Fuel Gas Composition Research Articles

Effect of Fuel Gas Composition and Excess Air on VOC Emissions from a Small-Scale, Industrial-Style Burner

Furnace-out emissions of benzene, toluene, cthylbenzene, and the xylenes have been measured for a research-grade, industrial-style diffusion flame burner operating under well-controlled conditions representative of refinery process heaters. Flame structure was also evaluated by means of visible emission imaging. Excess air was varied from 50% to sub-stoichiometric, The fuels were methane and blends of methane, hydrogen, and propane used to simulate the process gas burned in refineries. Each fuel was tailored so that the inlet and boundary conditions on the flame were invariant between fuels—minimizing fluid mechanic differences. The results show emission levels < 3 ppbv for toluene and < 0.5 ppbv for the other species under normal firing conditions. This is in contrast to emissions from 10 to 150 ppbv observed in refinery field tests (WSPA, 1994). They also show an increase in emissions with fuel hydrogen and propane contents. Under sub-stoichiometric conditions, emissions increase by orders of magnitude,...

Specification, Development, and Testing of the FT8-2 Dry Low NOx Control System

This paper describes the specification, development, and testing of the FT8-2 Dry Low NOx control system, and how the lean burn process requires an integration of the control system and combustion hardware. The FT8-2 digital fuel control system was developed to achieve the precise multizone fuel metering of both gas and liquid fuels, the calculation of combustor air flow necessary to achieve Dry Low NOx and the traditional governing/limiting control loops necessary for safe, stable engine operation. The system design goals were accomplished by the concurrent development of software-based fuel metering algorithms and fuel metering hardware. The fuel metering hardware utilizes an all-electronic valve positioner, employing a combination of feedback and software to achieve closed-loop control of actual fuel flow. Extensive testing under actual gas flow conditions and closed-loop bench testing using a real time engine model and fuel system model was conducted to prove system operation and develop system transient response prior to installation on the test engine. The setup and results of the flow testing and closed-loop testing are described. The paper describes the control scheme used to apportion the gas fuel between combustion zones and how external conditions such as ambient temperature and fuel gas composition affect the apportionment. The paper concludes with a description of the control system installation in the engine test cell and a review of engine test results.

内部改質方式の溶融炭酸塩型燃料電池の経時特性

Internal reforming molten carbonate fuel cell realizes high power generating efficiency by utilizing its generated heats in the cell to convert fuels into hydrogen rich gases. One of the crucial problem is deactivation of catalysts loaded in the cell. Deactivation phenomena of catalysts have been investigated by analyzing various catalysts after operating several thousands hours. The analyzed data suggest that the deactivation of catalyst is caused by the sintering of catalyst and support material. A correlation equation has been derived relating between the surface area or the specific dameter of catalysts and modified operation time, which explains the effect of operating temperature. Decay characteristics of reforming rate of internal reforming fuel cells have been predicted using this equation. They have shown same trend with experimental decay characteristics of several cells and stacks, utilizing various fuel gas compositions under the different flow patterns and the different operation temperatures.

Development and assessment of correlations for predicting stability limits of swirling flames

Swirling flow systems are being used in many industrial processes like separation of particles in gas flows (cyclones), atomisation and spreading of liquids (water, oil) and fast mixing and high-intensity reaction in reactor systems as, e.g. stable and intense flames of swirl burners. The widespread use of swirl burners in the process and energy industries and, in particular, new concepts for the reduction of NO x-emissions (ultralean premixed combustion) raise the need for simple-to-use models for predicting lean stability limits of highly turbulent flames stabilized by internal recirculation. Based on recently published experimental data of the first author concerning the reaction structures of swirling flames operated near to the extinction limit, different methods for predicting lean blow-off limits have been developed and tested for different burner sizes and fuel gas compositions. The aim of the investigations was to find stabilization criteria that allow predictions of blow-off limits of highly turbulent recirculating flames without the requirement for expensive and time-consuming measurements in those flames. Several similarity criteria based on volumetric flowrates, burner size and material parameters of the cold gases, were found to be capable to predict stability limits of premixed and (in some cases) nonpremixed flames at varying swirl intensities, burner scales and fuel compositions. A previously developed numerical field model, combining a k,ε-model with a combined “assumed-shape Joint-PDF”/Eddy-Dissipation reaction model for the determination of the time mean reaction rates in turbulent flows was also tested for its potential for stability prediction. All the methods presented have specific advantages and limitations: the similarity criteria are restricted to geometrically similar systems, but they are easy to use, fairly precise and can take the detailled chemistry into account in an integral manner. The numerical field model necessitates large computational effort and is limited to very much simplified, global reaction mechanisms, but it offers the opportunity to make predictions for different burner geometries and swirl conditions.

Test of a premixing radiant burner for the low NOx combustion of natural gas/hydrogen mixtures

Abstract The subject of this work is the development and testing of premixing radiant burners operated either with natural gas or natural gas containing different hydrogen fractions. Emphasis is first placed on establishing a stable combustion process by varying the fuel gas composition, air ratio and burner load; furthermore, emissions should be as low as possible. With respect to flashback-free operation, it is important to define the limits of hydrogen addition for the burner concept developed.

Superequilibrium and thermal nitric oxide formation in turbulent diffusion flames

Measurements and modeling of the formation of superequilibrium radicals and nitric oxide in atmospheric pressure turbulent jet diffusion flames are presented which quantify the influence of superequilibrium on thermal NO x formation. Variation of fuel gas compositions (CO/H 2/N 2, CO/H 2/CO 2, and CO/H 2/Ar) permits partial separation of chemical and fluid mechanical effects. Superequilibrium OH radical concentrations are measured by single-pulse laser saturated fluorescence and NO and NO 2 concentrations by probe sampling and chemiluminescent detection. Four different types of probes were used to quantify probe sampling effects. In turbulent reaction zones, virtually all of the NO x in the flame occurred in the form of NO but far downstream of the flame nearly half of the NO x occurred as NO 2. Thermal NO x maximized near stoichiometric flame zones; the rich shift observed by others may be a probe sampling artifact. In turbulent CO/H 2/N 2 jet diffusion flames, both measurements and a nonequilibrium turbulent combustion model show that superequilibrium decreases average temperatures by 250K, increases average OH concentrations by a factor of 4–6, and increases thermal NO x formation principally by broadening the range of mixture fraction (both rich and lean) where thermal NO x is formed. Calculated increases in thermal NO x due to superequilibrium in turbulent CO/H 2/N 2 jet diffusion flames are factors of 2.5 at 1 atm and 1.4 at 10 atm. The two-scalar pdf model predicts that thermal NO x yield is independent of Reynolds number in disagreement with previous experimental reports.

Heat transfer in a coke oven

Equations describing heat transfer in a combustion flue were developed and incorporated into a coke oven simulation programme, The model can be used to predict the oven temperature history, and the evolution rate and composition of the volatile matter. Unlike other coking models, the present package does not require the temperature history of the heating wall to be specified. It is calculated by the combustion flue model. This significantly extends the number of applications which can be studied. The model has been implemented in a computer program which requires only basic data on the charge properties, fuel gas composition, and oven dimensions as input. The model was tested by comparing predicted temperature profiles with data from two industrial batteries. Good agreement was obtained in both cases.

The importance of fuel gas composition in the atomic-absorption spectrophotometric determination of magnesium

The specifications for commonly used “low temperature” fuel gases permit wide variations in composition. The effect, on the determination of magnesium in nickel, of using two samples of “propane” of differing compositions is considerable, and the use of acetylene is advocated. The results emphasise the need for a complete specification of flame conditions to be given when reporting sensitivities and interference susceptibilities in atomic-absorption procedures when using flame atomisation.