Manufacture

DSD powdered material vertical cooler is constructed on a principle of indirect cooling i.e. that cooling medium, in this case water, does not come into contact with cooled material. With this way of cooling as against direct water injection to hot ground material, the final product quality is not affected. Although the cooler can be used for reduction of temperature of different fine-ground materials, it is used mostly for ground cement cooling.

1. At temperatures 80-90°C gypsum breaks down according to the formula CaSO₄ · 2 H₂O = CaSO₄ · 1/2 H₂O + 1 1/2 H₂O. while plaster forms. Liberated water vapor condensates and reacts with clinker minerals. Aggregates, clusters and deposits occur and sometimes even arches are formed in a silo.
2. After hexavalent chromium in cement is reduced with ferrous sulfate heptahydrate (FeSO₄ . 7 H₂O), which is broken down at temperature 64°C, 6 molecules of water are separated and so the sulfate is dissolved. Therefore sulfate should be added to cement of temperature lower than 60°C.
3. Paper bags get torn when temperature of packed material is more than 80°C trhají. Optimum temperature is less than 65°C.

The cooler consists of a vertical cylindrical vessel in the inside of which there is a peripheral worm conveyor of material. The bottom is fitted with aerating plates, manhole and cleaning hole. Cooled material is supplied to the lower part of the cooling cylinder on its bottom where it is aerated and then by means of wipers positioned on a supporting basket of the worm, it is pushed on the peripheral wall of the cooler and then lifted up by worm blades and with its centrifugal force it is lifted along the cooled wall of the cylindrical vessel to the discharge positioned in the upper part. So this is the optimum heat exchange between material, cooled wall and cooling water. Water supplied to the upper part through the cooler lid is taken to a peripheral distributing channel out of which water flows evenly on the outer side of the casing. Brushes positioned here provide even water distribution on the outer wall of the vessel. Warm water flowing down freely is colleted in a collecting channel and it is returned back for further use through a discharge tube, it is either cooled again to temperature required and returned to the material cooling system or it is used as utility warm water. The water system is perfectly separated from the powder system and so water cannot penetrate into cooled material.

The cooler vessel is equipped with outside, self-supporting, plastic casing into which the system of air nozzles is fitted tangentially and these should increase velocity of air flow along the cooler wall and so support water evaporation from the cooler wall. This effect helps significantly to increase the cooler capacity. Vapor saturated with water is taken by a piping to the discharging stack and so the cooler environment is not covered in frost much in winter period. Aerating plates on the bottom and air nozzles are supplied with pressure air from a fan which is part of the cooler equipment.

The worm conveyor consists of several exchangeable parts that can be easily adjusted to the appropriate minimum gap between the conveyor and outside casing. With the gap size the period of material stay in the cooler is adjusted and so its efficiency. The worm cooler is driven by an angle gearbox in horizontal position placed under the cooler bottom incl. motor. For the maintenance to be easy the drive is well accessible and it can be dismantled by means of a lifting mechanism.

When the cooler is broken down, rest of material can be discharged through the cleaning hole and discharging chute by means of an auxiliary drive. The cooled material leaves the cooler through the upper discharging chute to a pneumatic conveying through or other conveying system.

As in cooling the side sprayed with water is covered with water algae, an independent cleaning circuit, used to remove these impurities from the cooler wall, is positioned in the water circuit. This cleaning circuit is designed so that cleaning lye would not get in cooling water.

Inside and outside cooler casing
Cooling water film
Aerating bottom detail

capacity
sprayed cooling area
contact cooling area
cooling water
heat output
water temperature difference
drive power