大型燃气乙烯裂解炉燃烧过程的优化模拟

采用CFD-FLUENT软件建立了乙烯裂解炉炉膛模型,并按照裂解炉实际运行工况,将内燃机清洁燃烧概念,即富氧和烟气再循环引入到炉膛燃烧计算中,计算不同富氧率下燃料气体的放热量和不同烟气再循环率下NO_x的分布。结果表明,使用烟气再循环可以有效降低NO_x排放,但对燃料燃烧温度以及燃料燃尽率有影响,而利用富氧燃烧可以提高炉内燃料的燃烧放热量,但却增加NO_x排放,而使得锅炉排放恶化;采用适宜的富氧率和烟气再循环率,可以达到节能减排的目的。     

浸没燃烧天然气加热装置燃烧室设计优化

浸没燃烧天然气加热装置是一种新型天然气加热装置,通过理论分析计算与数值模拟实验研究的方法,并结合实际装置运行情况,对装置燃烧室进行优化设计,给出该类型燃烧室设计结构及运行工况的优化参数。结果表明:①综合考虑过剩空气系数对NO_x、CO排放以及烟气出口温度的影响,过剩空气系数建议取1.4;②在浸没式燃烧-圆筒形金属纤维燃烧器的燃烧室设计中,建议烟气流动空间设计流速取值不高于5 m/s。      

Effects of hydrogen enrichment on diesel engine fueled with Afzelia Africana biodiesel – TiO2 blends

Owing to strict emission-policies, vehicle manufacturers are mandated to control hazardous emissions from diesel engines. One novel step adopted in this work, is the use of hydrogen enrichment with nanofuel, where TiO₂ nanoparticles- Afzelia Africana biodiesel-mix was blended with hydrogen for use in a diesel engine. 25 ppm TiO₂ nanoparticles were admixed with biodiesel and ultrasonicated. Thereafter, H₂ was introduced through the air inlet at the lowest possible flow rate (3–4 LPM) to avoid reaching H₂/air explosion limit. The ratio of H₂ to the blended fuels (BNH) is (15: 85 vol/vol %). The effects of the nanofuels blended with pure H₂ were investigated by evaluating the brake thermal efficiency (BTE), wall temperature of the combustion chamber, NO_x, CO, and HC emissions. Via a simplified model, the associated uncertainties in the parametric variations were determined while a Supervisory Computer Aided Data Acquisition (SCADA) system with an in-built program, was configured in the engine set-up for data generation. The results showed that higher BTE of the blends + 25 ppm TiO₂ alongside hydrogen flowrates of 3 LPM and 4 LPM helped to improve the engine performance with lesser emissions of CO, NO_x and HC respectively. Sample BNH@-3-LPM gave the best performance/BTE of 39.5 % compared to BNH@-4-LPM (32.4 %), BN (29 %) and diesel (29.4 %), whereas, BNH@-3-LPM gave the lowest emissions of 0.4, 5 and 81 g/kwh for CO, HC and NO_x respectively compared with diesel which gave corresponding emissions of 0.8, 35 and 200 g/kwh for CO, HC and NO_x respectively.     

Hydrogen production by catalytic gasification of petroleum residue

The liquid fuel gasification to obtain a clean flue gas for power generation and produce chemicals such as methanol is a most promising attempt to reduce the greenhouse gas emissions and air pollutants. In this paper, an equilibrium model of liquid fuel gasification was developed by the method of Gibbs free energy minimization. Two kinds of catalysts: Ni/CeO₂/Al₂O₃ and Ni/Al₂O₃ were used to explore the influence of catalysts and operating conditions on hydrogen yield and char conversion. Over the ranges of operating conditions studied, the maximum hydrogen yield reached 52.47 vol%, whereas the char conversion varied between 45.2% and 98.5%. The results indicated that an appropriate reaction temperature is favorable for higher hydrogen production and char conversion. The model was validated with experimental data obtained from a fluidized bed gasifier.     

Experimental Investigation of the Effect of Using Ethanol-Blended Diesel Fuels on Engine Performance and Exhaust Emissions

Abstract

In this experimental work, the variations of cylinder pressure and exhaust emissions using ethanol–diesel fuel mixtures with different blends and compression ratios in a diesel engine are reported. Experiments are carried out using an ASTM-CFR monocylinder test engine, operated at constant engine speed and without loading. Comparison of the results with standard Eurodiesel fuel combustion experiments indicate that NO_x, soot, and CO emissions decrease, whereas CO₂ emissions increase with increaseed ethanol concentration. An increase in the compression ratio results in a decrease in NO_x and CO₂ emissions and an increase in CO and soot emissions.     

H2S废气反应炉燃烧数值模拟

针对某炼油化工厂H_2S反应炉设计的不同结构的燃烧器进行三维数值模拟,研究了不同燃烧器结构参数、燃料气成分与分配比例、反应炉花墙结构等因素对炉内流动与燃烧的影响,并确定了合理的燃烧器结构。结果表明:原始燃烧器结构下,单烧酸性气工况时,降低内圈酸性气比例有利于H_2S的完全燃烧,炉膛出口烟温有所提高;优化后的燃烧器结构较原始结构下,增强了内圈酸性气与空气的混合,更有利于H_2S气体的燃烧;反应炉内花墙结构能造成炉膛内烟气回流,提高了烟气的停留时间,有利于H_2S气体的燃烧完全;掺烧天然气工况较单烧酸性气工况,炉内燃烧变差。     

塔一联含氮天然气对加热炉燃烧的影响

为解决塔河油田注氮开采导致天然气含氮量上升而造成的天然气燃烧炉燃烧过程不稳定的问题,基于数值模拟软件Fluent,对塔一联含氮天然气在加热炉锥形燃烧室中温度场的分布规律及燃烧产物NOx的生成规律进行了研究,并针对塔一联含氮天然气组分的特殊性,分别以燃烧效率、NOx浓度、引燃温度、发热量及沃泊指数为基准,对掺混方案进行计算,并对4种掺混方案进行对比分析。确定选用基于NOx浓度的含氮天然气掺混方案,可保证塔一联含氮天然气燃烧过程燃烧效率、引燃温度、发热量及沃泊指数要求的同时,有效减少氮氧化合物带来的环境污染,具有较强的实际意义。     

加氢进料燃烧炉运行优化研究

为了解决加氢进料燃烧炉排气温度偏高的问题,通过建立数据模拟模型,分析了加氢进料燃烧炉入口燃料气流量、空气流量、低压蒸汽流量、上游尾气流量等因素对加氢进料燃烧炉出口温度、H_2摩尔分数以及炉内流场的影响,得出最佳工艺优化方案。并通过现场应用得出,加氢进料燃烧炉出口温度明显降低,燃料气用量也有所降低。在解决加氢进料燃烧炉出口温度偏高的同时,实现了节能降耗的目的,为国内同类加氢进料燃烧炉的研究提供了借鉴。     

Effect of waste cooking-oil biodiesel on performance and exhaust emissions of a diesel engine

The ever increase in global energy demand, consumption of depletable fossil fuels, exhaust emissions and global warming, all these led to search about alternative fuels. Biodiesel was produced from waste cooking-oil by transesterification process. Blends of waste cooking-oil biodiesel and diesel oil were prepared in volume percentages of 10, 20 and 30% as B10, B20 and B30. Biodiesel blends have ASTM standards of physical and chemical characterization near to diesel fuel. Diesel engine performance and exhaust emissions were studied experimentally for burning waste cooking-oil blend with diesel fuel. This experimental was applied on a diesel engine at different engine loads from zero to full load. Thermal efficiencies for waste cooking-oil biodiesel blends were lower than diesel oil. Specific fuel consumptions of biodieselblends were higher than diesel fuel. Higher exhaust gas temperatures were recorded for biodiesel blends compared to diesel oil. CO₂ emissions for waste cooking-oil biodiesel blends were higher than diesel oil. CO, smoke opacity and HC emissions for biodiesel blends were lower than diesel fuel. NO_x emissions for biodiesel blends were higher than diesel fuel.     

Influence of an oxygenated additive on emission of an engine fueled with neat biodiesel

Biodiesel obtained from mustard seed is found to be a promising alternative for petroleum diesel fuel owing to its similarity in physical and chemical properties. In this work, TiO₂ nano-fluid which acts as an oxygen buffer during combustion was added to mustard oil biodiesel (MOBD) to study its effect on emission characteristics of MOBD. TiO₂ nano-fluid can provide high surface energy during the course of combustion and reduces the limitations of neat biodiesel. A four-stroke, multi-cylinder, water-cooled, diesel engine was used in the experiments and was fueled with diesel, neat MOBD and MOBD with TiO₂ nanoparticles at 100 ppm (MOBDT100), 200 ppm (MOBDT200) and 300 ppm (MOBDT300). Experimental results revealed that the TiO₂ nanoparticles had positive effect on the emission characteristics of MOBD as it acted as an oxidation buffer. MOBDT300 showed a reduction in HC, CO and smoke emissions as compared to pure MOBD. In addition, NO_x emissions were also reduced by the catalytic activity of the TiO₂ nanoparticles which reduce the peak combustion temperature. Therefore, TiO₂ nano-fluid had a positive effect on reducing the emissions associated with neat biodiesel.     

PARTICULATE FORMATION IN FUEL OIL COMBUSTION

Abstract

In an attempt to develop a simple screening method to predict potential air pollution by particulate emissions from residual fuel oil burners, a comprehensive and detailed study of the combustion of single droplets of a wide range of oils suspended on a fine thermocouple was made, and compared with particulate emissions from a spray burner fired with identical fuels. Single droplet combustion parameters such as the pre-ignition time (t_i), ignition temperature (T_i), flame time (t_f), coke combustion time (t_i) and temperature (T_c) were derived from temperature-time traces of the droplet and particle combustion. The following relationships were established between the combustion parameters and the original droplet diameter (d_o):

where A, T_i K_i, K_f and K_c are constants dependent upon the fuel. The Conradson Carbon Residue of each fuel correlated with both K_c and particulate emissions. Other relationships between single droplet parameters, fuel composition and particulate emissions were evaluated. A strong relationship was found between T_c and the naturally occuring vanadium content of fuels. Addition of vanadium to a poor fuel increased T_c dramatically and improved both the single particle combustion and the particulate emissions level. A significant correlation between the effect of a calcium additive on T_c in the droplet experiments and its effect on particulate emissions was found. The action of additives cannot be explained simply an catalysis of coke combustion since a catalyst would not normally be effective at the high temperatures of the coke burn-out; all other results indicate diffusion control which is expected under these conditions. It is possible that metals have a catalytic effect earlier in the combustion process during the formation of the coke particle, modifying the structure of the coke and hence affecting its subsequent combustion.     

对省级天然气管网设施公平开放与监管的思考——以陕西省为例

天然气管网设施公平开放和依法监管是绝大多数市场化比较成熟国家的一致选择。中国的天然气管网改革才刚刚起步,特别是在省级管网设施的监管方面,面临诸多现实问题。为此,以陕西省为例,剖析了我国当前省级天然气管网公平开放面临的主要问题:(1)省管网公司采取统购统销模式,不适应公平开放制度管输业务独立的客观要求;(2)省内管输价格管理办法和成本监审办法待建立,管输价格合理性亟待监审;(3)储气调峰和两部制管输定价缺位,不适应公平开放定价规则;(4)居民和非居民用气实行"双轨"制,不利于市场健康快速发展;(5)储气调峰设施建设滞后,影响供气稳定性和开放准入;(6)管网开放更具操作性的规章制度准则有待于完善。由此建议近期的监管工作重点应从以下5个方面入手:(1)督促省内管输企业扎实履行信息公开义务;(2)监管管网设施信息和运营信息公开的及时全面真实有效;(3)推动省内管输价格管理办法和成本监审办法尽早出台;(4)推动省内管网公司管输与销售、管输与下游业务分离;(5)推动大用户直供,改变省网公司统购统销模式。     

Effect of biodiesel fuels on diesel engine emissions

Energy production is heavily dependent on fossil fuels that are not only diminishing, but also are considered the main cause of harmful emissions and global warming. Therefore using vegetable oils such as Jatropha, palm, algae and waste cooking oils as alternative fuels in diesel engines has drawn a great attention. Biodiesel from Jatropha, palm, algae and waste cooking oils has been produced using the transesterification process. Biodiesel from different feedstock is mixed with diesel oil in different proportions e.g. B10 and B20. Biodiesel physical and chemical properties are measured according to ASTM standards. A “single cylinder diesel engine” is employed as the test engine in the present work. Exhaust emissions such as CO, CO₂, NO_x, HC, and smoke are measured and compared with diesel oil. CO, HC, CO₂ and smoke emissions are lower for biodiesel mixtures B10 and B20 (Jatropha, algae and palm) compared “to diesel fuel”. CO₂ emissions from biodiesel blends B10 and B20 produced from waste cooking oil are higher compared to diesel fuel. NO_X emissions from all biodiesel mixtures B10 and B20 increases than diesel fuel for all biodiesel blend B10 and B20.     

Post-combustion of mazut with CO2 capture using aspen hysys

There is a wide range of resources for CO₂ emissions. The net amount of CO₂ emissions in the cement industry due to the consumption of fossil fuels and the chemical processes of cement production under heating raw materials is reported to be in the range of 15–25%; this industry, among all the industries and after the power plants and refineries, is the largest CO₂ gas producer throughout the world. Using CO₂ capture and storage (CCS), it can reduce greenhouse gas emissions in a short time. In this study, the technical feasibility study of recycling CO₂ in Abyek Cement Company, with a cement production capacity of about 12,500 tons per day in two production lines, has been studied as one of the largest cement industries throughout the world. Fuel oil (Mazut) is used as the primary fuel for furnaces in this industry. Affected by combustion, the emissions emitted from the five-stage preheater contain 5/24% vol% of CO₂, 7.6% H₂O, 4.8% vol% of O₂, and 63.1% N₂.     

Detailed modeling study of low-velocity combustion of crude oil at different moisture content

The authors developed a kinetic model of crude oil combustion in different moisture contents and operating conditions by considering the reaction rates and fuel properties. To model the diffusion of gaseous products under high-temperature conditions, the authors used a binary diffusion equation that depends on the physical properties of fuel used and the reaction temperature. Results showed that the combustion of crude oil at higher moisture is not more favorable because of a considerable increase in greenhouse gas emissions, although an optimum condition for output temperature is obvious. It also found that the char conversion is higher for the high residence times. Model validated against the experimental data available in the literature, which showed fully good agreement.     

Mathematical modeling of crude oil combustion at low reynolds number

The use of oxy-fuel combustion of crude oil is regarded as one of the major options for heat and power generation, due to its high density. In this work, we developed a kinetic model to evaluate the potential of heat generation from crude oil combustion in a combustor. Particular emphasis was placed on the influence of excess oxygen ratio (EOR) and reaction time on released greenhouse gas emissions and reaction temperature. Results showed that the reaction time is a key parameter on reaction temperature due to a considerable increase in the rate of reactions. It is also found that the EOR improves the char conversion and reaction temperature simultaneously.     

High energy and low emissions from catalytic combustion of crude oil

Combustion technology has been investigated to effectively and economically heat and power generation. A kinetic model of crude oil combustion in presence of CaO as a catalyst was developed. Effects of CaO mass yield (ppm) on three main parameters including combustion carbon conversion efficiency, reaction temperature, and combustion efficiency were investigated. Results showed that the CaO has a significant effect on the decrease of CO₂, which is the most important greenhouse gas. It also found that the carbon conversion efficiency decreases as the CaO increases, although it is not considerable.     

PARTICULATE FORMATION IN FUEL OIL COMBUSTION

In an attempt to develop a simple screening method to predict potential air pollution by particulate emissions from residual fuel oil burners, a comprehensive and detailed study of the combustion of single droplets of a wide range of oils suspended on a fine thermocouple was made, and compared with particulate emissions from a spray burner fired with identical fuels. Single droplet combustion parameters such as the pre-ignition time (t_i), ignition temperature (T_i), flame time (t_f), coke combustion time (t_i) and temperature (T_c) were derived from temperature-time traces of the droplet and particle combustion. The following relationships were established between the combustion parameters and the original droplet diameter (d_o):

where A, T_i K_i, K_f and K_c are constants dependent upon the fuel. The Conradson Carbon Residue of each fuel correlated with both K_c and particulate emissions. Other relationships between single droplet parameters, fuel composition and particulate emissions were evaluated. A strong relationship was found between T_c and the naturally occuring vanadium content of fuels. Addition of vanadium to a poor fuel increased T_c dramatically and improved both the single particle combustion and the particulate emissions level. A significant correlation between the effect of a calcium additive on T_c in the droplet experiments and its effect on particulate emissions was found. The action of additives cannot be explained simply an catalysis of coke combustion since a catalyst would not normally be effective at the high temperatures of the coke burn-out; all other results indicate diffusion control which is expected under these conditions. It is possible that metals have a catalytic effect earlier in the combustion process during the formation of the coke particle, modifying the structure of the coke and hence affecting its subsequent combustion.     

Syngas production from gasification of high sulfur fuel oil using a CO2 sorbent

Hydrothermal gasification is a thermochemical; process that operates at a temperature range of 800-1000 C, in order to convert solid and liquid feedstocks into chemicals or clean gaseous fuel known as syngas. In this research, an Aspen plus model of heavy oil was developed to investigate the effect of operating conditions and a CO₂ sorbent (CaO) on gas composition and gasification efficiencies. An increase in CaO/F ratio from 0.5 to 1.0 greatly reduced amount of produced CO₂ and increased H₂ due to positive performance of carbonation reaction in conversion of CO₂ to CaCO₃. Carbon Conversion Efficiency (CCE) initially increased by raising CaO/F, and then it is relatively decreased by a further increase in CaO/F.     

Emission characteristics of water-emulsified diesel fuel at optimized engine operation condition

The present study is carried out to analyze the emission characteristics of a natural aspirated diesel engine running with water-in-diesel emulsion fuel at optimized engine operating condition. In the first phase of the experiment, key engine operating parameters say compression ratio and water concentration with diesel are optimized in order to obtain higher performance and lower emissions level at all loading conditions using Taguchi-grey relational analysis based on signal-to-noise ratio and grey relational grade. The optimized condition of engine operating parameters is identified as 10% WC (water concentration) with diesel and 18-CR (compression ratio) at all loading conditions. In the second phase, experiments are conducted at optimal condition and the emission characteristics are compared with neat diesel. The results reveal that 10% WC with diesel at 18-CR exhibits better NO_x emission level at all loading conditions with a marginal penalty in other emissions.