Heating, air conditioning, ventilation and air purification systems in animal laboratories
动物实验,动物实验室
z-bo
2020-07-24
887
The environmental requirements of animal laboratories depend on the laboratory level. According to the classification of laboratory environment facilities, animal laboratories are divided into three levels: normal environment, isolated environment and isolated environment. A typical animal laboratory environment must meet comfort and control the laboratory ammonia concentration. In addition to the above requirements, barriers and isolated animal laboratories also need to ensure cleanliness, indoor pressure difference and maximum daily temperature difference. Therefore, the barrier and isolated animal laboratory HVAC system has the characteristics of a biologically clean air conditioning system.
One. Ventilation and air conditioning functions in animal laboratories
(1) Adopt outdoor air ventilation and air conditioning system
Generally, the density of animals raised in animal laboratories is high, and the air contains odors such as ammonia and hydrogen sulfide. It is a brand new direct injection ventilation
The air conditioning system can ensure that the concentration of ammonia in the air of the animal laboratory does not exceed the normal level, thereby ensuring the health of the laboratory animals.
(2) Large air volume
In addition to normal animal laboratories, clean animal (SPF animals and sterile animals) laboratories also need a clean barrier or isolation environment. A certain amount of air exchange must be performed to ensure the required air cleanliness.
(3) Large air conditioning load
Clean animal laboratory uses external air direct air-conditioning system and performs a large amount of air exchange. Therefore, its air-conditioning load is inevitably much higher than that of ordinary and comfortable air-conditioning systems. ..
(4) Advanced control requirements for ventilation and air conditioning systems
To ensure the accuracy of animal test results, a clean animal laboratory requires basically constant environmental conditions throughout the year. Even the temperature fluctuations during the day are below 4°C. This requires automatic control of the air conditioning system. According to the external weather conditions and the number of animals in the room, the air volume, cold air and heat of the air conditioning and ventilation system can be adjusted in time to keep the changes in laboratory environmental parameters within the allowable range of specifications. ..
(5) Waste gas must be treated and discharged
The exhaust gas of the animal laboratory contains ammonia, hydrogen sulfide and other toxic gases. Direct exhaust will have a negative impact on the environment around the laboratory. The exhaust gas must be treated to comply with regulations. The concentration can be released into the atmosphere.
(6) Large-area rooms with ventilation and air-conditioning equipment
The air conditioning load in the animal laboratory is large, the air conditioning load is large, the air duct size is large, and the equipment and facilities are large. The rooms and equipment occupy a large area.
(7) High construction and maintenance costs
The ventilation and air-conditioning equipment in the animal laboratory is very airtight, requires a lot of processing, requires a certain number of spare parts, and its cost should be high. In addition to the maintenance period of the equipment, the system also needs to operate 24 hours a year, and the energy consumption during operation is much higher than a typical ventilation system or a comfortable air conditioning system. Air-conditioning systems usually account for more than one third of the total cost of animal laboratory facilities, and operating energy consumption can reach 4/5 of the total cost of facilities,
二. Environmental requirements for animal laboratories
The Chinese standard "Animal Laboratory Environment and Equipment" (GB14925-2010) defines the environmental conditions of animal laboratories and animal laboratories. Therefore, when establishing an animal laboratory, it is necessary to meet the similarities and differences between national and local standards, and implement more stringent standards.
three. heating
(one) range
In addition to normal animal laboratories, clean animal laboratories are not allowed to install heating systems.
(two) system form
The heating system is best to use top air supply and return. Laboratory heating tubes should be placed overhead so that they are not placed in ditches that are difficult to repair.
(3) Control and adjustment of heating system
In order to realize the temperature control of the sub-room, it is necessary to install an automatic temperature control valve on the radiator. The heating system should adopt an adjustment method that combines quality adjustment and quantity adjustment.
(4) Matters needing attention
The animal laboratory must be equipped with a radiator heating system. Floor radiant heating systems are not suitable for use, because the laboratory often has drain pipes.
The heating medium should use cold and warm water to avoid scalding large-scale free-range animals and promote room temperature control.
We recommend the use of corrosion-resistant and easy-to-clean radiators, such as cast iron cylindrical radiators that can withstand weak acids such as ammonia. At the same time, it can be easily cleaned with water.
The water pipe valve should be placed in a higher position, and the automatic air release valve should be placed outside the laboratory to prevent the water valve from leaking and burning animals.
1. Load calculation In addition to the housing structure and surrounding air load, the air conditioning load must also include personnel, animals, laboratory equipment and lighting loads.
2. Calculation of air volume The ambient air volume must simultaneously meet the animal’s oxygen demand, deodorized air volume, cleanliness and the required pressure difference.
3. Pressure difference calculation The pressure difference must meet the pressure gradient requirements of the surrounding environment and adjacent rooms.
(2) Air conditioning system form
The animal laboratory mainly uses a single air duct, a constant air volume, and a full-wind DC air-conditioning system. If the air conditioning system supports multiple laboratories and has different usage requirements, a variable air volume air conditioning system can also be used.
(3) Air purification
In a general animal laboratory, it is necessary to install primary and medium-efficiency air filters in the air conditioning unit. Clean animal experiments should be installed in the air-conditioning device with primary, intermediate and low-efficiency air filters, and installed high-efficiency air filters in the exhaust outlet.
(four) airflow organization
The airflow organization of the animal laboratory should ensure the formation of a uniform temperature field, velocity field and minimum temperature gradient in the room.
In a barrier environment, the airflow in a typical and clean animal laboratory is usually turbulent. The air cleanliness of the barrier environment reaches level 7 (level 10,000). Small animal laboratories usually provide air at the top of the room and exhaust at the four lower corners or bottom. Large animal laboratories usually supply air at the top of the room and return air at the top or center of the room. In a clean animal laboratory in an isolated environment, the airflow organization often forms a vertical or horizontal laminar flow in the breeding cage or isolator, and the cleanliness can reach level 5 (level 100).
5. Ventilation
(1) exhaust
The air volume of general animal laboratory is usually 8-10/h ventilation. The displacement of the clean animal laboratory must be determined by calculation based on the amount of fresh air in the air conditioner and the pressure gradient in the room.
(II) Waste gas treatment
The waste gas of animal laboratories contains unpleasant malodorous gas, so animal laboratories installed in cities must discharge them after treatment. Commonly used exhaust treatment methods include activated carbon adsorption, acid mist purification tower absorption, high-voltage electrostatic decomposition, and UV photolysis purification.
1. Activated carbon adsorption device Activated carbon adsorption uses a large surface area and small carbon particle pores, that is, capillaries that attach gas to the solid surface. The normal adsorption of activated carbon is physical adsorption, and modified activated carbon also has chemical adsorption. Therefore, the adsorbability of activated carbon depends on the pore structure and chemical composition.
2. Acid mist purification tower Acid mist purification tower is a commonly used purification equipment in waste gas treatment projects. There are two types, "vertical" and "horizontal", most of which are made of glass fiber reinforced plastic with filler inside. The lye is used to neutralize and absorb the acid gas in the exhaust gas, and is suitable for the deodorization of ammonia, hydrogen sulfide, amine and other malodorous substances. If the filtration area is sufficient, the gas-liquid ratio is reasonable, and the chemical reaction is completed, the absorption and purification efficiency can reach 95%; the emission concentration of bad breath is less than 10ppm. Acid mist purification towers, fans and water pumps are usually provided by commercial suppliers.
3. The high-voltage electrostatic decomposer uses high-voltage static electricity to generate oxygen ion groups in the exhaust gas, and converts the odor in the exhaust gas into CO2, H2O, H2SO4 or partially oxidized compounds at room temperature and atmospheric pressure. Disassemble. The advantage of this method is that it has a good effect on odor processing, but the disadvantage is the lack of quantitative analysis data reports for practical applications, large investment and high operating costs, which may lead to the life of the "corona" tube and air pollution. The influence of factors such as the frequency of pre-filter replacement. influences. Please note that the reaction product H2SO4 corrodes the vent pipe. The high-voltage electrostatic decomposition device is shown in Figure 1-1-4.
4. The ultraviolet energy of the ultraviolet photolysis device and the high ozone uV of ultraviolet radiation radiate the molecular bonds of malodorous gas substances, and decompose the molecular bonds of ammonia and hydrogen sulfide to make them free atoms.
5. At the same time, the high-energy and high-ozone uV UV beam decomposes oxygen molecules in the air to produce free oxygen, that is, active oxygen. Free oxygen has an imbalance between positive and negative electrons and must be combined with molecular oxygen to produce ozone. UV + O2→OO * (active oxygen) O + O2→O3 (ozone), free ozone and pollutant atoms polymerize to form new harmless or low-risk substances, such as CO2, H2O.
(three) emissions
The exhaust gas discharged from the animal laboratory after treatment must still be discharged at high altitude. The vent must be 3m higher than the roof of the laboratory.
6. Control and adjust ventilation and air conditioning systems
The automatic control of the ventilation and air-conditioning system in the animal laboratory is the key to ensuring the safe, reasonable and energy-saving operation of the laboratory. The automatic control system must be complete, reliable, rapid adjustment and precise control. The content of automatic control mainly includes: temperature and humidity control, room pressure gradient control, air conditioning and ventilation system operation mode and operation mode conversion control, system startup sequence and interlock control, blower. And the exhaust fan frequency conversion speed regulation control, automatic backup fan input control in case of failure, etc.
