NeutriNOx®” SNCR system for cement plants Optimization of ... - Fives

NeutriNOx®” SNCR system for cement plantsOptimization of the urea / ammonia consumptionCyril Dufau-Sansot, Deputy General Manager, Pillard Feuerungen Gmbh Taunusstein (Germany)Julien Ryckeboer, Senior R’nD Engineer, Fives Pillard, Marseille (France)BASIC FACTS ABOUT THE SNCR SYSTEMSCurrently, numerous cement kilns have nitrogen oxides (NOx) emissions exceeding levels set by future environmentalregulations. Fives Pillard, thanks to its NeutriNOx® system, provides the adequate solution to reduce NOx emission levelsand thus fulfil the future requirements, i.e.: 500 mg/(n)m 3 @ 10% O 2vol. dry eq NO 2. Cf. European Directive No.2001/81.This solution is based on a Selective Non Catalytic Reduction of NOx technique, using ammonia or urea reaction to reduceNOx from the flue gases since the cement process NOx emission can not be reduced to the European Directive levels onlywith Low NOx cement kiln burners like the Rotaflam LoNOx® type. Then the direct injection of diluted urea or ammoniasolution into the hot flue gases helps to reach the target:The SNCR principle is the following:Nitrogen oxides NO and NO 2(as NOx), generated during the combustion processes, are reduced by gaseous Ammonia NH3at high Temperature (ranging between 800°C and 1 100°C), thus:4 NO + 4 NH 3+ O 2 4 N 2+ 6 H 2O (R1)6 NO 2+ 8 NH 3 7 N 2+ 12 H 2O (R2)5 O 2+ 4 NH 3 4 NO + 6 H 2O (R3)The reduction reactions R1 and R2 are predominant. However, above 980°C, reaction R3 yields increased NOx, instead ofreducing the NOx concentration and, as a result, overall efficiency goes down, as shown as follows:DeNOx Efficiency of the SNCR System: n = (NOx Initial – NOx Final) / (NOx Initial)Therefore, it is of utmost importance to inject the urea or ammonia solution at the optimal gas temperature. As the DeNOxefficiency is a function of two parameters, temperature and molecular ratio (NH 3/ NOx Initial), this maximum efficiencylevel is at around 960°C and it can be increased further by refining the molecular ratio.1/8

Why using urea instead of ammonia?The reducing agent, gaseous ammonia (NH 3), may be supplied by either: Aqueous solution of ammonia ranging from 10 to 35 % (m/m). For a concentration higher than 25 % (m/m) the productis considered in Europe as hazardous and requires compliance with very high level safety measures for storage and handling.or Aqueous solution of urea ranging from 25 to 45 % (m/m) CO(NH2)2 . Above 200°C the urea decomposes as follows:CO(NH 2) 2+ H 2O CO 2+ 2 NH 3(R0)Given its physical and chemical properties, urea is safer and easier to use. However the efficiency of ammonia solution isgenerally higher than urea.Therefore Fives Pillard uses urea as well as ammonia solution base product for its NeutriNOx® system in cement plants.Choice, urea and ammonia solution will be made depending on product price, availability from local chemical suppliers andexpected range of temperature.The NeutriNOx® main components are both ammonia and urea resistant.ENGINEERINGSITE MEASUREMENTNOx, TEMPERATUREFLUE GAS FLOW MODELLINGTEMPERATURE AND VELOCITY PROFILEATOMIZING MODELLINGLOCATION, NUMBER OF GUNS, PENETRATIONCHEMICAL AND FLOW MODELLINGANALYSIS OF UREA MIX IN THE REACTION ZONEFives Pillard can provide a complete installation from the solution tank to the injectors and has, for this purpose, developeda complete engineering process.Site measurement & flue glas flow modellingThrough site temperature monitoring, Fives Pillard determines the adequate and appropriate reaction area (for existingplants). Then, Fives Pillard calculates the flue gas balance and simulates the velocity and temperature profiles in the reactionarea, using CFD (Fluent) as follows:2/8

Velocity and Temperature profiles at kiln outletAtomizing Modelling & Chemical and Flow ModellingA second phase consists of atomization and particles modelling, as well as, efficiency optimization within the reaction area:The number of injectors and their location / penetration point(s) are optimized by The FIVES PILLARD “NeutriNOx®” SNCRsystem as follows:First level: main injectionSecond level optimizationFirst and second level injectors3/8

Injectors & AtomizersFives Pillard injectors are patented devices that have been developed especially for this application. They generate a veryfine spray, allowing quick reaction between urea / ammonia and NOx particles as follows.Each injector atomizer will be designed for a penetration which will vary according to the location, diameter of the duct andother operating parameters.Penetration of an injector means the projection of the (solution - air) emulsion momentum on the required axis. It representsthe capacity of each jet of an atomizer to cross and mix with the main flue gas flow as follows.PAtomizerUreaAmmoniaCompressedairPatented Fives PIllard injectorThe Fives Pillard atomizing device (fluid atomizing type) and NeutriNOx® system ensure maximum penetration andconsequently the best mix spread in the reaction area, thanks to: Highly efficient injectors. The Possibility to optimize the atomizer, such as number of holes, angles, etc. during the engineering phase. The Possibility to optimize the atomizing parameters without changing the atomizer, by adjusting the atomizing airconsumption and/or water quantity during the commissioning phase. As a result, the risk of NH 3emissions at stack isgreatly reduced. These parameters can also be set by the NeutriNOx® control system.Injector connected to a ductFives Pillard atomizer & spray4/8

TargetThe modelling target in the engineering phase is covering the complete cross section of the duct with the diluted urea /ammonia spray:Profiles of Mass fraction of NH 3THE FIVES PILLARD SNCR NEUTRINOX® SYSTEMIt includes: tank / control cabinet / skids / 2 levels of injection guns with several atomizers.To increase the turn down ratio of the injectors and to increase the penetration of jets, urea / ammonia solution can bemixed with water. Afterwards this solution is injected and atomized. Depending on the CFD modelling conclusions, thesolution is dispatched through 6 - 10 Nozzles, installed at 1, 2, or more levels in the calciner. Usually two levels are required.While the first level covers the maximum surface and has longest resident time, the second level optimizes reaction andefficiency.The flow rate of solution is directly controlled by the NOx emission at stack. The quantity of water is controlled to ensurethe highest injection efficiency. Thus, this configuration allows an accurate control of the NOx emission at stack thanks tomaintaining the highest penetration efficiency.Flow principle5/8

In addition to temperature profile, burner and raw meal inlet position, others parameters are taken into consideration tooptimize the urea / ammonia solution at engineering and commissioning phases, such as (for example): Burner Load, NOxCO and O 2content in the flue gas at kiln outlet, secondary air temperature and NH3 emission value at the stack – see aboveDepending on the ammonia or urea solution, tanks have to be heated or cooled internally.Fives Pillard can provide unloading units and tanks. To prevent freezing and / or crystallization of the urea solution, thetemperature control of the tank, as well as, the concentration of the urea are defined. In most cases, a 40% concentrationis recommended for the NeutriNOx® process.On the other hand, Ammonia has a very low vapour pressure. Therefore, the ammonia concentration must be carefullydetermined to prevent gasification in the tank, which in this case has to be cooled. Usually, a 25% Ammonia concentrationm/m or lower is best, avoiding the use of hazardous product standards to design tanks and handling system.First stage injectorsUrea TanksSecond stage urea gunsSITE RESULTSFives Pillard has already installed their NeutriNOx® SNCR system at a couple of plants.Applying a methodical approach based on their engineering process, Fives Pillard conducted a series of comprehensivetemperature measurements that was followed by a complete Fluent® simulation carried out to maximize the DeNOxreaction efficiency on site at ITC Salerno. By analysing the temperature and velocity profiles in the reaction zone of thecalciner, and by optimizing the urea injection (which concerns the choice of injection points, number of injectors and theirparameters, such as angle, velocity, water concentration, penetration of jets, etc.), Fives Pillard could determine the idealposition for their special injectors, ensuring optimal atomization fineness and future adjustment possibilities (momentumof jets and choice of angles and holes).Flow control skidPumping unit6/8

Control cabinetFlow meter skidA reduction of NOx emission up to 65% has been reached:Salerno plant resultsA second application has been realized in Asia. Due to the high capacity of the cement line (nearly 5,000 tpd), the engineeringphase led to installing two level with six injectors each. Optimization, during commissioning in March 2006, defined theoperating parameters for best results in automatic mode. Fives Pillard applied the same simulation method as in the ITCSalerno case. Operating the NeutriNOx ® system in automatic mode, guaranty to keep the NOx emissions at the stack in arange of +/- 5% of the set point, and allowing optimal Urea / Ammonia consumption.Other sites were commissioned during 2006 - 2007, among others in Italy, bringing new experience. Numerous kinds ofcalciner technologies (see figure 17) and operating conditions met on site, allowed Fives Pillard to refine the CFD modelsand hypothesis used to define the best position for the injectors.7/8

Calciner technologiesITC Vibo Valentia is a good example, where data collected during the commissioning period, drove us to change thehypothesis taken and so the position of injectors. They will be moved down in the calciner chamber, allowing an increase byabout 15% of deNOx reaction efficiency(NOx / NH )reacted 3 injectedProductionTPDGuns level1 + 2Temperatureat level 2Summary of SNCR resultsMax urea flowrate (L/H)MaxefficiencyMaxreductionITC Salerno 1,315 4 + 4 860°C 720 80% 73%ITC Collefero line 5 1,260 0 + 4 870°C 620 47% 71%ITC Collefero line 6 2,150 0 + 4 930°C 580 57% 60%HOLCIM Hon Chong 4,600 6 + 6 940°C 1,600 26% 50%ITC Vibo Valentia 2,180 4 + 4 870°C 700 15% 38%CONCLUSIONThanks to this genuine technology, Fives Pillard has been able to optimize Urea / Ammonia solution consumption, yieldingthe required NOx emission level, while avoiding an excessive consumption of solution. This leads to a saving of up to 25%of solution consumption (compared with non optimized approach), yet keeping the same DeNOx efficiency. In financialterms, that means a NOx reduction cost of about 120,000 € per year for a 3,225 TPD kiln (based on a cost of 90 €/T for ureasolution @ 40% m/m).8/8