Liquid Biofuels. Группа авторов

mechanical agitation. Gude and Martinez-Guerra [39] assessed the process of intensification in sustainable biodiesel production using a green chemistry approach. They compared the reaction efficiency between the conventional mechanical agitation, microwave, and ultrasound-enhanced biodiesel synthesis.

      The literature published on cavitation-assisted biodiesel synthesis can be categorized based on the type of cavitation employed, viz., acoustic cavitation and hydrodynamic cavitation.

      2.3.1 Acoustic Cavitation (or Ultrasound Irradiation) Assisted Processes

These are essentially lab-scale studies that have reported the role of ultrasound for intensifying the yield of the reaction. The ultrasound has been applied either through direct mode, i.e., with the ultrasonic probe or indirect mode, i.e., ultrasonic bath. The comparative analysis of some important studies using different feedstocks and catalyst in the presence of acoustic cavitation is summarized in Table 2.1.

      2.3.2 Acoustic or Ultrasonic Cavitation Assisted Processes

Hydrodynamic cavitation is a sub-type of cavitation technology with a wide range of applications that include biodiesel production. The studies utilized the hydrodynamic cavitation (HC) reactor for biodiesel synthesis with reactor capacity varying from 5 L/h to 100 L/h and hence, also considered as pilot-scale studies [86]. The application of HC reactors for biodiesel production at commercial scale is preferably sensible compared to acoustic cavitation-based reactors. The major advantage of HC reactors’ usage over acoustic cavitation reactors is the lower energy and solvent consumption to process a large quantity of feedstock [87]. The design-based approach of HC reactors is discussed explicitly in the next section. At present, the basic principle of HC is briefly explained. When a liquid flow is altered by passing the liquid through either a venturi or an orifice plate, it results in enhanced fluid velocity across the region of vena contracta by losing the local pressure. If this pressure fall is achieved below the threshold pressure value, it results in the formation of cavitational phenomena, i.e., growth of tiny bubbles. The consequent transient collapse of these tiny bubbles, which occurs in the expansion phase of liquid, resulted in the completion of the cavitation process [88]. A typical configuration of HC reactor mainly consists of a feed tank, a pump (preferably reciprocating pump), pressure gauges, and the cavitation chamber – either in the form of venturi or an orifice plate or throttling valve. Among these three, the orifice plates are used more often for the efficient performance of the HC reactor as the pressure drop is much higher, and extended cavitation zone can be achieved with orifice plates with different geometry of holes (orifices) [28, 87, 89, 90]. In this section, the literature available for biodiesel production using the HC reactor is summarized in Table 2.2. This will give a comprehensive analysis of various studies and reaction parameters used to optimize the biodiesel yield in each case.

Table 2.1(A) Ultrasound-assisted heterogeneously base catalyzed biodiesel synthesis case studies.

Oil (source)	Catalyst	Molar ratio (Methanol to oil)	Catalyst loading (wt% or w/w)	Reaction temperature (K)	Time (min)	Ultrasonic frequency/power (kHz/W)	% FAME (yield)	Reference
Mixed oil	KI/ZnO	11.68:1	7%	332	60	35/35	92.35	[22]
Soybean oil	Barium polymer	12:1	6%	338	150	37/100	99	[40]
Waste cooking oil	ZnO	6:1	1.5%	333	15	32 kHz	96	[41]
Canola oil	CaO, Ca-diglyceroxide	7.48:1	5.35%	333	150	20/40	99.4	[42]
Karbi oil	CaO	12:1	5%	333	120	20-30/50	94.1	[43]
Soybean oil	Sodium Zincronate	6:1	3%	328	480	25/360	80	[44]
Mixed oil	Cu2O	10.6:1	7.25%	335.5	40	35/35	98.33	[21]
Refined Palm oil	CaO	9:1	8%	323	37	28/200	95	[45]
Canola oil	Dolomite	9:1	5%	333	90	20/45	97.4	[46]
Palm oil	CaO	9:1	2%	333	3.5	20-50/800	80	[47]
Waste cooking oil	Hydrotalcite	15:1	0.08 g/g oil	330	60	20/11	76.45	[48]
Waste cooking oil	Coal fly ash	10.71:1	4.97%	333	Скачать книгу В начало < 22 23 24 25 26 27 28 29 30 31 > В конец