Written by Tim Highfield and Yael Muniz Calderon.
Digital tools for emissions estimation are widely spread nowadays given the imperative for companies to meet decarbonisation targets and reporting. However, if the software could not only calculate the emissions but provide insights about energy efficiency and process anomalies, this would optimise the system and reduce Greenhouse Gases (GHG) simultaneously.
io provides a service combining software interpretation and consulting to provide abatement solutions and a roadmap to reach the desirable targets.
As an example, io recently completed a first stage of an emissions and energy efficiency study for a client, on a major offshore oil production facility. The facility itself is relatively modern and has over 20 years of field life remaining.
io’s analysis used both design and operating data and considered all the major sources of emissions and consumers of power, both direct drive and electric, on the facility. This included gas turbines, flares, stages of centrifugal compression and centrifugal pumps.
To perform the analysis io used a software platform that can process minute-by-minute operating data from the data historian. This allowed io to process data for over 300 instruments (approximately 190 million data points) from 2022 to understand how the facility operated and how each item of equipment performed against its original design.
key findings
io’s analysis demonstrates that the equipment was largely operating on the design head and efficiency curves and that the gas turbines were not degraded, which is not unexpected for new facility.
From an emitters point of view, the gas turbines were operating at partial/low load with hot sparing which resulted in a higher heat rate and low efficiency causing increased fuel gas usage and thus emissions. Several trips had occurred during the year which shutdown the operational and hot spare turbines, in both the power generation and direct drive compression systems, which resulted in flaring.
The total amount of flaring was low throughout the year however there had been several trips of the gas turbines which resulted in flaring events.
From the consumers point of view, all the compressors were in recycle mode with over 50% of the compressor load coming from the recycle of gas. This resulted in higher gas turbine loads, and thus emissions, for both direct drive and power generation.
Equally, the pumps were in recycle resulting in higher gas turbine loads for power generation.
initial insights
If hot sparing reduction was possible the emissions on the facility could be reduced by 35% in 2022 with no CAPEX or OPEX investment – this is broadly in line with the IEA findings that “material and energy efficiency make important contributions to reducing industrial emissions, accounting for around 25% of emissions reductions by 2050 in the Net Zero Emissions by 2050 Scenario, relative to today’s levels” [1].
There is available capacity in one gas turbine for the power generation requirement (load moves from approximately 38% to 76%, resulting a decrease in heat rate and an increase in efficiency of approximately 5%.
The situation in the direct drive gas turbines is similar, however the degree of recycle in the centrifugal compressors results in a 50% reduction in emissions if one gas turbine is simply switched off and hot sparing eliminated.
The trips of both the operational and hot spare gas turbines demonstrated that the hot sparing did not provide the availability that was intended to and root cause analysis into these trips is required.
If the emissions could be reduced by 35% the carbon intensity (TeCO2e/bbl) would be reduced by the same percentage transforming the asset to one of the lowest carbon intensity facilities in the company’s portfolio. Furthermore, if the gas was redirected to export rather than power generation, an additional revenue of 3 to 4.5 MUSD per annum could be realised.
io’s work to further reduce emissions on the asset is continuing and we are looking at over 30 options for short-term emissions reduction using operational enhancements and digital tools (e.g. the efficiency of a gas turbine can be increased by 2-3% at lower loads by adjusting the inlet guide vanes).
A further 45 options are being evaluated for mid and long term emissions reduction and energy efficiency improvements, including the retrofitting of variable speed drives on key items of rotating equipment and a battery energy storage system to accommodate start-up of spare equipment and provide “hot sparing”. Electrification using renewable energy and the use of CCS are being evaluated as long term solutions to minimise scope 1 and scope 2 emissions as well.
conclusions
io’s study has identified immediate means in which the CO2 emissions from the facility can be reduced by up to 35%. The ongoing studies will provide the techno-economic analysis to reduce the emissions further and provide a roadmap in line with the company’s long term emissions reduction goals and net-zero commitments.
To discuss how io can help with understanding your emissions and providing insights for emissions reduction and/or enhancing production efficiency and energy efficiency please contact Tim Highfield, Director, Industrial Decarbonisation (tim.highfield@ioconsulting.com).
1 - International Energy Agency, Achieving Net Zero Heavy Industry Sectors in G7 Members.