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The reaction vessel may be discharged using the positive displacement pump into either of the two filtration systems. At right, a vertical tower, single plate pilot unit is shown. This unit has approximately 2 sq. ft. of area for filtration available. Wash water is added to the wash water vessel (in foreground), which is pressurized with air to facillitate washing of the cake. Using a roll cloth (seen in background), the resulting cake may be ejected following washing.

Filtrate, a mixture of acid and C₅ and C₆ sugars, is collected in 5 gallon vessels for storage and ultimate feed to the chromatographic separation system.

The vertical-leaf plate and frame filter system (seen at right) is also used to process lignin-cake and gypsum co-product streams. Again using the positive displacement pump, the hydrolyzate mixture is pumped through the channels in each leaf to fill the inner space between each leaf. When pressure is applied, via a hydraulic piston, the "juice" is expressed from the cake, reducing its overall moisture content to about 50%. In similar manner, the cake is washed, then discharged into the bin below. The filtrate, here too a mixture of acid and C₅ and C₆ sugars, is collected in 5 gallon vessels for storage and ultimate feed to the chromatographic separation system. This unit has 35 sq. ft. of filter area and has the capacity to receive the entire contents of the decrystallization/hydrolysis reaction vessel at a time.

In commercial scale equipment, the operation of the units seen here is entirely automatic; from fill to discharge to wash to cake ejection.