149- Analysis of the suitability of cyclone liquid separators and vane separators as internal components for the gas-liquid separation unit in the hydrogenation plant’s cycle hydrogen desulfurization tower

This post was last edited by luoli519 on 2020-4-14 at 18:14. Gas-liquid separation in the circulating hydrogen desulfurization tower of hydrogenation units is a technical challenge that petrochemical companies cannot bypass. Novae Energy Technology has received requests for technical solutions regarding hydrogenation projects from owners and designers of petrochemical plants. These projects include hydrocracking units, catalytic diesel hydrogenation reforming units, heavy oil hydrogenation units, residue oil hydrogenation units, and hydrogenation refining units. The selection of components for gas-liquid separation is required in various parts of these systems, such as the cold high-pressure gas-liquid separation tanks, the liquid separation tank at the inlet of the recycled hydrogen desulfurization tower, and the top liquid separator of the recycled hydrogen desulfurization tower. A wire mesh defoamer, a cyclone liquid remover (cyclone amine remover), or a vaned separator?

In the UOP hydrogenation unit process package, UOP continues to use the most traditional wire mesh demisters. Please refer to the structural dimension diagram of the hydrogenation unit’s cycle hydrogen desulfurization tower provided in the attached diagram; at the two locations indicated by red circles, it can be seen that the most traditional wire mesh demister is still being used.

Undoubtedly, the wire mesh demister is the simplest and most basic component for gas-liquid separation technology. Not to mention that the various types of wire mesh demisters available in China, with their different parameters, do not perform well in the separation process within hydrogen circulation desulfurization towers; even when using the original imported YORK standard series of wire mesh demisters, there is not much improvement in their separation performance. The structure and separation mechanism of the mesh demister determine that its operating flexibility is typically within the range of 60–110%, or even lower; the separation efficiency varies greatly, and phenomena such as \"liquid flooding\" and \"liquid surging\" can occur. The gel-like substances and particles carried by the airflow can easily clog the mesh, leading to a sharp increase in pressure drop, which results in high operational and maintenance costs.

This post was last edited by luoli519 on 2020-4-14 at 18:09. Given the actual problems encountered in the operation of wire mesh demisters in the recycle hydrogen desulfurization towers of many domestic plants that use UOP hydrogenation process packages, several petrochemical companies and design institutes have turned to us for assistance with kinetic separation technologies, hoping to use internal components similar to those found in multi-tube cyclone separators used in heavy catalyst units in the petrochemical industry in order to improve the performance of the wire mesh demisters in these processes. Around 2007, based on the process parameters provided by the design institute and the client, we completed the system design using a configuration design system platform powered by precise dynamics separation technology, and provided this petrochemical company as well as the design institute with cyclone separation solutions and equipment that were tailored to their specific operational conditions. Since then, under the guidance of that design institute, many new construction or renovation projects have involved replacing the cyclic hydrogen desulfurization towers with cyclone separation internals. However, since the first set of cyclone separation solutions and equipment designed based on a \"one-to-one customization for specific operating conditions,\" no design institutes or clients have since approached us for technical support and improvements for devices intended for different operating conditions and configurations. This is equipment based on precise dynamics separation technology; for devices operating under different conditions and with varying gas-liquid compositions, a system platform designed through precise dynamics calculations is necessary to achieve reliable separation results. Is it sufficient to simply address the “clogging” issue of the original wire mesh demister, without paying too much attention to the separation efficiency? If that’s the case, why not simply remove the screen defoamer to achieve the goal of \"resolving clogging without having to worry about separation efficiency\"? I once discussed this situation with the personnel from the process package supplier, and everyone couldn’t help but laugh.

It is understood that those who develop plans based on \"rough estimates\" or even sheer guesswork are not only sales-oriented companies at home and abroad, but also many design firms. The reason why it’s possible to get by by designing system platforms without using precise dynamics separation techniques, and by relying instead on ‘rough estimates’ or even arbitrary decisions, is often because the clients don’t understand the technology well enough. Although owners may be deceived due to their lack of understanding of separation techniques during the design phase of the installation, problems such as unstable separation efficiency, significant liquid carried in the gas stream, and liquid accumulation in pipelines that cause flow resistance during actual operation of the installation serve as clear indications that there are issues with the installation!

The cycle hydrogen desulfurization tower of the hydrogenation unit at a petrochemical plant in the northeast was not operating properly, so the plant commissioned a design institute to carry out technical renovation designs. This design institute also used a so-called \"cyclone dehydrator\" to upgrade the technology of the circulating hydrogen desulfurization tower. However, the design institute did not seek out specialized companies with dynamic separation technologies; instead, people relied on ‘rough estimates’ and ‘guesswork’” ； Yet, worried about the uncertainty regarding the effectiveness of technical upgrades for such a system, they decided to add a wire mesh demister to the so-called \"cyclone liquid separator\". :lol

This post was last edited by luoli519 on 2020-4-14 at 18:11. The attached document is the MR file prepared by a certain design institute for the technical renovation of the circulating hydrogen desulfurization tower in a petrochemical enterprise’s hydrogenation unit, in which a so-called \"cyclone liquid remover\" was used. The area marked in red represents the technical requirements set by that design institute – requirements that are based on approximations and estimates, as well as hasty decisions; since they were unsure about the effectiveness of the proposed technical modifications, they simply added a wire mesh demister to what is known as the \"cyclone liquid separator\". Instead of doing that, wouldn’t it be even more irresponsible to simply adopt the \"mesh demister\" from UOP’s hydrogenation unit cycle hydrogen desulfurization process package as is?

That’s all for the screen defoamer. Next, a design example is used to conduct a comparative analysis and discussion on the selection of design for the \"cyclone dewaterer\" and the \"vaned separator\".

This post was last edited by luoli519 on 2020-4-14 at 20:34. It presents the selection and design of the gas-liquid separation internals for the cyclic hydrogen desulfurization tower (2401-C-0101) in a 3.7 million tons/year hydrocracking unit. The properties of the feed at its upper part are as follows: 1. Operating temperature: 52℃ ； 2. Operating pressure: 16.6 MPaG ； 3. Rated gas flow rate: 226565 kg/h ； Initial flow rate: 205968 kg/h ； Final flow rate: 183,334 kg/h; 4. Average molecular weight of the gas phase: 3.3; 5. Gas phase composition: hydrogen, amine solution, water, and a small amount of hydrogen sulfide; gas phase density: 17.71 kg/m^3 ； 6. Oil phase flow rate: 0.05 kg/h ； 7. Oil phase density: 956 kg/m^3; 8. Oil phase viscosity: 0.522 cp ； 9. Surface tension of the oil phase: 0.065 N/m.

This post was last edited by luoli519 on 2020-4-14 at 18:39. The main separation technology requirements proposed by the design institute are: 1. Operational flexibility: 60-110%； 2. Maximum allowable pressure difference: 10 kPa; 3. The d50 particle size of droplets at the gas phase outlet is not greater than 3 microns, and the proportion of components with a molecular weight of C5+ is also not greater than 3 microns; furthermore, the removal rate of droplets with a size of 5 microns or more is approximately 95% ； 4. The cyclone must ensure that the cyclone tube can be disassembled and assembled, and pipe blocking should be carried out if necessary.