Combustion methods

The in situ combustion method of enhanced oil recovery through air injection (28,273,274) is a chemically complex process. There are three types of in situ combustion dry, reverse, and wet. In the first, air injection results in ignition of cmde oil and continued air injection moves the combustion front toward production wells. Temperatures can reach 300—650°C. Ahead of the combustion front is a 90—180°C steam 2one, the temperature of which depends on pressure in the oil reservoir. Zones of hot water, hydrocarbon gases, and finally oil propagate ahead of the steam 2one to the production well. 

The side-chain chlorine contents of benzyl chloride, benzal chloride, and benzotrichlorides are determined by hydrolysis with methanolic sodium hydroxide followed by titration with silver nitrate. Total chlorine determination, including ring chlorine, is made by standard combustion methods (55). Several procedures for the gas chromatographic analysis of chlorotoluene mixtures have been described (56,57). Proton and nuclear magnetic resonance shifts, characteristic iafrared absorption bands, and principal mass spectral peaks have been summarized including sources of reference spectra (58). Procedures for measuring trace benzyl chloride ia air (59) and ia water (60) have been described. 

P. Kesselting, Catalytic Combustion, ia F. Weiaberg, ed.. Advanced Combustion Methods, Academic Press, Inc., New York, 1986. 

Natural gas - Determination of sulfur compounds. Determination of hydrogen sulfide, mercaptan sulfur, and carbonyl sulfide sulfur by potentiometry. Also BS 3156 Subsection 11.4.3 1994 Natural gas - Determination of sulfur compounds. Lmgener combustion method. Also BS 3156 Subsection 11.4.5 1994... 

In many regions of the world coal reserves represent substantial indigenous resources, and for this reason coal will always play an important role in the future of power generation. Inevitably, coal is more difficult to handle and has less appeal than other clean-burning fuels such as gas. However, substantial progress has been made in modern efficient handling techniques and combustion methods that can give clean combustion with low emissions. 

Boilers may be direct fired or indirect fired. Energy supply designs account for various combustion methods using fossil fuels, municipal waste, process residues, waste heat, and by-products. Special boiler combustion systems to reduce pollution or improve efficiency include fluidized-bed and combined cycle. 

The in situ combustion method of enhanced oil recovery through air injection (397,503,504) is an exceeding complex process chemically. However, because little work has been done on the effect of chemical additives to oil recovery efficiency, this process will not be discussed herein. 

This is a relatively recent area of research and development. It has come about because of various reasons unsightly plastic articles, over-flowing landfill sites, enhancing humus in soils thus avoiding combustion methods that may generate toxic vapours, etc. 

Julien, C., Letranchant, C., Lemal, M., Ziolkiewicz, S., Castro-Garcia, S., Layered LiNio 5Coo 502 compounds synthesized by a glycine-assisted combustion method for lithium batteries, J. Mater. Sci. 37,2367-2375 (2002). 

While there have been very few intercalibration studies done between the various kinds of methods, the few available comparisons suggest that both the ultraviolet irradiation method and the various total combustion methods... 

Initially, results reported for dry-combustion methods were found to be higher than wet-oxidation methods based on persulfate by factors of 2 or more. This discrepancy has steadily decreased as methodologies have improved. Contamination problems of dry methods have been reduced and the oxidation efficiency of the wet methods has been improved. While the differences between approaches have been discussed [94,95], there is still uncertainty whether the remaining difference between the two techniques is real - a result of incomplete oxidation, incorrect estimation of blanks, or a combination of both. 

Collins and Williams [30] have recently described a modification of Ehr-hardt s earlier photochemical method [57], which offers the practical advantages of speed, convenience, and the potential for real-time analyses. However, until the accuracy of the results is established, the method will not receive general acceptance. Collins and Williams [30] examined the completeness of oxidation of their photo-oxidation system using three independent methods, but pointed out that while essentially complete oxidation was indicated, definitive proof was lacking. A more satisfactory solution to the problem might be found through comparison of results of the photo-oxidation method with the dry-combustion method, which most analysts are willing to accept as complete [96]. 

The various combustion methods differ primarily in the method of measuring the carbon dioxide generated from the organic carbon. The first really sensitive carbon dioxide detector and the one still most used is the non-dispersive infrared gas analyser. The detecting element senses the difference in absorption of infrared energy between a standard cell filled with a gas with no absorption in the infrared, and a sample cell. Water vapour is the only serious interference, hence the carbon dioxide must be dried before any measurements are made. 

An alternative method for the determination of particulate organic carbon in marine sediments is based on oxidation with potassium persulfate followed by measurement of carbon dioxide by a Carlo Erba non-dispersive infrared analyser [152,153]. This procedure has been applied to estuarine and high-carbonate oceanic sediments, and results compared with those obtained by a high-temperature combustion method. 

As for all of the fractions of organic material in seawater, the volatile organic carbon fraction is defined by the method by which it is collected. In one of the earliest estimates, Skopintsev [93] defined the volatile fraction as the difference between total organic carbon values, as measured by evaporation and dry combustion, when the evaporations were carried out at room temperature and at 60 °C. Thus Skopintsev s volatile fraction consists of those compounds that are volatile from acidified solution taken to dryness at 60 °C but not at 20 °C. This fraction was found to be between 10 and 15% of the total organic carbon. He also noted a 15% difference in measured organic carbon with his dry combustion method when samples were dried at different temperatures and concluded that this difference was due to the loss of volatiles. 

At the USDA Forest Service, Forest Products Laboratory (FPL), Brenden and Chamberlain (6) examined the feasibility of measuring heat release rate from an ASTM E-119 furnace. Three methods of measuring heat release were considered the substitution method, oxygen consumption method, and weight of material/heat of combustion method. The oxygen consumption method was shown to be the most advantageous way to measure heat release. However, data were limited to a few assemblies. Chamberlain... 

Spectrophotometry X-ray diffraction Combustion methods Wet digestion methods Miscellaneous... 

Combustion methods have been used to determine total sulphur and total organic carbon and total halides in soil, total and particulate organic carbon, total halide, phosphorus and nitrogen, total and particulate organic carbon in saline sediments and total nitrogen in sludges. 

Carbon in soil and plant materials can be determined by wet- and dry-combustion methods [7, 8]. In both instances, soil and plant carbon is converted into carbon dioxide, absorbed in alkali and determined either by titration against a standard acid or by weighing. These methods involve large apparatus, are expensive and time consuming, and therefore cannot be adapted to the routine analysis of a large number of samples. 

Organic carbon can be determined in calcareous soils after the carbonates have been removed by treatment with sulphuric acid-iron(II) sulphate solution and the samples oven-dried at 105°C. However, as in all other wet-combustion methods, chloride ions interfere [7]. Interference from small amounts of chloride ions (up to 4mg of Ch as KC1 or NaCl) was reduced by adding 2.5% of mercury II oxide or silver I sulphate to the acid digestion mixture. 

Good agreement was obtained between this wet combustion method [9] and a method based on dry combustion [17] (Table 12.5). 

---