Study On Sorption-enhanced Steam Reforming Of Tar By CO₂ Sorbent

Coke oven gas is a by-product in coke oven coking process.Coke oven gas discharged from carbonization chamber of coke oven(700?900?)can not be used directly due to impurities such as tar.The presence of tar can cause problems such as pipe blockage,equipment corrosion and environmental pollution.At present,ammonia cooling is usually adopted in the industry to purify coke oven waste gas,but the gas temperature after spraying ammonia water will fall below 85 ?.resulting in a large number of high temperature sensible heat being wasted and water pollution.The main component of the coke oven gas is H2,and making use of coke oven gas to produce H2 is considered to be one of the most promising way of producing hydrogen.At present,with the coke oven gas waste heat been not fully utilized,the coal tar been wasted,and the current problems of huge investment existing in the process of hydrogen production from coke oven gas by pressure swing adsorption.Some scholars using sensible heat of coke oven gas self,realizes the tar catalytic reforming,CH4 reforming,water gas shift reaction and other series of reaction by high performance catalysts,but it still need pressure swing adsorption process to obtain high quality H2 by follow.On this basis,this paper proposes the method of sorption-enhanced steam reforming of tar to profuce H2.That is adsorbing the CO2 produced by catalytic reforming reaction of tar by adding the CO2 adsorbent in ord to obtain a higher concentration and yield of H2.Therefore,the preparation of efficient adsorbent is the key to the success of this process.This paper mainly includes:First,using immersion method,sol-gel method,solid-liquid method,coprecipitation method and solid-phase reaction method,by controlling the calcining time(2h,4h,6h),calcination temperature(900?,1000?,1100? and 1200?),the quality ratio of CaO and Ca12Al14O33(3:1,3:3,1:3)to prepare the sorbent with CaO as active material and Ca12Al14O33 as inert carrier,and the sorbent was characterized by XRD,SEM and BET to investigate the effects of preparation parameters on the physical properties of adsorbents.It was found that the 4h-calcination time,900?-calcination temperature,3:1 of the CaO and Ca12 Al14O33 mass ratio and sol-gel method are the best preparation parameters to prepare sorbent with he least impurity phase,the smallest grain,the highest porosity between grains and the highest specific surface area.Second,at the adsorption temperature of 680?,desorption temperature of 820?,the influence of preparation parameters on adsorbent adsorption capacity and cycle stability was investigated.The study found that the sorbent prepared by sol-gel method under 4h-calcination time,calcination temperature of 900?,3:1 of the CaO and Ca12Al14O33 mass ratio had the highest adsorption capacity(mass fraction 150.5%)and the best cycle stability,and after the adsorption/desorption cycles of 8 times adsorption capacity did not decreased significantly.Third,under the different ratio of water to carbon,tar reforming temperature and the WHSV conditions,using the optimized sorbent to carry on the experiment of sorption-enhanced steam reforming of tar.The study found that after joining the CO2 adsorbent,H2 concentration in different operating conditions were more than 95%,while the yield of H2 can be obviously improved.With the increase of the reaction temperature,hydrogen yields were increased first and then decreased,and the maximum was at 800?(87.35%).The higher the ratio of water to carbon was,the higher yield hydrogen had,and from an economic point of view,the water carbon ratio is most ideal at 12:1.With the WHSV decreased,the hydrogen yield increased,and from an economic point of view,the WHSV of 0.128h-1 is most ideal.