosman Park, Cottesloe, Claremont, Peppermint Grove and Subiaco councils. AnaeCo has an agreement with the WMRC to construct and operate a commercial-scale DiCOM facility at its existing waste transfer station, 6 km from the Perth Central Business District. The DiCOM process is a community friendly and environmentally sustainable alternative to landfill disposal of putrescible wastes.

The facility will include a waste sorting and preparation facility and three DiCOM biological processing vessels, including associated ancillary equipment. The facility will be located immediately adjacent to the existing transfer station building.

The project will be a powerful demonstration of the potential that the DiCOM technology presents in the municipal solid waste (MSW) processing sector as it will, for the first time in Australia, allow for the retrofitting of existing transfer stations with MSW processing technology.

MSW arriving at the DiCOM AWT facility is initially sorted to recover inert, recyclable items such as metals, plastics and glass using a predominantly mechanical sorting with minimal manual intervention. Approximately 80% of MSW delivered to the facility can be diverted from landfill through this process.

A four-stage DiCOM bioconversion process is then performed for the recycling of solid organic waste into organic fertiliser and renewable energy.

After the organic material is mixed and pulverised it is loaded into a treatment vessel where it undergoes aerobic treatment. Anaerobic processing then occurs in the same vessel through the introduction of carefully regulated bacterial inoculum in the form of an inoculum solution.

This part of the process produces methane gas used to generate electricity to meet plant needs.

Surplus can also be sold to the electricity grid - it is estimated that the DiCOM Alternative Waste Technology facility at Shenton Park could generate enough renewable energy to provide the annual electricity needs for up to 2700 homes.

After anaerobic processing, the inoculum is drained from the vessel, air is reintroduced and secondary aerobic processing occurs to convert the material into compost. The compost is removed from the treatment vessel and is made available for retail sale, or use in agriculture.

The DiCOM Bioconversion cycle occurs over a 21 day period and is managed by a fully automated control system that constantly monitors and adjusts vessel conditions to deliver an optimal result.

ABB's System 800xA automation system has been selected by AnaeCo to control the facility.

ABB will supply the complete hardware, engineering and commissioning of the control system, drives, analysers, instruments and field devices.

Hafeez Abdulaziz, projects proposal engineer, ABB Australia, says: "ABB is thrilled to be involved with this project as it will be a powerful demonstration of the potential that this technology presents in the municipal solid waste (MSW) processing sector."

Hafeez adds: "The process will be fully automated using ABB System 800xA with extensive use of the Profibus communication protocol for all the drives and field devices. The plant process data will be monitored and controlled remotely from the AnaeCo staging facility. Sensors will monitor the conditions within each vessel and will set and vary the flow of air and water, thereby regulating moisture levels, temperature, pressure, oxygen, carbon dioxide and methane, as well as odour generation and control."

ABB's solution offering includes ABB's Industrial IT 800xA system, field instruments (safe and hazardous areas), gas analysers (safe and hazardous areas) and drives, all integrated to 800xA through Profibus.

Thomas Rudas, AnaeCo's managing director says: "We selected ABB as the preferred automation provider because of its state-of-the-art integrated solution and its excellent price-performance ratio. With the Profibus connections, AnaeCo will also benefit from a high degree of standardisation for planning and documentation and an extremely flexible system in regards to operation, maintenance and future expansion opportunities."

The project's controls concept was developed by Hero Engineering who, as a key member of AnaeCo's EPCM team, will be working closely with ABB. The project will be delivered in two stages, with the second stage commencing approximately six months after the completion of stage one.