SU1459686A1 - Heat-mass exchange apparatus - Google Patents

Abstract

The invention relates to instrumentation of heat and mass transfer in a gas-liquid system and can be used to carry out the processes of absorption, desorption, drying and purification of gas in the chemical, petrochemical, food and related industries. The goal is to increase work efficiency and improve the technological design of the film heat and mass transfer apparatus. The device contains a vertical body 1 with pipes 2, fixed in tube sheets 3 and 4, and means 5 for supplying liquid to pipes 2. The upper part is tightly § Liquid (L Ü 4 SP with Oi 00 sz: 21 Teparonosi 20) Liquid

Description

valves 7 are inserted in the form of two elements of an arc profile, the space between which is divided by a partition of a linear or curvilinear section. The free edges of the elements of the arc profile at the level of the ends of the pipes 2 have cuts, the areas over which are bent away and facing in the form of stop-guiding canopies, forming vertical vertical feeding channels. The device operates in the descending mode of the motor phase at a gas velocity in pipes up to 30 m / s. 1 hp f-ly, 5 ill., 2 tab.

one

The invention relates to the instrumentation of heat and mass transfer in a gas-liquid system and can be used to carry out heat-stressed products, absorption, desorption and gas dehydration in chemical, petrochemical and adjacent industrial fields, in particular, efficient use of the device is possible in the production of sulfuric acid. at the stage of absorption of sulfur trioxide.

The purpose of the invention is to increase the efficiency of operation by distributing the liquid-phase in two streams and improving the processability of the design.

FIG. 1 shows the proposed apparatus, a longitudinal section; in fig. 2 - distributor with a linear cross-section, axonometric; in fig. 3 - distributor with curved cross-section, top view; in fig. 4 - distributor sweep; in fig. 5 is a schematic of a device for the manufacture of distributors.

The heat and mass transfer apparatus comprises a vertical body 1 comprising pipes 2 fixed in tube sheets 3 and 4, means 5 for supplying fluid thereto, for example, a nozzle, which is installed in a distribution chamber 6 above liquid distributors 7. The latter are tightly inserted in the upper part of the tubes 2. The apparatus is mounted on the collector-separator 8. The distributor 7 is made of sheet material and is formed by two elements of an arc profile that are tightly inserted into the tube. The cylindrical space between them is divided by a partition 10 of a linear (Fig. 2) or curved (Fig. 3) section, the vertical edges 11 of which are connected to diametrically located edges 12 of the elements 9 of the arc profile. The free edges of the 13 elements 9 of the arc profile are provided with horizontal cuts 14 at the level of the upper ends of the pipes. The rectangular portions located above them are bent outwards in the form of stop guides 15 with the formation of vertical supply channels 16. When distributors are installed in pipes, the lower edge of the hoods serves as a movement limiter in the vertical direction. Bent out of sweep

(Fig. 4) the valve has spring properties, so that it is easily installed and securely fixed in the tube of the apparatus. The shape of the supply channel 16 provides a tangential smooth fluid inlet to the distributor 7 and the pipe 2. The stop guides 15, along with their main function, act as dampers for the liquid on the tube sheet 3.,. Heat and mass transfer apparatus equipped with nozzles 17-22 for the input and output of gas, liquid and coolant, respectively.

Distributors 7 can be easily

5 are made of rectangular shaped blanks (FIG. 4) in a flexible manner on the collar (FIG. 5). A blank is inserted into the slot 23 of the gate 24 of the machine. Thereafter, the collar is reported to rotate. Interacting with pressure rollers 25,

0 billet takes the form of a distributor. After the bend of the stop guides, the distributor is ready.

The simplicity of manufacturing distributors 7 in combination with the possibility of using tubing of commercially available standard heat and mass exchangers. provides high manufacturability of the design. Heat and mass transfer apparatus operates as follows.

The fluid through the pipe 19 is supplied

0 to the nozzle 5, which sprays it over the cross section of the apparatus with the formation of a small level above the surface of the tube sheet 3. The main part of the liquid, having passed the channels 16 of the distributors 7, flows down in the form of a film along the inner surface

5 pipes. Gas is introduced through the nozzle 17 into the upper part of the distribution chamber 6. Here it interacts with the spray nozzle, captures another part of the liquid in the form of droplets, and distributes

tubes of the apparatus, passage through the distributors 7. Due to the high gas flow rate (up to 30 m / s) and the presence of turbulent pulsations in it, a short distance from the entrance to the tube, liquid drops fall on the wall, where they merge with the flowing film. At the same time, the process of detachment of droplets from the crests of waves formed on the surface of the film, which are entrained in the gas stream core, takes place. The processes of dropping with a liquid film and their detachment from the wave crests in the high-speed down-flow mode cause a highly turbolized film contact zone of the phases and a gas-liquid mixture of a certain concentration (droplet contact zone of the phases) with intense renewal of the gas contact surface and fluid. This ensures a high intensity of the processes conducted in the apparatus and a high throughput in phases.

After leaving the pipe, the gas and the liquid enter the collection separator 8. The gas is removed from the latter through pipe 18, changing its direction through 180 °. Due to inertial forces, liquid droplets are deposited in the lower part of the collector-separator 8, the liquid phase is withdrawn from the apparatus through the nozzle 20. To remove process heat, the coolant is introduced into the annular space of the apparatus through the nozzle 21, which is removed through the nozzle 22. In the case of contact in the tubes of the apparatus gas with a liquid, the viscosity of which greatly exceeds the viscosity of water in the annular space (for example, sulfuric acid), the organization in pipes of a high-speed descending gas flow and liquid film (W 10-30 m / s) is essential but it intensifies (1.5-2.5 times) the process of removing the heat of reaction as compared with the case of a simple gravitational flow of the film. This makes it possible to have an apparatus with a lower heat exchange surface, and consequently, with a lower metal consumption.

In the proposed apparatus, the liquid phase is introduced into the pipes in two ways: evenly in the form of a liquid film through the supply channels 16 of the distributors 7 under the action of the pressure of the hydrostatic liquid column on the tube plate and less evenly (due to the initial irregularity of the grid irrigation tube grid) in the form of gas-liquid mixture through The upper section of the distributor 7 is approximately equal to the internal section of the pipe.

Since it is advisable to use the tube of commercially available standard one-way tube-tube heat exchangers in the proposed apparatus as a heat exchanger, it is easy to calculate the fraction of fluid supplied to the pipes unevenly in the RF (%). This fraction of fluid is approximately equal to the ratio of the cross section of the ruble space frp to the cross section of the apparatus with respect to the internal diameter D:

RF || 5Е..100.

In this case, the proportion of fluid supplied

in pipes evenly in the form of a film,

J

P „: 100-RF,

Using the data of one-pass shell-and-tube heat exchangers of the type of TN and ТК, 10, calculate the values of RF and Р „for tubes of various sizes (tab. I).

The ratio of the maximum value of the parameter to the average (over the section) of its value is taken as the coefficient of non-uniformity of the KH distribution over the cross section of the velocity apparatus, irrigation density, and other parameters. With a perfectly uniform irrigation nozzle section of the apparatus.

For the proposed apparatus, the value of the irregularity coefficient of irrigation of pipes is determined by the formula

To KF-RF + K.R. ",

where Kp is the coefficient of irregularity of irrigation of pipes through the slots of the distributors, the value of which can be taken equal. Substituting the numerical values for a heat exchanger with a diameter of 600 mm with pipes 0 with a diameter of 20 mm, K 1.29 are obtained.

This value of the coefficient of non-uniformity is a small value (does not exceed the value of the coefficient of non-uniformity of the distribution of velocities over the cross section of the apparatus in the turbulent mode). A comparison of the resulting non-uniformity with the non-uniformity of irrigation by the nozzle shows that, for the proposed apparatus, the coefficient of non-uniformity is less than 1.55 times.

The operability check of the distributor 7 is carried out on an experimental stand for studying heat transfer and hydrodynamics with a downward flow of gas (air) and a film of liquid. The main element of the stand is a copper pipe with an internal diameter of 21 mm and a height of 1856 mm. The liquid distributor is inserted into the upper part of the pipe, above the upper end of which it projects 30 mm. The width of the vertical feed channels is 2 mm. The upper part of the pipe with the Q-distributor is placed inside the distribution chamber with a diameter of 125 mm, air and water are supplied to the distributor. The distributor forms a film of liquid on the wall of the pipe, and the gas passes over its surface through the pipe from top to bottom and is withdrawn from the wall. Air flow is measured with a rotameter type RM-25 GUZ and a dual diaphragm. The flow rate of the fluid is with a PM-0.4 ZUZ rotameter. The air velocity in the pipe W varies from

About up to 33 m / s, and the density of irrigation is from 3-10 to 17-10 MVc.

The bench is equipped with instruments for determining the average heat transfer coefficient a and measuring the differential pressure DP / 1. Heat is supplied to the flowing film of distilled water using the constant heat flux method - electrical heating.

According to experiments, a good quality of the distribution of the liquid over the inner surface of the pipe is obtained, which is confirmed by high values of the heat transfer coefficient both in the case of gravitational film flow () and in the descending direction of the phases. In tab. 2 shows the results of experiments performed at two irrigation densities.

From the above data it can be seen that with increasing speed W up to 7-8 m / s, a slight increase in the resistance of the irrigated pipe is observed. In this case, the heat transfer coefficient is almost equal to the heat transfer coefficient at W 0. In the region of strong gas effect on the liquid film m / s, a noticeable increase in the pipe resistance is observed and an increase in the heat transfer intensity is observed.

Experiments performed on the stand with a traditional slit-type liquid dispenser give similar results. Since the intensity of heat transfer is largely determined by the uniformity of the fluid distributor, high values of heat transfer coefficients a confirm the good performance of the distributor.

The proposed apparatus provides compared with the known. an increase in operating efficiency, which is achieved by a more uniform distribution of gas and liquid through the pipes of the apparatus. Their uniformP,% 20

25

P „,% 20

25

My distribution allows all tubes of the apparatus to operate in the mode of equally high intensity and efficiency of the process, excluding gas overshoot over the cross section of dry tubes. In addition, the improvement of the technological design of the heat-mass-exchange apparatus, which is achieved by using the tubing of commercially available standard shell-and-tube heat exchangers and installing inexpensive and simple to manufacture distributors made of sheet material in the upper part of the pipes.

Claims (2)

1. A heat exchange apparatus, including a vertical casing, fixed in pipe grids, means for supplying fluid to them, characterized in that, in order to increase the work efficiency due to the distribution of the liquid phase in two streams and the improvement of the technological design, it is equipped with distributors tightly inserted into the upper part of the pipes, made in the form of two elements of the arc profile, a cylindrical space between which is divided by a partition of a linear or curvilinear section, the vertical edges of which are connected to two diametrically located edges of the elements of the arc profile, while the other two of their free edges are at the top the ends of the pipes are made with cuts and the areas located above them are bent outwards in the form of stop-guards visors forming feed channels with the outer surface of the arc profile. 2. An apparatus according to claim 1, characterized in that the upper part of the distributors protruding above the pipes is perforated. Table 1 30.5 34.5 69.5 65.5 FIG. g table 2 Fig.Z Fiel 25 .five 3oeomoSf a