Managing fouling in oil refineries requires a proactive and systematic approach to monitoring, cleaning, and mitigating the accumulation of deposits. The use of digital solutions, such as predictive maintenance and advanced monitoring, can help to minimize the negative impacts of fouling and ensure consistent and efficient refining operations.
Preheat trains in CDUs are key processes for the energy efficiency of the refinery. These extensive networks of heat exchangers aim to recover up to 70% of the energy required to preheat crude oil before entering the distillation column by exchanging heat with the hot streams coming out from it. The rest is provided in furnaces by burning fuel, normally natural gas. As fouling builds up in the train, the inlet temperature to the furnace (coil inlet temperature, CIT) decreases.
Additional fuel must be burned in the furnaces to maintain the desired inlet temperature to the distillation column (or coil inlet temperature, COT), which is critical to achieve the desired yields. If the furnace reaches the maximum capacity, the plant throughput must be reduced to meet the desired COT, leading to significant economic losses. In other cases, the hydraulic impact of fouling, rather than the thermal, is the cause of throughput losses.
Hexxcell’s technology has been extensively applied to help reduce the negative impact of fouling in preheat trains by closely monitoring the condition of the network, predicting future scenarios, optimising operations and cleaning schedules, and uncovering the impact of crude oil blends on fouling propensity. For an average-size refinery (100,000 – 150,000 bbl/d), typical benefits of applying Hexxcell’s technologies include $1-2 M/yr savings in fuel, reduction of over 8-10% in CO2 emissions of the CDU, production increase of 0.5-3%, and total financial impact of several millions of dollars per year.
While the preheat train is the main actor in refineries, substantial benefits can be achieved in other processes, such as vacuum distillation units (VDUs) requiring preheat, preheaters in cokers or FCCs, auxiliary exchangers in stabilisers, etc.