163- Design plan for technical upgrading of the dry gas liquid separation tank in heavy oil catalytic cracking units using feather leaf separators

Through discussions with technical managers of heavy oil catalytic cracking units at refining and petrochemical companies, as well as engineers from design institutes, we learned that the process package technology used in domestic heavy catalytic cracking units remains largely at the level of the 1980s and 1990s, with almost no technological upgrades having taken place. As separation technology devices that play an important role in petroleum refining units, the vast majority rely on traditional components such as \"packings\" and \"screens\".

The reason for this is, on the one hand, limited by the technical conditions of that time – there were simply no better technologies available to offer more options； Furthermore, the owner was not very familiar with the technical standards of the process package at that time, so the design institute simply copied the drawings over and over again, making only changes to the project name and dates to get things done, which saved time and effort. Today, competition in the petrochemical energy market is becoming increasingly fierce. If companies do not take proactive steps to upgrade and modernize their old technological installations, they will be unable to achieve advantages in terms of operating costs as well as comprehensive economic and environmental benefits. This forces companies to find ways to technologically upgrade their older facilities.

Through discussions with technical personnel from refineries’ heavy oil catalytic cracking units and design institutes, it was learned that there are many industrial devices for which technical upgrades and renovations are urgent; some examples are as follows: 1) Fluidized bed catalytic reactor cyclone separator； 2) Regenerated flue gas cyclone separator ； 3) Fractionator overhead gas-liquid separator ； 4) Dry gas liquid separation tank ； 5) Demister at the top of the desorption tower ； 6) Separator tank at the compressor outlet ； 7) Oil-gas separator at the compressor outlet ； 8) Inter-stage condensate tank of the compressor ； 9) Oil-gas separator at compressor inlet ； 10) Demister at the top of the stabilizer ； 11) Demister at the top of the reabsorption tower ； 12) Demister at the top of the absorption tower ； 13) Regenerated steam separator ； 14) Waste heat boiler drum and demister ； 15) Torch gas separation tanks, etc. In earlier years, there was insufficient understanding and inadequate emphasis on gas-liquid separation in these units. In some units, either no internal components for gas-liquid separation were installed at all, or merely wire mesh demisters were simply arranged. Whether these measures actually fulfilled their role in gas-liquid separation is something that only the on-site operating and management personnel of the plant can determine.

Next, we will discuss the design plan using as an example a case where a petrochemical company requested us to carry out a technical upgrade of its dry gas liquid separation tank in the heavy oil catalytic cracking unit by installing vane separation technology equipment.

This dry gas liquid separator tank (KO tank), which requires technical upgrading, has the tag number M-212. Initially, this unit used a wire mesh demister installed directly on the radial cross-section at the top of the tank, but its separation efficiency was low, and the dry gas exiting it contained significant amounts of liquid hydrocarbons. The owner later carried out technical modifications by installing filter element filters. Although the separation efficiency improved significantly, the filter elements tended to become clogged due to the accumulation of tar-like substances, resulting in a rapid increase in operating pressure drop. This required frequent replacements, leading to high demands in terms of operation and maintenance as well as elevated costs. It was necessary to carry out another upgrade using low-dropout, high-efficiency, long-life vane separator technology.

The operating conditions of the dry gas separator provided by the owner to our party are as follows: 1. Continuous phase of the medium: dry gas； 2. Medium dispersed phase: Gas condensate ； 3. Continuous phase flow rate, Nm3/h: 60 ； 4. Operating temperature, °C: 50–100 ； 5. Operating pressure, MPa(g): 0.4～0.7 ； 6. Gas phase composition (volume percentage): Hydrogen 91.03, Nitrogen 1.82, Methane 1.64, Ethane 2.19, Propane 1.73, Isobutane 0.80, n-Butane 0.48, Hydrocarbons with more than 5 carbon atoms 0.30.

The client has requested that we use the vane separation technology to redesign and manufacture a brand new dry gas separator tank, to be connected in parallel to the existing pipeline, in order to replace the current dry gas separator tank while making use of its existing structure. The client required Nuowei Energy Technology Company to use precise dynamics separation technology to calculate and configure the system platform, to improve and supplement the material property data before proceeding with the design; the separation efficiency was required to be no less than 99%, with a permissible pressure drop of ≤20 kPa during cleaning and ≤50 kPa in the case of scaling.

The main technical information regarding the aforementioned vane-type separator for dry gas dewpoint control, which was developed by our company for the client based on operating condition data and under stringent conditions, using NOVEL’s precise dynamics separation technology for calculations and configuration design of the system platform, is as follows: 1. Type of separator technology: Vane-type separator； 2. Separator model: P4S-20-45; 3. Pre-allocated coalescing internal component set model: G50D20 ； 4. Model of the precision lobed separation internal components: P4S-EDP-12-125; 5. Material: Shell made of SS304/internal components made of SS316L ； 6. Separation efficiency: 99.9% @ 8.57 microns and above ； 7. Operating pressure drop: 0.14 psi (~0.97 kPa).

The image below shows the pre-allocated coalescing internals set:

This post was last edited by luoli519 on 2024-4-7 at 11:02. The images of the P4S type precision vane separation internal component set are as follows: