Technical Paper September 2012

The LP Prilling Bucket For Urea

Mr.LiuXiaodi Inventor ofLPPrillingBucket, Chief Engineer Beijing AerospacePropulsionInstitute(No. 11 Institute). E:liuxd2006@126.com

The LP Prilling Bucket for Urea and its support system are installed at the center of the prilling tower top. By means ofthe motor thebucket can rotateat acertainspeedand make theureameltentering thebucket andjetoutbythecentrifugalforcetogetinto contactwiththeair comingfromthebottom ofthe tower,whereafterthedropletsshapeup(almostspherical),solidify andcool.

Prilling machine

1. Main design parameters of LP Prilling bucket Themaindesign parametersofthe LP Prilling bucketaredetermined bythefollowing: Prilling capacity Towerinnerdiameter Towerheight(effectiveheightforcooling) Barometricpressure Temperature Humidity

2. Features of LP Prilling bucket TheLP Prilling buckethasthefollowing features,which arecriticalfortheperformance:

Surface cone The surface cone is the most important parameter for LP bucket, and it determines the surface pressure distribution and affects the speed distribution of the urea melt leaving the bucket, and thus affects the prilling area in the tower. The cone design must consider accordingly the capacity, tower diameter,etc. Typically the LP bucket surface cone is: 8~25(varied accordingly) whereas for example a TUTTLE bucketconeis!5(andalmostfixed).

Jet hole densityhole number per area on surface Theoretically, we wish the same number of urea particles or the same urea quantity scattered on every area of the tower cross section, but this is very difficult to realise. We realize the optimum distribution by calculating the best distribution of the jet holes on the bucket surface and thus realize thebestparticlescatteron thetowercross section. Typically the hole number (single level) at LP bucket top is more than 50% at the LP bucket bottom, whiletheTUTTLE bucketsholenumberisthesameat everylevel.

Direction of the jet holes The direction of the jet holes determines the distribution of particles over the cross section of the tower. Thebetterofthe distribution,the better the cooling effect and the betterthe crushing strength ofthe prills. TheLP buckethasadifferentholedirection (horizontal)atthetop and bottom,whilewith aTUTTLE bucketitisthesame.

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Manufacture Themanufacturetechninqueis the most important elementfortheperformance ofthe bucket. LP Bucket Non-equilibrium Surface welding 5g-cm Beforeassembly in-andoutside iswelded TUTTLE bucket 7~15g-cm Afterassembly outside iswelded only

Surface cone Vertical welding

Perfectcone Perfectstraightline

Almostcone Almostline

3. LP prilling bucket references LP prilling bucket has a better performance, lower price, shorter manufacturing time and a better after-sales service. More than 500 sets have been in operation in China with capacities ranging from 480 mtpd to 3650 mtpd. Many urea plants replaced the TUTTLE bucket by the LP bucket achieving a significant better performance, for example Zhongyuan Co., Jinxi Co., Daqing Co., Jiujiang Co., Nanjing Co., NeimengtianyeCo.,Fuling Co., Sichuantianhua Co., Dongting etc.

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