Concerning some of the previously mentioned numbers, an average refinery should be consuming something like 9% of its crude oil throughput as energy. Energy is one of the biggest controllable costs in the refining business going up to 50%. Ninety percent of energy demands in this average refinery are provided by fuels either from fuels produced or imported. The remaining 10% of that energy demand is imported electricity. The final energy needs are divided between heat with 80% and the remaining 20% being power demand. Heat is released in fired heaters for direct process use and these account for almost 50% of overall energy demand, and boilers supply the other 30%. Burnt fuels from self-production that provide the basic energy for heat are mostly refinery fuel gas, FCC coke and some residual fuel. Natural gas is also a major fuel supply for most refineries, considered here as an import. Adding all typical fuels, refineries are mainly gas consumers, summing refinery gas and natural gas flows, going up to 70% of energy demand. Power is supplied by electricity, purchased or generated inside the refinery and steam, and these three power sources share almost evenly the demand.
Steam is usually distributed at least three pressure levels, mostly superheated. The highest commonly drives electricity generator steam turbines. The second high pressure, is used in steam turbines alternatively with electricity, to move most of the sensitivity equipment, like the FCC blower, distillation units main pumps and others. The lowest pressure usually has the lowest superheating quality and normally matches the required temperature for general heating and stripping demands. Actually, there can be more steam levels even up to ten, many of them ranging only in some areas and units, directly related to minor uses as stripping or heating for some special process. Generally steam represents something like 20% of final energy use, but is responsible for most of the scattered energy losses, particularly in the distributing system.
These figures indicate that a good energy balance must be accurate around fired heaters and boilers, because they deal with the bigger share of energy released in the refinery. Precision on steam balances, specially on the main pressure levels cover another significant amount of energy. Any loss detection and recovery on these systems should be significant. But these are just normal figures, an overview of a general refinery is fundamental to learn about the installed processes and that depends on each refinery's particular configuration.
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