Combustion hydrocarbon gases

Generally, two types of detectors are used to monitor gas compositions a thermal conductivity detector (TCD) for common permanent gases like O2, N2, CO2, He, Ar, etc., or a flame ionization detecdor (FID) for common combustible hydrocarbon gases/vapors such as C H2 , 2, H2,. and all sorts of volatile organic compounds. 

The combustion of gas produces little in the way of noxious substances. Ideal combustion will produce only water vapor, carbon dioxide and nitrogen. In practice, there may well be very small amounts of hydrogen, carbon monoxide and unburned hydrocarbons, notably methane. 

CNTs can also be produced by diffusion flame synthesis, electrolysis, use of solar energy, heat treatment of a polymer, and low temperature solid pyrolysis. In flame synthesis, combustion of a portion of the hydrocarbon gas provides the elevated temperature required, with the remaining fuel conveniently serving as the required hydrocarbon reagent. Hence, the flame constitutes an efficient source of both energy and hydrocarbon raw material. Combustion synthesis has been shown to be scalable for a high volume commercial production. 

Combustion of gas takes place in two ways, depending upon when gas and air are mixed. When gas and air are mixed before ignition, as in a Bunsen burner, burning proceeds by hydroxylation. The hydrocarbons and oxygen form hydroxylated compounds that become aldehydes the addition of heat and additional oxygen breaks down the aldehydes to H2, CO, CO2, and H2O. Inasmuch as carbon is converted to aldehydes in the initial stages of mixing, no soot can be developed even if the flame is quenched. 

Manson Ferrie (Ref 6) investigated explosive mixtures consisting of combustible hydrocarbons such as C2H2, and natural gas with oxygen as oxidizer. 

Catalytic combustion for gas turbines has received much attention in recent years in view of its unique capability of simultaneous control of NOX) CO, and unbumed hydrocarbon emissions.1 One of the major challenges to be faced in the development of industrial devices is associated with the severe requirements on catalytic materials posed by extreme operating conditions of gas turbine combustors. The catalytic combustor has to ignite the mixture of fuel (typically natural gas) and air at low temperature, preferably at the compressor outlet temperature (about 350 °C), guarantee complete combustion in few milliseconds, and withstand strong thermal stresses arising from long-term operation at temperatures above 1000°C and rapid temperature transients. 

Industrial analysis of hydrocarbon gases 25 years ago was limited almost to Orsat-type absorptions and combustion, resulting in crude approximations and inadequate qualitative information. The more precise method of Shepherd (56) was available but too tedious for frequent use. A great aid to the commercial development of hydrocarbon gas processes of separation and synthesis was the development and commercialization of high efficiency analytical gas distillation units by Podbielniak (50). In these the gaseous sample is liquefied by refrigeration, distilled through an efficient vertical packed column, the distillation fractions collected as gas and determined manometrically at constant volume. The operation was performed initially in manually operated units, more recently in substantially automatic assemblies. 

Partial oxidation processes rank next to steam-hydrocarbon processes in the amount of hydrogen made. They can use natural gas, refinery gas, or other hydrocarbon gas mixtures as feedstocks, but their chief advantage is that they can also accept liquid hydrocarbon feedstocks such as gas oil, diesel oil, and even heavy fuel oil. All processes employ noncatalytic partial combustion of the hydrocarbon feed with oxygen in the presence of steam in a combustion chamber at flame temperatures between 1300 and 1500°C. For example, with methane as the principal component of the feedstock ... 

On the other hand, when the fuel and air are not well mixed (such as when a pure hydrocarbon gas is burned as it emerges from a stack and mixes with atmospheric air), the combustion proceeds relatively slowly, and some of the hydrocarbon fuel decomposes to form elementary carbon and hydrogen before oxidation takes place. The heat of reaction is sufficient to raise the temperature to a point where the carbon particles glow incandescently. A yellow flame is the result. 

Natural gas, also known in its crude form, as marsh gas and fire-damp, consists mainly of methane (CH4). Other gases are present in various proportions, the most important being ethane, propane and butane. Natural gas is an important fuel since it contains about 95% combustible hydrocarbons. This gas is used in many glassblowers workshops in America. Since it is relatively cheap and efficient, its future utilization in other countries is probable. 

Natural gas is the gaseous mixture associated with petroleum reservoirs and is predominantly methane but does contain other combustible hydrocarbon compounds as well as non-hydrocarbon compounds (Table 2.3 Speight, 1999). In fact, associated natural gas is believed to be the most economical form of ethane. 

Catalytic combustion for gas turbines is an important tool for lowering NO emissions from gas turbines. Multistage catalytic reactors for gas turbines have shown ultralow emissions, namely 0.5 ppm NO.v, 0.8 ppm CO, and 1.7 ppm un-bumed hydrocarbons from natural gas fuel [145]. 

Table XXI.—Composition of Air-Hydrocarbon Gas Mixtures to Give Maximum Flame Temperatures, Maximum Speeds of Uniform Movement of Flame, and Complete Combustion. ...

Cylinders of the flashed gas were analysed for hydrocarbon gas composition on a Carle gas chromatograph (GC) system equipped with both a thermal conductivity detector (TCD) and a flame ionization detector (FID). An offline preparation system and dual inlet mass spectrometer (MS) were used to analyse the carbon and hydrogen isotopic values of hydrocarbon components. A customized Gow Mac GC was interfaced with a vacuum/combustion system to separate hydrocarbons from other components and combust to CO2 and water that were purified and sealed into Pyrex tubes for isotopic analysis. The CO2 was analysed directly on one of three dual inlet mass spectrometers Finnigan Delta S, Finnigan Delta + XL or VG SIRA II. The water was reacted with zinc turnings and converted to hydrogen gas, which was analysed on either the Delta S or Delta + XL MS. 

The power washed TPO parts pass under a robotic oxygenated butane or propane flame arm . The oxidizing flames (flame plasma) change the chemical make up of the TPO surface. The basis for this change is a working knowledge of the combustion reaction of the hydrocarbon gas defined as ... 

In an ideal combustion of fuel purely based on stoichiometric conversion, fuel is burnt to CO2 and H2O 100% with 0% excess air so that there is no oxygen left in the combustion flue gas. However, in reahty, industrial fired heaters require excess air. To achieve complete combustion, a minimum of 10-15% excess air (2—3% O2 in flue gas) is required for fuel gas. Otherwise, carbon monoxide and unbumed hydrocarbon could appear in the flue gas leaving stack. Fuel oil usually requires 5-10% higher excess air than fuel gas. In other words, a minimum of 15-25% excess air (3-5% O2) is required for fuel oil for complete combustion. 

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