Hearth reactors

FIG. 23-43 Reactors for solids, (a) Temperature profiles in a rotary cement lain, (h) A multiple hearth reactor, (c) Vertical lain for lime burning, 55 ton/d. (d) Five-stage fluidized bed lime burner, 4 by 14 m, 100 ton/d. (e) A fluidized bed for roasting iron sulfides. (/) Conditions in a vertical moving bed (blast furnace) for reduction of iron oxides, (g) A mechanical salt cake furnace. To convert ton/d to kg/h, multiply by 907. 

Figure 1730. Kilns and hearth furnaces Walas, 1959). (a) Temperature profiles in a rotary cement kiln, (b) Space velocities in rotary kilns, (c) Continuous lime kiln for production of approximately 55tons/24hr. (d) Stirred salt cake furnace operating at 1000°F, 11-18 ft dia, 6-10 tons salt/24 hr. (e) Multiple-hearth reactor one with 9 trays, 16 ft dia and 35 ft high roasts 1250 lb/hr iron pyrite. (f) Siements-Martin furnace and heat regenerators a hearth 13 ft wide and 40 ft long makes 10 tons/hr of steel with a residence time of 10 hr.

Raked hearth reactors were once extensively used in the metals extraction industries but are now being superseded. 

Different types of reactors are utilized for a wide variety of pyrolysis applications, including processing of waste plastics. The worldwide waste plastic pyrolysis systems utilize the fixed-bed designs of vertical shaft reactors and dual fluidized-bed, rotary kiln and multiple hearth reactor systems. The type of reactor used is chiefly based on material to be pyrolyzed and expected products from the pyrolysis. Stainless steel shaking type batch autoclave and stainless steel micro tubular reactors have also been used extensively [14]. Fluidized-bed reactors have been extensively used in producing raw petrochemicals from the pyrolysis of waste plastics [22, 24]. 

FIG. 19-24 Reactors for solids, a) Temperature profiles in a rotary cement kiln, h) A multiple-hearth reactor, (c) Vertical kiln for lime burning, 55 ton/d. d) Five-... 

Pakdel, H. Roy, C. "Chemical characterization of wood oils obtained in a vacuum pyrolysis multiple hearth reactor." In This Volume. 

Oil Refining. Further fractionation of the wood oil product is necessary when the objective is to either recover pure chemical compounds, or upgrade or process specific chemical group components. Results which are reported elsewhere by Renaud et al (7) and Pakdel et al (8) show that the multiple-hearth reactor can be operated in a mode that enables the separation and recovery of selected fractions of liquid fuels and chemicals. 

A more recent study of the heat fluxes inside the reactor as well as a comparison of the theoretical data predicted by a radiation heat transfer model showed that radiation is the main mode of heat transfer in the multiple hearth reactor configuration used (10). 

A multiple-hearth reactor has been successfully tested for the production of high yields of liquid fuels and chemicals. The reactor enabled the separation and recovery of water on the one hand and oil fractions or the other hand. Biooil yields reached about 50% by weight of the air-dry feedstock. Both the oil and charcoal have a higher calorific value than the raw wood feedstock. 

Chemical Characterization of Wood Pyrolysis Oils Obtained in a Vacuum-Pyrolysis Multiple-Hearth Reactor... 

PAKDEL ROY Vacuum-Pyrolysis Multiple-Hearth Reactor... 

Reactors widely used for the thermal regeneration of spent carbon are multiple hearth reactors, rotary kilns, moving bed reactors and fluidized bed reactors. Comparisons of these reactors were made in terms of residence time, steam and fuel consumption in Fig. 9.9 (Suzuki, 1976). 

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