ADNOC Gas Processing is looking into the energy saving opportunities to improve plants energy performance, aiming continual improvement and also for sustaining the already achieved efficiency improvement in varying operating scenarios. It is in line with the ADNOC Sustainability Strategy target for the Year 2030 which requires reducing the Green House Gases (GHG) intensity by 25% in Year 2030 considering Year 2018 as the baseline. Therefore, multiple avenues and opportunities were looked into to contribute towards this ambitious target. One of the promising contributors, having substantial potential of energy savings, is the Waste Heat Recovery. In this context, ADNOC Gas Processing has evaluated the option of utilizing waste heat from different heat sources across different plants using the Organic Rankine Cycle to generate power. Waste heat sources like exhaust gases from power generators, mechanical drive gas turbines, heaters and incinerators stacks, and low pressure steam condensers have been assessed. This opportunity of waste heat recovery exhibits substantial potential to contribute towards GHG emissions intensity reduction, reduce power import, improve energy efficiency and reduce the operating costs. The paper presents the techno-economic appraisal of the opportunity for the selected waste heat sources.

Acid Gas Recovery Units (AGRUs) are one of the core and energy intensive units in gas processing. In solvent based AGRUs, the rich solvent leaving absorber column is letdown across control valve before being sent to flash vessel. This pressure letdown indicates opportunity to recover energy by utilizing hydraulic turbine. In this context, an in-house study has been carried out to evaluate techno-economic feasibility of recovering energy from four (04) amine based AGRUs at one of the gas processing sites. Pressure letdown, across amine absorber control valves at selected AGRUs, from 60 to 7 barg indicated significant potential for energy recovery. A comprehensive review of existing design and current operation of AGRUs was carried out by technical team in close co-ordination with site personnel. Design inputs were prepared after discussions with Operations and Technical Services teams to evaluate modifications needed to implement the Hydraulic Power Recovery Turbine (HPRT). Internal estimation of potential power recovery was prepared and modifications needed to develop scope definition were identified. The team consulted potential suppliers for new equipment and technical proposals were evaluated for technical feasibility after discussions with multidisciplinary engineering teams. The key challenges relate to the feasibility of modification given the brownfield modifications, as the piping routing with existing arrangement of equipment like HP absorber, lean gas circulating pump and rich amine flash vessel etc., could lead to potential constraints of space availability and pipe-rack adequacy. In addition, competent contractors are required to implement modifications to existing lean amine circulating pump as shaft modifications are needed. Efficiency of hydraulic power recovery turbine and performance guarantees signifies the successful implementation. Overall cost, economic feasibility over its lifecycle and schedule for implementation are few of the the major factors governing the management decision. Based on current operation, preliminary estimates indicated power recovery potential of the order of around 5MW, from the four (04) AGRUs considered in the study, duly considering the overall efficiency of HPRT. The study ascertained significant reduction in power consumption of lean amine circulating pumps by utilization of recovered hydraulic power from respective AGRUs. Economic feasibility observed sensitive to applicable power tariff and other financial basis. However, on overall basis, study established that HPRT technology represent reliable, economically feasible solutions to reduce power consumption and emissions, thereby improving energy efficiency of gas processing industry.

The compression units installed on sales gas network face wide range of operating modes owing to the varying supply & demand scenarios and the associated network dynamics. It is very challenging to ascertain the real performance in such applications due to changing specific energy consumption. The paper presents development of a novel and robust monitoring system, enabling realtime energy performance monitoring of dynamic compression and revealing realistic opportunities for energy savings. The methodology comprised review of design and OEM data for the compression units, followed by review of operating envelope. Subsequently, developed a thermodynamic model of compression units encompassing all the operating modes. Then embedded the actual performance curves from OEM in the thermodynamic digital twin and validated the model with actual operating data. Carried out site visits and held discussions with technical teams as part of the comprehensive approach. A mathematical model additionally developed, in addition to the thermodynamic model, to enable operators for off-line monitoring of the compressors performance during unavailability of thermodynamic digital twin. Detailed performance analysis of centrifugal compressors is essential to ascertain their condition and functioning. A decrease in performance can be an indication of internal wear or fouling, which if allowed to continue, may result in reduced throughput or excessive energy consumption or even unscheduled outages. Thus, the performance is not just an indication of energy or operating cost but also reflects other vital aspects like reliability. The integrated thermodynamic digital twin developed for large sales gas compression units, with total throughput capacity of more than 500 MMSCFD, has enabled and demonstrated effective energy performance monitoring even with changing operating scenarios. It facilitated real-time comparison of actual performance (specific energy consumption) with model based expected performance. It also aided real-time trending of polytropic efficiency as well as real-time display of potential energy savings opportunities. The digital twin has proven to be a reliable and low cost tool to predict compressor performance for various operating modes on real time basis. The data from the compression digital twin can be tied into process simulation models for process optimization. The model can complement supervisory capabilities, diagnostics, control capabilities and even facilitate in predicting failures ahead of time.

Process refrigeration units are one of the major energy consumers at gas processing plants. Owing to the higher energy consumption, evaluation and benchmarking of energy performance of the refrigeration units is very important for identification of energy saving opportunities. In this regard, an energy performance benchmarking study was performed by detailed assessment and evaluation of the existing process refrigeration units to identify potential of energy efficiency improvement. The study encompassed twenty-one (21) process refrigeration units installed at five (05) different sites. The methodology included collection and analysis of design & operation data and review of key variables like percent load, anti-surge valve opening, condensing temperature & pressure and chilling temperature etc. Energy Performance Indicators (EnPIs) considered for the benchmarking were compressor's specific energy, coefficient of performance (COP) and relative COP (RCOP). A thermodynamic model was developed for each unit to ascertain the refrigeration load. Instead of usual high level benchmarking techniques, the study considered unit and equipment level benchmarking which provided better insight of the systems and helped in finding opportunities for energy efficiency improvement. Further, COP which is generally considered as a benchmarking EnPI, only considers refrigeration load and energy consumption, whereas, this study introduced a new EnPI named "Relative COP" which additionally takes into account the chilling and condensing temperatures and gives true energy performance benchmarking.

Energy efficiency improvement and optimization of energy aspects on new developments and projects has always potential to reduce emissions. It also has potential to reduce depletion of non-renewable energy resources, in addition to the potential benefits in project economics, through reduction of capital and/or operating cost. Realizing the gravity, GASCO which is one of the largest onshore gas processing companies, decided to develop a comprehensive Framework to focus energy efficiency improvement and optimization at project phase. GASCO started by outlining the specific objectives to be achieved regarding energy optimization and energy efficiency improvement thru energy aspects consideration, with emphasis on complete project lifecycle. Subsequently, developed the comprehensive framework to achieve the objectives. This framework is referred as GASCO Project Energy Optimization (PEO) Framework.The PEO Framework provides a structured process for review and optimization of energy aspects on new projects and defines the requirements for energy planning and reporting throughout the project lifecycle. Key components of the framework include processes for assessment and optimization of energy aspects, techniques for assessing energy aspects through workshops and desk top studies and guidance on energy optimization at an overall level, process system level and detailed equipment level.GASCO implemented the PEO Framework on two of its major projects. Numerous challenges were faced during initial implementation of PEO Framework. Few of the key challenges faced were lack of integration of energy optimization activities with traditional working of multiple disciplines engaged on the project, lack of familiarization with PEO Framework, difficulty in PEO Framework based scope comprehension and benefits quantification. GASCO tackled these challenges by appropriate improvement measures including PEO Framework introduction and orientation sessions for project personnel, nomination of focal person to respond all PEO Framework related clarifications and development or improvement of methodologies and techniques on case to case basis.Substantial benefits were realized in PEO Framework implementation in terms of system improvement as well as project-specific energy performance improvement. Few of the benefits availed include demonstration of effective energy information flow across discrete phases of project lifecycle, energy aspects reporting and tracking, experience of organizing and conducting Energy Review Workshops, introduction of energy related performance guarantees and development of technique for benefits quantification. PEO Framework implementation on two projects has substantively achieved the underlying objective of formal evaluation of energy aspects. Further, awareness and knowledge about PEO Framework procedures & requirements has increased among GASCO staff as well as project teams of respective Consultant / PMC. The paper throws light on the key attributes and features of PEO framework and shares the experience of...