Conversion of injected waste plastics in blast furnace

Samuelsson

2016

J. Sustain. Metall.

Plastic-containing shredder residue material has the potential to be used as an alternative reducing agent in nonferrous bath smelting processes. This would lead to not only decreased dependency on primary sources such as coal or coke but also to an increase in the efficiency of utilization of secondary sources. This calls for systematic scientific investigations, wherein these secondary sources are compared with primary sources with respect to devolatilization characteristics, combustion characteristics, reactivity, etc. As a first step, in this paper, devolatilization characteristics of plastic-containing shredder residue material (SRM) are compared to those of coal using thermogravimetric analysis. Proximate analysis has shown that SRM mainly decomposes by release of volatiles, while coal shows high fixed carbon content, which is reported to contribute to reduction reactions. To study the reduction potential of the evolved materials, composition of evolved off-gas was continuously monitored using quadrupole mass spectroscopy. The composition of volatiles shows H 2 , CO, and hydrocarbons which are known to have reduction potential. Therefore, it is essential that SRM would be used in a process that could utilize the evolved volatiles for reduction. Furthermore, to understand the potentials of different plastic materials as reducing agents, the devolatilization mechanisms and volatile composition of three common plastics, namely, polyethylene, polyurethane, and polyvinylchloride and their mixtures have been studied. The results show the interaction between the plastics within the binary and ternary mixtures. Similar phenomena may occur during devolatilization of SRM, which contains different type of plastics.

Section: Introductionmentioning

confidence: 99%

Alternative Reducing Agents in Metallurgical Processes: Devolatilization of Shredder Residue Materials

Lotfian

Samuelsson

2016

J. Sustain. Metall.

“…Blending with raw materials (composite agglomerates, coal blend for coke-making and fuel for sintering) [25]; • Direct use by injection through tuyeres [56].…”

Section: Waste Plastic Materialsmentioning

confidence: 99%

“…Top charging of plastic materials is practically impossible unless it is in form of CCA due to its chemical and physical properties. Therefore, all studies on introducing plastic to the BF are either through carbon composite agglomerates or injection through tuyeres [16,56,91].…”

Section: Plastic Materialsmentioning

confidence: 99%

“…Studies have shown that plastic particles have the capability to gasify completely in the raceway, which is known to improve the process efficiency and sustain the gas permeability along the BF cohesive zone. The reaction kinetics of waste plastic materials under the raceway, bird's nest and shaft conditions was studied by Babich et al [56]. They found that physical properties of plastic including grain size, shape, and porosity have strong effects on their reaction kinetics.…”

Section: Waste Plastics Injectionmentioning

confidence: 99%

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New Trends in the Application of Carbon-Bearing Materials in Blast Furnace Iron-Making

2018

Minerals

The iron and steel industry is still dependent on fossil coking coal. About 70% of the total steel production relies directly on fossil coal and coke inputs. Therefore, steel production contributes by ~7% of the global CO2 emission. The reduction of CO2 emission has been given highest priority by the iron- and steel-making sector due to the commitment of governments to mitigate CO2 emission according to Kyoto protocol. Utilization of auxiliary carbonaceous materials in the blast furnace and other iron-making technologies is one of the most efficient options to reduce the coke consumption and, consequently, the CO2 emission. The present review gives an insight of the trends in the applications of auxiliary carbon-bearing material in iron-making processes. Partial substitution of top charged coke by nut coke, lump charcoal, or carbon composite agglomerates were found to not only decrease the dependency on virgin fossil carbon, but also improve the blast furnace performance and increase the productivity. Partial or complete substitution of pulverized coal by waste plastics or renewable carbon-bearing materials like waste plastics or biomass help in mitigating the CO2 emission due to its high H2 content compared to fossil carbon. Injecting such reactive materials results in improved combustion and reduced coke consumption. Moreover, utilization of integrated steel plant fines and gases becomes necessary to achieve profitability to steel mill operation from both economic and environmental aspects. Recycling of such results in recovering the valuable components and thereby decrease the energy consumption and the need of landfills at the steel plants as well as reduce the consumption of virgin materials and reduce CO2 emission. On the other hand, developed technologies for iron-making rather than blast furnace opens a window and provide a good opportunity to utilize auxiliary carbon-bearing materials that are difficult to utilize in conventional blast furnace iron-making.

“…Plastic materials contain carbon and hydrogen, which makes them a possible alternative reducing agent [2]. Injection of plastic material in blast furnace has been reported in the literature and implemented in several industrial plants [2][3][4]. One limitation in using plastic-containing residue material for iron making is the content of metals such as zinc and copper which are not desirable in iron-making processes [5].…”

Section: Introductionmentioning

confidence: 99%

Alternative Reducing Agents in Metallurgical Processes: Gasification of Shredder Residue Material

Lotfian

El-Geassy

et al. 2016

J. Sustain. Metall.

Shredder residue material (SRM) contains plastic material, which has a potential to replace metallurgical coal for reduction during bath-smelting processes. Among the important parameters affecting its implementation are the gasification and the reactivity of char. Therefore, prior to considering its application in metallurgical processes, the gasification characteristics of the produced char need to be studied. Although the char produced from SRM contains lower fixed carbon compared with coal char, it has a porous structure and high surface area, which makes it highly reactive during gasification experiments. In addition to physiochemical properties, the catalytic effect of ash content of SRM char is attributed to its higher reactivity and lower activation energy compared with coal char. Furthermore, the effect of devolatilization heating rate on the gasification characteristics of produced char is investigated. It was found that the devolatilization heating rate during char production has a considerable effect on morphological properties of the char product. Moreover, the gasification reactivity of char produced at a fast devolatilization heating rate was the highest, due to the less crystalline structure of the produced char. Keywords Shredder residue material Á Char Á Gasification Á Reducing agent Á Bath smelting List of Symbols X Char conversion w 0 Initial weight of char w ? Saturation value of the weight-loss curve w(t) Sample weight at a time t r Gasification rate of the isothermal gasification q Gasification rate of the nonisothermal gasification E a Activation energy A Preexponential factor R S Reactivity index s 50 Time (in minute) required to reach the carbon conversion of 50 % w C Weight of carbon in the sample remaining unreacted at the time t The contributing editor for this article was Veena Sahajwalla.