Renewable instead of fossil: biofuels contribute significantly to climate protection and, in addition, to a more sustainable economy. They are produced, for example from used cooking oil, in reactors at temperatures of up to 450 °C. Monitoring these reactors requires application-specific instrumentation solutions. For this, the precise temperature monitoring of the usually exothermic reactions is of central importance.
Decarbonisation presents refinery operators with a great challenge and at the same time opens up new opportunities for them. Biofuels are one of them. The demand for fuels from renewable sources is growing. For their production, companies can also use decommissioned or underutilised plants. By retrofitting, they are meeting the environmental requirements, which are becoming more and more stringent.
Converting a reactor and constructing a new one for biofuels
In view of the new business opportunities, a petroleum company and WIKA customer decided to convert one of its sites into a production facility for biofuels. Used cooking oil and animal fats serve as the raw materials there. The tendered project comprised the retrofitting of an existing HDI reactor (hydroisomerisation) with two catalyst beds as well as the construction of a new three-bed reactor for hydrotreating (HDT).
The processes inside the reactors require precise temperature monitoring. To ensure safe and efficient operation of the reactors, the operator needs a temperature profile. It is based on the measured values of the temperature monitoring in the middle and upper layers of the catalyst beds and on the results of a radial temperature measurement with a higher density of measuring points in the lower area of the beds. Using such a temperature profile, dangerous hot spots, channelling effects and uneven distribution of the catalysts can be detected in good time.
Multipoint thermocouples fulfil the measurement requirements mentioned above. They also withstand the process temperatures between 430 °C and 450 °C that are required for this application.
Two multipoint thermocouple models in the catalyst beds
The model TC96-R Flex-R® multipoint thermocouple enables a quick and precise generation of temperature profiles in a reactor for biofuels.
When it came to the instrumentation, the company opted for multipoints by WIKA. Temperature monitoring in the lower areas of the catalyst beds is carried out by model TC96-R Flex-R®, which features thermocouples that can be flexibly positioned. Each bed is equipped with a TC96-R Flex-R® with 14 measuring points (HDT reactor) or 12 measuring points (HDI reactor). The instrument ensures response times between four and eight seconds, generating the desired temperature profile accordingly fast.
The model TC94 thermocouple in T-bar design was chosen to measure the temperature in the middle and upper areas of the catalyst beds; in each reactor, five instruments were installed, each with three measuring points. In this multipoint, several thermocouples are arranged along a guide rail (T-bar). This provides the sensors with the necessary stability for their measuring task.
Solution package included components made of Inconel 625 and the instrument installation
On request of the customer, all wetted components of the measuring instruments were made of Inconel 625 to counteract possible corrosion. Such a risk may occur in particular in HDT reactors in the presence of free fatty acids, carbon dioxide, water and chlorine. In addition to the measuring instruments, the order also comprised the temperature transmitters required for signal processing. On top of that, the temperature specialists from WIKA-Gayesco handled the installation of the multipoints.
Note
On the WIKA website you will find further information on multipoint thermocouples TC96-R Flex-R® and TC94. There you will also find a brochure on “Multipoint temperature measurement” as well as an overview of other measurement solutions for the oil and gas industry. Would you like to learn more about WIKA’s sustainability strategy? Then download a copy of the sustainability report. Should you have any further questions, your contact will gladly help you.
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