**2.5 Conclusions**

Nile water treated with NALCO inhibitors caused fouling problems inside CO2 coolers in different Egyptian ammonia plants. Technical solutions including redesigning of the PHEs and new plate geometries were investigated. Reducing the surface area of the CO2 coolers by 34% increased the gap velocity from 0.30 to 0.42 m/s (shear stress from 5.31 to 10.84 Pa) and hence decreased fouling. The operation time for the cooler was increased from 30 days to 43 days. NT-plates with asymmetric flow distribution over the channels decreased the rate of deposition on the surface of the plates.
