CN1068753A - The treatment of nitric acid tail gas by ammonified ammonium nitrate absorption Processes and apparatus - Google Patents

Abstract

The processing of nitric acid tail gas belongs to the chemical industry field.Solve NO in the nitric acid production tail gas _XPollute and the waste problem.Characteristics are: tail gas is used the ammonium nitrate solution that contains ammonia after the oxidation cooling removes acid mist be absorbing medium, finishes to comprise absorption of N O in the three ring absorption towers made from granite or acidproof brick _XTransforming the nitrous ammonium that is generated is ammonium nitrate and all processes such as ammonium salt particulate that wash in the gas phase, and absorptivity reaches more than 90%, NO _XReclaim with the ammonium nitrate form, the full payment that foot turns round in compensating operation, and have profit to scheme, cost of equipment only is 1/5-1/10 of stainless steel equipment commonly used.

Description

The treatment of nitric acid tail gas by ammonified ammonium nitrate absorption Processes and apparatus

The invention belongs to the chemical industry field.

One, preface: in nitric acid production, contain the nitrogen oxide about 2000PPM in a large amount of tail gas that discharged.Not only caused the waste of the resource and the energy, and atmosphere caused serious pollution, elimination or control to this nitrogen oxide, once reported several different methods both at home and abroad, but some shortcomings are all arranged, and as selectivity ammonia reducing process, the consumption ammonia high running expense that consumes energy is big, and do not reclaim product and energy, discharging tail gas contains NO _x400PPM; Non-selective reduction method is mainly " decolouring ", NO in the tail gas _xTotal amount does not reduce, if further NO is reduced to N ₂, process complications and catalyst will easily be poisoned; Alkali absorb method is handled back tail gas and is contained NO _x1000PPM, reclaiming nitrosonium salts also need increase evaporation crystallization equipment; Modenite method (solid absorption method) is handled back tail gas and is contained NO _x400PPM, adsorption capacity is low, and investment and running expense are big; Nitric acid absorption process, absorptivity only 70%, gas liquid ratio is little, dissolving NO _xNeed bleaching, cold and hot consumption is big.The running expense height absorbs the not treated NO of tail gas though high pressure is strengthened _xCan reach below the 200PPM, but once invest great, inapplicable to existing enterprise, only when Jian Xinchang, can consider [1].A good method should be: 1, can make NO _xBe reduced to below the 200PPM; 2, with NO _xRecovery becomes available product; 3, the stable and easy operating that keeps system; 4, do not consume too much energy; 5, reduced investment, device fabrication are installed easily; 6, can not produce secondary pollution, according to the reality of ammonium nitrate factory, developing a kind of is oxidant with rare nitric acid and air, is that the method that the continuous oxidation of absorbing medium absorbs is more satisfactory with the ammonium nitrate solution of ammoniacal liquor, both recyclable discarded ammoniacal liquor, the NO in the recyclable again nitric acid tail gas _x, become available ammonium nitrate products by conversion, and eliminated NO _xMurder by poisoning to environment is polluted, and reaches the treatment of wastes with processes of wastes against one another, the effect of achieving many things at one stroke.

The existing abroad industrialization report of treatment of nitric acid tail gas by ammonified ammonium nitrate absorption, still under test at home.Its cardinal principle is to utilize ammonia in the absorbing medium and the NO in the tail gas _xReact.U.S. GOOdPasture company had at first delivered the industrialization report in 1976, set up the exhaust gas processing device of handling 100T/ day nitric plant in March, 74 at Dimmit Taxes, ratify again subsequently to set up 250T/ day nitric plant exhaust gas processing device, United States Patent (USP) 3453071(1969 at RiChmOnt California) to introduce this method be 9 sections absorption towers.DRP 2513619(1976) introducing this method is 5 sections absorption towers, and wherein also having one section is absorbent with urea liquid.At home ammonification ammonium nitrate absorption process was once made lab scale, be two sections packed towers, consequently sure.

The characteristics of this method are, do not need special catalyst and cold and hot amount, and raw material is an ammoniacal liquor, and ammonium nitrate is an intermediate medium, handle the NO in the tail gas of back _xCan reduce to below the 200PPM NO of absorption _xReclaim with the ammonium nitrate form.From industrialized many methods in the world, treatment of nitric acid tail gas by ammonified ammonium nitrate absorption is most economical commercial run.

The present invention includes treatment of nitric acid tail gas by ammonified ammonium nitrate absorption industrialization process route and two capital equipments: the one, double-venturi oxidation cooling tower; Two is three ring absorption towers.Its advantage is that resistance is little, cost is low, intensity is high, corrosion-resistant, life-span length, compact conformation, can reduce large-scale pipeline link, simplify the operation, make install easily, small investment, running expense is low, absorptivity is high, do not produce secondary pollution, real is the ideal equipment of treatment of nitric acid tail gas, patent than the U.S. and West Germany all has essential improvement, and tower body can adopt granite or acidproof brick manufacturing.Cost is very cheap, is 1/5-1/10 of stainless steel absorption tower only, is particularly suitable for the national conditions of developing country.

Two, the main process and the reaction principle of this technology:

1, the oxidation of tail gas: because the nitric acid below 30% does not have oxidisability.So the mixture of the nitric acid of this process using 40-50% and air (or oxygen-enriched air) is with the middle NO oxidation of tail gas.Its oxidizability is brought up to more than 50%.Reaction equation is as follows:

2, use the ammonium nitrate solution absorption of N O of ammoniacal liquor _x:

3, the conversion of nitrous ammonium: add an amount of nitric acid and air and absorption liquid and tail gas and stream, transforming the nitrous ammonium is ammonium nitrate:

4, absorb salt made from earth containing a comparatively high percentage of sodium chloride particulate and remaining NO with ammonium nitrate solution (or water) washing _x: owing to generate a large amount of ammonium nitrate that is present in gas phase and nitrous ammonium particulate (aerosol), after also the circulationization absorber portion absorbs conversion, may also do not eliminated fully at the ammonification absorber portion.Remaining NO _xAlso should further absorb, in the hope of NO in the discharging tail gas _xLoss reaches minimum with ammonia.This section absorbs without the ammonification absorption liquid, is for avoiding the ammonia in the absorption liquid to be arrived gas phase and remaining NO by the gas belt _xGenerate the salt made from earth containing a comparatively high percentage of sodium chloride particulate once more, so that increase the ammonia loss, and produce secondary pollution.

Three, device structure and technological process:

(1) double-venturi whirlwind oxidation cooling tower structure and technological process:

Double-venturi whirlwind oxidation cooling tower is that tail gas filter (8) and antipriming pipe spray thrower (7) are arranged at the whole hollow tower (as shown in Figure 1) of garden cylindricality top, and there is gas distribution grid (5) middle and lower part, and top is that bottom, cooling zone (6) is zoneofoxidation (3).Gas inlet pipe (11) porch is that double-deck Venturi tube structure is communicated with tangent position with zoneofoxidation, there is double-deck nozzle (10) in tail gas, to spray nitric acid and the AIR MIXTURES of 40-50% in the inlet tube, with go into tower tail gas mix the back enter zoneofoxidation in the tower with tangential direction, and with tail gas in NO in rotary course, carry out oxidation reaction, the oxidizability of tail gas is brought up to more than 50%.Tail gas in the process of eddy flow under action of centrifugal force, after the intact nitric acid of unreacted separates, enter cooling zone, tower top (6) by distribution grid (5), cooling water (desalted water) counter current contacting under with the top spray, reduce below the exhaust temperature to 50 ℃, (tail gas is cooled to enter behind the three ring absorption towers with being reflected under 20 ℃-30 ℃ the temperature of ammonification absorption liquid to carry out), in the process of cooling, also can wash the most of acid mist in the tail gas simultaneously off, and the NO in the preliminary absorption tail gas _xAnd generating very rare nitric acid, the tail gas after the cooling encircles absorption towers by the filter (8) on top, cooling zone except that entering three from outlet (9) behind the acid mist, the preliminary absorption of N O of cooling cooling water _xAfter fall and mix the back with the remaining rare nitric acid that flows down from the tower wall after the zoneofoxidation oxidation reaction by the mozzle under the distribution grid (4) and go out from tower bottom flow, deliver to acid through storage tank (2) with pump (1) and absorb production station and be used for the acid absorption and (reclaim a part of NO _xGenerate nitric acid and enter production system).

(2) three ring absorption tower structure and technological processes:

Three ring absorption towers absorb tower bodies by diameter different three and are nested together with the form in concentric garden and form (as shown in Figure 2), outer tower and middle level tower cross section are annular, interior tower is a garden shape, outer shroud tower (4) does not load material, interior garden tower (6) and middle ring tower (5) are packed tower, Nei Yuanta leaves gross blow hole (3) with middle ring tower and communicates on the tower wall of packing layer bottom, three layers of tower all leave hopper (1) space below the passage position, three hopper bottoms with conduit respectively with tower outside hopper (11), (12), (13) communicate, outer shroud tower top communicates with middle ring tower separation with eddy flow plate shelves liquid devices (8), tower top, interior garden is provided with demister (9), at shelves liquid eddy flow plate and three towers below the demister position annular antipriming pipe spray thrower (7) is set all, the outer shroud tower installs many group spray throwers additional in the different level position, middle ring tower spray thrower installs air and nitric acid inlet tube additional, and tower demister top, interior garden and middle ring tower spray thrower also should install the clear water inlet tube additional.The ammonium nitrate solution of being drawn by interior tower bottom hopper adds the ammoniacal liquor ammonification in the hopper (13) outside tower, ammonium nitrate solution through ammonification is delivered to each spray thrower of outer shroud tower top by pump (14), along outer shroud tower hollow and two tower walls multilayer ring spray from top to bottom, form the large tracts of land liquid film at Liang Tabi, forming vaporific raindrop at annulus falls, tail gas through the oxidation cooling tangentially enters the outer shroud tower from inlet tube (2), rise along the form spiral of outer shroud tower (4) with cyclone, contact at a high speed with the ammonification liquid of outer shroud tower top multilayer ring spray, forming the vaporific gas-liquid mixed attitude of raindrop fully contacts, and carry out absorption reaction, solution behind absorption reaction, storage tank at the bottom of centrifugal action lower edge Ta Bi flow to the outer shroud tower, (added air or oxygen-enriched air have enough amounts during as the tail gas oxidation for the nitric acid of ring tower (5) top spray thrower spray and tail gas and the outer adding from then on of tower and air in delivering to pump (16) by conduit and storage tank (11), can no longer add air herein), from top to bottom also flow by the nitrous ammonium in the middle ring tower packing layer conversion solution.Tail gas through the ammonification absorption, by outer shroud tower top through the multiple shelves of eddy flow plate (8) and with enter after the ammonification absorption liquid of carrying secretly separates in encircle tower (5), air with the adding of middle Huan Ta top, the absorption liquid that nitric acid and pump (16) are sent up also flows together from top to bottom by middle ring tower packing layer, transform the nitrous ammonium in the absorption liquid, continue to absorb the NO in the tail gas simultaneously _xDuring absorption liquid through transforming flows at the bottom of the ring tower storage tank by conduit, flow to about storage tank outside the tower (12), ammonification adjustment PH-7 after, tower top, garden spray washing tail gas (or washing with water) in a part is delivered to pump (15), a part can be delivered to the production station evaporation and reclaim ammonium nitrate.The tail gas that ring tower secondary absorbed in the warp flows into interior garden tower by middle Huan Ta bottom passage (3), from bottom to top by packing layer, with water that from top to bottom sprays or ammonium nitrate washing absorption liquid counter current contacting, absorbs the NO in the tail gas once more _x, and wash the ammonium salt particulate of removing in the tail gas (aerosol), behind the demister (9) of tail gas that washing section absorbs, enter aiutage emptying by outlet (10) by tower top, interior garden.Ammonium nitrate that interior garden tower flows down washing absorption liquid adds the ammoniacal liquor ammonification behind the storage tank derivation tower at the bottom of by tower in storage tank (13), deliver to outer shroud tower top circulated sprinkling with pump (14) after ammonification.In order to prevent ammonium nitrate solution crystallisation by cooling (in temperature of this technology and the concentration range not can crystallization), occluding device, when stopping, use clear water flushing three ring absorption tower packing layers, and can add the small amount of steam insulation.

Four, to the explanation of the several problems of technical process:

1, the oxidation of tail gas and cooling:

Because NO in the tail gas _xMajor part is NO, and NO and NH ₄Therefore chemically reactive must not brought up to the oxidizability of tail gas more than 50%.In general, acid concentration is higher, and oxidation effectiveness with the nitric acid oxidation tail gas of 40-50%, consumes acid and is about 6g/m better ³Tail gas [7].This process using double-venturi whirlwind oxidation cooling tower, add part air (or oxygen-enriched air) with 40-50% nitric acid, tail gas and acid and air can well mix and contact in double-deck Venturi tube structure, and the improvement of its oxidation susceptibility, the minimizing of nitric acid dosage are sure.This is key character of this technology.With desalted water cooling is in order to recycle cooled dilute acid solution, and the tail gas cooling is in order to give NO in the operation tail gas of back _xAbsorption create good conditions, but and the most of acid mist after the oxidation in the flush away tail gas, can reduce the generation of ammonification suctionizations section " mist in vain ".(as the heat imbalance, then can at the bottom of tower, increase cooling coil, will recycle behind the cooling water temperature)

2, ammonification absorber portion reaction mechanism, ammonia concentration is to NO in the ammonification absorption liquid _xThe influence that absorbs:

According to the absorption double-film theory of generally acknowledging, the gas-liquid flow velocity is bigger, and the air film liquid film is thinner, absorbs the resistance littler [2] of diffusion.The absorption process that the ammonification absorber portion adopts many sprays to contact with whirlwind at the outer shroud tower, increased the speed of gas-liquid contact, thereby formed the high speed convection diffusion, just accelerated absorption process, because ammonia participates in reaction in gas phase, thereby has more quickened the speed of diffusion and absorption reaction, therefore, the outer shroud tower is relative, absorption of N O _xEfficient be higher, this is the principal character of this technology.

The ammonia content of ammonification absorption liquid is crossed conference increases the ammonia loss, and ammonia content is too small can be reduced NO in the tail gas _xAbsorptivity, it is heavy at 0.05-0.5%(that this process using can make ammonification absorb ammonia content in the solution of back) concentration (Operations Analyst is than convenient like this).NO in the tail gas then _xCan reduce to below the 200PPM, discharging tail gas does not have " white mist ".In operation can be according to the NO of tail gas _xContent is in time adjusted ammonia content in the absorption liquid, just can effectively control and run ammonia amount and NO _xContent is all below 200PPM.This process using absorbs the ammonia content that suitably increases ammonification section absorption liquid for three sections.The ammonification section is to NO _xAbsorptivity then can further improve, again through and flow that conversion zone absorbs and the absorption of counter-current absorption washing section capture.The ammonia loss can not increase NO in the tail gas yet _xContent will be lower.

3, spray flux is to NO in the tail gas _xThe influence of absorptivity and the selection of tower diameter:

According to the diffusion principle of absorption process, spray flux is big more, to NO in the tail gas _xAssimilation effect can be good more, but excessive spray flux can increase the consumption of power.Domestic lab scale proves, guarantee NO _xAbsorptivity more than 90%, sprinkle density should reach 8m ³/ m ³Two sections absorptions of hr(, gas liquid ratio is about 500: 1).Conference increase power consumption, and assimilation effect again is remarkable [7] not, now adopt three ring absorption towers, increased the absorption process of cooling section again, and the raising of absorption efficiency is undoubtedly, suitable minimizing internal circulating load, and it is possible widening gas liquid ratio.But sprinkle density can not be too small, theoretical proof, and satisfy the minimum spray density that the filling surface in the packed tower soaked into fully is 4-5m ³/ m ²Hr[3] so when selecting then tower diameter, can consider, promptly can consider the selection of big tower diameter by less sprinkle density.

4, the existence of nitrous ammonium and conversion:

Generation NH that can be quantitative in ammonification absorber portion course of reaction ₄NO ₂, theoretical proof, nitrous ammonium [4] soluble in water nitrous ammonium is stable [5] in the aqueous solution, containing under the condition of ammonia through evidence nitrous ammonium is stable [6], to NO _xAbsorption reaction do not have tangible influence [7].The tail gas of middle ring tower contains NH directly from the outer shroud tower in the gas phase ₄NO ₂, water and ammonia, so the outer shroud tower and in the upper gaseous phase of ring tower, the nitrous ammonium is stable, also is stable in absorbent solution, can not produce decomposition and explodes.

In order not make NH ₄NO ₂Bring NH into ₄NO ₃In the product, this process using is that an amount of air of adding can be effectively with NH about 0.5-2.0 at pH value particularly in pH value is the scope of 0.1-5.0 ₄NO ₂Be converted into NH ₄NO ₃In order to improve tail gas to NH ₄NO ₂Conversion ratio, this process using is sprayed the mode that adds nitric acid and air transforming cat head, this is to NH ₄NO ₂Conversion and NO _xTo continue to be absorbed all be favourable, through in the absorption liquid NH that transforms of ring tower ₄NO ₂Content can be controlled in below 0.1%, derives outside the tower, adjusts PH=7 in storage tank (12) ammonification and can send to evaporation recovery ammonium nitrate.

5, the concentration of ammonium nitrate and crystallisation problems in the absorption liquid:

The concentration of ammonium nitrate is excessive in the ammonification absorption liquid, can produce crystallization and occluding device, and the viscosity of the too small then absorption liquid of concentration is too small, and the dividing potential drop of water vapour and ammonia all will increase in the gas phase, thereby the NH that produces ₄NO ₂" white mist " is just many, and the ammonium nitrate solution of this process using 40-50% is absorbing on the liquid level, and the water vapour in the gas phase is low to the ratio of ammonia steam, and the nitrous ammonium of generation " white mist " is few, and this white mist is rapid and quantitative being absorbed by saltpetre ammonium solution especially easily.Looking into the solubility of ammonium nitrate in the aqueous solution, is 65.18% when (20 ℃) at normal temperatures, though in the time of 0 ℃ also up to 54.49%[8], and the course of reaction of this technology all is not less than 20 ℃.So under normal situation of driving, as long as inner-tower filling material is stacked rationally, bias current does not take place in gas, is can not produce crystallization and occluding device.

6, about the resistance problem of exhaust gas processing device:

Because oxidation cooling tower and outer shroud tower are hollow tower, all do not load material and column plate, so its resistance is very small.The resistance of whole device mainly occurs in Packed middle Huan Ta and Nei Yuanta, and we can select the less filler of resistance when detail design, select bigger measures such as tower diameter for use, make its resistance minimum.Theory is pointed out: under the air-flow (establishing the 85-95% that gets tolerable speed) of practical operation, to some customary filler (Tao Quan, saddle packing).The approximate range that pressure falls is the 40-70[millimeter of water/rice packed height] [9], if two tower packing height overalls are 40 meters, its resistance drop 0.16-0.28 technical atmosphere only then.According to the compression curve of rotary compressor, the rising of system pressure always approaches (being no more than), the value added of resistance drop.So, increase such resistance, to production system (the seeing explanation 7 for details) that can bear fully.Under special circumstances, if the Processes and apparatus of production system does not allow to increase this resistance.Then can consider increases by an air blast after production system, overcome the resistance of exhaust gas processing device, and this can make the turbocompressor increase that recovers energy concerning production system, and increases inflate quantity, improves the productivity ratio of system.

7, the variation of increase of turbocompressor electrical power and production system:

As 6 situations about mentioning are described, owing to after production system, increase exhaust gas processing device, must increase SR, thereby the energy that the turbocompressor expansion stages is reclaimed is understood quantitative minimizing, the power consumption of electronic turbine will quantitatively increase, this phenomenon that is inevitable.But after reaching new balance, its result will be the raising of system pressure, the improvement of sour acceptance condition, and the raising of efficient, the raising of product quality (acid concentration increase), tail gas pressure also can increase thereby increase the motive force that vent gas treatment absorbs accordingly.With certain complete middle pressure 270T/ day nitric plant is example: its design pressure is 4.5kg/cm ²Turbine rated current 168/159A, and the practical operation operating pressure only is 3.8kg/cm ², electric current only is 100/98A.All do not reach design level and specified index, facts have proved of operation, the turbine outlet improves 0.3kg/cm ²Pressure, its electric current only increases 5A, and such potentiality can be born fully to the resistance that overcomes exhaust gas processing device, though the turbine inflate quantity reduces to some extent, need not enlarge and exchange device more, and only many consuming electric powers just can be enhanced productivity, be absolute worthwhile, both improved production efficiency.Created necessary condition for eliminating tail gas murder by poisoning atmosphere pollution again.Domestic certain large-scale chemical fertilizer factory is in order to install exhaust gas processing device, overcome the resistance of device with the method that improves the tail gas turbine back pressure, and carried out actual measurement at multicomputer, it is no abnormal that the turbine back pressure is brought up to the 2500mm water column by the 170mm water column, turbine power increases to some extent, all right [10] such as equipment leakage, vibrations, noises.Therefore, it is fully feasible increasing exhaust gas processing device after production system.

More than produce nitric acid plant about the analysis of system pressure based on full middle-pressure process.As when considering that non-pressure process and full low-pressure process are produced the vent gas treatment of nitric acid, can consider that then (or afterwards) increases air blast (or air inducing) machine before exhaust gas processing device, overcome the resistance of exhaust gas processing device, if synthesis is produced nitric acid, can that exhaust gas processing device is installed equally be better with full middle-pressure process, if not all right just and non-pressure process, the same air blast that installs additional of low-pressure process entirely.

8, three ring absorption towers and venturi oxidation cooling tower not only can be used in the processing of nitric acid tail gas, can also be used for nitric acid and absorb production process, operations such as the preceding furnace gas purge drying of sulfuric acid absorption and vent gas treatment and catalytic oxidation, the processes such as alkali absorption of sour gas for another example.Because of tower body flower steel rock or acidproof brick manufacturing, when detail design as the air-tightness of considering three ring absorption towers and venturi oxidation cooling towers and whole compressive strength when not enough, then can consider when building tower, to use the acid resistant adhesive mortar cementation of fissures, and plaster with acid resistant adhesive mortar integral body in the appearance of tower.And equipped 100 * 100-300 * 300

6-

The acid-resisting concrete of 12 bar-mat reinforcement cast 100-200 thickness is to increase its air-tightness and whole compressive strength.

In order to overcome the stress that expands with heat and contract with cold, when driving (or parking), should slowly give heat, (or cooling) gradually heats up.Safety in the hope of equipment.

9, Economic and Efficiency Analysis:

The nitric plant is an example with the complete middle pressure of 270 ton per days.Its tail gas amount 38000m ³/ hr.Contain NO _x0.2%, folding NO ₂156.4kg/hr.Count 140kg/hr by reclaiming 90%.Be 3360kg every day, and rolling over 100% nitric acid is 4.6 ton per days, and counted 1380T by 300 days the whole year, because the deposed ammonia of used ammonia for reclaiming, and the final products that reclaim are ammonium nitrate, so annual recyclable ammonium nitrate is 1770 tons, are worth 1274400 yuan.(720 yuan/ton).

The operation running expense is handled tail gas expense [11] (dollar/year) by 300T/ day nitric plant nitric acid absorption process

Management	Operation	Maintenance	Cooling water	Steam	Electric power	Add up to
							4400	2200	2200	14980	17500	43250	84530

Folding 450,000 yuan of RMB (actual cost is low).Annual profit is ten thousand yuan of 127-45=82, and the ammonia reducing process that domestic many families adopt.One ton of nitric acid tail gas disposal cost of every production is that 11.17 yuan (80 years fixed prices) and product-free reclaim, as producing 80000 tons of nitric plants per year, to need the vent gas treatment expense every year approximately be 89.36 ten thousand yuan (80 years fixed prices), just seemed the superiority of this method by contrast.

Five, embodiment:

Example 1, a kind of NO that contains _xThe tail gas of 2420PPM, oxidizability 20-30% flow velocity 12-15M/SeC, tolerance 3350Nm ³70 ℃ of/hr temperature, the ammoniacal liquor with 0.65% (not containing ammonium nitrate) is with 2-3kg/cm ³Pressure, 8m ³The spray flux of/hr is divided two groups of sprays with 10 shower nozzles, and stream absorption processing, goes out to suck NO _x, 710PPM absorptivity 70.8% is discharged about 30 ℃ in tail gas, contains ammonia 0.49mg/l and contains ammonium nitrate 1.9mg/l, nitrous ammonium 3.6mg/l[12].

Example 1 explanation does not only add the ammonium nitrate medium with ammoniacal liquor and absorbs the higher NO of processing not oxidised temperature _xTail gas, the ammonia loss is big, and absorptivity is low, and " white mist " arranged.

Example 2, a kind of tail gas, normal temperature and pressure linear speed 0.9-1.08M/SeC contains NO _x1940PPM tolerance 1.5m ³/ hr, behind about 40% nitric acid oxidation, oxidizability is 90%, NO _xContent is brought up to 2820PPM gas and is filtered except that passing through two series connection absorption towers behind the acid mist, uses the ammonium nitrate solution of the 40-50% of ammonification to absorb processing, absorption liquid ammon amount import 0.123%.Outlet 0.062% absorbs sprinkle density 8m ³/ m ²Hr, after ammonification absorbs, tail gas NO _xContent is 280PPM, and absorptivity is 86%, and tail gas runs ammonia 43PPM NO after washing with water _xContent is 200PPM, and absorptivity increases to 90%, and it is OPPM that tail gas runs ammonia, total ammonium yield 88.7%.[13]

Example 3, a kind of gas, normal temperature and pressure, linear speed 0.9-1.08M/SeC contains NO _x2060PPM, tolerance 1.5m ³/ hr is 92.4%NO with about 40% nitric acid oxidation rear oxidation degree _xContent is brought up to 2640PPM, except that passing through two series connection absorption towers behind the acid mist, uses the ammonification liquid of the ammonium nitrate of 40-50% to absorb after filtration, and absorption liquid ammon amount import 0.126% exports 0.064, absorption sprinkle density 8m ³/ m ²Hr.Ammonification absorbs back NO _xContent is 200PPM, absorptivity 90.5%, and tail gas contains ammonia 66PPM NO after using the washing that contains ammonia 0.01% _xContent is 20PPM, and absorptivity increases to 98% tail gas runs ammonia 37PPM, total ammonium yield 65%.[13]

Example 4, another gas, normal temperature, normal pressure, linear speed 0.9-1.08M/SeC contains NO _x2270PPM, tolerance 1.5m ³/ hr, behind about 40% nitric acid oxidation, oxidizability is 90%, NO _xContent is brought up to 2520PPM, filters except that behind the acid mist, by two series connection packed towers, uses the ammonification liquid of the ammonium nitrate of 40-50% to absorb, absorption liquid ammonia content import 0.198%, outlet 0.051% absorption sprinkle density 8m ³/ m ²Hr, ammonification absorbs back NO _xContent OPPM, absorptivity 100%.Tail gas contains ammonia 73PPM, with acid washing back NO _xContent is 20PPM, and absorptivity drops to 90.2%, and tail gas runs ammonia 86PPM.Total ammonium yield 75.8%[13].

Example 2 examples 3 examples 4 all illustrate tail gas NO after the ammonification absorber portion absorbs _xContent can reach about 200PPM, and tail gas runs ammonia also below 200PPM, and through washing or contain that ammoniacal liquor is washed or acid washing, then absorptivity is all more than 90% as again, and tail gas runs ammonia and NO _xContent is all below 200PPM.Because the viscosity of water was big under ammonium nitrate solution was more synthermal.Therefore, absorbing through acid conversion zone after ammonification absorbs, also is rational with the saltpetre ammonium solution washing, purifying tail gas about PH=7 at last again.

Appendix:

I, reference:

[1] " chemical industry environmental protection " 1981 1 phases " about the suggestion of nitric acid tail gas improvement method " Beijing Chemical Research Institute's environmental protection institute etc.

[2] " chemical industry process and equipment " volume two P382 Higher Education Publishing House nineteen fifty-seven front page.

[3] with [2] P392

[4] " inorganic chemistry study course " volume two P448 People's Education Publishing House in December, 1964 second edition is worn volume such as stablize the country.

[5] " inorganic chemistry " volume two P253, in July, 1961 front page.

[6] " ammoniacal liquor and stream spray and absorbs the treatment of nitric acid tail gas Test Summary " research institute of chemical fertilizer factory of Ji Hua company 1980,12,15.

[7] " the ammonification ammonium nitrate absorbs the report of treatment of nitric acid tail gas lab scale " orchidization environmental protection institute 80,10

(8) " ammonium nitrate technology " P28 Chemical Industry Press, A, M, Du Bowei basic Я. И. the graceful work in Kiel

(9) with (2) P404

(10) " nitric acid tail gas is handled and driven to sum up " orchidization chemical plant 1981.3

(11) same (1) (12) are with (6) (13) same (7)

II, list of references:

1, GOODPASTURF chemistry null method and removal process

2, United States Patent (USP) 3452071(1969)

3, DRP 2513619(1976) nitrogen oxide is removed method and equipment (summary)

4, " 5% nitric acid absorbs NO in the tail gas _xTest Phase Report " 1979 January of clinical laboratory of Xingping Chemical Fertilizer Factory, Shanxi Prov.

5, " discussion of ammoniacal liquor absorption process nitric acid tail gas technology "

The Yin Bin friend of Xingping Chemical Fertilizer Factory, Shanxi Prov. ^※, Wang Bingren, 1980.9

6, " ammonia process operation method " Xingping Chemical Fertilizer Factory, Shanxi Prov. ammonium nitrate workshop

※ this paper author comrade Yin Binyou is former in the work of Xinping chemical fertilizer factory, and nineteen eighty-three is left this factory under order.Now be the member of environmental protective chemical industry research institute of Xinping county State Scientific and Technological Commission (part-time deputy director's post).

In January, 1992 is in Xinping

III, description of reference numerals:

Fig. 1-double-venturi oxidation cooling tower and schematic flow sheet:

1-pump 7-spray thrower

2-storage tank 8-filter

3-zoneofoxidation 9-tail gas outlet

The two shower nozzles of 4-cooling water mozzle 10-venturi type

5-gas distribution grid 11-gas inlet pipe

The 6-cooling zone

Fig. 2-three ring absorption tower and schematic flow sheet:

Hopper 9-demister at the bottom of the 1-tower

2-gas inlet pipe 10-tail gas outlet

3-breather pipe 11-storage tank

4-outer shroud tower 12-storage tank

Ring tower 13-storage tank among the 5-

Garden tower 14-pump in the 6-

7-spray thrower 15-pump

8-eddy flow plate 16-pump

Claims (6)

1, a kind of industrial method of treatment of nitric acid tail gas is characterized in that tail gas after the oxidation cooling removes acid mist, with the ammonium nitrate solution absorption NO wherein that contains ammonia _x, the NH that is generated in the absorption liquid ₄NO ₂Adding nitric acid regulates and to add air with tail gas behind the pH value and be converted into NH ₄NO ₃And recycling use, at last with truncate ammonium salt particulate in the gas of the solution of ammonium nitrate or washing, cleaning of off-gas.

2, method according to claim 1 is characterized in that the oxidation of tail gas and cooling are to finish in a kind of double-venturi oxidation cooling tower, in tower, the oxidizability of tail gas is brought up to more than 50%, and the temperature of tail gas dropped to below 50 ℃, special circumstances are 20 ℃-30 ℃.

3, a kind of double-venturi gas cyaniding cooling tower (as Fig. 1), it is characterized in that this tower is integral body of garden cylindricality, be to constitute by the cooling zone on top and zoneofoxidation two parts of bottom, the middle and lower part has the gas distribution grid separation to communicate, gas inlet pipe communicates with tangential direction and Ta Nei zoneofoxidation in the bottom, has two cover nozzles and inlet tube to constitute double-deck Venturi tube structure in the inlet tube.

4, method according to claim 1 is characterized in that:

(a) absorption of tail gas is to use through the 40-50% of ammonification ammonium nitrate solution, and wherein the content of ammonia should keep the weight concentration of 0.05-0.5% in the solution after the ammonification absorber portion absorbs.

(b) NH in the absorbent solution ₄NO ₂Be converted into NH ₄NO ₃PH value between 0.1-5.0, special circumstances are between the 0.5-2.0.

(C) washing, purifying of tail gas is the saltpetre ammonium solution (or water) with 40-50%.Its pH value is about 7.

(d) NO in the tail gas _xAbsorption, generating the conversion of nitrous ammonium and the washing, purifying of tail gas is to finish in a kind of three ring absorption towers.

5, a kind of three ring absorption towers (as Fig. 2), its architectural feature are that tower body absorbs tower bodies by diameter different three and is nested together with the form in concentric garden and forms.Outer tower and middle level tower cross section are annular, and the internal layer tower is a garden shape, and three layers of tower divide three sections to communicate with the form of series connection.

6, according to claim 3,5 described, it is characterized in that the tower bodies on double-venturi oxidation cooling tower and three ring absorption towers are granite or acidproof brick manufacturing, for increasing its whole compressive strength, its appearance is reinforced with reinforcing bar acid-resisting concrete.

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