Hybrid Process Of Membrane Separation And PSA For Hydrogen Recovery Of High Yield And High Purity From Refinery Gas

As more and more attention is paid to the living environment of people, the fuel standards in our country are continuously improved, and motor gasoline, diesel oil measures such as control of sulfur, olefins, aromatics content is more and more strict. However, a lot of heavy crude oil with sulfur and acid is used to reduce procurement costs, and clean hydrogenation technology is the main measure in order to solve the problem. Now the problem is that the consumption of hydrogen dramatically increases year by year, and the hydrogen cost has become the second-most expensive, after the crude oil refining process cost. At the same time, the tail gas with hydrogen is used as fuel gas in the processing of crude oil, or the separation of the existing recycling process is a single, which leading to the low recovery rates of hydrogen and light hydrocarbon,, and it produces a great waste of hydrogen and light hydrocarbon. As a result, for the hydrogen recovery of refinery tail gas, this paper presents that using membrane separation and pressure swing adsorption (PSA) process of the coupling technology to realize refinery tail gas of high yield of high purity hydrogen component in recycling, which can meet the needs of clean fuel production, reduce the hydrogen production unit load, saving resources and reducing energy consumption.Hydrogen separation membrane (HM) is added to recycle the existing exhaust gas in the original pressure swing adsorption device. Single-stage membrane and PSA recycling process are designed respectively to recycle the desorbed gas of the original PSA device and other refinery tail gas. Based on this, two-stage membrane and PSA recycling process are proposed, and the second stage membrane separating unit is used to recycle the retentate side gas of the firs stage membrane to increase the hydrogen recovery rate. In order to further increase the hydrogen recovery and PSA device utilization rate, two-stage membrane and PSA of the coupling technology is proposed, using the first stage hydrogen separation membrane to process the raw material of reformer hydrogen with higher hydrogen concentration, high purity hydrogen gas product can be obtained directly, the second stage membrane is used to process the tail gas with low hydrogen concentration and the retentate side gas from the first stage membrane, which can increase the hydrogen concentration to 90%, and then hydrogen gas is purified and recycled as a feedstock for PSA device, so as to realize high recovery of high purity hydrogen yield.Three kinds of process are simulated and optimized by UniSim Design software. The influence of feed pressure, operating pressure ratio and other operation parameters on the results of hydrogen recovery and economic benefit is considered, it can be found that membrane area needs less with bigger operating pressure and pressure ratio to get higher hydrogen recovery. Under different operating conditions, three kinds of tail gas recovery process are calculated for economic accounting respectively. It needs to add a membrane separation device with 9561m2 membrane area in single-stage membrane separation process, so as to get hydrogen gas product concentration 98 mol%, and the increment of hydrogen recycle is 4683 t every year, the increment of hydrogen recovery is from 71.86% to 96.63%, the increment of annual earnings is 1.68 X 108 CNY. The hydrogen recovery is 97.51% using two-stage membrane and PSA, the recovery is about 25% higher than the single PSA process, the membrane area of this process is 24197m2, and the membrane area of the first stage is same with the single-stage membrane separation process, for each year, the hydrogen recycle is 148688 t, and the total revenue is 7.85 X 108 CNY. The membrane area is 21335 m2 using two-stage membrane and PSA of the coupling technology, which achieves the requirement of the hydrogen gas product concentration 99 mol%, the hydrogen recovery is 97.67%, and the total revenue is 7.28 × 108CNY.The results show that pressure and operating pressure ratio has a direct influence on economic benefits in different technological processes when recycle the hydrogen in the refinery gas, the membrane and PSA coupling process with relatively complex structure make full use of the complementary advantages of membrane separation and PSA device, which is helpful to improve the concentration of hydrogen and hydrogen recovery of product, and increase the economic benefit.