THE IMPORTANCE OF PYROLYSIS IN DIESEL IGNITION OF RESIDUAL FUEL OILS

Recent attempts to increase yields of distillate fuels from crude oil have resulted in a decline in the ignition quality of residual fuel oils and claims of ignition problems in large marine Diesel engines. This has revived an interest in fundamental studies of the ignition of liquid fuels and in new ways of defining and measuring ignition quality.

As part of an extensive study of the ignition of a range of residual fuels oils and during the development of novel teats of ignition quality it became obvious that thermal cracking of the fuel could play an important part in the pre-ignition chemistry. This paper reports kinetic data from simple experiments performed on the pyrolyses of residual fuel oils. Small samples and high heating rates were used to try to match the conditions inside a Blow-speed Diesel engine. This data has been used to assess the contribution that thermal cracking makes to ignition processes.

Pyrolyses were carried out on a small silica-coated platinum coil in the inlet of a gas chromatograph. Light hydrocarbon pyrolysis products were formed, and the extent and rate of cracking determined at four temperatures.

Assuming that reaction took place on a surface surrounding the oil and that a constant supply of reactants were available, pseudo zero order rate constants for the initial part of the reaction were evaluated. They showed an Arrhenius relationship with temperature giving an overall apparent activation energy of 110 kJ mol^-1. Extrapolating rate constants to temperatures expected in Diesel engines, and assuming typical droplet sizes end ignition delays, it was shown that thermal cracking of fuels was possible before ignition and that it is likely that these reactions will have a strong influence on the processes leading to ignition. It was also shown that the presence of oxygen greatly increases the rate of thermal cracking.     

IGNITION DELAY CHARACTERISTICS OF SOME TURKISH VEGETABLE OIL-DIESEL FUEL BLENDS

ABSTRACT

Vegetable oils have chances to be used in Diesel engines as alternative fuels contributing to the solution of some agricultural, environmental and economical problems. Direct use of them has some technical problem yet but as blended fuels with diesel fuel or esters they have places on the application area. In this paper the effect of the compression ratio on ignition delay is investigated in an ASTM-CER engine working with four different types of vegetable oil of Turkish origin (sunflower, corn, soybean, and olive oil) blended with grade No.2-D diesel fuel at a ratio of 20/80 (v/v) and the results are compared with baseline diesel fuel. Longer ignition delay periods have generally been obtained for blend fuels ranking from olive oil to sunflower oil as compared to diesel fuel.     

IGNITION DELAY AND SOOT EMISSION CHARACTERISTICS OF METHANOL-DIESEL FUEL BLENDS

ABSTRACT

Alcohols, as alternative fuels, may contribute to the solution of environmental and economical problems to a certain extend. But, they seem to have little chances to be directly used in Diesel engines because of their low cetane number. However, as blended fuels with diesel fuel they have places on the application area. In this study, the effect of the compression ratio on ignition delay and soot emission for methanol-diesel fuel blends with various blending ratios is investigated on an ASTM-CFR engine and the results are compared with baseline diesel fuel. Longer ignition delays and less soot emissions have been obtained for blend fuels as compared to diesel fuel.     

IGNITION DELAY CHARACTERISTICS OF SOME TURKISH VEGETABLE OIL-DIESEL FUEL BLENDS

Vegetable oils have chances to be used in Diesel engines as alternative fuels contributing to the solution of some agricultural, environmental and economical problems. Direct use of them has some technical problem yet but as blended fuels with diesel fuel or esters they have places on the application area. In this paper the effect of the compression ratio on ignition delay is investigated in an ASTM-CER engine working with four different types of vegetable oil of Turkish origin (sunflower, corn, soybean, and olive oil) blended with grade No.2-D diesel fuel at a ratio of 20/80 (v/v) and the results are compared with baseline diesel fuel. Longer ignition delay periods have generally been obtained for blend fuels ranking from olive oil to sunflower oil as compared to diesel fuel.     

IGNITION DELAY AND SOOT EMISSION CHARACTERISTICS OF METHANOL-DIESEL FUEL BLENDS

Alcohols, as alternative fuels, may contribute to the solution of environmental and economical problems to a certain extend. But, they seem to have little chances to be directly used in Diesel engines because of their low cetane number. However, as blended fuels with diesel fuel they have places on the application area. In this study, the effect of the compression ratio on ignition delay and soot emission for methanol-diesel fuel blends with various blending ratios is investigated on an ASTM-CFR engine and the results are compared with baseline diesel fuel. Longer ignition delays and less soot emissions have been obtained for blend fuels as compared to diesel fuel.     

STUDIES ON FLUID CATALYTIC CRACKING OF HYDROPROCESSED FEEDSTOCKS

ABSTRACT

Worldwide public concern about environment and increased demand for better quality fuels by automobile industries has necessiated developed countries like USA, UK and Japan to stipulate stringent specifications for petroleum fuel products. Fluid catalytic cracking (FCC) is a major secondary process for fuel products and quality of products coming from FCC unit depends largely on the feedstock used. FCC naphtha makes up for 30–40% gasoline in a typical refinery pool. This FCC naphtha contributes to around 90% of the gasoline pool sulphur. Hence, sulfur and nitrogen reduction have become essential for meeting the quality requirements of fuel products resulting in the growing importance for pretreatment of FCC feedstock. In the present work, studies were carried out in pilot plant on hydrotreatment of feedstock for FCC unit. The results indicate better quality products for treated feedstock vis-a-vis untreated heavy vacuum gas oils from Persian Gulf (PG) crudes. Hydroprocessing of FCC feed has helped refiners in meeting the fuel products quality especially with feedstocks, which are characterized as heavy and refractory in nature.     

AUSTRALIAN BROWN COAL/OIL MIXTURES AS A FUEL FOR DIESEL ENGINES; ENGINE PERFORMANCE AND ECONOMIC VIABILITY

ABSTRACT

CSIRO Division of Energy Technology has used mixtures of finely ground, chemically beneficiated, Australian brown coal (up to 30% by weight, maximum particle size less than 13 microns) and automotive diesel oil (ADO) to fuel an essentially unmodified single cylinder diesel engine operating at 800, 1200 and 1500 r/min. Engine performance tests indicate that brown coal can be used as a fuel extender to reduce consumption of the conventional liquid diesel fuel (ADO). Partially burnt coal agglomerates were identified in the engine exhaust and there were indications of late burning at the higher engine speeds and coal concentrations. Engine brake thermal efficiency ratio is identified as an important parameter when evaluating the thermal performance and economic viability of new fuels for internal combustion engines. A simple economic model based on ‘payback period’ is developed and used to assess the viability of converting an existing diesel engine powered plant to operate on the coal/oil mixture fuels (COM). The simple economic analysis technique can also be applied to other fuel formulations and fuel extenders. Conversion of large, slow speed stationary diesel engines to operate on brown COM fuels is shown to be uneconomical, given a projected brown coal cost of 215 $A/t (including processing).     

FUEL INSTABILITY STUDIES: THE SYNTHESIS OF LONG CHAIN ALKYL SUBSTITUTED INDOLES

ABSTRACT

The reactions that are responsible for fuel instability are complex and not well understood. GC/MS analysis of many different middle distillate and fuel oils showed that substituted indoles were always present in both the fuel itself and in the sediments formed by these fuels. The alkyl chain length of substitution of indoles found in fuels varies with distillation range. Indoles found in the middle distillate fraction have an average alkyl chain length of one to eight carbons while in fuel oils, the alkyl side chain can be up to twelve or fourteen carbons in length. Commercially, only short chain alkyl substituted indoles are available. This paper presents our results for the synthesis of long alkyl chain substituted indoles to be used for instability studies.     

浅谈点燃式发动机的代用燃料

介绍了点燃式发动机的主要代用燃料—天然气、液化石油气、氢和醇类,根据其自身所具有的性质,分析了其作为点燃式发动机代用燃料的主要优缺点,详细介绍了氢燃料在点燃式发动机中的应用,并对这几种代用燃料在提高点燃式发动机性能方面进行了细致的比较。     

BEHAVIOR OF SHALE OIL JET FUELS AT VARIABLE SEVERITIES

ABSTRACT

Catalytic hydro processed ahale oil jet fuels In the USA were characterized and compared with petroleum Jet fuel to demonstrate their possibility as a conventional Jet fuel substitute. The shale oils (Geoklnetica, Occidental, Faraho and Tosco II) were hydrotreated in a 0.0508m ID by 1.524m long reactor containing Ni/MO/A1203 catalyst. The fractionated hydrogenated shale oila at Jet fuel ranges (120-300^°C) were analyzed for composition and physical properties. The increasing hydroprocessing severity proport1nally decreased nitrogen, sulfur, olefins, and aromaticB, and increased hydrogen content. The nitrogen content even at high severity conditions was considerably higher than that of conventional Jet fuel. Sulfur and olefin contents were lower at all severities. The heat of combustion and the physical properties, except the freezing point, were comparable to petroleum Jet fuels. The yields of Jet fuels increased proportionally to increased severity. The study showed that high severity hydroprocessing gave better performance in processing shale oils to Jet fuels.     

OPERATION AND EFFICIENCY OF CYCLIC COAL BURNING ENGINES

ABSTRACT

A method of burning porous solid fuels in a fixed bed and in pellet or chunk form is described wherein compressing the fuel with air forces oxygen deep into the fuel pores where primary reaction occurs. Subsequent expansion brings the primary re action gases out of the fuel pores where secondary reaction with additional oxygen can occur. Useful mechanical work can be produced by carrying out this compression-reaction-expansion process within a piston engine or within a gas turbine engine. Maximum useable engine speeds are not limited by burning rates but by pressure drop due to gas flow into and out of the fuel pores. Approximate thermal efficiency relations are presented which show the piston engine process to be less efficient than the turbine engine process due to incomplete expansion in the piston engine. Engines using this cyclic porous burning are somewhat less efficient than engines using constant volume burning at minimum volume, as in Otto engines, or constant pressure burning at maximum pressure as in Brayton engines. This latter efficiency difference is due to the cyclic burning being distributed throughout the compression and expansion rather than occurring all at the end of compression.     

COKE CHARACTERISTICS IN RELATION TO THE COLLOIDAL. MATTER OF PETROLEUM FOR THERMAL. PROCESSES

Abstract

The purpose of this work is to research the characteristics of the production of coke in thermal and hydrothermal cracking from residual oils and their deasphalted oils Using ethyl acetate, because it allows the elimination of both resins and asphaltenes (colloidal matter) from the parent oil in only one step. This improves the deasphalted oil as coke precursors and basic nitrogen compounds present in the resin fraction are practically eliminated.

A 104 ml batch autoclave reactor with a cooling system was used for the thermal and hydrothermal cracking experiments. This reactor can withstand temperatures of up to 500^°C, pressures of 500 bar and a rocking velocity of 1 Hz. The influence of the temperature was investigated at 400, 425 and 450^°C and at 0, 20, 40, 80,     

ANALYSIS OF INSTABILITY DEPOSITS TO THERMAL IN AVIATION JET FUELS

ABSTRACT

Gas chromatographic systems using nitrogen phosphorus and flame ionization detectors were utilized to analyze JP-5 fuels for reactants that lead to thermal instability products. High and low stability fuels defined by Naval Research Laboratory Gravimetric Jet Fuel Thermal oxidation Test (GRAV JFTOT) were chosen to make gross and detailed comparisons of the reactants present in each fuel. Whole fuel samples were analyzed and compared. An acid extract, HeOH extract, and MeOH saturated with MDA extract were also analyzed for each fuel sample using GC analysis. This study demonstrates the usefulness of extraction of bases and polars in defining thermal instability reactants in jet fuels. Data indicates the MDA does not appear to be useful as an extraction modifier for polars.     

APPLICATION OF X-RAY CT IMAGING AS AN ALTERNATIVE TOOL FOR CLOUD POINT DETERMINATION

ABSTRACT

This study explains the use of X-Ray CT (computerized tomography’) as an alternative tool for cloud point determination of crude oils and dark fuel oils by showing the results for artificially prepared transparent oils. The technique is fully computerized and data gathering and analysis are achieved by taking the advantage of the processing of the CT images. In the study, the cloud points of diesel oil samples containing 5%, 10% and 15 % additional wax were determined with this new technique. Results show that the cloud points determined with this technique and the standardized ASTM D-3117 method are very close. This encourages the use of the proposed technique to determine the cloud point of transparent distillate fuels and dark fuel oils and crude oils, whose cloud points can not be determined easily and accurately.     

THERMAL CRACKING,THERMAL HYDROCRACKIKG AND CATALYTIC CRACKING OF DEASPHALTED OILS

ABSTRACT

This paper present results of the thermal hydrothermal and catalytic cracking of heavy residues. In this investigation, ethvl acetate was used as deasphalting agent because it allows the elimination of both resins and asphaltenes from the oil in only one step. This improves the deasphalted oil Quality as, coke precursors and basic nitrogen compounds present in the resin fraction are practically eliminated)

Kinetic measurements of thermal cracking indicate a faster cracking for deasphalted oils. The yield of product oil boiling under 200°C is higher for the deasphalted oil compared with the original feeds. Coke formation shows an opposite trend. Asphaltenes formation decreases with time and temperature due to this latter trend.     

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.     

溶剂精制提高催化裂化柴油的安定性

找到了一种用于催化裂化柴油精制的溶剂，使精制油的催速储存安定性沉渣和颜色均达到了优级轻柴油的标准（沉渣＜20mg／100mL，色号不大于3．5）。剂油体积比在1：10－1：500范围内，精制油收率达到99％以上。溶剂在精制油中的含量低，经水洗即可除去，溶剂与抽出物分离后可以循环利用。     

CHANGE OF PHYSICAL AND THERMAL DECOMPOSITION PROPERTIES OF IN SITU HEAVY OIL WITH STEAM TEMPERATURE

ABSTRACT

Ikiztepe crude oil was subjected to four different steam temperatures during steam injection which was applied as an enhanced oil recovery process on a linear limestone model saturated with oil. Produced oils were characterized using density, viscosity measurements, pyrolysis experiments utilizing TGA and elemental analysis runs. Results showed that produced crude oils change in measured characteristics as compared to the original oil. These changes include an increase in H/C, and cracking activation energy, decrease in density, viscosity and amount of residue remaining after cracking (coke). Also, decrease in asphaltene amount, changes in the elemental composition of asphaltenes and increase in the cracking activation energies were observed at 225 °C run. These measurements show that the produced oils get lighter and differ compositionally from the original oil as steam temperature increases. Decrease in elemental sulphur amount is one of the major changes when environmental considerations are concerned. Residual oil left in the limestone pack on the other hand shows an increase in the low temperature oxidation (LTO), fuel deposition (FD) and high temperature oxidation (HTO) activation energies as determined from TGA combustion experiments on the samples taken from the pack after steam injection experiments.     

THE PRODUCTION OF SYNTHETIC FUELS FROM NIGERIAN TANBAND BITUMEN

ABSTRACT

Synthetic fuels are expected to become a major source of energy supply in the future and major sources of synthetic fuels will be coal, shale oil and tar sand.

This paper presents an investigation of hydrotreating using a batch process for bitumen from Nigerian oil sand. The chatacteriistics in conversion of asphaltencs were studied. Various ananlyses were performed to obtain the properties of the bittemen before and after conversion to synthetic crude, e.g., changes of heteroatoms such as sulphur decreases of asphaltics, viscosity add specific gravity, and increases of distillate yield.

The process liquid fuel streams that are highly aromatic. The data suggest that the use of hydrogen causes stabilization of reactive intermediates rather than saturation of thermal products.     

INFLUENCE OF FEEDSTOCK COMPOSITION ON THE YIELD OF TOTAL CYCLE OIL IN FLUID CATALYTIC CRACKING

ABSTRACT

With a view to gaining an insight into the understanding of the factors responsible for the maximization of the total cycle oil (TCO) in the fluid catalytic cracking of the vacuum gas oils (VGOs) including the one from Bombay High (BH), necessitated by a greater demand for the diesel fuel compared to gasoline, in India, studies have been carried out on three different VGOs in a Xytel Auto Mat II unit over two REY based FCC catalysts differing in their zeolite content using a fixed bed reactor. The fact that the yield of CLO (370^°C+) from BH VGO was much higher than would be expected for a predominantly paraffinic feedstock has led to studying the cracking to compositionally different concentrates isolated from BH VGO and the results are discussed.