PTQ Q1 2025 Issue

Process control and energy management in the 21st century Key online measurements and technologies for safe and optimal refinery operation, highlighting potential energy savings that can lead to reduced CO 2 emissions

Jochen Geiger AMETEK Process Instruments

R efinery working conditions are changing d ue to the increasing processing of sour crude oil as the avail- ability of sweet crude diminishes. As a result, refiners require more flexibility because, in addition to environmental impact monitoring, sulphur dioxide (SO₂) emissions have to be reduced without expending more energy (as this can increase overall CO₂ emissions). All of this brings significant challenges to the operators of a refinery. Behind the scenes, there is a growing focus on analyser solutions and the next generation of process instrumenta- tion, which will be reviewed with a specific emphasis on multicomponent/multisensor technologies and their corre- sponding process control improvements. The foundation of this methodology is a holistic perspec- tive on analyser design. Rather than adhering to one-size- fits-all solutions, analysers are tailored to each application. This careful customisation enhances accuracy and efficiency, ensuring a seamless fit. Along with this holistic approach is the integration of tai- lored sampling systems. Aligning analysers with sampling systems will mitigate potential complexities in sample condi- tioning systems. Streamlining workflows and boosting oper - ational fluidity, strategic technology selection is a hallmark of this methodology (see Figure 1 ). Measuring high sulphur-containing crude samples The supply of crude oil is becoming more challenging in several geographic regions. Crude compositions can change due to supply methods, which may shift from pipelines with a stable composition to ocean vessels with variable com- positions, requiring more refinery flexibility. In addition, it is essential to monitor the environmental impact and reduce emissions to comply with regulatory requirements. Maximum and minimum sulphur concentrations can vary between 1% and 6%. Not only are the chemical, catalytic, and thermal reactions within refineries dependent on stable crude oil, but piping specifications must also be considered regarding the maximum permitted sulphur concentration. For example, if a refinery is designed to operate at a sulphur level of 3-4% and the incoming crude is at 5.5%, a modified blending control system will be required. For many refineries, sulphur level measurements in the parts per million (ppm) range are an important part of the final product quality control system. When feedstock sulphur

concentrations are changing, it is necessary to measure the sulphur concentration in the crude oil itself. Not only is the incoming crude oil sulphur concentration different, but the viscosity of the crude will also alter, resulting in a change to the final product’s viscosity. When measuring the percentage level of sulphur in crude oil, the viscosity of the stream being introduced to the pro- cess gas analyser is one of the primary hurdles to overcome. In many cases, the fluid only remains liquid at temperatures >150°C, which is a challenging temperature for many com- plex process gas analysers. Therefore, selecting the appro- priate measurement solution is a critical consideration. Most existing online instruments are based on X-ray or ultraviolet (UV) fluorescence, which are analytical methods designed for low- and mid-level sulphur measurements in lighter sam- ple streams. For crude oil, heavy vacuum gasoil (VGO), residuals, or heavy bunker fuel, it has long been common practice to use instruments based on a radioactive detector technique. However, this has become increasingly difficult to select and implement, as it presents the system designers and end users with significant safety factors and complicated certifi - cation processes. An alternative method is X-ray transmis- sion, which offers the benefit of no permanent radioactive source, eliminating many of the safety concerns and certifi - cation issues. In addition, the entire measuring system is suitable for heavy fuels, as it can be maintained at temperatures up to 250°C. Almost no filtration is required to protect the meas - uring system from potential impurities in the stream. All this makes the blending control simpler, with lower mainte- nance requirements. Bunker fuel measurements occur quite far downstream in the refinery but have recently become more important as part of the global effort to reduce harm- ful emissions from points of use. Sulphur in bunker fuel can eventually be oxidised into SO₂ when burned and must be reduced. For a long period, bunker fuel was an extremely heavy fuel that only became a flowing liquid at high temperature and was expected to have high levels of sulphur. Since 2020, the International Marine Fuel Specification (ISO 8217:2024) has limited the sulphur concentration of marine bunker fuel to 0.5% (the previous limit was 4.5%). As a result, more accu - rate and controlled blending is required.

PTQ Q1 2025