By Iliana Colín, Emerson Gas Specialist for Analytical Measurements
Hello, I’m Iliana Colín and I’m your Analytic Expert today. I’d like to talk about some of the challenges associated with catalyst regeneration in catalytic cracking and how rethinking the approach to hydrocarbon monitoring in these processes can reduce risk and save you time and money.
Catalytic crackers have long been utilized to extract additional gasoline from heavier components resulting from the distillation process. The distillation process is the physical separation of a mixture of different molecules based upon the different boiling points of these molecules. The catalytic cracking process splits larger hydrocarbon molecules into lighter and higher value components such as gasoline by using a catalyst, which aids the reaction or “cracking” process. The cracking process produces carbon, or coke, which remains on the catalyst particle, reducing its effectiveness over time. Fluidized Catalytic Cracking Units (FCCU) will continuously route coked catalyst into a regenerator unit where oil remaining on the surface of the catalyst is stripped off with steam or solvent. The catalyst is then sent into the regenerator, where air is introduced to burn the coke off of the hot catalyst, usually in suspension. There are many different variations in the regeneration process: the semi-regenerative catalytic reformer and the continuous catalyst regeneration reformer (CCR). This last one is preferred because of the continuous regeneration of the catalyst, which allows plant operation for more than two years before a catalyst change is needed. This is important because the cost of the catalyst is very high.
One of the key parameters in the process is the purity of the nitrogen, which is required to move the catalyst from the reactor to the regenerator. The hydrogen content must be below 1% and total hydrocarbons must be below 15% in order to keep a non-explosive atmosphere in the process since high temperatures are needed. In addition, if hydrocarbons are burned they may lead to the formation of a coke lining over the catalyst, inhibiting its function, so monitoring is essential.
Challenges that arise in this application include the high quantities of dust due to the continuous flow of the catalyst that enables cracking. When older analyzers are used, it’s not uncommon for the dust to cause the sampling lines to plug, or even worse, damage the analyzer. This is often the result of a sampling system with inappropriate design for such a challenging environment. As a result, some plants use this as a reason to bypass the analyzer, and leave it without maintenance until it becomes useless. This is an extremely costly and dangerous approach, since the analyzer can signal a plant shut down, and if the signal is bypassed, the safety of the plant is threatened.
Also challenging is the fact that the area certification in these plants is classified as hazardous. This may drive users to install general purpose analyzers in high cost shelters that also require power supply, air conditioning, and safety devices. These shelters must be installed at floor level, representing larger tubing lines and the inherent time delay that affects the control of the application because the control system receives data with a delay of some minutes, and thus process safety is jeopardized.
Many analyzers currently installed on-site use analog outputs, and there is no way to know the status of the analyzer unless the tech is standing in front of it, which can be ill-advised in hazardous areas due to risks such as radioactive measurement of the flow rate of the catalyst moving bed, noise, height, and so on. New analyzers are able to send more information through a Modbus protocol to make the maintenance program of the analysis system easier.
A monitoring approach that can reduce risk and costs is to use an analyzer designed specifically for hazardous environments such as the X-STREAM Enhanced XEFD. Enclosed in a wall-mountable, flameproof housing certified for installation in CSA and ATEX hazardous areas, these modern analyzers offer communications protocols to keep the control room constantly informed of their condition as well as process feedback. The housing also means the analyzers do not require costly and space-intensive shelters, eliminating the need for additional utilities, such as power, air conditioning, etc. These systems offer the monitoring of both hydrogen and total hydrocarbons in a single analyzer, further reducing costs and time for installation, start up, maintenance and calibration. Because the systems are designed from the outset with very short sampling lines, which are far less likely to become plugged and have fewer fault points, analysis is faster and more reliable.
What kind of monitoring systems are you using in your catalytic regeneration processes? Have you experienced challenges?
By Rob Clemons, Sales Manager, PCE Pacific, Inc.
Hi. I’m Rob Clemons, Sales Manager for the Instrument and Automation Division of PCE Pacific, Inc. I’ve got a great customer story to share with you. Chances are, most of you don’t own cruise lines, but as you can imagine, cruise lines have very stringent water quality rules – both for potable water and for water used in recreational facilities like hot tubs. The Center for Disease Control (CDC) places strict regulations requiring the continuous measurement of both halogens, such as chlorine, and pH. So we’re very honored to have been selected by the unique cruise line, Un-Cruise Adventures, as their water quality measurement company. This selection might have implications for your application as well.
The analyzer that proved to be ideal for the Un-Cruise Adventures application is the 56 Advanced Dual Input Analyzer configured for FCL (free chlorine) measurement. The 56 is a benchmark in ease of use and met the stringent requirements of the CDC.
The CDC regulations regarding measurement of halogens states:
A HALOGEN analyzer-chart recorder must be installed at a distant point in the POTABLE WATER distribution system where a significant water flow exists and represents the entire distribution system. In cases where multiple distribution loops exist and no pipes connect the loops, there must be an analyzer and chart recorder for each loop. Potable Water; 48 126.96.36.199.2 Data Logger Electronic data loggers with certified data security features may be used in lieu of chart recorders.
Needless to say, the choice of an electronic data logger is far superior in terms of precision, ease-of-use, and reduction in maintenance time. The CDC specifications go on to say:
188.8.131.52 Operation 184.108.40.206.1 Maintenance. A manual comparison test must be conducted daily to verify calibration. Calibration must be made whenever the manual test value is > 0.2 ppm higher or lower than the analyzer reading. 220.127.116.11.2 Calibration (06) The daily manual comparison test or calibration must be recorded either on the recorder chart or in a log. 18.104.22.168.3 Accuracy (05) The free residual HALOGEN measured by the HALOGEN analyzer must be ± 0.2 MG/L (ppm) of the free residual HALOGEN measured by the manual test.
The built-in data logger of the 56 again saves time, and enhances accuracy.
Un-Cruise Adventures is using the 56 equipment to provide CDC-mandated chlorine and pH control of three public hot tubs as well as for ensuring CDC compliance with onboard potable water systems on two passenger vessels. Since pH measurement is part of the free chlorine measurement on the 56, the system saved both time and money. To accommodate Un-Cruise Adventure’s space requirement, the back-panel of the assembly was trimmed down on one side and the 56 analyzer re-installed in order to fit inside a weather-proof enclosure they supplied. Our team is available to customize a system for you. Are there any water quality monitoring issues you have?
Dan Emigh, Port Engineer of Un-Cruise Adventures, stated, “I chose to use the Rosemount analytical equipment from Emerson for this important function based on my past experiences when installing this panel on our first vessel back in 2000. I had fantastic support from the rep and the equipment worked precisely as expected. When it became necessary to add the same type of equipment to the second vessel in 2014 I started by contacting Emerson and again received immediate and full support from the technical staff. As a direct result of the fantastic customer and technical service I have always received from everyone, I have no reason to consider anyone else for our water treatment needs. One phone call to Emerson and questions are answered, issues are resolved, and parts are on their way to our distant ships. Thanks for all the past and present support.”
And we didn’t even have to twist Dan’s arm to say that. Remember, the next time you’re sailing with Un-Cruise Adventures, the quality of the onboard water is in good hands.