Extended Modified Continuous Cooking (EMCC) and IsoThermal

Cooking (ITC)

Extended Modified Continuous Cooking [11]and IsoThermal Cooking [12]mark

the consequent prolongation of the ground broken by MCC related to the equalizing

of alkali profiles and co-utilization of washing zone volume for cooking and

washing.

A typical configuration of an EMCC/ITC single-vessel hydraulic digester is

shown in Fig. 4.144. The initial process steps up to countercurrent cooking corre-

Steam

Wash filtrate

Circulation transfer

White liquor

WASH

HEATER

COUNTERCURRENT

COOKING

HEATER

CONCURRENT

COOKING

HEATER

Pulp

Extraction

Liquor

Fig. 4.144 Typical EMCC/ITC single-vessel hydraulic digester [12,13].

spond to the MCC technology described above. The additional element of EMCC/

ITC lies in the extension of the cooking zone down to the lowest set of screens

(see also Fig. 4.145).

There is no more dedicated high-heat washing zone between strainers. White

liquor is added not only to the top circulation and countercurrent cooking circulation,

but also to the wash circulation. At the same time, the temperature of the

wash liquor is raised to a point where the cooking temperature is also reached in

the extended zone. In Fig. 4.144, this means that the cooking temperature of typically

150–165 °C is maintained in the digester from the first set of screens down

to the last.

The split of white liquor between the points of addition must ensure that a

minimum residual alkali concentration is maintained in all liquors at all times, so

that the detrimental re-precipitation of dissolved organic compounds is safely

avoided. From a process perspective, EMCC and ITC are widely similar. Installation-

wise, EMCC requires only one wash circulation, whereas ITC uses two sets of

wash circulation loops with individual heaters.