Vegetable Oil Refining, Biodiesel, and Oleochemical Conversion

5 Integration into Vegetable Oil Refining

5.1 General integration architecture

A robust installation separates four functions: accurate reagent metering, intense but brief contact, controlled chemical or biological hold, and phase separation. The oil flow must be stable, and the reagent concentration must be verified. The hold vessel provides time for hydration, acid conversion, enzyme action, neutralization, floc development, or coalescence. The separator must receive a droplet and floc distribution within its hydraulic and solids loading capacity.

Table 5.1. Stage specific objectives and acceptance endpoints.

Stage	Contacted phase	Primary endpoint	Downstream constraint
Water degumming	Water in crude oil	Residual phosphorus at equal or lower water dose	Hydrated gums must aggregate without high neutral oil loss
Acid or deep degumming	Acid followed by water or base	Phosphorus, calcium, and magnesium	Adequate acid conversion and hold before centrifugation
Enzymatic degumming	Enzyme in aqueous microphase	Enzyme dose or time at equal phosphorus and yield	Enzyme activity, pH, temperature, and separation
Alkali neutralization	Caustic contacting free fatty acids and residual acid	Free fatty acids and soap at lower caustic excess	Avoid triglyceride saponification and oil entrainment
Water washing	Wash water contacting soap and salts	Soap and salts at reduced water use	Avoid stable surfactant rich emulsion
Adsorbent dispersion	Bleaching earth, silica, or carbon	Color, metals, and phosphorus at lower dose	Avoid particle fragmentation and filter resistance

5.2 Water degumming

Water degumming consists of heating crude oil, metering water, mixing, providing a hydration hold, and separating the heavy gum phase. Cavitation can distribute water rapidly and reduce the distance a phospholipid molecule must travel to reach an interface. The endpoint is not fine water dispersion. It is low residual phosphorus, rapid gum separation, low moisture in oil, and low neutral oil in gums [2,3].

Development should begin with a conventional baseline at the same feed, water dose, temperature, hold, and centrifuge setting. Cavitation should be introduced at low dose and one pass. Water or hold time should be reduced only after the baseline phosphorus and oil recovery are matched. Too much water increases the heavy phase volume, drying duty, wastewater, and emulsion stability. Cavitation changes contacting but does not remove the chemical optimum for water dose.

5.3 Acid and deep degumming

Acid degumming converts metal associated phospholipid forms into more hydratable or extractable species. Phosphoric and citric acids are common choices. Because acid dose is small relative to oil flow, distribution is critical. A fine acid dispersion can complete conversion rapidly, but adding acid and all hydration water before an excessively intense device can produce a stable acidic emulsion. Practical sequences include acid contact followed by an acid hold and later water addition, diluted acid and water contact in one stage, or separate contact stages with different doses.

The stoichiometric acid requirement depends on the measured calcium, magnesium, residual base, and phospholipid chemistry. A compact general expression is:

Here $n_i$ represents the amount of each neutralized or complexed species and $n_{acid,st}$ i is the acid stoichiometric coefficient. In practice, online flow control is combined with frequent phosphorus, calcium, magnesium, and acid strength measurements. A low outlet phosphorus value obtained by transferring excessive neutral oil to the heavy phase is not an economic improvement.

*Figure 5.1. Patent disclosed degumming sequence with acid conditioning, base addition, cavitation, hold, and separation. [15].*

5.4 Enzymatic degumming

Enzymatic degumming uses phospholipases to convert phospholipids to products with improved hydration, separation, or oil yield. Phospholipase A forms a lysophospholipid and a free fatty acid. Phospholipase C can release diacylglycerol and a water soluble phosphorylated head group. The selected enzyme changes both the chemistry and the yield accounting. A simplified phospholipase A reaction is:

The enzyme acts at an oil water interface. Cavitation can increase interfacial accessibility, but enzymes can lose activity under excessive temperature, repeated shear, interfacial stress, or recirculation. The correct comparison is lower enzyme dose or shorter hold at equal final phosphorus, metals, oil yield, and enzyme activity.

Results from enzymatic refining trials, conducted with an initial phosphorus content of 322 mg/kg, showed that when cavitation was employed during the addition of the enzyme and water, phosphorus levels measured 59, 30, 26, and 21 mg/kg after 0, 30, 60, and 90 minutes, respectively. For comparison, without the use of cavitation, these figures were 96, 73, 60, and 88 mg/kg. Results from a series of experiments are also reported in which phosphorus content decreased from over 325 mg/kg to 84 mg/kg, calcium from over 160 mg/kg to 66 mg/kg, and magnesium from over 70 mg/kg to 14 mg/kg [16].

*Figure 5.2. Data for enzymatic degumming with and without cavitation. [16].*

*Figure 5.3. Representative enzymatic degumming architecture showing acid conditioning, enzyme and water addition, cavitation contacts, short holds, heating, and separation [10].*

Table 5.2. Reported enzymatic degumming screening data. [16].

Condition and time	Phosphorus, mg/kg	Calcium, mg/kg	Magnesium, mg/kg	FFA, percent
Incoming	322	167	70	0.63
Cavitation, 0 min	59	35	10	0.59
Cavitation, 30 min	30	20	5	0.74
Cavitation, 60 min	26	18	4	0.74
Cavitation, 90 min	21	14	3	0.73
No cavitation, 0 min	96	52	15	0.58
No cavitation, 30 min	73	40	11	0.74
No cavitation, 60 min	60	33	9	0.64
No cavitation, 90 min	88	40	14	0.72

A final process scheme was also proposed, involving treatment at 70°C using a 50% citric acid solution (at a dosage of 1300 mg per kg of raw material) and an enzyme (30 mg per kg), along with the addition of 2.5% water and the application of multiple cavitation cycles; notably, the total duration of the enzymatic treatment was less than one hour, in contrast to traditional methods, where it can take up to six hours. It is particularly noted that this process has not been optimized; therefore, the presented data should be viewed as a working hypothesis rather than a guaranteed recipe [16].

5.5 Compression and decompression cavitation degumming example

US 9,321,983 B2 discloses acid and base pretreatment followed by compression and rapid decompression cavitation. In one example, measured residual phosphorus decreased from 46 to 2.3 mg per kg, iron from 0.8 to 0.05 mg per kg, calcium from 35 to 2 mg per kg, and magnesium from 8 to below the reported detection value. The process used repeated decompression intervals after pressurization. [11].

*Figure 5.4. Trace impurity reductions reported for compression and decompression cavitation degumming [11].*

Table 5.3. Patent example for compression and decompression degumming [11].

Analyte	Initial, mg/kg	Final, mg/kg	Calculated reduction
Phosphorus	46	2.3	95.0 percent
Iron	0.8	0.05	93.8 percent
Calcium	35	2	94.3 percent
Magnesium	8	reported as 0	approximately 100 percent

5.6 Alkali neutralization and water washing

Chemical refining removes free fatty acids (FFAs) from crude oils by reacting them with sodium hydroxide (caustic soda) to form soapstocks (Equation 5.3):

The theoretical mass of sodium hydroxide for neutralizing free fatty acids can be estimated from:

The excess factor is:

Rapid micromixing can reduce local concentration peaks and allow the excess factor to approach unity. The risk is direct: once free fatty acids and residual acid are neutralized, continued high interfacial area can increase triglyceride hydrolysis and saponification. The process should combine accurate free fatty acid measurement, verified caustic strength, ratio control, short contact, a defined hold, and timely separation.

*Figure 5.5. Neutralization converts free fatty acid to soap, while excessive local caustic concentration or long contact can consume neutral oil. [2,15,17].*

US 9,765,279 B2 discloses multiple localized shear cycles with millisecond relief intervals. The disclosed table demonstrates that nozzle size, stage count, shear rate, and time between cycles changed phosphorus, free fatty acid, and heavy phase volume. The strongest disclosed phosphorus values were obtained with multiple stages, while an unsuitable configuration produced high residual phosphorus and a larger heavy phase [15].

Table 5.4. Selected neutralization results. [15].

Nozzle opening, mm	Stages	Approximate shear rate, 1/s	Heavy phase, vol percent	Phosphorus, mg/kg	FFA, percent
0.56	1	66,390	5.85	94.0	0.10
0.56	2	66,390	3.80	28.0	0.08
0.56	2	66,390	2.38	2.2	0.03
0.56	3	66,390	1.88	1.6	0.01
1.25	2	50,120	2.42	4.0	0.02
3.28	1	6,400	6.70	157	0.15

Water washing removes residual soap and salts after the first separator. The wash stage normally requires less intensity than the initial neutralization stage because soap concentration is high and interfacial stabilization is strong. A mild contactor may reduce wash water, but an intense device can create a wash emulsion that overloads the centrifuge. The wash endpoint should include soap, salts, moisture, light phase oil loss, and wastewater volume.

5.7 Reported refining results

The supplied refining presentations report industrial and trial data for several oil streams. One presentation reports, for corn, rapeseed, and soybean oils, reductions in acid dose of approximately 51.9, 37.7, and 24.4 percent; reductions in sodium hydroxide use of approximately 27.2, 57.2, and 26.7 percent; and soap reductions of approximately 69.5, 65.1, and 30.9 percent, respectively. Final phosphorus values were reported at 4 mg per kg for corn and 2 mg per kg for rapeseed and soybean oil [18].

*Figure 5.6. Reported single pass testing across corn, rapeseed, and soybean oil streams. [18].*

Table 5.5. Data from multi oil refining results [18].

Oil	Acid reduction	NaOH reduction	Soap reduction	Final phosphorus
Crude corn oil	51.91 percent	27.22 percent	69.50 percent	4 mg/kg
Degummed rapeseed oil	37.70 percent	57.17 percent	65.14 percent	2 mg/kg
Degummed soybean oil	24.44 percent	26.66 percent	30.86 percent	2 mg/kg

Another presentation reports a commercial neutralization installation with acid reduction of 45 percent, caustic reduction of 25 percent, a 0.40 percent yield increase at the first centrifuge, elimination of wash water, a 15 mg per kg reduction in phosphorus, and a 500 mg per kg reduction in soap. The presentation reports annual savings of about USD 1.44 million and a simple payback of 0.43 years [19,20].

*Figure 5.7. Industrial Arisdyne controlled flow cavitation skid. [19,21]*

*Figure 5.8. Floc rich dispersion and visible phase separation after treatment. [19,21].*

5.8 Bleaching, winterization, and deodorization boundaries

Bleaching removes pigments, oxidation products, metals, soap, and residual phospholipids by adsorption onto activated clay, silica, carbon, or related media. Cavitation can improve wetting and break agglomerates, potentially reducing adsorbent dose. Excessive fragmentation can increase filter resistance and oil retained in spent earth. A trial should measure color, chlorophyll, phosphorus, metals, peroxide value, filter cycle time, spent earth oil, and pressure drop.

Winterization and dewaxing depend on controlled nucleation, crystal growth, and filtration. Cavitation can create nuclei but can also fragment crystals into fines that pass through or blind a filter. This application should be treated as exploratory and verified by crystal size distribution, cold test, haze, filterability, and oil loss. Hydrodynamic cavitation is not a replacement for steam deodorization. Its value is upstream removal of phosphorus, metals, soap, and oxidation precursors. Finished oil must still be evaluated for flavor, color, free fatty acids, trans isomers where relevant, tocopherols, sterols, peroxide value, p-anisidine value, and oxidative stability.