scholarly journals (Solar) Mixed Reforming of Methane: Potential and Limits in Utilizing CO2 as Feedstock for Syngas Production—A Thermodynamic Analysis

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2537 ◽  
Author(s):  
Henrik von Storch ◽  
Sonja Becker-Hardt ◽  
Christian Sattler
Keyword(s):  
Outlet Temperature ◽  
Operating Pressure ◽  
Carbon Formation ◽  
Synthetic Fuels ◽  
Reactor Outlet ◽  
Reactor Inlet ◽  
Syngas Production ◽  
A Value ◽  
Methane Potential ◽  
Reforming Reactions

The reforming of natural gas with steam and CO2 is commonly referred to as mixed reforming and considered a promising route to utilize CO2 in the production of synthetic fuels and base chemicals such as methanol. In the present study, the mixed reforming reaction is assessed regarding its potential to effectively utilize CO2 in such processes based on simple thermodynamic models. Requirements for the mixed reforming reactions based on process considerations are defined. These are the avoidance of carbon formation in the reactor, high conversion of the valuable inlet streams CH4 and CO2 as well as a suitable syngas composition for subsequent synthesis. The syngas composition is evaluated based on the module M = ( z H 2 − z CO 2 ) / ( z CO 2 + z CO ) ,   which should assume a value close to 2. A large number of different configurations regarding CO2/H2O/CH4 at the reactor inlet, operating pressure and outlet temperature are simulated and evaluated according to the defined requirements. The results show that the actual potential of the mixed reforming reaction to utilize CO2 as feedstock for fuels and methanol is limited to approximately 0.35 CO2/CH4, which is significantly lower than suggested in literature. At 900 °C and 7 bar at the reactor outlet, which is seen suitable for solar reforming, a ratio of H2O/CH4 of 1.4 can be set and the resulting value of M is 1.92 (CO2/CO/H2 = 0.07/0.4/1).

scholarly journals The Integration of Process Heat Applications to High Temperature Gas Reactors

2011 ◽  
Author(s):  
Michael G. McKellar
Keyword(s):  
High Temperature ◽  
Greenhouse Gases ◽  
Industrial Process ◽  
Inlet Temperature ◽  
Condensation Temperature ◽  
Outlet Temperature ◽  
Reactor Outlet ◽  
Reactor Inlet ◽  
Process Heat ◽  
High Temperature Gas

A high temperature gas reactor, HTGR, can produce industrial process steam, high-temperature heat-transfer gases, and/or electricity. In conventional industrial processes, these products are generated by the combustion of fossil fuels such as coal and natural gas, resulting in significant emissions of greenhouse gases such as carbon dioxide. Heat or electricity produced in an HTGR could be used to supply process heat or electricity to conventional processes without generating any greenhouse gases. Process heat from a reactor needs to be transported by a gas to the industrial process. Two such gases were considered in this study: helium and steam. For this analysis, it was assumed that steam was delivered at 17 MPa and 540°C and helium was delivered at 7 MPa and at a variety of temperatures. The temperature of the gas returning from the industrial process and going to the HTGR must be within certain temperature ranges to maintain the correct reactor inlet temperature for a particular reactor outlet temperature. The returning gas may be below the reactor inlet temperature, ROT, but not above. The optimal return temperature produces the maximum process heat gas flow rate. For steam, the delivered pressure sets an optimal reactor outlet temperature based on the condensation temperature of the steam. ROTs greater than 769.7°C produce no additional advantage for the production of steam.

Characterisation of Tar produced in the Gasification of Biomass with in situ Catalytic Reforming

2010 ◽  
Vol 8 (1) ◽  
Author(s):  
Sergio Rapagnà ◽  
Katia Gallucci ◽  
Manuela Di Marcello ◽  
Muriel Matt ◽  
Pier U Foscolo ◽  
...  
Keyword(s):  
Fluidized Bed ◽  
Renewable Energy Sources ◽  
Technical Specification ◽  
Steam Gasification ◽  
Outlet Temperature ◽  
Processing Unit ◽  
Reactor Outlet ◽  
Distributed Power Generation ◽  
Product Gas ◽  
Power Generation Systems

This paper concerns the cleaning of the hot gas produced by steam gasification of biomass in a fluidized bed. The cleaning takes place in a catalytic filter candle device placed directly in the freeboard of the bed. Such integration results in a compact processing unit and increased thermal efficiency; the result of the cleaning being carried out directly at the reactor outlet temperature. It thus lends itself to exploitation in distributed power generation systems utilizing renewable energy sources. Results are reported for runs performed in a bench scale fluidized bed steam gasifier fitted with a single full-size catalytic candle filter. Tar and particulates in the product gas were sampled in accord with technical specification CEN/TS 15439 with analysis by UV and fluorescence spectroscopy.

scholarly journals Optimization and Comparison of Direct and Indirect Supercritical Carbon Dioxide Power Plant Cycles for Nuclear Applications

2011 ◽  
Author(s):  
Edwin A. Harvego ◽  
Michael G. McKellar
Keyword(s):  
Power Plant ◽  
Supercritical Co2 ◽  
Operating Conditions ◽  
Working Fluid ◽  
Primary System ◽  
Outlet Temperature ◽  
Reactor Outlet ◽  
Temperature Range ◽  
System Pressure ◽  
Intermediate Heat Exchanger

Results of analyses performed using the UniSim process analyses software to evaluate the performance of both a direct and indirect supercritical CO2 Brayton power plant cycle with recompression at different reactor outlet temperatures are presented. The direct supercritical CO2 power plant cycle transferred heat directly from a 600 MWt reactor to the supercritical CO2 working fluid supplied to the turbine generator at approximately 20 MPa. The indirect supercritical CO2 cycle assumed a helium-cooled Very High Temperature Reactor (VHTR), operating at a primary system pressure of approximately 7.0 MPa, delivered heat through an intermediate heat exchanger to the secondary indirect supercritical CO2 recompression Brayton cycle, again operating at a pressure of about 20 MPa. For both the direct and indirect power plant cycles, sensitivity calculations were performed for reactor outlet temperature between 550°C and 850°C. The UniSim models used realistic component parameters and operating conditions to model the complete reactor and power conversion systems. CO2 properties were evaluated, and the operating ranges of the cycles were adjusted to take advantage of the rapidly changing properties of CO2 near the critical point. The results of the analyses showed that, for the direct supercritical CO2 power plant cycle, thermal efficiencies in the range of approximately 40 to 50% can be achieved over the reactor coolant outlet temperature range of 550°C to 850°C. For the indirect supercritical CO2 power plant cycle, thermal efficiencies were approximately 11–13% lower than those obtained for the direct cycle over the same reactor outlet temperature range.

Effect of Methyl Chloride on Landfill Gas Dry Reforming

2012 ◽  
Author(s):  
McKenzie P. Kohn ◽  
Marco J. Castaldi ◽  
Robert J. Farrauto
Keyword(s):  
Landfill Gas ◽  
Methyl Chloride ◽  
Dry Reforming ◽  
Liquid Fuels ◽  
Carbon Formation ◽  
Syngas Production ◽  
Engine Combustion ◽  
Mixture Prior ◽  
Activity Decrease ◽  
Al2o3 Catalyst

Landfills are the second-largest source of anthropogenic methane emissions in the U.S., accounting for 22% of CH4 emissions. Landfill gas (LFG) is primarily composed of CH4 and CO2, and currently only 18% of this is used for energy. Because landfills will continue to be used for the foreseeable future, complete utilization of LFG is becoming more important as the demand for energy increases. Catalytically reforming LFG produces syngas (H2 and CO) that can be converted to liquid fuels or mixed into the LFG stream to produce a more reactive, cleaner burning fuel. It has been demonstrated that injecting 5% syngas into a simulated LFG mixture prior to engine combustion decreases CO, UHC, and NOx emissions by 73%, 89%, and 38%, respectively. One barrier to using LFG in a catalytic system is the contaminant content of the LFG, including chlorine and sulfur compounds, higher order hydrocarbons, and siloxanes that have the potential to poison a catalyst. Chlorinated compounds are present in LFG at 10–100ppm levels and are often found as chlorocarbons. This research explores the effect of methyl chloride on the activity of a Rh/γ-Al2O3 catalyst while dry reforming LFG to syngas. It has been found that methyl chloride acts as a reversible poison on the dry reforming reaction, causing a loss in dry reforming activity, decrease in syngas production, and increase in H2/CO ratio while CH3Cl is present in the feed. CH3Cl exposure also decreases the acidity of the catalyst which decreases carbon formation and deactivation due to coking.

Syngas production from methane steam reforming and dry reforming reactions over sintering-resistant Ni@SiO2 catalyst

2019 ◽  
Vol 46 (3) ◽  
pp. 1735-1748 ◽  
Author(s):  
Bolin Han ◽  
Fagen Wang ◽  
Linjia Zhang ◽  
Yan Wang ◽  
Weiqiang Fan ◽  
...  
Keyword(s):  
Steam Reforming ◽  
Dry Reforming ◽  
Methane Steam Reforming ◽  
Syngas Production ◽  
Methane Steam ◽  
Reforming Reactions

Turning carbon dioxide into fuel

2010 ◽  
Vol 368 (1923) ◽  
pp. 3343-3364 ◽  
Author(s):  
Z. Jiang ◽  
T. Xiao ◽  
V. L. Kuznetsov ◽  
P. P. Edwards
Keyword(s):  
Carbon Dioxide ◽  
Greenhouse Gases ◽  
Carbon Capture ◽  
Large Scale ◽  
Fossil Fuels ◽  
Political Support ◽  
Synthetic Fuels ◽  
Science And Engineering ◽  
Syngas Production ◽  
Future Demands

Our present dependence on fossil fuels means that, as our demand for energy inevitably increases, so do emissions of greenhouse gases, most notably carbon dioxide (CO 2 ). To avoid the obvious consequences on climate change, the concentration of such greenhouse gases in the atmosphere must be stabilized. But, as populations grow and economies develop, future demands now ensure that energy will be one of the defining issues of this century. This unique set of (coupled) challenges also means that science and engineering have a unique opportunity—and a burgeoning challenge—to apply their understanding to provide sustainable energy solutions. Integrated carbon capture and subsequent sequestration is generally advanced as the most promising option to tackle greenhouse gases in the short to medium term. Here, we provide a brief overview of an alternative mid- to long-term option, namely, the capture and conversion of CO 2 , to produce sustainable, synthetic hydrocarbon or carbonaceous fuels, most notably for transportation purposes. Basically, the approach centres on the concept of the large-scale re-use of CO 2 released by human activity to produce synthetic fuels, and how this challenging approach could assume an important role in tackling the issue of global CO 2 emissions. We highlight three possible strategies involving CO 2 conversion by physico-chemical approaches: sustainable (or renewable) synthetic methanol, syngas production derived from flue gases from coal-, gas- or oil-fired electric power stations, and photochemical production of synthetic fuels. The use of CO 2 to synthesize commodity chemicals is covered elsewhere ( Arakawa et al.  2001 Chem. Rev. 101 , 953–996); this review is focused on the possibilities for the conversion of CO 2 to fuels. Although these three prototypical areas differ in their ultimate applications, the underpinning thermodynamic considerations centre on the conversion—and hence the utilization—of CO 2 . Here, we hope to illustrate that advances in the science and engineering of materials are critical for these new energy technologies, and specific examples are given for all three examples. With sufficient advances, and institutional and political support, such scientific and technological innovations could help to regulate/stabilize the CO 2 levels in the atmosphere and thereby extend the use of fossil-fuel-derived feedstocks.

Sign in / Sign up

Export Citation Format

Share Document