Run-of-kiln

Where practicable, the sample should be of run-of-kiln lime. However, shaft kilns are usually fed with lump limestone and it may be impractical to take representative samples and to install sample preparation equipment large enough to handle the product. 

In such cases, samples should be taken of smaller fractions of lime produced by crushing and/or screening. Test results from such samples can be correlated with those for run-of-kiln lime if required. 

As rotary kilns normally burn relatively small stone, sampling run-of-kiln lime (or, indeed, lime as it is discharged from the kiln into the cooler) does not present a problem. Routine samples should be taken at suitable intervals and tested immediately, preferably by the operator, so that corrective action can be taken as quickly as possible. Additional samples should be taken as and when the operator requires them. 

When selecting a product for agricultural liming, a critical factor is the delivered cost per unit of neutralising value [30.2]. In consequence, when lime is used, inexpensive grades of lime are favoured. TTiese include the fines screened from run-of-kiln lime, which contain more impurities (such as fuel ash, sulfur and clay) than the coarser fractions (see section 17.1.3). Hydrator rejects (section 20.4.3) and carbide lime (section 22.10) are also used. 

Because quicklime is relatively sensitive to abrasion and impact, it is an inherently dusty product. Run of kiln lime typically contains 5 to 10 % of material finer than 6 mm, a significant proportion of which is sufficiently fine (less than 75 pm) to become airborne at transfer points. Such material is generally of marketable quality and, after collection, can usually be blended back into the product. 

Belt conveyors are widely used to transport run-of kiln quicklime to the processing plant, llie conveyors should be enclosed to prevent wind-whip (as well as to keep off rain). Transfer points should be fitted with hoods and dust extraction. Bag filters are generally preferred, with the collected dust being discharged on to the down-stream conveyor. Conveyor discharge points should be arranged to minimise free-fall and should either be enclosed, or fitted with dust extraction. 

Reactions such as the above have been used for the large-scale commercial production of WC by Kenna-metal, Inc. in a process called the Macro Process [28]. Thermodynamics for the analogous molybdenum reaction show that the reaction is highly exothermic (Table 3). The solid reactants are metered into a carbon-lined kiln to develop a self-sustained exothermic reaction. The reaction occurs in a pool of molten metal at temperatures above 2800 K. At the end of the run the kiln contents solidify into a lower heavy layer of carbide crystals and an upper slag layer of oxides. 

Industrial preparation. Raw magnesite coming from the run-of-mine is calcined between 700 and 1000°C in a vertical shaft kiln and decomposes yielding magnesium oxide or magnesia (MgO) and giving off carbon dioxide gas ... 

Figure 1. Waste plasterboard gypsum and various types of waste materials (1) basin oxygen slag (2) run of station ash (3) lime (4) cement kiln dust and (5) incinerated ash...

The use of plasterboard gypsum (PG) combined in mixtures with blast fiiniace slag, cement kiln dust (CKD), cement bypass dust (BPD) and power station run-of-station ash (ROSA) was investigated to form a novel blended binder with pozzolanic properties. This novel binder had potential use to stabilise soils and to produce semi-dry roller compacted paste and roller-compacted concrete (RCC) for road foundation construction. 

The sound levels emitted by the lifter zone change quite distinctly with variations in the running of the kiln and often correspond (with sometime lag) to the variations in the burning zone temperature. With a high fines content the sound levels, measured at a distance of 1 m from the cooler, may vary by about 20 dB (A). If these variations in sound are utilized as a criterion for kiln control, it should be remembered, however, that a high proportion of fine particles may, under certain raw material conditions, also be formed as a result of "over-burning" the clinker. 

When electricity, gas, water, lime, sodium carbonate, phosphoric acid, tanks, pumps, switches, valves, analytical equipment, and controls have been properly placed, it is time to consider the kiln itself and all the auxiliary equipment required to run the kiln. Of instant concern today are emissions and waste products. Dust collectors must be in place and operational before a kiln can be operated. There must also be a means of disposing or recycling off specification product. Poor-quality products are usually produced in the first trial runs of new equipment. 

Cost Data for Kilns Purchase prices, weights, and horsepower requirements of typical units are given in Table 12-21. Installed costs will run to from 300 to 500 percent of purchase cost. Maintenance will average 5 to 10 percent of the total installed cost per year but is dependent largely on the hfe of the refractoiy lining. 

No. 2 fuel oil is a petroleum distillate that may be referred to as domestic fuel oil or industrial fuel oil. Domestic fuel oil is usually lighter and straight-run refined it is used primarily for home heating and to produce diesel fuel. Industrial distillate is the cracked type, or a blend of straight-run and cracked. It is used in smelting furnaces, ceramic kilns, and packaged boilers. 

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