Sewage treatment

The charge of water on 1 t of sulfuric acid makes 40-60 m³/t, however its basic quantity is spent for cooling of acid, while technological water makes about 1,5 m³/t. The basic quantity of sour drains is formed due to leakage and spread of acid in shop of wet clearing of gases, in absorption and drying bays and during of cooling of acid.

The most rational decision for neutralization of these drains is their neutralization by lime or soda with the subsequent water recirculation and removal of precipitates. The basic stage of process - neutralization of drains by lime up to рН=6:

CaO + H₂O + H₂SO₄ = CaSO4 + 2H₂O (15)

Fig. 4.9 – The scheme of cleaning of departing gases of sulphuric acid production from SO₂ by ammoniac way: 1 – absorption column; 2 – spray catcher; 3 – electrostatic precipitator; 4 – collectors; 5 – regeneration tower; 6 – blowing tower

In this case there is the sedimentation of ion SO₄^2- as calcium sulphate. After clarification and cooling water is given in the general sewer system or on recirculation.

One of ways of decision of a problem of drains is a replacement of water cooling of sulfuric acid on air cooling that would lead to significant reduction of water consumption in production of H₂SO₄.

Control questions on the topic “Waste products of manufacture of sulphuric acid. Methods of clearing, processing and neutralization of firm waste products, sulphurous anhydride and sewage of manufacture.”

1. Which raw material in sulfuric acid production is used?

2. Which ways of sulfuric acid production you know?

3. Which way of sulfuric acid production is the most widespread now?

4. Call the basic stages of contact-process sulphuric acid production.

5. Explain the scheme of contact sulphuric acid production from pyrite.

6. Explain the scheme of contact sulphuric acid production from natural sulfur.

7. Call the basic waste products of H₂SO₄ manufacture.

8. Which useful compounds the pyrite cinder contains?

9. Call the most rational way of cinder processing.

10. Explain the sequence of stages of cinder processing at low temperature chloridizing roasting.

11. Which metals can allocate from cinder?

12. What other ways of cinder processing you know?

13. The way of selenium sludge recycling.

14. Which chemical and physico-chemical methods of SO₂ extraction from departing gases are used?

15. In sulphuric acid production two processes of SO₂ recycling are most widely used. Call them.

16. Explain the method of double-contact at departing gases cleaning from sulfur dioxide.

17. Which physico-chemical phenomenon in method of double-contact is used?

18. Call the basic advantages and lacks of double-contact method.

19. Which stages the ammoniac way of gas clearing from sulfur dioxide includes?

20. Call the basic advantages and lacks of ammoniac way of gas clearing from sulfur dioxide.

21. On which stages of sulfur acid production sewage is formed?

22. How sewage of sulfur acid production is cleared?