Carbon stable isotope analysis as a tool for tracing temperature during the El Tremedal underground coal gasification at great depth

Inherent Tracers for Carbon Capture and Storage in Sedimentary Formations: Composition and Applications

“…Fractionation of C-isotopes during gasification is likely due to increased bond strength of 13 C– 12 C compared to 12 C– 12 C, resulting in 13 C depletion in low molecular weight gases and 13 C enrichment in heavy residues such as tar and vacuum bottoms . C-isotope ratios will be δ 13 C CO < δ 13 C CH4 < δ 13 C hydrocarbons < δ 13 C coal < δ 13 C char < δ 13 C CO 2 at typical gasification temperatures (>1000 °C). − This suggests that any CO 2 produced by incomplete reactions in the first stage of gasification is likely to be enriched in 13 C compared to the original feedstock, while the resulting CO will be depleted in 13 C. This agrees with experimental results from underground coal gasification plants, ,, and natural gas generation via pyrolysis of coal and lignite, , which produced CO 2 enriched in 13 C by 2–10‰ relative to the feedstock. Conversely, CO 2 generated from CO via the shift reaction will be depleted in 13 C. In a simplistic scenario, all CO 2 resulting from gasification will be derived from the shift reaction, so we could expect CO 2 captured from Syngas plants to be the same as or isotopically lighter than the feedstock, depending on the efficiency of the gasification reactions and proportion of feedstock not converted to Syngas.…”

“…Two common terrigenic components in sedimentary formations are crust and mantle. Mantle noble gases are enriched in 3 He, with 3 He/ 4 He as high as 70 R A (R A being 3 He/ 4 He of atmosphere, 1.339 × 10 −6 ) while crustal noble gases are enriched in radiogenic noble gases ( 4 He and 40 Ar) and have 3 He/ 4 He < 0.7 R A 32 . In subsurface fluids a distinction exists between radiogenic and crustal components; the terrigenic crustal component is derived from radioactive decay, but represents the cumulative accumulation in the host rock, and is thus controlled by the age and chemistry of the geological formation hosting the fluid and the openness of the system, while the radiogenic component is added to the fluid by in situ radioactive decay and is thus a function of the host formation chemistry and fluid residence time.…”

Source apportionment of carbon during gasification of coal–biomass blends using stable carbon isotope analysis

“…Stable carbon isotope composition is determined as the ratio of 13 C/ 12 C in a substance relative to Pee Dee Belemnite (PDB), a cretaceous marine fossil having an anomalously high 13 C/ 12 C ratio, which is an internationally established reference standard for the stable isotope composition of carbon in natural materials. Carbon isotope ratios are commonly reported using delta notation (as δ 13 C values) in parts per thousand (per mil, ‰) [10,11,[14][15][16][17][18][19][20][21] as shown in Equation 1.…”

“…These two gases, CO and CO 2 could be produced in isotope equilibrium or they may form due to the gasification of solid carbon and re-equilibrate isotopically in the gasifier according to Equation 9. Using the observed δ 13 C values for CO 2 and CO and the carbon isotope fractionation factor reported as a function of temperature by Richet et al [20,[36][37][38], apparent equilibrium temperatures (AET) for the isotope exchange reaction can be estimated. Based on the values of fractionation factor for CO-CO 2 isotope exchange provided by Richet et al [36,38], with an increase in temperature, the difference between the δ 13 C values of CO 2 and CO decreases.…”

Model Predictive Control of UCG: An Experiment and Simulation Study

“…Since the UCG runs in the underground, some of the process variables cannot be measured directly by conventional hardware (e.g., underground temperature). Known proxies of underground temperature estimation are based on measurement of carbon isotopes [11,28] and radon emanations [54,58]. Various soft-sensing methods are developed for monitoring and prediction of UCG variables.…”