139- **The exhaust gas absorption tower of the unit is designed with a vane separator as a technological upgrade to replace the wire mesh demister and bubble breaker.**

**For the design of such devices, there are only a few companies in China that can do it. The design capability of the design agency, as well as its familiarity with new technologies and processes, determine the level of technical equipment required for a given **installation, its operation and maintenance costs, the economic efficiency of the project, and its environmental impact. The **system** discussed as an example in this post belongs to the mid-to-high capacity category in China. The core of the discussion concerns this **equipment exhaust gas absorption tower; its process diagram is as follows:

After being initially cooled and separated in a scrubber tower, the oxidized exhaust gas is mixed with alkane-containing inert gases from the cyclohexane distillation system and sent to the bottom of the absorption tower. The bottom pump of the absorption tower transfers the liquid from the tower bottom to the absorption tower circulation cooler for cooling, and then sends it to the middle part of the tower. **The mixture with cyclohexanol flows downward through the packed bed, absorbing cyclohexane vapor from the rising gas. The exhaust gas is discharged to the high-point vent of the flare header after passing through the foam breaker at the top of the tower, while the material from the bottom of the tower is sent to the saponification unit under pressure.

The last edit to this post was made by luoli519 on 2019-12-5 at 16:04. **The function of the absorption tower in high-pressure systems is to use** a mixture of this substance and cyclohexanol for spraying, in order to absorb the oxidized exhaust gases containing saturated cyclohexane that are generated by the oxidation system. **The cyclohexanol stream is provided from the alcohol dehydrogenation system; it is sent to the cryocooler by a feed pump in the absorption tower, and then enters the top of the absorption tower. The attached figure is an excerpt from the original absorption tower drawings provided to us by the owner:

This post was last edited by luoli519 on 2019-11-18 at 19:30. This set of absorption towers was designed by a company in Hunan. The total diameter of the tower is 1600 mm, with two sections of random packing; the height of the upper section is 5000 mm (including the distribution packing) ； The height of the second section is 4000 mm (including the distributed packing). At both ends of the two sections of packing, 200 mm high 250Y structured packing is used as distribution packing to serve the functions of distribution and support. A trough-type liquid distributor was originally installed at the top of the filler, while collection-type liquid distributors were used to redistribute the liquid between various layers of the bed. The packing layer is equipped with packing compression rings and packing supports to limit and support it.

This set of **exhaust gas absorption towers operates at a temperature of 10°C and a pressure of 1.05 MPaG; it constitutes a high-pressure absorption system. The gas handling capacity is 15,000–17,000 Nm^3/h. As shown in the absorption tower drawings earlier, this is an absorption tower with a diameter of 1600 mm. The exhaust gas outlet pipe is located at the top of the tower; its diameter is only 200 mm. Inside this outlet pipe, there is a wire mesh demister whose cross-sectional area accounts for only 1/4 of that of the absorption tower, and whose thickness is approximately 150 mm. Moreover, the inlet pipe of the absorption liquid is only about 1000 mm away from the bottom of the wire mesh demister.

This post was last edited by luoli519 on 2020-1-9 at 15:57. In the face of conditions characterized by high flow rates and difficulties in gas-liquid separation, the design team opted to install a wire mesh demister with a diameter of 800 mm at the top of an absorption tower with a diameter of 1600 mm; moreover, the distance between this demister and the outlet pipe, which has a diameter of 200 mm, is less than 450 mm. Such a design approach is typically what domestic design teams use, relying on experience, rough estimates, or even hunches to carry out the design. Since gas-liquid separation belongs to the category of kinetic separation technologies, accurate kinetic separation calculations and a tailored system platform are necessary in order to obtain a complete and reliable design scheme as well as precise dimensional data. Unfortunately, the design firm produced these wire mesh demisting separation drawings based on experience, on \"rough estimates\" and \"guesses\", or even on hunches. The owner reported that \"the gas-liquid separation efficiency in the exhaust gas absorption tower of our company’s high-pressure equipment is poor. The mixture of ** and cyclohexanol, which is used as the absorbent, cannot be effectively recovered by the mist catcher inside the tower; as a result, it ends up in the flare pipeline along with the exhaust gases, with a liquid flow rate of around 100 kg to 200 kg per hour.\" At the current market price of **/cyclohexanol, how much high-value product is being burned up each day? ? ?

This post was last edited by luoli519 on 2019-12-5 at 16:06. It’s heartbreaking for the owner to see so many treasures burned down every day. They approached the **Engineering Research Center for Advanced Distillation Technology** at Tianjin University, hoping to upgrade the absorption tower technologically. The attached drawings are excerpts from the technical upgrade plans for this absorption tower, prepared by the **Engineering Research Center for Distillation Technology at Tianjin University:

The main contents of the plan from the **Engineering Research Center for Advanced Distillation Technology at Tianjin University are as follows: 1. Replace the upper packing with Intallox25, and the lower packing with Intallox38; at both ends of each section of packing, 200mm-high 250Y structured packing will be used as distribution packing to serve the purposes of distribution and support. 2. The originally installed trough-type liquid distributor at the top of the filler was replaced with a tray-type distributor, and a collection-type liquid distributor is used to redistribute the liquid between various bed layers.

This post was last edited by luoli519 on 2019-11-19 at 18:25. The Tianjin University Distillation Technology **Engineering Research Center specializes in mass transfer and separation processes that occur under conditions of thorough mixing between gas and liquid. Therefore, its technical upgrades to the aforementioned C-51501 absorption tower focus on improving the packing material and the liquid distributor. It can also be seen that the **Engineering Research Center for TianDa Distillation Technology did not carry out any other necessary technical upgrades to the wire mesh demister located at the top of that absorption tower beyond thickening the wire mesh by 50 mm. The reason for this is that the strength of this research center lies not in the field of phase separation under conditions of incomplete mixing between gas and liquid phases; its theories, engineering practices, and design models are quite different in this regard.