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Mash Filter Operation - Learn More

 

Overview
While it is possible to operate a mash filter using only manual control, for consistent results and efficient operation, automated programming is required. Pump speed during filter filling, filtration and sparging and air pressure control of the membranes and the timing of these events must be controlled to hit specific targets as described in the steps that follow. All these variables are set by the operator in the Aegir Insight control system, some by recipe, some for all recipes.

Step 1 Filling (< 5 minutes)
During this step the mash pump transfer the mash from the mash tun to the filter at a fixed pump speed. As mash enters the filter, air present in the filter will be expelled through the wort outlets. This steps ends when the filtration chambers are full and wort starts flowing past the sight glass at the mash filter outlet.

Step 2 Filtration (~ 20 minutes)
During this step the filtration cake builds up on the filter cloths. The inlet pressure is increased as cake thickness builds to maintain the desired wort flow rate until the optimal filtration pressure (typically 400 - 500 mbar) is reached. Once this pressure is reached the filtration is continued   at   constant   pressure   and   the wort flow rate will to decrease as the filtration proceeds.

 

Step 3 Pre-compression (~ 5 minutes)
During this step the membranes are inflated at an air pressure close to the filtration pressure.
The objectives of this step are to recover some of the high gravity wort present in the filtration cake prior to dilution during sparging and to homogenize and reduce the cake porosity and thereby obtain more efficient sparging. This step must start immediately after the end of the filtration step to avoid cake collapse in the chambers.

 

Step 4 Sparging ( ~ 30 minutes for Micro and Craft Junior)
During this step, the cake is typically sparged with water at 78°- 80°C to recover extract from the cake until the wort gravity at the outlet of the mash filter drops to ~2°P. The sparging water  is  sent  into  the  mash  filter  through  the  mash  inlet.  Sparging water can either come from the mash tun or from a line at the suction side of the mash pump. The average amount of water required is about 2.5 l/kg of malt equivalent.

Sparging is divided into 2 steps. In the first step, the membranes  are  decompressed  slowly  and  at  the  same  time  the sparge water is pumped into the filter chambers. The speed of the mash pump is adjusted in order that the pressure at the inlet is maintained at typically 200 - 300 mbar) and that there is always some flow  at  the  wort  outlet  in  order  to  avoid  filter cake  collapse that would lead to inefficient sparging due to the formation of preferential pathways.

In the second step, the membranes are fully deflated and sparging continues until the wort density reaches ~2°P. The inlet pressure should be increased to overcome the increased resistance of the filter cake due to the pre-compression).
 

Step 5 Final Compression (~ 10 minutes)
This step results in a reduction of the filter cake moisture content and is divided into two stages. In the 1st compression, the air pressure is the same as during pre-compression, typically 400 - 500 mbar, to push out the water inside the chamber in between the membrane and the filter cake. In the 2nd compression, the air pressure is increased to typically 800 - 900 mbar to reduce the moisture content of the cake to about 70 - 75%.

Step 6 Filter Opening (~ 2 minutes)
The filter is opened during this step.

 

Step 7 Spent Grains Removal (~ 10 minutes)
When the hydraulic ram is fully retracted, the filter plates can be moved manually one at a time towards the traveling plate to let the filtration cake to drop into the spent grains recovery bins or into a discharge hopper with spiral auger and expeller.