Carbon and climate efficient use of biogenic carbons in solid waste for circular chemicals through gasification
Typ
Examensarbete för masterexamen
Master's Thesis
Master's Thesis
Program
Innovative and sustainable chemical engineering (MPISC), MSc
Publicerad
2024
Författare
Mola Mendoza, Marina
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
Municipal Solid Waste (MSW) generation is a growing global concern, aggravated
by rapid urbanization, population growth, and industrialization. Annually, approximately
2.1 billion metric tons of MSW are generated, with the trend expected
to rise. To address this urgent challenge, solutions must include both capacity increase
and MSW treatment sustainability, like converting the non-recyclable waste
into chemicals like methanol via gasification. This can potentially reduce the dependence
on fossil-based raw materials in the chemical industry, increasing the
circularity of the carbon in waste streams.
This study explores the feasibility of using gasification for chemical synthesis from
MSW, focusing on the Bubbling Fluidized Bed (BFB) gasifier. Moreover, it includes
the development of a comprehensive Aspen Plus model to simulate the
MSW-to-methanol process for a feedstock input of 100 MWth. It includes drying,
gasification, syngas cleaning, syngas conditioning, methanol synthesis loop, and
methanol purification stages. The auto-thermal gasification system is modelled
using steam as gasifying agent, with a steam-to-feedstock (S/F) ratio of 0.8, and
oxygen from an Air Separation Unit (ASU) to combust the volatile matter in the
feedstock.
In this model, the MSW input is converted into 16.31 tonnes/h of syngas in the
gasifier operating at 920 °C, requiring an oxygen flow of 2.12 kg/s from the ASU for
the volatiles combustion to sustain the autothermal operation. After the cleaning
stage, the syngas has an energy content of 15.31 MJ/kg on a LHV basis. Then,
the ratio of H2/CO in the syngas is adjusted to 2.5 via a Water Gas Shift reactor
before entering the chemical synthesis loop. In the medium pressure vapor phase
reactor, operating at 220 °C with a Cu/Zn/Al/Zr catalyst bed, the syngas is converted
into methanol. After distillation, 9500 kg/h of methanol is produced with a
molar purity of 99.3%. The overall process energy efficiency is 0.45 and the carbon
conversion efficiency is 0.41, meaning that 41% of the biogenic carbon in the MSW
is converted into the carbon contained in the methanol product.
The techno-economic analysis reveals promising financial indicators, including a
payback period of 5 years, a high NPV (276.28 M€), and a competitive levelized
cost of methanol of 414.92 €/tonne, suggesting that the proposed process can be
economically viable and competitive with current methanol production methods.
Beskrivning
Ämne/nyckelord
Municipal Solid Waste , Gasification , Bubbling Fluidized Bed , Syngas , Water Gas Shift , Methanol , technoeconomic analysis