Nonferrous Metallurgy

Alumina can be produced in four ways, they are alkali process, acid process, acid-alkali combination, and hot process. Alkali process is divided into Bayer process, sintering process and Bayer-sintering combination method. Alkali process is the method of treating aluminum ore with alkali to change the alumina in the ore into sodium aluminate solution, inpurities suach as iron and titanium in ore and most silicon become insoluble compounds, separate the insoluble residue (red mud) from the solution, the useful components were recovered by washing, the pure sodium aluminate solution was decomposed into aluminum hydroxide, which was separated from the mother liquor, washed and then roasted to obtain alumina products.

The application of plate heat exchanger in the alumina industry is mainly the decomposition section of the refined liquid cooling, cooling step by step (respectively with the mother liquor and water heat exchange) to the process temperature. As the refined liquid ( oversaturated sodium aluminate solution) is prone to "scarring", it is necessary to clean the plate heat exchanger regularly, the cleaning solution is strong alkali or strong acid. Plate materials can be 316L, 254SMO, al-6xn, etc.

Full-welded wide channel plate heat exchanger is applied to the cooling section in the middle of decomposition and grading process in the process of alumina production. Its main applicable features are as follows:
1.The wide channel side running medium is aluminum hydroxide slurry, the medium flow rate is generally 0.6 ~ 1.2m/s. A high flow rate causes the slurry containing solid particles to flow over the surface of the plate without accumulating or scarring.
2.The wide channel side has no contact point, and the fluid can realize completely free flow, and is full of the entire flow channel formed by the plate, and the plate surface is almost involved in heat exchange, realizing the flow without "dead zone" in the flow channel.
3.The slurry inlet and outlet is provided with distribution structure. The slurry first passes through the distribution port, then enters the distribution box, and finally enters each wide channel evenly.
4.Both slurry side distribution box and cooling water side pipe box adopt the dismountable structure of plane cover plate, sliding door type principle, which can be disassembled at any time.

5.The plate pairs are spherical welded with good force form, pressure capacity is stronger.
6.The plate is made of SAF2205(S31803) dual-phases steel, which is the best solution to corrosion and abrasion.
7.The form of plate pack is horizontal, feed slurry comes in below and out above, effectively inhibit slurry settlement and scarring.