High-pressure dissolution-out and evaporation combined energy-saving method in production of aluminium oxide

Abstract

The invention relates to an energy-saving method in production of aluminium oxide and especially relates to a high-pressure dissolution-out and evaporation combined energy-saving method in production of the aluminium oxide. The method includes following steps: heating dissolved-out raw ore pulp with new steam employed in a high-pressure dissolution-out process to obtain new steam condensed water; performing a flash process to the new steam condensed water to form a flash steam under a pressure of 0.4-0.6 MPa; sending the flash steam through pipelines to a mother liquid evaporation process for partially replacing new steam; carrying out a multistage flash process to the dissolved-out raw ore pulp after the high-pressure dissolution-out process, wherein a flash steam, under a pressure of 0.4-1.0 MPa, is generated in first-stage flash from the fourth stage to the sixth stage in the multistage flash process with from the ninth stage to the eleventh stage being pre-heated; and sending the flash steam to the mother liquid evaporation process through pipelines for partially replacing the new steam. The method is characterized by employing a new high-pressure dissolution-out and evaporation combined energy-saving technology so that thermal energy in a system can be utilized better, thereby achieving a purpose of saving energy.

Description

technical field [0001] The invention relates to an energy-saving method for alumina production, in particular to an energy-saving method for combining high-pressure dissolution and evaporation in alumina production. Background technique [0002] In the process of producing alumina by Bayer process (or part of the Bayer process in the combined process), pressure cooking and dissolution and evaporation of mother liquor are the main energy-consuming (steam-consuming) processes. 98% of domestic bauxite is monohydraulic bauxite, which requires high-pressure dissolution. Under the current technology and equipment level, the secondary steam generated by high-pressure dissolution cannot be fully utilized, and the secondary steam that cannot be absorbed is produced by the final stage. It is directly discharged into the atmosphere from the evaporation or dilution tank, resulting in waste of heat, so that the comprehensive energy consumption of alumina produced by Bayer process in my c...

AI Technical Summary

Problems solved by technology

98% of the domestic bauxite is monohydraulic bauxite, which requires high-pressure dissolution. Under the current technology and equipment level, the secondary steam generated by high-pressure dissolution cannot be fully utilized, and the secondary steam that cannot be absorbed is produced by the final stage. It is directly discharged into the atmosphere from the evaporation or dilution tank, resulting in waste of heat, so that the comprehensive energy consumption of alumina produced by Bayer process in my country is much higher than that of foreign countries.

The secondary steam at the final stage of dissolution is mainly used to heat red mud washing water (direct heating), and the utilization efficiency is low

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