Catalytic combustion concept for gas turbines

Catalytic combustion for gas turbines was investigated, based on a partial catalytic combustion section followed by a homogeneous combustion zone. A pressurized test rig (<25 bar) was built to test the influence of various parameters on this concept using Pd and Pt catalysts.

The pressure influence on the apparent catalytic reaction rate was of the order 0.4, assuming that the reaction kinetics could be described by a power rate function which was of first order with respect to methane. Pd catalysts showed a pressure-dependent temperature for the transition of the active PdO to the much less active Pd. Combining Pd and Pt within one catalyst resulted in a considerably lower transition temperature.

Homogeneous combustion reactions set on from 650°C, depending on the methane concentration, pressure and flow. With inlet temperatures above 800°C the homogeneous combustion always started. At outlet temperatures below 1050°C high CO concentrations could be measured. At higher temperatures the CO, CH₄ and NO_x concentrations were lower than 5 ppm. During several experiments total conversion of CH₄ and CO was observed.     

Industrial gas turbine combustion performance test of DME to use as an alternative fuel for power generation

DME (dimethyl ether, CH₃OCH₃) is both a good alternative fuel for transportation and power generation and an LPG substitute owing to its cleanliness, multi-source productivity and the ease with which it is transported. This study was conducted to verify whether DME is a good fuel for gas turbines and to identify potential problems in fuelling a commercial gas turbine with DME. In this study, the GE7EA gas turbine of the Pyong-tak power plant in Korea was selected as the target of DME application. Combustion performance tests were conducted by comparing DME with methane, which is a major component of natural gas. Most results of the combustion performance tests show that DME is very clean and efficient fuel for gas turbines. However, other results have shown that it is necessary to retrofit a fuel nozzle to the combustor in consideration of the combustion properties of DME in order to enhance the availability and reliability of DME fired gas turbines.     

Diesel and rapeseed methyl ester (RME) pilot fuels for hydrogen and natural gas dual-fuel combustion in compression-ignition engines

This paper presents experimental results of rapeseed methyl ester (RME) and diesel fuel used separately as pilot fuels for dual-fuel compression-ignition (CI) engine operation with hydrogen gas and natural gas (the two gaseous fuels are tested separately). During hydrogen dual-fuel operation with both pilot fuels, thermal efficiencies are generally maintained. Hydrogen dual-fuel CI engine operation with both pilot fuels increases NO_x emissions, while smoke, unburnt HC and CO levels remain relatively unchanged compared with normal CI engine operation. During hydrogen dual-fuel operation with both pilot fuels, high flame propagation speeds in addition to slightly increased ignition delay result in higher pressure-rise rates, increased emissions of NO_x and peak pressure values compared with normal CI engine operation. During natural gas dual-fuel operation with both pilot fuels, comparatively higher unburnt HC and CO emissions are recorded compared with normal CI engine operation at low and intermediate engine loads which are due to lower combustion efficiencies and correspond to lower thermal efficiencies. This could be due to the pilot fuel failing to ignite the natural gas-air charge on a significant scale. During dual-fuel operation with both gaseous fuels, an increased overall hydrogen-carbon ratio lowers CO₂ emissions compared with normal engine operation. Power output (in terms of brake mean effective pressure, BMEP) as well as maximum engine speed achieved are also limited. This results from a reduced gaseous fuel induction capability in the intake manifold, in addition to engine stability issues (i.e. abnormal combustion). During all engine operating modes, diesel pilot fuel and RME pilot fuel performed closely in terms of exhaust emissions. Overall, CI engines can operate in the dual-fuel mode reasonably successfully with minimal modifications. However, increased NO_x emissions (with hydrogen use) and incomplete combustion at low and intermediate loads (with natural gas use) are concerns; while port gaseous fuel induction limits power output at high speeds.     

天然气作为汽车替代燃料的经济分析

对压缩天然气和液化石油气作为汽车替代燃料进行了经济分析,介绍了压缩天然气作为汽车替代燃料的社会效益和环保效益     

棕榈油甲酯的工业用途及应用前景

综述了棕榈油甲酯(生物柴油)的制造、应用情况.棕榈油基生物柴油的发展不仅拓展了棕榈油的工业用途,同时还促进了MES、季铵酯、甘油等相关油化学品的发展.棕榈油基生物柴油的崛起将会对今后棕榈油的工业格局产生深远影响.     

天然气催化燃烧在燃气轮机和锅炉中的应用

综述了天然气催化燃烧技术在燃气轮机和热水锅炉中的应用和研究现状及其发展方向,介绍了几种不同形式的催化燃烧器和一些典型的设计实例,指出催化燃烧技术仍存在的问题。     

尿素包合法分离棕榈油甲酯化产物中C_(16)和C_(18)脂肪酸甲酯

采用尿素包合法分离棕榈油甲酯化物中不同碳链长度的脂肪酸甲酯,为农产品涂膜保鲜材料的开发提供原料。重点考察了尿素用量、溶剂用量、包合时间和包合温度对分离效果的影响,并以尿素用量、95%乙醇用量、包合温度为三因素,C16脂肪酸甲酯和C18脂肪酸甲酯的纯度为二指标,根据Box-Benhnken中心组合试验设计原理,利用Designexpert7.0.1软件分析优化了分离的工艺条件并建立了回归模型。优化的最佳工艺条件如下:在棕榈油甲酯化物用量为20g,尿素用量为35g,95%乙醇用量为120mL,包合温度为5℃,包合时间为16h的条件下,饱和脂肪酸甲酯相中C16脂肪酸甲酯的含量达78.5%,不饱和脂肪酸甲酯相中C18脂肪酸甲酯的含量达93.1%,分别比原料提高36.4%和40.8%。     

黄磷尾气作为替代燃料用于石灰窑煅烧工艺

黄磷尾气含高浓度一氧化碳,其燃烧温度高,热辐射面积大,作为燃料是其最好的资源化利用途径。活性石灰窑所用的燃料是煤粉。黄磷尾气在具备一定条件时作为石灰窑煤粉的替代燃料具有可行生。通过研究黄磷尾气的燃烧特性、石灰窑的结构特点及温度分布、石灰窑对替代燃料的基本要求等,验证了黄磷尾气可以作为石灰窑煤粉的替代燃料。黄磷尾气用于石灰窑的替代燃料,在带来巨大经济效益的同时,也会带来不可估量的环境效益。     

Utilization of unattended methyl ester of paradise oil as fuel in diesel engine

Engine tests have been carried out with the aim of obtaining the performance, emission and combustion characteristics of a diesel engine running on methyl ester of paradise oil (MEPS) and its diesel blends. From the emission analysis it was found that there was a significant reduction in smoke and hydrocarbon emissions by 33% and 22% respectively for MEPS 50 blend and 40% and 27% reductions for MEPS 100. However, there was an increase of 5% and 8% NO_x emission for MEPS 50 and MEPS 100 respectively. Brake thermal efficiencies of MEPS and its diesel blends are slightly lower than that of std. diesel. From the engine analysis, it was found that the performance of MEPS and its diesel blends were similar to that of std. diesel.     

Atomization and combustion of canola methyl ester biofuel spray

The spray atomization and combustion characteristics of canola methyl ester (CME) biofuel are compared to those of petroleum based No. 2 diesel fuel in this paper. The spray flame was contained in an optically accessible combustor which was operated at atmospheric pressure with a co-flow of heated air. Fuel was delivered through a swirl-type air-blast atomizer with an injector orifice diameter of 300 μm. A two-component phase Doppler particle analyzer was used to measure the spray droplet size, axial velocity, and radial velocity distributions. Radial and axial distributions of NO, CO, CO₂ and O₂ concentrations were also obtained. Axial and radial distributions of flame temperature were recorded with a Pt–Pt/13%Rh (type R) thermocouple. The volumetric flow rates of fuel, atomization air and co-flow air were kept constant for both fuels. The droplet Sauter mean diameter (SMD) at the nozzle exit for CME biofuel spray was smaller than that of the No. 2 diesel fuel spray, implying faster vaporization rates for the former. The flame temperature decreased more rapidly for the CME biofuel spray flame than for the No. 2 diesel fuel spray flame in both axial and radial directions. CME biofuel spray flames produced lower in-flame NO and CO peak concentrations than No. 2 diesel fuel spray flames.     

Nonbleach process for the purification of palm C16–18 methyl ester sulfonates

There has long been interest in methyl ester sulfonates (MES) derived from natural or renewable sources, such as palm oil, with considerable effort focused on process development. A major drawback with current process technology is the formation of dark brown impurities that create aesthetic and odor issues in the final product. These issues are usually addressed by bleaching rather than by chemical purification. This paper reports on a simple yet highly effective nonbleach, two-step process for purifying palm C16–18 potassium methyl ester sulfonates. The first step comprises addition of water to the impure surfactant mixture. Preferably, the temperature of the system is maintained above the Krafft point of the surfactant, thereby completely solubilizing the surfactant and associated impurities. Once completely dissolved, the surfactant mixture is allowed to cool, and the potassium-neutralized methyl ester sulfonate precipitates out selectively. In the second step, the purified surfactant is recovered by gravity- or pressure-filtration or by centrifugation, followed by drying. The process significantly improves C16–18 MES analytical purity and color without raising safety or environmental concerns. It also allows for the purification of products derived from lower-grade methyl esters, resolves odor issues, and does not require use of substantial amounts of solvent such as methanol.     

Tar reduction through partial combustion of fuel gas

A partial combustion burner is introduced as a cleaning system for the tar content of gaseous (bio) fuel. The results of experiments, using a synthetic low calorific gas mixture, demonstrate the effectivity of the proposed process. In these experiments naphthalene is added as a model tar component. The effect of partial combustion of the fuel gasmixture on the naphthalene is examined for different air/fuel ratios (λ) and varying hydrogen-methane fuel concentrations. For a fuel gasmixture with high methane concentrations or for higher λ-values the total tarcontent slightly decreases. In this case the naphthalene polymerises, i.e. forms higher ring components and sometimes even turn into soot. At lower λ's and higher hydrogen concentrations the tarcontent strongly decreases. Moreover, the naphthalene is now cracked, i.e. converted into lighter tars and permanent gases. It is found that, for fuel gases representative for biogasification products and at a λ of 0.2, the presented burner reduces the tar content of the gas with over 90% by cracking. The paper ends with a short discussion on the conditions that may determine the cracking/polymerisation mechanism.     

Performance and combustion characteristics of a DI diesel engine fueled with waste palm oil and canola oil methyl esters

This study discusses the performance and combustion characteristics of a direct injection (DI) diesel engine fueled with biodiesels such as waste (frying) palm oil methyl ester (WPOME) and canola oil methyl ester (COME). In order to determine the performance and combustion characteristics, the experiments were conducted at the constant engine speed mode (1500 rpm) under the full load condition of the engine. The results indicated that when the test engine was fueled with WPOME or COME, the engine performance slightly weakened; the combustion characteristics slightly changed when compared to petroleum based diesel fuel (PBDF). The biodiesels caused reductions in carbon monoxide (CO), unburned hydrocarbon (HC) emissions and smoke opacity, but they caused to increases in nitrogen oxides (NO_x) emissions.     

A comprehensive experimental investigation of combustion and heat release characteristics of a biodiesel (hazelnut kernel oil methyl ester) fueled direct injection compression ignition engine

In the present study, hazelnut (Corylus avellana L.) kernel oil was transesterified with methanol using potassium hydroxide as catalyst to obtain biodiesel and a comprehensive experimental investigation of combustion (cylinder gas pressure, rate of pressure rise, ignition delay) and heat release (rate of heat release, cumulative heat release, combustion duration and center of heat release) parameters of a direct injection compression ignition engine running with biodiesel and its blends with diesel fuel was carried out. Experiment parameters included the percentage of biodiesel in the blend, engine load, injection timing, injection pressure, and compression ratio. Results showed that hazelnut kernel oil methyl ester and its blends with diesel fuel can be used in the engine without any modification and undesirable combustion and heat release characteristics were not observed. The modifications such as increasing of injection timing, compression ratio, and injection pressure provided significant improvement in combustion and heat release characteristics.     

脂肪酸甲酯降膜蒸发器沸腾传热性能

利用传统的多管排列式蒸发器对高黏度、易结垢的混合物进行蒸发,容易造成布液器堵塞,且结垢后的传热管难以清理。因此根据物料特性,本文设计了一种新型的降膜蒸发器,采用大降液孔加倾斜环板进行布膜,利用内径较大的锥筒作为传热壁面,并以粗甲酯作为试验工质对蒸发器的降膜蒸发传热系数随蒸发器筒体半锥度角、液膜流动雷诺数以及输入热通量之间的关系进行了试验研究。结果表明：该型蒸发器对于上述工质具有较好的适用性,蒸发系统能够在保持较高的传热系数的条件下,连续运行而不发生堵塞;蒸发器筒体锥度角有效地强化了降膜蒸发传热过程,而较大的热通量及进料流量在一定程度上却不利于蒸发传热。最后建立了降膜蒸发传热系数随蒸发器筒体半锥角和流动准数之间的经验关联式。     

Utilizing Philippine Calatrava coal-diesel oil mixture (CDOM) as alternative fuel for industrial steam generator

The fast depletion of fuel oil and the continuous increase in the demand for power is a global issue. In the Philippines, the demand for diesel oil is expected to increase significantly in a 20-year period as projected by the Department of Energy. In line with the Philippine Government's thrust to lessen the dependence on imported energy, the agenda for the search for alternative fuel is highly prioritized. Thus, this paper presents the results of the study on performance analysis and efficiency test of a diesel oil fired industrial steam generator using Philippine Calatrava coal-diesel oil mixture (CDOM) as alternative fuel. A computer program was developed in HyperText Markup Language (HTML^©) and JavaScript^© to aid the computation of the adiabatic flame temperature from the governing system of equations based on the heat interaction between CDOM fuel, combustion air and products of combustion to determine the most desirable alternative fuel. Actual experimentation for the determination of CDOM fuel properties was also conducted to verify the alternative fuel selected through theoretical calculations. Results showed that the CDOM fuel with a particle size passing 75 μm (−200 mesh) sieve having a proportion of 5% pulverized coal-95% diesel oil and 10% pulverized coal-90% diesel oil could be handled throughout the test with no degradation of the industrial steam generator. The steam generator efficiency using diesel oil is close to the steam generator efficiency using both CDOM fuels.     

Kinetics of methyl ester production from mixed crude palm oil by using acid-alkali catalyst

The production of biodiesel from high free fatty acid mixed crude palm oil using a two-stage process was investigated. The kinetics of the reactions was determined in a batch reactor at various reaction temperatures. It was found that the optimum conditions for reducing high free fatty acid (FFA) in MCPO (8-12 wt.%/wt oil) using esterification was a 10:1 molar ratio of methanol to FFA and using 10 wt.%/wt of sulfuric acid (based on FFA) as catalyst. The subsequent transesterification reaction to convert triglycerides to the methyl ester was found to be optimal using 6:1 molar ratio of methanol to the triglyceride (TG) in MCPO and using 0.6 wt.%/vol_TG sodium hydroxide as catalyst. Both reactions were carried out in a stirred batch reactor over a period of 20 min at 55, 60 and 65 °C. The concentration of compounds in each sample was analyzed by Thin Layer Chromatography/Flame Ionization Detector (TLC/FID), Karl Fischer, and titration techniques. The results were used for calculating the rate coefficients by using the curve-fitting tool of MATLAB. Optimal reaction rate coefficients for the forward and reverse esterification reactions of FFA were 1.340 and 0.682 l mol⁻¹ min⁻¹, respectively. The corresponding optimal transesterification, rate coefficients for the forward reactions of TG, diglyceride (DG), and monoglyceride (MG) of transesterification were 2.600, 1.186, and 2.303 l mol⁻¹ min⁻¹, and for the reverse reactions were 0.248, 0.227, and 0.022 l mol⁻¹ min⁻¹, respectively.