Box kiln

Sintering takes place in a kiln. There are many types of kilns for the different types of sintering used in industry. Two types of kiln are typical. One is the box kiln and the other is a tunnel kiln. The box kiln is simply an insulated box in which the ceramic green bodies are piled in their... 

FIGURE 40.45 A vertical cross section through a single-tracked, box kiln. (Adapted from Keey, R.B. et al., The Kiln-Drying of Lumber, Springer, Berlin, Germany, 2000.)... 

Box Kiln. A relatively small industrial intermittent kiln of box-like shape Boxing. The placing of biscuit hollow-ware, e.g. cups, rim to rim one on another this helps to prevent distortion during firing. 

The raw batch calcination can be accomplished in almost any kind of furnace. Tunnel kilns, box kilns, shuttle kilns, and rotary kilns have been used for many years, each with its own advantages, disadvantages, and limitations. In some instances, patents have been issued for the calcination technique Special firing profiles have been developed for some pigments to guide the reaction chemistry. 

Air Drying Equipment. Tunnel kiln dryers (70) are long furnaces comprised of several zones of different temperature, humidity, and air flow through which the ware travels on a moving car or belt. These kilns afford continuous processing. Periodic kiln cross-circulation dryers (70) are box furnaces in which ware is stacked on permanent racks or on a car that can be shuttled in and out of the furnace. Fans or jets are used to circulate heat uniformly through the ware. The process is not continuous, but production rates can be enhanced by shuttling multiple cars. 

Wet mixes are usually dried before calcination. Calcination is performed continuously in rotary or tunnel kilns, or batchwise in directly fired drum or box furnaces. The temperature at which the mixed metal oxide pigments are formed can be reduced by adding mineralizing agents [3.75]. In the case of chromium rutile pigments, addition of magnesium compounds [3.81] or lithium compounds [3.80] before calcination improves thermal stability in plastics. 

Modern rotary kiln plants have capacities of up to ca. 500 t/d, continuous grate furnaces up to 1000 t/d. The residence times are less than 1 hour. In kettles throughputs up to 150 t/d with residence times of several hours are aimed for. Box shaft kilns are no longer viable due to the lengthy (several day) calcination times. 

Drying is carried out in rocking, box and tunnel driers often utilizing the combustion heat from kilns. Rapid drying (ca. 10 min) with IR irradiation has recently been introduced for thin-walled articles (crockery). This compares with drying times for large format articles of up to 24 h and more (e.g. sanitary ware). 

Chemical munitions are placed in a cardboard box or carrier, which is transported to the top of the kiln. The boxed munitions are fed into the kiln through two loading chambers, each having its own door. The boxed munitions are dropped onto a heated (500°C-550°C) shrapnel (scrap) bed at the bottom of the detonation chamber. If sufficient energy from energetics in the munition is released, no additional external heating from the electrical resistance elements is required. If the munition does not contain energetics, additional heat can be provided by the electrical resistance elements. 

Chemical munitions are placed in a cardboard box or carrier, preferably by robot but if need be, manually. The box is placed on an elevator for the SK2000 version or on a trolley conveyor for the smaller units and is transported to the top of the kiln. Leaking munitions are placed in an airtight plastic bag and then in the box before being loaded. Munitions that are already in a single round container can be loaded onto the conveyor or elevator while in the container. 

During the winter of 1991, bulk mustard was drained from preheated (20°C) 1 ton containers into heavy-walled, polyethylene-lined cardboard boxes and allowed to freeze under cool conditions (<0°C). The boxes containing frozen mustard were then placed in sealed metal cargo containers and immediately transported to the incinerator site. The boxes were then off-loaded and processed via the rotary kiln solids feed system. All bulk mustard (3 tonnes) was destroyed in this manner as part of the incinerator test bum program (see below). 

In July of 2003 a new step was introduced at the plant, namely annealing of GeoDeck boards, in order to eliminate boards shrinkage. Initially, third-party kilns were employed to do the job, and in many cases boards were obviously overheated. They often became brittle and discolored. Being placed in the weathering box, they showed crumbling—in the worst case—even after 4 days. More detailed studies have shown that the lower the density, the less time it takes for board crumbling. Boards of density 1.06-1.07 g/caf crumbled after 4 days. Boards of density 1.08-1.10 g/cm crumbled after 7-12 days. Boards of density 1.15-1.16 g/cm did not crumble after a month. 

Minimizing heat storage in, and loss through, conveyors, trays, rollers, kiln furniture, piers, spacers, packing boxes, and protective atmospheres... 

Losses to Containers, Conveyors,Trays, Rollers, Kiln Furniture, Piers, Supports, Spacers, Boxes, Packing for Atmosphere Protection, and Charging Equipment, Including Hand Tongs and Charging Machine Tongs... 

Boxing-in. A method of setting in a kiln so that, for example, special refractory shapes can be fired without being stressed and deformed also known as POCKET SETTING. 

Saggar. A fireclay box, usually oval (0.6 X 0.45 m), in which pottery-ware can be set in a kiln. The object is to protect the ware from contamination by the kiln gases and the name is generally thought to be a corruption of the word safeguard . Since the bottle-oven has become obsolete as a kiln for the firing of pottery and since clean fuels and electricity have become increasingly used in the industry. 

Shuttle Kiln. An intermittent bogie kiln consisting of a box-like structure with doors at each end and accommodating kiln cars (usually two in number). Pottery-ware is set on the refractory decks of the cars which are then pushed along rails into the kiln, displacing two other cars of fired ware from the kiln. The fired ware is taken from the displaced cars which are then re-set with more ware to be fired. The shuttle movement of the kiln cars is is then repeated (cf. bogie kiln). 

Applications have included fumance parts, kiln linings, and annealing boxes. 

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