|A Quarterly Newsletter of Parr Instrument Company|
December 2018 | Vol. 5 No. 3
New Product Announcement
Temperature Sensors and Control
Gas to Liquid Applications
Use of Process Calibrators for Troubleshooting Loop Controllers
Parr Team Member Focus
New Product Announcement
4848T Touchscreen Reactor Controller
We are excited to announce our new 4848T Touchscreen Reactor Controller!
The Parr Model 4848T Controller brings a new touchscreen design to our controller line. This full featured controller has the same functionality as a fully populated 4848 Reactor Controller with a touchscreen interface.
- PID Temperature Control with Ramp and Soak Capability
- Motor Control, with Pressure and Auxiliary Temperature Displays
- 7″ Touchscreen Interface
- Data logging to Local USB Drive
Download the 4848T Touchscreen Controller Sales Literature.
Look for the system to launch on our website on January 1, 2019 along with special dealer content on our Dealer Extranet at that time.
Please contact us with any further questions regarding the new 4848T Touchscreen Reactor Controller.
Temperature Sensors and Control – Location, Location, Location
All of us that sell and/or service Parr reactors and pressure vessels have had conversations with customers describing the process of temperature control. While the concept of using a temperature sensor and controller to heat a reactor to a desired set point is relatively simple, it may be useful to remind ourselves of the three main components of such a system.
- Temperature sensor (thermocouple or RTD)
- Temperature controller (typically housed inside a 4848, 4838, or 4871 controller)
In simple terms, the controller takes an input signal from the temperature sensor, compares that measured value to the desired control temperature, and provides an output signal to the heater.
While conceptually straightforward, both new/inexperienced users and even VERY experienced users can overlook some of the simplest aspects of temperature control, sometimes with dangerous consequences. This brief article will discuss one of them: the location of the thermocouple.
A thermocouple consists of two wires made of dissimilar metals. They are in contact with one another at a single point. In a typical thermocouple provided by Parr, that contact is very near the end of the SS sheath, opposite the plug. When the thermocouple sheath is swaged into the head of the reactor or inserted into the thermowell and the plug is connected to the controller via a thermocouple wire (which consists of the same two dissimilar wires as are found in the thermocouple sheath), that thermocouple outputs a millivolt signal to the temperature controller. That signal is correlated to the sensed temperature.
Omega, a manufacturer of temperature sensors, has created a short video illustrating this concept: https://youtu.be/qF2wCb-OWM4 . Note that the “cold junction” shown in the video is located INSIDE the temperature controller.
Two potential problems can occur in this system.
- The extension wire could be damaged. We have received occasional reports of thermocouple extension wires unintentionally coming in contact with the reactor heater during operation such that the extension wire insulation melted and the two metal wires fused. This leads to the formation of a new thermocouple junction at the point of fusion. This new thermocouple junction then outputs a signal representing a lower temperature than that of the thermocouple inside the reactor.
- The thermocouple could be left out of the thermowell. We have received occasional reports (and in practice, we suspect this happens more frequently than is reported), that a user has forgotten to install the thermocouple in the thermowell prior to an experiment. If the thermocouple is left on the bench, for example, the controller receives an input signal representing ambient temperature.
Both these situations can lead to a similar outcome, that is, a controller receiving input from the temperature sensor that does not represent the intended input. In effect, the controller “thinks” the reactor is at a lower-than-actual temperature and increases the output signal to the heater. Because the temperature sensed by the thermocouple and transmitted to the controller does not change, the controller continues to increase power to the heater (attempting to minimize the difference between the measured temperature and the set point) until the heater reaches full power. It is as if the controller has been removed from the control system, and the heater acts as if it had been plugged directly into a wall receptacle. This can be especially dangerous if the user leaves the apparatus unattended for a significant time. The photo shows the results of an experiment started late in the afternoon and left unattended overnight, with the thermocouple left on the bench.
Gas to Liquid Applications for Parr Reactors
The Gas to Liquids or GTL (and the recently more popular Biomass to Liquids) process involves at least three major high pressure catalytic steps which are performed commercially in huge continuous flow reactors. Each of these steps require solid catalysts that have been tested and proven at laboratory scale. Laboratory catalyst testing may include formulation screening, long term activity, catalyst poisoning, catalytic reaction rate (chemical kinetic), catalyst regeneration, and material compatibility tests. Laboratory GTL catalyst testing may be done in batch reactors, but also in a continuous flow reactors such as a tubular packed beds or a fluidized bed reactors, which may better simulate the commercial process.
The three main steps for the Gas to Liquids process are:
- Synthesis gas (or syngas) generation (also known as reforming)– a high temperature (600-1000+ °C), moderate pressure (20-50 bar) process where steam, oxygen, or CO2 are used with a solid catalyst to reform a fuel or hydrocarbon source (such as natural gas or wood chips) into a gas containing carbon monoxide (CO) and hydrogen (H2), the process requiring a large amount of energy (heat). Often combustion is used to provide the high temperature heat needed. Higher temperatures provide higher quality synthesis gas as the product gas equilibrium shifts toward CO and away from CO2. Reforming reactors are also used to make hydrogen from steam. Reforming reactors are typically made from a high temperature high nickel alloy.
- Fischer-Tropsch synthesis– CO and H2 in the synthesis gas are formed together into longer hydrocarbon chains, in a catalytic process forming hydrocarbon oils and waxes in a moderate temperature (200-300 °C), moderate pressure (10-40 bar) process, releasing a large amount of energy (heat). Commercially, this heat is often removed by flowing high purity water through integrated cooling channels or pipes where a portion of the water boils, thus removing the heat while controlling the wall temperature. Large amounts of (acidic) water and some methane and other light gases are produced as side products. Most of the organic (hydrocarbon) product is generally a solid at ambient temperature and will clog product lines if not kept heated.
- Distillation/Hydrocracking – the waxy or heavy (high molecular weight) portion of the Fischer-Tropsch reaction product is heated, separated off, and treated with high pressure (35-200 bar) hydrogen at moderate temperatures (260-425+ °C) to crack the molecules to lighter (lower molecular weight) products. In this way more of the product can be used for fuels such as diesel or petrol. Note that in most applications, neat GTL synthetic diesel product cannot be used to replace conventional diesel but must be blended with conventional diesel to increase the aromatic content (to prevent problems with seals).
Making a complete Gas to Liquids pilot plant is challenging, as it typically requires additional equipment and design elements such as a steam boiler, boiler feed water treatment equipment, recycle compressors (including for catalyst regeneration), hydrogen separation membranes, distillation columns, pumps, heat exchangers, three-phase high pressure separators, heat tracing, and storage tanks. A full pilot plant typically requires significant engineering on the part of the customer or the customer’s Engineering Procurement Construction (EPC) firm.
If you have an inquiry related to any of the steps in a Gas to Liquids application or related catalyst testing, please submit an inquiry to email@example.com (or firstname.lastname@example.org within the US) and we would be happy to help design a system to meet the needs of your customer. Although Parr cannot meet the design specifications of every request, we have customized systems to meet a surprisingly wide variety of requests and will continue to do so.
Use of Process Calibrators for Troubleshooting Loop Controllers
A Process Calibrator is a device that sources process signals such as 0-20 mA, 0-5 Vdc and thermocouple signals for calibration purposes or troubleshooting. This article describes how calibrators can be used to troubleshoot Parr loop controllers and meters.
Thermocouples – A calibrator can be used to check suspected erroneous temperature measurements or faulty thermocouple circuits. If a reading’s value is suspect, a calibrator can be used to inject a thermocouple type specific signal equal to the suspect temperature(s) to compare with the measured value. A calibrator can also be used to isolate where a faulty connection is located. For example if a meter was indicating an open circuit, the calibrator can be connected in between parts of the circuit, such as the thermocouple / external cable junction, or the internal cable / loop controller junction. In the example given if the meter matches the calibrator when connected to the rear panel connector on the controller, but not at the end of the extension cable, it can be determined that the open is located in the extension cable. Calibrators can also be used to validate an alarm trip point.
Pressure Transducers – Parr’s typical pressure transducers output a 0-5 Vdc signal proportional to the pressure, based on the range indicated on the transducer labeling. A calibrator can be used to isolate a faulty part of the transducer circuit, in a method similar to the thermocouple procedure. Or it can be used to validate the displayed pressure measurement, which if erroneous, would indicate a faulty transducer or a parameter setting issue in the loop controller.
Tachometers – Parr’s typical tachometers are slightly trickier to simulate. The tach sensor provides a pulse signal to a Frequency to Voltage converter located on the A1695E board inside of the Parr controller. The calibrator can be used to simulate the 0-5 volt signal (ranged 0-2200 rpm) that is sent from the frequency to voltage converter to the loop controller. Some high end calibrators can source frequency signals to simulate Parr’s standard IR sensor (1000 Hz = 1750 RPM).
Multifunction calibrators are readily available that can source signals for all of the analog IO sensors that Parr provides, such as Current and Voltage, RTD, Thermocouple, Frequency, etc. High end models can even come equipped with ramp and step programming for more advanced troubleshooting. Simple test harnesses can be created to simplify connections to a controller. For more details, please contact Parr’s Technical Support staff.
2019 Dealer Training
Parr Instrument Company is committed to providing expert sales and technical support for our products. We believe that a big part of this is providing training to our representatives from around the world.
Periodically, Parr holds training sessions at our main office/manufacturing facility in Moline, Illinois. We do not charge for this training. Your only expenses would be travel and lodging.
- April 15 – 19, 2019
- September 16 – 20, 2019
Please contact us at email@example.com in advance if you would like to attend either of these sessions. We can help with letters of invitation and hotel reservations. Please let us know if there is any special training you would like and we will be happy to try to accommodate you.
Parr Team Member Focus
Steve Perry, Senior Product Manager
We are happy to introduce Steve Perry who has recently joined Parr as our Senior Product Manager for the stirred reactor, pressure vessel, and reactor system product lines. Steve will provide technical leadership to support customers and dealers in liaison with sales, engineering, and production staff. He will also work to leverage enhancements of existing products and help identify/develop new product offerings.
When asked what he likes so far about his new position at Parr, Steve said “Working with competent and kind people on a wide variety of projects.”
Steve received his undergraduate degree in Chemical Engineering from Brigham Young University (Provo, UT), a Masters in Metallurgical and Materials Engineering from Michigan Technological University (Houghton, MI), and a PhD in Chemical Engineering from Brigham Young University.
Steve has over 15 years experience in the design and testing of laboratory-scale and pilot-scale microchannel continuous methane steam reformer reactors and Fischer-Tropsch reactors (Pacific Northwest National Lab, Battelle, and Velocys). He also has experience working with organic synthesis batch reactors (Resodyn), combustion (PNNL, BYU), and solids handling (MTU, BYU, Velocys). During his time at Battelle and Velocys, Steve was a contributor on 29 patents.
Having grown up in Bothell, WA, Steve has more recently called Columbus, OH home and now resides in Bettendorf, IA. Steve and his wife Teresa have five children, only two of which are still at home. They enjoy reading, biking, swimming, singing, playing board games, visiting family, and home remodeling.
We are excited to add someone with Steve’s process and engineering experience, as well as his personal attributes, to our staff. Please join us in welcoming Steve to Parr!
We are currently compiling our 2019 Trade Show Schedule. Please send us a list of any shows where you will be representing Parr in 2019 and we will be happy to further your exposure by adding them on our Trade Shows page.
Email your trade show schedule to firstname.lastname@example.org.