MTR's membrane systems enable operators to do the following:
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For each application, MTR:
In summary, MTR does everything from initial concept to commissioning except the field installation work.
The VaporSep process combines a compression-condensation step with a membrane separation step. The feed gas - a mixture of hydrocarbons in nitrogen, hydrogen, or methane - is compressed and cooled, condensing a portion of the hydrocarbons in the gas. The liquid hydrocarbons are recovered; the remaining gas, which still contains significant amounts of hydrocarbons, is fed to the VaporSep membrane. The membrane separates the gas into a hydrocarbon-rich permeate stream and a hydrocarbon-depleted residue stream (the purified gas). The permeate is recycled to the compressor; the residue stream is vented or reused.
VaporSep membranes separate gas mixtures on the basis of solubility. Large hydrocarbon molecules with greater solubility in the membrane permeate much faster than smaller, less soluble molecules such as nitrogen, hydrogen, or methane.
By comparison, conventional membranes separate gases on the basis of size. Small molecules are selectively permeated because they diffuse through the membrane more rapidly than large molecules.
VaporSep membranes are manufactured as flat sheets and rolled into spiral-wound modules. The feed gas enters the module and flows between the membrane sheets. Spacers on the feed side and the permeate side of the membrane sheets create flow channels. The hydrocarbon vapor that passes preferentially through the membrane flows inward to a central permeate collection pipe. The light gas (nitrogen, hydrogen or methane) is rejected by the membrane and exits as the residue.
Spiral-wound membrane module
Modules are 3 feet long and 4 to 8 inches in diameter. As many as 4 modules are placed in pressure vessels designed to meet local standards (ASME, etc). To meet the needs of a particular application, modules are configured in series and parallel flow combinations.
VaporSep membrane separation systems are used in the petrochemical, refining, and natural gas processing industries. Current applications include the following:
The membrane module can operate over a wide range of temperatures and pressures. The temperature range is -40°C to 40°C. The feed pressure can be as high as 1,500 psi. The permeate pressure can be under vacuum if required to achieve a certain separation.
Several factors determine the required pretreatment. If dust or other solid particles are present, they must be removed upstream with a high-efficiency filter. If the feed gas contains entrained liquids, a mist eliminator vessel with a high-efficiency coalescing agent is required. MTR will provide detailed pretreatment requirements.
MTR will provide a standard piping and instrumentation diagram (P&ID) showing recommended control systems and instruments for the membrane and pretreatment equipment. MTR can review and approve customized control systems for special applications.
Membrane systems can be operated down to 20% of design capacity.
Large membrane systems may consist of multiple skids and subsystems, such as a compressor package, a dryer package, and a refrigeration package. The footprint of a skid may be as large as 30 feet long by 12 feet wide. Since every system is custom designed, the footprint may be reduced to fit the customer's requirements. Individual skids weigh as much as 25 tons.
With proper operation and maintenance, a VaporSep membrane should have a lifetime of 3 to 5 years. When replacement is necessary, the membrane module is easily replaced without the need for special tools or expertise.
The payback time is typically 6 to 12 months, depending on the application.
In the pervaporation process, a liquid mixture contacts the membrane, which preferentially permeates one of the liquid components as a vapor. The vapor enriched in the more permeable component is cooled and condensed, spontaneously generating a vacuum that drives the process. MTR's pervaporation systems use proprietary membranes to separate dissolved volatile organic compounds (VOCs) from aqueous solutions. The membrane selectively permeates the organic compound, producing a concentrated permeate stream that contains the organic component of interest and an organic-depleted residue stream. The dissolved organic may be a high-value component, such as a food essence, or a contaminant, such as a chlorinated solvent.
PerVap membrane separation systems are used in food processing and water treatment. Examples of applications include the following: