Parallel Between Rankine and Combined-Cycle Power Plants Configurations Burning Blast Furnace Gas

Abstract

The increasing fuel prices and stringent environmental legislation compel industries worldwide to pursue means to increase their processes efficiency. A higher efficiency relates to a reduction in fuel consumption, which results in a lower operational cost and emissions. When considering a steel mill, processes encountered in the blast furnace and in the coke oven, for example, generate gases that can be availed as low-grade fuels to return some sort of energy back to the process. This practice reduces the amount of high-grade fuel required and increases the global efficiency of the industrial site; however, demands higher investments and increase the management complexity. A thorough evaluation of such power cycles is important to assess their application. This paper is based on a currently operational combined-cycle power plant composed by two gas turbines that are adapted to use blast furnace gas as main fuel and one steam turbine with a total power rating of 490 MWe. This power plant configuration is compared to another one in which the topping cycle — composed by two gas turbines — is eliminated, and the same amount of blast furnace gas is burnt in a conventional steam generator, operating as a Rankine-cycle. The software Gate Cycle™ was used to model and simulate both cycles and provide the main parameters to analyze their performance. Parameters such as power rating, efficiency, emissions, and expected capital expenditure provided means to assess both options and evaluate their application. The combined-cycle provided higher efficiency and power rating when compared with the Rankine-cycle. However, the expected values for capital expenditure showed to be also higher. A major difference between both cycles is the higher flexibility of the combined-cycle power plant, which is essential to guarantee an electric energy source within the industrial site. As a counterpart, the operational complexity is significantly higher when compared with the Rankine-cycle. Overall, the present work provides valuable information to assess both solutions.

Stochastic Capacity Optimization of an Integrated BFGCC–MSHS–Wind–Solar Energy System for the Decarbonization of a Steelmaking Plant

“…Many studies have been conducted to improve the operating performance of BFGCCs. Campos et al [12] compared the operating performance of a BFGCC and the Rankine cycle. The results showed that the combined-cycle plant exhibited higher efficiency, rated power, and flexibility but with a higher cost and operational complexity.…”

Energy and Exergy Analysis on a Blast Furnace Gas-Driven Cascade Power Cycle

“…Campos [2] reported an exergy-based comparison between BFG-fueled combined cycle plants and steam cycle plant configurations, providing a method of direct combustion of blast furnace gas for power generation. Campos [3] compared the efficiency of combined cycle and Rankine cycle in BFG utilization, showing that the combined cycle has higher power generation efficiency. Ryzhkov [4] discussed the worldwide practice of operating combined cycle power plants on BFG to date, and the principles of upgrading a standard gas turbine power plant to a combustion BFG were studied.…”