Design for reducing the load on vacuum pumps due to secondary condensation of steam in negative pressure evaporation
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This post was last edited by Young people_l2Z7m on 2023-7-12 22:45. Application features: long-path condensation, coiled tube heat exchangers, spiral wound tube heat exchangers, fully welded stainless steel heat exchangers, spiral long-path design, capillary heat exchange tubes； In three-effect or four-effect evaporation, a vacuum system is essential at the tail end to create a negative pressure on the material side; only in this way can the temperature difference be controlled through pressure differences, thereby achieving energy savings through continuous multi-effect evaporation. In production, this approach is used to achieve process upgrades that result in reduced energy consumption ； Thoroughly condensing the secondary steam in the exhaust gas of the surface cooler reduces the workload on the vacuum pump at the back end, representing another way to achieve energy savings in this operation. With the current design and operating methods of the equipment, high-power, high-flow vacuum pumps are required to carry out evacuation tasks on a continuous basis; as a result, there is significant waste of electrical power. After upgrading the equipment and enhancing the condensation of secondary steam, thereby reducing the proportion of condensable steam in the exhaust gas, it is possible to reduce the volume of gas handled by the vacuum pump by 90% in currently sealed evaporation systems. The power consumption of the motors also decreases by 90%, which translates into a reduction of more than 75% in the overall electrical power required for production ； It offers significant energy-saving effects, in line with the principles of green chemistry and energy-efficient production ； The condensation of positive-pressure steam differs from that of negative-pressure steam ； Positive-pressure condensation can achieve complete condensation as long as the required heat transfer for condensation is met ； Negative pressure condensation is different, as the continuous evacuation at the tail makes overall condensation a difficult task in the first place ； Negative pressure condensation can only be observed directly in a laboratory setting, after ensuring that all non-condensable gases within the container have been completely removed ； Under production conditions, it is inevitable that non-condensable gases will be present and accumulate, and a negative pressure level must be maintained stably. To meet the requirement for deep condensation of vapor under negative pressure, the most common approach in production is to extend the condensation heat exchange process, thereby increasing the time spent on vapor heat exchange as well as its proportion in this process ； More detailed content will be added later; it’s too late today, time to go to bed. Those who are interested can add me on WeChat or send me a private message to learn from each other and communicate ；
In negative pressure evaporation, to reduce the workload on the vacuum pump, the following design measures can be adopted: 1. Fully condense the secondary steam: By increasing the area of the condenser, improving the structure of the heat exchanger, and raising the temperature of the cooling medium, the secondary steam can be condensed as much as possible, thereby reducing the load on the vacuum pump. 2. Extend the condensation heat exchange time: Increasing the time for condensation heat exchange can reduce the load on the vacuum pump. This can be achieved by increasing the flow rate of the cooling medium or extending the time that the steam stays in the condenser. 3. Add positive vacuum equipment: To meet the requirements of continuous vacuum pumping and maintaining a stable negative pressure level, positive vacuum equipment can be added at the rear to assist with continuous vacuum pumping. This can create a stable negative pressure environment, which helps to thoroughly condense the vapor under negative pressure. Through the combined application of the above measures, the operating load of the vacuum pump can be effectively reduced, thereby achieving the goal of energy savings and consumption reduction in the negative-pressure evaporation process. .
I fully agree with your viewpoint; we have essentially followed this approach by first upgrading the process equipment under the existing operating conditions. The equipment we designed includes a steam condensation process that enables thorough condensation of the steam, thereby reducing the volume of vapor that needs to be pumped away by the vacuum pump, which is then responsible only for removing the non-condensable gases； :victory:
The condenser is a key component in multi-effect evaporator systems; if its area is too small, it will not be able to condense the secondary steam from the last effect, which leads to a decrease in vacuum level and disrupts the entire system. Insufficient flow of cooling water can also result in a drop in vacuum level and disrupt the system. The size of the condensation area must be determined through calculations, and reducing the steam flow rate is related to the number of baffle plates as well as the pressure of the secondary steam. The length of the cooling water channel is related to the number of stages of the condenser, so it needs to be calculated as well: lol