Low Temperature Fischer Tropsch Process Research Articles

Impacts of advanced diesel combustion operation and fuel formulation on soot nanostructure and reactivity

Advanced diesel combustion, accomplished via a single pulse fuel injection and high levels of exhaust gas recirculation (referred to as “PCCI”, partially-premixed charge compression ignition), is shown to be a path to reduce oxides of nitrogen and particulate matter simultaneously. This is well established in the literature. Less established is the extent to which such dilute combustion processes influence soot formation and affect soot that is emitted from diesel engines under such combustion modes. This work focuses on characterization of the nanostructure and oxidative reactivity of soot generated by a light-duty turbodiesel engine operating under a PCCI combustion mode, a dilute, low-temperature combustion process. Previous work on a type of PCCI combustion, referred to as high-efficiency clean combustion (HECC), showed soot samples having a fullerenic nanostructure, characterized by high levels of tortuosity of the fringe layers as seen in transmission electron micrograph images and as quantified using an image processing algorithm. Thermogravimetric analysis of the HECC mode soot samples showed that they displayed higher rates of oxidation than soot samples from a conventional diesel combustion mode. The present work returns to PCCI combustion, considering the timing of the main fuel injection, and the effects of operating on fuels rich in n-alkanes, particularly a fuel produced from a low temperature Fischer-Tropsch process (LTFT) and a renewable diesel fuel (RD) produced via hydrodeoxygenation of a plant oil. PCCI combustion conditions yield soot that shows higher reactivity compared to soot from the conventional combustion mode regardless of fuel type. LTFT and RD fuels produce soots with lower reactivity compared to ULSD. Soots produced from PCCI combustion have higher surface oxygen concentration and higher proportion of amorphous carbon. In addition, TEM images show that PCCI soots from all three fuels have smaller primary particle and particle aggregate sizes, and smaller graphene layers. These properties explain the higher reactivity of soot from PCCI combustion. The less reactive soots, which are produced from LTFT and RD fuel under conventional combustion, show internal burning during oxidation. However, soots with higher reactivity which are produced from late injection PCCI combustion and ULSD show shrinking core oxidation, likely because of their overall amorphous structure.

Development of Integrated High Temperature and Low Temperature Fischer-Tropsch System for High Value Chemicals Coproduction

The conventional indirect coal-to-liquids process for transportation fuel production suffers from inefficiency in syncrude utilization and poor economic performance. This is largely because the FT syncrude are not properly used. In consideration of the potential synergies in fuel quality improvement and chemicals coproduction, for further high value utilization of the hydrocarbon products, the novel HTFT-LTFT system integrated high temperature Fischer-Tropsch process and low temperature Fischer-Tropsch process together is proposed based on the advanced coal gasification and FT techniques and modelled in Aspen Plus. Energy, exergy analysis and a detailed economic analysis are performed. The synergies of the integrated system is also discussed by comparing with the separated HTFT/LTFT system. Results show that the integrated HTFT-LTFT systems can increase the annual income by more than 10% by high utilization of FT syncrude and reduce the capital investment by 18.2% by sharing infrastructure. Higher energy and exergy efficiencies as well as internal rate of return (IRR) are achieved by the integrated systems. The integrated HTFT-LTFT system is more efficiently and economically than the separated HTFT/LTFT system. Therein the integrated HTFT-LTFT system coproduce both olefins and base oils simultaneously presents an excellent economic performance with IRR of 18%, much higher than the 4.7% of the separated HTFT/LTFT system.

Low Temperature Fischer-Tropsch fuels from syngas: Kinetic modeling and process simulation of different plant configurations

Fischer–Tropsch synthesis is considered a key component ofalternative-to-oil technology pathways to obtain synthetic liquid hydrocarbons usable for fuels and chemicals. In view of the growing interest and establishment of more and more syngas-to-liquids projects, it is essential to develop new process models that are at the same time detailed and practical-to-use. Aiming at this target, up-to-date literature kinetics research results have been converted into a well-established industrial process simulator. Low Temperature Fischer-Tropsch process oriented to middle distillate production is modeled in detail in this work. Detailed kinetic based on Langmuir–Hinshelwood–Hougen–Watson approach are exploited rather than traditional product distribution laws, both for Fischer Tropsch synthesis as well as hydrocracking. By varying the operating conditions and system process configurations, it is possible to simulate and analyse the performance of once-through and recycle plants with different product outputs.

Impact of Fuel and Injection Timing on Partially Premixed Charge Compression Ignition Combustion

Advanced combustion modes have drawn much attention from researchers due to increasingly strict emissions regulations. Partially premixed compression ignition (PCCI) combustion creates a partially premixed charge inside the cylinder before ignition occurs. As a result, NOx and particulate matter (PM) emissions can be reduced simultaneously relative to those of conventional diesel combustion. The basic operating mechanism of PCCI combustion is to prolong the time period for mixing of the fuel–air mixture by separating the end of injection and start of combustion. Three different fuels, ultralow sulfur diesel (ULSD), diesel fuel produced via a low temperature Fischer–Tropsch process (LTFT), and a renewable diesel (RD), which is a hydrotreated camelina oil, are tested in this study. Engine combustion performance, PM, NOx, CO, total hydrocarbon (THC) emissions, particle size distribution, soot morphology, and nanostructure are examined for conventional combustion and various PCCI conditions. PCCI combustion c...

Alternative method for bulk modulus estimation of Diesel fuels

The knowledge of Diesel fuel properties has great relevance for the analysis and comprehension of phenomena related to fuel injection, fuel–air mixture formation and diesel combustion processes. This work proposes an alternative method for estimating the bulk modulus of diesel fuels by means of an experimental installation commonly used for determining fuel injection rates from common rail injection systems. Three fuels were tested in the mentioned installation: commercial Diesel fuel (blended with 5.8% of biodiesel), hydro-treated vegetal oil (HVO) and gas to liquid (GTL) fuel from natural gas by means of low temperature Fischer Tropsch process. Results were obtained by testing two different injectors (solenoid operated and piezoelectric injectors) under different injection pressures and energizing times. Fuel temperature at inlet of the high pressure injection pump was controlled, keeping constant the pressure inside the fuel injection indicator. From the experimental work, data analysis and post-processing, bulk modulus of fuels tested has been estimated and compared to results obtained by diverse authors with different experimental installations and methods. Results obtained in this work show small differences compared to published data. Additionally, the initial time lag between the signal of the electric pulse when the injector is energized and the beginning of the injection rate profile depends only on the type of injector without influence of type of fuel and operating conditions. However, the rear time lag between both mentioned profiles depends only on injector type (when the solenoid operated injector was tested) while, with piezoelectric injector, it also depends on both energizing time of the injector and injection pressure.

Impact of alternative fuels on performance and pollutant emissions of a light duty engine tested under the new European driving cycle

Two alternative fuels, a gas to liquid (GTL) fuel from a low temperature Fischer–Tropsch process and a biodiesel produced from animal fats, have been tested using a light duty diesel engine with road load simulation (RLS) under the New European Driving Cycle (NEDC). The engine used has a variable geometry turbocharger (VGT), exhaust gas recirculation with cooling (EGR), common rail with split fuel injection and diesel oxidation catalyst (DOC). Regulated emissions have been evaluated and noticeable reductions in THC and CO were observed with both alternative fuels whereas only slight decrease was obtained in NOx emissions with biodiesel. With respect to results on particle matter, important reductions in both particle number and particle mass were obtained with both alternative fuels.

Strategies for active diesel particulate filter regeneration based on late injection and exhaust recirculation with different fuels

Wall flow–type particulate filters are used in diesel vehicle engines to reduce particulate emissions below the limits established in regulations Euro 5 and Euro 6. The soot accumulated in the trap is eliminated during regeneration processes, often combining passive strategies with active ones. Active regeneration is conducted by modifications of the engine control parameters with respect to those set for normal vehicle operation. In this work, three of these parameters were modified to look for an optimized regeneration strategy, considering fuel consumption, gaseous emissions and rate of regeneration. The selected parameters were injection timing (affecting all injection events), exhaust gas recirculation and amount of postinjected fuel. The fuel tested was considered as an additional variable, and therefore, tests were performed with three different fuels: an ultra-low sulfur diesel fuel, a biodiesel fuel produced from animal fat and a gas-to-liquid fuel from low-temperature Fischer–Tropsch process. It...

Estimation of mid‐distillates production rate in a low temperature Fischer–Tropsch process

AbstractBACKGROUND: The Fischer–Tropsch process is the most important path for converting natural gas to high quality liquid hydrocarbons. Low temperature Fischer–Tropsch synthesis in slurry bubble column reactors with cobalt‐based catalysts is used for mid‐distillates production.RESULTS: In this work the slurry bubble column reactor was simulated by applying the two‐bubble class mathematical model. In addition, the effect of operating parameters on synthesis gas conversion was studied. The distribution of products was also predicted from the simulation framework.CONCLUSIONS: The effect of synthesis gas inlet velocity on mid‐distillates production rate was studied in the present work. A maximum production rate for mid‐distillates of about 23 kg s−1 was predicted from the simulation program. Copyright © 2011 Society of Chemical Industry

Potential for reducing emissions in a diesel engine by fuelling with conventional biodiesel and Fischer–Tropsch diesel

A gas-to-liquid (GTL) fuel derived from Low Temperature Fischer–Tropsch process has been tested in an automotive diesel engine fulfilling Euro 4 emissions regulations. Both regulated and non-regulated emissions have been compared with those of a commercial diesel fuel, a commercial biodiesel fuel and a GTL–biodiesel fuel (30% and 70% v/v, respectively) in order to check blending properties, synergistic effects and compatibility between first and second generation production technologies for biofuel consumption in current diesel engines. After presenting a detailed literature review, and confirming that similar efficiencies are attained with the four tested fuels under identical road-like operating conditions (this meaning fuel consumption is inversely proportional to their heating values), significant reductions in smoke opacity, particulate matter emissions and particle number concentration were observed with both GTL and biodiesel fuels, with small changes in NO x emissions. Compared with the reductions in PM emissions derived from the use of biodiesel fuels, those derived from using GTL fuels were quite similar, despite its lower soot emissions reductions. This can be explained by the lower volatile organic fraction of the PM in the case of GTL. By adequately blending both fuels, a considerable potential to optimise the engine emissions trade-off is foreseen.