Recovering Heat and Water from Flue Gas
Funded through ERA Call #3: Industrial Efficiency, Imperial Oil Resources Limited’s Kearl ConDex Flue Gas Heat and Water Recovery project successfully demonstrated the effectiveness of the technology on an industrial boiler using recycled water from an oilsands mine and natural gas combustion exhaust. The project was at commercial scale and eight times the technology’s previous maximum operating duty, representing a significant scale-up accomplishment.
Oilsands mining and extraction processes require commercial-scale hot water that is primarily produced through contact with steam produced in natural gas-fired boilers. The ConDex technology takes waste heat generated from the combustion process in the boilers and transfers this heat from the boiler flue gas (BFG) to a slipstream of cold process water, increasing the temperature of the water to be used in the warm process water system. Although most industrial boilers have economizers that recover waste heat from the boiler combustion flue gases, only a portion of the waste heat is captured. The energy required to condense water vapour in the flue gas is not typically recovered as the condensed water is acidic and causes corrosion concerns. The ConDex technology recovers additional waste heat by operating well below the dew point of the flue gas, resulting in additional energy from cooling the exhaust temperature and significant latent energy. Using this waste heat from the boiler flue gas to heat the cold process water reduces the required firing rate of the boilers, thereby reducing the GHG emissions. The project successfully demonstrated an energy recovery of 16 megawatts in summer and 24 megawatts in the winter, confirming the anticipated performance at the project approval stage. This energy recovery is estimated to reduce GHG emissions by 33,000 tons annually. During the project, the ConDex was also able to collect 93,700 cubic meters of condensed water that has been recycled back into the process.
Adjusting Systems to Ensure Reliability
The project was successful overall, achieving its objective and demonstrating the technology’s energy-recovering abilities. Along the way, the team had to make various adjustments to the process. During early operation, the condensed water generated in the ConDex condensing economizer contained a larger number of particulates overall, with some specific elemental particulates higher than expected, with the potential to cause damage to the systems. The project team determined that this would impact the operation of the proposed course for the condensed water, back to the demineralization plant, where boiler feed water is treated. To avoid major reliability impacts on the boiler feed water system, the increased particulates required additional water treatment compared to what the demineralization plant was designed for. The condensed water had to be routed back to the alternate warm process water system, where it was circulated through the plant to meet other process needs. Although the condensed water could not be used as a supplemental supply into the boiler feed water system, the water could still be recycled back into the process.
What’s next?
The ConDex technology continues to be a solution in waste heat recovery after this project’s completion in 2022, contributing to environmental sustainability and operational efficiency in industries that utilize high-temperature combustion processes. The successful deployment at Kearl has demonstrated the scalability and effectiveness of the ConDex technology in industrial applications. This success has led to increased interest in adopting the technology across various sectors, aiming to enhance energy efficiency and reduce GHG emissions.