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Content archived on 2022-12-27

INTERSTAGE COOLING IN CONTINUOUS PRECIPITATION OF ALUMINIUM HYDROXIDE IN ADG ALUMINA PLANT

Objective

Cooling of a part of the suspension during precipitation of aluminium hydroxide permits to increase the process productivity. Six innovatory heat exchangers (made by Barriquand, France) with plane and smooth plates will be used, which are easier to clean and to operate. The estimated average productivity gain is 4.23 %.L%
For 1 deg. C of cooling, we obtain 0,6 kg of Al2O3 by cubic meter of sodium aluminate solution. That means, for 5,93 deg. C of cooling for the period was obtained an increase of the liquor productivity equal at 4,23% or 25.750 t. per year of Alumina for the period (period = from 9/92 to 8/94 = 24 months).
The project consists in cooling one part of the suspension during decomposition. Due to the high content of the suspension in dry materials (800 to 900 g/l) it was necessary to choose a particular technology, that of the PLATULAIRES heat exchangers supplied by the BARRIQUAND company. Six exchangers are installed (3 per files) between the precipitations tanks 8 and 9, 9 and 10, 10 and 11 on one hand, 21 and 22, 22 and 23, 23 and 24 on the other hand. Each of the exchangers has a surface of 252,0 sq.m and receives 25% of the flow of the suspension (300 m3/h) which circulates at a speed of 1,4 m/s.
They are fed directly from the tank by an immersed pump (1 pump per exchanger), the cooled suspension going into the precipitator tank coming next. The cooling is performed by closed circuit with the water turning through an atmospheric refrigerant. The cooling water flow is of 240 m3/h per exchanger. Instruments to measure flow, temperature and pressure are installed to check the optimumoperation of each exchanger together with a bank of regulators for each exchanger which will vary the flow of the coolant according to the desired exit temperature of the suspension. All this information is processed automatically and transmitted to the screen in the control room of the decomposition unit. In order to avoid an eventual clogging of the exchanger due to accidental shut-down, an automatic disposition for washing the exchangers on the suspension side has been foreseen. All the same time, a cleaning circuit with soda has also been planned. This unit ensures an average cooling of 5,93 deg. C of the suspension, taking into account periodical halts, for the maintenance of the tanks and of the relative exchangers.

Call for proposal

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Coordinator

ALUMINIUM OF GREECE SA
EU contribution
No data
Address
ST. NICOLAS PLANT
320 Paralia Distomou (BEOTIE)
Greece

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Total cost
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