APPENDIX III

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Calculation of a two-stage extraction system at 30oBx

and comparison with measured results in a pilot plant

1. Date juice extraction in two stages at 30oBx (calculated).

Data given are:

        - Composition of dates (flesh)

            moisture (M): 20%
            soluble solids (SS): 70%
            non-soluble solids (NSS): 10%

        - Moisture content for presscakes (P)

            P1 = 62%)
                             )     empirical data
            P2 = 72%)

        - Date juice recovered 30oBx

        - Equilibrium in each extraction stage is reached

        - Non-soluble solids do not enter in juice, but remain in presscakes

        - No water or solid material is spilled in the process

In the extraction schedule below the underlined figures are known data. To facilitate calculation initially the following letter symbols are used (all on weight basis).

        water in S2 = a

        soluble solids in S2 = b

        water S3 = c

        water in P1 = w

        soluble solids in P2 = x

The figures in brackets are the result of the calculations.

Material Balance

 

OPERATION

 

MATERIAL

COMPOSITION (PERCENTAGE)

             M                                  SS                              NSS

WEIGHTS

         TOTAL                     H20                          SS                       NSS

Extraction Dates

Date Juice (S2)

20

(90.6)

70

(9.4)

10

0

100

a + b

(208.8)

20

a

(189.1)

70

b

(19.7)

10

0

  Slurry 1       100+a+b

(308.8)

20+a

(209.1)

70+c

(89.7)

10
Separation Date Juice (S1)

Presscake (P1)

70

62

30

(26.6)

0

(11.4)

12.4+a+b

(221.2)

 

(87.6)

a-34.3

(154.8)

w

(54.3)

46.7+b

(66.4)

x

(23.3)

 

0

 

10

Extraction Presscake (P1)

Water (S3)

62

100

(26.6)

0

(11.4)

0

(87.6)

c

(169.9)

(54.3)

c

(169.9)

(23.3)

0

10

 

0

  Slurry 2       87.6+c

(257.5)

54.3+c

(224.2)

(23.3) 10
 

Separation

Date Juice (S2)

Presscake (P2)

(90.6)

72

(9.4)

(7.4)

0

(20.6)

a + b

(208.8)

87.6+c-a-b

(48.7)

a

(189.1)

54.3+c-a

(35.1)

b

(19.7)

23.3-b

(3.6)

0

 

 

10

Calculation

Equilibrium is reached, hence Brix of the juice in the presscake P1 is the same as in recovered juice S1 (30o). It follows:

out of which x and w can be solved (x = 23.3; w = 54.3).

All other unknown components in weights can now be expressed in a, b and c.

- Since S1 is 30oBx and contains no soluble solids, it follows:

(equation 1)

- Juice in presscake P2 and Date Juice S2 are in equilibrium hence have the same Brix level, expressed as follows:

and

(equation 2) b

- Moisture content P2 is 72%, hence

(equation 3)

Three equations, three unknowns, a, b and c can now be solved:

a = 189.12 rounded 189.1

b = 19.655 rounded 19.7

c = 169.89 rounded 169.9

After having inserted these results in the schedule, all other unknowns can now be calculated and the material balance is completed.

2. Date juice extraction in two stages at 30oBx in date syrup pilot plant (Libya)

The extraction part of the pilot plant (about 50 kgs/hr date input) consists of two horizontal continuous extraction vessels in which dates and extraction liquid are in contact at 85oC for about hour whilst being sitrred. Separation between the stages consists of a combination of a vibratory screen followed by a twin expeller press. The performance data for the extraction were compiled by determining

a) weight and composition of dates
b) weight and composition of presscake P2
c) weight and composition of recovered juice, S1
d) composition of juice S2 by sampling during operation.

Material Balance

Operational

Material

Composition
%-age
   M         SS  NSS

Weights

Total        H20          SS     NSS

Extraction Dates

Date Juice (S2)

20

89.6

70

9.3

10

1.1

100

198.2

20

177.8

70

18.4

10

2.0

  Slurry       298.2 197.8 88.4 12.0
Separation Date Juice (S1)

Presscake (P1)

67.3

63.2

30.0

28.5

2.6

8.3

221.0

77.2

148.9

48.9

66.4

22.0

5.7

6.3

Extraction Presscake (P1)

Water (S3)

63.2

100

28.5

0

8.3

0

77.2

149.4

48.9

149.4

22.0

0

6.3

0

  Slurry       226.6 198.3 22 6.3
Separation Date Juice (S2)

Presscake (P2)

89.6

72.0

9.3

12.8

1.1

15.2

198.2

28.4

177.8

20.5

18.4

3.6

2.0

4.3

 

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