Progress in the CO2 Capture Technologies for Fluid Catalytic Cracking (FCC) Units—A Review

© Copyright © 2020 Güleç, Meredith and Snape. Heavy industries including cement, iron and steel, oil refining, and petrochemicals are collectively responsible for about 22% of global CO2 emissions. Among these industries, oil refineries account for 4–6%, of which typically 25–35% arise from the regenerators in Fluid Catalytic Cracking (FCC) units. This article reviews the progress in applying CO2 capture technologies to FCC units. Post combustion and oxyfuel combustion have been investigated to mitigate CO2 emissions in FCC and, more recently, Chemical Looping Combustion (CLC) has received attention. Post combustion capture can readily be deployed to the flue gas in FCC units and oxyfuel combustion, which requires air separation has been investigated in a pilot-scale unit by Petrobras (Brazil). However, in comparison, CLC offers considerably lower energy penalties. The applicability of CLC for FCC has also been experimentally investigated at a lab-scale. As a result, the studies demonstrated highly promising CO2 capture capacities for FCC with the application of post combustion (85–90%), oxyfuel combustion (90–100%) and CLC (90–96%). Therefore, the method having lowest energy penalty and CO2 avoided cost is highly important for the next generation of FCC units to optimize CO2 capture. The energy penalty was calculated as 3.1–4.2 GJ/t CO2 with an avoiding cost of 75–110 €/t CO2 for the application of post combustion capture to FCC. However, the application of oxyfuel combustion provided lower energy penalty of 1.8–2.5 GJ/t CO2, and lower CO2 avoided cost of 55–85 €/t CO2. More recently, lab-scale experiments demonstrated that the application of CLC to FCC demonstrate significant progress with an indicative much lower energy penalty of ca. 0.2 GJ/t CO2

The impact of hydrothermal carbonisation on the char reactivity of biomass

Hydrothermal carbonisation (HTC) is an attractive biomass pre-treatment as it produces a coal-like fuel, can easily process wet biomass and wastes, and lowers the risk of slagging and fouling in pulverised fuel (PF) combustion boilers. One of the major factors in determining the suitability of a fuel as a coal replacement for PF combustion is matching the char reactivity and volatile matter content to that of coals, as these significantly affect heat release and flame stability. The char reactivity of wood and olive cake biocoals and their respective drop tube furnace chars have been studied using thermogravimetric analysis in comparison to other biomass fuels and high-volatile bituminous coal. It was found that HTC reduces the reactivity of biomass, and in the case of HTC of wood pellets the resulting biocoal has a char reactivity similar to that of high-volatile bituminous coal. Proximate analysis, X-ray fluorescence analysis, and textural characterisation were used to show that this effect is caused primarily by removal of catalytic alkali and alkaline earth metals. Subsequent torrefaction of the wood biocoals was performed to tailor their volatile matter content to match that of sub-bituminous and high volatile bituminous coals without major impact on char reactivity

Impact of solvent type and condition on biomass liquefaction to produce heavy oils in high yield with low oxygen contents

Bio-oils produced by processes such as slow or fast pyrolysis typically contain high water and oxygen contents, which make them incompatible with conventional fuels. It is therefore necessary to upgrade the bio-oils to reduce their oxygen and water contents. The bio-oil upgrading process can consume up to 84 wt% of the initial bio-oil it is therefore important to develop other alternative approaches to generate high quality bio-oil. Thermolytic liquid solvent extraction (LSE) has been considered as a potential viable process due to the high liquid yield, better product quality and water free nature of the final products. In this study, a novel LSE process of biomass liquefaction has been studied under various conditions of solvent type, temperature, and biomass species. Compared to currently available commercial pyrolysis approaches, this process using tetralin as a solvent is shown to be capable of generating high quality bio-oil with low oxygen contents (ca. 5.9%) at extremely high overall conversions of up to 87 and 92 (%) dry and ash free basis (DAF) from Scotch pine and miscanthus, respectively. Overall, the study has demonstrated the advantages of LSE for bio-oil generation from biomass, in terms of producing high conversions to liquid products that are compatible with existing petroleum heavy feedstocks

A novel approach to CO2 capture in Fluid Catalytic Cracking-Chemical Looping Combustion

Oil refineries collectively account for about 4–6% of global CO2 emissions and Fluid Catalytic Cracking (FCC) units are responsible for roughly 25% of these. Although post-combustion and oxy-combustion have been suggested to capture CO2 released from the regenerator of FCC units, Chemical Looping Combustion (CLC) is also a potential approach. In this study, the applicability of CLC for FCC units has been explored. A refinery FCC catalyst (equilibrium catalyst-ECat) was mixed mechanically with reduced oxygen carriers; Cu, Cu2O, CoO, and Mn3O4. To identify any detrimental effects of the reduced oxygen carriers on cracking, the catalyst formulations were tested for n-hexadecane cracking using ASTM D3907-13, the standard FCC microactivity test (MAT). To investigate the combustion reactivity of coke with physically mixed oxidised oxygen carriers, CuO, Co3O4 and Mn2O3, TGA tests were conducted on a low volatile semi-anthracite Welsh coal, which has a similar elemental composition to actual FCC coke, with various oxygen carrier to coke ratios over the temperature range 750–900 °C.The results demonstrated that, whereas Cu was detrimental for cracking n-hexadecane with the ECat, Cu2O, CoO, and Mn3O4 have no significant effects on gas, liquid and coke yields, and product selectivity. Complete combustion of the model coke was achieved with CuO, Co3O4 and Mn2O3, once the stoichiometric ratio of oxygen carrier/coke was higher than 1.0 and sufficient time had been provided. These results indicate that the proposed CLC-FCC concept has promise as a new approach to CO2 capture in FCC

Selective low temperature chemical looping combustion of higher alkanes with Cu- and Mn- oxides

Chemical looping combustion (CLC) of n-hexadecane and n-heptane with copper and manganese oxides (CuO and Mn2O3) has been investigated in a fixed bed reactor to reveal the extent to which low temperature CLC can potentially be applicable to hydrocarbons. The effects of fuel to oxygen carrier ratio, fuel feed flow rate, and fuel residence time on the extent of combustion are reported. Methane did not combust, while near complete conversion was achieved for both n-hexadecane and n-heptane with excess oxygen carrier for CuO. For Mn2O3, complete reduction to Mn3O4 occurred, but the extent of combustion was controlled by the much slower reduction to MnO. Although the extent of cracking is relatively small in the absence of cracking catalysts, for the mechanism to be selective for higher hydrocarbons suggests that the reaction with oxygen involves radicals or carbocations arising from bond scission. Sintering of pure CuO occurred after repeated cycles, but this can easily be avoided using a support, such as alumina. The fact that higher hydrocarbons can be combusted selectively at 500 °C and below, offers the possibility of using CLC to remove these hydrocarbons and potentially other organics from hot gas streams

Retardation of oil cracking to gas and pressure induced combination reactions to account for viscous oil in deep petroleum basins: evidence from oil and n-hexadecane pyrolysis at water pressures up to 900bar

This study reports a laboratory pyrolysis experimental study on oil and n-hexadecane to rationalise the thermal stability of oil in deep petroleum reservoirs. Using a 25 ml Hastelloy pressure vessel, a 35° API North Sea oil (Oseberg) and n-hexadecane (n-C16), were pyrolysed separately under non-hydrous (20 bar), low pressure hydrous (175 bar) and high liquid water pressure (500 and 900 bar) at 350°C for 24 h. This study reports a laboratory pyrolysis experimental study on oil and n-hexadecane to rationalise the thermal stability of oil in deep petroleum reservoirs. Using a 25 ml Hastelloy pressure vessel, a 35° API North Sea oil (Oseberg) and n-hexadecane (n-C16), were pyrolysed separately under non-hydrous (20 bar), low pressure hydrous (175 bar) and high liquid water pressure (500 and 900 bar) at 350 °C for 24 h. This study shows that the initial cracking of oil and n-hexadecane to hydrocarbon gases was retarded in the presence of water (175 bar hydrous conditions) compared to low pressures in the absence of water (non-hydrous conditions). At 900 bar water pressure, the retardation of oil and n-hexadecane cracking was more significant compared to 175 bar hydrous and 500 bar water pressure conditions. Combination reactions have been observed for the first time in pressurised water experiments during the initial stages of cracking, resulting in the increased abundance of heavier n-alkane hydrocarbons (> C20), the amount of unresolved complex material (UCM), as well as the asphaltene content of the oil. These reactions, favoured by increasing water pressure provide a new mechanism for rationalising the thermal stability of oils, and for producing heavy oils at temperatures above which biodegradation can occur. Indeed, we demonstrate that bitumen from the high pressure Gulf of Mexico basin has been formed from lighter oil components and it possesses similar characteristics to the laboratory oils generated

Should IQOS Emissions Be Considered as Smoke and Harmful to Health? A Review of the Chemical Evidence

The chemical evidence that IQOS emissions fit the definition of both an aerosol and smoke, and that IQOS and potentially other heated tobacco products (HTPs) pose some harmful health threats from the range of compounds released even at somewhat lower concentrations is reviewed. Further, we address the yields of harmful and potentially harmful compounds (HPHCs), including polycyclic aromatic hydrocarbons (PAHs), and the constituents of IQOS emission that are diagnostic of pyrolysis to provide information on the temperatures reached in IQOS tobacco sticks. The HPHCs present in IQOS emissions are the same as in conventional cigarette smoke (CCs), analogous to emissions from earlier generation of HTPs classed as smoke. However, Philip Morris International (PMI) studies have to some degree underestimated IQOS aerosol HPHC yields, which are a factor of between 3.2 and 3.6 higher when expressed on a tobacco rather than an IQOS stick basis compared to the reference 3R4F cigarette. Further, IQOS emissions contain carbon particles, which fit definition of both aerosol and smoke. Continual reheating of deposited tar in the IQOS device will occur with real-life use, likely leading to generation of even higher concentrations of HPHCs and particulate matter. Despite IQOS not exceeding 350 °C, local hot spots could exist, causing formation of species (phenol/cresols, PAHs). It is recommended that the impact of repeated use to determine the levels of black carbon (insoluble organic matter) in the particulate matter, and the extent to which compounds in IQOS emissions are formed by pyrolysis need to be assessed rigorously. To address whether uneven temperature profiles in heat sticks can lead to potential hot spots that could, for example, lead to PAH formation, it is recommended that pyrolysis studies on tobacco and other constituents of HTPs are required in conjunction with more effort on heating tobacco blends under controlled temperature/time conditions

Analysis of conjugated steroid androgens: Deconjugation, derivatisation and associated issues

AbstractGas chromatography/mass spectrometry (GC/MS) is the preferred technique for the detection of urinary steroid androgens for drug testing in athletics. Excreted in either the glucuronide or sulfated conjugated form, steroids must first undergo deconjugation followed by derivatisation to render them suitable for GC analysis. Discussed herein are the deconjugation and the derivatisation preparative options. The analytical challenges surrounding these preparatory approaches, in particular the inability to cleave the sulfate moiety have led to a focus on testing protocols that reply on glucuronide conjugates. Other approaches which alleviate the need for deconjugation and derivatisation are also highlighted

Cyclic performance evaluation of a polyethylenimine/silica adsorbent with steam regeneration using simulated NGCC flue gas and actual flue gas of a gas-fired boiler in a bubbling fluidized bed reactor

To accelerate the deployment of Carbon Capture and Storage (CCS) based on the solid amine adsorbents towards a practical scale application relevant to Natural Gas Combined Cycle (NGCC) power plants, this study has evaluated the cyclic performance of a polyethylenimine/silica adsorbent of kg scale in a laboratory scale bubbling fluidized bed reactor. A high volumetric concentration 80?90 vol% of steam mixed with N2 and CO2 has been used as the stripping gas during a typical temperature swing adsorption (TSA) cycle. Both the simulated NGCC flue gas and the actual flue gas from a domestic gas boiler have been used as the feed gas of the CO2 capture tests with the solid adsorbent. Various characterization has been carried out to elucidate the possible reasons for the initial capacity decline under the steam regeneration conditions. The effect of presence of CO2 in the stripping gas has also been studied by comparing the working capacities using different regeneration strategies. It has been demonstrated that the breakthrough and equilibrium CO2 adsorption capacities can be stabilized at approximately 5.9 wt% and 8.6 wt%, respectively, using steam regeneration for both the simulated and actual natural gas boiler flue gases. However, using a concentration of 15 vol% CO2 in the stripping gas has resulted in a significantly low working capacity at a level of 1.5 wt%, most likely due to the incomplete C

Biomedical and Forensic Applications of Combined Catalytic Hydrogenation-Stable Isotope Ratio Analysis

Studies of biological molecules such as fatty acids and the steroid hormones have the potential to benefit enormously from stable carbon isotope ratio measurements of individual molecules. In their natural form, however, the body’s molecules interact too readily with laboratory equipment designed to separate them for accurate measurements to be made. Some methods overcome this problem by adding carbon to the target molecule, but this can irreversibly overprint the carbon source ‘signal’. Hydropyrolysis is a newly-applied catalytic technique that delicately strips molecules of their functional groups but retains their carbon skeletons and stereochemistries intact, allowing precise determination of the carbon source. By solving analytical problems, the new technique is increasing the ability of scientists to pinpoint molecular indicators of disease, elucidate metabolic pathways and recognise administered substances in forensic investigations