Coproduction of liquids and syngas via residue oil cracking-coke gasification (RCCG) process

Due to the extinction of conventional oil resources, large portions of heavy oil will be exploited and processed in the refinery, thus in-return generating more degraded residue oil. Fluid catalytic cracking (FCC) process is unable to treat such kind of residue oil because of rapid catalyst deactivation and excessive coke deposition. Delayed coking, featured with wide feed adaptation and low investment, has been widely used for treating petroleum residues in China. Nonetheless, delayed coking has low liquid yield and produces low-value petroleum coke. As a result, a so-called residue cracking–coke gasification (RCCG) process was proposed to realize the hierarchical conversion and value-added utilization of petroleum residues. Heavy oil was first cracked in a fluidized bed reactor via contacting with the catalyst particles to maximize the liquid yield. Coke deposited on the surface of catalysts was gasified and/or combusted for catalyst regeneration. Simultaneously, high-quality syngas could be produced via coke gasification and further used as the hydrogen source for liquid oil upgrading. The regenerated hot catalysts circulated back to the cracking reactor, providing heat and also catalytic activity for heavy oil conversion. Cracking behaviors of Venezuela vacuum residue were studied in a self-designed fluidized bed reactor (Fig. 1) with spent FCC catalyst to optimize operation parameters for high liquid yield and conversion of heavy fractions. The results showed that the hydrothermal-treated FCC catalyst (A-FCC) showed reasonable activity for residue oil cracking to ensure the acceptable liquid yield and low coke formation. The residue oil conversion above 90% and liquid yield over 75 wt.% were obtained under the operation conditions of 520℃, catalyst-to-oil mass ratio of 6.17 and steam-to-oil mass ratio of 0.6 using A-FCC catalyst. Two methods of catalyst regeneration were used in batch operation, i.e., steam gasification and gasification coupled with combustion of the deposited coke on the catalyst. Steam gasification of the deposited coke was performed at 800℃ for the catalyst regeneration, and the total volume fraction of CO and H2 was up to 86 vol.%. In comparison with coke gasification, catalyst regeneration via gasification-combustion was shown to be able to shorten the required reaction time by about 40% (see Fig. 2), while the regenerated A-FCC catalyst manifested the catalytic activity similar to that of the original A-FCC catalyst. RCCG process is characterized with higher liquid yield and lower coke production than that of delayed coking, and also could process heavy feed oil and produce syngas comparing with FCC process, thus justified its technology advantages. Please click Additional Files below to see the full abstract

CHARACTERISTICS AND KINETICS OF BIOMASS PYLOLYSIS IN A MICRO FLUIDIZED BED REACTOR

A Micro Fluidized Bed Reactor (MFBR) was developed to enable on-line pulse feeding and isothermal differential reaction of particle reactant. Application of the MFBR to biomass pyrolysis demonstrated that the resulting globe kinetics parameters were 11.77 kJ/mol and 1.45 s-1 on the gas release characteristics, respectively

Analytical Multi-Scale Methodology for Fluidization Systems - Retrospect and Prospect

Understanding the spatio-temporal multi-scale structure of fluidization is a challenging problem. This presentation reviews our 20-year efforts on this subject, showing the roadmap that has gradually evolved from a simple idea to a systematic methodology inclusive of subsidiary, related systems and industrial applications. The strategy of establishing stability conditions through analyses of the compromise between dominant mechanisms is emphasized. The presentation concludes with prospects for further theoretical explorations and industrial applications

A few recent developments in fluidized bed technology applications for fuel conversion

In recent years, the process concepts based on two-stage and dual bed have been widely adopted in developing fuel conversion technologies including pyrolysis, combustion, gasification and catalytic cracking. These provide indeed advantages of, for example, easy operation and control, poly-generation of products, and high efficiency in elimination of undesirable product or pollutants. The so-called micro fluidized bed analyzer (MFBRA) has been newly developed to measure reaction rates at arbitrary temperatures, giving a great support to fundamental research and technology developments for fuel conversion. This report intends to summarize the involved new concepts, major fundamental understandings, pilot test and/or industrial demonstrations of a few newly developed fuel conversion technologies. Concretely, it will report fluidized bed two-stage gasification (FBTSG), dual fluidized bed pyrolysis combustion (DBPC), fluidized bed cracking gasification (FBCG) and MFBRA. The FBTSG technology separates fuel pyrolysis in a FB pyrolyzer and char gasification in a transport bed gasifier. The latter enables high-temperature tar cracking under catalysis of char to enable remarkably low tar content in the produced gas [1]. For fuel with high contents of water and nitrogen, the DBPC technology first removes fuel water and most fuel volatile in a pyrolyzer. This, on the one hand, ensures stable combustion of the fuel, and on the other hand facilitates NOx reduction by char and pyrolysis gas [2]. The FBCG technology separates the catalytic cracking of heavy feedstock for liquid and the gasification of char, the cokes formed on the catalyst surface, to produce syngas and also to regenerate the catalyst. By using micro fluidized bed, the MFBRA is newly developed to enable the on-line pulse feeding and rapid heating of particle reactant. It effectively suppresses the interfacial diffusion limitation and minimizes the intra-particle diffusion [3]. Thus, MFBRA provides isothermal reaction analysis in comparison with that in TGA based on programmed heating. REFERENCES 1. X. Zeng, et al. Pilot verification of a low-tar two-stage coal gasification process with a FB pyrolyzer and fixed bed gasifier. Applied Energy, 115, 9–16, 2014. 2. P. Dagaut, et al. Experiments and kinetic modeling study of NO-reburning by gases from biomass pyrolysis in a JSR. Energy & Fuels, 17(3), 608-613, 2003. 3. J. Yu, et al. Kinetics and mechanism of solid reactions in a micro fluidized bed reactor. AIChE Journal, 56, 2905-2912, 2010

Chem. Eng. J.

The minimum fluidization and minimum bubbling velocities of silica sand particles in air-blown micro beds of 120 mm high and with inner diameters of less than 32 mm were investigated to understand the wall effect in micro fluidized beds (MFBs) and the operability of the MFBs. Experimental results demonstrated that both the quoted velocities obviously increase with decreasing the inner diameter of the bed. A specific wall effect determined as the pressure drop per unit volume of particle bed in excess of the predicted pressure drop from the Ergun equation was proposed to quantitatively account for the influence of bed wall friction. By characterizing the fluidization qualities of differently sized particles in different MFBs, the article suggested further an optimal combination of bed diameter and particle size in the range of the static bed heights from 20 to 50 mm for the so-called micro fluidized bed (MFB) reactor devised to perform reaction(s) with minimal suffering from external gas mixing and gas diffusion. (c) 2007 Elsevier B.V. All fights reserved.The minimum fluidization and minimum bubbling velocities of silica sand particles in air-blown micro beds of 120 mm high and with inner diameters of less than 32 mm were investigated to understand the wall effect in micro fluidized beds (MFBs) and the operability of the MFBs. Experimental results demonstrated that both the quoted velocities obviously increase with decreasing the inner diameter of the bed. A specific wall effect determined as the pressure drop per unit volume of particle bed in excess of the predicted pressure drop from the Ergun equation was proposed to quantitatively account for the influence of bed wall friction. By characterizing the fluidization qualities of differently sized particles in different MFBs, the article suggested further an optimal combination of bed diameter and particle size in the range of the static bed heights from 20 to 50 mm for the so-called micro fluidized bed (MFB) reactor devised to perform reaction(s) with minimal suffering from external gas mixing and gas diffusion. (c) 2007 Elsevier B.V. All fights reserved

NO Reduction over Biomass Char in the Combustion Process

In the biomass combustion process, fuel N in biomass call be oxidized into NO(x), causing acid rain and photochemical smog. Some Measures should be taken to control NO(x) emissions from biomass combustion. In this paper, NO reduction over rice husk char in the combustion process was studied in it fixed-bed reactor to optimize the biomass combustion process. The results showed that biomass char was more active in the presence of oxygen to reduce NO than it was in the Inert atmosphere. With file increase of oxygen, more NO can be reduced by biomass char. From 973 to 1173 K, NO reduction over rice husk char increased with increasing temperature, Whereas the difference between NO reduction with and without oxygen decreased with increasing temperature. Moreover, the presence of CO and SO(2) in the combustion process was shown to enhance NO reduction over biomass char to different degrees. Therefore, it is in effective way to reduce NO from biomass combustion by emphasizing NO reduction over biomass char

Prediction of Core-Annulus Solids Mass Transfer Coefficient in Gas-Solid Fluidized Bed Risers

Based on analysis of energy dissipation in the core region of gas-solid fluidized bed risers, a simplified model for determination of core-annulus solids mass transfer coefficient was developed according to turbulent diffusion mechanism of particles. The simulation results are consistent with published experimental data. Core-annulus solids mass transfer coefficient decreases with increasing particle size, particle density and solids circulation rate, but generally increases with increasing superficial gas velocity and riser diameter. In the upper dilute region of gas-solid fluidized bed risers, core-annulus solids mass transfer coefficient was found to change little with the axial coordinate in the bed

Simultaneous production of CH4-rich syngas and high-quality tar from lignite by the coupling of noncatalytic/catalytic pyrolysis and gasification in a pressurized integrated fluidized bed

An integrated fluidized bed (IFB) reactor with a two-stage configuration has been developed to process small-size coal particles for the simultaneous production of CH4-rich syngas and high-quality tar, in which coal pyrolysis occurred in an upper transport bed (TB) within an atmosphere mixing steam and syngas generated by steam oxygen gasification of coal or char in a lower fluidized bed (FB). The coupling effect was investigated by combining non-catalytic/catalytic pyrolysis and gasification in a pressurized IFB. Having TB pyrolysis obviously raised CH4 yield (also its content in producer gas) and tar yield. The respective contributions to CH4 formation from the TB pyrolysis and FB gasification were mainly relevant to operating pressure and Ca(OH)(2) catalyst. Raising pressure facilitated CH4 formation. When lignite was treated without catalyst, the contribution from TB pyrolysis was greater than that from FB gasification as hydropyrolysis was intensified by pressure in H-2-rich gas atmosphere from the FB gasifier. Adding catalyst into lignite reversed their contributions. The FB catalytic gasification formed more CH4 because Ca(OH)(2) functioned well as a catalyst for CH4 formation in pressurized gasification. With elevated pressure or/and the addition of Ca(OH)(2), pyrolysis tar yield decreased in different degrees but its quality was improved. With the combination effect of pressure and Ca(OH)(2), producer gas from the tested IFB reactor was highly rich in CH4 to reach 10.8 vol%, with as well a high H-2/CO ratio of 2.3 that is suitable for making SNG. The obtained tar had its light tar content as high as 95 wt%.</p

Powder Technol.

A pyrolysis combustion technology (PCT) was developed for high-efficiency and environment-friendly chain grate boilers (CGBs). The realization of the PCF in a CGB requires that extremely large and widely sized coal particles should be first pyrolyzed in a semi-fluidized state before being transported into the combustion chamber of the boiler. This article was devoted first to investigating the fluidization of 0-40 mm coal particles in order to demonstrate the technical feasibility of the PCT. In succession, through mixing 0-10 mm and 10-20 mm coal particles in different proportions, multiple pseudo binary mixtures were prepared and then fluidized to clarify the effect of particle size distribution. With raw steam coal used as the feedstock, the superficial gas velocity of about 2.0 m/s may be suitable for stable operation of the fluidized-bed pyrolyzer in the CGB with the PCT. In the fluidization of widely sized coal particles, approximately half of the coal mass is segregated into the bottom section of the bed, though about 15% of 10-20 turn large particles are broken into 0-10 mm small particles because of particle attrition. The experimental results illustrate that an advanced CGB with the PCT has a high adaptability for various coals with different size distributions. (c) 2008 Elsevier B.V. All rights reserved.A pyrolysis combustion technology (PCT) was developed for high-efficiency and environment-friendly chain grate boilers (CGBs). The realization of the PCF in a CGB requires that extremely large and widely sized coal particles should be first pyrolyzed in a semi-fluidized state before being transported into the combustion chamber of the boiler. This article was devoted first to investigating the fluidization of 0-40 mm coal particles in order to demonstrate the technical feasibility of the PCT. In succession, through mixing 0-10 mm and 10-20 mm coal particles in different proportions, multiple pseudo binary mixtures were prepared and then fluidized to clarify the effect of particle size distribution. With raw steam coal used as the feedstock, the superficial gas velocity of about 2.0 m/s may be suitable for stable operation of the fluidized-bed pyrolyzer in the CGB with the PCT. In the fluidization of widely sized coal particles, approximately half of the coal mass is segregated into the bottom section of the bed, though about 15% of 10-20 turn large particles are broken into 0-10 mm small particles because of particle attrition. The experimental results illustrate that an advanced CGB with the PCT has a high adaptability for various coals with different size distributions. (c) 2008 Elsevier B.V. All rights reserved

Chem. Eng. Sci.

Effect of particle acceleration/deceleration on particle clustering behavior in dilute gas-solid flow was studied by experimental measurements and mathematical modeling. Calculation results of the model are in good agreement with experimental data from Phase Doppler Particle Analyzer (PDPA) measurements. The variation of voidage inside particle clusters is strongly dependent upon the change of the number of particles within the clusters. During acceleration, particle clusters are gradually disaggregated into smaller clusters with increasing voidage, while during deceleration, particle clusters are aggregated into larger clusters with decreasing voidage. (c) 2006 Elsevier Ltd. All rights reserved.Effect of particle acceleration/deceleration on particle clustering behavior in dilute gas-solid flow was studied by experimental measurements and mathematical modeling. Calculation results of the model are in good agreement with experimental data from Phase Doppler Particle Analyzer (PDPA) measurements. The variation of voidage inside particle clusters is strongly dependent upon the change of the number of particles within the clusters. During acceleration, particle clusters are gradually disaggregated into smaller clusters with increasing voidage, while during deceleration, particle clusters are aggregated into larger clusters with decreasing voidage. (c) 2006 Elsevier Ltd. All rights reserved