HRP940595A2

HRP940595A2 - Process for removing nitrogen oxides

Info

Publication number: HRP940595A2
Application number: HR940595A
Authority: HR
Inventors: Heinz Kucera; Erwin Niedermayer; Josef Tauschitz; Guenter Zellinger
Original assignee: Waagner Biro Ag
Priority date: 1989-04-26
Filing date: 1994-09-26
Publication date: 1996-04-30
Also published as: SI9010827A

Description

Tehničko područje izuma Technical field of the invention

Predloženi izum odnosi se na područje anorganske kemijske tehnologije i ekologije, specifično međutim na postupak za uklanjanje dušikovih oksida iz otpadnih plinova pomoću amonijaka, odnosno amonijačnih spojeva, u obliku vodenih otopina, koje ubrizgavamo u tijek otpadnog plina u temperaturnom području od 700 do 1200°C, te ih distribuiramo po cjelokupnom presjeku otpadnih plinova, i to zato, da zbrinemo otpadne vodene otopine iz industrije i/ili poljodjelstva. The proposed invention relates to the field of inorganic chemical technology and ecology, specifically, however, to the procedure for removing nitrogen oxides from waste gases using ammonia, i.e. ammonia compounds, in the form of aqueous solutions, which are injected into the waste gas flow in the temperature range from 700 to 1200°C , and we distribute them across the entire section of waste gases, in order to dispose of waste aqueous solutions from industry and/or agriculture.

Definicija tehničkog problema Definition of a technical problem

Poznato je da se u komoru za sagorijevanje, uređaja za proizvodnju pare, upuhavaju čvrsta sorpcijska sredstva i time se djelomično vežu štetne tvari kao SOx, klor, fluor i također dušikovi oksidi. Ti postupci imaju međutim nedostatak, da pri tome nastaju, odnosno zaostaju čvrsti kemijski spojevi, koji povisuju sadržaj pepela u otpadnim plinovima i na kraju krajeva opterećuju deponije. Daljnji nedostatak je u tome, da po tim poznatim postupcima u stupnju čišćenja većinom nije moguće doseći zakonski propisanu čistoću otpadnog plina, tako da su potrebne daljnje faze apsorpcijskog čišćenja, koje time povećavaju potrebu za prostorom i stoga nisu prikladne za stare uređaje, tim više što također drastično slabe radne rezultate. It is known that solid sorption agents are blown into the combustion chamber of the steam production device and thus partially bind harmful substances such as SOx, chlorine, fluorine and also nitrogen oxides. However, these procedures have the disadvantage that solid chemical compounds are formed or left behind, which increase the ash content in waste gases and ultimately burden landfills. A further disadvantage is that, according to these known procedures, it is mostly not possible to reach the legally prescribed purity of the waste gas, so further stages of absorption cleaning are required, which thereby increase the need for space and are therefore not suitable for old devices, especially since also drastically weaken work results.

Stanje tehnike State of the art

Poznato je upuhavanje plinovitog amonijaka u vruće otpadne plinove, pri čemu dolazi do redukcije dušikovih oksida, kod čega se pojavljuje nedostatak, da ,osobito kod promjenljivog sadržaja dušikovog oksida, amonijak ulazi kroz dimnjak, tako da su potrebne daljnje mjere, osobito preko katalizatora, koje nepotrebno poskupljuju postupak. Poznato je nadalje izravno upuhavanje uree, odnosno otopina uree u komoru za sagorijevanje (US-PS 4,208,386, odnosno 4,325,924), pri čemu se s dodatim aditivima može proširiti, odnosno promijeniti temperaturno područje u kojem je moguća razgradnja dušika. Taj postupak je vrlo nestabilan prema promjenama kod opterećenja i promjena temperature i što se veći dio organskih spojeva razgrađuje pri 1000°C, vrijeme trajanja uree vremenski je ograničeno, tako da zbog manjih promjena temperature dolazi do smanjenja redukcije NOx. It is known that gaseous ammonia is blown into hot waste gases, which results in the reduction of nitrogen oxides, which has the disadvantage that, especially with variable nitrogen oxide content, ammonia enters through the chimney, so that further measures are needed, especially via catalysts, which they unnecessarily make the procedure more expensive. It is also known to directly blow urea, i.e. urea solution into the combustion chamber (US-PS 4,208,386, i.e. 4,325,924), whereby with added additives, the temperature range in which nitrogen decomposition is possible can be expanded, i.e. changed. This process is very unstable to changes in load and temperature, and the larger part of organic compounds decomposes at 1000°C, the duration of urea is limited in time, so that due to smaller changes in temperature, reduction of NOx reduction occurs.

Opis rješenja tehničkog problema s izvedbenim primjerima Description of the solution to the technical problem with practical examples

Stoga smisao i namjera izuma je riješiti postojeće nedostatke amonijaka i također skladištenja amonijaka, kao također razgradnje uree, i po mogućnosti u samo jednom stupnja ukloniti dušikove okside iz otpadnog plina, ili ih reducirati tako, da odgovaraju zakonskim propisima o održavanju čistoće zraka. Therefore, the meaning and intention of the invention is to solve the existing deficiencies of ammonia and also ammonia storage, as well as urea decomposition, and preferably remove nitrogen oxides from the waste gas in only one step, or reduce them so that they correspond to the legal regulations on maintaining air cleanliness.

Pozitivan učinak sastoji se u tome da je amonijačnu vodu lakše skladištiti nego tekući amonijak. A positive effect is that ammonia water is easier to store than liquid ammonia.

Predloženi izum karakterističan je po tome, da amonijak, odnosno amonijačne spojeve i, u datom slučaju, jedan ili više aditiva u vodeno] otopini i plinovito, ili pomoćno sredstvo u stanju pare pojedinačno distribuiramo u tijek otpadnog plina, ili da amonijak, odnosno amonijačne spojeve ubrizgamo u tijek plinovitog ili pomoćnog sredstva u stanju pare, i tu smjesu distribuiramo u tijek otpadnog plina, pri čemu kao pomoćno sredstvo za upuhavanje redukcijskog sredstva s aditivom koristimo zrak za sagorijevanje, vodenu paru, komprimirani zrak ili inertne plinove, a kao aditiv reda veličine do maksimalno 10 mas. %, s obzirom na količinu amonijaka, koristimo organske spojeve koji sadrže dušik i/ili kisik, koje ili dodamo amonijakalnoj otopini ili na odvojenom mjestu primiješamo tijeku otpadnog plina u otopljenom obliku, da razgrade sekundarne emisije i/ili poboljšaju reaktivnost amonijaka, odnosno amonijačnih spojeva, osobito u smjeru nižeg temperaturnog područja. The proposed invention is characterized by the fact that ammonia, i.e. ammonia compounds and, in a given case, one or more additives in an aqueous solution and a gaseous or auxiliary agent in the vapor state are individually distributed in the waste gas stream, or that ammonia, i.e. ammonia compounds we inject into the flow of a gaseous or auxiliary agent in the state of vapor, and distribute this mixture into the flow of waste gas, whereby as an auxiliary means for blowing the reducing agent with an additive we use combustion air, water vapor, compressed air or inert gases, and as an additive of the order of magnitude up to a maximum of 10 wt. %, with regard to the amount of ammonia, we use organic compounds containing nitrogen and/or oxygen, which we either add to the ammonia solution or mix in a separate place with the flow of waste gas in dissolved form, to break down secondary emissions and/or improve the reactivity of ammonia, i.e. ammonia compounds , especially in the direction of the lower temperature area.

Daljnje bitne značajke navedene su u nastavku. Otopine aditiva sadrže organske spojeve koji sadrže dušik i/ili kisik, osobito glicerin, glikol i/ili druge otopine, koje sadrže viševalentne alkohole ili otpadne otopine, odnosno otopine iz industrije i/ili poljodjelstva. Further essential features are listed below. Additive solutions contain organic compounds containing nitrogen and/or oxygen, especially glycerin, glycol and/or other solutions containing polyvalent alcohols or waste solutions, i.e. solutions from industry and/or agriculture.

Redukcijska sredstva dodamo otpadnom plinu, ovisno o opterećenosti s dušikovim oksidima, koje treba ukloniti, osobito, međutim, u molskom omjeru do 2,0. We add reducing agents to the waste gas, depending on the load with nitrogen oxides, which should be removed, especially, however, in a molar ratio of up to 2.0.

Amonijačnu otopinu ubrizgavamo u vrući otpadni plin iz parnog kotla, koji plin sadrži prah, ložen prije svega s ugljenom prašinom, u komori za sagorijevanje na, odnosno iza razine plamenika, pri čemu prah koji nastaje u otpadnom plinu pri sagorijevanju u visokom temperaturnom području djeluje kao katalizator. We inject the ammonia solution into the hot waste gas from the steam boiler, which gas contains powder, fired primarily with coal dust, in the combustion chamber at or behind the level of the burner, whereby the powder formed in the waste gas during combustion in the high temperature area acts as catalyst.

Amonijačnu otopinu uvodimo u komoru za sagorijevanje na jednoj ili na više razina, ponajprije s vršnim zrakom, sekundarnim ili tercijarnim zrakom plamenika. The ammonia solution is introduced into the combustion chamber at one or more levels, preferably with peak air, secondary or tertiary burner air.

Amonijačnu otopinu ubrizgamo u dovodni vod vršnog zraka, te ju u njemu prethodno posušimo, a a njime ju također i jednakomjerno distribuiramo u atmosferi vodene pare u komori za sagorijevanje. We inject the ammonia solution into the peak air supply line, dry it beforehand, and distribute it evenly in the water vapor atmosphere in the combustion chamber.

Aditivno sredstvo otopimo u alkoholu ili nekoj drugoj organsko] tekućini i koristimo ga osobito razrijeđeno ili naplavljeno s vodom. We dissolve the additive in alcohol or some other organic liquid and use it especially diluted or diluted with water.

Reducent, u obliku otopine, se unosi u otpadni tijek preko sistema mlaznica, osobito novijih mlaznica vrlo male veličine kapljica, koje omogućuju finu i osobito jednakomjernu razdiobu po cjelokupnom presjeku otpadnog plina. Pri izvedbi pokusa uklanjanja dušika utvrdili smo da amonijačna voda, ako ju ubrizgavamo u komoru za sagorijevanje, suzbija tvorbu NOX, odnosno razgrađuje stvoreni NOx. Posebno dobre rezultate dobijemo ako amonijak otopimo u vodi i, prije uvođenja kroz mlaznicu u komoru za sagorijevanje, raspršimo ga kao otopinu u vrućem zraku, tako da u vrućem zraku nastaju prezasićene amonijačne kapljice, koje u posebno finom obliku ubrizgavamo u optočnu vodenu paru u komori za sagorijevanje pri temperaturama od 700 do 1200°C. Pojam vode ne vrijedi samo za čistu vodu, već osobito za otpadne otopine bilo koje vrste, kao što je npr. gnojnica, onečišćeno vino neprikladno za upotrebu, te vodeni kemijski otpaci, ako ne sadrže čvrste tvari. The reducer, in the form of a solution, is introduced into the waste flow through a system of nozzles, especially newer nozzles with a very small droplet size, which enable a fine and particularly even distribution over the entire section of the waste gas. During the nitrogen removal experiment, we found that ammonia water, if injected into the combustion chamber, suppresses the formation of NOX, that is, it breaks down the NOX created. We get particularly good results if we dissolve ammonia in water and, before introducing it through a nozzle into the combustion chamber, spray it as a solution in hot air, so that supersaturated ammonia droplets are formed in the hot air, which we inject in a particularly fine form into the circulating water vapor in the chamber for combustion at temperatures from 700 to 1200°C. The concept of water is not only valid for clean water, but especially for waste solutions of any kind, such as slurry, contaminated wine unsuitable for use, and aqueous chemical waste, if they do not contain solid substances.

Učinkovito temperaturno područje može se premjestiti ako otopini dodamo aditive kao što su triazini, cijanamidi, guanidini, a osobito njihove soli, količinama od 10% količine amonijaka. Pri tome, međutim, nije neophodno potrebno da aditive ubrizgamo otopljene zajedno s amonijakom, već ih možemo unijeti također i na nekom drugom mjestu, tako da se poboljša reaktivnost amonijaka. Također se pokazuju utjecaji izgorenog goriva, tako da se čine dokazljivim katalitički utjecaji letećih čestica, osobito kod rastućeg sadržaja teških metala. Daljnja značajka je, da amonijačnu vodu ne ubrizgavamo s primarnim zrakom, već s vršnim zrakom, odnosno sekundarnim zrakom ili s tercijarnim zrakom pri stupnjevitom sagorijevanju, za smanjenje tvorbe NOx u komori za sagorijevanje, tj . da amonijačna voda izazove malo zakašnjelu i produljenu redukciju. Stoga je također prikladno povratno sisanje dimnih plinova, osobito., dimnog plina bogatog kisikom, ako se naime gorivo spaljuje; sa suviškom zraka. Pri tome je međutim bitno -kako smo već spomenuli - da vodena para, koja nastaje pri sušenju otopine, katalizira redukciju. S molekulama vodene pare i napola vezanim kisikom, pobuđenim s visokim temperaturama, dakle praktički u nascentnom stanju, nastaju intermedijarni spojevi koji razgrađuju NOx, odnosno sprečavaju nastanak novih molekula NOx. Na svaki način, sadržaj NOx je na ulazu u dimnjak ili kod prethodno uključenog drugog stupnja čišćenja, u većini slučajeva spao na, do danas, zakonski podnošljive vrijednosti i ispod njih. Daljnji pozitivni učinci pojavljuju se kad je amonijak otopljen u ugljikovodicima koji sadrže N i/ili O, kao npr. viševalentnim alkoholima, osobito u vodenim smjesama ili emulzijama, pri čemu se čini prikladnim otpadne kemikalije, emulzije, kao vretensko ulje, eventualno s manjim sadržajem alkohola, ne nužno čiste, pri čemu se kod upotrebe dodatnih aditiva mogu spomenuti ili se od njih odustaje. Načelno možemo reći da se u nekoliko slučajeva može općenito odustati od upotrebe dodatnih aditiva ili otpadne otopine. The effective temperature range can be moved if we add to the solution additives such as triazines, cyanamides, guanidines, and especially their salts, in amounts of 10% of the amount of ammonia. In doing so, however, it is not necessary to inject the additives dissolved together with the ammonia, but we can also introduce them in another place, so that the reactivity of the ammonia is improved. The effects of burnt fuel are also shown, so that the catalytic effects of flying particles seem to be demonstrable, especially with the increasing content of heavy metals. Another feature is that we do not inject ammonia water with primary air, but with peak air, i.e. secondary air or with tertiary air during staged combustion, to reduce the formation of NOx in the combustion chamber, i.e. that ammonia water causes a slightly delayed and prolonged reduction. Therefore, it is also suitable to re-suction flue gases, especially oxygen-rich flue gas, if the fuel is burned; with excess air. In doing so, however, it is important - as we have already mentioned - that the water vapor, which is created during the drying of the solution, catalyzes the reduction. With molecules of water vapor and half-bound oxygen, excited with high temperatures, thus practically in a nascent state, intermediate compounds are formed that break down NOx, that is, they prevent the formation of new NOx molecules. In any case, the NOx content at the entrance to the chimney or with the previously included second stage of cleaning, in most cases fell to, to date, legally tolerable values and below them. Further positive effects appear when ammonia is dissolved in hydrocarbons containing N and/or O, such as polyvalent alcohols, especially in aqueous mixtures or emulsions, whereby waste chemicals, emulsions, such as spindle oil, possibly with a lower content, seem suitable of alcohol, not necessarily clean, while additional additives may be mentioned or omitted. In principle, we can say that in several cases the use of additional additives or waste solution can generally be waived.

Razgradnja, odnosno sprečavanje tvorbe NOx u visokom temperaturnom području zbog raspadnih organskih spojeva ima nadalje u prednost, da je na izlazu dimnjaka proboj reducenta neznatan, premda na strani goriva treba, osobito kod sagorijevanja smeća, računati s jakom tvorbom NOx. Zbog visokih temperatura tvorba sekundarnih emisija, odnosno organskih spojeva, održava se na krajnje niskoj razini. Osim toga ne nastaje ni jedan dodatni materijal za deponiranje, čak niti kad reducent doziramo k izlaznim NOx u nadstehiometrijskoj količini. Posebno dobri rezultati pokusa pokazali su se kod doziranja reducenta reda veličine jednostrukog, odnosno dvostrukog stehiometrijskog odnosa prema očekivanoj tvorbi N0X. Kod pokusa smo nadalje utvrdili da grijaće ploče tvorca pare nisu bile opterećene s dodatnim upuhavanjem amonijačne otopine, tako da nije došlo niti do taloga, niti do zapicanja, niti do dodatne korozije. Prema ovom postupku možemo upotrijebiti također i neprijatna goriva, kao što je npr. smeđi ugljen promjenljivog sadržaja pepela, a da se pri tome ne prekorače vrijednosti granične emisije, a pokazalo se je čak da se kod goriva bogatih s pepelom čini mogućim smanjenje potrebnog reducenta, čemu očito doprinosi i sadržaj teškog metala u letećoj prašini, odnosno njegov katalitički učinak. Načelno postupak je prikladan za uređaje za sagorijevanje za sva goriva, pa tako i za procesne otpadne plinove. Decomposition, i.e. preventing the formation of NOx in the high temperature area due to decomposing organic compounds, has the further advantage that the reductant breakthrough is insignificant at the chimney outlet, although on the fuel side, especially when burning garbage, strong NOx formation should be expected. Due to the high temperatures, the formation of secondary emissions, i.e. organic compounds, is kept at an extremely low level. In addition, not a single additional material for deposition is created, not even when the reductant is dosed to the output NOx in an over-stoichiometric amount. Particularly good results of the experiment were shown when reductant dosing was of the order of magnitude of a single or double stoichiometric ratio to the expected formation of NOX. During the experiment, we further established that the heating plates of the steam generator were not burdened with additional blowing of ammonia solution, so that there was neither sediment, nor sticking, nor additional corrosion. According to this procedure, we can also use unpleasant fuels, such as, for example, brown coal with a variable ash content, without exceeding the limit emission values, and it has even been shown that with fuels rich in ash, it seems possible to reduce the required reductant, to which the content of heavy metal in the flying dust, i.e. its catalytic effect, obviously contributes. In principle, the procedure is suitable for combustion devices for all fuels, including process waste gases.

Nije potrebno da amonijak bude otopljen u čistoj vodi. Za to su prikladne sve otpadne tekućine, ako otapaju NH3, i axo ne povisuju razinu štetnih tvari u otpadnom plinu, dakle vino koje sadrži glikol, voda koja sadrži ulje, alkohol za pranje, pri čemu mineralne otopine (solne otopine) mogu opet uzrokovati teškoće zbog stvaranja čvrstih sastojaka. It is not necessary for the ammonia to be dissolved in pure water. All waste liquids are suitable for this, if they dissolve NH3, and axo do not increase the level of harmful substances in the waste gas, i.e. wine containing glycol, water containing oil, alcohol for washing, while mineral solutions (saline solutions) can again cause difficulties due to the formation of solid ingredients.

Jedna od namjera izuma je također da se otpadne otopine, odnosno otopine iz industrije i/ili poljodjelstva koje sadrže amonijak, odnosno amonijačne spojeve, upotrijebe umjesto sintetičkih amonijačnih otopina pripremljenih za tu namjenu, kao npr. amonijačne vode. Nadalje, zamisao izuma je da se amonijačnim otopinama dodaju dodatni aditivi koji bi, s jedne strane, mogli poboljšati učinak čiste amonijačne otopine, spriječili daljnje sekundarne emisije ili za upotrebu proširili specifično temperaturno područje. Dodatni aditivi su u pravilu organski spojevi koji sadrže O i/ili N, koji se mogu dodati amonijačnoj otopini samo u neznatnoj količini. One of the purposes of the invention is also to use waste solutions, i.e. solutions from industry and/or agriculture containing ammonia, i.e. ammonia compounds, instead of synthetic ammonia solutions prepared for that purpose, such as ammonia water. Furthermore, the idea of the invention is to add additional additives to ammonia solutions that could, on the one hand, improve the performance of the pure ammonia solution, prevent further secondary emissions or expand the specific temperature range for use. As a rule, additional additives are organic compounds containing O and/or N, which can be added to the ammonia solution only in small amounts.

Dadatni aditivi mogu se također dodati i u obliku otpadnih otopina, odnosno otopina iz industrije i/ili poljodjelstva, koje sadrže gornje dodatne aditive. Kao primjer ovdje možemo spomenuti glicerin, odnosno otopine koje sadrže glikol, odnosno otopine koje sadrže derivate glicerina i/ili glikola, odnosno druge viševalentne alkohole. Additional additives can also be added in the form of waste solutions, i.e. solutions from industry and/or agriculture, which contain the above additional additives. As an example here we can mention glycerine, i.e. solutions containing glycol, i.e. solutions containing derivatives of glycerine and/or glycol, i.e. other polyvalent alcohols.

Pokazalo se je da su otopine dodatnih aditiva samo u nekoliko slučajeva doprinijele poboljšanju stupnja odvajanja, odnosno smanjenju sekundarne emisije, tako da nisu nužno potrebni za svaki slučaj upotrebe. It has been shown that the solutions of additional additives only in a few cases contributed to the improvement of the degree of separation, i.e. to the reduction of secondary emissions, so they are not necessarily necessary for every case of use.

Claims

1. The procedure for removing nitrogen oxides from waste gases using ammonia, i.e. ammonia compounds, in the form of aqueous solutions, which are injected into the flow of waste gas in the temperature range from 700 to 1200°C and distributed over the entire cross section of the waste gas, in order to dispose aqueous waste solutions from industry and/or agriculture, indicated by the fact that ammonia, i.e. ammonia compounds and, in a given case, one or more additives in an aqueous solution and a gaseous or auxiliary agent in the vapor state are individually distributed into the waste gas stream, or that ammonia, i.e. ammonia compounds are injected into the flow of a gaseous or auxiliary agent in the state of vapor and this mixture is distributed into the waste gas flow, whereby as an auxiliary agent for injecting a reducing agent with an additive we use air for combustion, water vapor, compressed air or inert gases, and as an additive of the order of magnitude up to a maximum of 10% with regard to the amount of ammonia, let's use organic compounds they contain nitrogen and/or oxygen, which we either add to the ammonia solution, or mix in a separate place with the flow of waste gas in dissolved form, to break down secondary emissions and/or improve the reactivity of ammonia, that is, ammonia compounds, especially in the direction of the lower temperature range.

2. The method according to claim 1, characterized in that the additive solutions contain organic compounds containing N and/or O, especially glycerin, glycol and/or other solutions containing polyvalent alcohols or waste solutions, i.e. solutions from industry and/or agriculture.

3. The method according to claim 1, characterized in that we add reducing agents to the waste gas depending on the load with nitrogen oxides, which should be removed, especially however in a molar ratio of up to 2.0.

4. The procedure according to claim 1, indicated by injecting the ammonia solution into the hot gas from the steam boiler, which gas contains dust, and which boiler is fired primarily with coal dust, in the combustion chamber at or behind the level of the burner, at why the dust that is formed in the waste gas during combustion acts as a catalyst in the high temperature area.

5. The method according to claim 1, characterized in that the ammonia solution is introduced into the combustion chamber at one or more levels, preferably with the peak air, secondary or tertiary air of the burner.

6. The method according to claim 1, indicated by injecting the ammonia solution into the peak air supply line, and drying it in it, as well as distributing it evenly in the atmosphere of water vapor in the combustion chamber.

7. The method according to claim 1, characterized in that we dissolve the additive in alcohol or some other organic liquid and use it especially diluted or flooded with water.

8. The method according to claim 1, indicated by the fact that the introduction of the reductant takes place in a dissolved form into the waste stream via a system of nozzles, especially newer nozzles of insignificant droplet size, which enable a fine and particularly even distribution over the entire cross-section of the waste gas.