Description

The Pulping Lab Digester controller is a modular, fully configurable, high accuracy, high stability temperature and process controller available with single, dual or three loops. It can be applied to air bath ovens or individually heated digesters.

In the case of an Air Bath Oven, it controls the air bath temperature to achieve the desired bomb temperature. Electrical heater elements are switched in a time proportional manner to control temperature. Cooling is achieved by operation of a vent. The bomb temperature is ramped up to the target cooking temperature and held there until the target H Factor is achieved, whereupon the cook is terminated and the temperature dropped back to ambient.

The calculation of H Factor is as follows:

(43.2 – 16113/T)

H FACTOR per HOUR = exp

Where T = the bomb temperature in degrees Kelvin.

The calculation of H Factor per hour begins to totalize very slowly once the cook is started. Once temperature is greater than 140 deg C, the H Factor will begin to accumulate noticeably.

Operation

The operator will set the desired H Factor, desired cooking temperature and desired rise time before starting the cook. Oven air temperature will be controlled with time proportioned pulses to the 8 heater elements to achieve the desired bomb temperature.

Temperature will be ramped up to desired cooking temperature at a ramp rate calculated from the desired bomb temperature and the desired rise time. H Factor will be based on bomb temperature. When the desired H Factor is reached, the temperature will be ramped down to zero and the vent opened.

A User Page is configured to allow the operator to setup the cooking parameters and to monitor the cook.

Cook parameters that can be altered are accessed via the bottom line:

§ Start/Stop parameter Set to ON to start or stop cook.

§ Desired H-Factor Target HF

§ Cook Temperature set point Deg C

§ Temperature Rise Time Minutes

§ Start Time HH:MM:SS (24hr clock)

§ Pulse Time HH:MM:SS (Set to 1 sec after start)

§ Timer Mode Set to ON to enable delayed start.

Normal Operation

Set up the H Factor Target, Cook Temperature and Rise Time.

With START selected, press the up arrow or down arrow. START will be ON momentarily and COOK will be highlighted as the cook commences.

An audible alarm will sound when the cook is within 100 HF of the target H Factor.

Delayed Operation

Set up the H Factor Target, Cook Temperature and Rise Time.

Set up the START TIME via the up or down arrows. Set the PULSE TIME to be 1 second after the START TIME.

Set the TIMER MODE to ON.

Start the Air Bath motor.

The cook will commence at the designated time.

An audible alarm will sound when the cook is within 100 HF of the target H Factor.

Set the TIMER MODE to OFF.