Prospects of Sunlight Driven Air-to-Methanol Synthesis via CO2 Electrolysis

<p>The race to save planet earth has led to significant advancement in technologies for harvesting renewable energy, carbon capture and conversion. Futures scenarios are being envisioned where CO₂ is captured from air and converted to valuable fuels and chemicals, with methanol (MeOH) being the most coveted product. Here we assess two potential air-to-MeOH pathways that harvest solar power via concentrated photovoltaic (CPV) cells for direct air capture (DAC) of CO₂ and subsequent conversion to MeOH by exploiting CO₂ electrolysis. Specifically, we perform techno-economic and life-cycle analysis on single-step (direct CO₂-to-MeOH electrolysis) and three-step (integration of H₂O electrolysis, CO₂-to-CO electrolysis, and hydrogenation reactor) air-to-MeOH routes. Our results indicate that in current scenario, the envisioned air-to-MeOH routes are not economically and environmentally compelling with high levelized costs of MeOH ~1180–1730 $/ton_MeOH and CO₂ emissions of ~2.29–2.69 /ton_MeOH. Using sensitivity analysis, we reveal targets for CPV capital cost ($290/kW), DAC capital cost ($375/(ton-CO₂/year)), and electricity emission intensity (<275 kg-CO₂/MWh) which will make the three-step route commercially and environmentally viable as a near-term technology. In contrast, direct CO₂-to-MeOH electrolysis will need drastic performance improvement to be economically competitive, with required current densities >300 mA/cm², energy efficiency >45% and stack stability >2 years. We hope this study will garner the key stakeholders to advance discussions about the cost and potential of this envisioned air-to-fuel technology. </p>

Prospects of Sunlight Driven Air-to-Methanol Synthesis via CO2 Electrolysis

<p>The race to save planet earth has led to significant advancement in technologies for harvesting renewable energy, carbon capture and conversion. Futures scenarios are being envisioned where CO₂ is captured from air and converted to valuable fuels and chemicals, with methanol (MeOH) being the most coveted product. Here we assess two potential air-to-MeOH pathways that harvest solar power via concentrated photovoltaic (CPV) cells for direct air capture (DAC) of CO₂ and subsequent conversion to MeOH by exploiting CO₂ electrolysis. Specifically, we perform techno-economic and life-cycle analysis on single-step (direct CO₂-to-MeOH electrolysis) and three-step (integration of H₂O electrolysis, CO₂-to-CO electrolysis, and hydrogenation reactor) air-to-MeOH routes. Our results indicate that in current scenario, the envisioned air-to-MeOH routes are not economically and environmentally compelling with high levelized costs of MeOH ~1180–1730 $/ton_MeOH and CO₂ emissions of ~2.29–2.69 /ton_MeOH. Using sensitivity analysis, we reveal targets for CPV capital cost ($290/kW), DAC capital cost ($375/(ton-CO₂/year)), and electricity emission intensity (<275 kg-CO₂/MWh) which will make the three-step route commercially and environmentally viable as a near-term technology. In contrast, direct CO₂-to-MeOH electrolysis will need drastic performance improvement to be economically competitive, with required current densities >300 mA/cm², energy efficiency >45% and stack stability >2 years. We hope this study will garner the key stakeholders to advance discussions about the cost and potential of this envisioned air-to-fuel technology. </p>

Evolution of Welding Residual Stresses within Cladding and Substrate during Electroslag Strip Cladding

Hydrogenation reactors are important oil-refining equipment that operate in high-temperature and high-pressure hydrogen environments and are commonly composed of 2.25Cr–1Mo–0.25V steel. For a hydrogenation reactor with a plate-welding structure, the processes and effects of welding residual stress (WRS) are very complicated due to the complexity of the welding structure. These complex welding residual stress distributions affect the service life of the equipment. This study investigates the evolution of welding residual stress during weld-overlay cladding for hydrogenation reactors using the finite element method (FEM). A blind hole method is applied to verify the proposed model. Unlike the classical model, WRS distribution in a cladding/substrate system in this study was found to be divided into three regions: the cladding layer, the stress-affected layer (SAL), and the substrate in this study. The SAL is defined as region coupling affected by the stresses of the cladding layer and substrate at the same time. The evolution of residual stress in these three regions was thoroughly analyzed in three steps with respect to the plastic-strain state of the SAL. Residual stress was rapidly generated in Stage 1, reaching about −440 MPa compression stress in the SAL region at the end of this stage after 2.5 s. After cooling for 154 s, at the end of Stage 2, the WRS distribution was fundamentally shaped except for in the cladding layer. The interface between the cladding layer and substrate is the most heavily damaged region due to the severe stress gradient and drastic change in WRS during the welding process. The effects of substrate thickness and preheat temperature were evaluated. The final WRS in the cladding layer first increased with the increase in substrate thickness, and then started to decline when substrate thickness reached a large-enough value. WRS magnitudes in the substrate and SAL decreased with the increase in preheat temperature and substrate thickness. Compressive WRS in the cladding layer, on the other hand, increased with the increase in preheat temperature.

Failure Analysis of Flange Sealing Surface of Outlet Pipeline of Wax Oil Hydrogenation Reactor

Hydrogenation reactor is the core equipment of various hydrogenation units or hydrogenation processes. Because of the harsh service environment, the difficult manufacturing technology, the high requirements and the expensive cost, the safety of hydrogenation reactor is a very important problem. The outlet flange of hydrogenation reactor in a petrochemical company suddenly cracked after several years of use. The maximum depth of the crack from the sealing surface to the depth of the flange is 165 mm, the circumferential cracking range is about 130 degrees. The crack is in a circumferential and curved line along the sealing groove, and has small bifurcations at the tip. In order to ensure the safety of equipment operation and prevent the recurrence of this kind of accident, the causes of flange failure were systematically analyzed and the preventive measures are formulated. This paper reviewed the manufacturing quality data of the failed flange, and carried out a series of tests and analyses, such as macroscopic inspection, penetration testing, ultrasonic testing, mechanical properties test, chemical composition analysis, metallographic structure analysis, finite element stress check and so on. Combined with the use environment and the operation parameters of the flange, we preliminarily analyze that the cause of flange cracking may be manufacturing defects. In order to avoid the failure of flanges again, it is recommended that the flanges of the same batch should be tested one by one to ensure the safe and stable operation of the device.

Experimental and Numerical Investigation on Manufacturing-Induced Material Inhomogeneity in Hydrogenation Reactor Shell

Hydrogenation reactor services as key equipment in chemical and energy industries. Manufacturing processes of hydrogenation reactor changes its performance before long-term service but impact of manufacturing residual influence remains unclear. In this work, actual material strength distribution (MSD) in hydrogenation reactor shell was investigated. First, a hydrogenation reactor shell made from 2.25Cr1Mo0.25V was dissected to measure MSD in thickness. Then, a numerical model was proposed to predict actual material strength in hydrogenation reactor shell. The model employs both data-driven and finite element techniques to simulate material evolution during manufacturing. Third, the predict results were discussed with respect to accuracy based on experiment result. Results exhibit good agreement between predicted value and experiment outcomes. At last, impact of manufacturing residual influence on load capacity of hydrogenation reactor shell was investigated. Results indicate that fit for service (FFS) evaluation of hydrogenation reactor based on heat treatment material properties is not conservative. This work will contribute to the accurate description of hydrogenation reactor's performance.

A Novel Process of H2/CO2 Membrane Separation of Shifted Syngas Coupled with Gasoil Hydrogenation

A novel process of membrane separation for H2/CO2 of shifted syngas coupled with gasoil hydrogenation (NMGH) is proposed. First, a new process, with two-stage CO2-selective and one-stage H2-selective membranes, was developed to substitute the conventional PSA separation devices to remove CO2 and purify H2 in coal gasification refineries to reduce energy consumption and investment costs. Then, the process was coupled with gasoil hydrogenation and the recycled H2 produced by the hydrogenation reactor could be further purified by the H2-selective membrane, which increased the H2 concentration of the hydrogenation reactor inlet by about 11 mol.% compared with the conventional direct recycling process, and the total system pressure was reduced by about 2470 kPa. At the same time, this additional membrane separation and purification prevented the accumulation of CO/CO2 in the recycled H2, which ensured the activity of the catalyst in the reactor and the long-term stable operation of the devices. Further, parameters such as compressor power, PI (polyimide)/PEO (polyethylene oxide) membrane area, pressure ratio on both sides of the membrane, and purity of make-up H2 were optimized by sensitivity analysis. The results showed that, compared with the conventional method, the NMGH process simplified operations, significantly reduced the total investment cost by $17.74 million, and lowered the total annual costs by $1.50 million/year.