Background technology:
In recent ten years, the dissolving-out process of China's alumina producer has been made significant headway, multiple advanced person's dissolving-out technology has obtained to use and develop, as complete single-sleeve preheating, the autoclave insulating and leaching technology of French A, P dissolving-out technology, German VAW dissolving-out technology, China oneself development.
They are compared with the old dissolving-out technology in past and are significantly improved, bring up to 260~280 ℃ as the stripping temperature from original 240~245 ℃, realized whole raw pulp whole process indirect preheating and indirect heating, the dissolving device operation factor increases substantially, and the stripping hear rate reduces; Dissolution fluid α
kSeveral key indexs of judgement result of extraction such as value, red mud alkali ratio, digesting efficiency of alumina had all improved many than past.
Along with the progress of dissolving-out technology, the improvement of technical indicator, its corresponding technology should be adjusted, and just can obtain optimum economic benefit.For example, the dissolution fluid α of old stripping of past
kValue is generally 1.60~1.65, and new dissolving-out technology α
kValue can reach 1.40, even 1.30~1.35; Even design scale is the small scale aluminum oxide factory of 50kt/a only, dissolution fluid α
kValue is also below 1.40, and after the employing indirect heating being described and improving the stripping temperature, the result of extraction of ore is very good.
Under the identical situation of caustic sodium concentration, dissolution fluid α
kBe worth lowly more, alumina concentration is then high more in the dissolution fluid, and result of extraction is also good more, illustrates that simultaneously the production capacity of dissolving device has improved, and the cycle efficiency of circulating mother liquor has improved.Dissolution fluid α
kBring many benefits though value reduces to producing, also bring some disadvantageous effects simultaneously, as Al in the solution
2O
3Degree of supersaturation is too big, and the stability of sodium aluminate solution reduces, Al
2O
3The hydrolysising loss increase causes the rate of recovery to descend, and also may cause the subsider race of subsequent handling muddy when serious, and red mud separation and washing procedure can not normally be moved.Therefore, improve dissolution fluid α in the stripping index
kBe worth under the lower situation, can not allow aluminum oxide go because of hydrolysising loss comes back in the red mud, the reply technical process is suitably adjusted, so that the aluminum oxide of many strippings can reclaim smoothly, improves alumina producer output and economic benefit.
Summary of the invention:
The objective of the invention is to: adopt a kind of with seed precipitation solution adjustment dissolution fluid α
kThe method of value, the stability of increase sodium aluminate solution reduces the hydrolysising loss in dilution, stripping pit, the red mud separating, washing process, to improve alumina producer output, increases economic efficiency.
The present invention is achieved in that the part seed precipitation solution of quoting decomposition process returns dilution workshop section, together enters dilution trap with the stripping slurry and the red mud wash liquor that come from stripping final stage ore pulp flash-pot, is used to heighten dissolution fluid α
kValue; Dissolution fluid α
kBe controlled at 1.30~1.35, with diluent α
kValue heightens 1.44~1.52; Raw pulp join alkali α
kValue 1.30~1.35.
In above-described method, seed precipitation solution should carry out the seston recovery earlier before entering dilution trap, be sent to dilution trap again; The diluent α of small scale aluminum oxide factory
kOptimum value is 1.48~1.52, the diluent α of big alumina producer
kValue is 1.44~1.48.
Key point of the present invention is:
(1) seed precipitation solution with the small part decomposition process returns dilution workshop section, together advances dilution trap with dissolution fluid, red mud wash liquor, suitably heightens dissolution fluid α
kValue, the stability of raising dissolution fluid.
(2) owing to contain the aluminium hydroxide seston of 2~4g/l in the seed precipitation solution usually, this seston is easily caused the instability of sodium aluminate solution, so should use the seed precipitation solution after seston is reclaimed.For the big factory of the small scale aluminum oxide factory of not building the seston recovery process or newly-built no seston recovery process, answer auxiliary construction seston recovery process.
The α of seed precipitation solution in the production
kBe worth higher, usually between 2.75~3.2.This is worth low, little factory of big factory height.Employing divides seed precipitation solution in dilution operation addition portion, can improve dissolution fluid α effectively
kValue.Small scale aluminum oxide factory is because mass flow is less relatively, and the subsider temperature is lower than big factory, and the big factory of hydrolysising loss is serious, and to produce powdery aluminum, taking all factors into consideration can be with diluent α in addition
kValue heightens 1.48~1.52, and big factory is because of producing sandy alumina to seminal fluid α
kValue requires low, can be with diluent α
kValue heightens 1.44~1.48.
Owing to adopted seed precipitation solution later to adjust diluent α
kThe technical scheme of value, thus raw pulp join alkali α
kValue can continue to be reduced to 1.30~1.35, does not worry that hydrolysising loss and subsider run muddy problem, and dissolving device aluminum oxide production capacity can further improve again.
At present, domestic small scale aluminum oxide factory and newly-designed big factory all do not build the seston recovery process.In fact, the investment of building this operation is little, but can make the production capacity of aluminum oxide improve about 2%, and economic benefit is very obvious.Simultaneously, behind the construction seston recovery process, adjust diluent α to adopting seed precipitation solution of the present invention to return dilution workshop section
kThe helpful effect of process program of value.
The invention has the beneficial effects as follows: can increase the stability of sodium aluminate solution, reduce the hydrolysising loss in dilution, stripping pit, the red mud separating, washing process, improve alumina producer output, increase economic efficiency.