SU128452A1 - Method of producing liquid nitrogen oxides - Google Patents

Description

It is known to produce liquid nitrogen oxides from nitric oxide, synthesized during an arc process on an oxygen-enriched mixture of nitrogen and oxygen, followed by the catalytic oxidation of nitric oxide to dioxide and separating the obtained nitrogen dioxide by selective adsorption by silica gel in the fluidized bed and subsequent desorption in nitrogenized or moving layer. The process is conducted in a closed cycle with gas recirculation and nitrogen dioxide is condensed under pressure.

However, this method is complicated by the separation of water vapor from gases intended for the synthesis of nitric oxide, and with the need to use low temperatures (-50) in the oxidation of nitric oxide.

The described method does not have these disadvantages. Its distinctive features are the use for the synthesis of nitric oxide and the pre-dried mixture of gases, as well as the process of catalytic oxidation of nitric oxide to dioxide in two stages at temperatures of 30-35 ° and -10 ° (instead of -50 °), which reduces energy costs for cooling.

Technological scheme of the process is shown in the drawing.

According to the invention, firstly, dry, pre-enriched air (up to a content of 60-65% by volume of 02%) is introduced with a gas blower / into a closed circulating gas system. Next, the gas mixture passes through the surface heat exchanger 2, where it is heated by the heat of the gases leaving the furnaces to 150-180 °.

The heated gases pass through the switching device 5 and enter one of the heat exchangers, the regenerators 4, with a highly resistant nozzle, where they are heated to a high temperature (1900-2050) for

J 128452

expense of heat previously accumulated by the regenerator nozzle. From the first regenerator, the hot gases enter the high-temperature electrolytic furnace 5, where in the flame of a volt arc, they are heated to the final temperature (2300-2150 °), at which reaction N0 takes place. The average temperature in the furnace per cycle is 2225 °. Of these, nitrous gases containing about 2.6% (volume) N0 pass through the second heat exchanger - regenerator 4, where they transfer their heat to the nozzle layer, cooled to 250-300 °, then the gases pass through the switching device 3 and heat exchanger 2 where their temperature is further reduced to 160-180 ° by heat exchange with the circulating gas going to the switching device.

The gases are then passed through a water cooler 6, where their temperature drops to 30-35 °, and a filter 7 for separating 1-1 solid packing particles entrained in the flow of gas from the regenerators.

The cleaned gas with a circulation gas blower 8 is driven through a water spray 1 cooler, where it is again cooled to 30 °.

Next, the gas enters the catalitic oxidation carried out in two successively installed reactors 10 and 11 with a fluidized bed of silica gel.

In the reactor 10, where the oxidation of NO in NO2 undergoes 70–75% pa, the cooling of the bed is carried out with a mixture of water; in the reactor //, where the degree of oxidation is brought to 95-98%, the process proceeds at a temperature of -10 ° and cooling is carried out with brine. in countercurrent with the flow of solid sorbent (silica gel), which is on the shelves in a fluidized state.

In the process of countercurrent adsorption, the content of NOg in the gas decreases from 2.6 to 0.05-0.03% by volume, and the temperature of the gas due to heat exchange with silica gel and the heat of adsorption increases to 60 °. Silica gel, saturated with nitrogen oxides with a temperature of about -5, from the bottom of the adsorption column 12 is continuously flowing into the upper part of the desorption multistage shelf column 13.

A purge gas with a temperature of about 50-60 ° C is fed to the bottom of the stripper to keep the silica gel on the shelves in a fluidized state.

The desorption process proceeds with a gradual increase in the silica gel temperature (from top to bottom) from -5 ° to 4-180 due to heating it with deaf steam with a coil of coils located on the shelves of the desorber 13.

A mixture of purge gas and nitrogen dioxide evolved from silica gel, containing about 50% NO2, is passed through filter 14 to compressor 15.

The silica gel heated to 180 ° C, after removing nitrogen oxides from the bottom of the desorption column 13, is continuously fed to the upper part of the adsorption column 12 by means of pneumatic conveying.

Thus, the scheme provides for the circulation of silica gel in a closed cycle to which fresh silica gel is periodically added to compensate for losses due to partial loss of solid particles by the gas flow.

Concentrated nitrous gases containing about 50% volume NO2, after compression in the compressor 15 to 7-12 atm, are successively passed through a water cooler - condenser 16, in which when they are cooled to a temperature of 30 °, partial condensation occurs.