Coal-fired Plants Research Articles

Ag-Cu modified ZSM-5 zeolite to effectively eliminate NOx and slip ammonia from coal-fired flue gas: Catalytic performance and characterization

To eliminate NOx emission and slip ammonia from coal-fired plants, ZSM-5 zeolites were modified with copper and different amount of silver. According to the activity measurement results, Ag1.5-Cu/ZSM-5 zeolite could exhibit 100 % NH3 conversion efficiency at 350 ℃ and the N2 selectivity was more than 90 %. Meanwhile, when NO was introduced in the gas flow, the NO and NH3 conversion efficiency of Ag1.5-Cu/ZSM-5 reached 97 % and 100 % at 300 ℃. The catalyst also showed good tolerance to H2O and SO2. XRD, BET, SEM and TEM experiments confirmed that the addition of silver and copper oxides would not destroy the MFI skeleton structure orsignificantly destroy the microporous and mesoporous structure of the molecular sieve. Moreover, Ag-Cu/ZSM-5 catalyst exhibited stronger surface acidity and promoted the NH3 adsorption ability (NH3-TPD). In addition, there were more active oxygen on Ag-Cu/ZSM-5 catalyst resulting from the interaction between silver and copper oxides, which contributed to its better redox performance (XPS and H2-TPR).

Continuous measurement of NO2 in flue gas employing cavity-enhanced spectroscopy sensing system

A cavity-enhanced spectroscopy sensing system for real-time and on-site measurement of nitrogen dioxide (NO2) in flue gas working in the spectral range of 430–450 nm is reported. The instrument acted on the transmitter and receiver in the form of optical fiber coupling, realizing the compactness of the system. Rayleigh scattering cross-sections of nitrogen and helium were measured to achieve the calibration of cavity mirror reflectivity accurately. The maximum reflectivity reached 99.9815 % at 448.3 nm, corresponding to a total loss of 185 ppm. A qualitative model theory was adopted to understand the adsorption process of NO2 gas in the optical cavity, and the performance of the highly integrated NO2 measurement system was improved by optimizing flow response time, and its repeatability and stability were also evaluated. Allan variance analysis indicates that detection limit of NO2 is 6.3 ppb by volume obtained at 20 s averaging time, and the sensitivity can be improved to 1 ppb at an optimal averaging time of 220 s. One day real-time monitoring of NO2 concentration near the flue gas sampling port of a coal-fired chemical plant was performed and the results were compared and analyzed with the variation of NO and O2 in flue gas to validate the applicability of the gas detection.

A Perspective on Decarbonizing Mobility: An All-Electrification vs. an All-Hydrogenization Venue

The growing demand for low-carbon fuel is predicted by ultimate goals to fit the carbon neutrality by 2050 in many countries and regions including the European Union. According to the International Energy Agency, the CO2 emissions related to transportation stand for around 30% of total annual emissions, and so, the decarbonization of the mobility sector has the highest priority. In this work, we attempt to evaluate the expected demand for low-carbon fuels, including blue and green hydrogen, and low-carbon electricity in order to compare the available and required capacities of low-carbon fuels and electricity. According to our calculations based on the figures from 2020, the transition toward H2 mobility would require an amount of hydrogen equal to 366 million tons/annum, and by 2035, this requirement will increase up to 422 million tons/annum, which is several times larger than the existing H2 production capacities. We have estimated the volume of the carbon capture and storage facilities required for full decarbonization of the mobility sector globally, and in the case of hydrogen mobility driven by blue hydrogen, it exceeds 4.0 billions tons of CO2 per annum, while the decarbonization of coal-fired plants will require more than 10.0 billions tons of CO2 per annum. In addition to the calculation of required resources, we have estimated the cost of the fuel and required capital investments and have compared different possible solutions from different points of view: economic viability, technical readiness, and social perception. Finally, it can be concluded that the decarbonization of the mobility sector would require a complex solution involving both low-carbon hydrogen and electrification, and the capacities of low-carbon fuel must be significantly increased in the following decade to fulfill the climate goals.

Commercial SCR catalyst modified with different noble metals (Ag, Pt, Pd) to efficiently remove slip ammonia and NOx in the flue gas

BackgroundWith the increasingly strict emission standard of flue gas, ammonia escape has been one of the urgent problems to be solved in the SCR process of coal-fired power plants. Slip ammonia is regarded as the secondary pollution in SCR process. Moreover, slip ammonia cannot only result in the deactivation of SCR catalyst, thus reducing NO removal efficiency, but also form NH4HSO4 and then corrode the equipment, which can do serious harm to the operation safety. Therefore, it is important to find ways to efficiently remove slip ammonia from the coal-fired plants with the complex gas composition. MethodsCommercial SCR (V2O5-WO3-TiO2) catalysts were modified with various noble metals (Ag, Pd, Pt) by improved impregnation methods. The NH3 oxidation performance of them was tested to select the most significant catalyst in selective catalytic oxidation of ammonia (NH3-SCO) and the effect of NO, SO2 and H2O were also investigated. Significant findingsThe experimental results showed that noble metals modification could all markedly improve the oxidation ability to remove slip ammonia from coal-fired plants and Ag/SCR catalyst obtained the best application prospect due to its low price. The NH3 conversion of Ag/SCR catalyst reached 92% at 350 °C. Moreover, 95% NOx could be removed when NO was introduced in the gas. Based on the characterization results, the introduction of noble metals had no visible influence on the structure and specific surface area of commercial SCR catalyst but it could increase the redox properties and the number and intensity of surface acidic sites. In addition, the redox cycles between noble metals and vanadium species on SCR catalyst surface were conducive to generate more active oxygen and promote the oxidation capacity of the catalysts.

High Performance of Commercial PAC on the Simultaneous Desulfurization and Denitrification of Wastewater From a Coal-Fired Heating Plant.

The flue gas desulfurization wastewater is highly saline and has too many refractory pollutants to be recycled during the desulfurization process of the coal-fired heating plant. Given that waste heat is abundant in coal-fired heating plants, a thermal treatment method was developed to simultaneously remove sulfates and nitrates from the wastewater, with the production of chemical-grade natroalunite and recycled water. The results showed that sulfates and nitrates were 50.3 and 10 g/L in the wastewater, respectively, and only 2.8% and 9.1% were removed after direct treatment at 270°C for 7 h; but these rates increased to 99.3% and 99.9%, respectively, with the addition of commercial poly aluminum chloride. Mass balance summarized that the treatment of 1 ton wastewater needed 0.1 ton PAC and produced 0.11 ton natroalunite and 0.92 ton recycle water. The removal of sulfates and nitrates was mainly done by the precipitation reaction of sulfates such as natroalunite and the redox reaction between nitrates and organics, respectively. Thermodynamic analysis demonstrated that the precipitate reaction occurred at 45°C and accelerated in the temperature range of 45–270°C, but became slow with the decrease of sulfate and Al concentrations in wastewater. Four other reagents were also used for wastewater treatment in comparison with PAC and showed the following order of performance: PAC > citrate calcium > limestone > subacetate aluminum > citrate ferric. This method provided a practical route to treat wastewater from flue gas desulfurization without generating secondary waste.

Excellent low temperature NH3-SCR and NH3-SCO performance over Ag-Mn/Ce-Ti catalyst: Evaluation and characterization

Low temperature SCR has been a promising technology due to the diverse load in coal-fired plants. However, ammonia escape problem could be more serious at low temperature on account of the condensation of NH4HSO4, resulting in deactivation of SCR catalyst and equipment corrosion. NH3-SCO technology could oxidize slip ammonia to harmless N2. Hence, it is important to develop a novel catalyst with high SCR and SCO efficiency at low temperature to remove NOx and slip NH3 and achieve the stable operation of SCR system. In this work, a combined sol-gel and impregnation method was used to synthetize different Aga−Mn/Ce-Ti (a = 2%, 5%, 8%) catalysts and applied in NOx and slip NH3 removal at low temperature. The activity measurement confirmed that Ag5-Mn/Ce-Ti catalyst exhibited an excellent low-temperature performance. At 150–300 °C, its NO conversion was 100%, NH3 conversion was above 95% and N2 selectivity was more than 90%. Moreover, considering the oxidation of slip ammonia, Ag5-Mn/Ce-Ti catalyst also exhibited above 90% NH3 conversion at 200–350 °C in the absence of NO. The catalytic performance could also be kept at a high level under the existence of SO2 and H2O. The characteristic results revealed that Ag and Mn modification could not apparently change the phase structure and could decrease the BET area to some extent. In addition, Ag-Mn/Ce-Ti catalyst possessed stronger and more surface acidic sites and contributed to better NH3 adsorption capacity. Besides, there was more chemisorbed oxygen on Ag-Mn/Ce-Ti catalyst resulting from the interactions among Ag, Mn and Ce oxides, which was responsible for its better redox property.

Ce–Ti catalysts modified with copper and vanadium to effectively remove slip NH3 and NOx from coal-fired plants

In this work, V/Ce–Ti catalysts were modified with different kinds of transition metals (Cu, Fe, Co, Mn) by sol–gel and impregnation methods. The NH3 oxidation performance of them was tested to select the most active catalyst in NH3-selective catalytic oxidation (NH3–SCO). The effect of NO, SO2 and H2O was also investigated. The experimental results indicate that 1% Cu–V/Ce–Ti catalyst exhibits the most significant ability to remove slip ammonia discharged from coal-fired plants and its NH3 conversion efficiency reaches 90% at 300 °C. In addition, 97% NOx can be removed when NO is introduced in the gas. Cu–V/Ce–Ti catalyst also obtains good resistance to H2O and SO2. Based on the characterization experiment, the introduced Cu and V are highly dispersed on Ce–Ti catalyst and they can increase the redox properties and the number of acidic sites. Besides, the redox cycles among Cu, V and Ce species on Cu–V/Ce–Ti catalyst surface are conducive to generating more active oxygen and promoting the oxidation capacity of the catalyst.

Co-combustion of Sewage Sludge in the Coal-Fired Heating Plant

Due to greening of production of electricity and heat some owners of heating plant are changing their fuel mix from fossil fuels to biomass one. The stabilized sewage sludge is in this biomass category as well. New Czech national legislation limits are stricter in parameters of biological activity, so the owners of water treatment plant are looking for new utilization of their stabilized sludge. There are some possibilities in combustion or co-combustion of this sludge in currently heating plant. The article describes the trial test of stabilized sludge combustion on heating plant technology. The heating plant is originally designed for combustion of brown coal. The stabilized sludge was produced at the municipal wastewater treatment plant, from where it was transported to low-temperature (78 °C) drying technology, from where it was transported in granular form to the heating plant in Mladá Boleslav. The fuel mixture of trial test was in energetic ratio of 23% dried sludge and 77% brown coal. The sludge was transported into the boilers by pneumatic conveying, which is used in normal operation for conveying pelletized phytomass. The result shows an increase in SO2 emissions from the original 189.91 mg∙m-3 to 407.98 mg∙m-3 and an increase in NOx emissions from 148.45 mg∙m-3 to 181.46 mg∙m-3. There were also detected increasing NH3 emissions due to reac-tion of control system in SNCR technology od decreasing of NOx emissions. The trial test was done during full op-eration of the heating plant. During the test there was also a lower steam production, from originally 38.17 kg∙s-1 to 34.44 kg∙s-1, which is related to the lower LHV compared to the reference fuel. There were no major operation problems, except higher dustiness during unloading of sludge. Finally, the Czech legislative problems associated with the combustion of stabilized sewage sludge are mentioned. In the current system, the sludge is established as waste, which forbids the combustion of it in conventional heating plants, even though all emission legislative limits are complied with. Nowadays the Ministry of the Environment of the Czech Republic is working on new regulation, which will determine new category of solid alternative fuels and it will be solution of this situation.

Multiple pollutants control of NO, benzene and toluene from coal-fired plant by Mo/Ni impregnated TiO2-based NH3-SCR catalyst: A DFT supported experimental study

There was a dearth of understanding regarding the mechanism of MPC catalyst activity and the creation of effective MPC catalysts for industrial low oxygen and high SO2 concentration environments. Herein, Mo/Ni was utilized to modify the commonly used WVTiOX catalyst to investigate the role and reaction mechanism of Mo/Ni in the MPC process. Mo/Ni doping greatly improved the MPC performance of the WVTiOX catalyst, increased the number of Brønsted and Lewis acid sites on the surface, promoted surface active oxygen Oα ratio, and intensified metal oxide synergy. The TiO2 (001) models of WVTiOX and NiWVTiOX catalysts were built, and the adsorption energies of NH3, O2, NO, C6H6, and C7H8 gaseous molecules on the surfaces of the two catalysts were calculated by density functional theory (DFT). The DFT and in situ DRIFTS results proved that NH3-SCR process of the catalyst was mainly governed by the L-H mechanism, while the E-R mechanism also worked to a certain extent. The following are possible benzene and toluene oxidation pathways on NiWVTiOX: C6H6 → C6H4O2 → C4H2O3 → CO2 + H2O and C7H8 → C6H5CH2OH → C6H5CHO → C6H5COOH → C4H2O3 → CO2 + H2O.

A Ten-Year Study on Alkali Content of Coal Fly Ash

After years of decline, coal consumption has risen significantly in the last year (2021), driven mainly by the ever-increasing demand in fast-growing Asian countries and fostered by rising gas prices in Europe and the United States. Coal is both the largest electricity production source and the largest source of carbon dioxide emission. Coal-fired plants produce electricity by generating steam by burning coal in a boiler, but also large amounts of coal fly ash. Coal fly ash contains essential constituents for cement production, such as Ca, Si, Al, and Fe. Application of coal-fired ash to produce clinker at high doses may reduce the limestone content in the raw mix. Furthermore, coal fly ash is one of the industrial source materials utilized in the development of low-carbon cements and concretes on account of its chemical characteristics. The monitoring methodology is based fundamentally on the analysis of a set of variables (Na2Oe, Na2O, K2O, free CaO, and reactive silica content and fineness) over time. Weak relations between Na2O and K2O, and Na2Oe, and reactive silica content were found. This applied research has been done to verify previously done research. The scope of this paper is to assess the alkaline content of coal fly ash over a period of 10 years. The Na2O-equivalent of coal fly ash ranged from 0.35% to 2.53%, with an average value of 0.79%. These values should be taken into account producing concretes made with potentially reactive aggregates in order to mitigate the alkali–silica reaction (ASR).

Removal of Reactive Yellow 4R Azo Dye from Synthetic Aqueous Solution by Alkali Hydrothermally Activated Fly Ash

Dye-containing wastewater affects the aesthetic quality, transparency and gas solubility of natural water bodies, hence colored wastewater must be treated before being discharged. Physical removal of dyes from wastewater can be achieved using activated carbon. However, this technique is expensive, so there is a need to find less expensive alternatives. A waste product generated from coal-fired plants known as fly ash is a sorbent that can be used to remove pollutants from solution. This study investigated the effectiveness of using alkali (NaOH) hydrothermally activated fly ash to remove Reactive Yellow 4R azo dye from synthetic aqueous solution. Na2O in alkali hydrothermally activated fly ash increases thirteen-fold. SEM observations revealed that the raw fly ash consisted of smooth round shaped particles, whereas the activated fly ash was composed of granular crystalline particles. Batch adsorption experiments of the dye at 25 °C showed that increasing the activated fly ash quantity (0.5 to 3.5 g) increased the removal efficiency from 30% to 39.3%. The Freundlich isotherm adsorption model best described the adsorption of Reactive Yellow 4R dye by alkali hydrothermally activated fly ash with KF = 1.49 x 10-21 mg/g. The dye adsorption kinetics by activated fly ash followed the Lagergren pseudo second order model, with calculated qe = 2.65 mg/g; k2 = 0.06 g/mg; and calculated h = 0.42 mg/g min‑1. Dye removal occurred primarily through surface adsorption and very little through intra-particle diffusion.

Philippines: Financial Sector Assessment Program-Technical Note on Bank Stress Test for Climate Change Risks

The Philippines is highly vulnerable to risks from climate change. The Philippines is categorized as one of the world’s most vulnerable countries to climate change and natural disasters, especially typhoons. Depending on where a severe typhoon hits the Philippines, it could potentially cause a systemic impact. All major cities and most of the population reside on the coastline, including the metropolitan Manila area where about 60 percent of economic activities take place. On the other hand, exposures to transition risk are concentrated in the coal-based power generation sector and the government’s licensing policy to build new power plants.

Technoeconomic Assessment of LNG-Fueled Solid Oxide Fuel Cells in Small Island Systems: The Patmos Island Case Study

Liquefied natural gas (LNG) is regarded as the cleanest among fossil fuels due to its lower environmental impact. In power plants, it emits 50–60% less carbon dioxide into the atmosphere compared to regular oil or coal-fired plants. As the demand for a lower environmental footprint is increasing, fuel cells powered by LNG are starting to appear as a promising technology, especially suitable for off-grid applications, since they can supply both electricity and heating. This article presents a techno-economic assessment for an integrated system consisting of a solid oxide fuel cell (SOFC) stack and a micro gas turbine (MGT) fueled by LNG, that feeds the waste heat to a multi-effect desalination system (MED) on the Greek island of Patmos. The partial or total replacement of the diesel engines on the non-interconnected island of Patmos with SOFC systems is investigated. The optimal system implementation is analyzed through a multi-stage approach that includes dynamic computational analysis, techno-economic evaluation of different scenarios using financial analysis and literature data, and analysis of the environmental and social impact on the island. Specific economic indicators such as payback, net present value, and internal rate of return were used to verify the economic feasibility of this system. Early results indicate that the most sensitive and important design parameter in the system is fuel cell capital cost, which has a significant effect on the balance between investment cost and repayment years. The results of this study also indicate that energy production with an LNG-fueled SOFC system is a promising solution for non-interconnected Greek islands, as an intermediate carrier prior to the long-term target of a CO₂-free economy.

Sustainable Systems for the Production of District Heating Using Meat-Bone Meal as Biofuel: A Polish Case Study

The developed production of heat (steam) by Farmutil Company enables use of renewable energy from biofuel meat-bone meal which is incinerated in rotary kilns utilising vapours and odours from its production, instead of natural gas, to ensure Farmutil’s own needs for heat. The transformation of existing district heating in Piła city (currently using coal) into a fourth generation district heating system was proposed, predicting the use of heat (hot water) after combustion of biofuel meat-bone meal as district heating in the city of Piła. The maximum possible surplus amount of heat that can be produced at Farmutil exceeds the needs for the district heating demands of the city of Piła (860,200 GJ/y) by 53.2% at a meat-bone meal burning scale of 150,000 t/y. The use of 52,000 t/y of meat-bone meal for district heating production also results in an increase in incomes through the sale of hydroxyapatite ash from its combustion, amounting 1.638 million EUR/y. The closure of the coal-fired heating plant eliminates the consumption of 44,000 t/y of coal and the need to pay CO2 emission permits amount to over 5.588 million EUR/y.

Mechanochemical Characterisation of Calcined Impure Kaolinitic Clay as a Composite Binder in Cementitious Mortars

The availability of some supplementary cementitious materials, especially fly ash, is of imminent concern in Europe due to the projected closure of several coal-fired power generation plants. Pure kaolinitic clays, which arguably have the potential to replace fly ash, are also scarce and expensive due to their use in other industrial applications. This paper examines the potential utilisation of low-grade kaolinitic clays for construction purposes. The clay sample was heat-treated at a temperature of 800 °C and evenly blended with Portland cement in substitutions of 10–30% by weight. The physical, chemical, mineralogical and mechanical characteristics of the blended calcined clay cement were determined. The Frattini test proved the pozzolanic potential of the calcined impure clay, as a plot of its CaO and OH− was found below the lime solubility curve. The 28 days compressive strengths trailed the reference cement by 5.1%, 12.3% and 21.7%, respectively, at all replacement levels. The optimum replacement level between the three blends was found to be 20 wt.%.

Sustainable Alternatives for Green Mortar: Quarry Waste and Ultra high fly ash utilization

The use of waste materials from different industries as a replacement of cement has gained much attention all over the world. In addition, many attempts have been done to replace partially or totally one of the ingredients from the mix design to lower the negative impacts of construction industry. In this study, quarry waste and fly ash were used as two different sustainable approaches to replace the maximum volume of natural alluvial sand and cement, respectively, in the traditional mortar matrix. The quarry waste is a by-product of quarries characterized with a large volume of fines, whereas, fly ash is the by-product of coal-fired electric generation plants. The performance of the green mortars containing the maximized volume of quarry waste and fly ash were evaluated with regard to the mechanical properties. The results have clearly indicated the beneficial use of the quarry waste and fly ash as a substitute for siliceous sand and cement respectively in preparation of green mortars. In addition, the cost and parametric analysis was also performed for a multi-story reinforced concrete building using the designed quarry sand and fly ash as concrete ingredients.

Coupling effects of mineral components on arsenic transformation during coal combustion

Exploring arsenic (As) transformation during coal combustion is beneficial for reducing its pollution. Herein, combustion experiments were developed at 1100–1300 °C in a fixed-bed experimental system with 25 types of coal samples. The occurrences of As in coal and combustion products were characterized. All the original forms of As in coal were found to be unstable during combustion. As retained in ash existed as water-soluble and ion-exchangeable and residual forms, but only as residual form at combustion temperature above 1200 °C. The distribution of As in gaseous and solid combustion products varied widely by coal types, which resulted from the coupling effects of multi-minerals in coal. Co-combustion experiments were conducted using As model compounds and pure minerals, by which the interaction of Ca, Fe, Si and Al minerals to retain As was elucidated. The As transformation during coal combustion was primarily attributed to the coupling action of Ca, Fe, Si and Al minerals in coal. As a result, As was retained as Ca–Si–Al–As and Fe–Si–Al–As composite salts in the ash, which have little environmental hazard. Utilizing the coupling effects of multi-minerals during combustion help reduce As pollution from coal-fired plants.

Sediment mercury concentration changes as a response to increased industrial activity in Coronel Bay, Chile

Among the main sources of atmospheric mercury emissions are thermoelectric plants that use coal to generate electricity. This heavy metal is transported by air from its origin to neighboring coastal areas, where it is deposited in the sediment record. This research evaluated the content and temporal distribution of Hg in the coastal sediments of Central Chile, Coronel Bay, industrialized zone with two operative thermoelectric plants, and Coliumo Bay, reference zone free of industry. To this end, sediment cores from the centers of the two bays were obtained. Laboratory results show that the greatest Hg contents were found in the surface strata of the Coronel Bay core, with concentrations up to an order of magnitude greater than those obtained in the same strata in Coliumo Bay. This increase in Hg concentration coincides with the beginning of industrial activity in Coronel, with greater concentrations observed from 2012 on, the year in which the industrial operation of two coal-fired thermoelectric plants on the bay began. Based on 210Pb activity and the relationships between Hg content and organic matter, it was established that the main pathway of Hg to sediment is atmospheric deposition, while Coliumo presented inputs that reflect local non anthropogenic sources.

Effect of fuel side deviations on the load-cycling performance of thermal power plants: A dynamic simulation

The operational flexibility of thermal power plants plays a critical role in accommodating the high penetration of intermittent renewable power. The load-cycling rate, which is an important feature of operational flexibility, is insufficient for thermal power plants. The unpredictable fuel side deviations that weaken the control system effect restrict the load-cycling performances of thermal power plants because fuel side parameters, including coal feed rate, air flow rate, and coal quality, cannot be controlled precisely due to the accuracy error of devices and variation in fuel characteristics. To explore the influence of fuel side deviations on the load-cycling processes of thermal power plants, dynamic simulation models of a coal-fired plant are developed, and the load-cycling processes with continuous deviations in the fuel side are simulated. The deviations of output power, live steam pressure, and live steam temperature are calculated and used to evaluate the influences. Results show that coal quality deviation has the most significant effect on load-cycling performance, which makes the maximum and cumulative deviations in output power increase to 1.15 and 1.10 times that without fuel side deviation. The effect of multiple input deviations lies upon the most significant deviation. For example, the maximum and cumulative deviations of output power increase to 1.15 and 1.09 times with deviations in the coal feed rate, air flow rate, and coal quality, which are close to those with only coal quality deviation. Reducing the impact of the dominant factor can effectively enhance the load-cycling performance of the coal-fired unit.

Performance Analysis of Cooling Wall of Supercritical CO2 Coal-Fired Plants

Performance Analysis of Cooling Wall of Supercritical CO2 Coal-Fired Plants