Many industrial processes such as printing, metal cleaning or painting produce waste air streams containing low concentrations of organic solvents, such as acetone, toluene, perchloroethane, xylene, etc. The total value of the solvent lost with the waste air is considerable. In addition, these solvents represent a significant pollution problem, and in recent years several procedures for recovering solvents from air, such as carbon adsorption, incineration, etc. have been introduced in the industry. All of them show some draw-backs in terms of efficiency, reliability and costs. In this paper a membrane process is described, which provides an attractive alternative to the conventional methods. In a basic study the permeabilities of acetone, toluene, xylene, dichloroethane and dichloromethane through a homogeneous polydimethylsiloxane (PDMS) membrane have been determined using a pressure difference between 400 and 1000 mbar as driving force. The selectivity of the membrane for the various solvents and their dependence on the solvent concentration in a mixture with nitrogen were studied.

The selectivities of the PDMS membrane for the solvent/nitrogen mixtures were in the range of S = 70-160, depending on the solvent and its concentration in the feed mixture. Based on these data a pilot plant process has been designed in which a solvent is recovered from a waste air stream and the depleted air is recycled into the waste air producing process. The solvent which has permeated the membrane is recovered as a liquid by condensation. Thus, complete recycling of air and solvents is possible. In a cost analysis it has been demonstrated that the membrane process is indeed an attractive alternative to conventional air cleaning techniques.

Read the full research of Removal of organic vapors from air

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“VOC” (volatile organic compounds) is a general term for organic compounds that are volatile and become gases in the atmosphere. It includes various substances such as gasoline, toluene, and chlorofluorocarbons. These substances are known to cause air pollution related to photochemical oxidants and are related to ozone layer depletion and global warming. Emission regulations have been taking shape in Europe and the United States. The emission regulations have been started in Japan on April 1, 2006.

No need to mention the petroleum through vents, most VOCs are contained as solvents in adhesives, paints, inks, etc., they are discharged from chemical product manufacturers and printing-related facilities. Also, electronic parts and metal processing manufacturers use VOCs as cleaning agents.

There are two types of VOC emission countermeasures: combustion treatment and separation / recovery treatment. The separation / recovery method includes adsorption by activated carbon and membrane separation operation with selective permeable membrane.

NAGASEP is a separation membrane module made of a single material of silicone rubber and has excellent properties for separating and concentrating VOCs. Membrane separation is a process that takes advantage of specific selective permeability of silicone membrane to the target component.

The device has a simple structure in which a vacuum pump and a steam recovery container are installed besides the membrane module, and VOCs can be continuously concentrated and recovered by depressurizing the permeation side of the membrane at atmospheric pressure on the gas supply side.

NAGASEP is a separation membrane module made of a single material of silicone rubber and has excellent properties for separating and concentrating VOCs. Membrane separation is a process that takes advantage of specific selective permeability of silicone membrane to the target component.

The device has a simple structure in which a vacuum pump and a steam recovery container are installed besides the membrane module, and VOCs can be continuously concentrated and recovered by depressurizing the permeation side of the membrane at atmospheric pressure on the gas supply side.

In the picture below you could see the permeability of VOCs in NAGASEP.

The post Separation, concentration and recovery of volatile organic compounds appeared first on NAGASEP.

In a 20℃ environment, oxygen can dissolve at 8ppm nitrogen at 15ppm. When temperature arise, less air dissolve in water. The dissolved oxygen is necessary for the creatures living underwater, but since oxygen would create scale buildup and corrosion of the pipes, for industries it’s ideal to remove the oxygen from water.

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