CO2 Reduction Potentials by Utilizing Waste Plastics in Steel Works

Abstract

Background, Aim and Scope. Feedstock recycling has received attention as an effective method to recycle waste plastics. However, estimating the reduction potential by LCA using coke oven and blast furnace in steel works has been a challenging task due to the complex structure of energy flow in steel works. Municipal waste plastics consist of several plastic resins. Previous studies have generally disregarded the composition of waste plastics, which varies significantly depending on the geographical area. If the reduction potentials by using each plastic resin in steel works can be quantified, the potential of municipal waste plastics (mixtures of plastic resins) can be estimated by summing up the potential of each resin multiplied by the composition of each resin in municipal waste plastics. Therefore, the goal of this study is to investigate the reduction potentials of CO 2 emissions by using individual plastic resins (PE, PP, PS, PET) and those for municipal waste plastics in the coke oven and blast furnace. Materials and Methods. A model was developed to clarify the energy flow in steel works. In order to estimate the changes in energy and material balance in coke ovens when waste plastics are charged, the equations to calculate the coke product yield, gas product yield, and oil product yields of each plastic resin were derived from previous studies. The Rist model was adopted to quantify the changes in the inputs and outputs when plastics were fed into a blast furnace. Then, a matrix calculation method was used to calculate the change in energy balance before and after plastics are fed into a coke oven. Results. It was confirmed that product yields of municipal waste plastics (mixtures of plastic resins) could be estimated by summing up the product yield of each plastic resin multiplied by the composition of each resin in municipal waste plastics. In both cases of coke oven and blast furnace feedstock recycling, the reduction potential of CO 2 emissions varies significantly depending on the plastic resins. For example, in the case of coke oven chemical feedstock recycling, the reduction potential of PS and PP is larger than that of PE. On the other hand, in the case of blast furnace feedstock recycling, PE has the largest CO 2 emissions reduction potential, whereas, the CO 2 emission reduction potential of PP is smaller than those of PE and PS. In both cases, PET has negative CO 2 emission reduction potentials, i.e., there is an increase of CO 2 emissions. In addition, the reduction potentials of CO 2 emissions are slightly different in each city. Discussions. The differences in the reduction potentials of CO 2 emissions by coke oven chemical feedstock recycling of each plastic resin is attributable to the differences in calorific values and coke product yields of each plastic resin. On the other hand, the difference in the CO 2 emission reduction potential for each plastic resin in blast furnace feedstock recycling is attributable to the difference in calorific values and the carbon and hydrogen content of e...

Assessment of midterm CO2 emissions reduction potential in the iron and steel industry: a case of Japan

“…IPPC (2011) reports 0.75 t-coke/t-plastic, without specifying the plastic type. Sekine et al (2009) reported 1.17 t-coke/t for polyethylene, 1.0 t-coke/t for polypropylene, 1.28 t-coke/t for polystyrene, and 0.57 t-coke/t for PET. Based on the above values, this study assumed a coke substitution rate of 1 t-coke/t-plastic.…”

Life cycle assessment of integrated recycling schemes for plastic containers and packaging with consideration of resin composition

“…4, which were obtained from modeling of the material recycling processes based on our field surveys and previous studies [2,24,25]. The amounts of recycled products and substituted products in coke oven chemical feedstock recycling and blast furnace feedstock recycling for each type of resin, obtained from the modeling of feedstock recycling processes based on previous studies [12,14,17], are shown in Tables 2 and 3, respectively. Power generation efficiency is assumed to be 20% for the energy recovery of household waste plastics in the I-0, I-1 and I-2 scenarios.…”

“…The Japan Plastic Containers and Packaging Recycling Association (2007) [14] also evaluated the environmental performance of the combination of material recycling and energy recovery of residue from the material recycling processes considering the resin composition of waste plastics in terms of calorific value. Sekine et al [17] investigated the potential reduction of CO 2 emission for feedstock recycling technologies in steel works for different types of plastic resin. Larsen et al [18] demonstrated the environmental and economic potentials of the recycling of household waste including plastic packaging wastes in a full-scale waste management system and compared various collection schemes; however, the recycling technology was assumed to be identical regardless of the collection scheme.…”

Plastics—Villain or Hero? Polymers and Recycled Polymers in Mineral and Metallurgical Processing—A Review

“…The coke product or the solid fraction yield depends on the volatile content in the polymers, decreasing with increasing volatile content in the polymers. Similarly, the gas yield decreases as the carbon content increases ( Table 4 and Table 5 ) [ 25 ]. Pyrolysis products of thermosets and their composites are given in Table 6 and Table 7 [ 26 ].…”