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Global demand for hydrogen has been increasing significantly in recent years as a result of global efforts to decarbonize and the potential solutions that hydrogen technology can offer. For example, hydrogen demand in 2021 is 94 million tons and is expected to approach 130 million tons by 2030. Much of this demand is driven by chemical production (primarily ammonia and methanol), refining, and fuel economy. The largest share of this production comes from steam-methane reforming (SMR). Compared to other commercial hydrogen production processes, SMR is currently the most economically attractive due to its scalability, efficiency, low feedstock, production and operating costs.
However, unabated SMR is a significant source of greenhouse gas (GHG) emissions, generating approximately 10 kg of CO2 GHG emissions per 1 kg of H2 produced primarily due to the use of natural gas combustion in SMR furnaces to provide the heat needed to drive adsorptive reforming to high conversion rates. According to a recent report by the United Nations Environment Program (UNEP), the international community has made little progress in implementing strategies to reduce GHG emissions since the 2021 climate summit in Glasgow, UK. This lack of progress has put the world on track to exceed the Paris climate target by 1.5°C. In order for the hydrogen production sector to significantly reduce its share of greenhouse gas emissions, there is an urgent need to rapidly develop and deploy large-scale, system-wide decarbonization measures.
The main point of this paper
Existing hydrogen production technologies:
Blue hydrogen: Hydrogen production through small reactors with carbon capture, utilization and storage.
Green Hydrogen: Hydrogen production through electrolysis of water.
Status of low-emission hydrogen production:
Only 1 million tons of low-emission hydrogen was produced in 2021, mostly using steam methane reforming (SMR) technology with no emission reductions.
Paris Agreement Target:
100 million tons of low-emission hydrogen are needed to achieve net-zero global emissions by 2050.
Low-carbon solution for SMR:
Electrification of the SMR heating process through a power source that does not emit greenhouse gases.
Electric Heating Technology:
A variety of electrical heating options exist in the chemical industry, but there are no industrial-scale SMR electrical heating applications.
Small Reactor Electrification Research:
Electrification of small reactors is an active area of research.
Experimental Study:
The purpose of this study is to experimentally investigate the feasibility of Joule (resistance) heating of catalyst-coated high-resistance wires as a potential method of energizing the SMR heating process.
Experimental Methods:
Experimental-scale Joule heating experiments are conducted by applying direct current through an iron-aluminum metal wire.
The wires could be straight or coiled, uncoated or coated with reforming catalyst (Ni/ZrO2)
Joule heating technology:
This study examines Joule (resistance) heating as a new method for promoting electrochemical heating in steam methane reforming processes
Experimental Method:
A FeCrAl metal coil with Ni/ZrO2 catalyst uniformly coated on the surface was used to achieve steam methane reforming reaction at different temperatures by varying the voltage and adjusting the resistance power (50-90 W)
Experimental Results:
When the resistive power exceeded 60 W (estimated coil temperature of 750 °C), the methane conversion rate was significantly increased
Comparative Analysis:
Joule-heated Ni/ZrO2-coated metal coils were compared to conventionally heated coated metal coils and to Joule-heated uncoated ZrO2 metal coils to elucidate the roles of Ni and ZrO2 as well as the differences in heating methods
Effectiveness Evaluation:
Joule-heated Ni/ZrO2-coated metal coils resulted in higher methane conversion than conventionally heated Ni/ZrO2-coated metal coils over a range of power, indicating that the method of joule-heated catalyst-coated metal coils is effective for steam methane reforming under experimental conditions
Research Innovation Points:
A new method is proposed to reduce CO2 emissions during hydrogen production using Joule-heated catalyst-coated metal coils, which can achieve higher methane conversion rates under experimental conditions and provide a more environmentally friendly method for hydrogen production
Under the experimental conditions of this study, Joule heating of Ni/ zro2 coated wires was proved to be effective for SMR. The coating of Ni/ ZrO2 catalyst on FeCrAl wires was uniformly distributed with minimal exposure of bare wires. The nickel particles in the coating were uniformly distributed without significant agglomeration. By applying voltage to both ends of the coated wires at a range of power settings from 50-90 W, the experimental results showed that the methane conversion increased dramatically at power settings greater than 60 W (estimated wire temperature of 750°C.) The conversion of Ni/ zro2-coated wires was significantly higher than that of the uncoated wires or the zro2-coated wires, which clearly indicates that Ni is the active catalyst. Taken together, the results provide the first experimental evidence for the potential of electrothermal catalytic wire reactors for hydrogen production.
