Membrane separation technology

The membrane separation method takes the selective osmosis membrane as the medium, and selectively permeates the membrane under the drive of potential difference, pressure difference and concentration difference to achieve the purpose of separation and purification.

① Palladium membrane diffusion method: at a certain temperature, hydrogen molecules dissociate into hydrogen atoms on one side of the palladium membrane, dissolve in palladium and diffuse to the other side, and then combine into molecules. After separation, the purity of hydrogen can reach 99.99%. The palladium alloy purification process has strict requirements on the content of oxygen, water, heavy hydrocarbons, hydrogen sulfide and olefins in the feed gas. Oxygen catalyzes hydrogen and oxygen reaction on the surface of palladium alloy membrane, which generates a lot of heat, causing the palladium alloy membrane in the diffusion chamber to overheat and damage. Water, hydrogen sulfide, olefins and heavy hydrocarbons will seriously poison the surface of palladium alloy. Before hydrogen enters the palladium membrane, oxygen will drop to 0. 1ppm, the quality of water and other impurities is reduced to below 1ppm,. The osmotic pressure of palladium membrane is usually 1 before the membrane. 4-3. 45MPa, post membrane pressure 448-690kpa. As palladium is a precious metal, this method is only applicable to small occasions with high requirements for hydrogen purity.

② Organic hollow fiber membrane diffusion method, including polysulfone, polyimide, polycarbonate, etc.

③ The hollow membrane separation hydrogen recovery unit is widely used in ammonia purge gas, methanol unit tail gas and various tail gas in the refining process. The organic hollow fiber membrane separation process can utilize the self pressure of the exhaust gas and take the pressure difference on both sides of the membrane as the driving force.

The tail gas of ammonia plant must be deammoniated before entering the membrane module. The ammonia content is reduced to below 200ppm. Prevent ammonia expansion from damaging the membrane.

Low-temperature separation

① The principle of low temperature cooling is that the boiling points of hydrogen and other gases differ greatly. It is a separation method that condenses all high boiling components except hydrogen into liquid at working temperature. It is applicable to recovering hydrogen from feed gas with hydrogen content of 30-80%. The purity of hydrogen production is 90-98%.

② Low temperature adsorption from electrolytic hydrogen or purity 99. High purity hydrogen and ultrapure hydrogen with a purity of 99.99% can be produced from 9% industrial hydrogen..

Generally, two tower streams are used, one tower is used for adsorption, the other tower is used for regeneration, and the cycle is switched regularly. The PSA operates continuously. The process flow is simple, the degree of automation is high, the cost of operation and maintenance is low, and the product purity is highly adjustable. The unique advantage of simultaneous removal of multiple impurity components by one separation.

Pressure swing adsorption (PSA) technology is based on the physical adsorption of gas molecules on the internal surface of a specific adsorbent (porous solid material). With the characteristics of the adsorbent that is easy to adsorb high boiling point components, difficult to adsorb low boiling point components under the same pressure, and the adsorption capacity increases under high pressure and decreases under low pressure, the feed gas is selectively adsorbed by passing through the adsorption bed under a certain pressure, and the high boiling point impurity components relative to hydrogen are selectively adsorbed, Hydrogen with low boiling point is not easy to be adsorbed and passes through the adsorption bed to achieve the separation of hydrogen and impurity components. The process of four towers and two homogenization is adopted for hydrogen purification. Lanbo purification technology of the company adopts PSA hydrogen production technology.

Metal hydride method

The high-purity hydrogen with purity of 99.99% is produced. The selectivity of hydrogen storage alloy to hydrogen is used to generate metal hydride. Other impurities in hydrogen are concentrated outside the hydride and discharged with waste gas. Hydrogen is released from metal hydride separation. The hydrogen is purified. Two and four are often combined to work continuously.

The process includes hydrogen absorption and desorption, and hydrogen absorption at low temperature and high pressure Hydrogen release at high temperature and low pressure.

Catalytic deoxidation

With palladium or platinum as catalyst, oxygen and hydrogen react to generate water, which is dried and dehydrated with molecular sieve. It is especially suitable for deoxidation and purification of electrolytic hydrogen, and can produce high-purity hydrogen with a purity of 99.99%.