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CPOTE2020 logo
6th International Conference on
Contemporary Problems of Thermal Engineering
Online | 21-24 September 2020

Abstract CPOTE2020-1151-A

Book of abstracts draft
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A novel concept of negative CO2 emission power plant for utilization of sewage sludge

Paweł ZIÓŁKOWSKI, Gdańsk University of Technology, Poland
Janusz BADUR, Institute of Fluid-Flow Machinery Polish Academy of Sciences, Poland
Halina PAWLAK-KRUCZEK, Wrocław University of Science and Technology, Poland
Łukasz NIEDŹWIECKI, Wroclaw University of Science and Technology, Poland
Mateusz KOWAL, Wroclaw University of Science and Technology, Poland
Krystian KROCHMALNY, Wroclaw University of Science and Technology, Poland

Carbon Capture and Storage (CSS) technology is considered an important “bridge technology”, allowing effective abatement of CO2 emissions for power units using fossil fuels. However, if biomass is used in a power plant, equipped with CCS system, negative CO2 emissions can be achieved. In practice, wide development of such technologies would enable not only reduction of CO2 emissions, but also reversal of the harm done so far. In the long term, wide application of technologies with carbon-negative emissions could allow coming back to pre-industrial concentrations of CO2 in the atmosphere. Sewage sludge is a residue of the wastewater processing, that is a biologically active and consists of water, organic matter, including dead and alive pathogens, as well as organic and inorganic contaminants such as polycyclic aromatic hydrocarbons (PAHs) and heavy metals. Due to the nature of sewage sludge and its possible influence on human health and wellbeing, it is a subject of various regulations. Currently, sewage sludge is considered a biomass, according to the new Polish act on renewable energy sources from 20th of February 2015 and its novel version from 19th of July 2019. This study presents a novel approach, that aims at assessing feasibility of the concept of a negative CO2 emission power plant, based on steam gasification of sewage sludge, subsequent combustion of the producer gas in a gas turbine with spray-ejector condenser. This novel solution offers an efficient way to convert the chemical energy in the sewage sludge and, in the same time, compress and capture CO2. Possibility to utilize sewage sludge is an additional advantage of the proposed solution. For the gas from steam gasification of sewage sludge, with following mass shares of main compounds YCO=0.133; YCO2=0.593; YCH4=0.117; YCnHm=0.08; YH2=0.051 and heating value of nearly 16.5 MJ/kg, it is possible to achieve negative CO2 emissions. In this paper, thermodynamic model of this novel type power plant made using CFM code is presented. The study shows complete mass and energy balance of such installation, based on the experimental results of steam gasification in an allothermal fixed bed gasifier.

Keywords: Sewage sludge, Steam gasification, CO2 negative power plant, Thermodynamic analysis, Spray ejector condenser