Kiln types

The ABS polymer is recovered through coagulation of the ABS latex. Coagulation is usually achieved by the addition of an agent to the latex which destabilizes the emulsion. The resulting slurry can then be filtered or centrifuged to recover the ABS resin. The wet resin is dried to a low moisture content. A variety of dryers can be used for ABS, including tray, fluid bed, and rotary kiln type dryers. 

Miscellaneous Kilns. A U.S. kiln, the Fluo-Sohds, appears to be another vertical kiln type, but this is its only similarity. It operates on a different principle. It utilizes as kiln feed only a discrete granulation of 0.225—2.4 mm (65—8 mesh) sizes. DeHcately controlled by air and exhaust gas pressure, the kiln feed of granules is fluidized as a dense suspension. Because it is instmmented, this kiln can produce a very reactive lime at better than average thermal efficiency. The kiln, however, has limited utifity because the cost of obtaining the kiln feed with many hard, compact limestones is prohibitive. 

The Calcimatic is a patented kiln of Canadian origin that is radically different from other kiln types. It consists of a circular traveling hearth of variable speed, supported on two concentric tiers of rollers. Kiln feed of 12.7 mm is fed onto the hearth in a 2.5—10 cm bed from a preheater chamber. The kiln is usually fired with natural gas or fuel oil, although the option of using pulverized coal has also been developed. After great interest, resulting in sales of many units throughout the world, the popularity of the Calcimatic has ebbed because of disappointment in the unit s mediocre thermal efficiency. 

Three different types of furnaces are generally in use for calcination. The shaft furnace is considered to be the most suited for calcining coarse limestone. Furnaces of the rotary kiln type are used for handling materials of mixed particle sizes and lumps which disintegrate during the process. Calcination can be carried out in a fluidized bed-reactor for materials of small and uniform particle size. These furnaces are usually fired with gas, oil or coke in some cases electric heating is resorted to. 

The rotary-kiln type incinerator mentioned by S. Slemrod of Picatinny Arsenal (Ref 24) for destruction of Mred-water syrup, obtained as waste in US plants manufacturing TNT by the batch method. One of such kilns was in operation at Keystone... 

The dehydrochlorinated molten polymer in the molten polymer vessel is qnantitatively fed into the pyrolysis reactor (Figure 26.11), which is of rotary kiln type. It has a hot air jacket and ceramic balls inside to prevent coking problems, as shown on the Fignre 26.12. Thermal degradation is at 400°C and 5 kPa overpressure. 

Virtually all the charcoal made in these regions - other than that used for specialised industrial purposes - is made in kilns. A wide range of kiln types is in use. Some are quite primitive, like the simple earth and vegetation covered kilns used by itinerant charcoal burners. Others, such as the beehive kilns used by Brazil s iron and steel industry, are comparatively sophisticated [5] [6]. Perhaps most widespread, and typical of the kilns used by smaller commercial enterprises in the developing world, are traditional earth or earthmound kilns like those to be found in Zambia [7] and Sudan [8]-... 

By far the most widely utilized type of ceramic kiln is the tunnel kiln, through which ware placed on refractory-lined cars is passed. Compared with the kiln types mentioned above, tunnel kilns have several advantages, in particular ... 

The thermal efficiency of ceramic kilns depends on a number of factors, in particular on the kiln type. The consumption of heat related to unit amount of ware is highest for periodic furnaces, and lower by about one half for tunnel or continuous multi-chamber kilns. The consumption of heat also depends on the kind of firing, a direct-fired kiln having a lower consumption than a muffle kiln where the ware is protected from direct contact with combustion gases. For example, a direct-fired tunnel kiln for glost firing of tiles has a fuel consumption 40% lower than a similar muffle tunnel kiln (Holmes, 1978),... 

In addition to the different shaft kiln types, rotary kilns are often used for lime burning. This enables good quality quicklime to be obtained with cheap fuels. Smaller limestone particles (10 to 60 mm) are utilized. 

The burning of the raw materials in all the described processes is carried out at ca. 1450 C, mainly in rotary kilns. Table 5.3-7 summarizes the individual processes and the kiln types used for them. 

Finally the kiln type and design has to be included in the model size, insulation, operating temperatures and throughput in order to correctly dimension operational units (fans, heat exchanges) to optimize mill drying - and this involves a trade-off between flexibility, costs and befits. 

Slurry" from more than one reactor is "dropped" into a "stripper" to remove unreacted monomer and then transferred to a large "blend tank." The suspended polymer particle can easily be separated from the water phase by filtering or centrifuging. The "wet cake" is then sent to a rotary kiln type dryer and bagged. The particle size of polymers obtained in this manner are usually much larger than those obtained with emulsion polymerization. They can be defined by a conventional screen analysis with respect to particle size. 

The traditional/long rotary kiln (type J in Table 16.1 and Fig. 16.15) consists of a rotating cylinder (110 to 140 m long) inclined at an angle of 3 to 4° to the horizontal. Limestone is fed into the upper back-end and fuel plus combustion air is fired into the lower front-end . Quicklime is discharged from the kiln into a lime cooler, where it is used to pre-heat the combustion air. 

A conservative capital cost estimate was made for a 610-mm diameter SBD designed to dry 220 kg/h of wet sludge with 20% by weight solids. The cost compared favorably with available kiln-type technologies and shows that the spouted bed is cost competitive with conventional technology. 

Total direct contact steam averages about 1 kg of steam for each 12 to 14 kg of raw material (rapeseed) processed. Rapeseed meal is difficult to thoroughly desolventize residual levels of hexane are typically 300 to 1200 ppm. This problem merits research for both safety and economic reasons. Moisture laden (25% or more) desolventized meal may be dried in the lower stages of the desolventizer in small plants. Larger plants use a separate rotating kiln-type steam tube drier to reduce the water content to 12-14%, which is then followed by an air cooler in which the moisture is further reduced to less than 12%, the evaporating moisture absorbing some of the heat. 

Toscoal Tosco Kiln-type retort vessel 425-540 795-1005 15 5 min 80-90 5-10 5-10... 

Recycl Blacks. The pyrolysis of carbon black containing rubber goods has been promoted as a solution to the accumulation of waste tires. In the processes in question, tires are pyrolyzed in the absence of oxygen, usually in indirect fired rotary kiln-type units. The mbber and extender oils are cracked to hydrocarbons which are collected and sold as fuels or petrochemical feedstocks. The gaseous pyrolysis products are burned as fuel for the process. Steel tire cord is removed magnetically and the remainder of the residue is milled into a pyrolysis black. This contains the carbon black, silica, and other metal oxides from the rubber and some newly created char. Typically these materials have 8-10% ash, and contain... 

Of type A are at present 32 plants in operation, of type B 11 and of type C 22. Merely 6 plants of type A or B are equipped with a calcinator, 3 in addition with a tertiary air dnct. The average thronghput of the various kiln types ranges from 1,000 to 3,050 t/d, that of the individual kilns even from 500 to 3,800 t/d. This especially results in different specifie heat losses through the wall of the rotary kiln, bnt also of the cooler and the preheater and thus in the total also in different mean specific fuel energy eonsirmptions (s. table 3). 

The four major components of hazardous waste incineration systems are shown in Figure 16.14. Hazardous waste incinerators can be divided as follows, based on the type of combustion chamber about 40% of U.S. incinerators are of the rotary kiln type consisting of a rotating cylinder lined... 

R D for advanced TRISO fuel technologies such as the UCO kernel fabrication and the ZrC coating has been carried out. As for the UCO kernel fabrication, a process for the carbon dissolution was established, and weU-shaped discrete ADU liquid droplets were obtained using an external gelation method (Jeong et al., 2007). Currently, a new kiln-type heating furnace has been built for the heat treatment... 

---