Ash content of wood

Production. Silicon is typically produced in a three-electrode, a-c submerged electric arc furnace by the carbothermic reduction of silicon dioxide (quartz) with carbonaceous reducing agents. The reductants consist of a mixture of coal (qv), charcoal, petroleum coke, and wood chips. Petroleum coke, if used, accounts for less than 10% of the total carbon requirements. Low ash bituminous coal, having a fixed carbon content of 55—70% and ash content of <4%, provides a majority of the required carbon. Typical carbon contribution is 65%. Charcoal, as a reductant, is highly reactive and varies in fixed carbon from 70—92%. Wood chips are added to the reductant mix to increase the raw material mix porosity, which improves the SiO (g) to solid carbon reaction. Silica is added to the furnace in the form of quartz, quartzite, or gravel. The key quartz requirements are friability and thermal stability. Depending on the desired silicon quality, the total oxide impurities in quartz may vary from 0.5—1%. 

The impact of extraneous inorganic matter on the analysis cannot be predicted. Most chemical analysis methods have been optimized for bark-free wood that has an ash content of less than 2 percent. These methods may not be applicable to herbaceous materials where structural silica can increase the ash content to more than 15 percent of the dry weight of the biomass. One potential problem with high ash samples is that inorganic materials, depending on their composition, may neutralize the sulfuric acid solutions used in the hydrolysis steps. The affect of pH changes... 

The ash content of a human body makes up about 5.6% of the body s weight 114 given a 132 lb. body, this comes to 7.3 lbs. The ashes from the 875,000 burned bodies would thus have weighed 6,387,500 lbs. The total quantity of ashes - wood ashes plus human ashes - would therefore have weighed almost 4,000 metric tons, or 8.6 million pounds, all of which (according to the witnesses) were then mixed with the soil and thrown back into the pits.115 Even if this quantity of ash had been mixed with the roughly 3.53 million cubic feet of soil excavated from the burial pits, it would be easy to find evidence for human remains of the quantity alleged by the witnesses. It must also be... 

The heating value depends on the moisture and ash contents of the densified material and is usually in the range of 15 to 17 MJ/kg. The use of asphaltic binders or pelletizing conditions that result in some carbonization can yield densified products that have higher heating values. Pellets, briquettes, and logs have been manufactured by densification methods from biomass for many years. Prestologs made from waste wood and sawdust were marketed before 1940 in North America, and the market for pellet fuels made from wood... 

Particulate control is by means of either a wet scrubber or a wet electrostatic precipitator located after the condensing heat exchanger. The choice of particulate control equipment depends on the degree of control required. The particulate slurry collected by the scrubber or precipitator is circulated through a pug mill that de-waters and pelletizes the ash. The ash pellets are spread on the tree fields as a fertilizer. The ash content of the wood is less than 1% so that a maximum of 5 t/day are collected and pelletized. The particulate emission standard to be met for new wood fired power plants in the State of Wisconsin, for exan le, is based on best available control technology (BACT) and can be expected to be about 21 g/ 10 kj. 

As the ash content of different biomass could influence the gasification reactivity of biomass chars, a study has been conducted to determine the influence of heavy metals on the gasification process [6]-[7]. They show that the alkali metals increase the reactivity of wood char and that lead, copper and zinc, especially as chlorides, inhibited the gasification of the char (about 2.5 times slower that the char fromtmtreated wood). 

Under the effect of carbonisation catalysts, the thermal decomposition of wood components sets in at a temperature approximately by 100°C lower than in the case of non-catalysed carbonisation of wood. Table 1 lists the yield of the wood carbonisation solid residue recalculated on fixed carbon to exclude the effect of the fluctuations of volatiles and the ash content upon the charcoal yield. The fixed carbon content of charcoal in the experiments represented in Table 1 was 78% to 81%. The increased ash content of charcod was caused by the catalysts, (NH4)2HP04 and ZnCb. The yield and overall heating value of the volatile (xoducts are given in Table 1. 

Holocellulose is the total carbohydrate content of wood. The values here are 100 — (the sum of percent ash, EtOH/benzene solubles, hot-water solubles, and lignin). Values from Refs. 73 and 76 were experimentally determined. 

Purity The purity of activated carbon is essential for the performance of the final catalyst. Impurities of activated carbon originate from the raw material and the process conditions. Ash contents of up to 20% can be possible. Wood-based activated carbons have ash contents as low as 1 wt% [7]. The ash content can be lowered further by acid treatment of the activated carbon [8]. Typically, the ash consists of alkaline and alkahne earth metal oxides, silicates, and smaller amounts of other compounds (e.g., iron). The presence of the alkaline and alkaline earth metal oxides makes those carbons more basic in nature, so that some additional adjustments are necessary during catalyst manufacturing to meet the constant quality requirements. Since the supports are used in catalysts, the presence of catalytically active compounds that could have a potential influence on the performance of the final catalyst has to be considered as well. For the manufacture of catalysts, activated carbon based on wood, peat, nut shells, and coconut are commonly used. Due to a relatively high sulfur content in activated carbons derived from coal, those carbons are typically not used as catalyst support. 

Other tree components, such as foliage and bark, contain a substantially higher content of extractives, and a slightly higher ash content than wood. Also, bark has a higher content of phenolics other than lignin, including phenolic acid and tannins as compared to wood. 

The wood structure after long immersion—which, in the case of archaeological wood, may be hundreds or thousands of years—is swollen. The lignin and ash content of the wood increases relative to the cellulosic portions as immersion time increases. The skeleton of waterlogged, swollen lignin and any remaining cellulosics has free water within the cells. This water is strengthening and prevents collapse. 

Recently experiments were performed on nests of the hornet Vespa crabro and of several wasps by means of combustion calorimetry and DSC, TG/DTG and MS. The ash content of most nests is small (about 3 %) comparable to that of wood (see above) with the exception of nests of the wasp Dolichovespula (7 4 %). In contrast to wood with more than 50 % (fresh) and about 20 % (dry) the water content of wasp nests is extremely low with only 3.6 %. This is of special importance for the insulating properties of the envelope. The combustion energy with values between -16 and -18 MJ/kg corresponds to that of wood [120]. 

Chemical Composition. Chemical compositional data iaclude proximate and ultimate analyses, measures of aromaticity and reactivity, elemental composition of ash, and trace metal compositions of fuel and ash. All of these characteristics impact the combustion processes associated with wastes as fuels. Table 4 presents an analysis of a variety of wood-waste fuels these energy sources have modest energy contents. 

The ash content is 0.2—0.5% by weight for temperate woods and 0.5—2.0% by weight for tropical woods. The principal elemental components of wood ash are calcium and potassium with lesser amounts of magnesium, sodium, manganese, and iron. Carbonate, phosphate, sUicate, oxalate, and sulfate are likely anions. Some woods, especiaUy from the tropics, contain significant amounts of sUica. 

Charcoal—sulfur processes need low ash hardwood charcoal, prepared at 400—500°C under controlled conditions. At the carbon disulfide plant site, the charcoal is calcined before use to expel water and residual hydrogen and oxygen compounds. This precalcination step minimises the undesirable formation of hydrogen sulfide and carbonyl sulfide. Although wood charcoal is preferred, other sources of carbon can be used including coal (30,31), lignite chars (32,33), and coke (34). Sulfur specifications are also important low ash content is necessary to minimise fouling of the process equipment. 

Almost all fiber and partial titanium dioxide can be recovered from white water by DAF under full flow pressurization mode43 with chemical addition. On June 10, 1982, at Mead Corporation, pulp was prepared with 40% cotton fiber and 60% wood fiber. The loading of titanium dioxide was about 50% (i.e., 273 kg Ti02 per 600 kg total pulp). The white water from No. 2 machine was fed to a DAF cell (diameter = 3 m) at 15.8 L/s (250gal/min) under full flow pressurization mode. Turkey red oil (TRO) was dosed as a flotation aid at 80mL/min. The influent white water (before TRO addition), DAF effluent, and floated scum were sampled for analysis. The DAF influent had 98 mg/L of TSS, and 650 NTU of turbidity at pH 9.27. The DAF effluent had 15 mg/L TSS and 550 NTU of turbidity at pH 9.25. Although TSS (fiber and titanium dioxide) recovery rate was 85%, the ash content (titanium dioxide) of the recovered TSS was very low. Therefore, using a DAF clarifier under full flow pressurization mode and TREO, the majority of fibers in white water but only about half of titanium dioxide can be recovered. 

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