Victorian Lignite Research Articles

Options for net zero emissions hydrogen from Victorian lignite. Part 2: Ammonia production

This the second of a two-part study investigating the feasibility of producing export quantities (770 t/d) of blue hydrogen meeting international emissions standards, by gasification of Victorian lignite plus carbon capture and storage (CCS). Part 1 focussed on the resources, energy requirements, and greenhouse gas emissions associated with the production of gaseous and liquefied hydrogen, while Part 2 focusses on the production of ammonia as an alternative hydrogen carrier for export.In this study, an Aspen Plus simulation of a conventional 1500 t d−1 iron-based catalyst Haber-Bosch ammonia synthesis process is developed and incorporated into the earlier lignite-to-hydrogen process model. Development of the simulation involves (i) estimation of the instantaneous rate kinetics, (ii) calibration against test data for a reactor of known dimensions, (iii) scaling up the bed dimensions to achieve a target production capacity, (iv) selecting an appropriate feed gas composition to optimise performance, (v) adjusting purge gas flowrates to achieve stable operation, and (v) incorporation into the previous lignite-to-hydrogen simulation.This study finds that 178.2 t h−1 liquid ammonia and all electricity required to support the process can be produced from 1050 t h−1 Victorian lignite. Surprisingly, the simulation results show that the electrical power requirement for ammonia synthesis (176.4 MW) is essentially the same as that needed for liquefaction of an equivalent output of hydrogen (175.5 MW). On this basis both options are equally attractive, although ammonia synthesis is at a higher level of technological maturity than large-scale hydrogen liquefaction.This is the first study to quantify the greenhouse gas emissions intensity of ammonia production from lignite, accounting for the full production chain from lignite mining to CO2 sequestration. It is found that ammonia can be produced from Victorian lignite with very low CO2 emission intensity (0.49 kgCO2-e kgNH3−1) equivalent to that of next-generation natural gas reforming with CCS processes. If required, the emission intensity can be reduced to 0.05kgCO2-e kgNH3−1 with a post-combustion CO2 capture system, and then made carbon neutral by co-gasification with ≤1.4% biomass.For comparison, this study also examines the implications of producing the same quantity of green ammonia using renewable energy alone. It is estimated that production of 178.2 t h−1 green ammonia would require 1946 MW renewable energy and associated transmission infrastructure. In Victoria, this could be supplied by a wind farm with a 5.4 GW rated capacity, occupying an area of over 72,000 ha. This is highly unlikely to be a viable option.This analysis indicates that clean hydrogen in the form of ammonia, produced in Victoria by lignite gasification with CCS, can be consistent with global emissions reductions targets over the next few decades. The unique combination of low-cost lignite and high-quality CO2 storage geology means that Victoria is well placed to become a significant exporter of low-emissions ammonia to the world market. Further research is recommended on recovery of energy from the low grade waste heat streams and opportunities for additional electricity generation using the organic Rankine cycle.

Options for net zero emissions hydrogen from Victorian lignite. Part 1: Gaseous and liquefied hydrogen

This two-part paper investigates the feasibility of producing export quantities (770 t/d) of blue hydrogen meeting international standards, by gasification of Victorian lignite plus carbon capture and storage (CCS). The study involves a detailed Aspen Plus simulation analysis of the entire production process, taking into account fugitive methane emissions during lignite mining. Part 1 focusses on the resources, energy requirements and greenhouse gas emissions associated with production of gaseous and liquefied hydrogen, while Part 2 focusses on production of ammonia as a hydrogen carrier.In this study, the proposed process comprises lignite mining, lignite drying and milling, air separation unit (ASU), dry-feed entrained flow gasification, gas cooling and cleaning, sour water-gas shift reaction, acid gas removal, pressure swing adsorption (PSA) for hydrogen purification, elemental sulphur recovery, CO2 compression for transport and injection, hydrogen liquefaction, steam and gas turbines to generate all process power, plus an optional post-combustion CO2 capture step. High grade waste heat is utilised for process heat and power generation. Three alternative process scenarios are investigated as options to reduce resource utilisation and greenhouse gas emissions: replacing the gas turbine with renewable energy from off-site wind turbines, and co-gasification of lignite with either biomass or biochar. In each case, the specific net greenhouse gas intensity is estimated and compared to the EU Taxonomy specification for sustainable hydrogen.This is the first time that a coal-to-hydrogen study has quantified the greenhouse gas emissions across the entire production chain, including upstream fugitive methane emissions. It is found that both gaseous and liquefied hydrogen can be produced from Victorian lignite, along with all necessary electricity, with specific emissions intensity (SEI) of 2.70 kg CO2-e/kg H2 and 2.73 kg CO2-e/kg H2, respectively. These values conform to the EU Taxonomy limit of 3.0 kg CO2-e/kg H2. This result is achieved using a Selexol™ plant for CO2 capture, operating at 89.5%–91.7% overall capture efficiency. Importantly, the very low fugitive methane emissions associated with Victorian lignite mining is crucial to the low SEI of the process, making this is a critical advantage over the alternative natural gas or black coal processes.This study shows that there are technical options available to further reduce the SEI to meet tightening emissions targets. An additional post-combustion MDEA CO2 capture unit can be added to increase the capture efficiency to 99.0%–99.2% and reduce the SEI to 0.3 kg CO2-e/kg H2. Emissions intensity can be further reduced by utilising renewable energy rather than co-production of electricity on site. Net zero emissions can then be achieved by co-gasification with ≤1.4 dry wt.% biomass, while a higher proportion of biomass would achieve net-negative emissions. Thus, options exist for production of blue hydrogen from Victorian lignite consistent with a ‘net zero by 2050’ target.

Factors affecting ammonium capture by some Victorian lignites

ABSTRACT Nitrogen (N) loss from intensive animal husbandry leads to economic loss and environmental damage. Lignite has a demonstrated capacity to suppress ammonia (NH3) volatilisation from manure and this has been attributed to the pH, cation exchange capacity (CEC), pH buffer capacity and labile carbon (C) content of the lignite. Whilst lignite is effective in mitigating NH3 loss, the capacity for N retention and how this is influenced by the lignite's properties are not well studied. It is unclear if lignites from different mines will have comparable N retention under similar conditions. In this study, we characterised five Victorian lignites for their C-containing functional groups, surface morphology and chemical properties. These were then related to the ammonium () adsorption capacity of the lignites using a batch isotherm technique. The contribution of biological immobilisation to the N retention capacity of the lignites was determined using 15N tracing in an incubation study. All lignites were acidic (pHH2O: 3.3–5.8; pHCaCl2: 3.0–5.4). The lignite had similar patterns of distribution of C functional groups with the carboxyl C between 2.8% and 5.3%. The maximum adsorption capacity (Qmax ) varied with the composition of the lignite and correlated positively with the lignites’ CEC, pH and carboxyl groups. Increase in pH, especially from pH >5, resulted in up to 3-fold increase in Qmax (25.6 mg g−1), likely due to deprotonation of carboxyl groups. Compared to adsorption, the biological immobilisation of did not play a substantial role in the overall lignite's N retention capacity. Highlights Victorian lignites were assessed for their retention capacity using adsorption isotherms and 15N tracing. adsorption capacity of lignites increased (up to 3-fold) with pH, especially from pH 5 to 7. Biological immobilisation did not play a substantial role in the retention capacity of the lignites. pH-dependent adsorption was the dominant means by which lignite retained .

Sequential conversion of lignite in alkaline water by oxidative degradation, dissolution and catalytic gasification

We have demonstrated a sequence of degradation, dissolution and catalytic hydrothermal gasification (CHTG) of lignite in alkaline water. A Victorian lignite was subjected to hydrothermal treatment (HT) in an aqueous solution of NaOH at 250 °C, and then oxidation with pressurized O2 at 100 °C. The sequential HT and oxidation solubilized a 95% portion of the lignite on mass/carbon bases. The resulting solution was further converted by CHTG in a flow reactor at 350 °C for 10 h, employing a ruthenium/activated-charcoal catalyst (ruthenium loading; 16 wt%). The initial carbon conversion to gas was as high as 98% while CH4, CO2 and H2 were produced. The conversion gradually decreased due to coke deposition over the catalyst but was near steady around 83% at 8–10 h. The solubilized lignite consisted of compounds with molecular mass up to 5,000. The heavier portion (molecular mass > 1,000) was responsible for the coke formation and accumulation that caused the catalyst deactivation.

Re-examination of Thermogravimetric Kinetic Analysis of Lignite Char Gasification

Kinetic analysis of CO2 gasification by thermogravimetry was examined employing chars from a Victorian lignite. The gasification of char from the rigorously acid-washed lignite was extremely slow. More than 600 min was required for the complete gasification as a result of a near absence of inherent alkali and alkaline earth metallic (AAEM) species. It was nonetheless necessary to strictly choose the following conditions for eliminating the mass transfer effect: an initial mass of char of <1.3 mg, a particle size of char of <125 μm, and a total gas flow rate of ≥1000 mL standard temperature and pressure min–1. Such requirement arose from the inhibition of non-catalytic gasification by CO within the char particle. On the other hand, the char from the original lignite was gasified much faster than the non-catalytic gasification and completed within 50 min by catalysis of the inherent AAEM species. The measured rate of catalytic gasification was, unexpectedly, independent of the initial char mass and particle size and gas flow rate. This was reasonably explained by no or little importance of CO inhibition in the catalytic gasification. This study has also drawn another important conclusion that the non-catalytic gasification obeyed first-order kinetics with respect to the char mass. The rate constant was steady over the entire range of char conversion, while both the specific surface area and carbon-type distribution of the char varied along with the conversion.

Performance Evaluation of Thermo Chemical Behavior of PCI Under Optimal Conditions

In this study, a three-dimensional mathematical model is used to simulate the flow and thermo chemical behavior of the enhanced operation of PCI Victorian lignite under optimal FC conditions. The geometry of the model includes a lance, a blowtorch, a nozzle, a track and a coke bed at the bottom of a BF. Under the same operating conditions, the highest temperature in the main coal pavilion is observed in the brindled lignite container due to its higher volatile matter content. Injecting lignite into briquettes can achieve a higher overall combustion value than the semi-coke container and the carbon container in the ducting. The comparison confirms the possibility of replacing the replacement coal with PCI coal with an improved lignite, as it shows a very similar evolution of the combustion characteristics under the same operating conditions.

Effect of SiO2 on loss of catalysis of inherent metallic species in CO2 gasification of coke from lignite

Inherent metallic species retained by coal char or coke, such as Na and Ca, behave as catalysts in gasification. The char/coke normally contains inherent SiO2, which can react with the inherent catalysts to form silicates, resulting in catalyst deactivation over the range of pyrolysis, carbonization and gasification, and thereby reducing the char/coke reactivity. The present authors simulated the inherent catalyst deactivation experimentally by blending a Victorian lignite with SiO2, briquetting the SiO2/lignite blend, carbonizing the briquette, and then gasifying the coke with CO2. The kinetic analysis of the gasification employed a comprehensive model, which assumed progress in parallel of non-catalytic and catalytic gasification. The model quantitatively described the measured kinetics of the coke gasification with different SiO2 contents over a range of coke conversion up to 99.9%. The kinetic analysis revealed that the SiO2 deactivated substantial and entire portions of the most active catalyst and its precursor, respectively, before the gasification (i.e., during the carbonization). The catalyst deactivation also occurred during the gasification, but mainly following a self-deactivation mechanism that involved no silicates formation.

Insights into Carbonation Kinetics of Fly Ash from Victorian Lignite for CO2 Sequestration

Mineral carbonation of fly ash can both capture and store CO2 permanently in a single process without long-term monitoring. Previous studies indicate that fly ash with high calcium and magnesium contents exhibit promising CO2 fixation capability. However, the reaction mechanisms and kinetics involved in the carbonation reaction of fly ash is still not fully understood. In this study, a typical Victorian brown coal fly ash from Hazelwood power plant was selected to sequestrate CO2 in a direct aqueous carbonation process. Experiments were conducted in a vessel reactor at various temperatures (40, 50, 60, and 70 °C), stirring rates (900, 1050, 1200, and 1350 rpm), and CO2 pressures (3, 4, 5, 6, and 7 bar) to investigate the reaction kinetics and identify the rate-limiting steps of carbonation. The results show that both the carbonation rate and the maximum carbonation efficiency could be improved by optimizing parameters and by the introduction of NaHCO3. Also, the complex effects of the operating parameters...

No.17 豪州ビクトリア褐炭改質法Cat-HTR技術の実証

No.17 豪州ビクトリア褐炭改質法Cat-HTR技術の実証

Steam–Oxygen Gasification of Potassium-Loaded Lignite: Proof of Concept of Type IV Gasification

An advanced type of gasification at atmospheric pressure, which is termed type IV gasification, has been proposed with potential performance to achieve a stand-alone cold gas efficiency over 95% lower heating value (LHV). This work aimed to prove the concept of type IV gasification of lignite. Continuous conversion of a Victorian lignite was simulated experimentally in a sequence of pyrolysis of potassium (K)-loaded lignite, vapor-phase steam–oxygen reforming of volatiles, and simultaneous steam reforming over the K-loaded char and its steam gasification. Systematic investigation of the effects of key operating variables on the process performance has reached their combination that realized steady-state carbon conversion of ≈100% together with tar concentration in the syngas of <30 mg Nm–3 dry. A suite of variables, K loading to the lignite of 3.3 wt % dry lignite, steam/carbon molar ratio of <0.8, oxygen/carbon molar ratio of <0.24, temperature for the pyrolysis of 600 °C, and char bed temperature for st...

Lignite amendment has limited impacts on soil microbial communities and mineral nitrogen availability

The application of lignite (brown coal) as a soil amendment has been shown to provide a number of benefits under certain circumstances, including increased cation exchange capacity, increased phosphorus availability and reduced heavy metal availability. However, there is also evidence that some lignites can have negative impacts on soil biology, with very little known about how lignite affects soil nitrogen (N) dynamics and microbial activity. We conducted a microcosm experiment to assess the influence of lignite from Victoria, Australia, and the same lignite in combination with urea, on soil microbial community composition, biomass, activity and nitrogen cycling. Extractable NO3− and NH4+, microbial biomass, phospholipid fatty acids (PLFAs), microbial respiration and enzymes activities were measured over a 120-day incubation period. The lignite had minor effects on inorganic N concentration in different soil types with or without urea application. Lignite reduced the total CO2 emissions from soil over the incubation period, primarily by inhibiting respiration shortly after application. Changes to total microbial biomass were negligible, but shifts in the soil microbial community caused by lignite or urea application were detected up to 60 days after treatment. During this time, periodic increases in peroxidase and phenol oxidase activities in lignite-treated soils were also observed, but changes in dehydrogenase activities were only apparent in urea-treated soils. Our results indicate that raw Victorian lignite has only a minor, temporary impact on soil microbial activity, community composition and N-cycling and does not increase CO2 emissions over a short time period of investigation. More research is now needed to determine potential longer-term impacts at the field scale.

Modification of Reactivity and Strength of Formed Coke from Victorian Lignite by Leaching of Metallic Species

Binderless briquetting of lignite at 100–200°C and subsequent carbonization produces formed coke with tensile strength (ST) of 5–40 MPa, while the briquetting often requires mechanical pressure over 100 MPa. High reactivity is another feature of the lignite-derived coke, and this arises from highly dispersed metallic species such as alkali/alkaline-earth metallic species and ferrous/ferric ones that catalyze CO2 gasification. This work investigated effects of leaching of those metallic species in aqueous solution of hydrochloric acid, acetic acid or oxalic acid on the reactivity and ST of resulting coke from a lignite. The leaching at pH ≤ 1 removed catalytic metallic species near completely, reducing the coke reactivity by a factor of 8–15. The reduced reactivity was similar to the reactivity of coke from a typical coking coal. The leaching at pH ≤ 2.2 increased ST from 6 to 13 MPa for briquetting at 200°C and 32 MPa. The performance of leaching with oxalic acid, of that solution had pH of 0.75 at 1 mol/L, was much better than that with acetic acid. This work also examined another type of leaching, oxidation of the lignite in aqueous solution of hydrogen per- oxide, which produced organic mono-/di-acids in-situ from the oxidation of aromatic carbons of the lignite. The degree of reduction of the coke reactivity was between that for leaching at pH of 1 and 2. The deg- radation of macromolecules enhanced plasticizability of the lignite under briquetting and increased ST of the resulting coke to 22 MPa.

Preparation and Steam Gasification of Fe-Ion Exchanged Lignite Prepared with Iron Metal, Water, and Pressurized CO2

This paper proposes an environment-friendly method to load ferrous ion (Fe2+) to lignite with water, iron metal and carbon dioxide (CO2) but without mineral acids or iron salts containing potentially harmful components. Iron metal was dissolved into 25 °C water that had been saturated with CO2 at its gaseous pressure of 4.0 MPa. The solubility of ferrous iron was 1 070 mg-Fe/L-water. This solubility was much higher than that predicted from the solubility product (Ksp) of FeCO3 with an assumption that Fe2+ represented the dissolved ferrous iron. Rather, another assumption of coexistence of Fe2+, FeHCO3+, and Fe(HCO3)2 reasonably explained the measured solubility of ferrous iron. The dissolved ferrous iron was loaded to a Victorian lignite by ion exchange. The iron-loaded lignites with different iron concentrations (0.3–6.7 wt %-dry-lignite) were subjected to a sequence of pyrolysis and steam gasification to produce synthesis gas in a thermogravimetric analyzer. The gasification was catalyzed by the loaded iron regardless of its concentration, while the quickest at 1.0 wt % where dispersion of iron-derived catalytic species in the char matrix was maintained until its complete gasification with steam.

Detailed Analysis of Residual Volatiles in Chars from the Pyrolysis of Biomass and Lignite

Pyrolysis of biomass or coal, if operated at temperature high enough to complete tar evolution, is expected to give resulting char a tar-free nature. Use of such tar-free char instead of the original fuel in gasification would reduce or even completely eliminate the need for use of complex devices/mechanisms for tar/soot removal. Increasing pyrolysis temperature may not only decrease the content of residual tar in the char but also reduce its reactivity in the gasification. There is thus a range of optimum pyrolysis temperatures depending on the original fuel and type/mode of gasification, which yields char of suitable quality. In this work, a variety of char samples were prepared by pyrolysis (first pyrolysis) of three different woody biomass feedstock and a Victorian lignite with heating rate and peak temperature of 10 °C/min and 450–750 °C, respectively, and were further subjected to flash pyrolysis (second pyrolysis) at 920 °C. A gas-chromatography/ mass-spectrometry (GC/MS) detected more than 200 com...

Characterisation of lignite as an industrial adsorbent

An alternative use of the abundant and inexpensive lignite (also known as brown coal) as an industrial adsorbent has been characterised. The adsorptive properties of two Victorian lignite without any pre-treatment were investigated using the cationic methylene blue dye as a model compound in aqueous solutions. Two commercial activated carbon products were also studied for comparison. The adsorption equilibrium of the four adsorbents was better described by the Langmuir isotherm model than the Freundlich model. The adsorption capacities of the two untreated lignite adsorbents, Loy Yang and Yallourn, calculated using Langmuir isotherms were 286 and 370mg/g, respectively, higher than a coconut shell-based activated carbon (167mg/g), but lower than a coal-based activated carbon (435mg/g). Surface area results suggested that larger micropores and mesopores were important for achieving good methylene blue adsorption by the activated carbons. However, FTIR and cation exchange capacity analyses revealed that, for the lignite, chemical interactions between lignite surface functional groups and methylene blue molecules occurred, thereby augmenting its adsorption capacity.

The effect of cation content of some raw and ion-exchanged Victorian lignites on their equilibrium moisture content and surface area

Six Victorian lignites of known inorganic content have been water and acid-washed. The acid-washed form of one of these lignites (LYLA(R)) was subsequently exchanged with Na, Mg, Ca and Al salts. The equilibrium moisture contents (EMC) of all samples have been determined across a range of relative vapour pressures (RVP) extending previous observations in the case of a single lignite exchanged with a series of cations. Previous measurements for a single lignite exchanged with a series of cations have only been made at a single RVP. The effects of the different metal cations on the EMC values varied depending on the RVP. The surface areas determined by CO2 adsorption also showed an effect of cation content.

Gasification Performance of Australian Lignites in a Pressurized Fluidized Bed Gasifier Process Development Unit Under Air and Oxygen-enriched Air Blown Conditions

This paper discusses the gasification performance of a number of Australian lignites in a high temperature winkler (HTW) gasification process development unit (PDU) capable of running at a pressure, temperature, and feed rate of 10 bar, 1000°C, and 250 kg h−1 respectively. The fuels include three Victorian lignites, one South Australian lignite, and a char derived from a Victorian lignite. All fuels were pre-dried to less than 20% moisture content. The tests were of 3–32 h duration. The majority of the tests were conducted at 8 bar(g) pressure, 125–240 kg h−1 feed rate, 750–920°C average bed temperature, and involved steam and air or steam and oxygen-enriched air as reactants for gasification. Carbon conversion ranged between 70-87%, with further improvement limited by elutriation of carbon-rich fines originating from a large fraction of fine particles present in the feed, and brittle nature of these lignites which generate fines through attrition. An acceptable calorific value of 4 MJ kg−1 of the fuel gas has been attained. An assessment of the reasons and the extent of loss of char through elutriation has been investigated through tests in a 1:1 scale cold model and characterization of the char.

Comparison of some physico–chemical properties of Victorian lignite dewatered under non-evaporative conditions

A Victorian lignite, designated Loy Yang low ash, run of mine (LYLA (R)) has been dewatered using mechanical thermal expression (MTE) at 150–200 °C and 6–25 MPa and by hydrothermal dewatering (HTD) at 200–300 °C and the products compared. Total acidity values for all samples as measured by a pyrolysis thermogravimetric Fourier transform infrared (TG–FTIR) method were similar to those measured by barium ion exchange. Stronger (carboxylic) acid values determined by pyrolysis TG–FTIR tended to be lower than ion exchange values, except for the 300 °C HTD sample, for which both methods gave similar values although these were much lower than at all of the other treatment temperatures. Equilibrium moisture contents (EMC) for the MTE products and the 200 °C HTD product were similar to those of the original lignite at relative vapour pressure (RVP) ⩽ 52%, but lower at RVP 92%. EMC values for 300 °C HTD products were all lower than for the original lignite, indicating that processing temperature was the most important factor in determining these properties. CO 2 adsorption surface area was also mainly a function of processing temperature, decreasing with increasing temperature. However, the pore volume as determined by mercury porosimetry was influenced by whether dewatering was effected by MTE or HTD, the mechanical pressure applied in the MTE process resulting in a lower porosity.

A comparison of adsorption isotherms using different techniques for a range of raw, water- and acid-washed lignites

Adsorption isotherms based on desiccator measurements at 30 °C have been constructed for six Victorian lignites (five raw, one water-washed and six acid-washed samples). The results for a selection of samples have been shown to be in good agreement with more detailed isotherms obtained using two different automated microbalances. This suggests that the rate of approach to the final relative vapor pressure has little effect. The equilibrium moisture contents at 51.4% relative vapor pressure or less for the acid-washed lignite samples showed moderately good correlations ( R 2∼0.5) with the carboxylic acid concentration, but much weaker correlations with the phenolic content.

Lignite–water interactions studied by phase transition—differential scanning calorimetry

Differential Scanning Calorimetry measurements have been made over the temperature range 20 to −50 °C with a cooling rate of 5 °C/min for six raw Victorian lignites, and for some of these lignites after water washing or acid washing. Two small peaks were observed in the region −28 to −36 °C, as found by earlier workers, in addition to a major peak at −5±3 °C which was assigned to the freezing of free water. Solutions of sodium chloride showed a single peak at about −42 °C as well as the main water peak at approximately −20 °C. However, water or acid washing the lignites to remove cations gave samples which retained the small peaks in this region with little change in intensity so that an association between the small peaks and cations or dissolved salts is unlikely. Dry samples of the coals showed no peaks, confirming that these small peaks are associated with coal–water interactions and not with the coal structure or the presence of cations.