Introduction to Crude Palm Oil (CPO) Dilution

            Control of crude oil dilution has been a formidable problem in process control for palm oil mills. This is due mainly to the difficulty in selecting a suitable flow meter for crude oil measurement, as crude oil is a non Newtonian, thixotropic fluid which cannot be measured using ordinary differential pressure flow meters. As the oil loss in ex-clarification processes is a major source of oil loss in the overall milling operation, there ia an urgent need to improve the control of crude oil dilution to achieve better oil recovery efficiency.

            Before introducing any automatic control system for crude oil dilution, it is necessary to evaluate the available measurement and control instruments for their suitable in terms of cost, accuracy and reliability for the palm oil mill.

            Basically dilution are required by most of palm oil mill to reduce viscosity of palm oil after been pressed. By applying right percentage of dilution it will result effective separation during clarification.

            Normally hot water at 85⁰C of sterilizer condensate been apply as dilution and there are few point of dilution been dose to crude oil passing through pressing machine. Below are few point of dilution point been dose.

(a)  Oil gutter, under press machine

(b)  Press cage

(c)  Digester steam

(d)  Digester discharge chute

(e)  Sand trap

(f)   Crude oil tank open steam coil

(g)  Vibrating screen

            There are various practice for applying dilution to crude oil prior clarification station, such as V notch, orifice plate and insulating valve. Poor dilution will cause poor oil separation at clarification and cause high oil loss at clarifier tank underflow, it also might cause diluted crude oil overflow from oil gutter and sand trap tank due to high viscosity, for certain case it will overload at vibrating screen and screen waste will be oily.

1.2       Important of right dilution rate.

            The main objective of the clarification and centrifuging processes is to separate as much oil as possible from the diluted crude oil. Illustrate conclusively that the optimum oil settling rate for crude oil is achieved with approximately 25% to 35% of water dilution to dilute crude oil. Manual control of crude oil dilution has been found to be highly unsatisfactory due to the following reason.

(a)  High variation in crude oil flow rate due to intermittent operation of the presses.

(b)  Throughput variation in the operation of presses due to varying crop quality and weather pattern. To achieve the required result, it is obviously necessary to look into the possibility of using automatic control of crude oil dilution.

            Good dilution will produce lower oil loss at clarifier tank underflow and effective separation within oil water and solids, it can be verified at sand trap tank, we will be able to see oil sells size of 50 cent coin floating and merge with bigger oil cells. Table below shows some comparison within good and poor dilution by physical view.

No	Good Dilution Rate	Low  Dilution Rate	High Dilution Rate
1.	Oil will flow smoothly at oil gutter and sand trap tank.	Oil will overflow at oil gutter due to greater viscosity.	Oil will flow faster without any oil at top surface.
2.	Able to see oil cell size of 50 cent coin floating to top surface at sand trap tank.	Only fine oil cell will float and level of sand trap tank will increase due to increase of viscosity.	Sign of emulsification at top surface of sand trap tank.
3.	Smooth distribution of screen waste at vibrating screen mash.	Most of screen waste will accumulate at middle of vibrating screen and will cause overloading at screen mash.	Screen waste will travel fast at screen mash and inlet feeding feed will looks watery.
4.	Good separation and clarifier tank with low oil loss at sludge underflow.	Will cause high oil loss at clarifier underflow, Low moisture content but high NOS.	Will also cause high oil loss at clarifier tank underflow, emulsify sign at top of oil surface, high moisture contain but low NOS contain.

Table 1.1: Comparison within  dilution rate.

            Below are some pictures shows physical condition of good dilution rate and poor dilution rate, all pictures and situation are base on my Mill condition and process flow.

Figure 1.1: Picture of low Dilution 

Figure 1.2: Picture of good dilution rate.

Figure 1.3: Picture of good dilution, view from sand trap tank.

Dilution rate are normally determined by type of planting material and weather changes, during high rain fall dilution rate should be lower and during dry season dilution rate should be higher. Table below shows dilution rate for Genting Trushidup Oil mill by comparing with rain fall (mm) for average per day for two weeks period.

No	Rain fall (mm)	Dilution rate (%)
1.	0-7	27
2.	8-20	25
3.	21- 35	22
4.	35-85	20

Table 1.2: Correlation within rainfall and dilution rate

            From table above, it is extracted base on Genting Trushidup Oil Mill data study that been updated on December 2011. It obviously shows rain fall are correlated with dilution rate and if been plotted in graph it reacted against both units.

1.3       How to determine best dilution rate.

            In order to determine the best dilution rate for each mill we need to carry out settling test, sample of undiluted crude oil bust be taken at right place with all source of water must be eliminated, objective of this test are to check with what dilution rate, crude oil will settle base on fasters time, temperature of this test must be same as clarifier tank, for Genting Trushidup Oil Mill case we are applying 85⁰C and test been carry out for 10 minutes.

Figure 1.4 : Settling test

Content	20% Dilution	22% Dilution	25% Dilution
Oil (mm)	20	25	18
Sludge (mm)	70	68	65

Table 1.3: Settling test data

            Picture 1.4 shows how settling test been carry out, 3 bikers with 500ml been place with 20%, 22% and 25% dilution and undiluted crude oil been place in it, retention time for this test are 10minutes.

            After 10 minutes, measure the high of oil settled and high of sludge, from table 1.3 it shows 22% dilution is the most suitable to be implemented at process during this period, during this test been carry out, need to ensure temperature are the same as clarifier tank temperature.

            Dilution rate might not be same with other oil mill and even at same mill it will slightly increase or reduce depends on weather, planting materials and FFB quality.

Figure 1.5: picture of over dilute DCO.