CS242560B1 - Device for determination of sorption properties of adsorbents at low temperatures and high pressures - Google Patents

Abstract

The solution concerns a device for determining the sorption properties of adsorbents at low temperatures and high pressures, for example for temperatures up to -118 °C and pressures up to 5.0 MPa, consisting of a liquid nitrogen reservoir /18/ and a cryostat vessel /1/, inside of which is located a heat exchanger /3/, a circulating air fan /4/, a measuring cell /5/with an inlet /12/ and an outlet /13/ and a platinum resistance thermometer /6/. In its lower part, a heating coil /7/, a resistance thermometer /8/ of the heating regulator and a resistance thermometer /9/ of the cooling regulator are placed. The heat exchanger /3/ with solenoid valve /10/, heating coil /7/, resistance thermometer /8/ of the additional heating regulator and resistance thermometer /9/ of the cooling regulator are connected to the measuring and regulating block, formed by the first converter /20/, the second converter /21/, the cooling regulator /23/ and the additional heating regulator /24/. The platinum resistance thermometer /6/ is connected to the third converter /22/, connected to the point recorder /25/ and the digital millivoltmeter /26/. The platinum resistance thermometer /6/ is further connected to a sampling container /14/ equipped with a sample collection point /15/ and connected to a nitrogen inlet /16/ and a connection /17/ to a vacuum pump, and the container /1/ of the cryostat is equipped with a lid /2/ and a connection /11/ to a pumping set, and the liquid nitrogen reservoir /18/ is connected to a connection /19/ to a pressure cylinder.

Description

The invention relates to a device for determining the sorption properties of adsorbents at low temperatures and high pressures.

To date, there are no known devices that would be used laboratoryly or industrially to determine the amount of substances that any adsorbent is capable of trapping in the low temperature region.

the process of air liquefaction is adversely affected by a number of substances contained therein, such as carbon dioxide, sulfur dioxide, hydrocarbons Οχ to Cg and water. During liquefaction, these substances may fall out or accumulate in the solid-phase plant, which in extreme cases may lead to an explosion for hydrocarbons. It is therefore necessary to remove the undesirable substances from the liquefied air beforehand. The actual removal of impurities can be carried out both at the beginning and during the process. Today, purification is mainly carried out by adsorption on the surface of the adsorbents. Silica gel is preferably used for this purpose.

Since the sorption capacity of the adsorbents used for air purification is not known, or the time and temperature necessary for their regeneration, the process of air liquefaction is adversely affected. This results in losses in the production itself and in the economic area. The lack of knowledge of the ability of adsorbents to adsorb undesirable substances present in the air at high pressures and low temperatures up to -170 ° C, which corresponds to the conditions of operation of the air liquefaction plant, does not allow their appropriate selection, appropriate reproducibility and thus economical process.

These drawbacks are eliminated by a device for determining the sorption properties of adsorbents at low temperatures and high pressures, e.g.

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- 2 ice for temperatures up to -118 ° C and pressures up to 5.0 MPa, according to the invention. It consists of a liquid nitrogen reservoir and a cryostat vessel, inside of which a heat exchanger, a circulating air fan, a measuring cell with inlet and outlet, a resistive platinum thermometer and a heating coil, a resistive thermometer of the regulator are located The heating coil and the resistance thermometer of the cooling regulator, the heat exchanger with solenoid valve, the heating coil, the resistance thermometer of the heating regulator and the resistance thermometer of the cooling regulator are connected to a measuring block consisting of the first transmitter, second converter, cooling regulator and heating regulator and platinum. connected to a third transducer connected to a point recorder and a digital millivoltmeter and a platinum resistance thermometer connected to a sampling vessel provided with a sampling point and connected to a nitrogen inlet and connected to a vu cryostat vessel and provided with a lid and the connection to the pump system and the reservoir of liquid nitrogen connected to the pressure connection of the bottle.

By means of the device according to the invention, it is possible to determine the amount of substances that any adsorbent is capable of retaining in the low temperature region. In the air liquefaction process, by knowing the ability of adsorbents to adsorb undesirable substances in the air at high pressures and low temperatures on the surface of the surface, the adsorbents can be selected appropriately, their reproducibility suitable, and the process economics appropriate.

The invention and its effects are explained in more detail in the description of a specific embodiment of the device according to the invention according to the accompanying drawing which illustrates a device for determining the sorption properties of adsorbents at low temperatures and high pressures according to the invention. determining the sorption properties of adsorbents at low temperatures and high pressures according to the invention described in the appended example.

The device according to the invention consists of a liquid nitrogen container 18 and a cryostat container 1 inside which a heat exchanger 2 is located

3 242 560 heat, a circulating air fan 6, a measuring cell ^{28 through an} inlet 12 and a drain and a resistance platinum thermometer 6. In its lower part there is a heating coil 2, a resistance thermometer 8 of the heating controller and a resistance thermometer% of the cooling controller. The heat exchanger 2 ⁸⁶ solenoid valve 10, the heating coil 2 »resistance thermometer 8 and heating controller RTD cooling controller 8 are connected to measurement and control unit comprising a first transducer 20, second transducer 21, controller 23 and cooling regulator 24 heating. A platinum resistance thermometer 6 is connected to a third transducer 22, connected to a point recorder 25 and a digital millivoltmeter 26. A platinum resistance thermometer 6 is also connected to a sampling vessel 14 provided with a sampling point 15 and connected to a nitrogen inlet 16 and a pump connection 17. The cryostate vessel 1 is provided with a lid 2 and a pump connection 11 and a liquid nitrogen container 18 is connected via a connection 19 to a cylinder.

The basic part of the apparatus is an air cryostat consisting of a double-shell glass container 1 of cryostat, for example a cylindrical shape β with a rounded bottom with an inner diameter of 250 mm and a height of the cylindrical part of 350 mm. The silver-plated cryostat container 1 is arranged, for example, in a 500 x 500 x 800 mm duralumin sheath. Between the vessel and the shell is a layer of polystyrene plates that fix the vertical position of the vessel and at the same time serve as an insulator. For example, the minimum thickness of the polystyrene insulation is 85 mm. Two circular openings are cut from the insulating plates and the duralumin sheath from the front and side, which serve to observe the measuring cell 2 ⁸ to illuminate the interior of the cryostat. The intercoat space of the cryostat glass container 1 is connected by a connection 11 with a pumping set which is able to pump the space up to a vacuum of 10 ~ Pa. The cryostat vessel 1 is provided with a lid 2. The lid 2 is formed by a copper plate to which the circulating air fan housing 6 is attached. Holes for four support rods are drilled into the bottom of the lid 2, which, in extension to the interior of the cryostat container 1, form a structure for mounting all the elements of the apparatus located inside the cryostat. Further, a hole in the tube is cut into the bottom of the vicar in which the union of the walls is a heat exchanger 3 and finally a circular opening for the circulating air fan 6.

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The space around the jacket of the circulating air blower 6 is thermally insulated with foamed polyurethane. The circulating air fan casing 6 is topped with an insulating layer also formed of foamed polyurethane. The cryostat cover 2 is attached to a supporting circular duralumin plate on which it is suspended in the cryostat. The support plate is covered on the underside with a thin layer of foam that prevents damage to the upper edge of the cryostat container 1. The cover 2 of the cryostat and the carrier plate drills the holes for the circulation fan shaft 6, the heat exchanger inlets and outlets and the inlet 12 and the outlet 13 of the measuring cell 2 and the opening for the electric wires of the control heating and resistance thermometer 8 of the heating and resistance thermometer 2 of the regulator. cooling.

A shaft bearing le of the circulating air fan 6 is mounted in a metal housing on the lid support plate 2. The carrier plate is thermally insulated from above by a layer of foamed polyurethane. After insertion into the lid 2 of the cryostat container 1, the wound plate is covered with a polystyrene plate and the slots are sealed with glass wool.

Another part of the cryostat is a cooling exchanger system in which liquid nitrogen is used as the coolant. ₊ Basic elements of the cooling circuit is a copper heat exchanger 2 in the form of a tube on whose surface is supplied with a number of copper wires, which increase the exchange surface. The heat exchanger 2 is fitted into a neon tube placed between the bottom of the cryostat cover 2 and a copper perforated plate mounted on the supporting rods of the bottom of the cryostat.

Pre-activated sorbent ^is weighed into the measuring cell 2 ⁱⁿ a manner known per se. The measuring cell 2 ^is purged with dry helium or argon to remove air humidity. The pump connection port 11 opens and the rotary pump evacuates the cryoplate housing. The cooling controller 23 and the heating controller 24 are set to the desired measurement temperature. The circulating air fan 6 is started. By pressurizing nitrogen from an external source, after opening the valve of the cylinder connection 19, wet cold nitrogen vapor is supplied to the heat exchanger 2. The temperature in the cryostat drops to the setting value on the cooling controller 23 and the heating controller 24. When the specific temperature is reached, it is maintained automatically. After the measurement temperature has stabilized with a resistance platinum 5 242 560 thermometer 2 mounted on the measuring cell 2, a gas stream containing adsorbate of known concentration is introduced into the cell. The adsorption gas exits from the measuring cell 2 via the outlet 13. In this gas, the adsorbate content is determined by a suitable method, for example an infantry analyzer or a gas chromatograph. At the same time, it is measured using a suitable volumetric meter. Various adsorption characteristics are obtained from the evaluated data obtained by the measurement according to the method of the invention, for example the time until the adsorbent penetration, the character of the penetration curve, the time to the adsorbent saturation with the adsorbate and so on.

In order to reduce heat losses to the crystals, the intercoat space of the cryostat container 1 is silvered so that the contents of the measuring cell 2 located in the cryostat container 1 can be observed through a window in the wall. placed from the side of the container.

An important part of the cryostat is the lid 2, whose primary function is to perfectly thermally insulate the internal space of the cryostat and its secondary task is to carry various structural and functional elements for cooling, measuring and regulation. By means of a circulating air fan 6, the cooling air is continuously circulated through a new tube with an exchanger inserted into the thermostat space. The circulating air fan 6 is driven by an electric motor. Due to the fact that the circulating air fan shaft 4 transfers cold from the cryostat space to the bearing, which consequently freezes, the circulating air fan bearing housing 4 is provided with an electric heater. The heating is realized by a ceramic sleeve mounted on the bearing housing, on which the cantalum resistance wire is wound. The heating intensity is regulated by the autotransformer as required. Liquid nitrogen is supplied to the cooling system from a liquid nitrogen container 18, in which, by means of self-evaporation, in a stabilized operation, a sufficiently high pressure is applied to the tern to push the liquid nitrogen into the heat exchanger 2. A constant pressure is maintained in the liquid nitrogen container 18 by means of a water manostat. The liquid nitrogen withdrawal from the liquid nitrogen reservoir 18 is controlled by the desired temperature in the cryostat and is controlled by the solenoid valve 10 at the outlet of the heat exchanger 2.

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A two-stage control is used to control the temperature in the cryostat, which controls cooling and heating separately. Cooling control is effected by admitting liquid nitrogen to the heat exchanger 2 via a solenoid valve 10, controlled by a temperature-controlled controller, which is sensed by a resistive platinum thermometer 6 located in a circulating cooling air stream. The heating control, which is realized by means of the resistance heating coil 2, is performed similarly, with the resistance thermometer 8 of the heating regulator placed downstream of the heating coil 2 ⁱⁿ the flow direction of the circulating atmosphere. cell 2 · Three additional resistance thermometers are mounted on the support rods of the internal design of the cryostat, at different heights, to monitor temperature gradients inside the cryostat. To facilitate the measurement and registration of temperatures, electrical transducers, such as a first transducer 20, a second transducer 21, and a third transducer 22, which convert the resistance signals into voltage signals, have been incorporated into the measuring circuits of the resistance thermometers. The output voltages from these transducers, proportional to the respective temperatures, are registered by a digital millimeter 26 and their time course is recorded by a dot recorder 25.

In this configuration, the cryostat can achieve the lowest controllable temperature of 85 K, the variation of which does not exceed 0.1 K. The maximum cooling rate is 2.8 ° C / min, the cooling of the cryostat from room temperature to -170 ° C takes 85 to 90 minutes. temperature changes from -170 to -180 ° C within ten minutes.

The measuring cell 2 where the adsorbent is placed is provided with inlet 12 and outlet 12 of the test mixture. A capillary is placed on the bottom of the measuring cell 2, which serves to suck the sample or the liquid phase resulting from the measurement. All three inlets of the measuring cell 2 are provided with stopcocks. The suction is connected to a sampling line, which consists of a sampling vessel 14 and a sampling point 15, from which a sample of the medium to be analyzed is taken with a syringe. The sampling vessel 14 serves, after evacuation by means of a vacuum pump, as a vacuum reservoir needed to evacuate the sample from the measuring cell 5.

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The analysis of samples can be performed in a number of ways, preferably using a gas chromatograph. Since the samples may contain very low concentrations of carbon dioxide, which cannot be determined with sufficient accuracy on a conventional type of thermally conductive gas chromatograph detector, a special analysis methodology is advantageously used which makes it possible to determine tens of thousands of percent of carbon dioxide in the sample. The method consists in that, after separation on a suitable chromatography column, the sample under test is led through a special hydrogenation catalyst, which is treated with hydrogen used as carrier gas, to hydrogenate the carbon dioxide present in the sample methane, which is then determined with high sensitivity by a flame ionization detector. gas chromatograph.

In practice, the adsorption capacity of silica gel to carbon dioxide was measured at -120 ° C. The measurement conditions were as follows: amount of silica gel 20 ml (14.6 g) Concentration of carbon dioxide in nitrogen 0.12% v / v measurement temperature -120 ° C, pressure 0.1 MPa, flow rate 550 ml / min. Breakthrough time C 2 9.4 h. The measured data indicate that the silica gel capacity under the given conditions up to the point of breakthrough is 15.8 ml / g.

Claims (1)

SUBJECT OF THE INVENTION 242 560 Apparatus for determining the sorption properties of adsorbents at low temperatures and high pressures, for example for temperatures up to -118 ° C and pressures up to 5.0 MPa, characterized in that it consists of a liquid nitrogen container (18) and a cryostat container (1) inside a heat exchanger (5), a circulating air fan (4), a measuring cell (5) and an inlet (12) and an outlet (15), a platinum resistance thermometer (6), and a heating coil (7) in the lower part thereof resistance thermometer (8) of the heating controller and resistance thermometer (9) of the cooling controller, the heat exchanger (5) with a solenoid valve (1Ω) heating coil (7), resistance thermometer (8) of the heating controller and resistance thermometer (9) of the cooling controller are connected to the measuring and control block consisting of the first converter (20), the second converter (21), the cooling controller (25) and the heating controller (24), and a platinum resistance thermometer (6) is connected to n to a third transducer (22) connected to a point recorder (25) and a digital millivoltmeter (26) and a resistance platinum thermometer (6) is connected to a sampling vessel (14) provided with a sampling point (15) connected to the inlet (16) and the cryostat receptacle (1) is provided with a cover (2) and a connection (11) to the pump set, and the liquid nitrogen container (18) is connected to a pressure bottle connection (19).