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Currently we are facing problem of higher CO (Carbon Monoxide) and CO2 contents in the Net Gas (Net Gas is H2, produced in CCR Platforming Unit). This CO is affecting UOP's Penex Unit Catalyst. Please help finding out the source of CO & CO2 and guide how to reduce both in the Net Gas (our main focus is on reduction of Carbon Monoxide as it is a permanent poison for Penex Catalyst).

Jul-2022

Answers

Lance Baird, Lance Baird LLC, labaird@comcast.net

CO is formed by water-gas shift, but in the reactor, not the reduction zone because a source of carbon is required. In addition to water in the feed and recycle gas, the water adsorbed on the catalyst coming from the reduction zone is important. The following process variables will reduce the CO concentration; use whichever is possible in your particular circumstances:
- Reduce water in the recycle gas or feed
- Increase unit pressure
- Reduce unit temperature
- Reduce catalyst circulation
- Improve the drying in the CCR drying zone
- Use the modified UOP reduction gas flow scheme

Dec-2022
Robert Snell, The Quaker Group, robert.snell@thequakergroup.com

Reducing CCR severity will directionally reduce CO in reformer produced H2. Increased recycle gas rate should also suppress CO but at a higher cost. As the gentleman mentioned above reformer gas is designed as a by-product of a unit designed to increase refinery pool octane and/or petchem feedstock.

Nov-2022
Wim Elseviers, Technip Energies Netherlands BV, wim.elseviers@technipenergies.com

Net gas from a CCR indeed contains CO as explained by others already and this is well known. Did UOP accept this quality hydrogen to be sent to the isomerozation unit without having passed through a PSA unit first - the CO levels in CCR net gas typically do not meet the quality requirements for Penex process.

A PSA will remove CO but will also reduce the quantity of H2 as the recovery is not 100 %. However, UOP has several advanced process schemes to recover this H2 by recycling the tail gas. If you have high value for C3C4 fraction, treating the net gas through a PSA + RecoveryMAX system will enhance the hydrogen purity, recover a large fraction of the C3C4 in the net gas to LPG and recover up to 98 % of the H2 with CO levels below 1 ppm.

If this investment would be too expensive and Penex is not the only user of H2 from the net gas, you could consider installing a PSA unit only on the slip stream of the net gas to just produce the quantity of Hydrogen required for the Penex unit and mix the PSA tail gas back with the net gas to other consumers. PSA tail gas compression will be required, but the PSA tail gas pressure could be optimized to reduce power consumption - at the cost of lower H2 recovery, so the tail gas pressure cannot be increased to very high levels.

Another alternative is to take H2 from a hydrogen plant, as was also suggested. Reducing the typical 10-20 ppm CO in the product H2 from the HPU to 0.1-1 ppm CO required for the Penex unit, will lower the hydrogen production flow rate from the HPU by 0.5 to 1.5 % and increase the heating value of the PSA purge gas to the reformer, reducing the make-up fuel demand to the reformer.

Nov-2022
Roger Haglund, OCI NV, r_haglund44@hotmail.com

It originates in the reduction zone where CO is formed through reverse WGS. Had the same problem on a Cyclemax CCR back in 2006. We did replace the dryer in the CCR circuit but it did not have any effect.

We swapped the hydrogen supply to Penex from the CCR to the Steam reformer which had a lot less of CO in the hydrogen. One could notice the Penex deactivation to "disappear". Have operated other CCR after this and not seen the same problem with Hydrogen. Exactly why the CO is allowed to form is not clear.

Oct-2022
STEVEN MCMURRAY, PTT Global Chemical, StevenMcMurr@gmail.com

Higher than normal CO / CO2 in Platforming net has is usually a result of higher than normal moisture in the recycle gas. CO formation will follow the moisture. Check the usual suspects for this, including changing out the desiccant in the CCR air dryer package. But if this is an ongoing long term problem, then using PSA hydrogen would be the best solution. Also small in line methanators have also been employed for converting the CO in some instances.

Oct-2022
Marcelo Tagliabue, Air Liquide, marcelo.tagliabue@airliquide.com

I totally agree with Marcio answer. In the first place, the Platforming process itself provides a low purity H2, because it was fundamentally used to produce streams rich in aromatics and the H2 was treated as a by-product. If this H2 is to be sent to another process with catalysts sensitive to the CO and CO2, this stream must be purified. Traditionally, and with high H2 purity requirements, cold boxes were used for this purification. But this type of installation demands high investment and complicated operation.

Between absorption units with amines (MEA, MDEA) and the PSA process, I prefer the latter, due to the purity of H2 obtained (less than 10 ppm CO) and fundamentally due to the ease of operation.

Oct-2022
Sergey Glistovchenko, Slavyansk ECO, Sergey.Glistovchenko@gmail.com

1. Check oxygen in CCR feed.

2. Check water-chloride balance in CCR.

3. Be sure you don't have addition of SMR hydrogen into the Net Gas stream (for balance or make-up).

Aug-2022
Marcio Wagner Silva, Petrobras, marciows@petrobras.com.br

It's important to understand better the refining scheme adopted in your refining asset, from the question it seems that the Net gas from CCR Platforming is directly fed to the Isomerization Unit (PENEX Process). If the net gas is not fed previously to a PSA unit or another hydrogen purification unit it's expected a high concentration of CO and CO2 which are poison to isomerization catalyst. In this case, its necessary to study the economic viability to install a PSA or MEA treating unit aiming to reduce the CO and CO2 concentration in the Net Gas sent to the Isomerization unit.

Aug-2022