Seminar Report Ppt

UNDER :- BY :-

DR. ANUPAM BHATNAGAR H.O.D. MINING DEPT. HIMANSHU JAIN C.T.A.E FINAL YEAR MINING.

Waste Problems in Some MetallurgicalIndustries – Their Abatement And Control.

INTRODUCTION

• A lot of resources in the form of raw material,fuel, water etc. are invested in an industry to achieve a target product. But inturn, it does not get 100% of what it has invested.

• A considerable portion of valuable resources is lost as waste in industries.

• Treatment and disposal of this huge quantity of industrial waste is major problem to which the scientific world aware of.

• Effluents from some industries are greater contributors to environmental pollution.

• A lot of work is being done throughout the world to tackle this problem

RECOVERY FROM WASTE

• Waste generated by mining , mineral processing and metallurgical industries is estimated to be have 2-3 billion tons annualy.

• The waste include gases , dusts , solution and a variety of massive solid minerals such as tailings and slags , all of which must be disposed of with minimum environmental degradation.

• The resources potential of waste generated by iron and steel , aluminium , clay , phosphate , copper , coal mining and processing and non-metallic and secondary metal industries should be examined.

• Slags from ferrous and non-ferrous smelting operation are being utilised to some extent but still there is scope of wider use.

Waste problem in some metallurgical industries.i. Problem of coal carbonisation in steel

plants.

ii. Waste from steel mills and blast furnace.

iii. Metal finishing industries.

iv. Disposal of red mud.

Coal carbonisation in steel industries

• The production of coke by high temp. Carbonistaion is an integral part of steel plants.

• Water is used in different steps from quenching to scrubbing.

• The effluents discharged from bye-product coke plant consists of ammonia,phenol,cyanides,H2S, pyridines and oils.

• The effluents are both organic and inorganic type, some of them being toxic while others are non-toxic.

• Steel industries adopt abatement measures of waste pollution by recovering useful bye-products and reusing water.

• But still various natural water sources downstream these industries are heavily polluted by coke even effluents.

• Total volume of process effluent from a bye-product coke plant of 1 million ton capacity is about 80 m³ /hr.

Table below shows the sources and volume (m³/hr) of waste water from a steel plant.

Sr. No. Unit operation

Max quantity

Min quantity

Composition

1. Coke quenching

- Small Tar ,ammonia, H2S

2. Cooling &scrubbing

Flushing 4 1 Tar ,phenol

Primary cool

2 1 Tar ,ammonia

Potash plant

5 2 Cyanide,oils

Final cooler

1 - Phenols, oils

3. Ammoni steel

60 30 Fixed ammonia

4. Benzol plant

6 2 Wash oil, benzol

Tar distillation

30 - Tar,light oil, cresote.

Treatment of coke effluent

1. Coke of suitable quality is heated ,in absence of air ,to 1000 Ec for 12-18 hrs and then quenched in retorts. The gases from retorts are condensed. Tar and Ammonia liquor at 90 Ec is sent to bye-product by suction pump and recirculated in coke ovens.

2. Absorption of ammonia with refrigerated water or by scrubbing with dil H2SO4.

3. After final cooling of gas with high velocity water spray in a cooler,crude napthelene separated out.

4. Absorption of benzol is done by scrubbing with wash oil.

5. Removal of H2S from the gas by scrubbing with a dilute solution of NaOH.

6. Finaly the gas is compressed and stored in gas stacks.

Blast Furnace operating zones and coke behaviour

Steel mill waste1. Wet scrubber effluents :- originate from flue gases of

blast furnace. It contain iron oxide ,alumina, silica, carbon and magnesia. However ,the concentration of each varies with the type of ore used.

2. Waste picking liquor :-originating from cold rolling mills. It is highly acidic and contain 1-2% H2SO4 and FeSO4.

3. Waste from Hot Rolling Mill :- it contains ,mostly, of suspended matter derived from the descaling of ferric oxide from variousstages of operation.

4. Miscellaneous effluents :-

• Thermal power station – flyash, acidic and alkali or both chemicals for conditioning of water.

• Sintering process and other miscellaneous operations.

Methods of treatment and disposal

• Blast furnace effluent : removal of flue dust by plain sedimentation or conjunction with chemical coagulation. The sludge is disposed off by dumping.

• Effluent from cold rolling mills : treatment with lime for neutralisation. The only useful bye-product from liquor is FeSO4.

• From various operations in steel making are not of a polluting type and their treatment and disposal do not pose serious difficulty.

Effluents from metal finishing industries

With the rapid growth of industries , the need for applying attractive finishes has become a necessity as well as a reality. The phenomenal development of metal finishing industry has brought in its wake the problem of waste water disposal and consequent pollution of water resources.

Electroplating industry uses large quantity of water. The effluents are primarily of following types :-

1. Effluent containing acids or metallic salts.

2. Effluent contain impurities which are immiscible with water such as grease, oils, kerosene etc.

3. Cyanides from plating bahs for Cu, Zn, Brass,etc.

4. Chromates from chromebaths, etching baths,electro polishing.

Treatment of effluents

There are two types of process :-

1. Batch process :- for a smaller volume of liquid (greater than 500 lit/day). This process applicable to cyanide, chromic acid or acidic/alkaline type effluents.

2. Continuous proces :- for larger volume (5000 lit/day). The effluents are collected in small volume and treated continuously.

Disposal of Red MudRed Mud , the causic insoluble residue from bauxite processing

is largest volume solid waste from non-ferrous industries. Its disposal poses increasing problems of land costs, storage and environmental pollution.

Red Mud is a complex material containing of Fe2O3, Al2O3, Na2O and CaO as major constituents besides other mineral phases.

It is very fine sized with poor setting properties , thixotropic and cracks on drying.Red Mud can be commercially exploited for making bricks , contruction of dams , pavements etc.

In some studies it has been found that bricks made only Red Mud deteriorates rapidly with time. But when diluted with 10-15% ash, good quality bricks can be produced. This can be disposed off commercially as an additive to cement.

Health consequences• Skin contact - some chemicals like corrosive acids can

damage skin by single contact while others , like organic solvents, may cause damage by repeatedly exposure.

• Inhalation - Inhalation is the most common source of workplace exposure to chemicals and the most difficult to control. Air pollutants can directly damage respiratory tract or gets absorbed through lung and cause system/systemic effects.

Ingestion - Ground water and sub soil water contamination from leachates from refuse dumps and poorly managed landfill sites can result in ingestion of toxic chemicals by population groups who live far away from the factory sites and decades after the garbage has been dumped.

Conclusion

• Like other industries-some metallurgical industries too have their well established roles in polluting the environment, besides waste problems.

• The problem of enormous waste of resources in metal and mineral industries, treatment and disposal of effluents from pollution have proved to be of great concern to the scientists,engineers and technologists.

• Supply of waste is plentiful. Only what is needed is the formulation of economics and technical studies./feasibilities of recovering these resources and converting them into useful products.

SAVE EARTH

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