Environment industries archive
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Iluka Resources has been actively seeking innovative and profitable Cleaner production solutions to waste problems. Its waste heat recovery power plant is saving it $1.5 million a year while its efforts to find markets for other wastes have resulted in potentially attractive business ventures.
Iluka Resources Limited (formerly Westralian Sands Limited) is an international mining and mineral processing company. The company has operations in Australia, the United States of America and Indonesia and employs over 2500 people.
The company has been mining and processing mineral sands in Western Australia for over 40 years, and is currently ranked second in the world for production levels of titanium minerals and first in the world for zircon production. It is also the most successful producer of synthetic rutile in the world. Other company investments are in tin, coal, copper and quicklime.
Iluka Resources Limited (Iluka) has shown a continued commitment to innovation and the early adoption of new technology. It was one of the first companies to adopt the Becher process for producing synthetic rutile and has also developed methods for turning what were previously waste materials into products for steel manufacture and fertiliser. This level of innovation is a result of the company's continuous focus on process improvement and environmental management.
A major project to more than double the capacity of the company's Synthetic Rutile Plant in North Capel, Western Australia was commenced in 1995. A significant component of this project was to be the handling and treatment of hot waste gas from the plant, which ultimately resulted in the construction of a Waste Heat Recovery Plant. The project was commissioned in the later half of 1997.
Synthetic rutile is produced by removing iron from ilmenite in order to increase the titanium content. Iluka uses the Becher process which involves feeding the ilmenite ore into a rotary kiln to reduce the iron oxides to metallic iron. The iron is precipitated as hydrated iron oxide which, along with other impurities, is removed from the synthetic rutile. Various other wastes are produced, including acidic effluent from leaching of the final product.
The reductant used in the process is coal, which also acts as a fuel for the kiln. The process results in a hot, dirty waste gas stream (primarily CO2) which needs to be treated before it can be released to the atmosphere.
Waste heat recovery
The traditional pollution control method of dealing with a waste gas stream which is high in both temperature and particulates would be to install a wet scrubbing system. While such a system would cool the gas and remove the particulates there are a number of environmental and economic impacts associated with it. These include:
Iluka investigated alternatives to a wet scrubbing system in order to determine whether there was a more effective way of dealing with the waste gas stream. The company finally decided to adopt a major technology modification in the form of a waste heat power generation facility and an electrostatic precipitator for the removal of particulates. This waste heat power generation facility can also be considered on-site recovery as the company is recovering the heat energy in the waste gas to produce electricity which is used on site, reducing the amount of power purchased
A project management team of seven Iluka staff was established and the major construction contract was awarded to Rico Pty Limited of New South Wales. Oracle Engineering provided specialist engineering design services to Rico Pty Limited. Iluka staff maintained a strong involvement with all stages of the project from conceptual design, through to detailed design, construction and commissioning. The final design consisted of a super-heater, boiler and economiser capable of producing about 30 tonnes/hr of steam. This super-heated steam drives a fully condensing steam turbine capable of producing about 6.5 MW of electricity (after allowing for power to run plant auxiliaries).
As this was the first time a plant such as this had been installed on a synthetic rutile plant in Australia a number of challenges were encountered. These were addressed through the innovation, originality and dedication of the team. The challenges included:
Alternative uses for waste
Iluka's Special Projects team has been actively seeking alternative uses for waste. The main initiatives have been as follows:
Pilot furnace smelting iron
Waste Heat Recovery
The financial and environmental benefits of the project are summarised in Table 1. The total cost of the Waste Heat Recovery Plant was just over $20 million and the expected rate of return on the investment was 16%. This compared favourably with the traditional wet scrubbing system that was expected to cost around $9 million but had no financial return on investment.
The plant now generates up to 6.5 MW of electricity, with an average of 5.5 MW. Of this 4 MW is used in the new synthetic rutile plant, 0.7 is used to run the Waste Heat Recovery Plant auxiliaries and any excess is used in other parts of the North Capel operations. By avoiding the need to purchase electricity and taking into account operational costs, the company is saving over $1.5 million per annum. With a payback time of 8 years and an expected operating lifetime of over 25 years, savings will continue to accumulate well after the plant has paid back.
Table 1. Financial and Environmental Benefits
|Total Investment||$20 million|
|Energy Generated on Site||Up to 6.5MW pa|
|Annual Energy Cost Savings||$1.5 million|
|Expected Return on Investment||16%|
|Expected Payback Period||8 years|
|Expected Operating Life||25 years|
|Annual Greenhouse Gas Emission Reductions||52,000 tonnes CO2 equivalent|
|Annual Water Savings (compared to alternative technology)||1.2 million litres|
As electricity generation is primarily based on the burning of fossil fuels, this project significantly reduces the associated environmental impacts. The project reduces the volume of coal required to provide electricity to the site by about 25,000 tonnes per annum and reduces the greenhouse gas emissions that would result from burning the coal by about 52,000 tonnes of CO2 per annum.
Other environmental benefits include a decrease in water consumption of about 1.2 million litres per annum as opposed to if the wet scrubbing system had been installed. In addition, the electrostatic precipitator reduces particulate emissions from the plant to well below current regulations. The levels are also expected to be below any regulations that may be imposed in the foreseeable future.
Additional uses for waste
While it is too early to estimate the potential benefits of pig iron production the economics appear to be favourable when considering the savings in of waste disposal costs, the potential capital costs and revenue streams. Potential pig iron production is estimated at 300,000 tonnes a year from recovered landfill waste as well as annual waste generated.
The fertiliser and soil conditioner initiative has not yet broken even yet but could do so and be profitable if sales volumes can be increased.
Iluka estimates that its carbonaceous material business could be expanded to be worth several million dollars a year.
As part of a major upgrade at the North Capel Synthetic Rutile Plant in 1995, the treatment of hot waste gas was an important consideration. Making use of the energy contained in the waste stream became a significant area of focus, with several options being investigated.
The main barrier to the implementation of the Waste Heat Recovery was the perceived risk of adopting a new and somewhat unknown (at least to Iluka Resources) technology. Most businesses would agree that it is far easier to adopt traditional, well established processes. However, this means that the benefits of newer technologies are frequently overlooked. Iluka had to look closely at what financial and environmental benefits the project offered, and at how the company could minimise its exposure to risk. In the end, by weighing the risks against the benefits of the project, the decision was made to go ahead.
In addition, Iluka Resources had to address an issue faced by many organisations investigating distributed power generation. The company's core business is not power generation, but the mining and processing of minerals. Consequently, it has to ensure that production takes precedence over energy generation, and that at no time does energy generation dictate production conditions.
Similar considerations have applied to developing uses and markets for wastes.