RU66224U1 - Absorption Column - Google Patents

Abstract

A column for the absorption of formaldehyde-containing gases is proposed, which includes an all-welded casing with liquid phase flow distribution devices and nozzle sections, as well as a drop eliminator, the nozzle sections being separated by chambers with level gauges and a plate part. The technical result achieved is an increase in the efficiency of chemisorption of formaldehyde and a decrease in the concentration of pollutants in the gas used for catalytic treatment.

Description

The proposed technical device relates to absorption columns used for the sorption of formaldehyde-containing gases obtained by oxidative dehydrogenation of methanol on silver or metal oxide catalysts using shelf or tubular contact devices.

The known design of a packed absorption column [Ponomarev II, Perelygin OA, Doronin VN, Gaynullin MG .. Machines and apparatus for chemical production, / Ed. Engineering. 1989, S. 95]. It contains an all-welded or assembled from separate tsar case 1, inside of which there are two plates 2 and 5 for distributing the fluid flow and several support grids 4 with nozzle layers 3, as well as a drop eliminator 6 in the upper part of the apparatus (Figure 1).

Packed columns of this type are very sensitive to irregularity of irrigation, which is not always achieved with devices 2 and 5. In addition, their significant drawback is the difficulty in achieving high efficiency due to the complexity of the distribution of liquid and gas phases over the cross section of the column.

The objective of the utility model is to improve the design of the absorption column while increasing its efficiency during operation.

The task is achieved in that the main structural elements of the proposed mass transfer apparatus are all-welded housing 1, switchgear 2 and several support grids 4 with layers of nozzle 3 and a drop eliminator 6, and between the nozzle sections of the column there are two chambers for level gauges 7 and 9, separated by a dish-shaped zone 8.

The essence of the proposed utility model is a column for the absorption of formaldehyde-containing gases, including all-welded body

with the liquid phase flow distribution devices installed in it, a droplet eliminator and at least three packed sections, moreover, the column has a dish-shaped part with 2-15 plates, and the packed sections are separated by chambers with level gauges.

Example.

Figure 2 shows a General view of the improved design of the absorption column, designed to produce 25 thousand tons / year of urea-formaldehyde concentrate grade KFK-85.

It represents a steel heat-insulated apparatus with a diameter of 2600 mm and a height of 36740 mm. Inside it are three plates designed to distribute the flows of the liquid phase entering the packed sections. As a nozzle, Pall stainless steel rings are used, poured in several layers onto grilles welded to the body. Between the packed sections are cameras with level gauges designed to maintain the required level of the liquid phase along the height of the mass transfer apparatus.

The column has a dish-shaped zone, consisting of twelve plates on which a urea solution with a concentration of 50-64% by weight is supplied. and a 6-10% aqueous solution of an alkaline agent.

Maintaining the required temperature of the liquid phase in the packed sections is achieved by circulating the liquid phase through the plate heat exchangers 10 using pumps 11 (Figure 2).

In the upper part of the absorption column, a droplet-breaking device is installed, which reduces the droplet drop with gas exiting the apparatus.

The inventive utility model works as follows.

Formaldehyde-containing gas with a temperature of 182 ° C obtained in a methanol oxidative dehydrogenation reactor and having a composition,% vol.,

methanol 0,065 dimethyl ether 0,110

With 1,000

CO _{2 \ tab} 0,101

formaldehyde 7,864 H ₂ O 8,400 oxygen 7,316 nitrogen 75,140 formic acid 0.004

continuously fed into the cube of the absorption column in an amount of 419 kg / h calculated on formaldehyde, and in the dish-shaped part - 264 kg / h. 60% aqueous urea solution with a temperature of 58-60 ° C. Due to the circulation of the liquid phase through the plate heat exchangers, the temperature in the packed sections is maintained in the following intervals:

Section temperature, ° С lower 67-70 average 54-56 top 22-35

At the same time, an 8% sodium hydroxide solution in quantities of 4.6, 9.4 and 8.2 kg / h, respectively, is metered into the cube, lower nozzle section and the dish-shaped zone of the column. The supply of aqueous solutions of urea and alkali is regulated in such a way that the molar ratio and pH in the bottom part, the lower and middle packed sections of the column are maintained at the level of technological requirements.

The proposed utility model differs from the known ones in that it combines the advantages of nozzle and plate mass transfer devices, that is, it is combined.

This makes the design more reliable in management and operation. In contrast to the known model, the implementation of the proposed technical solution will increase the efficiency of formaldehyde chemisorption and reduce the concentration of pollutants in the gas sent to catalytic treatment by 3 times.

Claims (1)

Absorption column of formaldehyde-containing gases, including an all-welded casing with liquid phase distribution devices installed in it, a drop eliminator and at least three packed sections, characterized in that the column has a plate part with 2-15 plates, and the packed sections are separated by chambers with level gauges.