Technical reform analysis of 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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Regarding atmospheric and vacuum distillation units, I have also seen in chemical plants many cases where steam jet pumps are used for vacuum creation at the top of the towers. However, the trend is to use a combination of steam jet pumps and liquid ring vacuum pumps in order to achieve energy savings and reduced consumption. Yet, no studies have been conducted to determine exactly how much energy can be saved in this way. I would like to ask my colleagues whether they have any information on this topic Please communicate more.
The top of the vacuum distillation column employs a hybrid vacuum extraction system that combines high-efficiency jet steam evacuation with mechanical vacuum extraction, thereby saving energy while ensuring the required vacuum level at the column 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, resulting in 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: 10,000 RMB + 180 (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. Equivalent energy consumption: kilograms of standard fuel per ton of crude oil – 0.4413 (baseline); 7. Operating costs: 10,000 RMB per year – 337.6632 (baseline); 8. Payback period for initial investment: 0.533 years. As can be seen from the table above, the hybrid vacuuming system saves 0.4413 kilograms 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.
Water ring pumps are more cost-effective; we can discuss this further if needed
For water ring pumps, it is crucial to control the water temperature in order to achieve a high vacuum level. We used reciprocating vacuum pumps before, which required a large amount of lubricant. Now we have switched to water ring pumps, but the water needs to be replaced frequently, and the water temperature must be controlled; the solenoid valves for water inlet and outlet also need to be operated often, resulting in more work for the operators compared to before. It would be even better if there were a good cooling method to control the water temperature.
We use a water ring pump in combination with steam for vacuum extraction. The water ring pump consists of a separation tank, a working fluid cooler, and the water ring pump itself; it operates quite stably, and it stopped working only once over three years due to an obstruction in the drainage path
May I ask, what was the vacuum level after it was stopped temporarily, and were there any dangerous situations such as backflow? How do you handle it? How long will it take to resume normal production?
Theoretically, it’s no problem to reduce energy consumption by 25%