Have you seen the open top cover hood of an old paper machine?

Reasonable structure and good sealing performance are the guarantee of high efficiency hood. According to the structure, the hood is divided into open hood and closed hood. Today, we mainly talk about the open top cover hood. Most of these types of air hoods can be seen on old paper machines. Most modern paper machines use high-speed airtight hoods or Yankee hoods. If you know about the open top cover hood, you can better understand the functional components of the hood.

Open top cover hood

This is the simplest form of hood, that is, a top cover is installed above the drying section. Many covers are only made of low adiabatic value plates, which require high air displacement to prevent condensation. There are also external insulation boards to provide better insulation performance, and the humidity can be slightly increased. This kind of hood is generally not tightly assembled to the drying section, and the leakage is a big problem. In order to capture water vapor and prevent condensation, the design value of exhaust volume is very large. The exhaust humidity range of open top cover hood is 0.04-0.07 kg (water) / kg (dry air). The exhaust humidity of simple cover is about 0.04kg (water) / kg (dry air). The exhaust humidity of the simple cover with insulation board is about 0.07kg (water) / kg (dry air). About 13 kg air is needed for each ikg water evaporation, and the energy consumption is increased due to the dry high air flow passing through the drying section. The high exhaust volume must be balanced with the air supply of the heating building, thus increasing the heat load of the building. Low exhaust temperature increases the cost of heat recovery, most of which are not desirable. The open hood is rarely used in new paper machines. Many old paper machines are still using open hoods, but they are gradually being replaced by more efficient closed hoods.

The drying section of paper machine is equipped with high efficiency closed air hood, which can improve the production environment, reduce the production energy consumption, and improve the paper machine efficiency and product quality. At present, domestic and foreign paper machine manufacturers have applied a lot of new technologies and materials in the design of ventilation and hood of paper machine drying section, which makes the performance and structure of ventilation system and air hood of paper machine drying section perfect, so as to meet the needs of high efficiency and high speed paper machine operation.