Institutional Repository of GuangZhou Institute of Energy Conversion, CAS
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Heating performance and optimization of ice source heat pump system with supercooled water
No full textAn ice source heat pump, which can extract latent heat from the icy water, has a better system performance in low-temperature areas. Cosiderring the disadvantange of ice source heat pump using static ice-making method or scraping ice-making method, an ice source heat pump based on supercooled water method is proposed and its heating performance is measured in the study. Then, a system model is developed to study and optimize the system performance. It concludes: (1) The ice source heat pump system COP decreases with the increasing supercooled water flow rate. The system COP reaches about 3.3 when the condensation temperature is 42 degrees C. (2) The proper range of supercooled degrees in ice source heat pump is mainly from 2 degrees C to 3 degrees C. (3) The rank of local exergy loss rate in ice source heat pump system is listed as follows: compressor > condenser > valve > evaporator > pump. The exergy loss proportion of compressor and condenser is about 65%. (4) The system COP and exergy efficiency of ice source heat pump increase approximately linearly with the increase of capacity. The optimal supercooled degree mainly depends on the rate of change of the compressor power and the pump power concerning the supercooled degree. This work provides insight into the performance of ice source heat pump with supercooled method and guides the design of ice source heat pump system
Chemical recycling of plastic wastes via homogeneous catalysis: A review
No full textImproper disposal of plastic wastes causes serious negative impacts on the ecosystem. These plastic wastes are considered to be a rich carbon resource, and the use of homogeneous catalytic chemical recycling methods has enabled the high-value recovery of plastic wastes under mild conditions to obtain liquid fuels (alkane, cycloalkane and aromatic hydrocarbon etc.), high-value chemicals (terephthalic acid, bisphenol A and diols), and plastic monomers (bis(hydroxyalkyl) terephthalate). This review summarizes recent advances in homogeneous catalysis of plastic polymers for the preparation of high-value chemicals. The bond breaking mechanism of plastics using different homogeneous catalysts and the relationship between catalyst active sites and catalytic performance are systematically discussed in each section. Finally, we evaluate the current homogeneous catalytic chemical recycling routes for plastic wastes. Chemical recycling through homogeneous catalysis is a bright way to realize the circular economy of plastic wastes
A novelty catalytic reforming of tire pyrolysis oil for hydrogen-rich syngas
No full textPyrolysis oil and pyrolysis char from waste tires have been reported with poor quality but could be a source and catalyst for generating hydrogen-rich syngas, respectively. In this study, the influence of two-layer catalysts on the catalytic reforming syngas distribution derived from side wall rubber pyrolysis oil (SWRPO) was explored. The side wall rubber pyrolysis char (SWRC), as a catalyst and carrier support of nickel, was used as the first-layer catalyst, and the calcined bottom ash (CBA) from oil sludge combustion was used as the secondary catalyst. Steam was used as an activator to activate SWRC and improve the concentration of CO and H-2 in catalytic reforming syngas. Different analysis methods (BET, XRD, SEM, and Raman) were employed to characterize the properties of catalysts. Consequently, the yield and LHV of syngas increased from 0.05 g.(-1)(goil) and 2.03 kJ.g(-1) to 0.42 g.g(oil)(-1) and 11.32 kJ.g(-1), respectively. The H-2 concentration increased from 20.38 vol% to 44.68 vol% in syngas with two-layer catalysts, and the H-2 selectivity reached 0.16. The yield of carbon deposit increased to 0.57 g.g(oil)(-1) with the SWRPO total conversion of 95.55 %. The lifetime of two-layer catalysts reached 17 h with a stability conversion process of SWRPO
Systematic construction of combustion reaction model for large hydrocarbon fuels based on a two-step reaction scheme
No full textUnderstanding the combustion chemistry of large hydrocarbons in practical gasoline, diesel and jet fuels is critical for the reduction of pollutant emissions and increase of fuel and engine efficiencies. The primary objective of the present study is to illustrate the methodology and application of a simplified modeling approach based on a two-step reaction scheme (TSRS) for describing the combustion chemistry of large hydrocarbon fuels under engine-relevant high-temperature conditions. Under such conditions, the combustion process of large hydrocarbons consists of two distinct subsequent reaction steps: the first step is the prompt fuel decomposition, converting the parent fuel to critical intermediate products; the second step is the oxidation reactions of the intermediates. Particularly, the second step is slower, thus rate-limiting, controlling the heat release and formation of final combustion products of the entire combustion reaction process. A systematic analysis by mathematical methods was performed to obtain a unified treatment for hydrocarbons with different molecular sizes. Based on the analysis of characteristic time scale of elementary reaction and steady-state assumption, TSRS used a fuel decomposition submodel to describe the fuel molecule decompose into critical intermediate species, including ethene, propene, butenes and methane for n-alkanes, and used a detailed foundational fuel chemistry mechanism to describe the oxidation reaction of the intermediates. The entire TSRS reaction model for large hydrocarbons is compact, consisting -110 species and -800 reactions, which can be further reduced. It was shown in the present study that, by revealing the relationship between the functional group composition of linear alkanes and the distribution of intermediates, and in combination with the rate criterion, the fuel decomposition submodel can be systematically generated to facilitate the automatic construction of compact kinetic models. One unified TSRS combustion reaction model was created and demonstrated for several large hydrocarbons ranging from C8 to C16, which was validated by comprehensive datasets, including speciation, ignition delay times and laminar flame speeds
Thermo-/photo-catalysts for aerobic oxidative cyanation of diverse oxygen-containing feedstocks
No full textNitriles constitute essential components in a vast array of both bulk and fine chemicals, as well as in various bioactive molecules. The aerobic oxidative cyanation of diverse oxygen-containing feedstocks, including alcohols, aldehydes, and ketones, stands out as a green and highly promising avenue for nitrile synthesis over both thermocatalysts and photocatalysts. In this review, we initially elucidate the reaction mechanisms involved in the oxidative cyanation of oxygen-containing compounds. Following this, we present a summary and commentary on the predominantly achieved progress in the oxidative cyanation of various oxygen-containing feedstocks over the last decade. The categorization is based on types of catalysts, including non-noble metal catalysts, single-metal-atom catalysts, metal-free catalysts, and photocatalysts. Additionally, we assess the current catalytic systems from the standpoint of green chemistry. Finally, we conclude by highlighting the current challenges and delineating our prospects for future research endeavors.
Aerobic oxidative cyanation of diverse oxygen-containing compounds over thermo- and photocatalysts is highlighted as a green and promising avenue for nitrile synthesis
Dynamic Effect of Drilling Fluid Filtrate Reducers on Hydrate Formation
No full textHydrate formation and decomposition are major challenges in marine hydrate development drilling. Filtrate reducers are important additives in water-based drilling fluids that reduce methane hydrate formation. However, research on the influence of commonly used filtrate reducers in drilling fluids on hydrate formation is limited. Here, we investigated the effects of three filtrate reducers, humic acid potassium (KHm), hydroxypropyl starch (HPS), and hydrolyzed polyacrylonitrile sodium salt (Na-HPAN), on methane hydrate formation kinetics and those of different concentrations under an initial pressure of 6 MPa and different initial pressures (6, 8, 10, and 12 MPa) in the same concentration system. The KHm solution (1-3%) promoted hydrate formation at 4 degrees C and 6 MPa, the Na-HPAN solution (0.3-1.5%) inhibited hydrate formation, and the HPS solution (0.1-1.5%) inhibited hydrate formation in the first 10 h of reaction but promoted a large amount of hydrate formation after the inhibition failure. At 4 degrees C, higher initial pressures led to earlier and faster formation of CH4 hydrate in large quantities in the filtrate reducer solution. An extreme gas hydrate conversion value was observed, indicating that the initial pressure is crucial when using a filtrate reducer. These observations provide a crucial basis for flow assurance and water-based drilling fluid design
Effect of different organic loads on the performance and microbial community mechanism of dry anaerobic digestion
No full textIn this study, the vertical continuous push-flow dry anaerobic digestion (AD) reactor was developed independently. Typical agricultural organic waste straw and cow dung were used as raw materials in this paper to carry out long-term continuous mixed dry AD experiments on a controlled laboratory scale. The experimental results showed that the system was in low-stress operation at an organic load rate (OLR) of 3 g VS L-1 d(-1), the VS methane production rate was located at 225 similar to 272 mL CH4 g VS-1, and the volumetric methane production rate was located at 0.95 +/- 0.08 L (Ld)(-1), and the combination of the volumetric methane production rate, VS methane production rate, methane content of the gas, and the VS removal rate showed that the system's operational performance in this stage was in the best condition in the whole set of experiments. When the OLR reached 25 g VS L-1 d(-1), the content of VFAs all began to climb rapidly above 8000 mg/L, with the content of acetic acid increasing most significantly due to the fact that the activity of acetic acid-type methanogenic bacteria was the first to be inhibited. Eventually, because of the kinetic differences between the hydrolytic acidifying bacteria and the methanogenic archaea, the final acidification destabilisation of the anaerobic digestion reactor occurred and the system was irreversibly destabilised. The system performance at this stage was in the best condition in the whole set of experiments. The study of microbial community succession and metabolic mechanisms showed that Methanoculleus and Methanobacterium play a key role in sustaining methane production, and the increased abundance and dominance of hydrogen methanogens implies that methane is produced via the hydrogen methanogenic pathway under high organic loading conditions
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