Date of Award
Master of Science (MS)
The main objective of this work was to develop a waste truck tires recycling facility for the Siberian coal transportation company “SibTreid NK” in the Kemerovo region, Russia. For years, the company has been stockpiling old scrap tires at their warehouse or dumping them into open strip mines. Taking this into account as well as existing environmental concerns due to the continually growing coal industry in the Kemerovo region, it is highly necessary to make an operational facility to deal with the large number of accumulated waste truck tires.
To achieve this goal, this project reviewed different methods and technologies for managing scrap tires, investigated economic feasibility for the most attractive options, and provided a list of recommendations for the company.
The current practices that “SibTreid NK” uses are dumping, landfilling, and retreading. To address the first part of the research, the strengths and weaknesses of the following scrap tire management techniques have been analyzed: grinding, thermochemical conversion processes that involve incineration, hydrothermal liquefaction, gasification, and pyrolysis, as well as existing methods.
Taking into account interests of the company in converting waste truck tires into oil, gas, and solids, the work is primarily focused on thermochemical processes such as pyrolysis. In total five scenarios of the pyrolytic process are considered in the study. For each scenario I developed the flowchart diagrams. These flowcharts show the following characteristics at each stage of the recycling practices: the feedstock flow within the company, associated expenses, and relevant emissions.
In order to determine the size of the future facility, necessary equipment, quantity of each by-product, and to evaluate the operating costs of the project, I analyzed the most typical size of a recycling facility used in literature. According to various literature sources, the most appropriate size of the future facility is 30 ton/day.
As input data to the process, I used the average composition of worn out truck tires. In this case use of averages for data is acceptable for several reasons. First, for study purpose ±30% accuracy is admissible. Second, it helps to avoid over-complication of the model to keep the project feasible. The final reason is the inability to obtain the data about the composition of a particular model truck tire by a particular brand, as this information is protected by the tire companies. Also, in articles dedicated to tire recycling, authors usually mention proximate and ultimate analysis of raw material, but almost never talk about whether they used a truck or a car tire or what brand. As the result the raw material was chosen to have steel concentration of 20%. The distribution of the byproducts on steel-free bases is adopted from the research dedicated to the pyrolysis of truck tires and equals 35.5% for the char, 12.5% for the gas, and 52% for the liquid fraction.
The next step of my research was to investigate the viability of the project. Economic analysis of all five scenarios for using the pyrolysis technology has performed, including conversion of low-value waste tires to high-value chemicals, tire derived oil, with and without pre-treatment of the initial feedstock. Using the minimum possible lifetime of the chemical facility (10 years) and current economic indexes of Russia, such as revenue tax, the exchange value of the ruble, fixed operating labor costs per year, I developed a program to calculate the internal rate of return (IRR), payback period (PBP), and net present value (NPV) of the project. The result showed that the most economically attractive option was the base case scenario option that considered the pre-treatment of the raw material, pyrolysis process itself, and the separation of the tire-derived oil. The NPV was 10.39 MM$, the payback period was about 3.6 years, and IRR was 31.5%. Then I conducted the sensitivity analysis for the base case scenario. It showed that the process is extremely sensitive to the fluctuation of the limonene yield and limonene price.
This study could be used by the company to produce extra revenue from selling pyrolytic by-products like steel, char, tire-derived oil, steam, and high-value chemicals. Variable costs of the company, such as fuel expenses, can also be decreased. The results of this work will help to mitigate a series of environmental problems caused by dumping and stockpiling in my region and decrease the number of emissions that otherwise would be emitted during the production of steel, char, oil, and valuable chemicals if waste truck tires were not recycled. Reduction of total emission will contribute to the obligation of the Russian Federation to address climate change and, ultimately, will have a positive impact on humans’ health in the Kemerovo region.
Tsiryapkina, Irina, "Technology And Economy Analysis Of Waste Truck Tires Management" (2019). Theses and Dissertations. 2489.