Natural Gas Combustion Products Research Articles

Heat Recovery System with the Embedded Thermosiphon-Type Heat-Exchange Apparatus

It is proposed to use the heat-exchange apparatus whose surface was formed by two-phase siphons of a closed type for the system of deep recovery of the heat of escaping gases of the boiler with the steam capacity of 0.278 kg/s. To protect the gas escape channel from the damage the by-pass was arranged for the portion of combustion gases passing by the heat-exchange apparatus that allows us to raise the temperature of escaping gases above the dew-point temperature. Due to the fact that the heat-exchange apparatus uses the physical heat of gases and also the heat released during the condensation of water steam from the combustion products of natural gas its surface is subdivided in two stages that use different liquids as an intermediate heat carrier for the thermosiphons, in particular the stage without the steam condensation uses water and the stage with the steam condensation uses the water-ammonia mixture. This required some improvement of the known methods of heat calculation for the thermosiphon-type heat exchange apparatus. Computing studies were carried out using the software developed by the authors. The investigation allowed us to establish that in the case of maintenance of the fuel rate at a fixed level the heat recovery system allows us to provide the steam production at a capacity of 0.278 kg/s and also to additionally heat 0,5049 kg/s of the heating system water in the hot water supply system in the range of 10 °C to 65 °C and also to generate the condensate at a capacity of 0.0247 kg/s. The comparison of heat-exchange apparatuses of a thermosiphon type and coil type showed that their structures are comparable with regard to heat engineering and overall indicators.

Formation and Control of Sulfur Oxides in Sour Gas Oxy-Combustion: Prediction Using a Reactor Network Model

Sour natural gas currently requires expensive gas cleanup before it can be used in power generation because it contains large amounts of hydrogen sulfide (H2S) and carbon dioxide (CO2) that entail a low heating value and highly corrosive combustion products. A potential alternative is to use the gas directly in a gas turbine process employing oxy-fuel combustion, which could eliminate the need for gas cleanup while also enabling the application of carbon capture and sequestration, possibly combined with enhanced oil recovery (EOR). However, the exact influence of an oxy-fuel environment on the combustion products of sour gas has not been quantified yet. In this work, we used a reactor network model for the combustor and the gas turbine together with our recently assembled and validated detailed chemical reaction mechanism for sour gas combustion to investigate the influence of some basic design parameters on the combustion products of natural gas and sour gas in CO2 or H2O diluted oxy-fuel combustion as w...

Issues on Nitrogen Oxides Concentration Reduction in the Combustion Products of Natural Gas

The issues on nitrogen oxides formation during the fossil fuels combustion in the furnace-tube boiler have been considered, taking into consideration the national and foreign literature of recent years. Chemical reactions as well as mathematical models describing the emergence and further changes in the concentrations of thermal, fast NOх are proposed. The coefficient impact assessment of the furnace-tube boiler finning on the composition of gaseous fuels combustion products is provided.

Application of CHEMKIN and COMSOL Programs in the Calculations of Chemical Composition of Natural Gas Combustion Products

This article presents the results of numerical calculations of chemical composition of flue gas produced by combustion of natural gas in an industrial heating device, i.e., a pusher furnace. In calculations of combustion chemistry, the CHEMKIN-PRO program was used. The gas-dynamic of flue gas was modeled with the use of the COMSOL Multiphysics program. In order to check the correctness of the plug flow reactor (PFR) model, as applied in calculations, a preliminary laboratory experiment was conducted. Based on measurement data that were obtained during the research on a laboratory stand, the boundary conditions were formulated and numerical simulations were carried out. The temperature and velocity profiles in the combustion chamber were determined with the use of the COMSOL program and were implemented in the CHEMKIN program. The obtained results of the numerical simulations performed in the experimental chamber showed high compliance with the results of measurements. This, in turn, led us to apply the analysis on a real object. The simulations of the chemical composition of flue gas in the each zone of the furnace were carried out based on the measurements data collected from the real object, i.e., a pusher furnace that is currently working in one of the steel plants located in our country.

Sr+ + H2O ↔ SrOH+ + H equilibrium in flames with strontium admixtures

Sr+ + H2O ↔ SrOH+ + H equilibrium was studied spectrophotometrically. This reaction occurs in natural gas combustion products. Its enthalpy Δr H ○(0) = 61.4 ± 2.8 kJ/mol and bond energy D 0(Sr+-OH) = 432.6 ± 2.8 kJ/mol were determined using the third law of thermodynamics. The experimental data on this reaction obtained earlier in hydrogen flames, Δr H ○(0) = 55.3 ± 10.6 and D 0(Sr+-OH) = 438.7 ± 10.6 kJ/mol, were interpreted anew. The D 0(Sr+-OH) = 432.8 ± 2.7 kJ/mol value was eventually obtained.

Numerical Analysis of the Natural Gas Combustion Products

The combustion products of fuels containing the elements C, H, O, N and S are calculated. The methodology is based on the equations obtained in the stoichiometric balance of atoms. The adiabatic flame temperature is determined considering that the pressure of the boiler furnace remains constant. The scope of this work is limited to the analysis of natural gas (methane) with molecular formula CH4. The methodology can, however, be employed for the calculation of combustion products of a great variety of hydrocarbons under the established restrictions.In the development of the methodology two cases are contemplated: Φ ≤ 1 (lean and stoichiometric mixture) and Φ > 1 (rich mixture). In the first case it is considered that when the combustion is complete, the combustion products are O2, H2O, CO2, N2, SO2, and the solution follows directly. When the combustion is incomplete, however, the products H, O, N, H2, OH, CO, NO, O2, H2O, CO2, N2 and SO2 can be generated, according to Stephen R. Turns, (2000). When bal-ances of atoms are performed, four conservation equations are obtained, one for each of the C, O, H and N elements. An additional restriction requires that the sum of the molar fractions of the products equals one mol. Finally, seven equilibrium constants, corresponding to the seven chemical reactions of combustion, are introduced. All this provides a system of four nonlinear equations which is solved with the Newton-Raphson method.

Influence of water vapour on high temperature oxidation of steels used in petroleum refinery heaters

The oxidation behaviours of three different steels used in the construction of petroleum refinery heaters were investigated by thermogravimetric analysis (TGA) technique. C-5, P-11 and P-22 steel samples were tested in two different environments: air and CO2 + 2H2O + 7.52N2, a gas composition which simulates the combustion products of natural gas, at 450 and 500 °C. P-22 steel had the best oxidation resistance at both temperatures in air. In CO2 + 2H2O + 7.52N2 environment, the oxidations of all the steels were accelerated and C-5 exhibited better oxidation resistance than P-22 and P-11. Analyses of oxidation products by optical microscopy, SEM-EDX and XRD were carried out to correlate TGA results to oxide composition and morphology. The lower oxidation rate of P-22 in air was explained with reference to the formation of a protective Cr-containing oxide layer between the steel and the iron oxide scale. The higher oxidation rates of chromium containing steels in CO2 + 2H2O + 7.52N2 environment were attributed to the depletion of protective Cr-containing oxide scale, which was deduced from the lower Cr content of this layer than that formed in air oxidation, as a result of probably faster oxidation of Cr even inside the steel. Therefore, the oxidation mechanisms of FeCr alloys with intermediate Cr contents at higher temperatures could also be valid for steels with low chromium contents such as P-22 (2.25%) even at 450 and 500 °C.

Analysis of aluminum plates under heating in electrical and natural gas furnaces

This paper analyzes the thermal storage characteristics of aluminum plates in furnaces during their heating for lamination under two sources of heat: an electrical resistance bank and a combustion process carried out with natural gas. The set of equations to model the furnace under operation with electrical energy, for air as the fluid, is presented. This supports the theoretical analysis for the system under operation with natural gas combustion products. A numerical procedure, using the software ANSYS, is applied to determine the convection heat transfer coefficients for heating by the air flow. Temperatures measured in a plate inside a real furnace are used as parameters to determine these coefficients. Then convection and radiation heat transfer coefficients are determined for the natural gas combustion products. Results are compared, indicating a possible gain of 5.5 h in relation to a 19.5 h period of conventional electrical heating per plate.

Reliability of a Conceptual Ceramic Gas Turbine Component Subjected to Static and Transient Thermomechanical Loading

A three year program to evaluate the feasibility of using monolithic silicon nitride ceramic components in gas turbines was conducted. The use of ceramic materials may enable design of turbine components which operate at higher gas temperatures and/or require less cooling air than their metal counterparts. The feasibility evaluation consisted of the following three tasks: (1) expand the materials properties database for candidate silicon nitride materials; (2) demonstrate the ability to predict ceramic reliability and life using a conceptual component model; and (3) evaluate the effect of proof testing on conceptual component reliability. The overall feasibility goal was to determine whether established life and reliability targets could be satisfied for the conceptual ceramic component having properties of an available material. Fast and delayed fracture reliability models were developed and validated via thermal shock and tensile experiments. A creep model was developed using tensile creep data. The effect of oxidation was empirically evaluated using four-point flexure samples exposed to flowing natural gas combustion products. The reliability and life-limiting failure mechanisms were characterized in terms of temperatures, stress, and probability of component failure. Conservative limits for design of silicon nitride gas turbine components were established.

Occupational risk factors for bladder cancer: results from a case-control study in Montreal, Quebec, Canada.

A population-based case-control study of the associations between various cancers and occupational exposures was carried out in Montreal, Quebec, Canada. Between 1979 and 1986, 484 persons with pathologically confirmed cases of bladder cancer and 1,879 controls with cancers at other sites were interviewed, as was a series of 533 population controls. The job histories of these subjects were evaluated by a team of chemist/hygienists for evidence of exposure to a list of 294 workplace chemicals, and information on relevant non-occupational confounders was obtained. On the basis of results of preliminary analyses and literature review, 19 occupations, 11 industries, and 23 substances were selected for in-depth multivariate analysis. Logistic regression analyses were carried out to estimate the odds ratio between each of these occupational circumstances and bladder cancer. There was weak evidence that the following substances may be risk factors for bladder cancer: natural gas combustion products, aromatic amines, cadmium compounds, photographic products, acrylic fibers, polyethylene, titanium dioxide, and chlorine. Among the substances evaluated which showed no evidence of an association were benzo(a)pyrene, leather dust, and formaldehyde. Several occupations and industries were associated with bladder cancer, including motor vehicle drivers and textile dyers.

IGR Solid-State Electrochemical NOx Control for Natural Gas Combustion Exhaust Gases

Solid-state electrochemical technology, embodied in the IGR process, is used to reduce nitrogen oxides (NOx) to nitrogen and oxygen, and thereby control NOx emissions from natural gas powered engines. The IGR deNOx process is based on solid-state, flow-through, high surface area, porous oxygen ion conductive ceramic electrolytes. Recent bench-scale experiments conducted for the Gas Research Institute have demonstrated NOx reduction in multicomponent gas streams, the inert portion of which simulate natural gas combustion products. The reduction products were analyzed by in situ gas chromatography to verify NOx reduction rates inferred from electrochemical measurements. IGR process advantages compared with existing NOx control technologies are reviewed.

Determination of aldehydes and ketones in natural gas combustion in the ppb range by high-performance liquid chromatography

The reported identification and determination of trace compounds in flue products of natural gas burning equipment is based on DNPH precolumn derivatization and followed by HPLC separation. The optimized HPLC analysis has been applied to the determination of trace amounts of aldehydes and ketones in polluted air such as lab and ambient air as well as natural gas and oil combustion products in a hospital. The results obtained in a hospital show that the oil fuel combustion process emits a considerable amount of toxic acrolein, whereas the emission of acetone is predominant in natural gas combustion.

Associations between several sites of cancer and ten types of exhaust and combustion products. Results from a case-referent study in Montreal.

A population-based case-referent study provided information on the associations between several types of cancer and 10 types of exhaust and combustion products. All site-exposure combinations were investigated. An increased lung cancer risk, in particular squamous-cell cancers, due to exposure to gasoline and diesel exhausts was found. Among the associations that have not been subject to previous attention, the most promising leads for further investigation are the possible relations between gasoline and diesel exhaust and colorectal cancers, gasoline exhaust and kidney cancer, coal combustion products and pancreatic cancer (and possibly nonadenocarcinoma lung cancer), combustion products of heating oil and prostatic cancer, and natural-gas combustion products and bladder cancer.

Combustion of finned steel tubing during stress relief heat treatment

An investigation has been made of two fires which occurred when finned plain carbon steel boiler tubes were being stress relieved at a nominal temperature of 1150° F (621° C). The furnace atmosphere consisted of the combustion products of natural gas with about 330% excess air. In both cases the furnace was being operated with one of the twenty-four burners out. This resulted in increased gas flow to the other three burners on the same manifold, and thus to local temperatures above 1150° F (620° C) near them. Both fires started at one of these regions of elevated temperature. Metallographic evidence indicates that repeated spolling of the scale occurred at the tips of the fins. The heat generated by the rapid oxidation of the bare metal exposed by this process led to a rise in temperature. This accelerated the spoiling, which in turn led to a further increase in temperature. Thus, the spoiling and subsequent oxidation resulted in an uncontrollable rise in temperature. When the temperature reached 2500° F (1371° C), iron and iron oxide (wustite) reacted to form an eutectic liquid. As this ran off the steel surface under gravity, bare metal was continuously exposed. This led to an even higher oxidation rate. Eventually,the ignition temperature for the steel was reached.

Resistance to Oxidation at Elevated Temperatures of a Number of Alloy Steels

A wide range of steels, extending from a plain carbon steel to high chromium-nickel, austenitic types and some nickel-based alloys, have been subjected to a cyclic oxidation test in natural gas combustion products at various temperatures. Resistance to oxidation can be expressed in terms of a breakdown temperature which provides a convenient parameter by means of which the behaviour of steels and alloys may be compared. On this basis, the beneficial effects of additions of chromium of up to 30% are confirmed, as are additions of silicon and/or aluminium to chromium steels. Cobalt, copper, molybdenum, vanadium, tungsten, niobium, titanium and nitrogen have comparatively little effect. Manganese appears to be detrimental when added to chromium steels and carbon can be in some circumstances. Nickel can enhance oxidation resistance in some circumstances but is detrimental in others. The presence of sulphur in free-machining, stainless steels appears to counteract the effect of a higher-thannormal manganese content.

Experimental investigation of cathode spots on metallic electrodes protruding in plasma flow

The behavior of cathode spots on metallic electrodes is investigated. The dependence of the basic characteristics of the spots (current per spot, life time, rate of displacement, average area and so forth) on the nature of the flow of the plasma past the surface of the electrode, the surface temperature of the electrode, the total current in the electrode, and the magnetic field is obtained. The investigations were done in connection with the study of the operation of electrodes of open cycle magnetohydrodynamic generators. The experiments were conducted with copper electrodes introduced in the plasma formed by the combustion products of natural gas with potassium added to it.

Evaporation constants for drops of water and ethyl alcohol in natural gas combustion products and in heated air

A formula is obtained for computing the evaporation constants for water and ethyl alcohol in high-temperature gaseous media. The computed evaporation constants are compared with experimental values.

The effect of combustion products of natural gas on the quality of enamel coating

The effect of combustion products of natural gas on the quality of enamel coating

Some data obtained with an experimental MHD-power plant

In the report a brief account is given of a large experimental complex MHD-power plant for open-cycle operation with combustion products of natural gas. The main distinguishing feature of such a plant in comparison with existing ones consists in the fact that with its help it is possible to investigate not only the MHD-generator itself but also other complicated components of MHD-power plants as well as to investigate the operation of major components of the MHD-power plant. Presumably the question as to the prospective application of open-cycle MHD-power plants for large-scale power generation can be answered only after the solution of complicated research and engineering problems associated with the development of a large-scale commercial pilot plant. Another distinguishing feature of the described plant lies in the fact that it is intended for a long-period service. The report gives main parameters of the plant, describes the technological scheme and its major components: the combustion chamber, the MHD-channel, the magnet system, facilities for injection and recovery of ionizing seeding, high-temperature air preheaters, end heat-exchanger systems, current inverting systems, etc. Also the report gives a summary of the obtained experimental results. The MHD-generator output power amounted to 30 kW. The comparison of the results on thermal and gasdynamic investigation carried out in the MHD-channel with theoretical calculations made on a refined one-dimensional flow model showed that they agree After the investigations carried out on the described plant conditions were obtained not only for further wide-scale magnetohydrodynamic thermophysical and electrophysical investigations of MHD-power plants but also for the continuation of the work for investigating a simultaneous operation of the MHD-generator with other components of the plant as well as for developing more rational designs of the components and conditions for their operation.