Yokogawa's role
Supporting efficient operations and stable quality in many types of complex production facilities
Petrochemical plants produce a wide range of products from naphtha, which is extracted from crude oil. The processes of removing by-products generated through chemical reactions and refining products are long and complex, requiring high-quality and highly reliable measurement instruments and control systems.
For these processes, Yokogawa provides temperature sensors, flowmeters, level meters, pressure transmitters, and other measurement devices that can be mounted on storage tanks, distillation columns, pipes, pumps, and other kinds of equipment, as well as systems that control these processes based on measurement data. With the extensive know-how and advanced technical capabilities that it has cultivated at all kinds of manufacturing facilities, Yokogawa can keep plants operating safely and efficiently, and provide maintenance and other forms of support over their entire lifecycle.
How petrochemical products are made
Crude oil from wellheads located onshore or at offshore drilling rigs (platforms) is transported by pipelines and tankers to oil refineries, where it is distilled to produce fuels such as gasoline and kerosene, as well as materials like naphtha. In a thermal cracker, the naphtha is broken down and purified to produce basic petrochemical products such as ethylene and propylene that are used as feedstocks in the production of petrochemical derivatives such as plastics, synthetic fiber raw materials, and paint raw materials. These products are also called intermediates. They are then processed into the finished products that we see all around us.
Measurement and control in petrochemical plants
Measurement devices such as temperature sensors, flowmeters, level meters, and pressure transmitters are mounted at key locations in ethylene, propylene, and other petrochemical derivative plants to continuously measure the condition of raw materials. Measurement and operation data are collected by the control system, and operations throughout a plant facility are monitored, controlled, and managed from a central control room. Plant safety, productivity, and equipment utilization are optimized 24 hours a day, 365 days a year.
Flowmeter
Mounted on a pipe, this measures the volume and mass (flow rate) of fluid flowing through it per unit of time.
Oxygen analyzer
Mounted on a furnace, this measures the oxygen concentration in the combustion process. The combustion conditions can thus be monitored and controlled to reduce CO2 emissions, reduce the emission of air pollutants, and save energy.
Gas chromatograph
This analyzes a gas or volatile liquid made up of multiple components.
Using chromatography, the individual components are analyzed, and their concentration is measured. This is mainly done to control the quality of raw materials and products.
Level meter (pressure type)
Mounted on equipment such as tanks and reactors, this measures the liquid level and calculates the remaining volume as a percentage of total capacity.
Pressure transmitter
Mounted on pipes and other types of equipment, this measures the pressure levels of gases and liquids.
Central control room
Based on the measurement and operation data acquired by the control system, the entire plant is centrally monitored and controlled from this location.
If a serious anomaly occurs, there is also a specialized system that can prevent accidents by safely shutting down the plant.
Measurement and control of key facility (distillation column)
A distillation column extracts necessary components based on differences in their boiling points. At oil refineries, distillation columns refine crude oil to produce naphtha, gasoline, and other products, and at ethylene plants, they thermally decompose naphtha then distill it to produce ethylene and other distilled products. Temperature sensors, flowmeters, level meters, pressure transmitters, and other devices mounted on the distillation column and its pipework send a continuous stream of measurement data to the plant control system. The control system manages the operation of equipment so that operating conditions remain close to preset target values. For example, if measurement data show a deviation from the target value due to a sudden change in the outside temperature, thereby affecting the boiling point, the control system makes changes to the valve settings and alters the flow rate, thereby returning the distillation column to a normal state.
Flow control of raw materials at the distillation column inlet
Naphtha is thermally decomposed, and liquid raw materials containing various components enter the distillation column. Fluctuations in the flow of these components are an external factor (disturbance) that impacts the control of the distillation column. To maintain conditions in the column in an optimal state, flowmeters measure the flow rate in the pipes, and valves are opened or closed.
Pressure control of evaporated gas at the top of the distillation column
Ethylene produced in the distillation column is discharged as a gas from the top of the column. To prevent fluctuations in the gas pressure from affecting the ethylene components, the gas pressure is measured with a pressure transmitter and the pressure and liquid level are adjusted in the reflux drum (a device for refluxing liquids). Some of the ethylene that has cooled and reverted to a liquid state is sent back to the distillation column for further purification.
Component control of liquids extracted from the distillation column
To efficiently extract ethylene with the targeted purity level, a certain amount of ethylene that has returned to a liquid state in the reflux drum is vaporized within a gas chromatograph to separate and analyze its constituent components. Based on the results, the flow rate of the liquid that is being pumped back to the distillation column is controlled. The liquid mixture extracted from the bottom of the distillation column is also sent to a gas chromatograph for component analysis, and based on the results, the operation of the heater (reboiler) is controlled to maintain product quality and conserve energy.
Related Industries
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Oil & Gas
Yokogawa has a wealth of experience in every part of the oil and gas business, from offshore and onshore facilities to pipelines, terminals, and deepwater operations. We provide solutions that enhance safety, ensure accurate and reliable operation, and increase plant efficiency.
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Chemical
Chemical plants rely on continuous and batch production processes, each posing different requirements for a control system. A continuous process calls for a robust and stable control system that will not fail and cause the shutdown of a production line, whereas the emphasis with a batch process is on having a control system that allows great flexibility in making adjustments to formulas, procedures, and the like. Both kinds of systems need to be managed in available quality history of product, and to be able to execute non-routine operations. With its extensive product portfolio, experienced systems engineers, and global sales and service network, Yokogawa has a solution for every plant process.
Related Products & Solutions
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Control
Yokogawa offers automation and control strategies, architectures, and solutions for every application size and complexity.
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Lifecycle Services
Maintenance capabilities backed by extensive experience gained from working closely with our customers allow us to optimize operations over the entire plant lifecycle.
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Measurement
With its highly reliable measurement technology, Yokogawa is able to offer an extensive lineup of product solutions that deliver new value to our customers by bringing together operational technology (OT) and information technology (IT).