Sintering plant emissions

Partitioning of "Po and "Pb between Particulate and Gas Phase in Sinter Plant Emissions... 

Studies were carried out at the two Tata Steel UK sinter plants to determine the degree of partitioning of Po and Pb between the particulate and gas phase using British Standard EN 14385 [3], which affords discrimination between particulate-bound and gas phase metals. The results obtained at Sinter Plant 1 clearly indicated that both Po and Pb were predominantly present in the particulate phase in sinter plant emissions. As can be... 

The results of this study demonstrate that Po and Pb are present in the particulate phase and therefore that the use of British Standard EN 13284-1 [2] is justified for the sampling of sinter plant emissions [7]. 

Other Le d Smeltings Processes. Stricter regulations concerning lead emissions and ambient lead in ak levels (see Airpollution), and the necessity to reduce capital and operating costs have encouraged the development of alternative lead smelting processes to replace the sinter plant—blast furnace combination. 

Emissions from sinter plants are generated from raw material handling, windbox exhaust, sinter discharge (associated sinter crushers and hot screens), and from the cooler and cold screen. The primary source of particulate emissions, mainly irons oxides, magnesium oxide, sulfur oxides, carbonaceous compounds, aliphatic hydrocarbons, and chlorides, are due to the windbox exhaust. Contaminants such as fluorides, ammonia, and arsenic may also be present. At the discharge end,... 

Wang, L., Lee, W., Tsai, P, Lee, W., and Chang-Chien, G., Emissions of polychlorinated dibenzo-p-dioxins and dibenzofurans from stack flue gases of sinter plants, Chemosphere, 50(9), 1123-1129, 2003. 

Lahl U (1994), Chemosphere 29 1939-1945.. .Sintering plants of steel industry - PCDD/F emission status and perspectives"... 

Sintering machines prepare large nodules (lumps) from beneficiated iron ore fines, and iron oxide containing dusts recycled from particulate emission control equipment. It is estimated that uncontrolled operation would discharge particulate at the rate of about 0.3% of the mass of sinter produced, or about 2,700 kg from a machine producing 900 tonnes of sinter per day. Cyclones can decrease the particulate emission to about one-quarter of these levels. It is also possible to use the sintering machine as a roaster to enable sulfur removal from sulfur-containing iron ores. This produces a more amenable ore, but it also produces sulfur dioxide in the waste gas stream. No emission-rate data for sulfur dioxide in sinter plant exhaust gas is available, since this has not normally been recovered. However, a mathematical model which enables estimation has been described [13]. 

In the steel industry the most common source of sulfur oxide emissions is the burning of coke oven gas that has not been desulfurized. However, emissions from iron ore sinter plants are receiving considerable attention in Germany and Japan, if not yet in the United States. Pelletizing plants are another potentially significant source. In Germany, sinter plants are estimated to be responsible for about 6% of the total sulfur oxide emission (8). 

Although means are available for controlling the bulk of the emissions from the conventional lead and zinc smelters, new processes being developed offer greater economy as well as better emission control (9,10). Cominco Ltd. recently announced the development of a new process to replace the conventional lead smelting process with its sintering plants and blast furnaces (39). 

The data shown in Table III indicate a significant reduction of emissions into the atmosphere compared to the sinter plant blast furnace technology operated earlier. 

PCDD/F emission data are expressed in terms of the NATO-CCMS (North Atlantic Treaty Organization - Committee on the Challenges of Modem Society) toxic equivalence quantities (TEQ) for most important processes [31]. These processes include public power/heat plants based on coal and residual oil, non-industrial and industrial combustion of coal, oil, gas and wood, blast furnaces, sinter plants, non-ferrous and aluminum production, electric furnace steel plants, road transport, incineration of domestic, municipal and hospital waste. Emissions of dioxins from the combustion of kerosene with dichloroethane or dichlorobenzene are significant... 

Emission standards for SO2 vary widely, but a conunon concentration limit is 1.25 g of SO2 per Nm, which has to be met by sulfuric plant emissions. On this basis, sulfur emissions from the blast furnace commonly exceed normal standards by a substantial margin. This has indeed resulted in the closure of some European lead blast furnaces or the conversion to alternative technologies. The alternative is to scrub the gas after fume collection with a Ume slurry, which is capable of reducing the SO2 concentration to 0.01 per cent by volume or 0.3 g per Nm. Otherwise a combination of total plant ventilation gases from sinter plant and refining operations with blast furnaces gases may be able to meet overall emission concentration limits for sulfur, but at the expense of large gas volume movements per tonne of lead produced (at around 12 000 Nm /tonne of lead). 

The Kivcet process is robust and highly flexible in the range of possible feed materials, from high-grade concentrates through to secondary leach residues. It produces a low volume of smelter gas rich in SO2 and suitable for sulfuric acid production. It is also well contained with minimal opportunity for environmental emissions, particularly in comparison with sinter plant-blast furnace technology. 

The QSL process has significant advantages over sinter plant-blast furnace technologies. It is a single step smelting process, is well contained with low emissions and can accept a wide range of feed materials. It does not require dry feed as with the Kivcet process however, in its early stages it did not prove to be as robust or as flexible as the Kivcet process, particularly with attempts to use natural gas for reduction and in its ability to handle quantities of zinc plant residues. 

In 1995, in the United Kingdom the dominant source was the incineration of solid municipal waste, contributing an average of 70 % to the atmospheric emissions. Other major emissions are from sinter plants (steel mills), combustion of coal, emissions from iron and steel plants, from non-ferous metal operations, and combustion of clinical waste, summing up to 23% of total industrial emissions [389]. 

Table 2 Partitioning of Po and Pb in emission samples collected using British Standard EN14385 [3] at Sinter Plants 1 and 2.

The authors are grateful to colleagues at Tata Steel, Mr Simon Johnston, Mr Richard Earl and Mr Pete Smith for collecting the stack emission samples used in this study and providing expert advice in XRF and carbon-sulphur analysis. This work has benefitted from collaboration with the regulatory authorities who have confirmed that best practicable means were used to measure and control sinter plant stack emissions. 

Smoke from the factories was a constant element of the community s life. The aged zinc plant belched out prodigious amounts of fume and dust full of sulfur, zinc, lead, cadmium, and arsenic. Control technology existed—these emissions could be trapped in baghouses and electrostatic precipitators—but U.S. Steel, like its competitors, only installed these devices where it was profitable to do so. Thus the plant used the sulfur from its roasters to make acid and collected metallic fume from ore sintering. The sale of these by-products was vital to the economics of zinc making, a business whose personnel,... 

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