Techno-Economic Assessment of Carbon Capture for Integrated Steel Mills in Canada

Abstract

Globally and within Canada, steel production accounts for 10% and 23% of total industrial CO2-eq emissions, respectively. This is primarily owed to the prevalence of the traditional blast furnace-based integrated steel mill, responsible for 73% of steel production globally. This thesis investigates the techno-economic feasibility of carbon capture methods within a Canadian integrated steel mill, focusing on reducing the direct emission intensity of hot rolled steel slabs till non-emitting steel production methods can be employed. The study emphasizes two post-combustion capture techniques: First, Monoethanolamine (MEA) absorption identified as the primary technology due to its maturity and cost efficiency. Second, hybrid methods combining vacuum pressure swing adsorption with low-temperature purification (VPSA-LTP) are explored for their commercial potential and lower thermal energy penalty relative to the chemical absorption base case.

A systematic framework involving performance modelling using Aspen Plus and Aspen Adsorption, and cost assessment evaluates energy consumption, cost implications, and environmental benefits of both carbon capture methods. The opportunity for waste heat recovery for the steel production process was also evaluated. A surrogate-based optimization framework was developed and proven to be a tool for conducting a less-computationally intensive techno-economic assessment of batch separation processes.

Key findings highlight that the lowest capture cost of $75 per tonne of CO2 captured ($86 per tonne of CO2 avoided) is achieved using a single-point of capture: the central power station, due to its volume and high CO2 composition. To achieve this minimum cost alongside its’ lowest achievable steel emission intensity, this carbon capture implementation includes MEA absorption with an oxy-combustion boiler and waste heat recovery from flared gas and flue gases to offset energy demand. In the case of natural gas supply constraints and overall reliance on electricity, using a hybrid VPSA-LTP process offers the lowest electricity consumption at a cost of $120 per tonne of CO2 avoided. Overall, carbon capture can be used to reduce the emission intensity to 0.76 tonnes of CO₂ per tonne of hot rolled steel slabs while increasing the production cost by 17% to $741 per tonne of steel.

It is recommended that advanced solvents and sorbent be explored to further reduce the energy penalty and increase the productivity of their respective methods. There must also be evaluation of alternative decarbonization schemes for further emission reduction and the potential of heat integration with the existing power station to generate more steam in lieu of electricity. There must also be a multi-disciplinary assessment of the impact of policies on the viability of carbon capture as a decarbonization solution for the steel industry.