Lube-Tech PUBLISHED BY LUBE: THE EUROPEAN LUBRICANTS INDUSTRY MAGAZINE
separated and removed from the lube base oil as the wiped film evaporator bottom product, asphalt flux.
The CEP design includes poison ‘traps’ that absorb the poisons at the entrance to the first reactor that results in increased catalyst life. The combination of these improvements along with the catalyst management program allowed the semi-works plant to achieve exceptional 11-month run in 2010 and 2011. CEP’s customers have reported catalyst runs lasting more than 12 months using the catalyst management program.
Out of this work, CEP now offers its own brand of catalysts most suitable for re-refining of drain oil. In addition, CEP is also able to predict the yields and product properties for ‘wild’ feedstocks and determine required operating conditions to achieve pre-set goals. This is especially important in countries where virgin lube oils don’t have upgraded properties similar to the USA and Europe.
The CEP process can now be built economically using pre- fabricated modules. In a recent CEP project, the ‘Front End’ recovery process utilised these modules to save overall construction cost. The ‘Front End’ process refers to the lube oil recovery process prior to the hydrotreating process. Now, the entire process including the hydrotreating process is available using appropriate process modules, saving capital cost while minimising the risk of cost overruns.
Hydrotreating In order to achieve the best hydrotreating technology, several advancements had to be made. The challenge in the hydrotreating process of used oil is that it is very difficult to sustain operations without frequent catalyst change-outs. Some re-refineries have ‘guard beds’ to function as sacrificial reactors to the main catalyst reactor. These guard beds tend to last typically one to three months at a maximum before switching over to another guard bed reactor. Having extra guard bed reactors increases the capital investment as well as requiring more maintenance. In the hydrotreating step, CEP designs according to mathematical models developed by MAGNA Associates.
Entering the real data with the precise analyses of the feed and discharge of each reactor of the three-in-line allowed us to adjust the models for differences in catalyst activities and unit peculiarities. The desulphurisation/deactivation model allows operators to optimise the hydrotreating reactor temperatures in each reactor to achieve the optimum life for the three beds. This also helps balance the deactivation rate of the catalysts to achieve the same run lengths for all three reactors in series. The examples below illustrate how the predictions of the mathematical models match the operating data for the three hydrotreating reactors.
Modeling of CEP Hydrotreaters Results of a review and analysis of Evergreen Oil’s operation in 2004 are presented in Figures A, B and C. In Figure A, observed and predicted performance data are displayed for Reactor R- 301. Metals loading is an indication of foulant embedded onto the catalyst, which decreases activity.
24 LUBE MAGAZINE No.111 OCTOBER 2012
Observed and predicted data for R-303 are shown in Figure C. The metals loading of this catalyst was 7.6% after 172 days of operation. Sulphur retention for this reactor varied between 25% and 40%. A comparison with reactors R-301 and R-302 shows quite clearly the increase in desulphurisation. This is due to the higher temperature in R-303. There is generally good agreement between observed and predicted data.
Catalyst activity comparisons are only valid for the same reactor. Catalyst activities for each reactor serve as a guideline to help predict product specifications. Agreement between commer- cially observed and predicted performance is generally quite good.
The metals loading of this catalyst was 8.9% after 172 days of operation. Sulphur retention (the amount of sulphur remaining in the oil) for this reactor varied between 65% and 85%.
Observed and predicted data for R-302 are shown in Figure B. The metals loading of this catalyst was 7.9% after 172 days of operation. Sulphur retention for this reactor varied between 65% and 85%. There is generally good agreement between observed and predicted.
Figure B Evergreen Desulphurisation R-302 Figure A Evergreen Desulphurisation R-301
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