SU763265A1 - Method of ammonia recovery from blasting gases of ammonia synthesis - Google Patents

Description

one

The invention relates to methods for separating ammonia from gas mixtures, in particular from ammonia synthesis purge gases, and can be used in the chemical industry.

There is a method for separating ammonia from a gas mixture by absorption of ammonia with aqueous solutions.

The disadvantage of this method is the low degree of ammonia recovery. 10 The residual ammonia content in the purified gas mixture is 0.61, 0 vol. %

The closest to the invention in technical essence and the achieved 5 result is the method of ammonia extraction from the purge gases of ammonia synthesis by absorption of it with water to produce ammonia water.

The purge gases enter adsorption at a temperature of 25-35 s. In this case, the dissolution of ammonia in water is accompanied by the release of a large amount of honest heat that must be removed to increase the driving force 25 of absorption. The absorption process is carried out at 40-60 0. Heat absorption is removed by cooling the absorbent with water through a wall in remote or built-in heat exchangers. .thirty

The known method has the following disadvantages.

The low degree of ammonia recovery {residual ammonia content in the purified gas is 0.5-1.0 vol.%) From ammonia synthesis gas produced in ammonia leads to an increased content of nitrogen oxides in the flue gases of the tube furnace, which in the existing ammonia production is emitted into the atmosphere pollution environment.

The presence of heat exchangers for the removal of heat absorption significantly complicates the design of the absorber. The use of other refrigerants is not economically feasible, since in this case the technological scheme is significantly complicated and capital and energy costs increase.

The aim of the invention is to increase the recovery of ammonia from the purge gases of ammonia synthesis and to simplify the process.

Claims (2)

The goal is achieved by the proposed method of extracting ammonia from the purge gases by absorption, which consists in that the purge gases before absorption are pre-cooled to (+5) - (- 5) ° C. In this case, preliminary cooling of the purge gases of ammonia synthesis is carried out in a vortex tube. The invention differs from the known technical solution in that the heat of absorption is removed directly by the source gas, which is cooled by 10-40 ° C below the temperature of the absorbent. This allows the heat absorption to be completely removed in direct contact of gas and liquid and to reduce the temperature of the absorbent. It is not the absorbent itself that cools, but the gas entering the absorber, which in turn cools the absorbent in direct contact. As a cold generator, a vortex tube is used in which the energy of the purge gas pressure is utilized. In the vortex tube, the gas is cooled due to the vortex effect (the Ranka – Hils effect), which consists in separating the swirling gas flow into. two streams - cold and hot. The ammonia recovery unit consists of a vortex tube, a water cooler and an absorber. Example. 23000 purge gases, content (%) 3 NHg-, 10 CH4; 3 Ar; 21 N3; 63 Hj, under pressure of 200 atm, with temperature + enters the vortex tube where it expands to 11 atm and is divided into two streams: cold (with temperature) and hot (with a temperature of 95-100 s). The hot stream (30% of the total flow rate) is cooled in a water cooler to + 40 ° C and then mixed with the cold stream. Gas mixture with a temperature of - 5 ° C enters sorbent. In the absorber, ammonia is absorbed by water through the production of ammonia water containing 19% ammonia. At this heat, absorption is removed by the cooled source gas in direct contact with ammonia water. The purge gases after the absorber, containing 0.009 vol.% Of ammonia, are fed for combustion in a tube furnace for steam reforming of methane. EXAMPLE 2 23000 purge gases containing (% 2 11 СН; 3 Ar; 21 Мд; 63 N. A pressure of 200 atm with temperature enters the vortex tube, where it expands to 11 atm and is divided into two streams, cold and hot. The hot stream (301 of the total flow rate, with a temperature of 125-135 C) enters water cooler, where it is cooled to + 40C. - A cold stream with a temperature of -10 ° C is mixed with a hot stream coming out of the refrigerator, and the gas mixture with a temperature of + 5 ° C enters the absorber.In the absorber, the ammonia is absorbed by water to produce ammonia water containing 15% ammonia.The purified gas mixture with a residual ammonia content of 0.018% vol. Calculations showed that the use of a vortex tube in the present invention is economically feasible. The implementation of the proposed method in the production of ammonia with a capacity of 2,720 tons per day will reduce the content of nitrogen oxides in tubular flue gases echi which are ejected into the atmosphere and, therefore, reduce environmental pollution. Claim 1. In order to increase the ammonia from the purge gases of ammonia synthesis by its absorption by water, characterized in that, in order to increase the degree of ammonia recovery and simplify the process, the purge gases prior to absorption are cooled to (+5) - (- 5) sec. 2. A method according to claim 1, characterized in that the pre-cooling of the purge gases is carried out in a vortex tube. Sources of information taken into account in the examination of 1.Patent of Germany 1244746, cl. From 01 C 1/04, 07.20.68. 2. Atroschenko V.I., Alekseev A.M. et al. Course of the technology of bound nitrogen. M., Himi, 1968. p. 247.