Page 51 - Impiantistica industriale

The case study here analyzed to 28 [11]; the resulting value is in order of 0.44 tonCO /
based on circular hydrogen ton H . 2
2
“production from waste, resulted C4=Equivalent CO emissions to replace electric ener-
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gy no more produced from waste incinerator. Resulting
in a feasible solution from amount of equivalent CO is in order of 2.5 tonCO /ton
2
2
technical, economic and H2 on the basis of a grid electric emissions factor of 0.245
environmental point of view kgCO /kWhe.
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C5=Indirect CO emissions for electric energy absorbed
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along the process take into account also O2 production;
thesis of a chemical in this case hydrogen. It derives that resulting value is in order of 1.9 ton CO /ton H2 according
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such system compared with conventional routes of waste to a grid emission factor of 0.245 kgCO /kWhe.
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disposal represented by incinerator and chemical synthe- C6=Equivalent CO emissions derived from transport of
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sis from fossil feedstock, allows for a better exploitation of Waste from production facility assuming a distance be-
carbon and at the end for a saving in terms of CO emis- tween gasifier and waste facility of around 100 km. result-
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sions. The proper estimate the CO saving of the waste ing specific consumption is 0.10 ton CO /ton H2.
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to chemical approach, the following formulation has been Taking into account the above contributions, the overall
adopted: CO emission for the waste to hydrogen plant is in order
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of 23.3 ton CO /ton H .
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2
The overall saving achieved by the waste to Hydrogen
plant, according to a simplified LCA analysis, is in order of
90% corresponding to around 202.000 tCO /anno.
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Emissions from conventional hydrogen
production
The estimation of CO emission for conventional hydro- Conclusions
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gen production, takes into consideration that equivalent Waste like RDF, Municipal Solid Waste and waste plas-
emission for feed and fuel consumption is around 75% of tics, once properly converted into syngas, may be used
the overall LCA emission [12]. An average feed & fuel con- as feedstock for the synthesis of wide range of chemicals.
sumption for conventional hydrogen plant equal to 3500 This approach fulfills the hierarchy of waste management
kcal/Nm H has been assumed. The resulting specific being addressed to waste which is no more recyclable
3
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emission for the above-mentioned assumption is around and normally routed to incinerator or landfill. The key step
12.6 tonCO /ton H . allowing a reasonable use of waste as alternative feed-
2 2
stock, is the primary conversion step based on a high
Emissions from incinerator temperature gasification carried out under pure oxygen
For the incinerator it is adopted the reference value of environment and with a temperature profile assuring cer-
around 2tonCO /tonWaste. Assuming the distance from tain characteristics for produced syngas.
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nearest incinerator equal to 1000km as experienced by The case study here analyzed based on circular hydro-
many countries obliged to export waste along long dis- gen production from waste, resulted in a feasible solution
tance due to unavailability of dedicated waste facilities, from technical, economic and environmental point of view.
the overall emission is in order of 2.1 tonCO /tonWaste Competitive cost of production may be achieved under
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equal to 22.5 ton CO /ton H . gate fee in order of 130-150€/ton, which is the average
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To proper account for the equivalent CO emission de- cost for the disposal of such fractions of waste in Italy.
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riving from electric power no more produced from waste The simplified LCA analysis performed around the waste
and needed to be replaced from the grid, it is assumed to hydrogen scheme, performs high CO saving once
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an electric energy efficiency of 28%. It derives that 24 t/h compared with conventional steam reforming process.
of waste having a calorific value of 18MJ/kg, considering The waste to chemicals approach allows to perform at the
also a combustion assisted with natural gas in order of same time two services, not only the synthesis of a chem-
2% of energetic content of waste would produce around ical but also the recovery of waste. Under this scenario in
34MWe. The latter needs to be replaced by electric ener- the LCA analysis waste enters with a credit of CO emis-
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gy from the grid. sion related to the avoided conventional disposal system
based on incinerator.
Emissions from waste to Hydrogen Under this scenario the waste to Hydrogen scheme here
For the waste to hydrogen plant the following contribution analyzed accounts for a saving of CO emission in order
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have been taken into account: of 90%. This means a potential reduction of emissions of
C1=CO emissions derived from all carbon contained in around 202.000 tCO /y.
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the waste which along the process is converted into CO .
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Considering the reference waste composition, this contri-
bution is in order of 16,5 tonCO /tonH . Acknowledgments
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C2=CO emissions derived from fuel consumption. This We kindly acknowledge Maire Tecnimont Group and its
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contribution considers the direct fuel consumption in the subsidiary NextChem for the support to the research
gasifier and auxiliary boiler. This contribution is in order of and development in the field of Waste to Chemical area.
1.9 ton CO /ton H2) MyRechemical is NextChem’s subsidiary for the Waste
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C3=CO emissions derived from fugitive emissions of to Chemical technology solutions, which are developed
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natural gas used along the project calculated as 2,5% of under a proprietary technological platform. The Circular
natural gas consumption [10] with a Methane GWP equal Hydrogen Trade Mark is under registration by NextChem.
Impiantistica Italiana - Gennaio-Febbraio 2022 47 47