CS201561B1 - Nitrous emissions disproportionation method - Google Patents

Description

The present invention relates to dieproporclonation of intrinsic emissions. The most common and at the same time 1 versatile method of removing nitrosheal ealels from industrial exhalation is the absorption process. For this absorption eo use the most pure water or alkali metal or alkaline earth hydroxide solutions, either in a non-pressurized cell or in pressurized equipment. In such cases, the efficiency of the absorption process may be 85 to 90%, depending on the concentration of nitrous gases present, 0 _χ , in particular the reactive duoxide, the absorption solution used and the absorption apparatus; on average, however, especially in industrial conditions, abaorption efficiency never exceeds 30%.

The advantage of the absorption process is always the relative simplicity of the apparatus: the disadvantage, however, is that the investment costs, the relatively low efficiency of the equipment, and usually the need for further disposal of liquid and toxic waste, or its processing into a useful by-product, are always very high.

The most effective methods for disposing of Ν0 _χ are alkaline abaorption in a strongly reducing or strongly oxidizing environment, which can dispose of 1 part of the relatively reactive and relatively insoluble duanium oxide. Both types of oxidation-reducing absorption are often combined in different order. 3 as a reducing agent, and most commonly, sulfur dioxide, hydrogen sulfide, or yoylide compounds; Some of the alkali hypochlorite and corrosive hypochlorite have been used as oxidizing agents

201 561

201 501 soils *, hydrogen peroxide or ozone, solutions of alkaline permanganates, etc. In the ranked cases, 1 anaha was regenerated by absorbing handles, nojčaetijl by electrolytic oesthet, and abeorbant recycled da process. From an efficiency point of view, the absorption process is always designed to eliminate ΝΟ _χ in smaller volumes 1 when the concentration of the non-icing content can reach a maximum: the oxidation tupene ¹ , usually in pars, there are difficulties with nitric acid. Reductions with larger NO levels must always be oxidized to NO *, or catalytic catalytic thermal reduction of noaelectric and hydrocarbons or selective β ammonia, depending on the air flow in the emitter.

However, very low temperatures or excessive pressures can lead to dieproportionation to non-toxic and practically inert nitrous oxide and reactive to dual oxide in nitric oxide:

NO —---- ---------- N ₂ 0 ₂

NO ♦ N ₂ O ₂ ................... ............ »N ₂ 0 + NO ₂

Nitric oxide under the above conditions may obviously lose its free radical character, and the formation of an unstable blmer may cause dieproportionation.

However, due to tharmodynaaic instability, a number of chemical reactions can be used under certain conditions supported by catalysts;

NO

NO

NO

NO

-> 2 N ₂ 0 + 0 ₂ -136, 9 KO - »N ₂ 0 + ₂ N0 -103.0 kO

-> N ₂ + 0 ₂ - 172.9 kO

-> N ₂ + 2N0 ₂ - 242.0 kO

These examples of possible die-reaction reactions have not been successfully applied in practice. This is prevented by the necessity of costly pressure equipment nobo operating demanding cooling devices to very low temperatures, which would in practice be intolerable in particular when processing large volumes of pumice oxides.

The use of any catalyst in the absorption removal of nitric oxide and other patent applications. For example, according to Japanese patent 7834,677, Japanese patent 7517,367 or 7834,679, nitric oxide removes spindle in alkanolamine in the presence of lozenges. In addition, the patent teaches that the active ingredient ingredients have always led to the necessary presence of other reducing components; in particular, sulfates, such as those described in Japanese Patent 74, 122, 878, for example, in an alumina medium from catalysis of cotons by medium, aero nobo cobalt. A similar procedure is carried out according to Japanese patents 7522,773, 7562,860, 7567,785 nobo 7562,892 and the like, in an aqueous ammonia concentration of 15% by weight.

Disadvantages of the above methods, including: Due to the very low temperatures, high pressures, purging of the auxiliary defective handrail and the high investment and operating costs, and resulting in a large number of waste water solutions difficult to use, the process according to the invention is essentially eliminated and advantageously avoided. a nitric oxide, and contacted with a solution at least

201 SOI of one of the heavy metal nitrates, preferably cobalt, nickel, iron, manganese, chromium, copper, zinc, cadmium or lead or / and uranyl or aluminum and / or lanthanum and / or actinide at pH 0 to 0 solutions 6.

The advantages of the invention are its relative unpretentiousness as to the required absorbent device; as well as the necessary abeorbents. The process operates in devices without pressure modification of the most frequent and simple solutions of abaorbents, which remain in the aqueous environment without perceptible change in function for an unlimited time. A further advantage of the invention, particularly I ¹ the circumstance that unlike other zněných practice, the method is selective for hard Duen reactive carbon, although carbon duelčltý it can be disposed. On the other hand, in the case of high duoxide contents, it is necessary to count on the classification of the next higher grade.

Ukázal cobalt nitrate * has been shown to be the most effective β-disproportionate absentbent, but 1 aqueous solutions of nickel, iron, manganese, nitrates, chromium, copper, zinc, cadmium, lead, indanyl, aluminum, uranyl, aluminum, , lanthanum, etc.

In special cases, instead of a simple solution of nitrates, for example 1 aqueous solutions and high radioactivity, which can be dispensed with from the regeneration of spent nuclear fuel, it is possible to incorporate as a disproportionate solution; Their incorporation into the process is best suited in the flow-through device. The solutions almost always contain considerable concentrations of all the necessary active cations in the form of nitrates, in particular iron cations, lanthanides and actlelds.

The reaction principle used may to some extent be an indication of the reaction of reactive nitric oxide with water, the course of which can also be favorably influenced by lowering the temperature or increasing the pressure:

NO ₂ -—- b N ₂ 0 ₄

N, O. -> ^NO 2 ⁺ ♦ ^ 2 ⁴ h ₂ °

The nitric oxide reaction, however, always requires the presence of a catalyst which, after the hypothetical intermediate step has been formed with water and a defect in hydrolysis; the easy catalytic action of NO is probably due to its free-radical character:

NO -_katSÍJ £ SÁÍa £ - / N ₂ 0 ₂ / / NjjOg / -> NO * + NO ”

HgO

Since the resulting components ae are unstable in an acidic environment, it is common to express the above-mentioned reakoe:

NO -> 4 / N ₂ O ₂ / -> 2 N ₂ 0 ♦ 2 N ^ Oj optionally

NO -> 3 (NjgOg) ——> 2 N ₂ 0 + 2 NO ₂

After this procedure is to reduce nitrogen oxide in abaahu nitržznich β mixtures of at least 30-80%, while the remaining reactive fell N0 _2>, or N ₂ 0 ₃ can be removed by other but also taehnleky saving manner. ·

The procedure is illustrated in more detail in the examples which do not allow the application of SOI to be sapped and the method according to the proportions of duanathoea ohaaabaorpol can also be applied in other conditions, especially on an industrial scale for exhalation and radioactive non-radioactivity.

Example 1.

The intermittent emission and both NO 29000 mg / a ³ was accrossed in a cobalt nitrate solution of molar concentration in water at pH 5.5. The flue gas exhibited a residual concentration of 32 _{χ of} 32%, although in the form of reactive NO ₂ (i.e. equivalent to 9300 mg / n ³ NO). The Chamlaorpenl solution worked with unchanged effect and without apparently changing the spacing for a very long time.

Example 2.

In the same manner, with an efficacy of 63%, a completely fresh exhalate was prepared by absorption in a 1/2 molar aqueous solution of nickel dicalate at pH 4.2.

Example 3.

Exhalation of 8 with 12000 mg / n ³ NO was passed through a scrubber and not a 3 molar copper nitrate solution. The temperature of the solution was 23 ° C and the pH of the solution was 3. The exhaled exhalation showed analytically a content of 4150 mg / m ³ (expressed as NO) of duel dioxide.

Example 4.

Exhalation, containing 200 to 70000 mg / m ³ NO, which resulted from a reduction denitration operation simulating the treatment of radioactive waste, was accrubbed in simulated radioactive aqueous waste of an approximate molar composition;

HNO ₃ 2; Fa / N0 _3/3 0.159; NaNO 3 0.01; Cr / N0 _3/3 0.02 »Ni / NOJ / g 0 ', 037; H ₃ PO ₄ &il;

MoO ₃ 0.117; Sr / NO 3 / g 0.027; Bo / NO3 / 0, 0.027; KNOg 0,064; lanthanide nitrate compounds 0 *, 477; Zr0 (N0 _3/2 0.106; Co / N0 _3/2 0.01; Oj TaOg 012; AgNOj 0.002; Cd / NOJ / g 0.002; solution represented the total concentration of 15 wt.% Ameal nitrates.

The resulting exhalate, leaving a two-stage ecrubber operating on the self-recirculating prilolp, exhibited an NO ₂ content, expressed in NO units, of between 50 and 18000 mg / m, representing nearly 100% dlapraporolonation efficiency / aal 75 denitrification effect electrochemical absorption.

Example 5.

Exhalation, containing NO at a total concentration of CCE 37 000 mg / m ³ was akrubrověna in an aqueous solution containing 1000 g of solution of 50 g NmN0 ₃ 400 g of Al / N0 _3/3 and 25 g of HN0 _third

The absorption temperature varied between 26 and 45 ° C, the pH of the absorption solution was 0 ° C.

The exhalation exhalation showed 21400 mg / m ³ NO ₂ (i.e. equivalent to 14000 mg / m ³ NO), which corresponded to 62%, and there was no increase in both the lontA NO 'circulation and the lontA content in the aqueous aboorption solution. NOg even in the sum of aspen nitrogen.

Claims (1)

The method of disproportionation of the irritant emissions in aqueous solutions * preferably at temperatures up to 45 ° C and a pressure of up to 74.5 MPa, to produce a predominant proportion of natoxic nitrous oxide and / or pulp and oxygen *, characterized in that the enrichment error is preferably with a predominance of nitric oxide, it is contacted with a β solution of at least one of heavy metal nitrates, preferably cobalt * nickel * iron, manganese, chromium, mSdl, zinc, cadmium or lead and / or uranyl and / or aluminum and / or lanthanum and / or actinide at a solution pH of between 0 and 6.