ble for significant emissions of CO 2 . Considering the trend for renew - ables co-processing in crude oil refineries, which tends to raise even higher the hydrogen demand, it is fundamental to minimise the energy intensity of the hydrogen production processes. This goal can be achieved through the following actions: • Hydrogen management is required to minimise burning it as fuel • Apply pressure swing adsorption processes (PSA) to improve the par - tial pressure and recycling of hydro - gen from process units • Maintain reliability of PSA units Closer integration between refin - ing and petrochemical assets is another tool to help downstream players optimise energy consump - tion. Refining assets are typically self-sufficient in steam and power generation, while they may be deficient in hydrogen generation, whereas petrochemical plants can export hydrogen but are deficient in power and steam generation. Thus, the synergy between refining and petrochemical assets can help the players to optimise their energy demand. Some alternatives that reduce the energy requirement in crude oil refineries involve capital invest - ments for either revamps or new plant. Revamping fired heaters and furnaces to improve efficiency and minimise greenhouse gas (GHG) emissions is a widely used option. The crude oil distillation unit is the largest energy-consuming unit in a crude oil refinery with many optimisation opportunities. Establishing an adequate overflash can save a large amount of energy in the fired heaters. For process - ing units with higher processing capacity, pre-flash configuration can reduce the energy intensity of the downstream steps of the process. Figure 2 presents a crude oil distilla - tion unit with a pre-flash column. An evolution of the pre-flash con - figuration is the progressive dis - tillation technology developed by Technip. In the conventional process, the lighter fractions are superheated, leading to energy wastage. To avoid this, the progressive distillation con - cept applies a series of distillation
Condenser
Air cooler
Gas
Fuel gas
Re ux
Sour water
Condenser
Pump
Heavy naphtha
Sour water
Stripper
Steam
Crude oil
Light naphtha + LPG
Kerosene
Pump
Atmospheric distillation tower
Stripper
Pre- fractionation tower
Heated and desalted crude oil
Steam
Light diesel
Fired heater
Pump
Stripper
Atmospheric gasoil (Heavy diesel)
Steam
Steam
Fired heater
Pump Crude oil
Atmospheric residue
Pump
Figure 2 Crude oil distillation with pre-flash column
• Determine optimal opportuni - ties to shut down and clean the heat exchanger network • Optimise pumparound flow rates Another high energy-consuming process is the hydrocracking unit; for these units, the following actions can help to reduce the energy intensity of the process: • Inspect and re-assess the structural integrity of reactor internals during The synergy between refining and petrochemical assets can help the players
best time to maximise the internal power generation in the refinery? These questions can be answered using adequate simulators, consider - ing key information such as natural gas cost, equipment availability, reli - ability, and the operating limits for critical processing units like the FCC. Among the consolidated tech - niques to optimise energy consump - tion, we can quote the use of Pinch analysis to reduce requirements for hot utilities in the processing units and maximise the energy recov - ery from the process. This option is especially attractive in crude oil dis - tillation, FCC, and delayed coking units as these are high energy-con - suming processes. The use of equipment load man - agement systems, monitoring speed for rotating equipment, thermal effi - ciency monitoring systems, control and monitoring the flare gas emis - sions, and flow rate measurements for gases discharged to flare systems can help to identify bad actors and promote effective actions to optimise power consumption in the process plant. Focusing on the high energy- consuming units, it is possible to consider the following option to deliver energy savings in crude dis - tillation units: • Monitoring thermal efficiency of heat exchangers
to optimise their energy demand
turnaround maintenance shutdown • Use low ΔP valves (mainly in com - pressor discharge) • Avoid the use of compressor con - trol through recirculation strategy In the face of stricter regulations over the last decades, crude oil refin - ing has become strongly depend - ent on hydrogen, which is normally produced through an energy-inten - sive route such as natural gas steam reforming, which is also responsi -
74 PTQQ 2 2022
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