Sustainable process for the co-generation of pig iron and electric energy using wood as fuel

Abstract

An integrated and sustainable process is presented for the co-generation of pig iron and electric energy in a blast furnace installation in which dried wood replaces charcoal as the fuel, as the reducing and as the carburizing agent. Furthermore, this application incorporates the process—until now independent—of transforming wood into coal, inside the blast furnace.

Description

[0001]This application claims priority from U.S. Provisional Patent Application No. 61 / 566,874, filed in the United States Patent and Trademark Office on Dec. 5, 2011, the entire disclosure of which is incorporated herein by reference.BACKGROUND OF THE INVENTION[0002]Pig iron is an alloy of Iron and Carbon that is used as raw material for the production of steel. Selected species of wood are transformed into pieces of uniform and predetermined size such as chips (but not only this shape) that are dried to less than 10% Moisture Content and classified by size in a wood drying and classifying line so that only dry coarse particles are charged into the blast furnace. The large amount of water evaporated in the wood drying process may be recycled to reduce the amount of fresh water used in the process. The dry wood is heated inside the furnace with hot spent gas in order to initiate the exothermic carbonization process. The greater weight of wood in the charge, that is required to compe...

AI Technical Summary

Benefits of technology

The patent describes a method of using biomass in a blast furnace to increase its flammability and heating value. The biomass is dried and then pulverized with coal. The pulverized powder is blown from a tuyere as an auxiliary reducing material in the blast furnace. The method also recovers energy from the burnt wood volatiles and converts it into electric energy. This thermal energy is used to heat the furnace and create a hot gas loop to optimize the carbonization process. The main technical effect of the patent is to provide an efficient and cost-effective method for using biomass in a blast furnace.

Problems solved by technology

This energy, as well as many volatiles and fine charcoal particles that are pollutants, are normally vented and thus lost into the atmosphere.

Comment—though this patent mentions the use of a biomass material in contact with the iron ore, it does not establish such biomass material as being the only energy source, the only reduction source, and the only carburizing agent.

Furthermore, it does not consider substantial energy co-production, and it considers plastic resinous materials as one of the reactants, which we don't.

Furthermore, it does not consider a surplus energy production of a previous drying of the wood.

Furthermore, it does not consider cogeneration.

The second process is the Electric Arc Furnace (EAF) that produces steel in one step by melting recycled steel scrap and consumes great amounts of energy per ton of steel produced.

Although steel is considered an essential product for humanity, its production causes a series of environmental problems such as carbon dioxide emissions as well as ground, water and atmospheric pollution.

High energy consumption and a need to improve material efficiency are also important issues that confront the steel industry.

Continuous efforts are spent in attempting to solve these major problems around the world but an effective and efficient solution has not been found.

The charcoal production process generates CO and CO2 gas that, together with the fine particles that are lost to the ground and to the atmosphere produce air and water pollution.

Charcoal storage at the charcoal production facility, transportation to the blast furnace, storage and handling at the blast furnace plant create a serious ground and atmospheric pollution problem that eventually may contaminate the water.

Exposure to rain degrades the quality of charcoal as a fuel and wind promotes atmospheric and ground contamination of fine charcoal particles.

In addition, the heat energy generated in the charcoal production process is normally lost to the atmosphere because most producers do not recover it.

Charcoal pieces tend to be fragile and may collapse due to erosion and to the weight of the charge above them during the descending movement.

This creates fine particles that may reduce the permeability of the charge and eventually are blown out of the furnace before they are burned, lowering the material yield of the process and increasing pollution.

All the energy and the water contained in the wood are lost creating a serious contamination and efficiency problem.

A batch process produces a charcoal of non-uniform size and quality and with a significant process loss because all wood pieces do not have a similar heat treating history.

In addition, part of the wood is burned in order to generate the heat required for the carbonization process thus reducing the wood-to-carbon yield.

But, since wood has a bulk density that is approximately twice that of charcoal, the wood charge will occupy a volume twice the volume of the charcoal charge, thus diminishing the working volume of the furnace in that amount.

Images