Drum dryer – use and maintenance
The efficiency of the drum dryer is usually measured by the mass of moisture in the fabric that can be vaporized per square meter of effective drying area per unit time, generally 11kg/(m2 h). It mainly depends on factors such as the surface temperature of the drying cylinder, the effective drying area, the vehicle speed, the condition of the fabric being dried, and the evaporation of moisture on the fabric. Therefore, in order to improve drying efficiency, the following measures can be taken:
(1) Appropriately increasing the steam inlet pressure can increase the temperature of the drying cylinder, thus speeding up the heat exchange rate on the surface of the fabric and the internal heat transfer rate. However, if the surface temperature of the drying cylinder is too high, it will have a negative impact on the feel of the fabric being dried, and it also increases the requirements for the strength of the drying cylinder.
Therefore, the copper drying cylinder is generally controlled at around 120℃, and the steam inlet pressure is controlled at 98~147kPa. If it is a new copper drying cylinder, the surface strength of the drying cylinder is consistent and the steam inlet pressure can reach 196kPa.
(2) Quickly and effectively discharge the condensed water in the drying cylinder. Since the thermal conductivity of water is very small, quickly discharging it from the drying cylinder can reduce the thickness of the water layer in the cylinder and facilitate heat transfer. Therefore, it is important to choose a suitable drain trap. For siphon drying cylinders, a separate thermal power trap can be installed under each drying cylinder, which is beneficial to improving heat transfer efficiency under high-speed rotation.
(3) Blow air to the vaporization surface of the fabric being dried. When moisture vaporizes from the free surface of the fabric to be baked, a sluggish water vapor layer is formed on the surface of the fabric, which is not conducive to the continued diffusion of moisture in the fabric to the free surface. Blowing air to this area can thin and destroy this water vapor layer, increase the partial pressure gradient that takes away evaporated water from the fabric surface, and accelerate the vaporization rate. This blowing device is installed on the drying drum of the Vaporloc flat washing machine manufactured by the British company Mather & Platt. An air duct is installed on one side of the drying cylinder, and a wide arc-shaped slit air outlet is opened to speed up the vaporization rate and improve the drying efficiency.
Although the steam inlet pipeline of the dryer is equipped with a safety valve and a pressure reducing valve, and an air safety valve is also installed on the bulkhead of the drying cylinder, since the drying cylinder is a pressurized thin-walled container, it should be used when using it. Strictly abide by operating procedures and strengthen governance. When starting a cold truck, first open the truck empty, and open the trap straight-through valve and bypass pipe stop valve, the drain valve at the lower end of the station column and the steam exhaust valve at the upper end, as well as the air safety valves of the lower drying cylinders. Wait until the steam comes out. After the open air safety valve ejects, then close the above-mentioned drainage and exhaust valves, gradually open the steam valve to heat the cylinder surface according to the required steam inlet pressure, and guide the cloth operation. Otherwise, because the accumulated cold water and cold air have not been fully discharged, a large amount of steam suddenly enters, which will quickly condense and form negative pressure, causing the drying cylinder to collapse.
During operation, you should always check whether the indication value of the pressure gauge on each steam inlet pipe is normal, and make necessary adjustments to the relevant steam inlet regulating valve to prevent the safety valve from malfunctioning and the steam pressure entering the drying cylinder being too high. explode.
The troubleshooting and maintenance of the drum dryer are shown in Table 5-1 and Table 5-2 respectively.
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