Solid Byproducts

Solid by-products of gasification and combustion processes are significantly different. The primary solid by-product of a low-temperature gasification process is char. Char consists of unreacted carbon and the mineral matter present in the gasifier feed. The most important and significant use of char is as a source of activated carbon. 

Char from a variety of sources, including coal, is used to produce activated carbon. The two most important uses for activated carbon are for water and wastewater treatment and decolorization. Other uses for activated carbon include the capture of pollutants such as volatile organic compounds (VOCs) and pesticide residues from industrial waste streams. 

Other markets for char include iron, steel, and sili-con/ferro-silicon industries. Char can be used as a reducing agent in direct reduction of iron. Ferro-silicon and metallurgical-grade silicon metal are produced carbothermally in electric furnaces. Silica is mixed with coke, either iron ore or scrap steel (in the case of ferro-silicon), and sawdust or charcoal in order to form a charge. The charge is then processed by the furnace to create the desired product. Char can be substituted for the coke as a source of reducing carbon for this process. Some plants in Norway are known to have used coal-char in the production of silicon-based metal products as late as mid-1990.5 The use of char in this industry is not practiced due to lack of char supply. 

The primary solid byproduct of combustion processes is bottom ash, which primarily consists of mineral matter and minor amounts of unreacted carbon. Because the leaching property of the ash, the bottom ash from combustion of most material is considered hazardous. An exception is the bottom ash from combustion of biomass. 

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The process involved consists of 5 consecutive steps. The first step involves a reaction which forms an arsenate salt. This reaction requires two raw materials, raw 3 and raw 4, and can be conducted in either reactor R1 or R2. The arsenate salt from the first step is then transferred to either reactor R3 or R4 wherein two reactions take place. The first of these reactions is aimed at converting the arsenate salt to a disodium salt using raw material 1 (raw 1). The disodium salt is then reacted further to form the monosodium salt using raw material 2 (raw 2). The monosodium salt solution is then transferred to the settling step in order to remove the solid byproduct. Settling can be conducted in any of the three settlers, i.e. SE1, SE2 or SE3. The solid byproduct is dispensed with as waste and the remaining monosodium salt solution is transferred to the final step. This step consists of two evaporators, EV1 and EV2, which remove the excess amount of water from the monosodium solution. Evaporated water is removed as effluent and the monosodium salt (product) is taken to storage. States si and. S 9 in the SSN represent raw 3 and raw 4, respectively. States... 

Allyl bromide (3 4.4 mL, 6.1 g, 0.05 mol) was added dropwise to a stirred solution of tris(pyrrolidin-l-yl)sulfonium difluorotrimethylsilicate (2 7.1 g, 0.2 mol) in anhyd MeCN (5 mL), and the reaction was stirred at rt for 2 h. The volatiles were distilled into a dry-ice trap from the solid byproduct tris(pyrrolidin-l -yl)sulfonium bromide. The distillate was fractionated through a low-temperature microcolumn to give the title compound yield 1.0 g (83%) bp — 3 to 0"C. 

Loin, L. Managing Solid Byproducts of Industrial Food Processing, Food Review, 21 (April-Juiie 1991). 

Incineration is often regarded as a very efficient technique for municipal solid waste (MSW) management. However, the environmental impacts of MSW incineration need to be carefully taken into account. The most relevant problem with MSW incineration is flue gas treatment. However, another often overlooked issue is the disposal of solid byproducts of the incineration process. MSW incinerators essentially produce two types of solid by-products, that is, slag, or bottom ash, and fly ash, often mixed with various other chemicals used for flue gas treatment. Bottom ash and—even more—fly ash are regarded as dangerous wastes mainly due to their potentially toxic elements (PTE) content and their tendency to leach such PTE to the environment. 

For the ozonolysis of linear alkenes only alk-l-encs should be used to avoid product mixtures as the resulting formaldehyde or formic acid are readily separated. This type of reaction is also a successful method for the preparation of perfluorinated carboxylic acids.The advantage over the oxidation with potassium permanganate is that the process does not form solid byproducts which are diflicult to separate. A disadvantage of this procedure is the fact that two reaction steps arc needed to obtain the required product. 

Both reactants are soluble in organic solvents and are drop-wise mixed. In contrast to the synthesis by ammonolysis of the respective tris(chloro-silylethyl)boranes, no solid byproducts form the only byproduct is dimethylsulfide which can be easily removed, together with the solvent by vacuum distillation. Moreover,... 

Dust removal is crucial for long production runs with a high selectivity level. The fines removed via the cyclones contain a lot of the copper catalyst. For economic reasons and low environmental impact it is neccessary to recover the copper catalyst from solid byproducts and utilize unconverted silicon in external processes, like the production of ferroalloys [10]. 

In some cases, acid scavenging is not used to stop further reactions of the acid, but to shift an existing equilibrium to the favored side. This is true for elimination reactions or the formation of ylids that are further used in Wittig reactions. Hydrochloric acid (HCI) is the acid most commonly formed. Usually, tertiary amines such as triethylamine are added to scavenge the acid. With the acid, these substances form solid salts which turn the reaction mixture into a suspension. The solid byproduct must then be removed. This can be done via a filtration step which requires expensive equipment, especially for precipitates vrith high filter resistances or continous filtration. If the product is inert to and insoluble in water, one can dissolve the solid by adding water to the reaction mixture, and remove the organic phase by a simple liquid-liquid separation. If the product is sensitive to acids and moisture, until now only filtration was left as a suitable means. 

Raw materials The successful introduction of a selective blend of solid byproduct wastes into the feedstock replacing quarried raw materials has an immediate effect The lesser the use of primary raw materials the lesser the environmental footprint of a production process. 

A number of engineered systems have been used to effect high heat transfer into the biomass particle and quick quenching of the vapor product, usually after removal of solid byproduct char , to recover a single phase liquid product. 

Other types of biomass pyrolysis oil produced under less specified conditions, typically longer residence time or lower temperature, will have a different chemical composition and will therefore have different chemical and physical properties. Such Uquids will also be produced in lower yields in conjunction with higher gas and solid byproducts. The hydroprocessing described in this chapter has been developed to address the properties of fast pyrolysis bio-oil. A more detailed discussion of fast pyrolysis can be found in chapter Catalytic fast pyrolysis for improved liquid quality . 

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