Liquid Biofuels. Группа авторов

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СКАЧАТЬ 2.2 mostly deals with homogenously catalyzed transesterification process and rarely addressed the heterogeneously catalyzed system for biodiesel production.

Table 2.2 Hydrodynamic cavitation reactors assisted biodiesel synthesis case studies.

Oil (source)	Catalyst	Molar ratio (Methanol to oil)	Catalyst loading (wt% or w/w)	Reaction temperature (K)	Time (min)	Design of HC reactor (Cavitation chamber details, pressure)	% FAME (yield)	Reference
Thumba oil	TiO2-Cu2O nanoparticles	6:1	1.6%	353	60	Orifice – 2 mm and 20 holes; 2 bar pressure	65	[91]
Cannabis sativa L. oil	KOH	6:1	1%	333	20	Orifice – 3 mm and 7 holes; ~ 15 bar pressure	97.5	[92]
Waste cooking oil	NaOH	6.8:1	1%	308	5	Orifice – 0.3 mm and 100 holes; 7 bar pressure	99	[93]
Waste frying oil	KOH	6:1	1.1%	336	8	Venturi apparatus; 3.27 bar pressure	95.6	[94]
Used frying oil	KOH	4.5:1	0.55%	318	20	Orifice – 3 mm and 16 holes; 2 bar pressure	93.86	[95]
Rubber seed oil		6:1	1%	328	18	Orifice – 1 mm and 21 holes; 3 bar pressure	96.5	[96]
Waste cooking oil	KOH	12:1	3%	323	120	High speed homogenizer (1200 – 3500 rpm)	97	[97]
Waste cooking oil	KOH	6:1	1%	333	15	Orifice – 1 mm and 21 holes; 2 bar pressure	98.1	[98, 99]
Nagchampa oil	KOH	6:1	1%	333	20	Orifice plate; 1.4 bar pressure	91.8	[100]
Used frying oil	KOH	5:1	1%	333	10	Orifice – 2 mm and 25 holes; 2 bar pressure	95	[26]
Thumba oil	NaOH	4.5:1	38 g	323	30	Orifice – 3 mm and 5 holes; 1.5 bar pressure	80	[101]

      The next section deals with the quantification of cavitational zonesbased analysis for the efficient design of hydrodynamic reactors.

2.4 Designing the Cavitation Reactors

      As discussed in the previous sections, the chemical and physical effects of a cavitational phenomenon will be able to initiate as well as promote various chemical reactions. Thus, to design an efficient cavitational or sonochemical (either acoustic or hydrodynamic cavitation) reactor, one must be able to produce a cavitation zone, i.e., the area in the reactor in which formation, growth and the transient collapse of tiny bubbles should occur. Hence, the measurement of cavitation zone as well as cavitational intensity will ultimately impart the effectiveness of a selected cavitational reactor design. Along with cavitational intensity, analysis of pressure difference is also done, which leads to the development of a high number of cavitational bubbles and increases the impacts of physical effects of cavitational phenomena (especially in the case of a hetero-phasic reaction system). Moreover, application of either acoustic (either probe or ultrasound bath) or hydrodynamic (either orifice or venturi based) cavitational reactors is typically based on the size of reactants processed. In the following paragraphs, the basic methodology to determination of cavitational intensity in both cases is discussed elaborately.

As a standard procedure in chemical engineering practice, the lab-scale kinetics data is used to design a specific reactor followed by dimensional analysis; the design approach for a cavitational reactor will need an estimation of cavitational effects on the reaction mixture and variation of pressure amplitude throughout the reactor geometry. Gogate et al. [89] reported the methods commonly used to measure the variation in pressure amplitude and cavitational intensity. In this study, Gogate et al. [89] also reviewed the literature published in analyzing the cavitation intensity using an experimental- and mathematical-based approach. The authors reported the use of hydrophones to measure the variation of pressure amplitude experimentally. The obtained readings can be compared to the simulated (i.e., mathematically model-based) results to determine the efficiency and energy dispersion into the liquid under operating conditions. To estimate the chemical effects of cavitation, i.e., the formation of free radicals, authors suggested using degradation of potassium iodide as a model reaction. The quantity of iodine gas liberated can be measured using the UV/VIS spectrophotometer (measuring absorbance at a wavelength of 355 nm) [87, 89]. The cavitational yield for a given design and particular model reaction could be determined using the following equation [88]:

      (2.1)

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