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Fluid Bed Drying and Cooling Technology

Post on 2022-08-23

Counter current fluid bed drying

The main machine is a cylindrical continuous countercurrent fixed fluid bed. The crystals fall into the dryer by gravity and are blown to boiling state by the hot air blown from the bottom (boiling height is about 2 meters). The crystals are in full countercurrent contact with the hot air (contact time is more than10 minutes), and the moisture is quickly and completely removed by evaporation.Compared with vibrating fluid bed, counter current fluid bed drying can save more than 70% energy.

Drying equipment that evaporates and removes water by direct contact between hot air and water crystals mainly includes drum drying, air flow drying and fluid bed drying. Fluid bed drying also includes transverse flow fluid bed, intermittent fluid bed and counter flow fluid bed. Due to the different contact modes between hot air and materials, the energy consumption of various drying equipment varies greatly. The transverse flow fluid bed with the highest energy consumption is a rectangular fixed fluid bed or a vibrating fluid bed. Sincethe materials are always in contact with fresh air from entering the dryer along the bed to the discharge outlet, the boiling height is relatively low,and the evaporation capacity of the hot air is almost exhausted without using much, especially the hot air near the outlet is almost unused; Energy consumption is next to that of intermittent fluid beds, which are generally fixed fluid beds, including cylindrical and rectangular ones. Although the materials are always in contact with fresh hot air, due to the relatively high boiling height, the efficiency of hot air is higher when the wet materials first enter the fluid bed for drying, and is much lower at the later stage of drying; The second energy consumption is airflow drying. The materials are in contact with the hot air downstream (parallel flow), and the utilization rate of the hot air remains stable; The most energy-saving methods are drum drying and counter current fluid bed drying. Materials and hot air are in counter current contact, and the utilization rate of counter current of hot air evaporation can always be in the best state. Among them, the counter current fluid bed drying (generally cylindrical fixed type) is especially energy-saving, with high boiling height, and the hot air and materials are close to pure counter current contact and fully contacted. After drying and evaporating the same moisture, the more energy-saving drying equipment requires less hot air, and its tailwind emission is correspondingly reduced. The lower the moisture content and temperature of the tailwind, the less the total heat loss.

Counter flow fluid bed cooling

The main machine is a cylindrical continuous counter current fixed fluid bed. The crystals fall into the cylindrical counter current fixed fluid bed dryer by gravity, and are blown to boiling state by the cold dry air blown from the bottom (boiling height is about 1.2m). The crystals are in full counter current contact with the hot air (contact time is more than 6 minutes) to cool the materials to 20 ~ 25 ℃. Using counter current fluid bed for cooling can save more than 80% energy than vibrating fluid bed.

The energy-saving continuous counter current fluid bed drying and cooling integrated unit is a fully automatic working unit, which can meet the drying of products with low absolute moisture requirements (up to 0.01% at least) and anti caking requirements for finished products. It is especially suitable for drying organic acids, sugars or sugar alcohols, as well as other crystal or granular materials. It is also easy to manufacture a unit that meets GMP requirements for pharmaceutical enterprises.

The main machine of the fluid bed drying and cooling integrated unit is a cylindrical continuous counter current fixed fluid bed. The fluid bed is divided into upper and lower sections. The upper section is fluid bed drying and the lower section is fluid bed cooling. The upper section is the main dryer, and 95 ~ 98% of the water evaporation is completed by it; The lower section uses low-temperature cold dry air to complete the final drying and cool the materials to 20 ~ 25 ℃. The crystal falls into the cylindrical counter current fixed fluid bed dryer by gravity, and is blown into boiling state by the hot air blown from the bottom (boiling height is about 2 meters).The crystal is in full counter current contact with the hot air (contact timeis more than 10 minutes), and the water is quickly and completely removed by evaporation. After the dried crystals are taken out uniformly and continuously through the closed air valve at the bottom of the drying section of the fluid bed, they fall into the cooling section of the counter current fluid bed at the lower part, and are blown into a boiling state (boiling height is about 1.2m)by the cold dry air blown from the bottom. The crystals are in full counter current contact with the cold dry air (contact time is more than 6 minutes). After cooling, they are taken out uniformly and continuously by the closed air valve at the bottom of the integrated machine, and then sent to the square vibrating screen for screening. The finished product is conveyed to the silo by air flow through screening, and the agglomerates are sent to the crushing and then returned to the dryer by air flow. The tail air of counter current fluid drying has large moisture content and low drying temperature(generally below 50 ℃), which not only reduces the demand for air volume for drying, realizes high efficiency and energy saving, but also reduces the damage to thermal sensitive materials in the drying process.Similarly, due to the complete counter current contact between materials and cold air, the demand for air volume of cold and dry air is also very low,realizing the high efficiency and energy saving of cold source.

The operation process of the counter current fluid bed drying and cooling integrated machine can be completely controlled automatically. Due to the high boiling height, the problem of short circuit of materials is solved, the materials are dried evenly, and the quality of finished products is stable.Moreover, the sieve plate with special structure in the dryer can not only control the speed of crystal advance to be balanced and stable, but also prevent the crystal from falling into the air duct after the air is stopped.