Recently, in the Western countries, high-temperature dryer with 3-pass cylinder, where traditional drying method has been substantially updated, is becoming more and more widespread.

The peculiarity of this dryer consists in the fact that contacted media (air-gas blend and exhausted cossettes) pass through the cylinder in 3 turns, and discharge of exhausted cossettes and spent gas cleaning from dust of exhausted cossettes are carried out in one device – cyclone.

This dryer has a lot of advantages compared to the traditional one:
1. Cross-sections for pass-through of the contacted media are selected in such a way that the highest speed of gases and exhausted cossettes is obtained in the first pass of the dryer cylinder and the lowest one – in the last pass. Due to this, the time of presence of exhaust cossettes in the first pass, that is the most dangerous from the point of view of ignition, where the blend of heated gases has the highest temperature. On the contrary, the highest time of presence of exhaust cossettes, where the temperature difference between gases and exhaust cossettes, and, consequently, intensity of heat and mass exchange between them will be maximal. Total time of presence of exhaust cossettes in 3-pass cylinder is less than is traditional one.
   It allows to:
   • increase sufficiently fire safety of the facility;
   • decrease losses of exhaust cossettes in the cylinder;
   • use the length of drying cylinder for exhaust cossettes more rationally;
   • decrease heat losses into the environment;
   • mprove quality of exhaust cossettes (more uniform drying, less quality of burnt particles).
2. Flanks of 3-pass cylinder are performed in form of cone. As a result, diameters of input and output couplings of rotating cylinder with fixed parts are much less than those for traditional dryer with equivalent productivity. Apart from this, there is one discharge unit instead of two for traditional dryer (one – for exhaust cossettes and another – for dust from exhaust cossettes, caught in the cyclone). These design features allow to reduce air suction via sealing devices of the cylinder and during discharge of the exhaust cossettes.
3. The advantages of 3-pass cylinder also include:
   • less metal intensity;
   • less length.

"Teplocom" Ltd. is ready to develop the project based on dryer with 3-pass cylinder and carry out all the activities concerning manufacturing, supply and assembling of the equipment with turnkey commissioning.

New type of dryers, where overheated steam is used as drying agent, is more efficient and economical compared to high-temperature cylinder dryers. Such dryers have appeared recently in sugar industry, but, at the moment, they are successfully operated in some foreign countries. The most successful dryer of such type was developed in Denmark; now it is commercially manufactured by several companies.

In this device, on the most efficient drying methods is applied – drying in pseudo-liquefied layer of dried materials. Drying takes place without access of air. Overheated steam, obtained from exhaust cossettes during drying, serves as drying agent. Heat supply is carried out by feeding saturated or slightly overheated, but with higher temperature potential, steam to the heat-exchanging device. By help of heat-exchanging device, introduced heat is transferred to steam, obtained from the exhaust cossettes, and, from this steam, by direct contact, to the exhaust cossettes. In the device, principle of recirculation of the secondary steam obtained is implemented, as well as differentiation principle, due to which bigger particles of the exhaust cossettes are present in the device for a longer period of time than smaller particles. It allows uniform drying of all exhaust cossettes.

Good design, where heat exchanger, fan, devices for differentiation of particles of exhaust cossettes, and secondary steam cleaning device are integrated in one body, allows to reduce significantly construction volume of pulp drying department and even more, that is of great importance, construction length of the premise.

Saving factor of the facility depends on how the secondary heat of secondary steam and condensate, taken out from the device, will be used. For this purpose, initially, during design development, there were set the parameters for secondary steam, equivalent to those of process steam, coming from heat generation plant (3 kilogram-force per cm², 148⁰С), that allows almost complete use of its heat in the heating circuit of sugar mill. Successful completion of this task will allow to reduce fuel consumption by more than 10 times compared to traditional dryers.

In the steam dryer losses of exhaust cossettes are almost absent, the facility is fire-safe, quality of dried pulp is significantly improved.

Design of installation of steam pulp drying device always envisage, to certain extent, reconstruction of heating schemes of sugar mill and heat generation plant. Extent of such reconstruction depends on park of equipment, available at the enterprise to be reconstructed. Proportions of heat and electric power, generated at heat generation plant could change to the significant extent. All this should be taken into account during designing.

"Teplocom" Ltd. will carry out for your company calculation of feasibility for the project of plant reconstruction with installation of steam pulp-drying device, as well as will carry out the design, supply and assembling of the equipment with turnkey commissioning.