Study On The Promoting Effect Of Palladium Membrane Hydrogen Permeation And Carbon Dioxide Adsorption On Steam Reforming Of Fluidized Coke Oven Gas For Hydrogen Production

Coke oven gas was a by-product of gas production in coke production.About 21billion Nm³ of coke oven gas is produced each year,its main component gases are CH₄?23%?27%?and H₂?55%?60%?.In the traditional industry,hot coke oven gas?HCOG?was cooled and separated to remove liquid chemicals,resulting in a large amount of thermal energy and chemical energy being wasted.Through steam reforming and water gas shift reaction,the amount of hydrogen production from the steam reforming of HCOG would be several times more than the amount of hydrogen in HCOG.Therefore,it is of great significance to produce hydrogen from hot coke oven gas by catalytic reforming.There had been few reports on the hydrogen production from hot coke oven gas by catalytic reforming in the past few years,and relatively less research on the application of fluidized bed membrane reactor?FBMR?to hot coke oven gas reforming to produce hydrogen.This study described the experimental explorations on the effect of gas extraction via immersed tubular membrane on the hydrodynamics in a pilot-scale gas fluidized bed membrane reactor?FBMR?at high temperatures.Based on the hydrogen production from hot coke oven gas by catalytic reforming,a method of synergistic strengthening of the steam reforming process by hydrogen membrane separation and carbon dioxide adsorption in a fluidized bed membrane reactor?FBMR?was adopted.This work had studied on promoting effect of carbon dioxide adsorption and palladium membrane on steam reforming of fluidized coke oven gas for hydrogen production through the design of various experimental conditions and the collection and analysis of experimental data by means of simulated coke oven gas?25%CH₄-75%N₂,26%CH₄-21%H₂-8%CO-45%N₂?.Differential pressure signals were measured at different vertical intervals in the bed and were then characterized by different methodologies including multiscale resolution and power spectra analysis.The experimental results showed that the gas extraction resulted in more complex effects on the hydrodynamics in the FBMR at elevated temperatures than at room temperature.The relative amplitude of?_r(?/x_av)of the differential pressure tended to decrease with the increase in the gas extraction fraction for each constant operating temperature,which indicated that the gas extraction decreased the average bubble size in the FBMR irrespective of the temperature.The experimental results showed that the emergence of turbulent fluidization occurred more rapidly at higher temperatures.At room temperature,the defluidization was caused by 20%gas extraction at an inlet velocity of 2U_mf.However,at high temperatures and under the same operating conditions,the gas extraction simultaneously decreased the magnitude of the low-frequency components?0.6?0.9Hz?and the numbers of the medium-to small-sized structures.This suggested that the gas extraction profoundly decreased the excess gas in the fluidized bed,thereby decreasing the number of small-sized structures and inhibiting the integration of bubbles.The effects of the gas extraction on the bubble properties in the FBMR increased with an increase in the gas extraction fraction and slightly decreased at higher inlet gas velocities.At elevated temperatures,the D6 sub-signals?0.781?1.562Hz?represented the highest percentage of the wavelet energy distribution of the differential pressure signals at high temperatures,which meant that the medium-to small-sized bubbles dominated the gas-solid flow dynamics and the gas extraction enhanced the dominance of the D6 scale components.At room temperature,the gas extraction caused the wavelet energy to be concentrated in the A8 level sub-signals,which was related to global phenomena at the scale of the FBMR system,e.g.,the compression wave from the gas supply systems.In experiment 2,a fixed-bed tube furnace was used as the experimental reactor,and hydrogen was produced by simulated coke oven gas reforming?25%CH₄-75%N₂?.The CH₄ conversion in the reforming experiment reached more than 95%,which proved that nickel-based catalyst had good catalytic activity for methane steam reforming,so the catalyst was used for the follow-up experiments.In the simulated coke oven gas reforming hydrogen production experiment 3?25%CH₄-75%N₂?,the nickel-based catalyst and calcined dolomite were used as experimental catalysts and CO₂ adsorbents.Under the operating conditions of different temperature and volume ratio of catalysts and adsorbents,the GC gas chromatograph was used to record the proportion of gas in each component of the experimental tail gas.The volume fraction of N₂ was used as the reference system to analyze the factors affecting CH₄ conversion in coke oven gas.In the sweep gas on hydrogen permeation experiment,in-situ separation of hydrogen via a palladium membrane tube,the promotion of hydrogen production from CH₄ conversion in coke oven gas was studied.Experiments have shown that the appropriate high temperature facilitated the hydrogen production reaction,and had increased the CH₄ conversion rate from 60%to over 90%.At the same time,the CO₂ adsorbent was added in the mixed gas,and the CH₄ conversion rate could reach 95%,but the adsorption effect of the CO₂ adsorbent was not sustained,which resulting in a decrease in the CH₄conversion rate.Under suitable operating conditions,at 560°C,the palladium membrane could greatly improve the CH₄ conversion rate in coke oven gas,which could reach 95%,but the CH₄ conversion rate decreased sharply in the later stage of the experiment,which was related to the hydrogen permeability stability of the palladium membrane.This is a major problem that hindered the improvement of CH₄conversion rate.Based on the experiment data,the component of the mixed gas was appropriately changed?26%CH₄-21%H₂-8%CO-45%N₂?,a certain proportion of CO and H₂ were added to simulate the coke oven gas.The experiment 4 proved that the addition of CO and H₂ would inhibit the CH₄ conversion rate in the mixed gas.Moreover,the inhibition effect of CO on CH₄ conversion rate in the mixed gas was stronger than that of H₂.However,the promoting effect of carbon dioxide adsorption and palladium membrane on steam reforming of fluidized coke oven gas for hydrogen production was still very obvious.The conversion rate of CH₄ in the mixture could reach 90%.In the experiment,the amount of hydrogen in the permeate side was one order of magnitude smaller than hydrogen production from simulated hot coke oven gas by catalytic reforming.?0.0038L/min-0.15L/min?...