SU1157014A1 - Method of obtaining nitric acid - Google Patents

Abstract

A method for producing nitric acid, which involves the oxidation of ammonia followed by multi-stage absorption of the obtained nitrogen oxides with water in a plate column under pressure, characterized in that, in order to increase the degree of absorption of nitrogen oxides, absorption is carried out in two stages: in the first stage, the content of nitrogen oxides in gas phases (in 0.11-0.20 vol.%, in the second stage - in a fluidized bed of silica gel at a mass ratio of T: W on the plate, equals 4

Description

Sl vi The invention relates to chemical technology, and more specifically to the problem of intensifying the processing of nitrogen oxides to nitric acid. The aim of the invention is to increase the degree of absorption of nitrogen oxides. Example 1. (known). Absorption of N0 is carried out on 47 sieve plates (hole diameter 2 mm, free section 5%). 4600 kg / h of water are supplied for irrigation. Changes in the concentration of nitric acid and the composition of the gas in the plates are shown in the table. The amount of the product obtained is 14.9 tons of HNO monohydrate, at 1 h. 37 plates have a free cross section of 5%, and the remaining ten plates e (, mm and free cross section of 8%. On the last 10 plates loaded silica gel of 20 kg, which provides the catalyst and liquid phase 0.1: t. The overflows of these plates are protected by a stainless steel mesh to prevent the transfer of silica gel from plate to plate.The absorber is irrigated with water in an amount of А715 kg. The change in nitric acid concentration and gas composition is given below

. Example 2. Absorption of N0 is carried out on 47 sieve tar trees. And

15035 t of monohydrate HNO per 1 h. Examples 3-10 are given below.

The process of obtaining nitric acid 35 is carried out in embodiments under a pressure of 730 kPa. After contact oxidation of ammonia, separation of the acidic condensate by cooling the gas and oxidizing nitrogen oxides with oxygen of the air, the nitrous gas is absorbed. The concentration of nitric acid produced is 58%. The processing of nitrogen oxides is carried out in an absorber with a diameter of 3.2 mm on 47 mesh S plates. The gas velocity in the absorber is 0.26 m / s.

Under normal conditions for the processing of nitrogen oxides to nitric acid. At a low content of nitrogen oxides in a gas, the limiting stage is the oxidation of nitrogen oxide with oxygen. In this case, the bulk of the nitric oxide is oxidized in the gas phase to 95% and the remaining amount is oxidized in the liquid 55 phase and at the interface. i The use of a fluidized sipicagel in a three-phase layer (liquid-solid gas) makes it possible to sharply intensify the oxidation of oxide and nitrogen by increasing the proportion of oxidation processes in the liquid phase and at the interface (gas-solid, liquid-bone-solid) . Silica gel is able to concentrate oxides of nitrogen, nitrous acid and oxygen on its surface and, according to the law of mass action, thus increases the rate of chemical reactions.

The most effective use of silica gel is in the range of N0 concentration in the gas in the range of 0.11-0.2% by volume, which, in accordance with the change in the gas composition along the height of the column, determines the choice of catalyst loading zone on 1-10 absorber plates, calculated from above.

The effectiveness of the proposed method depending on the concentration of NC can be traced from the data below.

9115701A6

The experiments were carried out on the same helix. As the catalyst used

a high-pressure bubbling unit at 20 ° С, lump silica gel of a low-velocity gas velocity of 0.3 m / s, crusty (mm) - KSM, and large-scale pressure of oxygen-containing silica gel, large-pore

20 kPa, irrigation density 0.5 m .5 (mm) - BSC.

 . . ...,

Concentration of NOj.B gas, vol.% Absorption rate,%

The catalyst silica gel KSM40 A9 48 26

Silica gel catalyst 45 40 20

Lack of catalyst24 20 18 16

When the catalyst ratios are 0.5: 1, the process faucets have practically no effect on the liquid phase on the plate.

0.1: 1 silica gel does not provide}

lasting positive effect, and "j" Effect of silica gel ratio

Namely: there is an oscillation according to the ef-mark KSM and the liquid phase on the plate

absorption efficiency of oxides azo can be followed at a constant

ta, and an increase in the NOy concentration ratio of 0.15% by volume.

Mass ratio

silica gel and liquid in the absence of QQ. Q. 0.3: 1 0.5: 1 0.6: 1

catalyst

The degree of absorption,% 23 27 40 51 55 56 Under the considered conditions for the absorption of nitrogen oxides, the solubility of silica gel in acid does not exceed 40 0.002 wt.%, Which is much lower

0.11 0.15 0.2 0.25 OST requirements imposed on. weak nitric acid content of the solid residue in the product.

Claims (1)

METHOD FOR PRODUCING NITRIC ACID, including the oxidation of ammonia followed by multi-stage absorption of the obtained nitrogen oxides with water in a dish column under pressure, characterized in that, in order to increase the degree of absorption of nitrogen oxides, the absorption is carried out in two stages: at the first stage, to the content of nitrogen oxides in the gas phase of 0.11- * 0.20 vol. X, in the second stage in a fluidized bed of silica gel with a mass ratio of T: W on a plate equal to (0.1-0.5): 1. 1 157014