Rice hull process

Tluid-hed reactor rice hulls process heat... 

Self catalyzed rice hull processes SiC and SiN microwhiskers 2.2 [14]... 

Rice hull hydrocarbons supply the carbon source and rice hull ash the silicon source. This is an early carbothermal process (Equ. 10a). At <900°C, coking (Equ. 10b and 10c) removes water and organics and yields a mixture of silica and carbon, and at <1700°C, pyrolysis yields silicon carbide whiskers (Equation lOd). The overall yield is 1 percent. Three variants of the rice hull process are known. Compacted rice hulls can be pyrolized at 1600°C without coking [14], thus directly yielding a mixture of graphite and SiC whiskers, 10-200 pm in length and... 

Silica gel, carbon furnace black and cobalt chloride yield silicon carbide whiskers, or Tokawhiskers [30], in a metal catalyzed process at >1450°C. A process variant [9] yields SiC whiskers >1350 C in a fixed bed percolated by a hydrogen flow. The addition of iron above 1450°C affords submicron whiskers ending with a silicon rich droplet. The iron seems to evaporate and condense below 1450°C leaving behind whiskers with silicon rich tip >1450 C. These processes use the same starting materials as the rice hull processes but they also use a metal particle catalyst. As a result, they are believed to proceed by a VLS phase transformation. 

Short VLS or VS whiskers are obtained with diameters ranging from 0.6 to <1.0 pm and lengths ranging from 10 to <100 pm by chemical vapor deposition, chemical mixing and carbothermal processes. Whiskers derived by the rice hull process reflect the most irregular growth habitat. Two variants have been observed, whiskers without inclusions in any part of their structure, and whiskers with nanoparticulate inclusions in the core of their structure. The sheath of these sheath/core whiskers is free of inclusions. Only their core contains nanoparticulate inclusions, such as Si-O-C phases and nanocrystalline Ca, Mn, and Fe impurities. 

In the United States, up to about 4 x 10 Btu/yr of biofuels ate consumed for electricity generation, raising process heat, and domestic heat. Eurthermore, much of the energy needs of many nations are met by biofuels, including wood and wood waste, spent pulping fiquors, bagasse, and municipal waste. Some use is also made of dried com cobs, rice hulls, and a wide variety of agricultural wastes used in niche appfications. 

In one modification of this procedure, the starting material is pyroly2ed rice hulls in place of more conventional forms of sihcon dioxide (31). Another unique process involves chlorination of a combination of SiC and Si02 with carbon in a fluid-bed reactor (32). The advantages of this process are that it is less energy-intensive and substantially free of lower sihcon chlorides. 

Wood and wood waste includes residues from the forest and the mill. Bark, sawdust and other mill wastes are all suitable fuels. Agricultural residues include corncobs, sugar cane bagasse (the stalks after processing), leaves, and rice hulls. MSW materials include paper products, cloth, yard wastes, construction debris, and packaging materials. 

Iowa. Modem industrial prepns start with agricultural residues such as oat hulls, corn cobs, rice hulls, bran, etc, which have a relatively high pentosan content (Ref 10). In these processes pentosans are hydrolyzed to pentoses by acid digestion, and these split out water internally to form forfurals ... 

Pyrolysis is the process of thermal degradation of a substance into smaller, less complex molecules. Many processes exist to thermally depolymerize tires to salable products. Almost any organic substance can be decomposed this way, including rice hulls, polyester fabric, nut shells, coal and heavy crude oil. Pyrolysis is also known as destructive distillation, thermal depolymerization, thermal cracking, coking, and carbonization. 

Whiskers are normally obtained by vapor phase growth. Early in the 1970s, a new process was developed, starting from rice hulls, to produce SiC particles and... 

The heating value of a typical biomass is sufficient to produce steam in excess of that required by the activated process if the system has been designed for maximum thermal efficiency. This can be especially important to developing countries who have large supplies of biomass such as rice hulls or coconut shells and who are currently contemplating the manufacture of activated carbon for export or local water treatment. 

TABLE 3.10 Effect of rice hulls on the oxidative induction time (the OIT) of an HDPE, processed on the Brahender laboratory extruder... 

The composites were processed on the Brabender laboratory extruder. The OIT was measured at 190°C. The OIT values show the resistance of the material to oxidation The higher the OIT, the higher the resistance. The amount of Biodac was 28% in all cases. The amount of rice hulls and sawdust was 32% in all the cases. The amount of HDPE was 40% in all the cases. 

Y.H. Lee, T. Kuboki, C.B. Park, and M. Sain. Processing-property behaviors of PP/rice hull and PP/rice hull/nano-clay composites. In The Global Outlook for Natural Fiber Wood Composites, Intertech, Portland, ME, Lake Buena Vista, FL, 2005. 

Tables 6.8 and 6.9 show some experimental data for GeoDeck deck boards having the same formulation but different density as a result of different regimes of processing (speed and temperature of the extrusion) and different moisture content of the initial ingredients (rice hulls, first of all).

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