Deep Decarbonization in the Pulp Industry - Carbon Dioxide Recycling and Utilization in a Lime Kiln via Methanation

In most pulp mills lime kilns are the only source of fossil carbon dioxide emissions. Natural gas is a widely used fossil fuel for combustion in lime kilns. For deep decarbonization of the pulp mill, fossil fuels have to be substituted by alternative low carbon fuels. Besides biomass-based approaches, the utilization of hydrogen (H2) can be a possible option. This paper presents a study on an exemplary lime kiln with a natural gas demand of 50 MWth. Starting with the a base case, 3 scenarios are developed for an alternative fuel supply to the lime kiln. The utilization of hydrogen is considered as the main alternative. One downstream option for the flue gases is the separation of CO2 and the conversion of CO2 and H2 to synthetic natural gas (SNG) which can partially be used in the lime kiln and partially be sold to the grid. The cases were simulated in a chemical engineering software to calculate mass and energy balances. Based on the data, the processes are assessed especially in terms of CO2 emissions. Results show that the CO2 emissions can be reduced by the utilization of hydrogen. In cases of SNG production, the heat for carbon capture can be supplied by the excess heat from the SNG process. The investigated concepts can also be transferred to the cement industry since processes are very similar.      «

In most pulp mills lime kilns are the only source of fossil carbon dioxide emissions. Natural gas is a widely used fossil fuel for combustion in lime kilns. For deep decarbonization of the pulp mill, fossil fuels have to be substituted by alternative low carbon fuels. Besides biomass-based approaches, the utilization of hydrogen (H2) can be a possible option. This paper presents a study on an exemplary lime kiln with a natural gas demand of 50 MWth. Starting with the a base case, 3 scenarios are...     »