Topic last reviewed: 1 February 2014
Sectors: Downstream, Midstream, Upstream
As explained in the Energy Efficient Design module, energy efficiency in a new facility design may be achieved through a number of design optimization steps. Once a facility has been commissioned and is in operation, the issue arises of how to maintain or improve upon its efficiency performance. Performance and efficiency monitoring can allow a plant to maintain the highest practical efficiency of facilities and processes.
Systems for monitoring and optimizing the performance of oil and gas process facilities are essential for maintaining and maximizing their energy efficiency. Monitoring systems are widely used in the oil and gas industry, and make use of modern sensors, data collection and information management, as well as sophisticated control and analysis software.
The basic goals of performance monitoring and control systems are to keep each process as close as possible to its optimal operating conditions, to coordinate the dynamics of different sub-systems to promote stable, maximal production, to minimize and/or accommodate disturbances and system transients, and to identify damaged, fouled or degraded components.
Monitoring and control systems include electronic sensors, digital data acquisition systems, networks and computers for collecting, storing and analyzing data, and feedback control systems and actuators for automatically adjusting operating parameters. Computer models of the systems being controlled are also frequently used to predict deviations from expected/optimal performance. Control software may also be used for automatically initiating maintenance activities, and optimizing the control systems themselves, as in automatically tuning closed-loop feedback controllers.
As discussed in the Energy Efficient design module, small improvements to a facility’s energy efficiency can have a large impact on facility profitability. However, poor facility reliability and availability can be detrimental to profitability. Performance and efficiency monitoring is essential for maintaining facility reliability and availability and may therefore also have a large impact on profitability.
Application of Technology
All facilities should monitor operational performance and efficiency, including both older facilities that may not have incorporated energy efficient design principles, as well as recently commissioned energy efficient facilities.
- Older Existing Facilities – performance and efficiency monitoring is important for these facilities to remain competitive with newer, more energy efficient facilities. Performance and efficiency monitoring equipment and systems may not have been included in the original facility design and build, but may be added during a facility retrofit. Installing modern monitoring and control equipment can, in some cases, allow operational improvements so that the facility meets modern tightened criteria pollutant limits without needing further process equipment retrofits (e.g. of post-combustion emissions controls).
- Newer Existing Facilities – newer facilities typically already incorporate some of the energy efficient design principles discussed in the Energy Efficient Design module. To maintain high energy efficiency, new facilities tend to incorporate performance and energy efficiency monitoring equipment and systems when the facility is designed and built.
Monitoring and control systems are used at all stages of oil and gas production and distribution. They are also applied at all functional scales, from individual pieces of equipment to entire production plants. Examples of specific applications include:
- Monitoring of multiphase fluid parameters in pipes to counteract ‘slugging’ transients
- Monitoring of pressures, temperatures and flowrates of different process streams in oil refineries to optimize performance
- Monitoring of heat exchangers to help reduce or eliminate fouling issues [refer to the Heat Exchanger module, Case Study on fouling prediction software]
Day-to-day energy performance can be monitored using key energy parameters (KEPs), relative to KEP targets and allowable ranges. These targets and limits may need to be dynamic, so they can shift with the type of feedstock and desired product, ambient conditions, and other factors influencing the operating state of the plant. KEP targets and ranges can be set by statistical analysis (e.g. using statistical process control (SPC) tools) and/or system models (which may be developed from first principles). A dashboard, showing KEPs and their allowable ranges can be used for real-time monitoring of KEPs, with green, orange and red coloring to indicate acceptable, warning and out-of-control energy/efficiency performance.
|Years experience in the industry:||21+|
Range of application:
|Upstream production processes; refineries; fuel systems; feedstock systems; heat systems; power systems|
|Guideline capital costs:||Upfront costs for measurement and control systems range from hundreds of dollars for simple, low-pressure sensors, to millions of dollars for large, integrated monitoring systems|
|Guideline operational costs:||Major operational costs include labor for periodic calibration and for maintenance/repairs; costs of software and software updates; electricity usage|
|GHG reduction potential:||Effective monitoring and control allows systems to operate much more efficiently, using less thermal and electrical energy inputs. GHG emissions associated with these energy inputs are accordingly reduced|
|Time to perform engineering and installation:||1-24 months. This broad time range reflects that the time to perform engineering and installation is highly dependent of the complexity of the system being examined|
|Typical scope of work description:||
Mass and energy balances (both individual systems and overall), which require accurate mass flow inputs, will help to identify errors in meters. The quality of the data is key.
|Technical:||Measurement accuracy, range, stability, sampling rate, signal-to-noise ratio, and response time
Ease of installation and integration; device size
Need for external power supply; need for wired or wireless interconnection
Ease of calibration and maintenance
Flexibility to adapt to changing monitoring needs (e.g. adding measurement channels in the future)
Need for redundancy
Range of tolerated operating conditions (e.g. surrounding temperature, vibration environment)
Ease of use by operators; ease of calibration and servicing
|Commercial:||Reputation of supplier and reliability of their product
Expected life of measurement/monitoring system
Availability of technical support, training and replacement parts
Strength of product warranty
|Environmental:||Direct environmental impacts from monitoring equipment (e.g. energy use) are negligible relative to those of the plant they help optimize and the gains from that optimization. Effective use of monitoring technology allows more efficient usage of plant equipment, allowing more efficient use of process inputs and reductions in waste streams. This may result in GHG and/or air pollutant emission reductions.|
|Economic rule-of-thumb:||Monitoring costs are usually dominated by capital, installation and commissioning costs. These costs can be offset by savings from more efficient operations over the life of the systems|
Performance monitoring can be accomplished with a broad suite of monitoring equipment and systems.
The main operational risks associated with monitoring equipment are those associated with measurement error. Excessive measurement error leads to sub-optimal system control and operation; hence calibration and testing at adequate intervals are necessary. Incorporating some redundancy between monitoring sensors/systems can help mitigate measurement error risk by allowing cross-checks between monitoring signals by the controlling software.
Proper use of monitoring equipment can improve process efficiency, reliability and safety. By allowing more optimal and robust equipment utilization it can also reduce operating costs.
Industry case studies
1. Performance monitoring for a cogeneration captive power plant [Reference 1]
An oil refinery was built and commissioned in 1998 with a capacity of 6 MMT/year but later expanded to 12 MMT/year. To meet its power requirements, 227 MW of captive cogeneration power plant was commissioned by integrating with the steam systems of the Naphtha Cracker system at the same petrochemical complex. The complete project included an Energy Management System (EMS), a Distributed Control System (DCS) and a Performance Monitoring System (PMS).
First the PMS solution was customized and installed as per the site requirements. As there were no drivers present for communication, the communication was carried out over the OPC communication interface. PMS calculation tags were compared with the field tags and the calculation engine was upgraded after finding mismatch in units of flow parameters. To avoid mismatch between DCS and PMS, the communication loop was checked several times.
The performance monitoring for the gas turbine is carried out by performing calculations of power output and heat rate after taking readings of the various parameters from the online measuring instruments to the DCS and correction factors as per the GTG performance curves. The measured Gross Heat Rate of the gas turbine is computed based on measured gross power and the actual heat input to the gas turbine. Thermal calculations are based on several ASME PTCs.
- Real time feedback to operator on boiler efficiency, turbine heat rate, cycle efficiency and equipment performance.
- Portability and integration to different DCS platforms. Scalable from unit level to plant level application. Accurate calculations as per ASME PTC codes. Facility for user configurable calculations.
- Removal of human error in calculations.
- Calculations can be done at set interval without manual intervention.
- Trend analysis and reporting can be done at the DCS.
2. Fouling: Implementation of performance monitoring at the Irving oil refinery [Reference 2]
Canada’s largest oil refinery, at Saint John, NB, had asphaltene deposits in the preheat train heat exchangers, requiring extra fuel to the furnace to makeup the temperature for efficient distillation. Fouling monitoring software was used to pin-point the exact time that the fouling event occurred, which exchangers fouled, how much fouling had occurred and the value of the cleaning the fouled exchangers. The fouling monitoring program calculated the fouling factor daily for the exchanger, so that changes in fouling behavior as a result of crude type can be identified on time.
- Kalkitech Energy Systems, Performance Monitoring for a Cogeneration Captive Power Plant of an Oil PSU
- Waters, A., Akinradewo, C. and Lamb, D., Fouling: Implementation of a crude preheat train performance monitoring application at the Irving oil refinery, Proc. Int. Conf. Heat Exchanger Fouling and Cleaning VIII, 2009.