Analysis of technical upgrades for atmospheric and vacuum distillation units: Energy consumption analysis of switching from multi-stage steam jet pumps to steam jet pumps + liquid ring vacuum pumps [
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The top of the vacuum distillation tower employs a hybrid vacuum extraction system that combines high-efficiency jet steam evacuation with mechanical vacuum extraction, thereby saving energy while ensuring the desired vacuum level at the tower top. The designed operating pressure at the top of the vacuum tower is 12 mmHg (absolute). The vacuum extraction system for reducing the roof pressure currently typically uses a steam-based vacuum system, which requires less maintenance and offers high reliability ； However, for large-scale installations, mechanical vacuum pumping systems demonstrate their economic advantages, offering significant energy savings and reduced consumption. The vacuum tower at the top of this unit employs a hybrid vacuum extraction system that combines high-efficiency jet steam vacuuming with mechanical vacuuming. The comparison data compared to a system that uses solely steam for vacuuming is as follows: Hybrid vacuuming system vs. Pure steam vacuuming system: 1. Investment: RMB ten thousand + 180 versus baseline; 2. Steam consumption: tons per hour – baseline + 7.63; 3. Electricity consumption: KW – baseline + 160; 4. Circulating water usage: tons per hour – baseline + 100; 5. Softened water usage: tons per hour – baseline + 3.0; 6. Energy consumption per ton of crude oil: –0.4413 kg of standard fuel versus baseline; 7. Operating costs: RMB ten thousand per year – 337.6632 versus baseline; 8. Payback period for the initial investment: 0.533 years. As can be seen from the table, the hybrid vacuuming system saves 0.4413 kg of standard fuel per ton of crude oil compared to the pure steam vacuuming system, with a payback period of only 0.533 years. Therefore, it is economically reasonable for this device to adopt a mixed vacuum pumping system.
Mixed vacuum pumping scheme; Full water vapor vacuum pumping scheme. 1. Investment: 10,000 RMB + 180 (baseline). 2. Water vapor consumption: tons per hour – baseline + 7.63. 3. Electricity consumption: KW – baseline; tons per hour + 100 (baseline). 4. Circulating water. 5. Softened water: tons per hour – baseline + 3.0. Is the value in the bolded row reversed? The water ring pump requires water replenishment.
4. The value in the circulating water column is also written backwards; it should be +100 for all steam ejectors, with the value corresponding to the ejectors and liquid ring pumps serving as the baseline.
Two-stage steam before, one-stage circulation pump after
To be honest, not all aspects of this approach in vacuum distillation processes necessarily lead to reduced energy consumption. Theoretically, based on mere data comparison, it is indeed more energy-efficient to use a water ring + steam injection system compared to steam injection alone. However, petrochemical companies generally do not lack low-quality steam – failing to use it would mean wasting it, and since it’s already a waste, why not make use of it? If costs are not taken into account, then steam injection is the more energy-efficient option!