What is Liquid Carryover? Understanding the Impact and Prevention

In various industrial processes, especially in fields such as chemical manufacturing, oil and gas, and power generation, the proper separation of gas and liquids is crucial. One significant challenge that engineers and operators often encounter is the phenomenon known as “liquid carryover.” This occurrence can have detrimental effects on equipment, product quality, and overall process efficiency. In this blog post, we’ll delve into the concept of liquid carryover, explore its implications, and discuss its monitoring and suggest some preventive measures to mitigate its effects.

Liquid carryover, in simple terms, refers to the unintentional entrainment of liquid in a gas or vapor stream. This can occur in various equipment and processes where both liquids and gases are present, such as natural gas processing, gas transmission and distribution pipe networks, distillation columns, gas and steam turbines, compressor systems, and industrial scrubbers, filters and phase separation. The liquid carried over in the gas stream can vary in size, from fine mists to larger droplets and can convert to a liquid stream on the bottom of a pipeline known as a stratified flow.

Implications of Liquid Carryover

The consequences of liquid carryover can be significant and far-reaching:

  1. Safety Concerns: The presence of liquid in a gas stream can lead to erosion, corrosion, and mechanical damage to downstream equipment such as regulators, valves, compressors and gas turbines. Liquid carryover can compromise the safe operation of equipment and processes. For example, liquid carryover in gas fed to a compressor causes excessive wear to dry gas seals that, when not maintained, has led to the loss of containment and explosion. When liquids are supplied to gas turbine power stations, uneven burn, fuel nozzles wear, and damage to turbine blades can potentially cause catastrophic mechanical failures.
  2. Financial Impact: When wet gas is unexpectedly present in natural gas systems, it results in significant errors in fiscal measurements of flow and calorific value. Gas suppliers that are unwittingly allowing natural gas liquids into the gas export line do not get paid for their calorific value as they are not included in the gas analysis and BTU calculation. Gas transmission companies incur 4x the compressor servicing costs compared to dry gas compressors and extra costs and downtime to pig the line and dispose of the waste products.   
  3. Reduced Efficiency: Liquid carryover and its associated solids can interfere with the efficient operation of gas processing, affecting heat exchange, mass transfer, and fluid dynamics. This can lead to decreased process efficiency, extra downtime, decreased asset life and suboptimal product quality.
  4. Environmental Impact: With methane having up to 28x the CO2 equivalent, the venting of natural gas should be minimised. But, the extra maintenance of compressors, valves and regulators and vessels that liquid carryover causes in natural gas systems means that greenhouse gas emissions are higher than they could be if liquid carryover was better controlled.

Preventing Liquid Carryover

To prevent or minimize liquid carryover, engineers and operators implement various strategies:

  1. Effective Instrumentation: Due to the difficulty of monitoring, liquid carryover is an area that has been overlooked for too long. Installing and maintaining appropriate instruments, such as process cameras, can provide real-time data to monitor and control liquid levels effectively. Once the type, severity and frequency of liquid carryover events is understood, an appropriate and effective solution can be implemented. Whatever the solution, a continuous check to ensure correct phase separation continues over time is essential.   
  • Regular Maintenance: With effective monitoring, inspection, cleaning, and maintenance of equipment can identify potential issues before they escalate. Changing filter cartridges when carryover begins to escalate rather than on a set service interval will optimise the process.
  • Process Optimization: with better data about liquid carryover, process conditions can be optimised, including pressure, flow and temperature to help reduce the chances of liquid carryover.
  • Proper Equipment Design: without good data on liquid carryover, ensuring that equipment is designed with appropriate separation and drainage mechanisms can be challenging. While there is ample technology to solve any phase separation problem, selecting and sizing the best technology to can be challenging without knowledge of the liquid carryover characteristics. The data from process cameras can justify the cost of improving existing assets. This includes better demisters, baffles, cyclones and separation media in filters.

Liquid carryover is a phenomenon that can have serious implications for industrial processes, equipment, and overall efficiency. Understanding the causes and consequences of liquid carryover empowers engineers and operators to take proactive measures to prevent its occurrence. By implementing proper equipment design, maintenance practices, and process optimization, industries can minimize the risks and additional costs associated with liquid carryover and ensure smooth and efficient operations.

In the ongoing pursuit of innovative solutions, LineVu offers a cutting-edge approach to addressing liquid carryover. Specifically designed for Midstream and Downstream applications, LineVu introduces liquid carryover detection that can revolutionize the natural gas industry. By providing a live video feed of pipeline conditions, LineVu allows gas treatment plant operators and gas network managers to make informed, evidence-based decisions swiftly.

This technology not only facilitates quicker reactions to prevent issues like foaming and fouling in processes such as desulphurization and dehumidification but also offers a step-change to improve the efficiency of phase separators and filtration systems. With LineVu, decision-making becomes significantly easier, as operators and managers gain real-time insights into pipeline conditions, enabling them to optimize production, enhance safety, and ultimately achieve higher levels of operational excellence.

By combining technological advancements like LineVu, that provides a deep understanding of liquid carryover,  with experienced process managers, gas processors and transmission system operators  can see the future of plant management and usher in a new era of efficiency, productivity, and reliability in their operations. The ongoing collaboration between engineering principles and innovative solutions ensures that the challenges posed by liquid carryover can be effectively managed, leading to safer, more efficient, and environmentally conscious industrial processes.

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About the author

Paul Stockwell, the managing director of Process Vision, is a renowned authority in moisture measurement with 35 years of experience in the oil and gas industry. He founded International Moisture Analysers (IMA) and played a key role in advancing moisture measurement techniques. Notably, he introduced tunable diode laser absorption spectroscopy for natural gas measurements, revolutionizing the field and establishing it as the industry standard method. Throughout his 20-year tenure as managing director, Paul has gained valuable insights into process optimization, cost reduction, and safety enhancement. His vision for Process Vision encompasses improving process throughput, reducing maintenance costs and CO2 emissions, and nurturing young engineering talent, aiming to make a significant difference in the oil and gas industry.

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