Disclosure of Invention
In view of the above, the present invention is directed to provide a separation, purification and collection device for xenon in an air sample, which has the characteristics of reasonable layout and easy operation, and is suitable for efficiently and rapidly transferring, purifying, separating and collecting millilitre xenon in a hectoliter level pre-concentrated air sample obtained from a cubic meter level air sample, thereby satisfying the measurement requirements of a gas detector on radioactive xenon in a large number of air samples.
The invention specifically adopts the following technical scheme:
a separation, purification and collection device for xenon in an air sample is characterized by comprising: the device comprises a transfer unit, a separation and purification unit, a collection unit and auxiliary units, wherein the transfer unit is connected with the separation and purification unit, the separation and purification unit is connected with the collection unit, and the auxiliary units are respectively connected to the transfer unit, the separation and purification unit and the collection unit;
the transfer unit comprises a high-low temperature box of a transfer column and the transfer column arranged in the high-low temperature box of the transfer column, and refrigerant conveying pipes and heating pipes are tightly arranged on two sides of the transfer column;
the separation and purification unit comprises a thermal conductivity detection module, a reserved column heating furnace, a purification column heating furnace, a separation column heating furnace, and reserved columns, purification columns and separation columns which are respectively arranged in the reserved column heating furnace, the purification column heating furnace and the separation column heating furnace;
the collecting unit comprises a collecting column heating furnace and a collecting column arranged in the collecting column heating furnace;
the auxiliary unit comprises a vacuum pump connected with the transfer unit, the separation and purification unit and the collection unit, a steel bottle connected with the flow washing gas and a storage bottle connected with the collection column.
Further, the transfer column is a stainless steel tube filled with active carbon; the purification column is a stainless steel tube with a built-in 4A molecular sieve, is preferably spiral, is beneficial to miniaturization of the device, and realizes the adsorption of impurity gases such as water vapor, carbon dioxide and the like in a sample at normal temperature; the separation column is a stainless steel pipe with a built-in 5A molecular sieve, is preferably spiral, is beneficial to miniaturization of the device, realizes separation of xenon from other impurity gases under normal temperature conditions, and makes collection of high-purity xenon samples possible; the collecting column is a stainless steel tube filled with active carbon, is preferably U-shaped, is beneficial to miniaturization of the device, and realizes the collection of milliliter-scale high-purity xenon at normal temperature.
Further, the transfer column is a U-shaped spiral pipe. The high-low temperature box of transfer post is exclusively used in the quick temperature rise and fall of transfer post, is equipped with a pair of U type groove aluminum plate in, closely laminates tightly at the refrigerant conveyer pipe and the heating pipe of transfer post both sides with two U type groove aluminum plates with transfer post and distribution and presss from both sides tightly, and wherein the low temperature conduction oil is chooseed for use to the refrigerant, and the heating pipe adopts electrical heating for the refrigeration and the intensification of transfer post are simple easily obtained, convenient operation.
Furthermore, low-temperature heat conducting oil is filled in the refrigerant conveying pipe, and the heating pipe is electrically heated.
Furthermore, the thermal conductivity detection module structure mainly comprises a heat conductor, a signal processing board, an electric heating element, a temperature measurement sensor and a temperature control system, wherein the heat conductor comprises four symmetrical chambers containing thermosensitive elements, the four thermosensitive elements form a Wheatstone bridge, the Wheatstone bridge is connected with the signal processing board, the four chambers are divided into two reference chambers and two measurement chambers, the reference chambers only pass through carrier gas flow, and the measurement chambers pass through mixed gas flow of the carrier gas and a gas sample to be measured. The thermal conductivity detection module greatly reduces the treatment capacity of the purification column and the separation column, reduces the column material filling capacity of the purification column and the separation column, saves the treatment time of the whole process, enables the collection column to collect a small amount of pure xenon in the pre-concentrated air sample in time, optimizes the column material filling capacity of the collection column, reduces the xenon loss, improves the xenon recovery rate, and is favorable for the retransfer and physical measurement of the xenon sample in the later-stage collection column; when the device is used for quantitative analysis, the full-process yield of the separation, purification and collection device can be determined, so that technical support is provided for optimizing the process operation parameters.
Furthermore, the reserved column structure is a U-shaped stainless steel hollow tube, and the volume of the hollow tube is equal to the volume of pure xenon contained in the pre-concentrated air sample.
Further, the vacuum pump pumping speed was 4 liters per second.
Furthermore, the steel cylinder is a stainless steel cylinder and is used for cleaning the gas detector, the volume of the steel cylinder is 125 times of the volume of the gas detector, and the steel cylinder is filled with high-purity helium which is slightly lower than the highest using pressure of the gas detector.
Further, the temperature rise rate of the reserved column heating furnace, the purification column heating furnace, the separation column heating furnace and the collection column heating furnace is 25-40 ℃/min.
Furthermore, the file bottle is a stainless steel bottle and is used for temporarily storing a pure xenon sample during heating desorption of the collecting column, and the volume of the file bottle is 10-20 times of that of the gas detector.
The device for separating, purifying and collecting xenon in the air sample comprises a transfer unit, a separation and purification unit, a collection unit and an auxiliary unit, and solves the problems of complex treatment process and long time consumption of a small amount of xenon in the air sample with cubic meter magnitude in the traditional technology. The device for separating, purifying and collecting the xenon in the air sample can transfer, purify, separate and collect the milliliter xenon in the hectolitre air sample pre-concentrated to the ten-cubic-meter air sample within 1h, meets the requirement of a gas detector on sample measurement, realizes the quick and efficient sampling of the xenon in the cubic-meter air sample, and provides a solid technical support for the emergency monitoring of the radioactive xenon by the radioactive xenon isotope sampling monitoring with short response time and large dynamic range.
Detailed Description
The present invention will be described in further detail with reference to the following examples and fig. 1.
The device for separating, purifying and collecting xenon in an air sample is shown in figure 1, wherein V1-V17 are ball valves, P1-P7 are pressure sensors, TV 1-TV 4 are three-way valves, FV 1-FV 2 are four-way valves, and SV 1-SV 3 are six-way valves, and specifically the device comprises: the device comprises a transfer unit, a separation and purification unit, a collection unit and auxiliary units, wherein the transfer unit is connected with the separation and purification unit, the separation and purification unit is connected with the collection unit, and the auxiliary units are respectively connected to the transfer unit, the separation and purification unit and the collection unit;
the transfer unit comprises a high-low temperature box 8 of the transfer column and the transfer column 3 arranged in the high-low temperature box of the transfer column, and refrigerant conveying pipes and heating pipes are tightly arranged on two sides of the transfer column 3;
the separation and purification unit comprises a thermal conductivity detection module 1, a reserved column heating furnace 7, a purification column heating furnace 9, a separation column heating furnace 10, and a reserved column 2, a purification column 4 and a separation column 5 which are respectively arranged in the reserved column heating furnace, the purification column heating furnace and the separation column heating furnace;
the collecting unit comprises a collecting column heating furnace 11 and a collecting column 6 arranged in the collecting column heating furnace;
the auxiliary units comprise a vacuum pump 12 connected with the transfer unit, the separation and purification unit and the collection unit, a small steel bottle 13 connected with the flow washing gas and a storage bottle 14 connected with the collection column.
The thermal conductivity detection module greatly reduces the treatment capacity of the purification column and the separation column, reduces the column material filling capacity of the purification column and the separation column, saves the treatment time of the whole process, enables the collection column to collect a small amount of pure xenon in the pre-concentrated air sample in time, optimizes the column material filling capacity of the collection column, reduces the xenon loss, improves the xenon recovery rate, and is favorable for the retransfer and physical measurement of the xenon sample in the later-stage collection column; when the device is used for quantitative analysis, the full-process yield of the separation, purification and collection device can be determined, so that technical support is provided for optimizing the process operation parameters. Furthermore, the thermal conductivity detection module 1 works on the principle that different gas components and concentrations have different thermal conductivity coefficients with the carrier gas, the change of the heat conductivity coefficient can cause the change of the output signal of the chromatographic detection module, can clearly indicate the change of the components of the gas sample to be detected, and is used for the on-line monitoring of the separation, purification and collection process, according to the outflow sequence and retention time of different components in the air sample from the transfer column 3, the purification column 4 and the separation column 5, a peak cutting technology is adopted, and a large amount of non-xenon gas components in the pre-concentrated air sample can be emptied in time by switching valves, so that the aims of quickly and efficiently transferring, purifying, separating and collecting millilitre xenon in a hectoliter pre-concentrated air sample obtained from a cubic meter air sample are fulfilled, and preparation is made for retransferring and measuring the xenon sample in the subsequent collection column 6. Firstly, during the low-temperature transfer process of a hectolitre level pre-concentrated air sample from an external cubic meter level air sample to a transfer column 3, a large amount of non-xenon gas components are directly exhausted, after the low-temperature transfer is finished, a vacuum pump 12 is started, the transfer column 3 at low temperature is subjected to pipeline buffer type pressure relief, the transfer column 3 is connected into a chromatographic main flow path, and a thermal conductivity detection module 1 monitors the component outflow condition of the transfer column on line; then, washing the desorbed transfer column 3 with high-purity helium carrier gas, continuously and directly emptying components of non-xenon gas, monitoring the component outflow condition of the transfer column 3 on line by the thermal conductivity detection module 1, switching four-way valves FV1 and FV2 when a chromatogram shows that a large amount of components of non-xenon gas in an air sample are emptied, sequentially connecting the purification column 4 and the separation column 5 in series behind the transfer column 3, further purifying and separating the rest air sample of the transfer column through the purification column 4 and the separation column 5 under the normal temperature condition, continuously monitoring the gas component outflow condition of the separation column 5 on line by the thermal conductivity detection module 1, and continuously and directly emptying the components of non-xenon gas; then, when the transfer column 3 is at the xenon desorption temperature, the collection column 6 is connected in series to the measuring component outflow part of the thermal conductivity detection module 1 by switching the six-way valve SV3, the purified and separated xenon is collected by the collection column 6, and redundant non-xenon gas components are emptied; and finally, when the thermal conductivity detection module 1 detects that the xenon component in the transfer column 3 is completely desorbed on line and no xenon component flows out from the separation column 5, stopping collection.
Furthermore, the structure of the preformed column 2 is a phi 1/8 stainless steel hollow pipe, preferably U-shaped, the volume of the preformed column is equal to the volume of pure xenon contained in the pre-concentrated air sample, the preformed column can be used for quantitative analysis of a thermal conductivity detection module, when the flow of separating, purifying and collecting xenon in the actual air sample is simulated, the initial content of the pure xenon is provided, and then the concentration of the xenon desorbed into an archive bottle by the collecting column is measured, so that the recovery amount of the pure xenon in the simulated flow is obtained, the full-flow yield of the separating, purifying and collecting device is determined, and technical support is provided for optimizing the flow operation parameters.
Further, the transfer column 3 is a phi 1/2 stainless steel pipe with built-in activated carbon, preferably in a U shape, and is installed in the high and low temperature box 8 of the transfer column, the high and low temperature box of the transfer column is specially used for rapid temperature rise and fall of the transfer column, a pair of U-shaped groove aluminum plates are arranged in the high and low temperature box, the transfer column and refrigerant conveying pipes and heating pipes which are distributed on two sides of the transfer column are tightly attached and clamped by two U-shaped groove aluminum plates, wherein low-temperature heat conducting oil is selected for the refrigerant, and the heating pipes are electrically heated, so that refrigeration and temperature rise of the transfer column are simple and easy to obtain. The requirements of low-temperature adsorption, high-temperature desorption and transfer of xenon in a hectolitre level pre-concentrated air sample from an external cubic meter level air sample are met within the temperature range of-30 ℃ to 300 ℃, the desorption temperature can be accurately controlled, xenon adsorbed by a transfer column is completely desorbed, radon possibly existing is not desorbed, the requirement on xenon adsorption capacity is met, the xenon adsorption, desorption and transfer operations are simple and easy, the active carbon filling amount of the transfer column 3 is effectively reduced, the volume of a high-low temperature box 8 of the transfer column is reduced, the power consumption is reduced, and the processing time of the whole process is saved.
Further, the purification column 4 is a phi 1/4 stainless steel tube filled with a 4A molecular sieve, preferably a spiral type, which is beneficial to miniaturization of the device and realizes adsorption of impurity gases such as water vapor, carbon dioxide and the like in the sample at normal temperature.
Further, the separation column 5 is a phi 1/4 stainless steel tube filled with a 5A molecular sieve, preferably a spiral type, which is beneficial to the miniaturization of the device, realizes the separation of xenon from other impurity gases at normal temperature, and makes the collection of high-purity xenon samples possible.
Furthermore, the collecting column 6 is a phi 1/8 stainless steel tube filled with active carbon, preferably a U-shaped stainless steel tube, which is beneficial to the miniaturization of the device and realizes the collection of milliliter-scale high-purity xenon at normal temperature.
Furthermore, the temperature rise rate of the reserved column heating furnace 7, the purification column heating furnace 9, the separation column heating furnace 10 and the collection column heating furnace 11 is 25 ℃/min-40 ℃/min, and the moderate heating power is favorable for accurately controlling the temperature of the purification column, the separation column and the collection column during heating, ventilating, activating and regenerating, so that the effectiveness and the high efficiency of activating and regenerating are ensured; the collecting column is favorable for rising to the desorption temperature in a short time when being heated and desorbed, the temperature can not overshoot greatly, the collecting column can be controlled accurately, xenon adsorbed by the collecting column can be completely desorbed, radon which possibly exists can not be desorbed, the accuracy and precision of the later-stage radioactive xenon physical measurement are ensured, and the processing time of the whole process is also shortened.
Further, the pumping speed of the vacuum pump 12 is several liters per second, for example, 4 liters per second, so that the separation, purification and collection device can be quickly pumped to the expected vacuum degree, and the processing time of the whole process is saved.
Further, the steel cylinder 13 is a stainless steel cylinder and is used for cleaning the gas detector, the volume of the steel cylinder is 125 times of the volume of the gas detector, high-purity helium which is slightly lower than the highest using pressure of the gas detector is filled in the steel cylinder, the pressure impact of the flow scrubbing gas on the gas detector is reduced through the decompression cache of the high-purity helium, the safe use of the gas detector is ensured, the requirement of miniaturization of the device is met, the gas detector can be continuously cleaned for more than 30 times at the pressure slightly higher than the normal pressure, the influence of the memory effect on the measuring accuracy of the gas detector is eliminated in a short time, and the influence of the cleaning operation on other functional operations of the separation, purification and collection device is reduced to the minimum; below 100kPa, it is necessary to replenish the cylinder 13 with high purity helium gas to a pressure slightly below the maximum use pressure of the gas detector.
Further, the file bottle 14 is a stainless steel bottle for temporarily storing the pure xenon sample when the collection column 6 is heated and desorbed, and the volume of the file bottle is several times, such as 10 to 20 times, of the volume of the gas detector.
The invention also provides a xenon separation, purification and collection method based on the xenon separation, purification and collection device for the air sample, which specifically comprises the following steps:
a) activation regeneration treatment of column
a1) Introducing carrier gas and flowing through a mass flow controller MF1, and setting the flow rate of a mass flow controller MF 1;
a2) switching on the power supply of the separation, purification and collection device, and switching valves to discharge carrier gas from the valve V7 after the carrier gas flows through the transfer column 3, the purification column 4, the separation column 5 and the collection column 6;
a3) respectively setting the activation temperatures of the transfer column 3, the purification column 4, the separation column 5 and the collection column 6, and introducing carrier gas to heat, activate and regenerate the transfer column 3, the purification column 4, the separation column 5 and the collection column 6; after reaching the respective activation temperature of the transfer column 3, the purification column 4, the separation column 5 and the collection column 6, preserving the heat until the activation is complete, and stopping heating;
a4) and when the temperatures of the transfer column 3, the purification column 4, the separation column 5 and the collection column 6 are all reduced to room temperature, switching valves to enable the transfer column 3, the purification column 4, the separation column 5 and the collection column 6 to be in a closed state, and preparing to enter a transfer process of xenon in the pre-concentrated air sample.
b) Transfer of xenon from a preconcentrated air sample
b1) Starting refrigeration of a high-low temperature box 8 of the transfer column, resetting the flow of a mass flow controller MF1, and starting a power supply of a thermal conductivity detection module 1 to be in a state to be analyzed;
b2) when the temperature of the transfer column 3 reaches the set xenon adsorption temperature, the three-way valve TV2 is in a state of connecting a hectoliter level pre-concentration air sample obtained from a cubic meter level air sample from the outside with the transfer column 3, the xenon flow in the pre-concentration air sample is washed and adsorbed to the transfer column, the three-way valve TV3 is switched to a venting state in a delayed mode, and a large amount of non-xenon gas components are directly evacuated;
b3) after the transfer of the hectolitre pre-concentrated air sample from the outside, which is obtained from the cubic meter-level air sample, is completed, the refrigeration of the high-low temperature box 8 of the transfer column is turned off, and the three-way valves TV2 and TV3 are switched to the state connected to the six-way valve SV 2. Thus completing the transfer of xenon in the hectoliter level pre-concentration air sample and preparing the flow of separating, purifying and collecting xenon in the air sample entering the transfer column 3.
c) Separation, purification and collection of xenon from air samples in transfer columns
c1) Under the condition that the transfer column 3 is at a low temperature, the valves V6 and V16 are alternately switched on and off, the pipeline is evacuated by the vacuum pump 12, the pipeline buffer type pressure relief is carried out on the transfer column 3, and then the valves V6 and V16 are in a closed state;
c2) setting the heating temperature of the transfer column 3 to be 0 ℃, alternately switching on and off the valves V6 and V16 again, evacuating the pipeline by using the vacuum pump 12, continuing to perform pipeline buffer type pressure relief on the transfer column 3, then switching the six-way valve SV2 to connect the transfer column 3 into a main chromatographic flow path, performing flow washing by using high-purity helium carrier gas, starting online monitoring of the component outflow condition of the transfer column 3 by the thermal conductivity detection module 1, and directly evacuating a large amount of non-xenon gas components in the air sample;
c3) setting the desorption temperature of the transfer column 3, switching four-way valves FV1 and FV2 when a chromatogram shows that a large amount of non-xenon gas components in an air sample are exhausted, sequentially connecting a purification column 4 and a separation column 5 behind the transfer column 3 in series, further purifying and separating the air sample of the remaining transfer column 3 through the purification column 4 and the separation column 5, continuously monitoring the outflow condition of process components on line by the thermal conductivity detection module 1, and directly exhausting the large amount of non-xenon gas components in the air sample;
c4) when the transfer column 3 reaches the desorption temperature, the six-way valve SV3 is switched, the collection column 6 is connected in series to the position where the measurement component of the thermal conductivity detection module 1 flows out, the thermal conductivity detection module 1 monitors the flow condition of the process component on line, meanwhile, the collection column 6 collects xenon in the air sample, and a large amount of non-xenon components in the air sample are directly evacuated;
c5) when the thermal conductivity detection module 1 monitors that the xenon component of the transfer column 3 is completely analyzed on line, the six-way valve SV3 is switched to stop collecting, and the transfer column 3 stops heating. Thus completing the separation, purification and collection of xenon in the air sample of the transfer column.
Further, the method comprises the following steps:
d) desorption and inflation process for xenon sample in collecting column
d1) The three-way valve TV4 is switched to point to the direction of a mass flow controller MF2, a vacuum pump 12 is opened, valves V8, V13, V15, V9 and V16 are opened and closed alternately, the vacuum pump 12 is used for evacuating a pipeline, pipeline buffer type pressure relief is carried out on the collecting column 6, then the vacuum pump 12 is closed, and valves V8, V9, V13, V15 and V16 are closed;
d2) setting the resolving temperature of the collecting column 6, heating to the resolving temperature, keeping the temperature, setting the flow rate of a mass flow controller MF2, opening valves V8, V9 and V12, slowly washing the collecting column 6 by flowing washing gas, filling a gas detector with high-purity xenon of the collecting column 6, closing V8, V9 and V12 when a pressure sensor P5 shows that the pressure is slightly lower than the normal pressure, stopping heating the collecting column 6, setting the flow of the mass flow controller MF2 to be 0, and filling the xenon into the gas detector for the subsequent measurement of the xenon by the gas detector.
Further, in the steps b 2) to b 3) and the steps c 2) to c 5), the high-low temperature transfer technology is adopted to transfer xenon in the hectolitre level pre-concentrated air sample from the outside and obtained from the cubic meter level air sample, and the specific processes of rapidness, high efficiency and easy operation are as follows: the transfer column 3 is a phi 1/2U-shaped stainless steel tube filled with activated carbon, the stainless steel tube is installed in a high-low temperature box 8 of the transfer column, the high-low temperature box 8 of the transfer column is specially used for quickly heating and cooling the transfer column 3, a pair of U-shaped groove aluminum plates are arranged in the high-low temperature box, the transfer column 3 and refrigerant conveying pipes and heating pipes which are distributed on two sides of the transfer column 3 are tightly attached and clamped by two U-shaped groove aluminum plates, low-temperature heat conduction oil is selected for the refrigerant, and the heating pipes are electrically heated, so that the required high and low temperature of the transfer column 3 in the transfer process is quickly and easily obtained. The invention adopts a high-low temperature transfer technology, realizes the requirements of low-temperature adsorption, high-temperature desorption and transfer of xenon in a hectolitre level pre-concentrated air sample from an external cubic meter level air sample within the range of-30 ℃ to 300 ℃, can also accurately control the desorption temperature, completely desorbs xenon adsorbed by a transfer column, and does not desorb radon possibly existing, thereby not only meeting the requirement of xenon adsorption capacity, but also ensuring that the adsorption, analysis and transfer operations of xenon are simple and easy, effectively reducing the filling amount of active carbon of the transfer column 3, reducing the volume of a high-low temperature box 8 of the transfer column, reducing the power consumption and saving the processing time of the whole flow.
Further, in the steps c 2) to c 4), the specific operation of directly exhausting a large amount of non-xenon components in the air sample is as follows: the thermal conductivity detection module 1 monitors the outflow condition of process components on line, adopts a peak cutting technology, and evacuates a large amount of non-xenon gas components in the pre-concentrated air sample in time by switching valves according to the outflow sequence and retention time of different components in the pre-concentrated air sample through the transfer column 3, the purification column 4 and the separation column 5, so as to achieve the purpose of quickly and efficiently transferring, purifying, separating and collecting milliliter-level xenon in a hectolitre-level pre-concentrated air sample obtained from a cubic meter-level air sample, and prepare for the retransfer and measurement of the xenon sample in a subsequent collection column.
Further, the peak cutting technology adopted by the thermal conductivity detection module 1 can timely evacuate a large amount of non-xenon gas components in the sample in the following specific process: firstly, during the low-temperature transfer process of a hectolitre level pre-concentrated air sample from an external cubic meter level air sample to a transfer column 3, a large amount of non-xenon gas components are directly exhausted, after the low-temperature transfer is finished, a vacuum pump 12 is started, the transfer column 3 at low temperature is subjected to pipeline buffer type pressure relief, then the transfer column 3 is connected into a chromatographic main flow path, and a thermal conductivity detection module 1 monitors the component outflow condition of the transfer column on line; then, washing the heated transfer column 3 with high-purity helium carrier gas, directly emptying non-xenon gas components, switching four-way valves FV1 and FV2 when a chromatogram shows that an air peak in an air sample returns to a chromatographic baseline, sequentially connecting a purification column 4 and a separation column 5 in series behind the transfer column 3, further purifying and separating the rest transfer column air sample through the purification column 4 and the separation column 5 under the normal temperature condition, adsorbing water vapor and carbon dioxide, separating xenon from other impurity gases, and directly emptying the non-xenon gas components; then, when the transfer column 3 is at the desorption temperature, the collection column 6 is connected in series to the measuring component outflow part of the thermal conductivity detection module 1 by switching the six-way valve SV3, the collection column 6 is used for collecting xenon in the air sample, and redundant non-xenon gas components are emptied; finally, when the thermal conductivity detection module 1 detects that the effluent component xenon peak of the transfer column 3 returns to the chromatographic baseline on line, the collection is stopped.
Further, in the step d), a micro-flow control technology is adopted, so that the gas filling process of the high-purity xenon sample is accurately controlled, and the method specifically comprises the following steps: firstly, a pipeline is evacuated by a vacuum pump, and pipeline buffer type pressure relief is carried out on a collecting column, so that the impurity gas in an inflation pipeline is ensured to be minimum, and the influence on subsequent measurement is minimum; then, heating the collecting column to a desorption temperature, keeping the temperature, setting the flow rate of a mass flow controller MF2, adopting a micro-flow control technology, opening valves V8, V9 and V12, slowly washing the collecting column by flow washing gas, filling high-purity xenon in the collecting column into a gas detector, enabling the pressure of a pressure sensor P5 to slowly rise at the speed of hundred pascals per second, closing V8, V9 and V12 when a pressure sensor P5 shows that the pressure is slightly lower than the normal pressure, stopping heating the collecting column, setting the flow of the mass flow controller MF2 to be 0, and enabling the xenon filled in the gas detector to be used for measuring the subsequent xenon. The use of micro-flow control technology not only ensures the sufficient desorption of xenon in the collecting column, but also can be fully filled into the gas detector, and meets the pressure use requirement of the gas detector.
When the method is used for simulating the separation, purification and collection process of xenon in an actual air sample, the initial content of pure xenon can be provided, and the concentration of the xenon desorbed into the filing bottle by the collection column is measured to obtain the recovery amount of the pure xenon in the simulation process, so that the full-process yield of the separation, purification and collection device is determined, and the substantial technical support is provided for optimizing the process operation parameters. The specific process of determining the process yield of the separation, purification and collection device by the reserved column 2 is as follows: firstly, simulating the purification, separation and collection processes of xenon in an actual air sample, selecting a reserved column 2 with the volume equal to that of pure xenon contained in the air sample, introducing the pure xenon sample from the outside under the normal temperature condition, enabling the pure xenon sample to flow through a purification column 4 and a separation column 5, and then collecting the pure xenon sample by a collection column 6; then, the desorption and gas filling process of the high-purity xenon sample is simulated, the collecting column 6 is heated to the desorption temperature, the pure xenon sample desorbed from the collecting column 6 is slowly washed by high-purity helium and filled into the filing bottle 14, and finally, the concentration of xenon in the filing bottle 14 is measured to obtain the recovery amount of the pure xenon in the simulated process, so that the process yield of the separation, purification and collection device is calculated, and technical support is provided for optimizing the process operation parameters.
Example 1
In this embodiment 1, the separation, purification and collection device for xenon in the air sample is formed by connecting a stainless steel pipe, a valve, a mass flow controller and a pressure sensor according to a flow diagram, wherein the stainless steel pipe is an inner polished stainless steel pipe, and the mass flow controller MF1 has a flow range of 0-1L/min and a precision of 0.1%; the flow range of the mass flow controller MF2 is 0-70 mL-min, precision 0.1%; the pressure ranges of the absolute pressure sensors P1, P2, P3, P4 and P6 are 0-600 kPa, the pressure range of the absolute pressure sensor P5 is 0-200 kPa, and P7 is a vacuum gauge; the integral vacuum degree of the device is not more than 10Pa, and the pressure drop is not more than 0.5kPa.h under the positive pressure condition of 0.5MPa-1This embodiment is rationally distributed, easy to maintain and change. The temperature control ranges of the reserved column heating furnace 7, the purification column heating furnace 9, the separation column heating furnace 10 and the collection column heating furnace 11 are 15-400 ℃, the temperature rise rate is 25-40 ℃/min, and the temperature control precision is not more than +/-5 ℃.
The device of the embodiment is used for the device with the volume of 10m3The separation, purification and collection of xenon in an air sample of (1), comprising the steps of:
a) activation regeneration treatment of column
a1) Introducing carrier gas and flowing through a mass flow controller MF1, and setting the flow rate of the mass flow controller MF1 to be 50 ml/min;
a2) switching on a main power supply of the separation and purification collecting device, switching a six-way valve SV2, a four-way valve FV1, an FV2 and a six-way valve SV3, switching three-way valves TV2 and TV3 to the direction of communicating the six-way valve SV2, switching a three-way valve TV1 to the direction of communicating the thermal conductivity detection module 1, opening a valve V7, and discharging carrier gas from a V7 after the carrier gas flows through a transfer column 3, a purification column 4, a separation column 5 and a collecting column 6;
a3) respectively setting the activation temperatures of the transfer column 3, the purification column 4, the separation column 5 and the collection column 6 as 300 ℃, 350 ℃ and 300 ℃, connecting the power supplies of the high-low temperature box 8 of the transfer column, the purification column heating furnace 9, the separation column heating furnace 10 and the collection column heating furnace 11, and connecting carrier gas to heat and activate the regeneration transfer column 3, the purification column 4, the separation column 5 and the collection column 6; after reaching the respective activation temperature of the transfer column 3, the purification column 4, the separation column 5 and the collection column 6, preserving the heat until the activation is complete, and stopping heating;
a4) when the temperatures of the transfer column 3, the purification column 4, the separation column 5 and the collection column 6 are all reduced to room temperature, the six-way valve SV2, the four-way valve FV1, the FV2 and the six-way valve SV3 are switched to enable the transfer column 3, the purification column 4, the separation column 5 and the collection column 6 to be in a closed state, and the transfer process is ready to enter.
b) Transfer of xenon from a preconcentrated air sample
b1) Opening the high-low temperature box 8 of the transfer column for refrigeration, setting the flow of the mass flow controller MF1 to be 200 ml/min, and opening the power supply of the thermal conductivity detection module 1 to be in a state to be analyzed;
b2) when the temperature of the transfer column 3 reaches below minus 30 ℃, the three-way valve TV2 is in a state that a hectolitre level pre-concentration air sample obtained from a cubic meter level air sample from the outside is connected with the transfer column, a xenon flow in the pre-concentration air sample is washed to the transfer column by using high-purity helium carrier gas, and the three-way valve TV3 is switched to an emptying state after delaying for a few seconds;
b3) when the xenon in the pre-concentrated air sample has been completely flushed to the transfer column, the transfer is stopped, the refrigeration of the transfer column 3 is stopped and the three-way valves TV2 and TV3 are switched to a state in which they are connected to the six-way valve SV 2.
c) Separation, purification and collection of xenon from air samples in transfer columns
c1) When the transfer column 3 is at low temperature, alternately switching on and off the valves V6 and V16, evacuating the pipeline by using the vacuum pump 12, performing pipeline buffer type pressure relief on the transfer column 3 until a vacuum gauge P7 shows that the pressure is below 20kPa, and closing V6 and V16; in the step c, setting the pumping speed of the vacuum pump to be 2L/s;
c2) setting the heating temperature of the transfer column 3 to be 0 ℃, alternately switching on and off V6 and V16 again when the pressure sensor P2 shows that the pressure exceeds 100kPa, evacuating the pipeline by using a vacuum pump 12, carrying out pipeline buffer type pressure relief on the transfer column 3 until a vacuum gauge P7 shows that the pressure is below 20kPa, then switching over a six-way valve SV2 to connect the transfer column 3 into a main chromatographic flow path, carrying out flow washing by using high-purity helium carrier gas, and starting online monitoring on the component outflow condition of the transfer column 3 by using a thermal conductivity detection module 1 to directly evacuate the non-xenon gas component;
c3) the temperature of the transfer column 3 is set to 300 ℃, when the chromatogram shows that the air peak is in a completely descending trend, the situation that a large amount of non-xenon gas components in the air sample are emptied is shown, four-way valves FV1 and FV2 are switched, the purification column 4 and the separation column 5 are sequentially connected in series behind the transfer column 3, the air sample of the rest transfer column 3 passes through the purification column 4 and the separation column 5 to be further purified and separated, and the non-xenon gas components are continuously and directly emptied;
c4) when the temperature of the transfer column 3 reaches 300 ℃, the six-way valve SV3 is switched, the collecting column 6 is connected in series to the position where the measurement component of the thermal conductivity detection module 1 flows out, the collecting column 6 is used for collecting xenon in the air sample, and redundant non-xenon gas components are emptied;
c5) when the thermal conductivity detection module 1 monitors the outflow component of the transfer column 3 on line and shows that the xenon peak drops to the baseline level, the six-way valve SV3 is switched to stop collecting and the transfer column 3 stops heating. Thus completing the separation, purification and collection of xenon in the air sample of the transfer column.
Further, in order to transfer the xenon in the separated and purified air sample to a gas detector for a subsequent xenon measurement process, the method of the embodiment further comprises the following steps:
d) desorption and inflation process for xenon sample in collecting column
d1) The three-way valve TV4 is switched to point to the direction of a mass flow controller MF2, a vacuum pump 12 is opened, valves V8, V13, V15, V9 and V16 are opened and closed alternately, the vacuum pump 12 is used for evacuating a pipeline, pipeline buffer type pressure relief is carried out on the collecting column 6, then the vacuum pump 12 is closed, and valves V8, V9, V13, V15 and V16 are closed;
d2) setting the analysis temperature of the collecting column 6 to 300 ℃, heating to 300 ℃, setting the flow rate of a mass flow controller MF2 in the range of 1 ml/min-5 ml/min, adopting a micro-flow control technology, opening valves V8, V9 and V12 to enable the flow-scrubbing gas to slowly flow and scrub the collecting column by high-purity helium, filling the high-purity xenon in the collecting column 6 into a gas detector, closing V8, V9 and V12 when a pressure sensor P5 shows that the pressure is about 95kPa, stopping heating the collecting column 6, setting the flow rate of the mass flow controller MF2 to be 0, and enabling the xenon filled in the gas detector to be used for measuring the subsequent xenon.
The embodiment pair is composed of 10m3The time for transferring the pre-concentrated air sample of about one hundred liters obtained from the air sample to the transfer column can be controlled within 1h, and the time for separating, purifying and collecting the xenon in the air sample in the transfer column does not exceed 40 min. Therefore, compared with the problems of complex processing process and long time consumption of a small amount of xenon in a cubic meter level air sample in the traditional technology, the device realizes the rapid and efficient transfer, purification, separation and collection of milliliter-level xenon in a hectoliter level pre-concentrated air sample obtained from the cubic meter level air sample, and meets the requirement of meeting the requirement of the prior art on the condition that the milliliter-level xenon is rapidly and efficiently transferred, purified, separated and collectedThe gas detector has the advantages of meeting the requirement of measuring a small amount of radioactive xenon in a large amount of air samples and solving the urgent need of monitoring radioactive xenon isotopes.
The described embodiment of the invention is only one of the possibilities that is easy to implement. All relevant embodiments are exemplary and not exhaustive, and the invention is in no way limited to only these embodiments. Many modifications and variations are possible and apparent without departing from the scope and spirit of embodiments of the invention.