Non-condensable gas from diesel hydrogenation vacuum tower

The situation mentioned by the original poster has been discussed by other forum members on the Haichuan Chemicals Forum as well; I have provided detailed responses to those inquiries, which can be found on the Haichuan Chemicals Forum. The problem mainly lies in the gas-liquid separation tank. The gas-liquid separation performance is not satisfactory, resulting in oil carried in the gas phase ； Whether the medium temperature is high or low, if the gas-liquid separation effect is poor, oil-contaminated gas will enter the vacuum pump or even escape outside the system. There are two reasons analyzed for the low efficiency of gas-liquid separation: First, the separation internals become clogged, which significantly reduces the efficiency of foam removal in the gas phase and leads to severe oil carryover in the gas phase. Secondly, the liquid level control inside the separator is set too high. Or both. However, the separator level is monitored by on-site level gauges as well as remote level control, so it generally does not exceed the set level, unless the level control system fails ； Therefore, the issue of separated internal components is the main suspect. In a vacuum distillation system, the direction of vacuum transfer is: from the vacuum pump to the gas-phase outlet side of the separator, then to the gas-phase inlet side of the separator, followed by the condenser, and finally to the top of the distillation column. Therefore, the direction of absolute pressure transmission is the opposite: the absolute pressure is highest in the distillation tower, and then it decreases sequentially in the order of the condenser, the gas-phase inlet side of the separator, the gas-phase outlet side of the separator, and the vacuum pump. When the separator uses traditional mesh or fiber-type demisting internals, the limited operational flexibility leads to large fluctuations in gas flow rates, which can cause flooding. Additionally, the flow channels of these demisting internals may become blocked by particles and viscous substances, resulting in an increased pressure difference across the inlet and outlet sides of the gas phase in the demisting separator. The absolute pressure on the gas inlet side of the separator is high, while the absolute pressure on the gas outlet side is very low. The liquid at the bottom of the separator is connected through the bottom area; according to the principle of communicating vessels, a high liquid column must be formed in the downcomer of the demister assembly to create static pressure that compensates for the low absolute pressure at the gas outlet side of the separator, thereby achieving equilibrium. As a result, the liquid column in the downcomer becomes very high, and in some cases it even fills the entire downcomer, leading to a siphoning effect. At this point, the separator not only has a low efficiency in separating gas from liquid and removing foam, but the liquid that has been separated can even be ‘siphoned’ into the gas outlet side of the separator, and may even be carried by the gas flow to the vacuum pump and outside the system. Due to oil in the vacuum lines and vacuum pumps, the system’s vacuum level inevitably fluctuates and decreases, which in turn causes fluctuations in the operation of the condenser and distillation tower. Currently, devices both domestically and internationally are adopting the high-efficiency vane-type gas-liquid demisting and separation internals technology to upgrade the traditional screen-type and fiber-type barrier separation demisting internals used in vacuum systems. This approach overcomes the shortcomings of conventional demisting separators, such as easy clogging, limited operational flexibility, high operating pressure drops, low efficiency, and the need for maintenance and replacement of the internals. For more information on related high-efficiency air-liquid demisting and defoaming separation internals based on the vane design, please visit the HaiChuan Chemicals Forum at the link http://bbs.hcbbs.com/thread-1354814-1-1.html. For more detailed technical upgrade plans, please contact professional separation technology companies directly.