DRI Plant

SCOPE OF DRI ASH SEPARATION PLANT:

Sponge Iron is iron ore reduced directly in solid state using coal gas, natural gas or coal as reductants and is also known as Directly Reduced Iron(DRI). The need for development and commercialization of sponge iron manufacturing process arose in late 50's when Electric Arc Furnaces (EAFs) engaged in manufacturing steel started facing problems of availability of scrap of desired quality, the traditional source of their iron metallics. The DRI process soon become popular and since the inception of first DRI plant in 1957 in Mexico, there has been continuous growth of this industry in last three decades. This is evident from the steep rise in world DRI production during the past three decades. India entered the sponge Iron industry only in 1980, when the coal based DRI plant of Sponge Iron India Limited (SIIL) was commissioned at Kothagudem, in Andhra Pradesh.

PRINCIPLE OF WORKING:

Every sponge Iron plant using coal as reductant in a rotary kiln creates a waste, which basically consists of coal char and other inorganic oxides.

This waste char, which is also sometimes called DRI ash, necessarily must have a minimum quantity of carbon in it in order to prevent re-oxidation of the freshly produced sponge iron at the discharge end of the rotary kiln. The carbon serves to maintain a reducing atmosphere till the end of the process.

The waste is separated from the product DRI using magnetic separation. The DRI is the saleable product and the ash/char is a waste product. In some plants, this waste is sold to local brick kilns for use in firing bricks (but only in the dry season).

Forsberg Agritech builds machines for air separation of solids and one such machine can be used to separate the carbon bearing char from the magnetic and non-magnetic oxide wastes.

The carbon bearing char has a fixed carbon content of between 40 and 50% and has useful fuel value. This can be gainfully employed in all boilers, which accept such fuel, such as fluidized bed boilers. It pays therefore to separate the char and utilize the fuel. (The waste could be used directly but will have lower calorific value and will make the fluidized bed heavy which can have adverse effect on the life of the pressure parts inside the fluidized bed boiler.) It also pays from the ecological point of view in that wastes are converted into useful fuel.

The separation is based on density and size differences and the separation is very easily accomplished with very few moving parts. This makes the system very cost effective.

The separated fuel can be used in the fluidized bed boiler replacing bought out fresh coal. This should lead to effective cost savings.

As the plant is not compatible with wet ash it is proposed that wetting in pug mill be eliminated and the dry material be fed to our plant through closed conveying system e.g. screw conveyor with an automatic bag filter system.

ADVANTAGES:

The calorific value of the segregated product will be significantly higher than that of the total DRI ASH, - which is being currently used. The recovered high calorific carbon will greatly reduce fuel requirement.

When the Ash content goes down and percentage of FC that goes in the boiler increases the wear and tear of all your combustion equipment will go down. One will be the best judge to estimate the saving that one may be able to achieve due to lower wear and tear of the equipment due to lower ash content.

A related saving will be the lower periodicity of the maintenance cycle due to lower ash content. Again it will vary from z place to place. One will immensely gain in down time. Shut downs are very expensive.

Even if 42 to 50 % available FC is collected and gainfully employed in all Boilers, it pays to separate the Char and use the fuel. In the bargain this reduces the disposable Ash and increase the calorific value of the fuel in the Boiler.

The waste, when used directly (as is being done presently) with less calorific value makes the fluidized bed heavy which can have adverse effect on the life of pressure parts inside the fluidized bed boiler.

It pays from the ecological point of view in that wastes are converted in to useful fuel.

When there is less ash % going in to the boiler, the size of the boiler required reduces and your total cost of boiler will comedown or production and productivity of existing boiler will increase.

To our estimate the payback period of such technology is very low.