Process technologies for producing low-carbon olefins from heavy feedstocks in China
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This post was last edited by chengkang on 2009-10-19 at 12:24. Process technologies for producing low-carbon olefins from heavy feedstocks in China – (1) DCC process. In response to the generally low content of light oils in China’s crude oil, the Sinopec Petroleum Research Institute has developed the Deep Catalytic Cracking (DCC) technology, which enables the production of larger amounts of low-carbon olefins. The DCC process flow is similar to that of conventional FCC; the feedstock can be VGO, or it can be blended with deasphalted oil, coker wax oil, or residue. However, it differs significantly from FCC in terms of catalyst, process parameters, and degree of reaction. DCC-I uses a riser with a packed-bed reactor and operates under harsh conditions to produce more propylene. DCC-I uses a riser reactor with milder reaction conditions, which allows for higher yields of isobutylene and isopentene, while also enabling the production of propylene and high-quality gasoline. (2) CPP process. Based on DCC technology, the Institute of Petrology has developed the catalytic pyrolysis (CPP) process technology through improvements to process parameters, catalysts, and plant configuration; this technology has now been successfully tested on an industrial scale at the Daqing Refining and Chemical Co., Ltd. of CNPC. The CPP process is a process that combines catalytic reactions with thermal reactions. The newly developed catalyst possesses dual catalytic activities for cationic reactions and radical reactions; within the riser reactor, the feed materials undergo catalytic cracking, high-temperature pyrolysis, selective catalysis, olefin copolymerization, disproportionation, and aromatization – all of which enable the maximum production of ethylene and propylene. Reaction temperature (610–640°C) and reagent-to-oil ratio (15–21), including two operating modes: maximum propylene (CPP-P) and maximum ethylene (CPP-E). (3) HCC process. The patented technology for the direct cracking of heavy oil to produce ethylene (HCC), developed by Luoyang Petrochemical Engineering Company, was designed to address the issue of heavier feedstocks for ethylene production, and industrial application trials have been successfully carried out at Qiqihar Chemical Company in Heilongjiang. The HCC process employs a \"reaction-regeneration\" technology similar to that used in catalytic cracking. Under process conditions of high reaction temperatures (750–700°C), short contact times (0.2–1.05 s), and a high oil-to-catalyst ratio (15–25), a specialized catalyst with good activity, selectivity, and stability (LCM-5) is used to directly crack heavy oil to produce ethylene, along with propylene, butenes, and light aromatics (such as RX). Meanwhile, the resulting coke and some tar are utilized as an internal heat source. The most prominent advantage of the HCC process is its ability to directly crack various heavy hydrocarbons, including VGO, residue, as well as coking distillates and thermally cracked materials
The FDFCC-III process: The FDFCC-I1I process developed by Luoyang Petrochemical Engineering Company of Sinopec is based on the FDFCC-I process. It involves transferring the gasoline catalyst in the riser, which has a relatively low temperature and high residual activity, to the bottom of the heavy oil riser where it mixes with the regenerated catalyst. This increases the catalyst-to-oil ratio in the heavy oil riser, reduces the instantaneous contact temperature between oil and catalyst, enhances the catalytic reaction, suppresses thermal cracking reactions, and thus achieves the goals of reducing the production of dry gas and coke, increasing the yield of propylene, and improving the product distribution. In March 2006, a FDFCC III technological upgrade was carried out on the FDFCC-I unit at the Changling Branch of Sinopec Corporation. It came online on April 18, and two calibrations were conducted on May 17–18 and August 9–10. Under conditions that were essentially the same as those used in the FDFCC-I unit, namely with similar feed oil and catalysts, the product profile of the FDFCC-III process improved: the dry gas yield decreased, while the yields of liquefied petroleum gas and propylene increased. Meanwhile, the volume fraction of olefins in the gasoline produced by the FDFCC-II process can be less than 18%, which is 30 percentage points lower than that in FDFCC-I; at the same time, the sulfur content in the gasoline also decreases by 40% to 50%. The CGP technology RIPP has developed a CGP process based on the MIP of FCC processes that produce various heteroalkanes, one that enables gasoline components to meet Euro III emission standards while increasing propylene production. This process uses heavy oil as raw material and employs a novel reaction system consisting of series-connected lift tube reactors. The first reaction zone is primarily used for cracking reactions; within this zone, the degree of cracking of the feed oil increases in one step, thereby producing more gasoline rich in olefins and liquefied petroleum gas rich in propylene ； The second reaction zone is dominated by hydrogen transfer reactions and isomerization reactions, with moderate secondary cracking reactions. Under the combined action of secondary cracking and hydrogen transfer reactions, the olefins in gasoline are converted into propylene and isoparaffins. In April and July 2004, the CGP technology was applied to upgrade the 1.2 Mt/a RFCC unit of Sinopec Zhenhai Refining & Chemical Co., Ltd. and the 1.0 Mt/a RFCC unit of CNPC Jiujiang Branch, respectively. In October 2004 and April 2005, the Jiujiang Branch conducted two industrial calibrations of its CGP unit. The results of the industrial test calibration show that, when the properties of the feed oil deteriorate, the product distribution is slightly better than that of the original process; the conversion rate increases, the total liquid yield rises, while the yields of dry gas and slurry both decrease. The propylene yield increases by more than 3 percentage points, the volume fraction of olefins in gasoline decreases by 12–20 percentage points (with the lowest value reaching 13.4%), the sulfur content drops by 32.5%, and the RON increases by about 2 units. The PetroFCC technology: UOP’s PetroFCC process is based on the RxCat technology; it operates at high reaction temperatures and high oil-to-catalyst ratios, which increases the degree of cracking and boosts the production of propylene ； The second riser is used for the reprocessing of FCC gasoline to further increase propylene production ； Cracking gasoline into propylene using an additive with a high ZSM-5 content. The MxCat technology involves mixing a portion of the raw catalyst with the highly regenerated catalyst in an MxR mixing vessel located at the bottom of the riser, which allows for a reduction in the temperature at which the oil agents come into contact with each other and thus decreases thermal cracking. Its propylene + propane yield can be increased from 6% in conventional FCC processes to 21.5%. HS—FCC technology: The King Fahd University of Petroleum and Minerals in Saudi Arabia, Japan Oil Corporation, and Saudi Aramco jointly developed a highly aggressive FCC process for high-propylene yield—HS—FCC_l. This process operates at high reaction temperatures, short contact times, and a high catalyst-to-oil ratio, and utilizes a superstable Y catalyst, additives with high selectivity of molecular sieves, as well as a downward-flow reactor. The operation results of the demonstration unit show that when paraffin-based wax oil is used as the raw material along with conventional cracking catalysts, an propylene yield of 10.6% can be achieved ； When using hydrogenated wax oil as the feedstock along with a conventional cracking catalyst plus 10% ZSM-5 additive, the propylene yield can reach 20.4%. INDMAX technology: Indian Oil Corporation has developed the INDMAX technology for producing light olefins and high-octane gasoline from heavy oil. It employs fluidized reaction and regeneration techniques, operating at a reaction temperature of 550–580 °C, an oil-to-agent ratio of 15–25, a water injection rate of 15%–20%, and low reaction pressure. It uses oil cracking components from the bottom of the tower as raw materials, along with a three-component catalyst consisting of selective molecular sieves and ultra-stable Y molecular sieves. This technology has completed pilot tests as well as trials on a 0.1 Mt/a demonstration plant.
Process technologies for producing low-carbon olefins from heavy feedstocks abroad: The main technologies for producing olefins through the cracking of heavy oil abroad include the twin riser process developed by Exxon Mobil, the Petro FCC and LOCC processes developed by UOP, the SCC process developed by Lummus, and the NEXCC process developed by the Finnish company Mesteoy, among others. (1) Exxon Mobil twin riser process. The dual riser process is a patented technology developed by Exxon Mobil; the two riser reactors share one settler and one regenerator. The feed oil first enters the first riser reactor for reaction, and the gasoline fractions in the reaction products then go to the second riser reactor for further processing. The catalyst used contained both USY and ZSM-5 catalysts. This process technology can significantly increase the propylene yield; under appropriate conditions, the yields of ethylene and propylene via this process reach 2.7% and 12.1%, respectively, which are 2.25 times and 2.88 times higher than those obtained through conventional catalytic cracking under the same conditions. (2) Maxofintm process. A flexible FCC process jointly developed by Exxon Mobil and Kellogg Company is called Maxofin™. This process is similar to Exxon Mobil’s dual riser process: the first riser reactor cracks ordinary FCC feedstock, while the second riser feeds into the first one to produce cracked naphtha. Both risers share a single settler and regenerator. The catalyst used in this process is a conventional catalytic cracking catalyst to which 25% ZSM-5 catalyst has been added. Under conditions of maximum propylene production, the top temperatures of the first and second lift columns were 537°C and 593°C respectively, the oil-to-reagent ratios were 8.9 and 25 respectively, and the yields of ethylene and propylene were 4.50% and 18.37% respectively. (3) PetroFCC process. The PetroFCC process developed by UOP is also a configuration with two risers sharing one regenerator. The first riser operates under high-temperature and high oil-to-fuel ratios, using a catalyst with high cracking activity and low hydrogen transfer activity, along with additives containing a high concentration of shape-selective zeolites, to maximize the direct conversion of heavy feedstocks into light olefins or gasoline and light diesel fractions. To increase the olefin concentration, a low-pressure reaction zone is employed, along with a rapid separation system and an advanced feed distribution system, to control the short residence time of the oil-gas mixture in the riser, thereby reducing the formation of hydrogen and light saturated compounds. The second lift column operates under more severe conditions than the first lift column, further cracking some of the naphtha fractions produced by the first lift column into lighter components to facilitate the production of low-carbon olefins. The feedstock for this process can be distillate oil or vacuum residue; the propylene yield can reach 22.8%, while the C4 yield can reach 15.6%. The gasoline fraction can be further processed in an aromatic unit to produce over 50% p-xylene and 15% benzene. The PetroFCC technology increases propylene production by modifying the design of FCC units, integrating refining and chemical processes in a cohesive manner, which can significantly enhance a company’s economic efficiency. (4) Light olefin catalytic cracking {LOCC} technology. Light olefin catalytic cracking (LOCC) is a catalytic cracking technology developed by UOP for the production of low-carbon olefins. This technology utilizes a dual lift tube reactor and two reaction zones: the first lift tube carries out the primary cracking of the feed oil, while the second lift tube performs the secondary cracking of gasoline. At the bottom of the first lift pipe, there is an MxR mixing tank in which a portion of the raw catalyst is circulated and mixed with the high-temperature regenerated catalyst, thereby reducing the temperature at which the oil agents come into contact and minimizing thermal cracking. This technology uses an additive with a high ZSM-5 content. (5) Selective Compartmentalized Cell Differentiation (SCC) process. The Selective Chromatographic Crystallization (SCC) process is a technology developed by Lummus Company to maximize the production of propylene. The SCC process consists of the combination of the following technologies: (a) highly severe catalytic cracking operations; (b) optimized process conditions and selective fractionation using catalysts; (c) gasoline reprocessing; (d) ethylene and butylene isomerization to produce propylene. Among them, the high-severity catalytic cracking reaction system consists of a short-contact-time riser and a directly-connected cyclone separator, enabling the propylene yield to be increased from the traditional 3%-4% to 6%-7%. Selective group dissociation is achieved by optimizing process operating conditions and catalyst formulations. By using an FCC catalyst with a high ZSM-5 content and operating under high temperatures and high oil-to-catalyst ratios, the propylene yield can be increased to 16%-17%. Reprocessing of gasoline components can further raise the propylene yield by 2-3 percentage points, while the transposition reaction of ethylene and butylene into propylene in a fixed-bed reactor is expected to enable an additional 9-12 percentage points increase in propylene production. Therefore, the combination of these 4 technologies can yield 25%-30% propylene. However, there have been no reports to date of this technology being industrialized. (6) NEXCC process. NEXCC is a catalytic cracking process for producing gaseous olefins, developed by the Finnish company Mesteoy. It features two circulating fluidized bed units arranged coaxially, with the outer unit serving as a regenerator and the inner unit acting as a reactor; moreover, multi-entry cyclone separators are used in place of conventional FCC cyclone separators. NEXCC operates under severe conditions; its typical reaction temperature is 600–650°C, the catalyst circulation rate is 2–3 times that of the FCC process, and the contact time between the oil and the catalyst is 1–2 seconds. The size of the NEXCC unit is only 1/3 that of a FCC of the same scale, thus construction costs can be reduced by 40%-50%.
It’s quite comprehensive, but this PetroFCC and LOCC are very similar to the TSRFCC developed by the Petroleum University. 14 years have passed since its introduction, and TSRFCC has been industrialized in 10 units. In terms of producing large amounts of low-carbon olefins, increasing liquid yield, and generating more diesel, it is in no way inferior to foreign technologies. Among domestic FCC industrialization technologies, it is the technology with the most industrial plants. It possesses independent intellectual property rights.