1 Introduction
Indoor environmental quality is the most important environmental factor affecting human health. Indoor air pollutants vary in type and quantity with changes in the location, type, use, and outdoor air pollution conditions of the building. An effective way to solve this problem is to add air purification equipment indoors. According to relevant information, the air purification equipment currently used is generally poor in purifying a variety of pollutant gases, such as carbon dioxide and body odor released from the human body, and water produced in the kitchen. Steam and carbon monoxide, complex gas pollutants produced during smoking. In addition, many types of contaminants are difficult to clean with current air purification equipment. Based on the above reasons, this study proposes the use of activated carbon fiber filter to purify indoor polluted gases. The performance and characteristics of activated carbon fiber filters are systematically studied. The effects of various factors on filter filtration efficiency under different polluted air conditions are discussed. The application of activated carbon fiber in indoor air purification provides a scientific basis and lays a foundation for the research and development of indoor air purifiers.
Activated carbon fiber filter (hereinafter referred to as filter) is made of activated carbon fiber felt or fiber cloth. This material is superior to activated carbon (GAC) with highly developed microporous structure, large adsorption capacity and large external surface area (about 10 for GAC). ~100 times), the speed of suction and desorption is fast, and the purification effect is good. The filter design dimensions are 282mm x 282mm x 120mm. When the filtered air volume is 260m3/h, the design wind speed is 0.91m/s, the filtration speed is 0.172m/s, and the filter material is 0.44m2 (the effective area of ​​the filter is 0.42m2). In order to facilitate processing and reduce the cost, the filter frame is made of plastic plate, the filter material is supported by 207# nylon mesh and wire mesh, and the edge of the filter material is bonded with the plastic frame by glass glue to seal it. Its structure is shown in Figure 1.
2, the performance test of the filter
2.1 Test Flow Chart
The performance test procedure for the filter is shown in Figure 2.
The air volume of the sampler is controlled at 1L/min, and the sampling time and flow rate are recorded during sampling.
2.2, test methods
2.2.1, filter resistance test
Close the fresh air outlet, open the return air valve, start the fan, control the fan air volume by adjusting the gate valve of the main air duct, and then adjust the filter wind speed of the filter. The fan air volume is determined by measuring the wind speed by a thermoelectric anemometer connected to the main air duct. The resistance of the filter is determined by the differential pressure of the static pressure ring set before and after it, and the static pressure is read by the tilting micromanometer.
2.2.2 Test of the total removal efficiency of various polluting gases by filters
(1) Pollution gas test and sampling analysis method
It is taken once every minute); NH3 is prepared by concentrated ammonia water volatilization method.
In the experiment, the sampling tube is first installed at the measuring hole before and after the filter, and the sampling tube is connected with the atmospheric sampler. Then, a certain concentration of certain polluted gas is prepared in the laboratory, and the fan is mixed for 2 minutes, and the fan is turned on to adjust the required air volume. According to the different contents of the performance test research, different conditions were set and the concentration of the polluted gas before and after the filter was measured. The test sequence is as follows: after the fan is started, the filter inlet is sampled for 5 min first, and the concentration is used as the inlet concentration of the filter. Then, the average concentration of the filter outlet after 5 minutes of operation of the fan is measured to determine the total removal efficiency of the filter. .
Total filter removal efficiency:
3, filter performance test results and analysis
3.1 Filter resistance test results and analysis
The change of filter resistance with the wind speed of the main air duct is shown in Figure 3.
It can be seen from Fig. 3 that the resistance of the filter increases with the increase of the wind speed of the air duct, which is almost linear. When the air volume of the filter is the design air volume (ie, Q=260 m3/h, the wind speed of the air duct is 2.82 m/s, and the filter speed is 17.20 cm/s), the filter resistance is about 20 Pa.
3.2 Filter test results and analysis of pollutant removal efficiency
3.2.1 in the same pollution conditions
The average concentration of the filter outlet after 5 minutes of fan opening for different air volumes was measured for 5 min, and the polluting gas removal efficiency was calculated. The result is shown in Figure 4.
From Fig. 4, the air volume and efficiency curve show that: 1SO2, NOX polluted gas has the highest removal efficiency and the optimal filter speed of the filter corresponding to the same concentration and different air volume. The maximum removal rate of the filter to the inlet concentration of 1.555mg/m3 is 90.4%, the optimum filtration rate is 12.50cm/s, the optimum air volume is 189m3/h, and the highest removal of NOX with the concentration of 2.506mg/m3. The rate is 76.58%, the optimum filtration rate is 12.50cm/s, and the efficiency of the filter is 157.6~251.6m3/h. 2 The low air volume removal rate is low, mainly due to the low air output of the fan. Although the filtration efficiency of the filter is improved, the relative unpurified gas is more. After one cycle, the concentration of the pollutant in the room after the purified gas is mixed with the unpurified gas. Still high, the removal efficiency after 20 minutes of startup was affected. However, if the filter is not filtered by a certain amount of air, the polluted gas will reach a certain maximum removal efficiency, and the result is uneconomical. Therefore, choosing the optimal start-up time, optimal filtered air volume and optimum gas removal efficiency have important practical significance for the study of activated carbon fiber filters.
3.2.2 A certain concentration of polluted gas at different boot times with different air volumes
The average concentration of the gas at the outlet of the filter after the fan was turned on for 10, 20, 30, 40, 50, and 60 minutes was measured, and the total removal efficiency of the polluted gas in each time period was calculated. The test results are shown in Figure 5 and Figure 6.
It can be seen from Fig. 5 and Fig. 6 that when the air volume of the same concentration of polluted gas is constant, the removal efficiency of the polluted gas increases with the extension of the fan opening time, and finally tends to an equilibrium value. The airflow through the filter is 189~226m3/h, and the pollution gas removal efficiency curve is the most ideal. Generally, when the filter inlet concentration is not too high, the fan can be turned on for 20~30min to meet the indoor environmental quality requirements.
3.2.3, the filter air volume is certain, the concentration of pollutant gas is different
The average concentration of the gas at the outlet of the filter after the fan was turned on for 20 minutes was measured, and the removal efficiency of the filter under different filter inlet concentrations was calculated. The test results are shown in Figures 7 and 8.
It can be seen from Fig. 7 and Fig. 8 that in the specified purification time range, the gas removal efficiency of the filter increases with the increase of the concentration of the polluted gas, but when the concentration of the polluted gas reaches a certain value, the efficiency has Reduced. This shows that activated carbon fiber has a high removal rate of high concentration of polluted gas in a certain period of time, but the net air volume per cycle is certain, that is, the amount of polluted gas processed in a certain period of time is certain, with indoor manufacturing pollution The concentration is increased, and even if the removal efficiency of the filter is high, the circulation and mixing of the gas within a fixed time also affect the total removal efficiency. Therefore, for a low concentration of polluted gas, a short opening time can be used for rapid purification, and when the concentration of the polluted gas is high, the fan opening time can be extended to achieve an optimal removal effect of the purifier. The filter has a concentration range of optimal removal efficiency for different kinds of polluted gases within a certain period of time. Within this range, the purification equipment can be opened for a certain period of time to meet the indoor environmental quality requirements, if the concentration range is marked on the gas filter Will be convenient for the user's choice.
3.2.4 The same concentration of polluted gas changes in time before and after the fan is turned on, and the concentration before and after the filter changes with time.
Burn 0.1g, 0.5g of sulfur, and mix the fan for the first 5min, the second 5min, the third 5min, the fourth 5min filter before and after the gas average concentration, calculate the removal of each time period effectiveness. The measurement results are shown in Fig. 9 and Fig. 10.
It can be seen from Fig. 9 and Fig. 10 that the filter adsorption filter gas law is: (1) For the low concentration gas, the first 5 min treatment efficiency is higher, and the inlet concentration decreases before the saturation, and the efficiency is in a downward trend. The longer the boot time, the greater the cumulative removal efficiency, but the accumulation rate is reduced, so the turn-on time is not as long as possible, too long, and the power consumption is not necessarily obvious. (2) For the high concentration gas, the removal rate of the first 5 min is relatively low, and then the efficiency of the second 5 min increases with the decrease of the concentration, and the efficiency decreases gradually when the concentration drops again. The removal efficiency increases with the increase of gas concentration, but when it increases to a certain value, the removal efficiency starts to decrease with the increase of concentration, and a peak appears in the middle, indicating that the high concentration of pollutant gas should increase the fan opening time appropriately. Conducive to the removal of pollutants. The above two rules are in complete agreement with the previous results analysis.
3.2.5 Removal rate of CO and CO2 by filter
The experiment room ignites 6 cigarettes, each cigarette is sucked once every minute. After the smoke is exhausted, the electric fan is mixed for 2 minutes, and the purification device is turned on to adjust the air volume Q=157.6m3/h. At the filter inlet, a variety of gases are used. The detector measures the CO2 and CO gas concentrations through the longer CO2 and CO detection tubes. After 5 minutes and 20 minutes, the CO2 and CO gas concentrations are measured at the outlet of the filter. The results are shown in the attached table.
4, summary
(1) The resistance of the filter is linear with the wind speed of the duct.
(2) The removal efficiency of the filter for SO2 and NOX varies with the air volume of the filter. When the removal efficiency is the highest, the corresponding air volume of the filter is 189m3/h~226m3/h.
(3) The removal efficiency of the filter for SO2, NOX and other polluted gases increases with the removal time, and finally gradually tends to be flat. The optimum filtration rate of the filter does not change with changes in contaminant concentration.
(4) During the 20-min start-up time, the removal efficiency of SO2 and NOX gas in the filter increases with the increase of the concentration of the polluted gas, but when the concentration of the polluted gas reaches a certain value, the concentration increases, but the efficiency increases. Reduced. The filter has an optimal concentration range for the removal of SO2 and NOX.
(5) The filter has almost no removal effect on CO and CO2.