Pig iron smelting is the main production process of steel industry, the amount of its production water supply and waste water discharged is a big water consumer in the iron and steel industry. According to statistics, the national iron works Water consumption is 2.1 billion cubic meters, accounting for 22.5% of the water consumption of iron and steel enterprises, the cycling water using rate is 68.3%, treatment water quantity accounting for 12.7% of the iron and steel enterprises

Specific steelmaking plant wastewater

Indirect cooling water
　　
Indirect cooling water of warm air furnace of blast furnace, with the safe water supply equipment, recycling use can be achieved after cooling treatment. To consider the issues of water quality and stability, even if the solution is ideal, there is still a small part of the sewage water, this water can be dischared to other systems that can withstand it to be used further.

Direct cooling water
　
The direct cooling water of equipment or product, especially the cooling water of iron casting machine is seriously polluted, a large amounts of suspended solids are in the wastewater. These equipment and finished products required not high to the water quality, after a simple precipitation, the water can be recycled. Or discharged into the next working procedure which has Less demanding on water quality to use.

Production process water
　　
Washing water of blast furnace gas and slag flushing water，Because the water and the material contact with each other in direct，the water contains many harmful substances, must be carefully handled to realize the recycling use. These two wastewater is a typical wastewater in steelmaking plant, also the keys and difficulties of governance.

The quantity and quality of the waste water

All waste water of steelmaking plant , except for a very few losses, the waste water basically equal to the consumption water.
Many factors influence the water consumption, raw material, fuel situation, smelting operation conditions, the equipment structure, the setting condition of feed(water)pump, the quality and level of water supply, water treatment equipment and process and other conditions all have a great influence on the water consumption.

Steel plant wastewater treatment and chemical agent
　
Steelmaking products are collectively called steel. Steel is divided into ingot steel and casting steel water. Steel ingot is semi-finished products used for rolling steel ; The casting water is intermediate products used to cast a variety of steel castings.
Steel may have different classification methods. According to the quality the steel is divided into ordinary steel and high quality steel; By refining methods can be divided into open hearth steel, converter steel, and electric furnace steel three categories; The converter is divided into side-blown converter, pure oxygen top-blown converter and combined top and bottom blown converter steelmaking

The main wastewater in steel plant is the waste water purified by oxygen top-blown converter flue gas. Continuous casting water is only in small part of steelmaking plant. Time at home and abroad shows that, Steelmaking plant flue gas treatment generally adopt the efficient two-stage venturi scrubber, dust removal efficiency is more than 98%. For treating structures of suspended solids in the waste water, we used horizontal flow sedimentation tank in the past, now has been gradually changed into vertical sedimentation basin or radiation type sedimentation basin, natural precipitation replaced
by adding coagulant sedimentation, at the same time,  using dispersants to solve the problem of circulating water fouling,  to realize closed cycling. In this regard, China's Shanghai Baosteel Group Corporation has achieved good results.

The domestic treatment process of the dust removing water from oxygen top blown converters in steel plant，some adopt flocculation technology and magnetic processing method, the effect is also very significant. For example, in Beijing capital steel the suspended solids in the wastewater can be reduced to less than 50mg / L,likewise, scrubbing wastewater of converter fume recycling use don’t set up cooling tower in Shanghai Baosteel Group Corporation, TISCO, Shanghai Steel Works NO.1.they can maintain the normal production, Unaffected by temperature constraints, save infrastructure investment, occupy less site area, reduce the cost of wastewater treatment.
　　
The steelworks converter dust removal wastewater treatment should focus on the problem of solving the governance of the suspended solids, temperature balance and stabilization of water quality. In the choice of governance programs of converter dedusting wastewater, you should combine with the factors of converter process conditions, material condition, flue gas treatment and dust removal operation etc.

Through production practice we believe that, adding inorganic polymer flocculant of polymeric aluminum chloride, the Aluminum ions can compress the double electric layer on the suspended solid surface, due to the hydrolysis and the form of aluminum hydroxide, hydroxide itself easy to form velvet tablets, Polymer molecules are adsorbed on the surface of turbidity aluminum hydroxide molecules, and will make these cashmere particle forming large solid aggregates, it is the first phase of the agglutination.
　　
The second stage, when adding organic polymer flocculant PAM into polluted water, through a variety of bonding effect, the adsorption bridging action of the effective functional group on the ionic bonds and particulate, that is using the hydrogen bonds, and other ionic bond’s vander waals force of attraction to carry on the exchange-adsorption reaction, make it become a greater strong binding force floc. Large diameter and high concentration of colloid particles are beneficial for the bridging action, for this reason, Anionic Polyacrylamide can only be used as coagulant aids, should be used with  metal salts.

The main reason for using anionic polyacrylamide PAM separately and achieved good effect is, the divalent cations play a supporting role in the outcome sewage.