Hardening of green blocks
4 – Hardening of green blocks
The importation of the green blocks in the autoclave
After 8 hours of curing time, the cured cake leaves the autoclave.
The green blocks called calcium silicate bricks will be introduced into the autoclave. They will be steamed during 8 hours under a pressure of 16 bar and a temperature of 200°C
The hot steam solves some silicic acid on the surface of the sand grains.
They form together with the ingredients of mixture a new crystal structure, said crystal phase CSH. In this way, the sand grains are firmly linked. The sand-lime brick is hardened.
The hardening of material in the autoclave is the main stage of process consuming of the steam. Habitually several autoclaves will be exploited at different times and an accumulator of steam used for the recovery of partial heat.
The heat recovery is for the use of condensate and also for the optimum reuse of the steam which is produced for the autoclaving.
Upon closing of the autoclave, the steam will be temporarily stored on one hand to use it in the autoclaving and on the other hand for the building heating system and the preheating of the feed water.
Through a heat exchanger, heat can be regained from the condensate to use it in the preheating of the feed water or to preheating the fermentation rooms or to heat buildings.