Pyrolysis and combustion of treated and untreated rice hulls

Hanna, Samir B.; Farag, L.M.; Mansour, Nabil

doi:10.1016/0040-6031(84)85112-6

Cited by 36 publications

(25 citation statements)

References 2 publications

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“…The black color of the residue produced by the process A is attributed to black carbon grains occluded in the residue particles 7,14 .…”

Section: Processes a And Bmentioning

confidence: 99%

“…Process A reproduces the common practice of quickly burning the hulls to produce heat and was studied by Hanna 7 and Krishnarao et al…”

Section: Processes a And Bmentioning

confidence: 99%

“…During burning, the impure elements, especially alkaline and alkaline earth oxides, strongly reduce the silica's SSA. Calcium, magnesium, potassium, sodium and aluminum oxides, all present in the hull, react at high temperatures and long soaking times with part of the silica to produce a kind of soda lime glass 7,11 , in which sodium is replaced by potassium, which reduces the residue's SSA to close 1.0 m 2 /g 12 . This point will be further discussed in section 3.4.…”

Section: Introductionmentioning

confidence: 99%

“…7 Crystalline phases, mainly cristobalite, develop during long sintering times at high temperatures, and carbon remains inside silica particles, turning the residue black [12][13][14] . The development of crystalline phases renders silica powder potentially dangerous for the human respiratory system 15 .…”

Section: Introductionmentioning

confidence: 99%

“…The straw/hull weight ratio is close to 3.6 3 and the world's annual rice output is around 300 million tons, representing a potential production of almost 40 million tons of silica from processed hulls and straw. The potential to extract high quality silica from these residues has attracted the attention of several researchers [4][5][6][7][8] . Although silica with high SSA can potentially be extracted by microbiological degradation because it excludes calcination, the hull's organic compounds are known to biodegrade only after long periods of time 9,10 , rendering this process an unviable alternative.…”

Section: Introductionmentioning

confidence: 99%

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Silica Derived from Burned Rice Hulls

2002

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Three new processes to obtain silica having high specific surface area from burned pre-treated rice hulls are presented and discussed. These procedures allow for the simultaneous recovery of biomass energy and the production of high quality silica at thermoelectric plants, without the risk of using corrosive substances in the burning process. The first method involves treatment of the hull with hot organic acid solutions before burning, the second with boiling water, both using an autoclave at temperatures close to150 °C, while the third method renders the hull fragile by treating it at 250 °C and reducing it to a fine powder before burning. The first two methods result in white amorphous silica that can show 500 m 2 /g of specific surface area. The third method, which does not remove the alkaline elements from the hull, produces an amorphous gray carbon-free powder whose specific surface area can be as high as 250 m 2 /g. An investigation of the specific surface area of the prepared silica indicates the alkaline elements are not mixed with silica in the hulls or combined as insoluble compounds. A comparison is made of these processes and the dissolution of silica by sodium hydroxide solutions is discussed.

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“…The black color of the residue produced by the process A is attributed to black carbon grains occluded in the residue particles 7,14 .…”

Section: Processes a And Bmentioning

confidence: 99%

“…Process A reproduces the common practice of quickly burning the hulls to produce heat and was studied by Hanna 7 and Krishnarao et al…”

Section: Processes a And Bmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Silica Derived from Burned Rice Hulls

2002

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Waste Recycling in Thermoelectric Materials

Bahrami

Schierning

Nielsch

2020

Advanced Energy Materials

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power plants, factories, motor vehicles, computers, or even human bodies into electricity. TEGs are suitable for small applications because of their compatibility, simplicity, and scalability. For example, electricity can be generated from small heat sources and by taking advantage of small temperature differences for powering wristwatches or wearable devices such as miniaturized accelerometers or electroencephalography (EEG) devices. [3,4] However, low efficiency and high fabrication cost are the main disadvantages of TEGs which hinder their vast application in the market. Although many studies have explored the ways to increase the efficiency of TEGs in converting the thermal to electric energy, cost of TE materials synthesis and miniaturized TEGs fabrication has not been addressed widely.TEGs require materials with high electrical conductivities and low thermal conductivities, as well as high thermopower (Seebeck coefficient, S) which in turn constrains the types of materials that can be used as a TE material. The direct conversion of thermal to electrical energy in response to a temperature gradient across a material can be calculated by using the following equationwhere ΔV is the generated voltage, S is the Seebeck coefficient or thermopower, and ΔT is the temperature difference. The performance of a TE material is defined by the dimensionless figure of merit (zT), which relates the material properties to its conversion efficiency, in the following way 2 l e ZT S T σ κ κ ) ( = +where σ is the electrical conductivity, κ l and κ e are the lattice and electronic contributions to the thermal conductivity of TE material, respectively, and T is the absolute temperature. High S 2 σ (power factor, PF) and low thermal conductivity, κ = κ l + κ e , lead to better performance. In practice, however, the mutual dependence between these material properties makes an optimization of zT difficult. For many decades since the 1950s, when research and development of bulk homogenous materials for TE applications started to increase, research and development efforts focused on elements derived from raw materials for synthesizing TE materials. The compounds synthesized from raw elements such as Thermoelectric (TE) technology enables the efficient conversion of waste heat generated in homes, transport, and industry into promptly accessible electrical energy. Such technology is thus finding increasing applications given the focus on alternative sources of energy. However, the synthesis of TE materials relies on costly and scarce elements, which are also environmentally damaging to extract. Moreover, spent TE modules lead to a waste of resources and cause severe pollution. To address these issues, many laboratory studies have explored the synthesis of TE materials using wastes and the recovery of scarce elements from spent modules, e.g., utilization of Si slurry as starting materials, development of biodegradable TE papers, and bacterial recovery and recycling of tellurium from spent TE modules. Yet, the outcomes of such work have no...

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