Frequently Asked Questions

Membrane separation is a purely physical process with no phase change, no chemical additives, and no heat required, making it simpler and more energy-efficient than traditional methods like distillation, absorption, or cryogenic separation. Traditional methods often involve large equipment footprints, high energy consumption, and complex operations with moving parts. Membrane systems are compact, modular, easy to install, and can operate unattended, making them ideal for remote or offshore locations.

Membrane separation is used across a wide range of industries including petrochemical plants for hydrocarbon and monomer recovery, natural gas processing for CO₂ and H₂S removal, refineries for hydrogen purification, and water treatment for desalination and wastewater reuse. Companies like MTR (Membrane Technology and Research, Inc.) have deployed over 450 membrane gas separation systems worldwide for applications including polyethylene production vent recovery, fuel gas conditioning, nitrogen removal, and solvent dehydration.

A hydrocarbon recovery system captures valuable hydrocarbons, such as ethylene, propylene, and other monomers, from industrial vent and purge gas streams that would otherwise be flared or lost to the atmosphere. These systems typically use membrane technology (such as MTR’s VaporSep®) to separate hydrocarbons from light gases like nitrogen and hydrogen based on differences in permeation rates through the membrane. The recovered hydrocarbons are recycled back into the production process, reducing raw material costs and improving plant profitability.

The main types of hydrocarbon recovery systems used in the oil and gas industry include membrane-based separation systems, cryogenic recovery units, absorption-based systems (using lean oil or refrigerated solvents), and pressure swing adsorption (PSA). Membrane systems like MTR’s VaporSep® are increasingly preferred for petrochemical applications because they are compact, have no moving parts, require minimal maintenance, and offer fast payback, typically less than one year.

Hydrocarbon recovery systems solve the problem of valuable feedstock being wasted through flaring or venting at petrochemical plants, refineries, and gas processing facilities. In polyethylene production alone, feedstock losses from distillation column overheads, reactor purges, and resin degassing vents can range from $1 million to $3 million per year per plant. These systems recover that lost value while also addressing environmental compliance requirements by reducing volatile organic compound (VOC) emissions and flare loads.

Hydrocarbon recovery systems directly reduce flaring by capturing hydrocarbons from vent streams and recycling them back into the process instead of burning them at the flare. This significantly lowers CO₂, methane, and other greenhouse gas emissions associated with routine flaring. For example, MTR’s membrane-based VaporSep® systems recover more than 90% of vent hydrocarbons, which drastically cuts the volume of gas sent to the flare and helps operators meet increasingly strict environmental regulations.

The main components of a membrane-based hydrocarbon recovery system include a compressor to pressurize the feed gas, a condenser and gas/liquid separator to remove condensable hydrocarbons, membrane modules that selectively separate hydrocarbons from light gases, and associated piping, instrumentation, and controls. MTR’s complete VaporSep® units are skid-mounted for easy installation, handling vent streams from 300 to 30,000 lb/h with hydrocarbon concentrations of 10 to 80 vol%.

A propylene recovery unit (PRU) is a system used in polypropylene production plants to recover valuable propylene that is otherwise lost in vent streams.

It works by first compressing and cooling the vent gas to condense part of the propylene. The remaining gas is then passed through a membrane system, which separates it into two streams:

A propylene-rich stream, which is recycled back into the process

A nitrogen-rich stream, which is purified and reused

This process enables efficient recovery and reuse of both propylene and nitrogen within the plant.

A propylene recovery unit improves efficiency by minimizing the loss of valuable raw materials and reducing waste.

By recovering up to 99% of propylene, the system significantly lowers feedstock costs and increases overall plant profitability. It also reduces flaring and emissions while allowing nitrogen to be reused in the process. Additionally, membrane systems can achieve higher recovery rates than traditional condensation alone, improving overall process performance.

A propylene recovery unit typically combines multiple technologies, including:

Compression systems – to increase pressure for effective separation

Condensation units – to recover bulk propylene as liquid

Membrane separation technology (e.g., VaporSep®) – to separate remaining propylene from nitrogen

Heat exchangers and control systems – for temperature control and process optimization

The membrane system is the core technology, enabling selective separation of propylene from lighter gases without the need for chemicals or complex operations.

To optimize efficiency, operators should focus on:

Maintaining proper pressure and temperature conditions for optimal separation

Ensuring membrane performance and cleanliness through regular monitoring

Optimizing recycle streams to maximize propylene recovery

Integrating membrane systems with existing compression and condensation stages

Monitoring feed composition and adjusting operating parameters accordingly

Combining condensation with membrane separation is especially effective, as it enables higher recovery rates even at moderate conditions.

Selecting the right technology depends on several factors:

Feed composition and flow rate

Required recovery efficiency (e.g., 90% vs. 99%+)

Operating conditions (pressure, temperature)

Space and installation constraints

Cost and payback period

Membrane-based systems are often preferred because they are compact, energy-efficient, and capable of achieving high recovery with fast payback. They also offer easier installation and lower maintenance compared to more complex alternatives.

Ethylene Oxide (EO) and Vinyl Acetate Monomer (VAM) are important petrochemical products made using ethylene as a key raw material.

EO is produced by reacting ethylene with oxygen, while VAM is produced by reacting ethylene with oxygen and acetic acid. Both processes operate in similar reactor loop systems and share a common challenge — loss of valuable ethylene in purge gases.

In both EO and VAM production:

Ethylene reacts with oxygen (and acetic acid in VAM) in a catalytic reactor

Only part of the ethylene converts in one pass, so unreacted gases are recycled

Inert gases like argon build up in the loop and must be purged

This purge stream contains valuable ethylene, which is often recovered using membrane systems and recycled back into the process

This loop-based process improves efficiency but requires recovery systems to minimize losses.

Several factors influence efficiency, including:

– Catalyst performance and selectivity (affects conversion rates)

– Reaction temperature and pressure control

– Feedstock purity (ethylene and oxygen quality)

– Recycling and purge gas management

– Ethylene recovery systems (like membranes)

Poor control or losses in purge streams can significantly increase operating costs due to lost ethylene.

Ethylene Oxide (EO):

Production of ethylene glycol (used in polyester and antifreeze)

Surfactants, solvents, and sterilization agents

Vinyl Acetate Monomer (VAM):

Adhesives and coatings

Paints and sealants

Packaging and textile materials

Both are essential building blocks in the chemical and manufacturing industries.

Temperature control is critical because the reactions are highly exothermic (heat-generating).

It is managed by:

Using multitubular reactors with cooling systems

Circulating coolants or generating steam to remove excess heat

Maintaining controlled operating ranges (typically ~200–300°C for EO)

Monitoring continuously to avoid side reactions and safety risks

Proper temperature control ensures high selectivity, safety, and consistent product quality.

Gas recovery systems are technologies used to capture and reuse valuable gases that would otherwise be wasted or flared in industrial processes. In petrochemical plants, off-gas streams often contain a mixture of hydrocarbons and nitrogen.

Modern systems, such as membrane-based solutions, work by separating gases based on their permeability. The gas is compressed and cooled, then passed through membranes, where hydrocarbons permeate faster than nitrogen, producing a hydrocarbon-rich stream that can be reused as fuel while nitrogen is removed.

Gas recovery systems are critical because they help industries reduce waste, improve efficiency, and lower operating costs. Without recovery systems, valuable hydrocarbons are often burned in flare systems, resulting in energy loss and emissions.

By recovering these gases, plants can convert waste streams into usable fuel, reduce dependency on purchased energy, and minimize environmental impact. This also supports better resource utilization and overall process optimization.

Selecting the right gas recovery system depends on several factors, including gas composition, flow rate, pressure, and desired product quality. Facilities should evaluate whether their streams contain recoverable hydrocarbons and define their recovery goals.

Membrane-based systems are often preferred because they are compact, easy to install, and require minimal maintenance. Custom-designed solutions tailored to specific process conditions ensure optimal performance and maximum recovery efficiency.

Modern gas recovery systems, especially membrane-based technologies, are highly efficient and capable of recovering a significant portion of valuable hydrocarbons. These systems can produce fuel gas with low nitrogen content and high hydrocarbon concentration, making it suitable for reuse.

They also enhance overall plant efficiency by reducing hydrocarbon losses and improving fuel utilization, often delivering strong economic returns with simple operation and low energy requirements.

VCM recovery is critical because a significant amount of unreacted vinyl chloride monomer (VCM) is lost in vent streams during PVC production. These emissions are strictly regulated and often require incineration before release. Recovering VCM not only ensures environmental compliance but also allows manufacturers to reuse valuable raw material, improving overall process efficiency and reducing operating costs.

Membrane-based systems, such as VaporSep®, separate VCM from vent gases by allowing VCM to pass through the membrane faster than inert gases. This creates a VCM-rich stream (permeate) that is recycled back into the process, while the remaining gas (residue) is treated or incinerated. The recovered VCM is then condensed and reused in production, creating a closed-loop recovery system.

VCM recovery systems offer several key benefits:

Recover up to 90–99%+ of lost VCM

Reduce raw material losses and improve profitability

Minimize emissions and regulatory risks

Lower energy requirements compared to traditional methods

Compact, low-maintenance systems with no moving parts

These advantages make VCM recovery both economically and operationally efficient.

Membrane-based recovery systems are considered one of the most effective technologies for VCM recovery. Compared to conventional condensation alone, membranes achieve higher recovery rates and operate efficiently at moderate temperatures and pressures. They also offer a compact design and lower maintenance requirements, making them ideal for modern PVC plants.

VCM recovery supports sustainability by reducing harmful emissions, lowering the need for incineration, and minimizing waste. By recycling unreacted VCM back into the production process, it reduces the demand for fresh raw materials and improves resource efficiency. This leads to a cleaner, more sustainable PVC manufacturing process with a smaller environmental footprint.

Natural gas treatment is essential to remove impurities such as CO₂, H₂S, nitrogen, and heavy hydrocarbons so the gas meets pipeline and operational specifications. Untreated gas can reduce heating value, cause corrosion, and lead to operational issues. Proper treatment ensures safe transportation, improved efficiency, and compliance with industry standards.

Yes, natural gas treatment systems can be fully customized based on the composition of the raw gas and project requirements. Membrane-based solutions are particularly flexible and can be tailored to handle varying levels of CO₂, H₂S, nitrogen, and hydrocarbons to achieve optimal performance and meet specific pipeline or processing standards.

Yes, natural gas treatment can also assist in removing water vapor from the gas stream. Membrane systems and integrated treatment processes can reduce moisture content along with other contaminants, helping prevent corrosion, hydrate formation, and operational inefficiencies in pipelines and equipment.

Common technologies include membrane separation, amine treatment, adsorption (PSA), and cryogenic processes. Among these, membrane technology is widely used due to its simplicity, low operating cost, compact design, and ability to remove multiple contaminants in a single step.

Natural gas treatment increases the value of gas by removing non-combustible and harmful components like CO₂ and nitrogen, which lowers BTU value. By upgrading gas quality to pipeline standards and recovering valuable hydrocarbons, treated gas becomes more marketable and efficient for end-use applications.

Membranes play a key role by selectively separating impurities such as CO₂, H₂S, nitrogen, and heavy hydrocarbons from natural gas streams. These systems are quick to install, easy to operate, require minimal maintenance, and provide high efficiency with strong hydrocarbon recovery, making them a reliable and cost-effective solution for modern gas processing.

Fuel gas conditioning is necessary because raw gas often contains impurities such as H₂S, CO₂, nitrogen, and heavy hydrocarbons (C₃+) that can damage engines and turbines. These contaminants can cause corrosion, carbon buildup, and reduced fuel quality, leading to poor performance or even making the gas unusable. Proper conditioning ensures the gas meets required quality standards for safe and efficient operation.

Fuel gas conditioning improves operational efficiency by enhancing fuel quality and protecting equipment. It helps reduce maintenance costs, prevent unscheduled downtime, and improve the reliability of gas engines and turbines. Additionally, it eliminates the need for alternative fuels like diesel and ensures consistent performance in demanding environments.

Fuel gas conditioning commonly uses membrane-based separation technology, such as FuelSep™ systems. These membranes selectively remove impurities like CO₂, H₂S, nitrogen, water, and heavy hydrocarbons from the gas stream. The systems are compact, have no moving parts, and operate efficiently under ambient conditions, making them easy to install and maintain.

Yes, fuel gas conditioning can recover valuable hydrocarbons (such as C₃+ liquids) from the raw gas stream. Instead of being wasted, these components are separated and returned to the main gas stream for downstream recovery, helping maximize resource utilization and improve overall process economics.

Yes, fuel gas conditioning significantly reduces emissions. By removing heavy hydrocarbons and acid gases like CO₂ and H₂S, it lowers harmful exhaust emissions and helps maintain compliance with environmental regulations. It also reduces non-methane hydrocarbon (NMHC) emissions and minimizes environmental impact.

Nitrogen is removed because it reduces the heating value (BTU) of natural gas, making it less efficient and often unsuitable for pipeline transport or sale. High nitrogen content dilutes the energy content, so removing it ensures the gas meets commercial and pipeline quality standards.

The most common methods for nitrogen removal from natural gas include:

Cryogenic distillation – effective but complex and expensive

Pressure Swing Adsorption (PSA) – suitable for certain conditions

Membrane separation – a simpler, cost-effective solution, especially for small to mid-scale operations

Most natural gas pipelines require nitrogen content to be below approximately 4% to 6% to meet quality specifications. Gas exceeding this limit must be treated before it can be transported or sold.