An oil refinery is an industrial separation and production aggregation of processes where crude oil which comes from the ground (from drilling process) is transformed and refined into more useful products such as petroleum, light and heavy naphtha, diesel, and others useful and needful compounds or fuels. Oil refinery plants are huge, sprawling industrial complexes with extensive piping carrying feeds, gas, steam, and other fluids between large chemical processing units, such as distillation columns, reactors, and storage tanks. Each refinery has its own unique arrangement and combination of dedicated refining processes and units mostly determined from the refinery location and economic constraints.
Raw (unprocessed) crude oil is not useful in an industrial or any other application. Therefore, the crude oil consisted of hundreds of different hydrocarbon molecules is separated in a refinery into components that can be used as fuels, lubricants, and feedstocks in petrochemical and other processes which manufacture products such as plastics, detergents, solvents, elastomers, and fibers. Different boiling points (vaporization temperatures) allow the hydrocarbons to be separated by the distillation (separation) process. Since crude oil contains hydrocarbons of varying molecular masses, forms, and lengths (paraffins, aromatics, cycloalkanes, alkenes, dienes, and alkynes). The differences in the structure of these hydrocarbon molecules make their physical and chemical properties varying. This variety of physical and chemical properties is what makes crude oil useful in a broad range of applications. Oil refineries also produce various products such as:
- Hydrogen, light hydrocarbons, reformate and pyrolysis gasoline used for further blending or processed further on-site.
- Sulfur which is sold to the chemical industry.
- Different shares of petroleum products which are typically sorted in four categories: light distillates (LPG, gasoline, naphtha), middle distillates (kerosene, jet fuel, diesel), heavy distillates and residuum (heavy fuel oil, lubricating oils, wax, asphalt) usually used as an engine fuel or in construction.
- Petrochemical organic compounds that are the ingredients for the chemical industry and pharmaceuticals.
- Heat and electricity
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Oil refineries are large scale plants, processing about a hundred thousand to several hundred thousand barrels of crude oil a day. Because of the high capacity, many of the units operate continuously, as opposed to processing in batches, at steady state or nearly steady state for months to years. The high capacity also makes process optimization and advanced process control very desirable.
Primary Process Control Improvements for Refining Units
Prior to any advanced process control (APC) project, even in refining plants, base-level PID tuning and optimization is a critical pre-requisite step. Unless base-level PID control loops are well tuned, advanced process control (APC) cannot work well, since advanced process control (APC) will be manipulating the setpoints of the base-level PID control loops. Therefore, the first necessary step in the overall process control improvement procedure for refining plants is PID tuning and optimization of primary or base-level PID controllers. The benefits of PID tuning and optimization in refining plants is the reduction of the oscillation amplitude or increase of the controller action by a factor of 2 or 3. This allows to enable smoother running of the refining plants with increased stability in all control loops avoiding unnecessary refining plants problems such as: damage and/or to fast wear and tear of the equipment, plant irregular shutdowns or off spec product properties and/or grades.
Many engineers are worried about causing shut-downs and operating problems when tuning PID controllers on equipment in the refining plants. Trial-and-error PID tuning methods can be ineffective and even catastrophic since these processes are super-fast and very unforgiving.PiControl Solutions LLC has extensive experience in PID tuning and optimization for PID controllers in the refining plants. We understand and know how to tackle with typical PID control loop problems and have customized PID tuning and optimization software tools to help optimize all refining plant controllers.
Our unique and novel closed-loop system identification technology makes it possible to tune and optimize base-level PID control loops quickly, efficiently and precisely. With our closed-loop technology we can perform system identification and PID tuning optimization of the following critical base-level PID controllers easily. Moreover, all process and data analysis and PID tuning and optimization work can be easily performed remotely by PiControl Solutions LLC process control engineers.
Advanced Process Control (APC) Improvements for Refining Units
PiControl Solutions LLC has extensive experience in advanced process control optimization for refining plants. We understand the economics factors that drive the profit margin and have customized multivariable closed-loop system identification and advanced process control (APC) design and optimization tools to help optimize and improve the refining plants.
We apply DCS-based APC (advanced process control), which is faster, cost more effective, all inside the existing DCS/PLC, avoiding the complications of OPC/other data communication links from computer to DCS.
We focus to analyze the process and provide the right economic advanced control solution for each refining plant. Our DCS-based APC (advanced process control) methodology has proven particularly successful in the refining plants. Our DCS-based APC (advanced process control) design will result in the following refining plant benefits:
- Maximization of unit production rate
- Minimization of unit utilities
- Minimization of unit waste and off-spec products
- Reduction of unplanned unit or equipment shutdowns
- Provided faster unit grade transitions
- Achievement of faster unit or equipment new conditions
- Improvement of unit or equipment control stability and increasing safety
- Reduction of operator mistakes
Some examples of the achievable benefits are as follow:
- Crude oil distillation unit product properties and quality (purity, distillation start or end point, dew point) predictions and inferential control.
- Vacuum distillation unit product properties and quality inferential control.
- Inferential control of the Claus recovery unit and prediction of the sulfur content.
- Improvement of the Catalytic Reformer conversion.
- Boiler unit increased stability and increase of the steam production.
- Improvement of the furnace control performance by avoiding fuel fluctuations and dynamic transitions of the burning process.
- Improvement of the Fluid Catalytic Cracker (FCC) controls and conversion.
- Improvement of the Isomerization unit conversion.
- Improvement of the compressor performance and many others.
After DCS work on advanced process control (APC) schemes is complete and all advanced process control (APC) parameters are calculated and optimized, PiControl Solutions LLC will over factory acceptance test (FAT) make sure that the advanced process control (APC) design is complete, correct and operable. After completion of process control (APC) control project, PiControl Solutions LLC will conduct dedicated process control training for refining company. PiControl Solutions has designed, optimized and started more than several well-proven refining control.
PiControl Solutions expects to see a minimum 2-10 % improvement in the refining plant’s operating efficiency production and a 30 – 50 % or more reduction in oscillation amplitudes due to optimized and advanced control. The oscillation reduction will enable smoother but faster running of the plant with increased stability in all control loops.
PiControl is an innovative process control software and services company that offers state of-the art, modern solutions at a lower cost, implemented in shorter time compared to competitors.
PiControl Solutions is the only process control and automation company in the world which can perform any advanced process control (APC) project completely remotely. Nowadays, every country uses high speed and reliable internet connection and with a help of medium to high resolution cheap web-cameras or even over widely used remote meeting and screen sharing applications it is possible to do complete design, tuning and optimization, FAT test and start-up of any advanced process control project. Over this low cost online/remote approach huge travel and accommodation costs can be saved and human health and safety can be kept on the high level.
For more information and details, please send us an email: info@PiControlSolutions.com or call the Tel: (832) 495 6436.