Heat Exchanger World magazine April 2024 | Page 37

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Materials
Agitators T = 230 ° C
98 % Sulphuric acid
T = 260 ° C
Autoclave
Flash vapor stage nr . 1 , T = 212 ° C
Steam T = 260 ° C
Flash stage nr . 1 T = 212 ° C
Preheater nr . 1 T = 160 ° C
Flash vapor stage nr . 2 , T = 165 ° C
Final heater
Atm . mixing condenser
Flash stage nr . 2 T = 165 ° C
Preheater nr . 2
Slurry
Condensate
Flash vapor
Atm . flash stage T = 100 ° C
T = 65 ° C
HP Pos . disp . feed pump
Hot process water Fresh slurry
Slurry discharge
Hot process water
Cold water
Figure 2 . HPAL for laterite nickel with indirect heat transfer ( self-cleaning heat exchangers ).
Figure 3 shows that it would also be possible to modify the existing directly heated laterite nickel processing plants into an indirectly heated configuration employing self-cleaning heat exchangers . Installing the indirectly heated flow path employing self-cleaning heat exchangers parallel to the existing directly heated flow path creates a unique flexibility in the operation of the plant enabling an easy return or fall-back from the ‘ new ’ technology on the ‘ old ’ technology , if necessary .
Because of the reliability of the self-cleaning heat exchangers , the fall-back possibility from ‘ new ’ on ‘ old ’ technology and the large benefits which can be achieved by the operation of the indirectly heated self-cleaning exchangers , the installation of full-size self-cleaning heat exchangers parallel to the existing directly heated installation should be considered , instead of rather costly small-scale pilot-plant testing prior to the installation of full-size self-cleaning heat exchangers .
98 % Sulphuric acid
T = 260 ° C
Agitators
Spray tower final heating ( mixing condenser )
Autoclave T = 230 ° C
Indirect Direct
Direct Indirect
Steam , T = 260 ° C
Flash vapor stage nr . 1 , T = 212 ° C
Self-cleaning HX ( SCHX )
Flash stage nr . 1 T = 212 ° C
Indirect Direct
SCHX
Condensate
Atm . mixing condenser
Flash vapor
Flash vapor stage nr . 2 , T = 165 ° C
Flash stage nr . 2 T = 165 ° C
Atm , flash stage T = 100 ° C
T = 65 ° C
Slurrt storage tank
T = 127 ° C
T = 191 ° C
SCHX
HP Pos . displ . feed pump
1 st Stage Spray Tower ( mixing condenser ) incl . heat exchanger
Condensate
Condensate
2 nd Stage Spray Tower ( mixing condenser ) incl . heat exchanger
Fresh slurry
Slurry discharge
Hot process water
Cold water
Figure 3 . HPAL for laterite nickel employing direct heat transfer revamped into indirect heated configuration .
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