RU2542265C1 - Sieve tray of dip type for mass-transfer apparatus working in "gas-liquid" and "gas-liquid-liquid" systems - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: sieve tray contains horizontal plate with uniformly arranged sieves, through which in upward direction the gas phase passes and liquid phase passes in downward direction. The horizontal plate is made out of two connected plates. Each plate has asymmetrically installed elements of two sieve types: one sieve element has form of round sieve-valve connected to the plate with posts, pressed from the plate together with sieve-valve, the other sieve element is in form of the round sieve-hole with overall dimension ensuring installation in the sieve-hole with minimum clearance of the sieve-valve of the another plate. On the top plate the sieve-valves look down symmetrically to the sieve-holes in the bottom plate, and in the bottom plate the sieve-valves look up symmetrically to the sieve-holes of the top plate.

EFFECT: increased efficiency of phases contact, increased throughput capacity of the tray.

3 dwg

Description

Failure type sieve plate for mass transfer apparatus working in gas-liquid and gas-liquid-liquid systems, which can be used in oil refining, chemical, petrochemical, food and other industries, in particular for distillation and absorption separation mixtures of organic and inorganic substances, for example, when fractionating a mixture of two mutually insoluble liquids.

A failure-type strainer plate is known for mass transfer apparatuses operating in gas-liquid systems, including a horizontal sheet with uniformly distributed screens through which the gas phase passes from top to bottom and the liquid phase from top to bottom (Skoblo A.I., Tregubova I.A. , Egorov NN Processes and apparatuses of the oil refining and petrochemical industry. M: Gostoptekhizdat, 1962, 200 p.). The main disadvantage of such plates is the narrow range of loads in the gas and liquid phases, since at a low plate load the liquid phase fails from the overlying plate to the underlying one almost without phase contact, and at a high plate load it chokes — in both cases, the plate has an effective mass-transfer action decreases sharply. In addition, the efficiency of mass transfer on the plate as a whole is determined by the efficiency of the local counterflow of gas and liquid phases through a single sieve opening and is significantly lower than in the case of countercurrent contact of the gas and liquid phases on sieve plates with drain transfer devices.

Also known is a failure-type plate for mass-exchangers operating in gas-liquid systems, including a horizontal sheet with uniformly distributed screens, through which the gas phase passes and from top to bottom the liquid phase equipped with a safety overflow device, the height of which above the plate blade corresponds the maximum permissible fluid level on the canvas (certificate for utility model RU No. 29671 U1, B01D 3/18, B01D 3/20, B01D 3/22, 05.27.2003).

The main disadvantage of the analogue is the uneven spreading of the liquid phase from the overflow device on the underlying failure sieve plate, as a result, it becomes necessary to install an additional distribution device with a gear overflow plate, which leads to an increase in the metal consumption of the failure plate and more than double the height of the mass transfer apparatus to accommodate overflow devices and switchgears without increasing the mass transfer efficiency of the apparatus as a whole.

Closest to the claimed invention and considered as a prototype is a failure-type sieve plate for mass-exchangers operating in gas-liquid systems, including a horizontal web of parallel strips through which the gas phase passes from top to bottom and the liquid phase from top to bottom, this strip is made curved in a sinusoid and shifted relative to each other by half a wavelength, forming a sieve (copyright certificate for the invention SU No. 748939, B01D 3/22, 07/10/1999). The disadvantage of this invention is the structural complexity of mounting the plates, since a slight displacement of the essentially parallel corrugated strips relative to each other in the horizontal and especially in the vertical plane will lead to a significant change in the vertical cross-section of the slots between adjacent plates and the violation of the uniformity of the flow of gas and liquid phases, passing through these gaps, in terms of costs, speeds and degree of dispersion.

When creating the invention, the task was to increase the efficiency of contact of the gas and liquid phases on the failed contact devices of the sieve type and to increase the throughput of the plate by changing the organization of contact in the sieves from countercurrent to local cross-flow and expanding the boundaries of the stable operation of the plate, as well as during mass transfer between gas and two immiscible liquids.

The problem is solved due to the fact that in a sieve plate of a failure type for mass transfer apparatuses operating in the "gas - liquid" and "gas - liquid - liquid" systems, including a horizontal canvas with uniformly distributed sieves, through which the gas phase passes from bottom to top and from top to bottom the liquid phase, a horizontal web is formed of two bonded webs, each web has asymmetrically arranged elements of two types of screens, one screen element has a shape in the form of a round-shaped sieve valve, sk replicated with the fabric with legs squeezed out of the fabric together with the sieve valve, another element of the sieve is made in the form of a sieve-hole of round shape with a dimension that allows you to insert a sieve-valve of another fabric into the sieve-hole with a minimum clearance, on the upper fabric sieve-valves facing downwards symmetrically to sieve openings in the lower sheet, and in the lower sheet sieve valves facing upwards symmetrically to sieve openings in the upper sheet.

The proposed sieve failure plate due to the specific design - the presence of sieve valves - in the horizontal section has essentially doubled the expansion of the working height of the blade plate in the assembly. This will significantly expand the boundaries of the stable operation of the plate. With a high specific load of the plate in the liquid phase, excess liquid will additionally fill the lower sieve valves, through which the liquid phase will flow onto the underlying plate through additional distribution devices, preventing the overlying plate from flooding. With a low specific load of the plate in the liquid phase, the liquid will predominantly fill the lower sieve valves, contacting them countercurrently with the gas phase, not allowing the liquid phase to fall onto the underlying plate. Under normal plate specific load, gas and liquid phase flows intensify mass transfer on the plate by increasing the quality of gas bubbling near the sieve valve due to the increase in the gas phase passing through the gap between the plate blade and the valve compared to the gas phase passing through the sieve hole. For example, for a dry plate, when the gas phase passes through a slot of a sieve valve with a width of 2 mm and a diameter of a sieve valve of 20 mm, compared with the passage of the gas phase through a sieve hole with a diameter of 20 mm, the gas phase velocity increases by 2.5 times. The possibility of the liquid phase flowing from the zone of the sieve valve facing up to the area of the adjacent sieve valve facing down leads to the formation of double contact of one portion of the liquid phase with adjacent flows of the gas phase, which should lead to the formation of a local cross-flow mode of hydrodynamics of the mesh plate intensifying mass transfer. In cases where the gas-liquid-liquid system is separated on a sieve plate, for example, fractionation of partially soluble liquids, then on a sieve plate, a higher density liquid will interact with gas in downstream sieve valves and a lower density liquid in sieve valves facing up.

The figure 1 shows a horizontal canvas of a sieve failure plate of two sheets fastened together with sieve-valves assembly.

Figure 2 shows a horizontal canvas of a sieve failure plate made of two sheets fastened together with sieves-valves in a disassembled form: separately the upper and lower sheets.

The figure 3 shows a fragment of a horizontal canvas sieve failure plate of two fastened together paintings with sieves-valves, assembled in a vertical section and a horizontal section of a sieve valve on AA sieve failure plates with round valves, where 1 is the upper canvas, 2 is the lower canvas , 3 - sieve-valve, 4 - valve head, 5 - valve foot, 6 - sieve-hole.

Comparative bench tests of a sieve failure plate with round valves with a diameter of 20 mm and a leg height of 4 mm according to the claimed invention with a classical failure plate, the sieves of which are made in the form of holes of a circular shape with a diameter of 4 mm and a rectangular shape of 4 × 20 mm with the same live section level of 20% of the area of the plate.

The results of bench tests of a sieve failure plate with round valves according to the claimed invention showed that a sieve failure plate with round valves provides:

- an increase in gas throughput by 10%, an increase in the mass transfer efficiency in the gas-liquid system by 10% (the effectiveness was assessed visually by changing the porosity and increasing the height of the foam);

- extension of the lower limit of the range of stable operation of the plate (the beginning of the liquid back-up by an upward flow of gas) by 10%, and the upper limit of the range of stable operation from 100% (design value) to 115% (cessation of runoff and the beginning of the liquid reflux to the next plate). Thus, the range of stable operation of the plate increased by 25%.

An analysis of the hydrodynamic features and the results of experimental bench tests of the developed dip sieve plate confirm that the claimed invention solves the problem of increasing the efficiency of contact of the gas and liquid phases on the sieve contact devices of the sieve type and increasing the throughput of the plate by changing the contact organization in the sieves from countercurrent to local crossflow and expanding the boundaries of the stable operation of the plate, as well as during mass transfer between a gas and two, do not mix liquids.

Claims (1)

A failure type strainer plate for mass transfer apparatuses operating in the gas-liquid and gas-liquid-liquid systems, including a horizontal sheet with uniformly distributed sieves, through which the gas phase passes from top to bottom and the liquid phase from top to bottom, characterized in that a horizontal web is formed from two webs fastened together, each web has asymmetrically arranged elements of two types of screens, one screen element has a shape in the form of a round-shaped sieve-valve fastened with a leg si squeezed out of the fabric together with the sieve valve, another sieve element is made in the form of a circular sieve hole with a dimension that allows you to insert another sieve valve into the sieve hole with a minimum clearance, the sieve valves on the upper sheet are symmetrically facing down sieve holes in the lower sheet, and in the lower sheet, the sieve valves face upwards symmetrically to the sieve holes in the upper sheet.

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