Process parameters liquid products composition

Details of the tantalum and niobium extraction process depend on the type of raw material used, decomposition method, initial solution composition, extractant type, equipment specifications, type of final products and desired purity. Therefore, process parameters are usually defined individually for each specific case. This may be the reason for the existence of the wide variety of publications devoted to the liquid-liquid extraction of tantalum and niobium. Nevertheless, some common features of the process should be emphasized. 

Some regularities describing the influence of co-pyrolysis process operating parameters, nature of wood biomass and plastics on the yield and composition of liquid products were established and discussed. Obtained data indicate that the optimum ten erature of biomass/plastic mixtures conversion which corresponds to the maximum yield of liquids is 390-400 C. 

In wood pyrolysis, it is known that several parameters influence the yield of pyrolytic oil and its composition. Among these parameters, wood composition, heating rate, pressure, moisture content, presence of catalyst, particle size and combined effects of these variables are known to be important. The thermal degradation of wood starts with free water evaporation. This endothermic process takes place at 120 to 150 C, followed by several exothermic reactions at 200 to 250°C, 280 to 320 C, and around 400 C, corresponding to the thermal degradation of hemicelluloses, cellulose, and lignin respectively. In addition to the extractives, the biomass pyrolytic liquid product represents a proportional combination of pyrolysates from cellulose, hemicelluloses. 

The composition and relative amounts of the products formed are dependent on process parameters such as heating rate, pressure, coal type coal (and product) residence time, coal particle size, and reactor configuration. A major disadvantage of this type of process is the large yields of char (Table 18.2) that markedly reduce the yield of liquid products. 

Mixed copper/zinc catalysts with high copper-to-zinc ratios are widely used as catalysts for low-pressure methanol production and for low-temperature shift reaction [2, 31], see also Chapter 15. These catalysts are commonly made by coprecipitating mixed-metal nitrate solutions by addition of alkali. Li and Inui [32] showed that apart from chemical composition, pH and temperature are key process parameters. Catalyst precursors were prepared by mixing aqueous solutions of copper, zinc, and aluminum nitrates (total concentration 1 mol/1) and a solution of sodium carbonate (1 mol/1). pH was kept at the desired level by adjusting the relative flow rate of the two liquids. After precipitation was complete, the slurry was aged for at least 0.5 h. When the precipitation was conducted at pH 7.0, the precipitate consisted of a malachite-like phase (Cu,Zn)C03(0H)2 and the resulting catalysts were very active, while at pH < 6 the formation of hydroxynitrates was favored, which led to catalysts less active than those prepared at pH 7.0 (Figure 7.8). 

The method used to contact the alloys and the sulphates did not greatly influence the final distribution of metals between oxidation products. The most irrpcrtant characteristics determining the processing parameters were the sulphate composition and the initial conposition of the alloys. The average total oxidation rates of conponents were close to previous values [3] and were satisfactorily described by a equation characterising the processes with a predominant role for mass transfer in the liquid phase ... 

The Underwood equation system determines separation product compositions and internal liquid and vapor flows in the sections for the set values of two parameters, characterizing the separation process. The reflux number R and withdrawal of one of the products D/F or recoveries of some two components into the top product = di/fi and = dj/fj, etc., can be chosen as such two parameters. For example, at direct split of three-component ideal mixture 1(2) (1)2,3 (here the top product contains component 1 and small admixture of component 2 and the bottom product contain components 2,3 and small admixture of component 1), Eq. (5.3) has only one common for both section root U2 < 0 < ai. If f i and 2 are set, then di and d2 can be defined and 1 " can be obtained from Eq. (5.1). The rest of internal flows in the column section can be defined with the help of the material balance equations. 

The design of a proper drying process should guarantee a high level of active enzyme. Generally, enzyme activity after drying is a function of the composition of the initial liquid to be dehydrated, the process parameters, and the physicochemical characteristics of the enzyme [2], so that drying of each enzyme product should be considered on an individual basis. 

Knowledge of the effects of various independent parameters such as biomass feedstock type and composition, reaction temperature and pressure, residence time, and catalysts on reaction rates, product selectivities, and product yields has led to development of advanced biomass pyrolysis processes. The accumulation of considerable experimental data on these parameters has resulted in advanced pyrolysis methods for the direct thermal conversion of biomass to liquid fuels and various chemicals in higher yields than those obtained by the traditional long-residence-time pyrolysis methods. Thermal conversion processes have also been developed for producing high yields of charcoals from biomass. 

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