Key points
The production of chemicals that are used to create products such as polymers, plastics and fertilisers requires flow control solutions. The “chemicals” industry is a broad term. It stretches from olefins and aromatics through to speciality chemical producers such as coatings, adhesives, ceramics and lubricants; the production of polymers and thermoplastics and polyamides; inorganics such as chlorine and acids; agrochemicals and fertilisers; industrial gases such as nitrogen, oxygen and hydrogen.
The manufacture of associated products like paints, colourants and chemicals sold directly to consumers (in the form of detergents, soaps and cosmetics) also fall under the wider chemical market.
At all stages of production, flow control products such as actuators must provide exacting levels of durability and safety. Above all, they must provide reliability and precision when controlling the flow of gases and liquids.
How do actuators help with precision valve control within the chemical industry?
Actuators working within the production of chemicals can make process adjustments easily and increase batch repeatability. Control valves are used in the chemical industry to control conditions including flow, media, pressure, temperature and liquid level. They require precise control input to achieve a high-quality end-product.
Control valves can operate to open and closed positions, move to predefined set points or operate in a modulating state. Modulation of the valve position regulates the flow rate and is used for accurate control of the secondary parameters such as temperature, level or concentration.
Sensors throughout the plant monitor the process mediums and send feedback to control systems. Signal commands are then sent to an actuator, instructing it to move the valve, which in turn changes the mixture.
Patrick Ho, Product Manager – HVAC and Control Valve Solutions at Rotork, said: “Production of chemicals requires specialist equipment, especially specialist flow control. Both the precision and repeatability required means that process control actuators are the ideal choice to deliver both quality products and safe operation.”
Process control actuators
Specialist process control actuators are required in part because of the high precision valve control achievable, as well as the constant movement required to maintain the process. Process control actuators should provide continuous, accurate and repeatable modulating control.
For industrial gases, agrichemicals, polymers, specialty chemicals and beyond, process control actuators provide the precision required to enact the necessary processes to ensure success. Repeatability is important within chemical production because control valves are often required to move repeatedly between two or more setpoints.
The ability to move the valve to the same position time after time means the control system does not need to make adjustments for position variance. Appropriate process control actuators, like Rotork’s CVA and CMA are designed to be highly responsive with rapid, repeatable operation and resolutions of 0.1%; they move quickly and accurately with very little variation. Consistency is key.
Temperature control within chemical production
Temperature control is an essential part of successful chemical production. Even tiny variations in temperature can cause failure, wastage or reduced product quality. Sensors monitor conditions and send feedback to control systems that then send signals to actuators to change mixture or conditions.
For example, Rotork CVA all-electric control valve actuation technology improved the efficiency of the production process for an Australian polymer manufacturing company.
Automation of a previously manually operated temperature control of water supplied to the condenser (as part of the water/glycol separation process) was required. Previous temperature variation of 1-2 °C resulted in an unacceptable level of wasted product.
Rotork installed an electric control package, with a V-port ball valve operated by a CVA actuator. This led to reduced product waste as the CVA provided the precise and modulating valve operation required.
Any combustion process used within the chemical industry requires the exact ratio of fuel and air within a furnace to produce the right amount of heat. This allows both for energy-efficient production and considers the high cost of running industrial combustion.
If excess and unnecessary fuel is used, money is wasted. Effective combustion control reduces the level of emissions and improves the efficiency of the process, by modifying combustion firing conditions.
Effective combustion that produces the appropriate level of heat without leaving any unburned and wasted fuel is essential in reducing emissions and saving money. The choice of a process control actuator helps achieve this. Reduction of emissions through actuator choice is also relevant. Electric actuators, rather than pneumatic options, are often favoured in chemical production because of sustainability concerns.
Electric flow control does not release emissions in the same way as pneumatic actuators but still meets the high standards of control required. This issue of sustainability of production methods will only increase in importance over the coming years and electric actuation is a sensible choice in reducing environmental impact.
Safety concerns are answered by reliable flow control products
Intelligent electric actuators can also provide reliable and efficient precision valve control within chemical production. This was seen in a recent project at a chemical processing plant in Cadiz, Spain that produces linear alkyl benzene, paraffins, sulphonic acid and heavy alkylate.
IQ3 actuators were installed on gate valves and control the flow of unprocessed fluids and provided Emergency Shutdown (ESD) capability. In an emergency, they can release the fluids into suction and discharge pumps for isolation.
This example also highlights a further consideration that manufacturers and operators must consider; the robust and safe nature of actuators chosen. Appropriate actuators with suitable ingress and atmosphere protection to cope in demanding environments must be chosen; hazardous area certified equipment is usually required within chemical production because of the likelihood of harsh or corrosive environments. Explosion-proof flow control can be necessary. The enclosure of IQ3 actuators is rated IP68 (20 m for 10 days) and NEMA 4/4X/6.
Conclusion
The chemical industry covers a wide group of different producers and operators, stretching from consumer products and the production of inorganics to the creation of fertilisers and specialist chemicals. Irrespective of the final product, the chemical industry relies on efficient and effective flow control. Process control actuators are often the product of choice. Patrick Ho said: “Process control actuators provide continuous, accurate and repeatable modulating control, which is essential within the chemical industry. They are highly responsive and are able to provide high degrees of accuracy.”
