MINISTRY OF SCIENCE AND EDUCATION OF THE REPUBLIC OF KAZAKHSTAN SOUTH KAZAKHSTAN STATE UNIVERSITY named after M. AUEZOV Prepared by: Kassym A. M. Ch. T-14 -1 ka 1 Checked by: Yeskendirova M. M.
Plan: Conditions of sewage formation Clearing of such waters Recycling of sludge
Conditions of sewage formation The extractive way of phosphoric acid production consists in decomposition of natural phosphates by sulfuric acid and separation of formed firm phase – calcium sulfate – from phosphoric acid solution:
The phosphoric acid produced by this way has low concentration (25 -32 % of Р 2 О 5), therefore it is evaporated up to higher concentration. Depending on the process temperature and concentration of the phosphoric acid obtained the calcium sulfate formed can be separated as dihydrate Ca. SO 4 • 2 H 2 O (gypsum), half-hydrate Ca. SO 4 • 0, 5 H 2 O and anhydrite Ca. SO 4 (anhydrous salt). Depending on it three ways of wet-process phosphoric acid production are distinguished: dihydrate (Ca. SO 4 • 2 H 2 O), half-hydrate (Ca. SO 4 • 0, 5 H 2 O), anhydrite (Ca. SO 4) methods. The dihydrate way is the most widespread; it provides obtaining the phosphoric acid at 65 -800 С contained 25 -32% of Р 2 О 5.
The process of wet process phosphoric acid production by dehydrative method includes the following stages:
Treatment of such the waters is carried out by means of neutralization by limy milk with the subsequent coagulation of the deposit formed with help of polyacrylamide. As a result of the waste water treatment the sludge is formed, which contains fluorine and phosphorus compounds. Besides, circulating water flows are not completely consumed; therefore unbalanced flows arise, which demand additional purification before discharge in reservoirs. Fig. 4. 6 – A schematic diagram of a neutralization installation of fluorine-containing waste water by chalk: 1, 6 – bunkers; 2 – a conveyer; 3 – a storage of chalk; 4 – a clamshell crane; 5 – a collectorbalancing tank; 7 – a reactor; 8 – a fan
Recycling the sludge 1) from the point of view using valuable components containing in them; 2) 2) with the purpose of environmental protection from toxic fluorine and phosphorus compounds.
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