Boiler Flue Gas Research Articles

Effective installation for scrubbing ash from flue gases of small boilers

2. V. P. Belyakov, Cryogenic Technology and Techniques [in Russian], Energoizdat, Moscow (1982). 3. V. I. Kupriyanov, A. V. Isaev, and V. Mo Ermokhin, "A cryogenic sorption pump for evacuation of large chambers," Problems of Atomic Science and Technology. Ser. High-Vacuum Physics and Technology [in Russian], No. 8, KhFTI AN USSR, Khar'kov (1977), pp. 72-73. 4. A. M. Makarov, N. V. Filin, and L. A. Luneva, "Characteristics of diffusion streams of rarefied gas in a high-vacuum pipeline with surface separation or absorption of molecules," Trudy NPO Kriogenmash, No. 17 (1975), pp. 54-69. 5. N. N. Tarasov, N. V. Filin, and V. I. Kupriyanov, "Calculation of a vacuum system for long cryogenic pipelines," Problems of Atomic Science and Technology, Ser. High-Vacuum Physics and Technology [in Russian], No. 6, KhFTI AN USSR, Khar'kov (1976), pp. 53-56. 6. Inventor's Certificate 494,556 USSR. MKI FI6L 9/08. Cryogenic pipeline [in Russian]. 7. M. N. Rachitskaya, "Cryogenic-vacuum equipment," Khim. Neft. Mashinostr., No. i, 40-43 (1986).

Pilot plant experience in electron-beam treatment of iron-ore sintering flue gas and its application to coal boiler flue gas cleanup

The peresent development status of the electron-beam flue gas treatment process, which is a dry process capable of removing SOx and NOx simultaneously, is described. The most advanced demonstration of this process was accomplished with a pilot plant in Japan where the maximum gas flow rate of 10,000 Nm 3/h of an iron-ore sintering machine flue gas was successfully treated. The byproduct produced in this process is collected as a dry powder which is a mixture of ammonia sulfate and ammonium nitrate and is salable as a fertilizer or a fertilizer component. A preliminary economic projection showed that this process costs less than the lime scrubber which removes SOx but does not remove NOx. Tests using simulated coal combustion gases suggest that this process will be applicable to coal-fired boiler flue gas treatment as well. However, test on actual coal-fired flue gases are still required for commercial application decisions. A process development unit program consisting of the design, construction and testing of actual coal-fired power station flue gases is underway in the U.S.A. The design and engineering of the test plant is far advanced and the construction phase will be launched in the very near future.

Boiler Flue Gas Analysis and Automatic Combustion Air Trim Control by Measurement of Carbon Monoxide, Unburned Hydrocarbons, and Opacity

Regulation of combustion air flow is one of the most critical, yet commonly neglected elements of steamship economy. This paper describes the author's company's successful pioneering implementation of sophisticated electronic technology to that end, which has resulted in fleetwide fuel savings of 31/2 percent.

A Pilot Test of Simultaneous Removal of NOx and SOx from the Flue Gas of Coal-Fired Boiler

Simultaneous removal of NOx and SOx from the flue gas was performed under the gas feed rate from 50 to 80Nm3/hr using the slurry liquid of MgSO3-Mg (OH) 2-e (II) edta system in a column packed with “SAN” packing.It was shown that the removal ratio of NOx exceed 90% for liquid-gas ratio above 30kg-liquid/kg-gas. More than 99% of SO2 was removed. It was found that NOx removal ratio can be estimated by means of Porter's equation.As the results, deposition of solid particles in the apparatus does not occur when concentration of solid particles in the slurry liquid is in the range of 2-5%. Any increase in the initial concentration of MgSO3 or Fe (II)-edta increases NOx absorption capacity of the absorbing liquid.NOx absorption capacity of the liquid did not increased so much at O2 cocentration above 5% when the concentration of MgSO3 and Fe (II)-edta in the liquid were increased.

The influence of nitrogen on the oxidation resistance of low alloy steels

Experiments in simulated boiler flue gas have shown that the oxidation resistance of mild steel is increased by up to two orders of magnitude by a surface nitriding treatment. Oxidation resistance was determined under isothermal conditions and during cyclic changes of temperature and oxygen potential. The oxide scale has a fine grain size, is extremely adherent and is therefore protective. A nitrided surface layer is produced by gas-metal equilibration with NH 3 : H 2 gas mixtures under conditions to form austenite (y) at nitriding temperature. On cooling to room temperature, martensite (a') is formed with retained austenite, the relative proportions of which depend on cooling rate. During oxidation at 420 °C, martensite and austenite in the immediate surface layer temper within a few minutes to form ferrite (a) containing a fine dispersion of y'-Fe 4 N platelets ca . 50 nm in diameter. X-ray analysis at increasing depth from the surface of nitrided mild steel shows that tempering of the a' + y structure to a + y'-Fe 4 N is accelerated at the free surface of the alloy relative to the remainder of the nitrided layer, and results in formation of incoherent nitride precipitates on the surface. The nitride particles act as nucleation sites for oxide formation, and electron microscopy shows that the oxide nuclei are of the same order of size as the nitride particles.

The oxidation resistance of nitrided mild steel

The oxidation resistance of mild steel in a simulated boiler flue gas atmosphere has been shown in laboratory tests to be significantly enhanced by a surface nitriding treatment which forms a controllable fine-grained martensitic layer without precipitation of iron nitrides. A mechanism is suggested by which improved protection results from the refinement of oxide grain size and the condensation of cation vacancies in the nitrided layer instead of at the metal/oxide interface. A parallel is drawn with the development of improved oxidation resistance in superalloys by sub-surface dispersion of incoherent stable oxide particles.

Corrosion and Deposits From Combustion of Solid Waste—Part IV: Combined Firing of Refuse and Coal

Combined firing of processed municipal refuse with coal has been investigated in a stoker-fired boiler. The refuse preparation consisted of shredding, magnetic separation of metals, and air classification. The nature of the deposits and the extent of corrosion of simulated boiler tube surfaces was determined by inserting probes into the boiler. For amounts of refuse up to 35 percent on a heating value basis, the corrosion rate of carbon steels was reduced substantially below that found from previous measurements for refuse alone, and below that calculated on the basis of dilution by the coal. The temperature of the boiler flue gases also was found to be an important factor in corrosion. The emissions of sulfur oxides from high sulfur coal were reduced by the action of the alkaline components of the refuse.

Application of Electrostatic Precipitators for The Control of Fumes from Low Odor Pulp Mill Recovery Boilers

The cellulose pulping industry has long used electrostatic precipitators to collect soda ash entrained in recovery boiler flue gases. At a collection efficiency of 85 to 95%, the optimum economic situation is reached where capital outlay and operating expenses balance the value of the chemicals recovered over the life of the equipment. In recent years, however, stringent governmental regulation of particulate emissions has necessitated collection efficiencies above 99%. Although economic operation can not be achieved, traditional precipitator design is readily adaptable to these higher collection efficiencies. The pulp and paper industry in the United States has recently embarked upon a program to eliminate the emission of odorous gases from pulp mills. This involves q totally different operation of the kraft pulping liquor recovery process. Low odor operation of the recovery boiler results in a particulate emission with different physical properties than those produced by the traditional process. Electrostatic precipitators of the traditional design are incapable of handling this particulate emission. Fundamental changes in precipitator design and application are therefore necessary.

燃焼装置における窒素酸化物の発生と抑制対策 : ボイラにおける発生状況と排ガス循環二段燃焼による抑制法(エネルギ変換とその周辺問題小特集号)

燃焼装置における窒素酸化物の発生と抑制対策 : ボイラにおける発生状況と排ガス循環二段燃焼による抑制法(エネルギ変換とその周辺問題小特集号)

煙道ガスによる廃水処理および洗毛廃水の蒸発処理例

煙道ガスによる廃水処理および洗毛廃水の蒸発処理例

Recent Electrostatic Precipitator Experience with Ammonia Conditioning of Power Boiler Flue Gases

Motivated by heightened recent interest, Koppers Co. has been experimenting with ammonia conditioning of power boiler flue gases for the purpose of improving the precipitability of the emitted fly ash. Chemical reactions resulting from ammonia injection are postulated. Measurements on three pulverized coal and two cyclone fired boilers, all of which emit acidic ash, are described. In all five cases, considerable but varying, increase in precipitator power input and collection efficiency resulted when gaseous ammonia in the amount of 1 5 ppm was injected between the economizer and air preheater. The conditioned fly ash showed decreased acidity and inconsistent change in electrical resistivity. Unless air heater temperatures were unusually high (>400°F), tendency of the air heater to plug was an additional, but unwanted, result. At one station with high air heater outlet temperature ammonia injection has been adopted as a permanent solution to community pressure for reduction of stack discharge. Ammonia inj...

Oxidation of Sulphur Dioxide in Air at 950° C: Co-operative Influence of Carbon Monoxide and Nitric Oxide

THE oxidation of sulphur compounds in fuel to form sulphur dioxide, and the further oxidation of a small proportion of this to sulphur trioxide, give rise to problems of atmospheric pollution and of corrosion. The severe corrosion frequently experienced in those zones of boilers where the combustion products have become relatively cool is related to the sulphur trioxide of the flue gases, and the formation of sulphur trioxide in boilers has therefore been subjected to extensive investigations. The mechanisms generally held to be responsible for the production of the greater part of the sulphur trioxide detected in boiler flue gases are: (1) oxidation of sulphur dioxide by oxygen atoms in the flame; and (2) catalytic oxidation of sulphur dioxide at surfaces in the post-flame region.

Boiler Flue-Gas Measurements Using a Dewpoint Meter

Corrosion and fouling of low temperature heat-transfer equipment poses one of the major obstacles to the achievement of maximum boiler operating efficiency. The first consideration in controlling or eliminating a problem of this nature is determination of its causes. Dewpoint-meter investigations for this purpose were performed on units fired by coal, oil, and various fuel combinations. The context of this paper presents a review of those factors thus revealed by these investigations as major contributors to plugging and corrosion processes in air preheaters installed on oil-fired boilers. These tests disclosed that corrosion potential of boiler flue gases is directly effected by the degree of boiler slagging. They have established that flue gas corrosion potential can be substantially reduced by decreasing the level of excess air employed in operation. The results of this study also indicate that maximum rate of condensation (peak rate, or PR) and the temperature of its occurrence (peak rate temperature, or PRT) are more reliable indicators of corrosion potential than the dewpoint.

Closure to “Discussions of ‘The Formation of Sulphuric Acid in Boiler Flue Gases’” (1958, Trans. ASME, 80, pp. 232–233)

Closure to “Discussions of ‘The Formation of Sulphuric Acid in Boiler Flue Gases’” (1958, Trans. ASME, 80, pp. 232–233)

The Formation of Sulphuric Acid in Boiler Flue Gases

Abstract The discovery of the mechanism for the formation of sulphuric acid in flue gases of modern boiler plants by the process of surface catalysis, brought about by the heating surface over which the gases pass, was published some years ago. Notwithstanding the evidence put forward at that time, both from fundamental tests and operating plants, controversy on the question continues and little progress has been made in the suppression of this harmful product which is responsible for the deposit and corrosion on the boiler-plant surfaces and is, moreover, a very destructive and undesirable contaminant of the atmosphere. This paper describes further work on the subject, including tests which leave the explanation in no reasonable doubt and shows the effect on the sulphuric-acid formation of various surface treatments of the heating surface—both metallurgical and chemical.

Causes of Flue Gas Deposits and Corrosion in Modern Boiler Plants

This paper is intended to be an amplification and continuation of the author's previous paper entitled “Causes of High Dew-point Temperatures in Boiler Flue Gases” read before the Institution in 1943, in which attention was drawn to the phenomenon of the catalytic production of sulphuric acid in flue gases by their passage over heated iron surfaces. At that time the full importance of these findings was not apparent, but evidence is now submitted to show that, in addition to causing deposits and corrosion by the deposition of acid in air heaters and economizers, this phenomenon is primarily responsible for the flue-gas deposits and corrosion in all parts of boiler plants. Experiments are described which show that when flue gases are passed over sand-blasted steel-surfaces which are maintained at the gradation in metal temperatures which can occur through a modern boiler plant, sulphur trioxide is produced at the high temperature surfaces, causing sulphuric acid to condense on the cooler surfaces. When the maximum surface temperature is moderated no appreciable formation of acid occurs. It is believed that the interaction of the sulphur trioxide in the generation zone, and the condensed acid in the cooler zone, with the various constituents of the fuel ash and the metal of the heating surface, can explain all the numerous deposit and corrosion effects which have been the subject of research work both here and abroad during recent years. The high surface temperatures which are necessary for the catalytic action to occur are largely due to the general advances in operating temperatures and pressures, and in some measure to “surface combustion” taking place on the tube surfaces, elevating their temperature above that which they would acquire if swept only by inert gases. Although the advance in steam and water temperatures is considered to be a primary factor in these difficulties, many other contributory factors, particularly the nature of the fuel, play an important part. Pulverized-fuel boiler-plants are least affected and, at the present time, the adoption of pulverized fuel appears to be the most effective way of dealing with the problem. Further research is necessary to devise practical means of prevention or alleviation in stoker and oil-fired plants, and it is thought that full consideration of the factors outlined in the paper may materially assist in this object.

A method for the determination of small concentrations of so3 in the presence of larger concentrations of so2

AbstractThe sources of errors likely to arise in the estimation of minute quantities of SO3 in gases containing much larger quantities of SO2 are discussed with particular reference to boiler flue gases. A laboratory method is described whereby these difficulties in estimation may be eliminated, as demonstrated by the results obtained on a synthetic gas mixture of known SO2 and SO3 content.

Dust Precipitation from Boiler Flue Gases

Dust Precipitation from Boiler Flue Gases

Discussion in London on Bonded Deposits on Economizer Heating Surfaces and on Causes of High Dewpoint Temperatures in Boiler Flue Gases: At the Joint Meeting with the Institution of Electrical Engineers, 4th November 1943

Discussion in London on Bonded Deposits on Economizer Heating Surfaces and on Causes of High Dewpoint Temperatures in Boiler Flue Gases: At the Joint Meeting with the Institution of Electrical Engineers, 4th November 1943

Causes of High Dewpoint Temperatures in Boiler Flue Gases

High dewpoint temperature in flue gases in boiler plants causes premature condensation in the cooler gas passages resulting in deposits and corrosion. Evidence is submitted to show that high dewpoint can be caused by the increased temperature of the superheater tubes, the oxide film catalysing the conversion of the sulphur dioxide formed by combustion into sulphur trioxide, thereby increasing the sulphuric acid content of the gases. The trouble is confined chiefly to plants fired by mechanical stokers, pulverized fuel plants generally being unaffected. Coating the catalytic surfaces with lime or fine pulverized fuel ash prevents the action, and it is suggested that these materials sprayed on the tubes at intervals may prevent the formation of acid and its serious consequences.