Heaters & Exchangers

SNC Lavalin rationalised the flow sheet for Vale’s massive Goro Nickel project to use less equipment and inter connecting piping by combining a pre heater with its corresponding flash vessel. Jord was engaged for the detail mechanical design and fabrication of the revolutionary vessels. These vessels resembled giant dumb bells with the slurry preheater residing in the top section above the flash vessel at the bottom. Each autoclave required three combined flash / heaters vessels of up to 21m in height and 5.3m in diameter, at the widest point of the flash section. The heaviest vessel used for the high pressure flash weighed over 300 tonnes prior to the lining of the flash section. The image below shows 7 of 27 vessels and heat exchangers that Jord supplied to this milestone project. Materials of construction were a combination of clad titanium, incolloy. Refractory was brick lining.

For a major expansion project of an Alumina plant, Jord designed, fabricated and supplied 24 (check) x flash vessels, reactors and tanks of various sizes and duties. Whilst the vessels were fabricated overseas, extreme care was taken to ensure they were designed in strict accordance to Australian AS standards. With diameters up to 7m, logistics became an issue, for their 8,000 km journey over land and sea.

The below vessel flashes dissolved H2S from a mixed sulphides slurry located downstream of the autoclaves. Alloy 31 was selected to eliminate the conventional, costly and time-consuming approach of acid brick lining the vessels on site.

Broadly speaking the diameter of a direct contact heater relates to its capacity and the height relates to its efficiency, commonly measured by the approach of the liquor outlet temperature to the temperature of the heating steam. Provided that all of the steam is condensed and the amount of air and other non condensing gases is reasonably low, the capacity is set by the flow of slurry. For this project, Jord achieved the required approach in a series of vessels that were significantly smaller in diameter than those of its competitors by noting that at steady state there is always sufficient feed to condense the steam generated by flashing the product leaving the autoclave. Consequently the pre heaters could be sized based on the slurry flow using well proven design procedures. Four trains of low, intermediate and high pressure pre heaters were supplied with the high and intermediate pressure units mounted above one another in towers as depicted.

The direct slurry heaters referred to above has the disadvantage of diluting the slurry with water. In an effort to overcome this, Jord participated in demonstration plant studies to develop an indirect slurry heating process. The pilot plant modularised 39 shell and tube exchangers fabricated out of titanium and super-duplex materials. The plant collected heat transfer and fluid scaling data.