CN115683977A - Device and method for measuring radon adsorption saturation coefficient of activated carbon - Google Patents
Device and method for measuring radon adsorption saturation coefficient of activated carbon Download PDFInfo
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- CN115683977A CN115683977A CN202211322001.9A CN202211322001A CN115683977A CN 115683977 A CN115683977 A CN 115683977A CN 202211322001 A CN202211322001 A CN 202211322001A CN 115683977 A CN115683977 A CN 115683977A
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Abstract
The invention discloses a device and a method for measuring radon adsorption saturation coefficient of active carbon, wherein the device comprises a constant temperature and humidity box, a sealing tank, an active carbon box and a radon concentration measuring device, the radon concentration measuring device comprises a radon detector and a drying column, the active carbon box is arranged in the sealing tank, the sealing tank is arranged in the constant temperature and humidity box, the outlet end of the sealing tank is connected with the inlet end of the drying column, the outlet end of the drying column is connected with the inlet end of the radon detector, and the outlet end of the radon detector is connected with the inlet end of the sealing tank. The active carbon adsorption radon saturation coefficient detection device is simple in structure, the active carbon box adsorbing sufficient radon is exposed in the sealed tank, when the air radon concentration and the active carbon radon concentration of the sealed tank reach stability and do not change along with time, the active carbon adsorption radon saturation coefficient can be obtained by measuring the air radon concentration and the unit mass active carbon radon concentration of the sealed tank at the moment.
Description
Technical Field
The invention relates to the field of radon adsorption and radon concentration measurement, in particular to a device and a method for rapidly determining radon adsorption saturation coefficient of active carbon.
Background
The activated carbon is a porous carbon-containing substance, has a developed micropore structure and a large specific surface area, has strong adsorption capacity on a plurality of substances, and is widely applied to a plurality of fields such as air purification (the adsorption target gas is formaldehyde, ammonia, benzene, xylene, radon and the like), waste water treatment, radon measurement, radon-containing gas emission adsorption and the like. At present, the method for testing the gas-phase adsorption performance of the activated carbon with the most wide application adopts a carbon tetrachloride adsorption rate method. However, the detection result obtained has certain limitations because the adopted test gas is not the target gas.
In the air with constant radon concentration, when the radon activity accumulated by the activated carbon reaches a state of being stable and not changing along with time, which is called an adsorption saturation state, the adsorption saturation coefficient epsilon (m) of the activated carbon 3 /kg) is the ratio of the radon activity in unit mass of the active carbon to the radon concentration value in the air exposed by the active carbon under the adsorption saturation state, and the value can be used for well measuring the radon adsorption capacity of the active carbon and indirectly measuring the capacity of the active carbon for adsorbing other gases such as formaldehyde, ammonia, benzene, xylene and the like. Therefore, the device and the method for measuring the radon adsorption saturation coefficient of the activated carbon have important significance for judging the adsorption performance of the activated carbon and guiding the processing and production of the activated carbon.
Disclosure of Invention
The invention aims to provide a device and a method for measuring radon adsorption saturation coefficient of active carbon.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
the utility model provides an active carbon adsorbs survey device of radon saturation coefficient, its includes constant temperature and humidity case, seal pot, activated carbon box and radon concentration measurement device, radon concentration measurement device includes emanometer and dry post, activated carbon box establishes in the seal pot, and the seal pot is established in constant temperature and humidity incasement, and the exit end and the entry end of dry post of seal pot are connected, and the exit end and the entry end of emanometer of dry post are connected, and the exit end and the entry end of seal pot of emanometer are connected.
The method for measuring the radon adsorption saturation coefficient of the active carbon by adopting the measuring device comprises the following steps: will adsorb the feetThe active carbon box for measuring radon gas is exposed in the sealed tank and placed in the measuring device, and when the radon concentration of air and the radon concentration of active carbon in the sealed tank reach stable state and do not change with time, the radon concentration C of air in the adsorption saturation state is measured a And the radon concentration activity value C of the unit mass active carbon in the adsorption saturation state c Infinity according to C a 、C c Calculating to obtain the saturation coefficient epsilon of radon adsorption of the active carbon,
is calculated by the formula
The method for measuring the radon adsorption saturation coefficient of the activated carbon comprises the following steps:
step S1: baking the activated carbon to remove residual radon gas and moisture in the activated carbon;
step S2: filling the baked activated carbon into an activated carbon box, and weighing to obtain the weight of the activated carbon, which is recorded as m;
and step S3: placing the activated carbon box in a closed container filled with uranium ores for a plurality of days to enable the activated carbon to fully adsorb radon gas;
and step S4: taking out the activated carbon after the radon gas is completely adsorbed, placing the activated carbon in a sealed tank in an open state, and placing the sealed tank in a constant temperature and humidity box;
step S5: connecting the sealed tank, the drying column and the radon detector into a closed loop by using a plastic soft conduit, and coating composite high-temperature grease at each interface to prevent air leakage;
step S6: opening a constant temperature and humidity box, setting the temperature to a certain value, starting a radon measuring instrument after the temperature display reaches the set value, setting the radon measuring instrument to be in a measuring mode, and setting the period to be 1h;
step S7: observing radon concentration data recorded by a radon detector, when the radon concentration is basically stable and unchanged in at least 4 measurement periods, considering that the activated carbon is in an adsorption saturation state, stopping measurement, taking the average value of the last 3 stable data as the air radon concentration in the adsorption saturation state, and recording as C a ；
Step S8: taking out the activated carbon box, screwing a sealing cover, standing for 3.5-4 h, measuring the total gamma counting rate by using a BH1936 spectrometer, setting the measuring time to be 300s, and recording the counting rate after background deduction as n;
meanwhile, measuring the radon concentration activity value C of the unit quality activated carbon in the activated carbon box under the adsorption saturation state c (∞)；
Step S9: the radon saturation coefficient calculation expression of the activated carbon adsorption is
Wherein eta is the detection efficiency factor of the total count of the activated carbon box.
In order to reduce the error, the experiment can be carried out under the same condition according to the above experimental steps, and the average value of the results of the experiment is taken as the measured value of the adsorption saturation coefficient epsilon of the activated carbon under the condition.
Wherein, C according to the present invention c The (infinity) derivation equation is as follows:
the differential equation of radon concentration activity in unit mass of activated carbon changing with time is as follows:
in the formula, λ(s) -1 ) Decay constant of Radon, 2.1X 10 -6 s -1 ，C a (Bq/m 3 ) Is the radon concentration in air, C c (t) (Bq/kg) is the activity of radon per unit mass of activated carbon. k is a radical of formula 1 C a The radon activity measured by the adsorption of air into unit mass in unit time; k is a radical of formula 2 C c (t) is the amount of radon activity desorbed from a unit mass of activated carbon per unit time out of confinement and diffused into the air; lambda C c (t) is the amount of radon activity per unit time that decreases from a unit mass of activated carbon due to decay.
Assuming that fresh and clean activated carbon is in the air with constant radon concentration, the radon atom number in the activated carbon is zero at the initial moment of exposure, and the solution (1) is obtained
The formula is the cumulative radon concentration activity C in the active carbon with unit mass c In a time-dependent manner, the cumulative rate being
As can be seen from the above formula, the radon accumulating rate of the activated carbon is exponentially decayed, and the initial rate is k 1 Ca, exponential decay coefficient k 2 + λ, the accumulation rate tends to zero after a sufficiently long time, i.e.
The invention provides a device and a method for measuring radon adsorption saturation coefficient of active carbon, wherein the device is simple in structure, an active carbon box adsorbing sufficient radon gas is exposed in a sealed tank, and when the air radon concentration and the active carbon radon concentration of the sealed tank reach stability and do not change along with time, the adsorption saturation coefficient can be obtained by measuring the air radon concentration and the active carbon radon concentration of unit mass of the sealed tank. The method takes the target gas radon as the test gas, and the obtained detection result is more accurate and effective.
Drawings
FIG. 1 shows an apparatus for measuring an adsorption saturation factor of activated carbon according to the present invention.
Detailed Description
The invention is further explained by the following embodiments in conjunction with the drawings.
As shown in figure 1, a device for measuring saturation coefficient of radon adsorbed by activated carbon comprises a constant temperature and humidity box 1, a sealed tank 2, an activated carbon box 3 and a radon concentration measuring device, wherein the radon concentration measuring device comprises a RAD7 radon measuring instrument 4 and a drying column 5, the activated carbon box 3 is arranged in the sealed tank 2, the sealed tank 2 is arranged in the constant temperature and humidity box 1, the outlet end of the sealed tank 2 is connected with the inlet end of the drying column 5, the outlet end of the drying column 5 is connected with the inlet end of the RAD7 radon measuring instrument 4, and the outlet end of the RAD7 radon measuring instrument 4 is connected with the inlet end of the sealed tank 2.
In the invention, the constant temperature and humidity box is an LHS-100CL constant temperature and humidity box produced by Shanghai-Hengchun scientific instruments Co.
The sealing tank is a cylindrical sealing tank with the bottom surface diameter of 15cm and the height of 15cm, is made of a material with low radioactivity and difficult radon adsorption, and the upper top of the sealing tank is a cover which is provided with spiral threads and can be screwed and sealed tightly.
The diameter of the activated carbon box is 6 to 10 cm, the height is 3 to 5cm, and the top of the box is provided with a threaded, screwed and tightly sealed cover. The activated carbon box is filled with activated carbon, the surface of the activated carbon box is covered with a filter membrane, and the activated carbon box is arranged inside the sealed tank.
The drying column had a diameter of 6.7cm and a height of 28.9cm and was filled with 510 grams of anhydrous calcium sulfate desiccant.
The sealed tank, the drying column and the RAD7 radon measuring instrument are connected into a closed loop by adopting a plastic soft pipe, and the plastic soft pipe is a vinyl resin pipe with the inner diameter of 5 mm.
The method for measuring the activated carbon adsorption saturation coefficient by adopting the device comprises the following steps: the active carbon is enabled to fully adsorb radon gas, then the active carbon box is placed in a sealed tank in an open way and is placed in a measuring device, and the radon concentration C in air in an adsorption saturation state in the measuring device a Taking out the activated carbon box, screwing the sealing cover, and measuring the radon concentration activity value C of the activated carbon with single mass under the adsorption saturation state c Infinity according to C a 、C c And (infinity) calculating to obtain the adsorption saturation coefficient epsilon.
The determination method specifically comprises the following steps:
step S1: placing the activated carbon in an oven to bake for 6 hours, wherein the temperature is set to be 120 ℃ so as to remove residual radon gas and moisture in the activated carbon;
step S2: filling the baked activated carbon into an activated carbon box, and weighing to obtain the weight of the activated carbon (the weight of the activated carbon is subtracted from the total weight of the activated carbon and the box to obtain the weight of the empty box), and recording the weight as m;
and step S3: placing the activated carbon box in a closed container filled with uranium ores for a plurality of days to ensure that the activated carbon fully adsorbs radon gas, wherein the placing time is determined according to the size of the container and the radon precipitation rate of the uranium ores, and the good tightness of the container and the drying of the air in the container are ensured in the whole process;
and step S4: taking out the activated carbon after the radon gas is completely adsorbed, placing the activated carbon in a sealed tank in an open way, and placing the sealed tank in a constant temperature and humidity box;
step S5: connecting the sealed tank 2, the drying column and the RAD7 radon detector into a closed loop by using a plastic soft conduit, and coating composite high-temperature grease at each interface to prevent air leakage;
step S6: starting a constant temperature and humidity box, setting the temperature to be a certain value, starting a RAD7 radon measuring instrument after the temperature display reaches the set value, setting the measurement mode to be a sniff measurement mode, and setting the period to be 1h;
step S7: because the radon activity of the activated carbon box is in direct proportion to the gamma counting rate, the change trend of the radon concentration of the activated carbon along with time can be represented by a change curve of the gamma total counting rate of the activated carbon box along with time. Observing radon concentration data recorded by an RAD7 radon detector, when the radon concentration is basically stable and unchanged in at least 4 measurement periods (namely a variation curve of gamma total counting rate along with time tends to be stable), considering that the active carbon is in an adsorption saturation state, stopping measuring by the RAD7 radon detector, taking an average value of the last 3 stable data as the radon concentration of air in the adsorption saturation state, and recording as C a ；
Step S8: taking out the activated carbon box, screwing a sealing cover, standing for 3.5 hours, measuring the total gamma counting rate by using a BH1936 spectrometer, setting the measuring time to be 300s, and recording the counting rate after background deduction as n;
meanwhile, measuring the radon concentration activity value C of the unit quality activated carbon in the activated carbon box under the adsorption saturation state c (∞)；
Step S9: the adsorption saturation coefficient is calculated and expressed as
Wherein eta is a total count detection efficiency factor of the activated carbon box, and can be calibrated by a known experimental method; c c The value is the radon activity value of the unit mass active carbon in the adsorption saturation state; c a The radon concentration value of the air exposed by the active carbon in a saturated state is adsorbed;
in order to reduce the error, the experiment can be carried out for multiple times under the same condition according to the above experimental steps, and the average value of the results of the multiple experiments is taken as the measured value of the adsorption saturation coefficient epsilon of the activated carbon under the condition.
As a specific example of the present invention, the experiment was performed 5 times, and the specific test results are shown in table 1:
TABLE 1 test results
Claims (5)
1. The utility model provides an active carbon adsorption radon saturation coefficient's survey device, its characterized in that, it includes constant temperature and humidity case, seal pot, activated carbon box and radon concentration measurement device, radon concentration measurement device includes emanometer and dry post, the activated carbon box is established in the seal pot, and the seal pot is established in constant temperature and humidity incasement, and the exit end of seal pot is connected with the entry end of dry post, and the exit end of dry post is connected with the entry end of emanometer, and the exit end of emanometer is connected with the entry end of seal pot.
2. A method for measuring radon adsorption saturation coefficient of activated carbon using the measuring apparatus according to claim 1, wherein the activated carbon case adsorbing a sufficient amount of radon is exposed to the inside of the airtight container and placed in the measuring apparatus, and when the radon concentration in the airtight container and the radon concentration in the activated carbon are stabilized against time variation, the radon concentration C in the air in the adsorption saturation state is measured a And the radon concentration activity value C of the unit mass active carbon in the adsorption saturation state c (∞) according to C a 、C c Calculating to obtain the radon adsorption saturation coefficient epsilon of the active carbon,
is calculated by the formula
3. The method for determining radon saturation coefficient on adsorption by activated carbon according to claim 2, comprising the steps of:
step S1: baking the activated carbon to remove residual radon gas and moisture in the activated carbon;
step S2: filling the baked activated carbon into an activated carbon box, and weighing to obtain the weight of the activated carbon, which is marked as m;
and step S3: placing the activated carbon box in a closed container filled with uranium ores for a plurality of days to enable the activated carbon to fully adsorb radon gas;
and step S4: taking out the activated carbon after the radon gas is completely adsorbed, placing the activated carbon in a sealed tank in an open way, and placing the sealed tank in a constant temperature and humidity box;
step S5: connecting the sealed tank, the drying column and the radon detector into a closed loop by using a plastic soft conduit;
step S6: opening the constant temperature and humidity box, setting the temperature to a certain value, starting the emanometer after the temperature display reaches the set value, setting the emanometer to be in a measurement mode, and setting the period to be 1h;
step S7: observing radon concentration data recorded by a radon detector, when the radon concentration is basically stable and unchanged in at least 4 measurement periods, considering that the activated carbon is in an adsorption saturation state, stopping measurement, taking the average value of the last 3 stable data as the air radon concentration in the adsorption saturation state, and recording as C a ；
Step S8: taking out the activated carbon box, screwing a sealing cover, standing for 3.5-4 h, measuring the total gamma counting rate by using a BH1936 spectrometer, setting the measuring time to be 300s, and recording the counting rate after background deduction as n;
meanwhile, measuring the radon concentration activity value C of the unit quality activated carbon in the activated carbon box under the adsorption saturation state c (∞)；
Step S9: the radon saturation coefficient calculation expression of the activated carbon adsorption is
Wherein eta is the detection efficiency factor of the total count of the activated carbon box.
4. The method for determining radon adsorption saturation coefficient by activated carbon as claimed in claim 3, wherein in step S5, a compound high temperature grease is coated at each interface to prevent air leakage.
5. The method for determining radon adsorption saturation coefficient of activated carbon according to claim 3, wherein the same procedure is adopted to conduct a plurality of experiments under the same conditions, and the average value of the results of the plurality of experiments is taken as the measured value of the radon adsorption saturation coefficient ε of activated carbon under the conditions.
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| CN116499925B (en) * | 2023-06-30 | 2023-09-15 | 苏州巨联环保有限公司 | Method for testing adsorption saturation degree of activated carbon |
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