Design of Clean Drying Room in Pharmaceutical Aseptic Workshop
In the medical aseptic workshop, a large number of vessels used in the production cycle need to be washed and dried. The clean level of the clean area as the auxiliary production area generally requires D level, and the drying room is no exception. After cleaning in a clean environment, the dehumidification and drying of utensils that contain a lot of moisture has become a problem we have to solve. We use examples to show that reasonable design can achieve energy-saving, drying and dehumidifying effects, which has certain theoretical guidance and practical application significance for this work.
0 Preface
Dehumidification is mainly divided into three types: heating and dehumidification, cooling and dehumidification, and desiccant adsorption dehumidification. In the past, the most commonly used method was heating, heating, ventilation, and dehumidification. However, in a clean environment, simply adopting the method of full delivery and full row heating and dehumidification, the energy consumption is large, and the load on the clean filtration system is also large, so we designed cooling and dehumidification 1. Comprehensive dehumidification method of heating and dehumidifying clean air circulation.
1 Principle
In the actual design, a small amount of fresh air is added to maintain the pressure difference of the system relative to the outdoor 12.5Pa. In the mixing section and the return air are mixed, the primary effect is filtered, and the air is cooled to the temperature below the dew point by the surface cooling water section, allowing the water vapor in the air to condense The water baffle intercepts and removes the water, and then the air is heated to more than 60 ° C through the heating section. The air expands and the moisture in the unit volume is reduced to achieve heating and dehumidification. The filter is sent to the drying room after filtering. In order to ensure the minimum temperature loss during the process, the purification and dehumidification fan should be as close as possible to the drying room, and the air supply pipeline should be insulated. The dried hot air absorbs the moisture in the vessel in the drying room, the temperature decreases (about 45 ° C) and the humidity increases, and it is taken out of the drying room through the return air pipe, returns to the mixing section and starts the next cycle, so as to achieve the purpose of dehumidification.
In addition, the temperature and humidity sensors are set at the air inlet and return air outlet. The exhaust fan is turned off when the machine is turned on. The system is in the circulating air flow operation mode. After a period of operation, as the moisture in the hot air absorption vessel increases, if the cooling and dehumidification power is not enough, the effect If the absolute humidity of the return air inlet is much higher than the absolute humidity of the air inlet, close the air outlet valve, open the exhaust valve, and exhaust fan, and use the direct exhaust mode to quickly replace When the humidity of the air in the system is high, when the difference between the two is not large, it switches to the circulation mode. The principle is shown in Figure 1.
In actual use, even if the cooling water is not turned on (such as the chiller is not turned on in winter), the purpose of drying and dehumidifying the utensils can be achieved by simply using the heating and dehumidification method of circulating and straight row alternating mode.
2 Application example calculation
2.1 Cleanliness and air exchange frequency
Comprehensively consider the clean room design specification GB50073-2013, the pharmaceutical industry clean plant design specification GB50457-2008, the 2013 version of GMP and its implementation guide, production and cleaning auxiliary area D. Clean room ventilation times are 6 times / h-20 times / h, fan The primary effect filter is G4 type, the intermediate effect filter is F type, and the H13 type high-efficiency filter at the air inlet of the drying room is selected. It meets the requirements of the medical clean plant. It has been verified that the dust particles are <3520000 / m3, which meets the requirements of the D clean plant.
2.2 Selection of fan air volume
Our drying room has an area of ​​42m2, a volume of 110m3, and an air-conditioning duct of about 120m3. A 2500m3 / h air volume fan is used. The number of air changes reaches 2500/120 = 20 times / h, which meets the design upper limit. The exhaust fan uses 2400 / h air volume fan, which can ensure that the system maintains a pressure difference of 12.5Pa relative to the outside world.
2.3 Heating power
2.3.1 Cubic meters of water content at different temperatures, humidity and atmospheric pressure (see Table 1)
The pressure difference between clean rooms is generally <50Pa, the pressure difference between the clean room and the outside is generally <80Pa, and the pressure difference between the fan and the outside is generally <500Pa, which is almost negligible relative to the atmospheric pressure of 0.1Mpa, which is almost negligible. Situation handling.
2.3.2 Flow of moisture in the air
The purification and drying system can run for a certain period of time. According to the heat preservation conditions of the clean workshop, the maximum temperature can generally reach 60 ℃, and the humidity can reach 80%. Look up the table 1. The water content of the air is 103.7g / m3, and the circulation volume is about 120m3 (dryer plus fan duct volume ), The quality of the water is:
m = 103.7g / m3X120m3 = 12440g
Known ventilation times n = 20 / h = 20 / 60min = 1/3 min
The maximum flow rate of moisture in the air is S = mXn = 12440g / 3min = 414.6g / min
2.3.3 Heat required per unit time
Assuming that the outdoor fresh wind is 0 ° C in extreme cases at the beginning of the cycle heating mode, it is assumed that the temperature of the return air inlet in the system is T1 = 0 ° C. After heating, the temperature of the air outlet T2 = 60 ° C and the water heat capacity C = 1cal / g ° C , Q = MCΔT / t = SCΔT = 414.6g / minX1 / g ℃ X (60 ℃ -0 ℃) = 24876 cal / min
2.3.4 Heating power
Assuming that the heating power is P, the heating efficiency n = 60%, the thermal equivalent: q = 0.24cal / j = 0.24kcal / KWs = 0.24 × 60kcal / KWmin
Table 1 Cubic meters of water content (g) under different temperature, humidity and atmospheric pressure q = 14.4 kcal / KWmin
Then the heat output per unit time Q = nqP heating power
P = Q / nq = 24.876kcal / min / (60% X14.4kcal / KWmin) = 28.8KW
So we choose 6KWx5 = 30KW adjustable heater with five gears.
2.4 Dry dehumidification
2.4.1 Simple heating and dehumidification
In the case of simple heating and dehumidification, assuming an outdoor temperature of 25 ° C and a humidity of 50%, the temperature and humidity of the inside and outside of the drying room are the same at the initial start-up, and the fresh air is turned off. After a certain period of time t1, the temperature in the drying room rises to 45 ° C and the humidity rises 80%.
It can be seen from Table 1 that the water content in the air is m1 = 11.4g / m3 and m2 = 52.2g / m3, respectively, and the system volume V = 120 m3 is replaced by a full row for a time of t2 = 60min / 20 = 3min. ΔM = (m2-m1) V = (52.2g / m3-11.4g / m3) x120g = 4896g
After the replacement, the temperature and humidity in the drying room are the same as the outdoor, and then switch to the cycle heating mode to enter the next cycle.
Similarly, when the outdoor temperature is 25 ° C and the humidity is 80%, the heating temperature will eventually reach 45 ° C, and the water can be removed in each cycle as shown in Table 2:
With less and less water removed each time through continuous circulation, the humidity in the drying room becomes lower and lower. In this way, the humidity in the drying room can be reduced to below 20% to achieve the purpose of drying the utensils.
2.4.2 Reasonable heating and insulation temperature design
It can be seen from Table 1 that increasing the holding temperature of the drying room up to 60 ° C, absorbing moisture in the vessel, setting the same time to reach 80% humidity, moisture in the air is 103.7g / m3, and the amount of water discharged at one time can reach (103.7g / m3 -11.4g / m3) x120 g = 11076g, which is more than double that of 4896g at 45 ℃, and the dehumidification efficiency is higher. It can be seen that the insulation of the drying room is very important.
However, because the temperature of the clean workshop around the drying room is generally 20 ℃, if the drying room temperature is set too high, the temperature difference is too large, the heat dissipation is also large, the heat loss is large, the required heating power is too large, the heating section temperature is too high, safe The risk is too great, so it is better to set the temperature of the heat preservation cycle at 45 ℃ -60 ℃. Usually it is set to 45 ° C in winter and 60 ° C in summer.
From Table 1, it can be seen that even when the maximum humidity reaches 100% and the outdoor temperature is 15 ° C, the maximum moisture content in the atmosphere is m1 = 12.7g / m3. The heating cycle is 45 ° C, the humidity is 20% after multiple displacement and discharge, the moisture content in the air is m2 = 13.0g / m3, m2> m1, indicating that the final humidity can be achieved by pure heating and dehumidification at this time. .
2.5 Comprehensive drying and dehumidification
2.5.1 Reasons for comprehensive drying and dehumidification
Under extreme conditions in summer, when the outdoor temperature is above 35 ° C and the humidity is 100%, it can be seen from Table 1 that the moisture content in the air will be> 40g / m3. If it is discharged by heating only, corresponding to the moisture content of 40g / m3, the circulation temperature in the drying room is 45 ℃, and the humidity is> 60%; the circulation temperature is 50 ℃, the humidity is close to 50%; 55 ℃, the humidity is close to 40%; even if the temperature reaches 60 The humidity at ℃ also exceeds 30%, at this time it is difficult to achieve the purpose of drying.
Therefore, under extreme conditions in summer, when replacing outdoor air, the outdoor high-temperature and high-humidity air should be first cooled and dehumidified to reduce the moisture content of the air from 40g / m3 to 15g / m3-20g / m3 and remove up to 25g / m3. Moisture, and then heating and cycling to 5055 ℃ -55 ℃, the final humidity can be controlled below 20% to achieve the purpose of drying.
2.5.2 Calculation of cooling capacity of surface cooler
According to the foregoing, the fresh air make-up volume V = 2500m3 / h, the fresh air water content M = 40g / m3, the unit time treatment water volume m = MV, = 2500m3 / hX40 g / m3 = 100Kg / h
In the process, it is necessary to reduce the 35 ℃ fresh air to 10 ℃, and the temperature difference ΔT = 25 ℃
Water heat capacity C = 1cal / g ℃,
Required cooling capacity Q = mCΔT = 100Kg / hX1cal / g ℃ X25 ℃ = 2500Kcal / h
If the exchange efficiency of the surface cooler is 50%, the cooling capacity requirement should be 5000 Kcal / h.
3 Program control
The operation of the clean dehumidification and drying system involves fresh air, return air valve switch, temperature and humidity collection, moisture content in the air, time parameter calculation and comparison control, heating, refrigeration, fan no wind protection, overheat protection, various operating mode switching Control, so we chose Siemens S7-200PLC programming controller, and connected to the central monitoring system through the network, can achieve dual control of online and remote monitoring.
references:
[1] Drug Certification and Management Center of the State Food and Drug Administration; Drug GMP Guide Plant Facilities and Equipment [M]. Beijing: China Medical Science and Technology Press, 2011.8
[2] Order No. 79 of the Ministry of Health of the People's Republic of China. Regulations on the Quality Management of Pharmaceutical Production (2010 Revision) [EB]. Beijing: Ministry of Health, 2011.1
[3] Liu Xianzhe, Cai Zhiming; Design, Construction and Commissioning of Dry and Clean Workshop; Clean and Air Conditioning Technology [J]; 1997.3.
[4] Wang Jun; Experience of air conditioning and ventilation design in clean workshop of pharmaceutical factory; building thermal energy ventilation and air conditioning [J]; 1998.2.
[5] Xu Li; Design and Management of Clean Workshop during GMP Implementation; Chemical and Biological Engineering [J]; 2003.4.
[6] Chen Guangjian; GMP design of pharmaceutical factory clean workshop from the perspective of production management theory; pharmaceutical engineering design [J]; 2001.1.
[7] Wan Bin; Cai Zhihui, Zhan Yanmin; Air-conditioning energy-saving control transformation of GMP clean workshop; [J] Electrical Engineering Technology; 2009.12.
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