Process and apparatus for preparing urea from nh3 and co2

Claim 1

IN A CONTINOUS TWO STAGE PROCESS FOR PREPARING UREA FROM NH3 AND CO2 WHICH COMPRISE THE STEPS OF CONTINOUSLY SUPPLYING ALL OF THE NH3 AND CO2 TO BE REACTED TO A FIRST REACTION ZONE EXOTHERMALLY REACTING THE NH3 AND CO2 TO FORM AMMONIUM CARBAMATE IN THE FIRST REACTION ZONE AND OBTAINING A REACTION MIXTURE CONTAING CARBAMATE AND UNTRWACTED NH3 AND CO2, FEEDING THE RESULTING REACTION MIXTURE INTO A SECOND REACTION ZONE, REACTING THE REMAINING NH3 AND CO2 IN THE SECOND REACTION ZONE TO FORM ADDITIONAL CARBAMATE AND COVERTING THE CARBAMATE THEREIN TO UREA, THE IMPROVEMENT WHICH COMPRISES PROVIDING A COOLED FIRST ZONE AND AN INSULATE SECOND ZONE, CONTINUOUSLY MEASURING THE TEMPERATURE OF THE REACTION IN THE SECOND ZONE AND CONTINUOUSLY CONTROLLING THE COOLING OF THE FIRST ZONE BY REMOVING HEAT FROM THE FIRST ZONE AND REGYLATING THE AMOUNT OF HEAT REMOVED THEREFROM, THE CONTINOUS CONTROL AND THE REGULATION BEING RESPONSIVE TO THE TEMPERATURE MEASUREMENT IN THE SECOND ZONE WHEREBY THE TEMPERATURE IN THE FIRST ZONE IS CONTROLLED WITHIN THE RANGE OF 160*TO 175*C.SO THAT ONLY FROM 70 T0 90% BY WEIGHT OF THE CO2 IS REACTED IN THE FIRST ZONE TO CONTROL THE CO2 SUPPLY TO THE SECOND ZONE AND THEREBY CONTROL THE TEMPERATURE IN THE SECOND ZONE WITHIN THE RANGE OF 170*TO 200*C.