Flow and mass transfer model as well as scale up of an external loop ammoniation reactor are studied under commercial condition in this paper. The results show that the flow model in reactor approches perfect mixed flow

when the recycle ratio β is 22 1 and the model parameter m is near 1. The model is fitted with the actual operation condition and can be used to scale up for commercial reactor. The previous research

in which macro kinetics of ammoniation of phosphoric acid was measured in a double magnetic stirring reactor

found that the reaction between wet phosphoric acid and gaseous ammonia was a rapid reaction controlled by the gas film mass transfer. Hence a new mass transfer model based on this mechanism is obtained by using a laboratory reactor. The model is studied on a pilot scale reactor with a capactiy of 10 kt MAP·a -1

and then verified by using an commercial reactor with a capacity of 60 kt MAP·a -1 . The final mass transfer model of reactor is as follows:k G a=0 61W 0 3 a q 1 2 a The model is used for reactor scale up to a large commercial scale of 120 kt MAP·a -1 . It is found that the key factor of scale up should be q a= W a S t/ S r

i

e the ammonia loaded kg per unit time

per unit cross section area of reaction tube.