Circulation Type Laboratory Pulping Digester

lab digester


  • Self-contained laboratory sized pulping system supports the rapid development of processes.
  • Designed AND manufactured AND tested AND CERTIFIED to current ASME Pressure Vessel Code Section VIII, Div 1 for assurance of quality and safety.
  • Easy on and off cover, no leakage during temperature ramp, no shear on the seal.
  • Optional steam jacket heating for fast rates of temperature rise up to 25C/minute.
  • Computer graphical user interface with H-Factor cook control.
  • All 316 Stainless Steel wetted materials.
  • Circulation heating with minimized loop volume.
  • Liquor flow is returned directly over the center of the chip basket to ensure optimum distribution of the liquor throughout the batch.
  • Liquor circulation rates over 12 litres per minute (adjustable)
  • Standard high power for faster ramp times than the competition.
  • Redundant safety features; vessel temperature limit, heater power limit, heater temperature limit, overpressure cut-out switch and a rupture disc.



  • Batch and Continuous Process Simulation with metering pump option.


  • Custom sizes and any number of vessels with interconnection.
  • Metering pump for simultaneous liquor injection/extraction at operating temperatures and pressures.
  • Steam jacket heating.
  • Circulation flow meters.
  • Liquor sampling condenser.



     The Laboratory Digester is a self-contained circulation type pulping pressure vessel system. The vessels are available in the standard ten-liter size or sizes ranging from one to twenty litres, with practically any size available. The vessels are designed, manufactured, tested and certified to the current ASME Pressure Vessel Code Section VIII, Div 1. This is your assurance of proper design for longevity, uniform build quality and safety in every system.  The vessels have easy to open and close covers that are designed to not leak during temperature ramping.  The design of the covers does not impart any shear force to the gasket causing premature gasket failure.

     A seal-less magnetically coupled pump circulates the liquor through a 3000-watt electric heater. The heated liquor returns to the top of the vessel where it is distributed over the pulp.  The liquor return is directly over the center of the chip basket to assure even distribution of the liquor.  The circulation flow is variable by means of a variable speed motor controller on each pump. An optional flow meter is available for indication of the actual circulation calibrated in liters per minute.

   The flow enters the vessel on top of a removable stainless steel basket in which the wood chips are placed. A perforated weight is supplied for placement on top of the wood chips to ensure chip packing and uniform distribution of the liquor. A valve in the top cover provides a means for application of steam or for the evacuation of air. The dual vessel system enables the user to generate steam or to preheat liquor in one vessel for use in cooking in the other vessel.

     An RTD temperature sensor capable of measuring to 0.1° C accuracy is located at the bottom of the vessel, directly in the flow stream of liquor for optimum temperature sensing.  Cook programming and control is by means of Windows compatible software.  The software features graphical temperature and pressure indicators, Temperature vs. time graphing, Proportional, Integral and Derivative (PID) type control with an auto-tune feature, and H-factor cook control (the cook may be automatically terminated when a user-defined H-factor is achieved).

One or two vessels are mounted on a steel frame with casters for ease of movement. Multiple digester frames may be located in close proximity for configurations with other vessels. An optional metering pump facilitates simultaneous bi-directional liquor exchange between vessels. The metering pump is sized for your application and flow rate requirements.

     The metering pump flow rate is infinitely variable by the pump stroke adjustment or the standard variable speed control. The metering pump option includes remotely controlled solenoid valves that precisely start and stop the flow of liquor through the metering pump. Interconnection of the vessels may be permanent or by supplied quick connect fittings and flexible reinforced hose for rapid reconfiguration. Connections are made to the top and/or bottom of the vessels. An optional condenser with a pre-determined volume allows liquor sampling during the cook.

     Please contact us for more information on the existing features of the system or custom designs and options to meet your requirements.