Parallel row tube and remaining tank dissolving-out system and method for gibbsite bauxite

Abstract

Provided are a parallel row tube and remaining tank dissolving-out system and method for gibbsite bauxite. The dissolving-out system comprises a circulating mother liquor tank, a two-series parallel row tube heating device, a mixer, a heat preservation remaining tank, a flash evaporation device and a diluting device. The two-series parallel row tube heating device is formed by connecting 2-3 groups of row tube heating devices in parallel, and each set of row tube heating devices is formed by sequentially connecting a primary row tube preheater, a secondary row tube preheater, a condensate water row tube heater and a live steam row tube heater in series. The method comprises the process steps that circulating mother liquor is conveyed to a two-series parallel row tube heating system through a mother liquor feeding pump to be heated, and then the circulating mother liquor and desilicated ore pulp are evenly mixed in the mixer and then enter the heat preservation remaining tank to be dissolved out; dissolved-out slurry is fed into the flash evaporation device, and enters the diluting device after being subjected to flash evaporation. According to the system and method, the ore pulp treatment capacity can be greatly improved, energy can be saved, and production cost can be reduced.

Description

technical field [0001] The invention belongs to the technical field of alumina production, and in particular relates to a dissolution system and method for gibbsite-type bauxite in parallel tubes plus a residence tank. Background technique [0002] At present, more than 95% of alumina plants in China adopt the Bayer process. The core of the Bayer method production process is the dissolution process of bauxite slurry. The purpose of dissolution is to make bauxite and circulating mother liquor react at a certain temperature to generate sodium aluminate solution. The reaction formula is: [0003] Al 2 o 3 (1 / 3)H 2 O+2NaOH+aq→2NaAl(OH) 4 +aq [0004] Due to the different chemical compositions of bauxite ores in various places, the required dissolution temperature varies greatly; for gibbsite, low-temperature and low-alkali dissolution methods are generally used; the main technical indicators for the dissolution of gibbsite-type bauxite are : Dissolution temperature is 135°...

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Problems solved by technology

[0006] 1. It is difficult to increase the production capacity of a single series: The theory and production practice have proved that the mother liquor and the desiliconization slurry are mixed first and then preheated and heated with multiple inner tubes and casings. Due to the limitation of seamless pipe manufacturing, the largest outer The pipe can only be DN=600, which limits the size and quantity of the inner pipe and cannot continue to increase. The maximum is 3 inner pipes of DN200. Under this condition, if the system flow is increased, the flow velocity in the casing will reach 3m / s Above, the system resistance loss is too large, the equipment wears out, the equipment manufacturing cost is high, and the operating cost is high, which is not economically reasonable.

[0007] 2. The scarring of the heater is serious, which affects the heat transfer efficiency: when the slurry is heated in the casing, it is easy to generate scarring (mainly caused by kaolinite reaction), and the casing heat exchanger is in the case of no scarring. The lower heat transfer coefficient is at least 1000~2000Kcal / m 2 .h.℃; in the case of scarring, the heat transfer efficiency drops rapidly, and the heat transfer coefficient drops to 550~800Kcal / m 2 .h.℃ or so, affect the heat transfer effect

[0009] ①Single-series heaters have limited processing capacity and cannot continue to be enlarged;

[0011] The mother liquor and pulp are mixed in the heat preservation tank, without separate mixing facilities, it is not easy to fully mix, and the temperature and pressure of the heat preservation tank are easy to fluctuate, resulting in unstable operation of the subsequent flash evaporation system

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