Study On Gasification Characteristics And Kinetics Of Petroleum Coke

With the degradation of crude oil and increasing depth of petroleum processing, theoutput of petroleum coke from delayed coking process has rapidly increased. Thus, how toutilize petroleum coke in an efficient and clean way has been paid lots of attentions byrecent researchers. Petroleum coke used as the feedstocks of gasifier to produce syngas（CO+H₂） could realize the effective and clean utilization of petroleum coke. Thegasification characteristics and kinetics of petroleum coke was studied by using athermogravimetric analyzer （TGA）, a fluidized bed reactor （FBR） and a micro fluidizedbed reaction analyzer （MFBRA）, respectively. The main contents and achievements of thisstudy were summarized as follows.（1） The characteristics of petroleum coke gasification with CO₂were studied byusing TGA. The results showed that the gasification reactivity of petroleum coke was farlower than that of Fugu coal, even lower than that of graphite. Characterized by BET, SEM,XRD and FT-IR for its properties, it was found that prtroleum coke had poor pore structure,low specific surface area, high degree of graphitization and aromaticity, thus leading to itspoor gasification reactivity. Black liquor from paper-making industry can greatly improvethe gasification reactivity of petroleum coke and its catalytic effects were slightly lowerthan that of K₂CO₃and Na₂CO₃, but higher than CaO. The gasification reactivity ofpetroleum coke was found to be equal to that of Fugu coal when black liquor loadingamounts is10wt.%of the sum of black liquor and petroleum coke, demonstrating thatblack liquor can be an effective catalyst for petroleum coke gasification.（2） Steam gasification characteristics of petroleum coke catalyzed via black liquorwere investigated in a laboratory-scale FBR. The results showed that black liquor could notonly effectively improve the gasification reactivity, but also greatly enhance H₂content inthe produced syngas. The optimal loading amounts of dewatered black liquor were10wt.%of the sum of black liquor and petroleum coke, which could decrease the gasificationtemperature by about200℃when realizing the same gasification activity. Comparing withnon-catalytic gasification, the catalytic gasification rate of petroleum coke was5timeshigher and H₂content in the produced syngas was increased by8percentage points at thesame gasification temperature. The active components i.e., alkaline metals in the blackliquor, could destroy the aromatic C=C bonds in petroleum coke and meanwhile combinewith the carbon matrix of coke to generate a bulk of high-activity C（O） compounds, thus increasing the gasification rate. By facilitating the reactions of water gas shift and steammethane reforming, the gasification of petroleum coke catalyzed by black liquor formedmore hydrogen in the produced syngas.（3） The non-catalytic and catalytic gasification kinetics of petroleum coke with CO₂,steam and mixing atmosphere （oxygen/steam） as gasification reagent was studied inMFBRA, respectively. The results showed that the gasification rate of petroleum coke withthese three gasification reagents increased at higher reaction temperature and also smallparticle size was favorable for the higher gasification rate. The gasification rate ofpetroleum coke-steam was4times higher than that of petroleum coke-CO₂at the sametemperature, indicating better reaction activity of petroleum coke with steam. Addingpartial oxygen could accelerate the steam gasification rate of petroleum coke, but it existedan optimum value for producing high-quality syngas. The shrinking-core model （SCM）could accurately calculate the gasification kinetics of petroleum coke with CO₂, steam andmixing atmosphere （oxygen/steam）, their active energies for non-catalytic gasificationcalculated from SCM were186.50kJ/mol,120.04kJ/mol and100.43kJ/mol, respectively.At for the catalytic gasification condition, the activation energies decreased significantly, tobe153.30kJ/mol,76.55kJ/mol and62.97kJ/mol, respectively.