Explain how would you proceed in designing a waste disposal system for a steel plant?

Answer 1

The world steel industry produces about 780 Mt of crude steel and simultaneously approximately 300 Mt of solid wastes products are also produced. Thus an average of about 400 Kg of solid by products is generated in the steel industry per tonne of crude steel. Major share of this (70-80%) consists of Blast Furnace Slag and basic Oxygen Furnace Slag. These wastes are an ecological hazard. The total steel production in India is about 25 million tones and the waste generated annually is around 8 million tones (considerably higher than the world average). Though the report has highlighted the associated ecological problems and suggested management, the main purpose of the report is to highlight the business opportunities available in utilization of the generated wastes into commercial products. Technologies have been developed in most the developed nations of the world for utilization of the generated wastes. and there are nations, which have total utilization of the wastes. In India though utilization of wastes have begun it is still quite some time before there is total utilization. The report has focused on the wastes generated - quality and quantity- by integrated steel plants, secondary steel sector and electric arc furnaces in India. Technologies developed for utilization of the generated wastes into useful products have been covered along with the technology sources, in India and abroad, and estimated project costs. The report has also presented a plan for zero waste programme

One of the major concerns of world steel industry is the disposal of wastes generated at various stages of processing. The global emphasis on stringent legislation for environmental protection has changed the scenario of waste dumping into waste management. Because of natural drive to be cost-effective, there is a growing trend of adopting such waste management measures as would convert wastes into wealth, thereby treating wastes as by-products. This has led to aiming at of zero-waste technologies. The technologies developed to economically convert wastes of steel plants into wealth provide new business opportunities for prospective entrepreneurs. Such technologies which have been identified in the report through adequate deliberations are indicated below in two categories, namely technologies for gainful utilisation of wastes in manufacture of conventional products and those for gainful conversion of wastes into altogether new products

Ecological problems and their management

The major solid wastes of steel plants that are dumped namely, BF sludge, spent refractories and fly ash, pose ecological problem and parallel initiatives are required for eco-friendly management of solid wastes. The following two ways have been identified and dealt with in this chapter for management of ecological problems.

* Plantation for green cover

* Plantation of flowering and tree species.

There are conflicting reports of effects of soil amended by fly ash on vegetables. Pending confirmation and reconfirmation of no harmful effects on vegetables, fly ash is prohibited in production of vegetables or food grains. Therefore, fly ash may be used for plantation of flowering plants and tree species'.

Practices and technologies of steel plant solid waste management.

Practices and technologies of steel plant solid waste management have been classified into three groups as follows.

Minimisation of wastes

Recycling of wastes

Reuse ( including sale to outside parties) of wastes

For minimisation of wastes, minimisation measures have been indicated. For recycling / reuse, the technologies have been briefly described with the name of the developing agency and the commercial status in this chapter. Cost data for implementation of the technologies could not be made available, because, normally, foreign parties reply only to queries about specific projects. It is suggested that research proposals may be made for the technology packages involved for indigenous through technology absorption and commercialisation, end then exemplary facilities based on cost-effective technologies may be set up for other entrepreneurs to follow suit. Problems and prospects of managing key by-products which are substantially dumped at present like steelmaking slag, BOF dust/sludge, fly ash and spent refractories have been dealt with at length.

Plan for zero waste programme

It is emphasised that all the industries, including the steel industry, are to be committed to 'sustainable '. Therefore, steel plants have no option but to plan immediately for a zero waste programme and implement the same. Aim of zero waste programme is make the total dumped quantity and so the individual waste quantities dumped to zero or near zero, or in other words, to produce 100% or almost 100% products. Wastes generated in all the model plants have been analysed and measures have been suggested to eliminate or minimize dumping.The chapter solicits initiatives from Govt. of India for creation of community cement plant to be built, owned and operated by a third party to take care of EAF slag's and community 2-stage Waelz kiln of adequate capacity to take care of zinc-rich EAF dust from a cluster of SSPs (EAF). To achieve the goal of zero waste programme on national basis as a part of 'sustainable ' initiative from Govt. of India is necessary to provide community ferruginous waste processing plants based on technologies like REDSMELT, FASTMET, ROMELT, Hamborn Shaft Furnace or process developed by RDCIS for utilisation of ferruginous wastes, to be built, owned and operated by third parties