Using membrane separation for CO2 removal in syngas

It is now feasible to separate CO2 using membrane separation technology; it depends on what process requirements your equipment has. The working principle of membrane separation is to use a polymer membrane to selectively \"filter\" the feed gas in order to achieve separation. When a mixture of two or more gases passes through a polymer film, the differences in the solubility and diffusion coefficients of each gas component within the polymer result in different rates of penetration through the membrane wall. Thus, gases can be divided into \"fast gases\" (such as H2O, H2, He, etc.) and \"slow gases\" (such as N2, CH4, and other hydrocarbons). When the mixed gas permeates under the drive force of the partial pressure difference of the corresponding components on both sides of the membrane, gases with a relatively fast permeation rate pass through the membrane wall first and become concentrated on the low-pressure permeation side, while gases with a relatively slow permeation rate become concentrated on the high-pressure retention side.

It is used for carbon dioxide recovery, primarily to facilitate the extraction of oil and the separation of carbon dioxide from natural gas. Monsanto, Dow, and Grace all have such devices; the higher the carbon dioxide concentration during the separation process, the more favorable it is for recovery. We specialize in gas separation membranes; separation is definitely possible, but the effectiveness will depend on the specific circumstances of the client~!

I’m providing the original poster with two papers that are not closely related to natural gas separation, but they should help in understanding this process. But how do I add a PDF attachment? ?

I posted it in “Membrane Separation, Pressure Swing Adsorption, and Cryogenic Technologies Discussion Forum » Membrane Separation, Pressure Swing Adsorption, and Cryogenic Technologies Sharing Area » Removal of Sulfides by Membrane Methods”. By the way, is posting like this in compliance with the rules? ?

I highly recommend the use of membrane separation CO2 technology, as it is environmentally friendly, energy-efficient, easy to operate, and holds great promise.

If the concentration is not very high, the cost becomes too high. So far, there are no known examples in China of any place using membrane methods to recover carbon dioxide.

I haven’t heard of any examples in China where membrane technology is used for carbon dioxide recovery.

Is it feasible to use the method of \"physical absorption in liquid + membrane degassing\"? It can save a lot of energy.

'For physical absorption of liquids, organic solvents are used, and low temperatures or high pressures are generally required. Is it necessary to degas the carbon dioxide-containing solvent obtained in this way using a membrane? What kind of membrane can be used for degassing? Even the membranes that come to mind do not possess high CO2/(polar) solvent selectivity. I’m not sure if I understand correctly

3.2 Membrane separation technology: Gas membrane separation is a new type of chemical separation technique. It utilizes the pressure difference between the gases on either side of the membrane as a driving force, allowing CO2 to dissolve and permeate through the membrane. This results in a decrease in the concentration of CO2 on the side where the membrane material is located, while CO2 becomes concentrated on the other side of the membrane, thereby achieving the goal of removing CO2 from natural gas. This process offers advantages such as low energy consumption, minimal initial investment, compact equipment, small footprint, high operational flexibility and simplicity, easy maintenance, and the ability to scale up the equipment. It is an efficient, energy-saving, and environmentally friendly emerging technology that has become an important area of research and development in the fields of energy and the environment. It is highly effective in addressing issues such as natural gas purification, recovery, and utilization in the oil industry, as well as in reducing production costs. This project was designed and manufactured for CO2 removal from natural gas in Hainan, and is implemented by the Dalian Institute of Chemical Physics, Chinese Academy of Sciences. The membrane separation system consists of pretreatment and membrane separation. The preprocessing section mainly includes components such as a gas-liquid separation system and a heating system. After pre-treatment to remove particles and oil mist, the natural gas is preheated before being fed into a membrane separator for treatment; concentrated CO2 gas (permeate) is obtained on the low-pressure side ； On the high-pressure side, natural gas exhaust (decarbonized gas) is obtained and fed into the customer’s pipeline network. The raw natural gas comes from a single-well gas field, with the gas well being at a depth of approximately 3,800 meters. The membrane separation unit is designed with a daily processing capacity of 4×104 Nm3/d, an operating pressure of 5.1 MPa, a temperature of 36°C, and a CO2 content in the gas of approximately 81 Vol%, with a CH4 content of about 15 Vol%. Other components also include N2, C2–C6+, and saturated water vapor. It is required that the flow rate of the recovered natural gas (decarbonized gas) after treatment be no less than 350 NM3/h, with a CO2 content of 20–25 Vol%, and the natural gas pressure to be ≥2 MPa. The device consists of a pretreatment module and a membrane separation module; the pretreatment module has an area of approximately 8m×3m, while the membrane separation module has an area of about 2.5m×2.3m. The pretreatment module includes gravity separation and high-efficiency gas-liquid separators, multi-stage precision filters, and water-jacketed heaters, among others. The membrane separation module consists of a primary membrane separation process and a secondary membrane separation process, comprising a total of four inlet membrane separators with a diameter of 200 mm. Among them, the primary membrane separation process consists of two membrane separators connected in parallel, while the secondary membrane separation process consists of two membrane separators connected in series. This device is the only one in China that utilizes membrane separation technology for CO2 separation, and it is also the natural gas membrane treatment unit of its kind in the world capable of handling the highest concentrations of CO2. The successful application of this technology indicates that China’s technology for separating CO2 from natural gas using membrane technology has reached the forefront of the world. Since it was put into operation (July 18, 2007), it has been functioning properly for nearly 9 months, having processed a total of 1260×104 Nm3 of natural gas. Use membrane technology to reduce the CO2 concentration in natural gas from 20% to below 3%. The process unit consists of components such as cyclone separation, multi-stage precision filtration, heating, and membrane separation. The processing capacity is 2,100 NM3/h; based on an annual operating time of 8,000 hours, the annual processing volume amounts to 16.8 million NM3/year, with 12.7 million NM3/year of natural gas recovered. The membrane separation system consists of three parts: a compressor, pretreatment, and membrane separation. The pretreatment section mainly includes: a cyclone demister, multi-stage precision filters, and heating with a water-jacketed furnace. Natural gas is passed through a cyclone demister, a primary pre-filter, and two stages of precision filters to remove particles and oil mist; this process enables the level of heavy hydrocarbons in the natural gas to be reduced to below 0.1 mg/m3, and it also removes all solid particles with a diameter greater than 0.01 μm ； After being heated in a water-jacketed furnace, it enters the membrane separator for separation. First, enter the first-stage membrane separator M-01 for separation. On the high-pressure side, exhaust gas (non-permeate) is obtained; this non-permeate can be integrated into the user’s pipeline network. On the low-pressure side, CO2 (permeate) is produced, which is then compressed to 2.0 MPa and fed into the secondary membrane separator M-02 for separation. The resulting secondary exhaust gas is sent back to the raw gas side for further separation, in order to improve the recovery rate of natural gas. To treat natural gas containing 20% CO2, about 9 membranes are required, at 800,000 each; the supporting equipment and instruments cost around 3 million. To treat 50% of CO2, approximately 11 membranes are needed, at 800,000 per membrane, while the supporting equipment and instruments cost around 3 million. The depreciation period for membranes is 7 years, and for equipment it is 20 years. The operating cost can be calculated based only on the electricity cost for the compressor; other electricity costs can be excluded. It is not economical to use membrane treatment for 80% CO2-containing natural gas.