Furnace Flue Research Articles

Speciation of chromium in steelmaking solid wastes by selective retention on ion-exchange media and determination by isotope dilution inductively coupled plasma mass spectrometry

The separation and determination of CrVI and CrIII were carried out by using a combination of ion-exchange resins and inductively coupled plasma mass spectrometry (ICP-MS). Once in solution the species were retained on Dowex 1-X8 and Dowex 50W-X8 resins, for CrVI and CrIII, respectively. Following elution of the CrVI with HNO3 and of the CrIII with HCl, and after elimination of chloride ions, chromium contents were determined by ICP-MS. The sample dissolution and preparation method was developed using CrO3 (CrVI) and Cr2O3 (CrIII) mixtures. A general method was established, consisting in the leaching of the soluble chromium species (CrVI and any soluble CrIII compound) with a NaOH–Na2CO3 solution, and in digesting the residue (insoluble CrIII compounds and Cr metal) by fusion with NaHSO4 and extracting the melt with HCl. The obtained solutions were submitted to the ion-exchange speciation processes. The scope of the method was investigated by analysing two electric arc furnace flue dust samples: MS-2 (carbon steel flue dust) and MS-3 (stainless-steel flue dust). The determination limits (10s), considering test samples of 10 mg, were 0.1 µg g−1 for both CrVI and CrIII. Validation of the proposed method was carried out by analysis of BCR CRM 544 and by standard additions of CRM 544 to CrO3–Cr2O3 mixtures; recoveries of both chromium species (CrVI and CrIII) close to 100%, with precision values better than 3%, were achieved. External calibration and isotope dilution (ID) were applied for ICP-MS measurements; the latter system (ID) was developed for application to Cr measurements in steelmaking solid wastes, to overcome any possible interference from the complex sample matrix.

Differentiation of polychlorinated dibenzo‐p‐dioxin and dibenzofuran sources in coastal British Columbia, Canada

AbstractMultivariate pattern analysis techniques, principal components analysis, and polytopic vector analysis (PVA) were used to apportion sources of dioxins and furans to Howe Sound and the lower Strait of Georgia marine ecosystem, British Columbia, Canada, based on deposition in recent sediments. In sediment cores collected in 1990, differences between congeners in the depth of maximum concentration suggested the influence over time of several different sources. Those with a predominance of hexachlorinated dibenzodioxins and 2,3,7,8‐tetrachlorodibenzofuran comprised one of the major contributions to the sediment core samples and surficial samples collected from Howe Sound, consistent with past inputs of pulpmill effluent. For most sediment samples, however, over 50% of the composition was attributable to a separate source with octachlorodibenzo‐p‐dioxin (OCDD) as the dominant congener, followed by heptachlorodibenzo‐p‐dioxins with small amounts of heptachlorodibenzofuran and octachlorodibenzofuran (OCDF). This source signature is consistent with the composition of dioxins/furans in formulations of pentachlorophenol‐based wood preservatives, which were used extensively in British Columbia, Canada prior to the mid‐1980s. This major input signature to the greater Strait of Georgia cannot be unequivocally ascribed to PCP use and disposal, however, since several other dioxin/furan sources also exhibit a highly similar composition, one dominated by OCDD. For example, source signatures similar to PCP formulations include those from diesel emissions, coal combustion, municipal solid waste, or other incineration stack emissions (fly ash, in particular), chimney soot from oil central heating, black‐liquor recovery furnace flue gas, and scrap wire and car incineration. Further research is required to discriminate among the OCDD‐containing sources and, hence, provide for improved future source management.

Zinc recovery from blast furnace flue dust

Blast furnace flue dusts are a mixture of oxides expelled from the top of the blast furnace, whose major components are iron oxides. They also contain zinc, silicon, magnesium and other minor element oxides in lesser amounts. The direct recycling of flue dust is not usually possible since it contains some undesirable elements (zinc and alkaline metals) that can cause operational difficulties in the blast furnace. Furthermore, in some cases the dust contains toxic elements (zinc, cadmium, chromium and arsenic) that make it hazardous and unacceptable for landfill. The fact that it is not possible to recycle this dust directly or to reject it as landfill, makes it necessary to consider the recovery of the valuable elements contained in it and to obtain a non-hazardous residue that can be stored without problem or can be used in agglomeration units in iron-making industries. To reach this objective a sequence of unit operations which consists of leaching, filtration, purification, extraction, stripping and electrolysis processes is required. In this research a blast furnace flue dust which principally consists of iron, with some zinc and other elements oxides has been examined. The preliminary results show that it is possible to leach selectively the valuable elements of the dust by sulphuric acid at low acid concentration and room temperature, giving high recovery using zinc (about 80%). The pregnant solution obtained is subjected to purification and extraction for eliminating its contaminants, and increasing its zinc concentration before electrowinning the zinc.

97/02257 Utilization of waste heat of metallurgical furnace flue gas

97/02257 Utilization of waste heat of metallurgical furnace flue gas

Furnace Flue Gas Modelling and Simulation

A furnace flue gas model is developed based on furnace mass and energy balances and fuel combustion chemistry. The model describes the furnace fuel combustion dynamics under different conditions. A knowledge base is used in the modelling since process variables are very dependent on the furnace fuel combustion process and existing modelling methods cannot deal with this properly. Using the furnace model developed, a close study of the effect of furnace temperature and air on fuel combustion and boiler flue gas emission can be realised.

Application of scanning electron microscopy for pollution particle source determination in residential dust and soil

AbstractMany tons of electric furnace flue dust accumulated in an industrial area in Tifton, Georgia. Vehicles transporting the flue dust, classified as K061 hazardous waste because it contained lead and cadmium, initially dumped the material in a warehouse. Once the warehouse was full, the flue dust was dumped in uncovered piles. Run‐off from the piles and wind‐driven particles had the opportunity to contaminate nearby industries, residential buildings, and neighborhood soils over a period of many years. Scanning electron microscopy‐energy dispersive x‐ray spectrometry (SEM‐EDS) was used to compare the morphology and chemical composition of fly ash dust from the suspect pile with samples collected from the surrounding buildings and soil. Adhesive samplers were used to collect dust that had accumulated in buildings surrounding the fly ash dump site. Suspect dust particles were analyzed by SEM‐EDS and compared with known dust particles from the fly ash pile. Soil samples were dried, sieved, and the “fines” analyzed by SEM‐EDS for comparison with samples from the fly ash pile. Fly ash particles similar in morphology and chemical composition to the fly ash in the suspect pile were identified in most of the buildings sampled surrounding the fly ash dump site and in all of the soil samples analyzed surrounding the dumpsite. This case study illustrates the usefulness of applying morphology and chemistry information acquired by SEM‐EDS for pollution particle source determination.

Analysis of electrical arc furnace flue dusts by spark ablation inductively coupled plasma atomic emission spectrometry

A medium-voltage spark was used for the direct nebulization of electric arc furnace (EAF) flue dust. In order to attain the necessary sample conductivity, powder pellets are briquetted after mixing the sample 1 + 1 with graphite. The elutriated material was excited in an argon inductively coupled plasma (ICP). The use of cellulose as binder provides better results in terms of reproducibility. After optimization of the spark parameters (voltage, 500 V; repetition rate, 400 s–1; and resistance, 2.2 Ω), the carrier gas flow rate (2.1 l min–1 of argon) and the operating power of the ICP (1.2 kW), precisions (relative standard deviation) for zinc, lead, cadmium and iron range from 0.8 to 2.0%. The stability of the spark sampling, during a complete spark ablation (SA) ICP process (≈90 s) was tested by plotting emission intensity versus time profiles. The similarity between the amounts of analyte obtained from different pellets was proven by collecting the spark-eroded particles and analysing their carbon contents. Five steelmaking EAF flue dusts were selected for this study, using the two samples with extreme contents of the elements considered, for calibration. The results obtained by SA-ICP matched the results obtained by ICP from nebulized solutions.

X‐ray photoelectron spectroscopic (XPS) study of DeNOx catalysts after exposure to slag tap furnace flue gas

AbstractX‐ray photoelectron spectroscopy has been used to investigate the composition of both the surface of DeNOx catalysts (Ti:Mo:V = 92:6:2 and Ti:W:V = 85:10:5 at.%) and the material deposited from the flue gas. In spite of the charging of the surface in the spectrometer, it was possible to perform both qualitative and quantitative analysis. The deposits primarily contain Ca, Si, O, S, As, P and N. Oxidation numbers of Ca, Si, Ti, Mo, W, S and N were determined from chemical shifts in combination with line widths. There are, however, problems with the determination of the oxidation state of As owing to an influence of the exciting Al Kα radiation on the oxidation state. Nevertheless, As seems to exist both as As3+ and As5+.

Electric arc furnace flue dusts: characterization and leaching with sulphuric acid

Two electric arc furnace flue dusts, principally iron oxides, containing zinc, lead, cadmium, chromium and other elements in a lesser amount were examined. The non-ferrous metals make these materials hazardous wastes. The direct recycling of the dusts is not possible, which makes it necessary to look for a process to beneficiate these materials to generate a non-hazardous residue that can be used as landfill. This paper contains an electric arc furnace (EAF) flue dusts characterization and a systematic study of sulphuric acid leaching to obtain the reaction rates of dissolution. Results show that it is possible to beneficiate the dusts by leaching the non-magnetic fraction with sulphuric acid at low acid concentration and room temperature, giving high recoveries of Zn (≈ 80%), recycling of the magnetic fraction to the EAF with partial recoveries of iron, zinc and chromium and leaving a compact, non-pollutant residue.

Energy conservation in the refinery by utilizing reformed fuel gas and furnace flue gases

Decrease of fuel supplies and cost increases make it vital for industries, especially energy intensive ones, to consider conserving available sources and convert losses into sources of energy. In this paper, a gas turbine-based cogeneration system is suggested to utilize a refinery's reformer gas in the gas turbine, and furnaces flue gases together with the engine exhaust gases in a heat recovery steam generator, HRSG. This is proposed as an alternative to the currently used system where the gas turbine and the steam generator are used separately. Operating variables comprising compressor pressure ratio and turbine inlet temperature are varied widely to evaluate performance; namely power, SFC, overall efficiency and annual fuel savings at design and off-design loading conditions using a dedicated computer program. Results show that the proposed system offers 100% higher overall efficiency and $5.25 million annual fuel saving for a 12 MW e gas turbine.

Theoretical and experimental study of the removal of dust particles from flue gases using two-phase steam-water droplet mixtures

The removal of dust particles using two-phase steam-water droplet mixtures has been studied. Two-phase steam-water droplet jets obtained by the flashing expansion of subcooled water, through convergent/divergent nozzles, have been characterized. The water droplet sizes and velocities were measured through the use of stroboscopic photography and laser-doppler velocimetry, respectively. A theoretical model using one-dimensional mass, momentum, and energy balances together with the concept of a critical Weber number criterion was developed to predict water droplet sizes and velocities. The agreement between measurements and predictions was reasonable. A theoretical model for predicting dust collection efficiencies of a two-phase scrubber was developed. It was determined that dust collection efficiencies exceeding 99 pct for basic oxygen furnace flue gases could be obtained using a two-phase scrubber.

Coal liquefaction catalysis by industrial metallic wastes

Catalytic activity of industrial metallic wastes in coal liquefaction was examined in a 100lb/day continuous coal processing development unit. Red mud, a waste material from the aluminium industry, and an electric furnace flue dust containing Ni, Mo, Co and Fe showed a pronounced effect on the conversion of a Kentucky bituminous coal. Coal conversion and oil production increased significantly with the addition of red mud and flue dust. Comparison of the catalytic activity of pyrite, red mud, and flue dust, based on selectivity analysis, showed that red mud was the most desirable disposable catalyst. However, if the primary goal of coal liquefaction is high oil production, irrespective of hydrogen consumption, pyrite is the most active catalyst among those discussed in the paper.

Staged-electric ironmaking utilizing solid wastes of the aluminum and steel industries

A new approach is presented for utilizing solid wastes of the aluminum and steel industries, the Staged-Electric ironmaking process, which involves a traveling grate for preparing preheated and prereduced pellets for a submerged arc electric smelting furnace. Either red mud from production of alumina or a blend of blast furnace flue dust, sludge and basic oxygen furnace dust as steel plant wastes are the prominent raw materials for the process. These off-grade sources of iron units are converted to steel and high carbon hot metal respectively with only minor metallurgical penalties. A method of extending the technology to commercial practice is presented.

Water analogue model achieves optimal design of furnace flue gas collection system

Arc furnaces used for melting and refining steel generate large amounts of smoke and dust that can cause severe pollution in and around the furnace building unless a satisfactory depollution system is provided. This paper discusses a water analogue model study conducted at Neyrtec's Research & Test Centre to design an efficient furnace-pollution collection system in which the gas flow to be processed was optimized. The study showed that this flow could be 25–30 per cent lower than the value recommended by dust collection plant suppliers on the basis of standard design procedures. A fullscale collection system based on the design developed with the model has just been completed. The fullscale system confirmed the excellence of the collection efficiencies and the validity of the model results.

Determination of zinc in blast furnace flue dusts

Two methods for the determination of zinc in blast-furnace flue dusts are described. One involves a solvent extraction step using methyl isobutyl ketone to separate the zinc from the bulk of the interfering elements, followed by a complexometric titration of the zinc with EDTA, using Eriochrome Black T as indicator. The other employs differential pulse polarography with a hydrochloric acid + pyridine supporting electrolyte. In this method, the interference of iron is prevented by reducing it with hydroxylamine hydrochloride; aluminium is complexed with potassium fluoride. Other elements, with the exception of cobalt, do not interfere. Excellent agreement between the two methods is obtained in the range 0.01–0.6% zinc.

Retinal hemorrhages in subacute carbon monoxide poisoning. Exposures in homes with blocked furnace flues

Retinal hemorrhages in subacute carbon monoxide poisoning. Exposures in homes with blocked furnace flues

Cleaning of open hearth furnace flue gases

Cleaning of open hearth furnace flue gases

Use of cermet filters for purifying samples of open-hearth furnace flue gases

1. A method has been successfully worked out for purifying samples of flue gas by cermet filters under high temperature and dust-laden conditions and moisture content up to 25 vol.%. 2. The cermet filters of steel Kh17N2 placed in the flue gases of open-hearth furnaces showed: a) high scale resistance which ensures reliable operation during the time between furnace repairs at temperatures up to 673°K; b) high degree of gas purification (to 3–4 μ); c) good regenerability (the greatest effectiveness of regeneration was achieved at Vf/Vr = 0.63); d) minor clogging in depth of the filter owing to the presence of a monolayer on the surface of the cermet tube. 3. The use of gas purification by cermet filters permitted sampling and cleaning gases at temperatures above the dew point, which makes it possible to eliminate condensation and corrosion of the lines and to analyze the flue gas for moisture content, which is valuable information for controlling the melting process.

Vacuum removal of dust from open-hearth furnace flues

Vacuum removal of dust from open-hearth furnace flues

Steam Jets Efficiently Remove Dust From Open Hearth Furnace Flues

Steam Jets Efficiently Remove Dust From Open Hearth Furnace Flues