Reducing emissions and operating costs - right sizing power generation and heat recovery
Summary
Our client’s asset power requirements have changed due to the changing production profile. Opportunity exists then to improve efficiency, particularly for the power generation and gas compression facilities, and help reduce operating costs and emissions reduction.
Following on from an initial high-level concept study to identify the various options for increasing plant efficiency, our client asked us to develop implementable options. The scope included looking at the feasibility of replacing and/or modifying existing power generation and gas compression equipment, as well as the viability of installing a sizable new waste heat recovery unit, along with the associated process equipment.
Utilising a multi-discipline team, Apollo established equipment requirements to allow the vendors to provide sizes and weights. Working with the equipment vendors, this information was then used to assess the feasibility of installation and to develop costs for project implementation.
Options were then compared through cost-benefit analysis and on an environmental impact basis. The results of this comparison were then used to make clear recommendations to the client along with the identification of key requirements for the next project phase which are needed to manage any residual risks and optimise project delivery.
The Problem
As assets approach end of field life, production profiles and platform power requirements generally reduce. This leads to power generation and gas compression equipment being significantly over-sized for current needs and often operating less efficiently. This has the outcome of higher than necessary operating costs and emissions, the latter of which is key to meeting environmental targets.
Retrofitting waste heat recovery (WHR) systems to existing North Sea oil and gas production facilities is not common, but advances in technology and government tariffs on emissions are making the installation of these systems more appealing. Other than the cost, the main challenge presented by retrofitting waste heat recovery facilities is the sheer size of the equipment. In this case, equipment weights alone were up to 400t.
To compound matters, the WHR equipment needs to tie into existing turbine exhaust systems which are typically located at the extremities of the asset. This further increases the scale of the challenge.
Client testimonial
“Apollo quickly grasped the scope and interdependencies allowing them to identify the key issues with delivery of these brownfield modifications and what engineering would be required to overcome these challenges”
The Solution
Apollo provided a multi-discipline engineering team with the necessary skills to evaluate the various tabled options appropriately. The options consisted of:
Power Generation:
- Full replacement of a power generation unit
- New power generation unit
- Partial replacement of the existing power generation unit with a new more efficient gas turbine
Gas Compression:
- Full replacement of a gas compression unit
- Partial replacement of an existing unit with a new more efficient engine
- Partial replacement of an existing unit with an electric drive motor & variable speed drive unit
- Re-wheeling the existing compressor
Waste Heat Recovery Package:
- New rankine steam cycle WHR equipment package (estimated 620t package weight)
- New organic rankine cycle WHR equipment package (estimated 1300t package weight)
The team liaised with the client to define the requirements necessary for the equipment and then engaged with the vendors to find appropriate solutions and to tailor these, where possible, to the particular circumstances.
A large part of the scope was the constructability assessment for the various options, which was key to the design feasibility given that the power generation and compression equipment were not originally designed to accommodate major changes. These items were located in difficult-to-reach areas of the platform with limited or no crane coverage for construction activities.
The WHR scope required particular attention in this area given the magnitude of the new equipment.
Industry norms were used to fill in gaps in vendor data and estimate the size and weights of the complete packages to allow the development of new supporting structures and appraisal of existing primary steelwork.
Cost estimates were developed for each viable option to provide the data needed to evaluate the cost-benefit of the options.
Apollo’s technical safety team led a high-level HAZID assessment on each option to ensure platform safety would not be compromised by the modifications.
The final cost-benefit and environmental impact results were presented to the client in an easy-to-interpret format, bringing clarity to the otherwise complex set of considerations. The results also included a clear list of the residual risks the project would need to address along with a scope of work for how this could be achieved in subsequent design stages.
Would you like more information? Contact us today to discuss this further – info@apollo.engineer