Sintering coke additions

The manner in which carbon is utilised for zinc production is affected by heat balance issues as well as chemical requirements for metal reduction. The heat balance is influenced by the amount of slag produced, the blast preheat and the preheat achieved in coke and sinter. Apart from the quantity of zinc oxide reduced, the chemical factors include the lead and iron contents of sinter and the moisture entering the furnace in blast air and in sinter or additives. Based on typical operating conditions as indicated above and a lead production of close to 50 per cent of the zinc production, the empirical formula used to relate carbon consumption to zinc production is given by Equation 6.1 ... 

Sintering. The charge for sintering is prepared by blending selected concentrates, smelter by-products, returned sinter, flue dust, and when required, additional fuel such as coke bree2e. The blend is then peUeti2ed in preparation for sintering. 

The value of E0 is probably a little high if coking were the only mechanism of deactivation, thus it probably reflects sintering or a solid state transformation (with water vapor ) as being an additional important factor. 

Addition of promoters to resist deactivation. For example, greater support stability with alumina is achieved with small amounts of added silica or zirconia, sintering and coking of platinum is reduced by adding rhenium, and acid sites neutralized with potassium. 

In addition, catalysts must have high thermal stability to resist sintering, particularly where there is a need for periodic regeneration by combustion of coke deposited on the catalyst. A further desirable characteristic is the ability to resist deactivating influence of poisons, notaby sulfur compounds, which are often present in reactant streams. 

The effect of chloride on the activity and selectivity is mainly through the support. It has been noted earlier that, by changing support-metal interactions, chloride minimizes sintering. The formation of large particles would favor hydrogenolysis. In addition, chloride increases the acidity of the support, which improves isomerization and, in some cases, cracking reactions. Increasing the support acidity would also increase the ability of the support to adsorb coke. Hence, there is likely to be more spillover of coke from metal to support, and consequently less coke... 

An additional mechanism of deactivation, due to catalyst particle agglomeration (sintering), leads to reduction in active specific surface area and, as a result, catalyst activity. Obviously, such deactivated catalytic pellets cannot be regenerated just by combustion of hydrocarbons over the deactivated catalytic bed (like in case of coking) this type of deactivation is rather irreversible. Moreover, periodic regenerations of the catalytic bed (to bum off deposited coke) make the sintering deactivation even more severe. 

In this micro sintering experiments laterite ore should be crushed to the needed granularity firstly less than 8mm accounted for 90%. The reducing agent coke was screened to 200 mesh and the proportion is about 80%.. Conduct four groups totally the additives fluorite content are 0% and 5%, respectively, the maximum temperature is seted of 1050 ° C (alkalinity to 1), and 1200 ° C (alkalinity to 2). When the furnace temperature up to the maximum temperature of the test requirement, the samples should be cooled to room temperature in the furnace after heat preservation for 10 min. A small amount of the sample was pulverized after the experiment for XRD analysis and then to determine the compressive property. 

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