The core working principle of the deoxygenation membrane equipment is based on Henry's Law and the gas-liquid mass transfer process. Henry's Law states that at a constant temperature, the equilibrium concentration of a dissolved gas in a liquid is directly proportional to the partial pressure of that gas in the gas phase. The equipment uses a hydrophobic microporous hollow fiber membrane as the gas-liquid contact interface, creating a dissolved oxygen concentration gradient across the membrane that drives oxygen molecules to migrate from the liquid phase to the gas phase.
The membrane material is selected from hydrophobic polymers such as polypropylene (PP) or polyvinylidene fluoride (PVDF). The pore size of the membrane micro-pores ranges from 0.01 to 0.1 micrometers. The hydrophobic nature prevents the water phase from penetrating the membrane pores, while gas molecules dissolved in the water can freely pass through the membrane pores into the gas phase side.
The equipment provides two process modes:
A vacuum pump creates a negative pressure environment on the gas phase side of the membrane module, bringing the oxygen partial pressure on the gas phase side close to zero. Water containing dissolved oxygen flows on the liquid phase side of the membrane module. Driven by the partial pressure difference, oxygen molecules pass through the membrane pores into the gas phase side and are continuously discharged by the vacuum pump. In this mode, the outlet dissolved oxygen concentration can be reduced to below 1 μg/L.
High-purity nitrogen gas (purity ≥ 99.999%) is introduced into the gas phase side of the membrane module as a sweep gas. The high-purity nitrogen maintains an extremely low oxygen partial pressure on the gas phase side. Driven by the concentration gradient, dissolved oxygen in the liquid phase passes through the membrane pores into the gas phase side and is discharged along with the sweep gas. In this mode, the outlet dissolved oxygen concentration can be reduced to below 5 μg/L.
The two modes can be selected based on actual operating conditions. The vacuum mode is suitable for applications with strict requirements for outlet dissolved oxygen levels; the nitrogen sweep mode is suitable for sites with a stable supply of nitrogen. The equipment can operate within a temperature range of 5 to 40 degrees Celsius, with an inlet water pressure range of 0.1 to 0.5 MPa.
The deoxygenation membrane equipment consists of a membrane contactor unit, a vacuum system or sweep gas system, and piping and control systems. The membrane contactor is the core component of the equipment, internally packed with hollow fiber membranes arranged in bundles, with both ends potted and fixed using epoxy resin, and the whole assembly enclosed in a stainless steel or engineering plastic housing. The housing has four ports: two for the liquid phase and two for the gas phase.
The liquid phase side is equipped with an inlet and an outlet. Water flows either inside or outside the membrane fibers, resulting in either an inside-out or outside-in flow path design depending on the membrane module configuration. The gas phase side is equipped with a vacuum port or sweep gas inlet/outlet ports. The vacuum mode is equipped with a liquid-ring or rotary vane vacuum pump; the sweep mode is connected to a nitrogen supply line. The control system includes flow control valves, pressure gauges, vacuum indicators, and online dissolved oxygen monitors for real-time monitoring of equipment operating parameters.
The deoxygenation membrane system is connected in series after the Reverse Osmosis (RO) or Electrodeionization (EDI) module. Process flow: RO/EDI permeate enters the feed pump, is pressurized, and sent to the shell side of the deoxygenation membrane, producing deoxygenated water. The auxiliary system consists of a vacuum unit and a sweep gas unit. The vacuum system includes a liquid-ring vacuum pump or dry screw vacuum pump, a gas-liquid separation tank, and a circulating water tank; the sweep gas system includes nitrogen cylinders, a pressure reducing valve, and a mass flow controller.
For conditions requiring product water dissolved oxygen below 5 ppb, a two-stage series process is used: the first stage membrane tube side is connected to a vacuum pump, and the second stage membrane tube side uses nitrogen sweep combined with vacuum. The inlet water quality must meet: turbidity < 1 NTU, total suspended solids < 5 mg/L, residual chlorine < 0.1 ppm, to prevent membrane surface fouling and blockage, as well as oxidative degradation of the polypropylene material. The PLC control system collects data on inlet flow rate and product water dissolved oxygen, and uses PID algorithms to adjust the vacuum pump frequency and sweep gas flow rate, maintaining product water quality while reducing operating energy consumption.
Dissolved oxygen removal step in ultrapure water preparation for the electronics and semiconductor industry.
Boiler makeup water deoxygenation in the power and heating industry, replacing thermal deaerators or chemical deoxygenation processes.
Deoxygenation treatment in the preparation of water for injection and purified water for the pharmaceutical industry.
Deoxygenation of production water in the food and beverage industry to delay product oxidation and deterioration.
Deoxygenation of injection water in the petrochemical industry to reduce the dissolved oxygen corrosion rate in water injection systems.
Deoxygenation of water for laboratory analysis and precision cleaning applications.
The system operates on Henry's Law and gas-liquid mass transfer. Using hydrophobic microporous hollow fiber membranes, it creates a dissolved oxygen concentration gradient across the membrane barrier, allowing dissolved oxygen molecules to pass freely into the gas phase side while completely blocking the liquid phase.
Vacuum Deoxygenation Mode pulls negative pressure on the gas side, reducing dissolved oxygen down to below 1 μg/L, which is optimal for critical standards. Nitrogen Sweep Mode introduces ultra-pure nitrogen (≥ 99.999%), reducing dissolved oxygen to below 5 μg/L, suitable for facilities with an established nitrogen supply.
To prevent membrane fouling and avoid chemical degradation of the polymer materials, the inlet water must have a turbidity < 1 NTU, Total Suspended Solids (TSS) < 5 mg/L, and residual chlorine < 0.1 ppm. The system is typically installed directly downstream of RO or EDI modules.
The standard operational temperature range is 5 to 40 degrees Celsius, with an allowable inlet water pressure between 0.1 and 0.5 MPa.
For strict standards below 5 ppb, a two-stage series configuration is deployed: the first stage membrane utilizes a vacuum pump, and the second stage combines nitrogen sweep gas with vacuum extraction, dynamically modulated by a PLC-based PID loop.
Key applications include ultrapure water for electronics/semiconductors, boiler feedwater deoxygenation (replacing thermal/chemical systems), pharmaceutical WFI and purified water, food/beverage anti-oxidation, petrochemical injection water corrosion mitigation, and precision laboratory cleaning.