Characteristics and Shortcomings of Double Cone Vacuum Drying Equipment
1 Overview
Double cone vacuum dryer (hereinafter referred to as double cone) is a long history of vacuum indirect heating dynamic dryer, is an energy-saving drying equipment. It is characterized by a vacuum cone driven by a drive 360. Rotation, to promote the material in the cone and the cone and the heating surface contact heating, and constantly mixing material on the heating surface from the self-cleaning effect, vacuum operation is conducive to reducing the evaporation pressure and evaporation temperature, improve the heating medium and heating materials Temperature difference, but also very conducive to many low-temperature heat-sensitive materials dry. The double cone is operated with no other inert gas in the vacuum, which is very advantageous for the evaporation and drying of various organic solvent materials to recover the solvent with high solvent recovery. The structure of the double cone is very conducive to the drying of the dry material fast discharge, which is any other type of dryer can not match the advantages of operation.
Double cone for a variety of non-sticky wall loose material drying, because the cone in the vacuum suction pipe on the tail gas filter, it greatly reduces the exhaust gas entrainment product dust loss, high dry yield. It can be a one-time feed and sealed discharge, to avoid operational pollution, to avoid dust when flying dust and pollute the environment. The double cone dynamic drying efficiency is much higher than the various disc drying.
However, there are some shortcomings in the double cone drying, the first is the double cone only for intermittent drying. As a result of the use of friction-type mechanical vacuum seals, seals can not be avoided in the dry friction in the production of foreign matter, in the event of vacuum leakage, the seal of the wear and tear of foreign matter must be sucked into the double cone, and dry products are mixed, if Products are drugs are drugs are contaminated, so that good drugs become poor quality medicine harm medicine.
If the double cone is used as a sphere, the heating area F (m) is proportional to the square of the sphere diameter D (mm) when the double cone dryer is enlarged, and the double- The volume V (m) of the sphere is enlarged in proportion to the square of the sphere diameter D (mm). So the double cone from small diameter to large diameter, its heating area is far less than its volume expansion. The ratio of the double cone heating area F (rfl) and the double cone volume V (m) is proportional to the expansion of the diameter D (iTlm), resulting in a small size of the double cone of the F / V value is much larger than the large size of the double cone F / ,, value. The F / v value of the 5 m biconvex is about half of the F / V value of 0.3 m biconvez, about 3.6 m / m, and its F / V value decreases when the double cone volume expands to 10 m To 2.5 m / m.
Double cone vacuum drying equipment As the name suggests for heating and drying, the main function should be reflected in the heating and drying efficiency or heat exchange area size. Relatively speaking, its volume is secondary. But at present almost all of the double cone dryer product samples, are the size of the volume to identify the specifications of the double cone, which to some extent is a double cone factory intentionally misleading users. Because many users do not realize that there is a regular change in F / V when the double cone is enlarged. Mistakenly believe that the size of the volume of double cone has a similar drying efficiency. Often buy a large double cone, found in the production of its drying efficiency, much lower than in the dry factory with small size double cone test practice to produce drying efficiency. Because the drying efficiency doubled down to meet the desired output, had to buy a large double cone. Not only increased investment to increase plant land, and delayed the production plan.
Many heat-sensitive products drying temperature below 100 ℃, is a lot of heat-sensitive products are still drying <100 ~ hot water as a heat source, this must be equipped with hot water tank, hot water pumps and hot water pipes and other auxiliary facilities. Hot water heating is inevitable there is import and export temperature difference, and steam latent heat compared to naturally reduce the temperature difference, which is very high heat sensitivity of low temperature heating is very unfavorable. Hot water heating heat transfer coefficient is much lower than the saturated water steam heating, jacket hot water heating structure is also more complex than the steam heating, not only increased the investment in equipment, but also not conducive to management.
As the drying material in the double cone in the continuous mixing rotation, some crystalline fine water content of more products, such as riboflavin, spiramycin and other products are easy to form in the mixing of varying sizes of pellets. Once the pellets are produced, it is difficult to achieve complete and thorough drying. In principle, the double cone does not apply to the presence of knots in the dry material.
The double cone is a dynamic drier with a heated boiler (heated jacket) constantly rotating. Large (large diameter) traditional double cone of the cone and the outer wall of the jacket wall thickness is very thick, heavy weight. Cone liner is generally stainless steel, and the outer wall of the jacket is carbon steel. The diameter of the large double cone (2 ~ 10 m) is 1,600 ~ 2,600 mm, the wall thickness of the cone is 8 ~ 14 mm, and the wall thickness of the outer wall is thicker. As we all know, the thermal resistance of stainless steel 5 times larger than carbon steel, very thick stainless steel liner is not conducive to the pyramid heat transfer, reducing the double cone heating and drying efficiency, driving a heavy liner naturally to increase the drive motor power The The double-cone outer jacket is thicker and heavier, but also increases the energy consumption of the drive motor. Double cone a year running time in a few thousand hours, so how to correctly deal with the long-term operation of the double cone to improve efficiency and energy saving, in the world are actively mobilizing a new era of energy conservation, the equipment structure that has been neglected in the past Equipment materials, it is worth our in-depth study and discussion.
The following discussion was made with the double cone without GMP requirements.
2 double cone magnification
With the development of fine chemical products, more and more need for high efficiency and large double cone. A traditional large double cone, its huge body shape and it contains the heating surface is not commensurate, a 5 m double cone heating area of only 18 m, F / V value of 3.6 m / m, and a 10 m double cone of the F / V value further decreased to 2.5 m / m, with the external strong to describe the double cone is not too much.
The magnification of the double cone vacuum dryer is the amplification of the heat exchange area. Fortunately, there is a huge space within the cone can be used, how to use this space is the key. Taking into account the cleaning of the equipment, the surface of the heat exchange element is as simple as possible. Selection of thin empty c, Di ~ hot plate, both in line with the surface clean and clean and meet the compact double requirements. With 10 m double cone as an example, it is possible to set the thin inner heating plate in the direction of the flow of the material in the large pyramid space. For the cleaning and necessary maintenance space, such as 110 to 160 mm spacing between the inner heating plates, The general increase in the area of the inner heating plate than the original cone heating area of 1.5 to 3 times, so that the double cone of the F, V value can be increased to 0.2 m. Small double cone similar to the 9.0 m / m value. In particular, the thickness of the inner heating plate is less than one third of the thickness of the cone, and the heating area is doubled and the thermal resistance is greatly reduced, so that the double cone drying efficiency after amplification is more than 2 to 3 times that of the conventional double cone. The inner structure of the 10 m double cone is shown in Fig.
As illustrated in Figure 1, 10 m. The diameter of the cone 2,600, 600 mm wide on both sides of the maintenance channel by # l ~ ≠} 7 within the heating plate 7, a total of 14, the total area of the heating plate F = 56 m, the heating plate thickness 40 mm, the total volume of the inner heating plate V = 2.2 m, the center distance of the inner heating plate d = 200 mm, the actual gap between the two inner heating plates is 160 mm, the known heating zone of the cone jacket F = 29.6 m, so the total area of 10 m double cone heating F = 85.6 m, the volume of known cone V = 12.1 m, after deducting the actual volume of the cone after the heating plate V = 9.9m, by The F / V value of this new double cone is 8.6 m / m, which is very close to that of the small 0.2 in double cone of 9.0 1TI / m. 10 1TI double cone without heating plate F / V value of 2.5 II1 / m, so increase the internal heating plate after 10 1TI. The double cone is not more than 3 times higher than the F / V value (as shown in Fig. 2). If the F / V value is increased, the drying efficiency of a new double cone can be reached Double cone, single hour drive motor can save about 60 kW / h power consumption.
3 large double cone to increase the comparison of the inner heating plate to save stainless steel
Still take 10 m (actual operating volume) as an example. The 10 m double cone has an external dimension of 2600 x 3600 (total height). According to the above description double cone heating jacket area F = 29.6 in, the total area of the heating plate F = 56 1TI, if the double cone wall thickness of 14 millimeters, and the inner heating plate wall thickness of 3 mm, then The double-cone stainless steel weighs 3-3 t, while the weight of the stainless steel on the inner heating plate is 1.34 t. It can be seen that per square meter of double cone requires 111.4 kg of stainless steel, and the heating plate per square meter of stainless steel is only 24 kg, that is, double cone per square meter heating area consumption of stainless steel than the same Heating area of the internal heating plate more than 4.6 times. Only from the existing large-scale traditional double cone has a heating area ~ IE4, and the consumption of stainless steel a lot of this special situation to consider the cone empty, both conditions to increase the heating plate, but also very much need to increase the heating plate To counteract the negative effects of cone wall thickness.
4 The structure of the inner heating plate is strengthened
Conventional hollow thin inner heating plate must be strengthened by plug welding. Because the wall thickness of the inner heating plate is only 2 ~ 3 mm, both sides of the hollow heating plate need to be perforated. It is difficult to strictly process the groove on the sheet. There is a drug GMP requirements of the heating plate in the welding must be polished after polishing, so in many of the solder joints in the existence of a slight weak links, it will be in the future production operations in the sudden burst due to local rupture caused the entire heating plate blasting. The traditional sheet welding reinforcement structure is easy to leave this hidden danger.
We learn a lot in the new double cone within the heating plate to strengthen the structure of the use of hinged non-destructive welding to strengthen the technology, the heating plate on the double-sided motherboard is no longer perforated, so as to avoid drilling plug welding operation brought about by the ills, Eliminating the practical problems of internal heating plate machining that is essential for double cone magnification.
5 double cone low temperature (100 ℃) heat source problem
Double cone dry heat-sensitive products, the traditional double cone are used hot water heating method. Hot water heating not only need hot water tank, hot water pump and pipe a set of cumbersome, due to hot water heat to heat, import and export must exist temperature difference, hot water outlet temperature low natural heating and drying effect is much lower than the hot water inlet, so Hot water heating temperature difference is not conducive to dry.
Large-scale double cone If you still use hot water heating, due to a substantial increase in the load of dry equipment and the need for a substantial increase in heat load, hot water heating system, a set of cumbersome also concocted, not only a lot of equipment investment, The efficiency of the drying equipment to bring a lot of disadvantage. But if the use of saturated water vapor as a heat source, as long as the strict control of the double cone heating jacket within the temperature or pressure to ensure that the temperature or pressure in line with the heating temperature requirements of the saturated water vapor physical parameters to ensure that the jacket will be timely steam condensate Water out. You can use 0.2 MPa of saturated water directly to the double cone of low temperature heating heat source. Of course, large-scale double-cone jacket within the larger space, just driving the jacket (especially within the heating plate) there are a lot of inert gas must be discharged clean, otherwise it will seriously affect the normal operation, the best way is to smoke Vacuum, and then add saturated water vapor.
6 Study on Thinning Thickness of Equipment with Large Double Bars
Today's world are considering energy-saving emission reduction, up to the aircraft down to the train car, are trying to reduce the thinning in the structure. It is also necessary to study from the energy saving and emission reduction, save stainless steel and improve the efficiency of heating and drying, and it is also necessary to make our contribution in the field of drying technology.
7 concluding remarks
With the T and fine chemical production of large-scale, need a lot of large-scale double cone vacuum dryer, due to large-scale double cone structure did not keep up with the pace of the times, to bring a lot of problems with the use of production. Our industrial production and the proportion of energy consumption is much higher than Japan and other developed countries, ignoring the efficiency of many devices, especially the existence of equipment is not the cost, and the weight of the equipment to the price of misunderstanding, double cone vacuum drying The device may be typical of this.