Challenges in using waste heat recovery and DLE combustion to reduce CO2 & NOX emissions

Developing new oil and gas plants in today´s economic and environmental climate requires significant design effort and planning before any sanction to proceed is likely to be received. Electrical power requirements are increasing, with greater use of large electric motor driven equipment than ever before to give better control, reliability and flexibility of the production equipment and systems. Many of these oil & gas plants are located in remote areas with little or no utilities infrastructure, and require their own dedicated power generation and distribution facilities. With the increasing cost of energy, greater legislation, and rising awareness to environmental concerns, oil & gas plant operators have placed a high emphasis on improving overall efficiency and reducing emissions produced from burning hydrocarbon fuels to provide electrical/mechanical energy. Greater use of exhaust heat recovery from gas turbine driven generators has led to reduced requirements for separately fired heaters and boilers, with comparable reduction in carbon dioxide (CO2) and nitrogen oxides (NOx) emissions, for example. NOx have also been reduced by specification of dry low emission (DLE) combustion technology for many gas turbine driven generators and compressors. However, this drive to improve overall efficiency and reduce emissions, particularly for gas turbine driven generators, also presents its own challenges. This paper examines some of the difficulties and consequences. It considers balancing the desire to minimise the emission of pollutants from power generation equipment in normal operation with the need to provide a safe and reliable source of power for the process plant, thereby minimising potential process plant shutdowns and the corresponding flaring of inventory which this often leads to.