In Situ Catalytic Methanation of Real Steelworks Gases

The by-product gases from the blast furnace and converter of an integrated steelworks highly contribute to today’s global CO2 emissions. Therefore, the steel industry is working on solutions to utilise these gases as a carbon source for product synthesis in order to reduce the amount of CO2 that is released into the environment. One possibility is the conversion of CO2 and CO to synthetic natural gas through methanation. This process is currently extensively researched, as the synthetic natural gas can be directly utilised in the integrated steelworks again, substituting for natural gas. This work addresses the in situ methanation of real steelworks gases in a lab-scaled, three-stage reactor setup, whereby the by-product gases are directly bottled at an integrated steel plant during normal operation, and are not further treated, i.e., by a CO2 separation step. Therefore, high shares of nitrogen are present in the feed gas for the methanation. Furthermore, due to the catalyst poisons present in the only pre-cleaned steelworks gases, an additional gas-cleaning step based on CuO-coated activated carbon is implemented to prevent an instant catalyst deactivation. Results show that, with the filter included, the steady state methanation of real blast furnace and converter gases can be performed without any noticeable deactivation in the catalyst performance.

Concentration, Soil-To-Plant Transfer Factor Determination of Heavy Metals in Udu Area of Delta State, Nigeria

Heavy metals in varied concentrations are employed in the production of steel of different grades. Silver, cadmium, cobalt, chromium, and copper are of great importance in achieving this. They are part of the main ingredients in the production processes, which in most cases determines steel grades. The location of an integrated steel plant within Udu community of Delta State resulted in the pollution of the soil of the surrounding communities, most of which are involved in farming and fishing activities. This necessitated the transfer of these heavy metals from polluted soils into edible plants. These were mainly as a result of discharges of effluents, smoke and particulates from stack during production into the soils of the surrounding communities and finally into some edible plants; that are consumed by the communities as vegetables. Soil and leaf samples were collected from six different towns or communities in Udu. The towns are Ujevwu, Aladja, Ovwian, Ekete Inland, Orhuwhorun and Otor-Udu; and the heavy metals analysed are Ag, Cd, Co, Cr, Cu and Fe. These samples were digested using USEPA Method 3050B and the heavy metals were determined using atomic absorption spectrophotometer (AAS). Results obtained showed the following range for transfer factors (TF) in three different edible plants; which are pumpkin plant (Telfaira occidentalis), bitter leaf plant (Vernonia amygdalina) and scent leaf plant (Occinium gratissimum). The range of values obtained for the transfer factors are- Ag: 4.48–196.45; Cd: 44.52–212.79; Co: 0.03–0.46; Cr: 0.38–3.37; Cu: 21.76–102.95 and Fe: 2.85–14.40. For the six sample sites, generally, the values are in the order: Cd ˃ Ag ˃ Cu ˃ Fe ˃ Cr ˃ Co. Result interpretation shows some level of contamination when compared to recommended standard of these heavy metals in plants. The effect of which can be devastating in the future if not checked.

Enrichment of Integrated Steel Plant Process Gases with Implementation of Renewable Energy

The steel industry is one of the most important industry sectors, but also one of the largest greenhouse gas emitters. The process gases produced in an integrated steel plant, blast furnace gas (BFG), basic oxygen furnace gas (BOFG) and coke oven gas (COG), are due to high shares of inert gas (N2) in large part energy poor but also providing a potential carbon source (CO and CO2) for the catalytic hydrogenation to methane by integration of a Power-to-Gas (PtG) plant. Furthermore, by interconnecting a biomass gasification, an additional biogenic H2 source is provided. Three possible implementation scenarios for a PtG and a biomass gasification plant, including mass and energy balances were analysed. The scenarios stipulate a direct conversion of BFG and BOFG resulting in high shares of N2 in the feed gas of the methanation. Laboratory experimental tests have shown that the methanation of BFG and BOFG is technically possible without prior separation of CO2. The methane-rich product gas can be utilised in the steel plant and substitutes for natural gas. The implementation of these renewable energy sources results in a significant reduction of CO2 emissions between 0.81 and 4.6 Mio tCO2,eq/a. However, the scenarios are significantly limited in terms of available electrolysis plant size, renewable electricity and biomass.

Synergies of Cutting Air Pollutants and CO2 Emissions by the End-of-Pipe Treatment Facilities in a Typical Chinese Integrated Steel Plant

Reducing industrial emissions has become increasingly important, given China’s ongoing industrialization. In this study, the reduction in CO2 emissions and air pollutants due to end-of-pipe treatment in a typical integrated steel plant in China was assessed. The emissions were subdivided into sector levels, including main production and auxiliary departments. The synergies of reducing air pollutants and CO2 emissions using end-of-pipe treatment technologies were quantified, including direct and indirect effects. The results show that (1) using the carbon balance method is more suitable for the greenhouse gas (GHG) emissions of the steel plants in China at the enterprise and sector levels. The carbon-related parameters adopted in the carbon balance method strongly impact the accuracy of the emission calculation. (2) Compared with the direct synergistic CO2 emissions caused by chemical reactions, the indirect emissions due to the power consumption of the end-of-pipe facilities is more significant. (3) To achieve the control of local air pollutants and CO2 emissions, the negative effects of CO2 emissions caused by the end-of-pipe treatment technologies should be considered.