RU2045322C1 - Column for acid concentration and denitration - Google Patents

Abstract

FIELD: heat- and mass-transfer apparatuses for gas-liquid system. SUBSTANCE: column for acid concentration and denitration has contact steps installed one above another in column body, cover with outlet of vapor-gas mixture, bottom plate in which sleeve is installed in a spaced relation to it. Circular partition between sleeve and bottom plate body separates its volume into upper and lower zones. Sleeve has tangential inlet for introduction of vapor-gas mixture and installed in lower zone. Outlet for discharge of used acid is installed in upper zone of bottom volume above partition. Besides, outlet for discharge of used acid from the first contact step above bottom plate is communicated with lower zone of volume. This makes it possible to conduct the process of reaction with high rate of renewal of contact surface fully precluding breakthrough of treated acid without contacting and providing full distillation at high efficiency. EFFECT: higher efficiency. 2 cl, 2 dwg

Description

 The invention relates to heat and mass transfer apparatus for systems: gas (steam) liquid and can be used in the chemical industry mainly for the concentration of diluted nitric acid and denitration of spent sulfuric acid.

 A known sulfuric acid denitrator having a bottom with an outlet for spent acid and a nozzle for supplying hot steam to the bottom, in which a chute is installed in front of the outlet for spent acid. The disadvantages of this denitrator are the low steam throughput, limited by the entrainment of the liquid with the vapor under the bubble mode, and the low efficiency of the stripping of nitric acid and nitrogen oxides from sulfuric acid due to the breakthrough of the vapor outside the zone of contact with the liquid phase.

 Also known is a column for denitration and concentration of acids, including a housing with contact steps, a cover with a steam-gas mixture outlet pipe, a bottom with a steam inlet device made in the form of a support cup equipped with concentric rings with slots for steam passage having different heights increasing from peripherals to the center. The column is equipped with nozzles for entering the liquid phase and vapor phase located in the bottom tank. The waste acid outlet pipe is located in the lower part of the bottom tank inside the support cup.

 A disadvantage of the known columns is unstable operation when changing the load of the vapor-gas stream, especially when increasing it, when there is a large entrainment of the liquid with the vapor-gas stream, as well as the leakage of liquid without contact with steam. The known column does not provide complete distillation of nitric acid and nitrogen oxides from the treated acid due to insufficient time for the decomposition reaction of nitrosylsulfuric acid, as well as a small contact surface of the phases. The objective of the invention is the creation of a column of denitration and concentration of acids with high productivity, stable operation with increasing phase loads and ensuring the complete distillation of nitric acid and nitrogen oxides from the treated acid.

 The task is ensured by a column of denitration and concentration of acids, including a housing with contact steps, a cover with a steam-gas mixture outlet pipe, a bottom with a steam inlet device made in the form of a glass installed in the bottom tank with a gap to it, liquid and gas-vapor phase inlets and withdrawal of spent acid from the bottom tank. In the column according to the invention, the glass is equipped with an annular partition dividing the bottom capacity into the upper and lower zones, as well as a nozzle for introducing the vapor-gas phase into the glass, which is installed tangentially in the lower zone, a waste acid outlet pipe is installed in the upper zone of the bottom above the partition. In addition, it is advisable that the exhaust acid outlet pipe from the first contact gas stage along the vapor-gas phase is in communication with the bottom zone of the bottom tank. This allows the interaction of the contacting phases and their separation in a swirling flow. The acid to be processed passes through the gap between the glass and the bottom, is picked up by a swirling flow, their interaction is intense, a significant area of the phase contact surface develops, the renewal rate of which is high. The interaction of the phases is carried out both in the droplet and in the film modes. The presence of liquid in the lower part of the glass and the nature of its interaction with the vapor-gas phase completely excludes the breakdown of the treated acid outside the contact zone of the phases. The organization of interaction and separation of the contacting phases in a centrifugal field makes it possible to intensify the mass transfer process, predetermining the stable operation of the column with increasing phase loads and ensuring the complete distillation of nitric acid and nitrogen oxides from the treated acid, and provides an increase in the productivity of the column.

 The advantages of the proposed columns increase with the organization of the return of spent acid from the steps of the column to the bottom tank.

 In FIG. 1 is a longitudinal section through a column; in FIG. 2 cross section AA in FIG. 1.

 The column consists of a housing 1 with a set of contact steps 2, a cover 3 with a nozzle for the outlet of the vapor-gas mixture, a bottom 4 with a glass 5 installed in it, located with a gap 6 to the bottom 4. The glass 5 is equipped with an annular partition 7 dividing the capacity of the bottom 4 into the upper 8 and the bottom 9 zone. A nozzle 10 is installed tangentially to its surface in the nozzle 5 for supplying the vapor-gas mixture inside the nozzle 5. A nozzle 11 is installed for removing the spent acid from the column. For nozzles of the acid to be treated, nozzles 12, 13 are provided for supplying the vapor-gas phase, nozzle 14. To improve droplet separation in the upper a droplet separator 15 can be installed in zone 8 of the bottom container 4. The column is equipped with a nozzle 16 for discharging spent acid with the first contact stage 2 above the bottom tank 4.

 The column works as follows. The acid to be treated, for example, sulfuric acid, is supplied to the lower zone 9 through the nozzle 13. It is advisable to connect the nozzles 13 and 16 with an external water seal, which allows maximum use of the bottom volume to intensify the process of distillation of nitric acid vapor and nitrogen oxides. Acute water vapor is introduced into the lower zone 9 of the bottom 4 through the nozzle 14. The acid fills the lower part of the zone 9 above the level of the gap 6, thereby forming a water seal and eliminating steam leakage when the column is working through the gap 6. The volume of acid in the lower zone 9 provides the time required for the decomposition of nitrosylsulfuric acid. The steam passes through the tangential nozzle 10, acquires a rotational movement and thus unwinds the liquid entering the nozzle 5 through the gap 6. In the area of the interface between the nozzle body 5 and the tangential nozzle 10, the steam interacts intensively with the liquid. Steam splits the liquid into droplets that move along intersecting paths, collide, merge and crush again. A significant area of the contact surface of the phases develops, the refresh rate of which is high. The part of the glass 5 lying above the tangential pipe 10 serves to separate the liquid from the swirling vapor-liquid flow. Drops of liquid under the action of centrifugal forces are discarded to the inner surface of the glass 5, hit it and turn into a film. The rotating film of liquid breaks off from the upper end of the cup 5, is discarded to the walls of the upper zone 8 body, flows to the partition 7 and is discharged from the column through the nozzle 11. The gas-vapor phase is directed to the overlying contact stage 2. For better separation of droplets from the gas-vapor flow, it can be installed above the upper the end of the glass with a gap to it droplet separator 16.

 At each stage 2, the process of mass transfer continues. All acid entering the lower zone 9 is in contact with the steam and is discharged from the column in the upper zone 8. Due to this, an increase in the completeness of the distillation of nitric acid and nitrogen oxides from the treated acid is achieved. Such an organization of the interaction of phases in a centrifugal field can improve the performance of the column. In addition, when connecting the exhaust acid outlet pipe 16 through a water trap to the pipe 13, the spent acid is returned from the contact stage 2 to the working area at the entrance to the glass 5 for further processing. This allows you to achieve a higher degree of distillation of residues of nitric acid and nitrogen oxides and thereby achieve a higher concentration of production sulfuric acid.

Claims (2)

 1. A COLUMN OF ACID CONCENTRATION AND DENITRATION, including a housing with contact steps, a cover with a steam-gas mixture outlet pipe, a bottom with a steam inlet device made in the form of a glass installed in the bottom tank with a gap to it, liquid and gas-vapor phase inlet and outlet pipes waste acid from the bottom of the tank, characterized in that the glass is equipped with an annular partition dividing the bottom of the tank into the upper and lower zones, a gas-vapor phase inlet pipe installed tangentially in the glass in the lower zone, and the pipe withdrawal of spent acid is installed in the upper region of the bottom of the container wall.  2. The column according to claim 1, characterized in that the outlet pipe of the spent acid from the first above the bottom of the contact stage is communicated from the lower tank of the bottom.