Laboratory ventilation and exhaust system control steps and programs
(1) The laboratory selects a certain number of fume hoods according to process requirements and functional layout, some of which also have partial local exhaust hoods. Usually, the number of ventilations after inspection is far more than 10 times, generally more than 20-30 times, to meet the requirements of ventilation. However, the ventilation rate is calculated based on the maximum opening area of the fume hood. Data and experience show that only 18 or fewer people use the fume hood 99% of the time. Therefore, when the minimum opening area of the fume hood is less than the ventilation time requirement, it is also necessary to check the ventilation volume and ventilation time. If it is less than the requirement of ventilation time, an integrated exhaust system should be added.
(2) The laboratory ventilation adopts a new air system, and the exhaust air of the fume hood does not circulate indoors. Because the laboratory requires the room to be under negative pressure relative to other auxiliary areas. Therefore, the fresh air volume of the laboratory is designed to be 70%-80% of the exhaust volume. In addition, 20%-30% of fresh air is sent to the auxiliary room, office, management room, internal walkway, etc. of the laboratory, and then the gap between the door and window is added to the room.
(3) The air volume balance of the laboratory fume hood can adopt a fixed air volume control system, that is, the exhaust air volume is constant, and the supply air volume and the supplementary air volume of the gap between the doors and windows are constant. This method is suitable for laboratories where the maximum exhaust air volume meets the minimum ventilation requirements. Tag: ventilation renovation
(4) For rooms with an exhaust air volume far greater than the minimum ventilation requirement, a two-stage ventilation control system can also be used to ensure the balance of the air volume, that is, according to the displacement signal of the fume hood, there are two types of air supply conditions for the exhaust fan and blower, low air volume The operating conditions should be applied to maintain the minimum number of air changes, saving energy consumption. In this case, a variable air volume control system is used. When the air volume of the fume hood changes, the exhaust air volume will also be relatively small. At this time, the exhaust fan placed on the roof is required to change frequency as the position of the fume hood door changes, reduce the air volume, and ensure the constant wind speed of the fume hood surface. At the same time, the automatic control system changes the frequency of the new fan, reduces the air volume, and maintains the negative pressure balance. Variable air volume system can reduce system energy consumption. When the maximum and minimum ventilation times of the system are close, the fixed air volume system is considered, which makes the system simple and reduces the initial investment.
Laboratory gas emission treatment
Because there are many toxic and acid-base corrosive gases in laboratory gas emissions, the gas should be filtered before being discharged into the atmosphere. Acid gas generally adopts vertical acid mist tower. Optical catalytic purification tanks are used to treat toxic and organic gases. The two devices are installed at the end of the exhaust system, the vertical acid mist tower is installed in the positive pressure area of the fan, and the photocatalytic purification box is installed in the negative pressure area of the fan. After preliminary and medium-efficiency filtration, the air in the animal house is directly discharged into the atmosphere, but high-pressure jet treatment is performed at the air outlet, and the jet height is greater than 3m.
The renovation of the laboratory ventilation system is a comprehensive task. Everyone must pay attention when doing this work. Do not look at this problem alone, because solving only one part of the problem is not obvious for the entire system transformation, so It still needs to be comprehensively and comprehensively transformed and improved.