CS209337B1 - Rehabilitation of nitrous gases from exhalations - Google Patents

Abstract

The invention solves the problem of removing nitrous gases from exhalations by their reaction with aqueous solutions of ammonium salts of lower aliphatic carboxylic acids with carbon numbers from to C-j in countercurrent gas scrubbers. The reaction of both components takes place at normal pressure and temperature. The invention is applicable to the capture of nitrous gases from exhalations in the chemical industry, laboratories and research sites in air protection.

Description

(54) Method of removing nitrous gases from fumes

The invention provides for the removal of nitrous gases from the exhalates by their reaction and aqueous solutions of ammonium salts of lower aliphatic carboxylic acids with carbon numbers from C to C in countercurrent gas scrubbers. The reaction of both components takes place at normal pressure and temperature.

The invention is applicable to the capture of nitrous gases from fumes in the chemical industry, laboratories and research facilities for air protection.

209 337

The present invention relates to a process for the removal of nitrous gases from fumes by converting them to inert substances by reaction and ammonium salts of lower aliphatic acids in an energy-efficient configuration.

By eliminating the emission of nitrogen oxides (NO *) from the exhalates produced e.g. in metal pickling, nitration processes, explosives production, in the manufacture of dyeing products and intermediates is limited worldwide, their quantity is small, but their hygienic and ecological defects around manufacturing plants are indisputable.

The new plants solve the problem of ΝΟ _χ fumes by energy-intensive processes, especially by absorption at elevated pressure with a result of about 500 - 800 gm in the off-gas. Older medium pressure systems have a 1500 - 3000 gm “· ³ ΝΟ _χ . Moreover, the systems use different absorbing media, with an average efficiency of about 50-60 vol. %, mainly due to low concentrations of Μ0 _χ and their discontinuous effluents. Other problems arise when dealing with the use of absorbent solutions.

Recent techniques in the field of the use of absorbent solutions containing mainly nitrite and sodium nitrate have been working to convert nitrites to nitrogen, with the remaining sodium nitrate contemplated to be used as a liquid fertilizer component. However, the solution is unacceptable from an agricultural point of view because of its high sodium content.

Attempts to apply catalytic oxidation to remove Ν0 _χ from flue gases lead to more demanding investment facilities. The processes require larger auxiliary fuel volumes, high operating temperatures, and high platinum catalyst costs.

A selective reduction of Ν0 _χ using ammonia is also described. Under suitable reaction conditions and in the presence of a suitable catalyst, ammonia is preferably reacted with nitrogen oxides according to the following equations:

NO + 4 NH ₃ → 5 N ₂ + 6 HgO

NO / + 8 NHy → 7 N ₂ + 12 HgO

Under conditions applicable to a selective reduction, i.e. a temperature of 200-300 ° C, and at 10-30 '(v / v) excess ammonia, the Ν0 _χ removal effect is more than 80% (v / v). It is not necessary to use a platinum catalyst in this reduction - a more vain catalyst from vanadium oxide is sufficient. The process described is energy intensive.

Disadvantages of the above-mentioned state are eliminated by the process according to the invention, which is based on the fact that nitrogen oxides are scrubbed in counterflow gas scrubbers 5-95% by weight. aqueous ammonium salts of aliphatic carboxylic acids having a carbon content of from C 1 to O 2. The whole conversion process Ν0 _χ takes place at normal temperatures of the exhalates themselves, atmospheric pressure in a classical spraying device. The sprinkler itself - gas scrubber - can be of the most varied design.

In the present invention, the lower aliphatic acid released by the reaction is recirculated through a conventional pump. The pumped circuit includes a degree of saturation of the liberated aliphatic acids with a gaseous or aqueous ammonia solution to form the corresponding ammonium salts of the aliphatic acids. The regeneration of the absorbent solution takes place at normal temperature and pressure.

Ammonia saturation control is provided by the automatic pH control associated with the dispenser. Lower aliphatic acid solutions have a pH of about 2 and their salts have a pH of about 4-6. The reaction water released causes dilution of the solution, the concentration of which must be monitored and adjusted with pure acid or directly with an ammonium salt of aliphatic acids.

Example 1

Exhalates with Ν0 _χ are fed at the bottom of the column packed with Raschig rings. The column is sparged with 40% v / v. ammonium acetate solution. The scrubbing solution is pumped to the second column, where ammonia gas is fed countercurrently. The recovered solution is recycled, the degree of saturation aa being controlled by pH. The scrubbing efficiency of n0 _χ from the exhalates is 92% by weight.

Example 2

Exhales containing Ν0 _χ are scrubbed with 70% vol. ammonium formate solution. Regeneration of the used solution is ensured by suction of ammonia gas through the ejector into the pipeline. The removal efficiency Ν0 _χ is 97% by weight.

The advantages of the proposed solution according to the invention are that the whole process is investment, operational and energy efficient. Due to a suitable design, it can be retrofitted to various sources of nitrogen oxide emissions. It can be used for dilute and concentrated sources, for sources with continuous or discontinuous discharge, since the reaction pe is immediate and does not require any special temperature or pressure conditions.

Claims (2)

aliphatic acids. The recovery solution is recovered under normal temperature and pressure. The addition of ammonia is controlled by means of an automatic pH control coupled with the respective dispenser. Lower aliphatic acid solutions have a pH of about 2 and a pH of about 4-6. The water released by the reaction causes dilution of the solution, the concentration of which needs to be monitored and adjusted? pure acid or directly ammonium salt of aliphatic acids. Example 1 Exhalants with χOχ are fed at the bottom of a column filled with Raschig rings. The column was shaken with 40% ammonium acetate solution. The scrubbing solution is pumped into a second column where gaseous ammonia is fed in countercurrently. The recovered solution is recycled while the degree of saturation is controlled by pH. The ejection efficiency of χ0χ from the exhalates is 92% by weight. Example 2 Exhalates containing χ0χ are sprayed with 70% by volume ammonium formate in a packed column at ambient temperature. Regeneration of the spent solution is ensured by sucking gaseous ammonia through the ejector into the duct. The removal efficiency of χ0χ is 97% by weight. The advantages of the proposed solution according to the invention are that the whole process is investment, operational and energy-saving. On the basis of a suitable dimensioning, nitrogen oxides can be additionally fitted to different emission sources. It can be used on dilute and concentrated sources, on sources with continuous or discontinuous feed, since the reaction is instantaneous and requires no special temperature or pressure conditions. DISCLOSURE OF THE INVENTION It is desirable to remove the nitrous gases from the exhalations by passing them through a countercurrent gas scrubber, characterized in that the gases are scrubbed with a 5 to 95 vol.