Self-Assessment Questions

1. ***Extract efficiency from your mash filter is running low. From the given data below, calculate the actual current extract efficiency – show your workings. Explain how you would investigate and remedy the situation.

The Mash Filter is producing 475 hL of wort at 1.060 Specific Gravity and 14.68  ˚Plato.

Mass of malt used = 10,000 kg.

Malt extract dry = 82% w/w or 316.6 L˚/kg.

Malt moisture = 5% w/w.

Density of water at 20˚C  = 0.9982 kg/L.

2. ***Your lauter tun is the rate limiting step in the brewhouse. It is rated at 10 brews per day, with a cycle time of 144 min. Current cycle time is 10 min longer than this. Demonstrate the impact of this on brewhouse capacity. How would you investigate, and remedy, this situation?

3. ***Using the data from the table below, and by reference to Darcy’s Law, explain why the mash filter is the fastest wort separation device.

Table: Design and operational parameters for mash tun, lauter tun, mash filter

Darcy Variable

 

Lauter Tun

Mash Tun

Mash Filter

 

Tun diameter                m

8

5

20 (58 chambers)

 

Grain bed loading       kg / m²

200

500

30

 

Cycle time                      min.

144

288

110

 

Brews per day

10

5

13

 

Water to grist ratio

3.2

2.5

2.7

 

Milling system

Wet / six- roll dry

Two / four-roll dry

Hammer

Q

Wort flow rate       hL/h

889.2

378

1,522.9

K

Bed permeability m2

3.084 x 10-11

9.72 x 10-11

      3.525 x 10-13

K

Relative permeability

87

275

1

DP

Maximum limit                bar

0.1

0.1

0.3

A

Filtration surface area     m²

50

20

330

µ

Mash Water                    L/kg

3.3

2.5

2.7

µ

Sparge water                  L/kg

4.0

5.0

2.8

µ

Malt modification

     Less well

Well

       Less well

µ

Mash temperature          ˚C

76

65

76

µ

Strong worts viscosity       mPa.s

1.25

1.85

1.65

L

Grain Bed Depth            m

0.5

1.0

0.05
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