Process Modelling and Simulation of Waste Gasification-Based Flexible Polygeneration Facilities for Power, Heat and Biofuels Production

Synergistic blending of biomass, sewage sludge, and coal for enhanced bioenergy production: Exploring residue combinations and optimizing thermal conversion parameters

Creating renewable energy from lignocellulosic biomass is essential for a sustainable future. Due to their abundance and the possibility of producing cheap and clean energy, non-lignocellulosic wastes like sewage sludge from industrial and municipal wastes have drawn attention as a feasible alternative to fossil fuels. These abundant, cost-effective resources may help minimize the effects of climate change since they produce less pollution. Several drawbacks are associated with using sewage sludge in thermal conversion procedures. These issues encompass suboptimal energy yield, elevated ash levels in the final product, and subpar biomass quality. Using these scraps in conjunction with coal might enhance energy conversion processes. This study has revealed the necessity for further investigation into how various combinations of residues interact with each other, influencing synergistic effects and degradation processes. The study's underlying objective was to provide a centralized database on the synergistic effects of mixing biomass and sewage sludge for bioenergy production, coal and biomass, and coal and sewage sludge through thermochemical processes like combustion, pyrolysis, gasification, and hydrolysis with Aspen Plus. This study will assist in enhancing biofuels' output from sewage sludge, coal, and coal/biomass blends in thermal conversion by defining the operating parameters (temperature, heat, and residence duration) of pyrolysis and combustion, features, and chemical properties that may influence these processes.

Modeling and simulation of Khat waste fast pyrolysis for energy recovery

Bioenergy is now recognized to be capable of providing the vast majority of predicted future renewable energy supply. Biomass is currently considered a common and commonly used renewable energy source. This study depends upon the investigation of khat waste using Aspen Plus software, which is required for creating environmentally friendly energy sources capable of improving our access to energy and economic sustainability. The outcome of the study is to understand the characteristics of the pyrolysis process without conducting a time-consuming, expensive, and complex procedure. The results of the investigation will be useful in determining the best feedstock for the formation of biofuel. Aspen Plus software simulates several ash-free organic components, including carbon, oxygen, nitrogen, hydrogen, and sulfur, with results like 45.72 % for carbon, 5.84 % for hydrogen, 0.43 % for nitrogen, and 38.56 % for oxygen. The production of biofuel is affected by processing parameters such as temperature and total mass flow rate. During reactions with the same mass but different temperatures, the bio-oil declined from 600 °C to 800 °C, while the maximum gas emission climbed quickly and the biochar reduced. In addition, it was recovered from Khat waste and proved to have an energy efficiency of 80.75 % and a net energy capacity of 134.25 kW. In addition, the High heating value (HHV) can be obtained from Khat waste is 19.38 MJ/kg, and low heating (LHV) can be 18.12 MJ/kg. We have been able to realize it using the Institute of Gas Technology formula based on ultimate analysis. The results show that Khat produces more oil than other wastes. As a result, all Khat waste is naturally occurring and Khat waste usually contains less nitrogen and no sulfur when used as fuel, which is an air pollutant reducing and protecting the environment.

Efficient removal of tar employing dolomite catalyst in gasification: Challenges and opportunities

Fossil fuels are currently the dominant source of electricity and energy production around the world. Biomass is one of the most referred renewable carbonaceous resource(s) that can be employed for the waste-to-energy concept. Syngas obtained from biomass gasification can be utilized for a variety of key industrial purposes, including internal gasification engine operation, power generation, and hydrocarbon compound production using the Fisher-Tropsch technique. However, the existence of impurities such as hydrogen sulfide, tar, and particulate matter along with other undesirable chemicals present in syngas are major disadvantages of biomass gasification. Tar is the most difficult among all the pollutants to be removed from syngas; it also causes serious problems in downstream syngas applications. For decades, studies have been performed with various catalysts to remove the tar. Dolomite has shown positive response for tar elimination and hydrogen-enriched gas production. Several studies have been carried out on dolomite for eliminating the tar from syngas. This review encompasses sources of solid waste, the mechanism of catalysis, and in-situ and ex-situ usage of dolomite in the gasification process. It addresses the key issues such as fragmentation and attrition, elutriation, and coke formation along with dolomite's usefulness in amalgamation with other catalysts, environmental consequences, and economic viability of dolomite applications. It also discusses the challenges and opportunities for tar removal using catalysts, with a specific focus on dolomite along with economic and environmental sustainability considerations.

Multi-Criteria Selection of Waste-to-Energy Technologies for Slum/Informal Settlements Using the PROMETHEE Technique: A Case Study of the Greater Karu Urban Area in Nigeria

Slum/informal settlements are an integral part of a city, with a population projected to reach 3 billion by 2030. It is also expected that the rate of waste generation will more than triple by 2050 in the cities of low-income countries of sub-Saharan Africa. At this rate, the risk to the environment and health of inhabitants are enormous, because the current waste management practices are not guided by legislation on proper use and disposal. This paper proposes the conversion of waste to energy as a solution to this problem. The aim of this study is to apply the PROMETHEE technique with a combination weighting method to obtain the most appropriate waste-to-energy technology for the slum/informal settlements of the Greater Karu Urban area in Nigeria. The findings reveal that the gasification technology outperformed the other technologies, and the affordability of electricity supply from this technology was determined by a general survey conducted on the slum/informal settlements.

Decarbonizing Vehicle Transportation with Hydrogen from Biomass Gasification: An Assessment in the Nigerian Urban Environment

Tailpipe emissions from vehicles consist of CO2 and other greenhouse gases, which contribute immensely to the rise in global temperatures. Green hydrogen produced from the gasification of biomass can reduce the amount of CO2 emissions to zero. This study aims to provide a modelling framework to optimize the production of hydrogen from biomass waste obtained from different cities, for use in the road transport sector in Nigeria. A gasification model with post-treatment shift conversion and CO2 removal by adsorption is proposed. In this study, six cities are simulated based on technical and environmental considerations, using the Aspen Plus software package. The results revealed that Kaduna has the highest hydrogen generation potential of 0.148 million metric tons per year, which could reduce CO2 emissions to 1.60 and 1.524 million metric tons by the displacement of an equivalent volume of gasoline and diesel. This amounts to cost savings of NGN 116 and 161.8 billion for gasoline and diesel, respectively. In addition, the results of the sensitivity analysis revealed that the steam-to-biomass ratio and the temperature of gasification are positively correlated with the amount of avoided CO2 emissions, while the equivalence ratio shows a negative correlation.

Study of Energy Valorization of Disposable Masks via Thermochemical Processes: Devolatilization Tests and Simulation Approach

The COVID-19 pandemic exacerbated the use of medical protective equipment, including face masks, to protect the individual from the virus. This work studies the feasibility of using these materials as fuel for thermochemical processes for the production of syngas. A preliminary physic-chemical characterization was made by means of moisture and ash determination, thermogravimetric analysis, X-ray fluorescence. Afterward, pyrolysis and gasification tests were executed in a laboratory-scale fluidized bed reactor with chirurgical and FFP2 masks investigating four temperature levels and three different operating conditions (fluidizing agents and dry/wet sample). A qualitative and quantitative analysis of condensable aromatic hydrocarbons in the produced gas, collected during the test campaign, was performed employing a gas chromatograph-mass spectrometer. The experimental data from the tests were used to propose a hybrid approach to simulate the gasification process, based on experimental laws for the devolatilization step and a thermodynamic equilibrium approach for char gasification. The resulting data were compared with a thermodynamic equilibrium model, showing that the new approach captures non-equilibrium effects always present in real gasifiers operation.

Syngas Composition: Gasification of Wood Pellet with Water Steam through a Reactor with Continuous Biomass Feed System

Investigations were performed in relation to the thermal gasification of wood granulate using steam in an allothermal reactor with electric heaters. They studied the impact of the temperature inside the reactor and the steam flow rate on the percentage shares of H2, CH4, CO, and CO2 in synthesis gas and on the calorific value of syngas. The tests were conducted at temperatures inside the reactor equal to 750, 800, and 850 °C and with a steam flow rate equal to 10.0, 15.0, and 20.0 kg∙h−1. The intensity of gasified biomass was 20 kg∙h−1. A significant impact of the temperature on the percentages of all the components of synthesis gas and a significant impact of the steam flow rate on the content of hydrogen and carbon dioxide in syngas were found. The highest percentage of hydrogen obtained was 43.3%. The calorific value of the gas depended significantly on the temperature inside the reactor and the correlation between the temperature and the steam flow rate. Its maximum value was 13.3 MJ∙m−3 at 800 °C. This paper also includes an assessment of the mutual correlations of the percentage shares of the individual synthesis gas components.