For many years, methanol has been established as an important organic basic material, both in chemical applications and in the energy sector. In the low-pressure process commonly used today, through catalytic synthesis, hydrogen, carbon monoxide and carbon dioxide are formed into methanol (CH3OH) at pressures of up to 100 bar and temperatures of up to 300 °C. The individual plant concept is chosen depending on the geographically available raw material and the desired production capacity.
The production process takes place in four stages:
In order to reduce the energy required and achieve a consistently high throughput with constant quality, the operators are dependent on maintaining several critical process parameters - pressure, temperature, flow rate, level - in the respective plant sections.
Rather than coal, naphtha and oil, today, natural gas is mainly used as the input raw material for methanol production. Unwanted natural gas components such as sulphur are bound in the form of hydrogen sulphide (H2S) through targeted hydrogenation and then removed in the desulphurisation reactor.
In order to monitor the activity of the catalyst in the hydrogenation reactor constantly over the entire bed, specially adapted multipoint thermometers are used to monitor multiple points. Correct functioning must be permanently guaranteed, since any sulphur components that slip through would poison the downstream process steps. The correct gas flow is detected by using compact orifice plates, Venturi tubes with mounted differential pressure transmitters.
Depending on the feedstock and the selected plant design, one, two or three types of reformers are installed in series for methane steam reforming:
This combination is responsible for the optimal recovery of hydrogen and syngas. In the catalyst bed-based cylindrical pre-reformer, the first pre-reforming stage takes place under the supply of hot steam at around 500 °C and 30 bar.
In order to monitor the activity and ageing of the catalyst constantly over the entire bed, specially adapted multipoint thermometers are used to record multiple points. The ratio between gas and steam must be monitored precisely to prevent coking and damage to the catalyst. Compact orifice plates and Venturi tubes with mounted differential pressure transmitters perform this task reliably and durably.
In the primary reformer (known internationally as a steam methane reformer - SMR), reformer tubes are mounted vertically in several rows, which are continuously fired with burners from the outside. The conversion of the gas-steam mixture into hydrogen, carbon monoxide and carbon dioxide takes place in the catalyst-filled interior of the tube. The walls of the reformer tubes, which are usually specially alloyed, are permanently under particular stress due to the high temperatures. A crack during regular operation due to overtemperature is not uncommon. This can make it necessary to shut down production or could even damage the entire plant. The alternative operation of the process - as is often practised - with a reduced flame leads to a reduced throughput and the plant operator must accept permanent losses in efficiency.
Through the targeted analysis of the individual set-up and perfect positioning of tube-surface temperature sensors (XTRACTO-PAD®) matched to the tube materials, we offer the perfect solution. The exact tube surface temperature, which is independent of the flame strike, is recorded 24/7 due to the special shielded design. The SMR can now actually be controlled for longevity with the highest throughput. Furthermore, in addition to the tube surfaces, the temperatures of the flue gases produced by firing are also monitored in the chamber. Sensor solutions suitable for this purpose, with thermowells made of materials which are resistant over the long term, are developed specifically for your application.
Depending on the feedstock and the selected plant design, one, two or three types of reformers are installed in series for methane steam reforming.
This combination is responsible for the optimal recovery of hydrogen and syngas. After initially converting about one third of the gas passed through the primary reformer, the next stage “ignites” in the secondary reformer at temperatures of over 1,000 °C and pressures of over 30 bar to achieve a conversion of close to one hundred percent. The ATR has a refractory lining in the interior. The steam-gas mixture and, via a large burner, preheated process air (oxygen and nitrogen components) are fed in from above. First, partial combustion - partial oxidation - takes place. Then the mixture flows through the catalytic bed, located in the middle part of the reformer, and the remaining methane components are finally converted.
In order to monitor this demanding process properly and continuously, the correct temperature is recorded in many catalyst beds by means of specially designed WIKA multipoint temperature sensors. Due to their robust design and the protection of the sensor elements against hydrogen poisoning, these sensors offer redundant measurement which is stable over the long term.
The freshly reformed syngas is combined with recycled syngas and compressed to around 80 bar by means of a multistage compressor driven by steam turbines. Before and in the course of the compression, the medium is intercooled and the resulting condensate is separated in separators. Their level must be monitored continuously to prevent any potential overflow. The compressors and downstream plant areas are thus protected from excessive moisture content.
Modular bypass level measuring instruments are recommended for this task, as they transmit the level precisely and, via an optional switching function, trigger a warning in good time. At particularly critical points, versions with a double chamber enable redundant measurement. In addition to the bypass indicator, other measuring systems can be integrated, for example, reed chain, magnetostrictive sensors, radar and vibrating fork. For smooth operation of the compressors, the temperature in their heavily stressed bearings must be monitored. Highly vibration-resistant temperature sensors ensure the necessary accuracy for this.
In the methanol reactor, the synthesis of hydrogen, carbon monoxide and carbon dioxide to methanol (CH3OH), and the by-product water, takes place in a low-pressure process at pressures of 50 ... 100 bar and temperatures of 200 ... 300 °C. Depending on the plant concept, several gas-cooled and water-cooled reactors, connected in series with catalyst-filled tubes, are used.
To ensure that the required pressure for the desired synthesis is constantly available, measurements (precise, even under high temperatures) are taken at the reactor inlet and outlet using a temperature-compensated process transmitter/diaphragm seal system. During the multistage reaction, a lot of heat is generated, which is removed using intercooling stages. The critical temperature distribution along the catalyst beds is monitored by several fast-response multipoint thermometers with rapid heat transfer.
After methanol synthesis, the media flow is cooled down and the liquid methanol and water components are separated from the unreacted syngas components in the methanol separator. The gases are returned to the synthesis circuit via the pressure swing adsorption unit. The liquids are passed on to the expansion tank as raw methanol.
Diverse-redundant sensors are often used for level monitoring in the separator. Differential pressure transmitters with fully welded seal-less diaphragm seals output the hydrostatic level column. Operationally proven level indicators, with reed chain or magnetostrictive transmitter and optional two-chamber system for mounting a radar sensor, thus ensure a constant measurement with a stable signal.
At the end, the resulting crude methanol is processed in two steps in the methanol fractionating columns for storage and resale. In the low-boiling column (topping column), highly volatile by-products such as dissolved gases are first separated using distillation. Then the final separation of the pure methanol from water and alcohols takes place in the high-boiling columns.
The correct separation, distillation and onward transfer of the media is monitored by means of diverse-redundant level sensors. Differential pressure transmitters with fully welded seal-less diaphragm seals output the hydrostatic level column. Operationally proven level indicators, with reed chain or magnetostrictive transmitter and optional two-chamber system for mounting a radar sensor, thus ensure a constant measurement with a stable signal.
Methanol is stored temporarily in large tanks until its further use. Free-hanging multipoint thermometers are often used to monitor the temperature in the tanks, which are typically operated without pressure. Thanks to their compact design and smart transport and installation concept, the sensors, some of which are over 20 metres long, can be conveniently handled and installed in the plant without the use of an additional crane.
Precise calibration instruments are the starting point for resolving your test requirements. However, they only form one part of a high-performance calibration system. From our extensive product range, we can design a complete and individual solution for you which contains all the relevant components: with adaptability for test items, pressure and vacuum supply, components for pressure control and fine adjustment, through to voltage supply and multimeters for the calibration of electrical test items. Our particular strength lies in the project planning, development and the building of complete, individual, application-specific systems – from simple manual work stations through to fully automated test systems in production lines.
Are you looking for suitable calibration equipment for your applications? Get an overview of our wide range of calibrators. Use our calibration service for pressure, temperature, force, flow and electrical measurands. We calibrate your references and test equipment independently of manufacturers in our accredited calibration laboratories, or directly on your premises.
WIKA will support you with additional services from our trained experts. Service technicians will make sure that your measuring instruments, in case of breakdowns and repairs, are fully functional again in a short space of time. From pressure controllers and diaphragm seal systems to calibration baths - all from one source. We install your measuring units and provide support for the commissioning of the instrumentation. Through our local experts, we can be reached worldwide, are quickly available and tuned to individual circumstances. Try it for yourself.