Flue Gas Cleaning Research Articles

Biochar in cementitious material—A review on physical, chemical, mechanical, and durability properties

<abstract> <p>Ordinary Portland Cement (OPC) is a crucial building component and a valuable strategic resource. The production of cement accounts for 5% to 10% of global carbon dioxide (CO<sub>2</sub>) emissions. Over the years, many researchers have been studying ways to reduce the amount of CO<sub>2</sub> in the atmosphere caused by cement production. Due to its properties, biochar is found to be an interesting material to be utilised in the construction industry due to its effectiveness in CO<sub>2</sub> sequestration. Biochar is a solid residue created by the thermal breakdown of biomass at moderate temperatures (350–700 ℃) without oxygen or with a small amount of oxygen, sometimes known as bio-carbon. Biochar has a wide range of uses, including those for heating and electricity generation, cleaning flue gases, metallurgy, animal husbandry, agriculture, construction materials, and even medicine. The objective of this paper is to review the potential of biochar as a cementitious material by evaluating its physical, chemical, mechanical, and durability properties. Using biochar as a cementitious material makes it possible to conclude that cement production will be reduced over time by partial replacement, which will also promote and encourage sustainable development in the future.</p> </abstract>

Techno-Economic Analysis of Fluidized Bed Combustion of a Mixed Fuel from Sewage and Paper Mill Sludge

The treatment and disposal of sewage sludge is one of the most important and critical issues of wastewater treatment plants. One option for sludge liquidation is the production of fuel in the form of pellets from mixed sewage and paper mill sludge. This study presents the results of the combustion of pelletized fuels, namely sewage and paper mill sludge, and their 2:1 and 4:1 blends in a fluidized bed combustor. The flue gas was analysed after reaching a steady state at bed temperatures of 700–800 °C. Commonly used flue gas cleaning is still necessary, especially for SO2; therefore, it is worth mentioning that the addition of paper mill sludge reduced the mercury concentration in the flue gas to limits acceptable in most EU countries. The analysis of ash after combustion showed that magnesium, potassium, calcium, chromium, copper, zinc, arsenic, and lead remained mostly in the ash after combustion, while all cadmium from all fuels used was transferred into the flue gas together with a substantial part of chlorine and mercury. The pellets containing both sewage and paper mill sludge can be used as an environmentally friendly alternative fuel for fluidised bed combustion. The levelized cost of this alternative fuel is at the same current price level as lignite.

Technical possibilities of ash and sulphur oxides emission reduction at Russian coal-fired thermal power plants

The issues of the introduction of the best available technologies (BAT) at Russian coal-fired thermal power plants in accordance with the recommendations of the current information and technical handbook ITS 38-2017 are considered. It is shown that the technological indicators of ITS 38-2017 on emissions of solid fuel ash and sulphur dioxide do not solve the problem of reducing the negative impact on the environment. The analysis of the properties of burnt coals and available technologies for sulphur dioxides and ash cleaning of flue gases was carried out in order to determine new technological indicators for emissions of solid fuel ash and sulphur dioxide and the best available technologies for updating ITS 38-2017. The analysis of existing technologies for ash cleaning and desulphurization of gases was carried out and recommendations were given for areas of their effective application to meet different quantitative levels of technological indicators of emissions. New technological emission indicators for updating ITS 38 are proposed and justified. Recommendations are given to expand the list of the best available technologies recommended for implementation at Russian thermal power plants.

Investigation and Evaluation of Flue Gas Pollutants Emission in Waste-to-Energy Plant with Flue Gas Recirculation

The emissions of pollutants by waste-to-energy power plants, which contain more toxic substances owing to the complicated composition of municipal solid waste (MSW), such as NOx, SO2, HCl, HF, particulate matter, and heavy metals, has attracted increasing attention worldwide. To effectively control the pollutants, a flue gas cleaning system is indispensable in the operation of MSW incineration power plants. In this study, the flue gas cleaning system in a waste-to-energy power plant with flue gas recirculation (FGR) was evaluated. The concentrations of various pollutants were measured and compared with the standards at home and abroad. The results indicated that NOx emission can be effectively reduced by FGR, and that the emission concentration of NOx may meet the national emission standards only by adopting FGR. However, the emission levels of HCl and PM exceeded the limits in legislative standards; therefore, operation optimization or retrofit of a deacidification system and bag filter were proposed to comply with the international standards and near-zero-emissions goal.

Advanced Flue-Gas cleaning by wet oxidative scrubbing (WOS) using NaClO2 aqueous solutions

• Simultaneous de-SO x /de-NO x scrubbing enhanced by NaClO 2 solutions. • Advanced De-NO x performance in simultaneous absorption. • Synergistic role of SO 2 on the oxidation/absorption of NO x. • Faster de-NO x oxidative mechanisms under acidic NaClO 2 solutions. • Simultaneous absorption model based on operating dosage. In this work, we investigate the use of a Wet-Oxidative Scrubber (WOS) to simultaneously control SO 2 and NO x emissions from exhaust flue-gases. The experiments are performed in a pilot-scale scrubber with a simulated flue-gas containing 500 ppm v of SO 2 and 1030 ppm v of NO x , using water doped with 0.25–1% w/w of NaClO 2 . The results prove that the adopted WOS is able to simultaneously remove SO 2 and NO x , and a synergistic effect is observed for the presence of SO 2 in the flue-gas, which improves the NO x removal by establishing more effective and faster oxidative mechanisms under acidic conditions. A predictive model of the WOS unit performance based on the experimental dosage of NaClO 2 , which takes into account for all the operating parameters of the process, is developed to predict the de-SO x and de-NO x efficiencies and also the wash water pH.

Lime Based Construction Materials as a Carbon Sink

Lime is used in a variety of industrial sectors (e.g. construction materials, iron and steel industry, flue gas cleaning, etc.) By the thermal decomposition of limestone (CaCO3), known as calcination, two products are obtained: CO2 and quicklime, i.e. calcium oxide (CaO). There is a growing interest in quantifying and improving the potential of CO2 absorption of lime containing products during their operational life. The carbonation occurs during the lifetime of the lime application and it consists in the absorption of atmospheric CO2 that closes the loop by forming calcium carbonate back. Thus, a portion of the CO2 emitted during calcination is reabsorbed and stored in a permanent stable form. A literature review was carried out on the Carbonation Rate (CR) of lime used in three different construction materials: air-lime mortars, mixed air-lime mortars and hemplime. Out of 205 scientific publications reviewed, only 57 provide information about CR, specifically 21 for air-lime mortars, 27 for mixed air-lime mortars and 9 for hemplime. CR is 80-92% for pure air-lime mortars, 20-23% for mixed ones and 55% for hemplime. For all the materials, the CR trend over time was also assessed, according to the Fick’s law.

Flue Gas Composition and Treatment Potential of a Waste Incineration Plant

Waste-to-energy (WtE) incineration is an important technique in waste management systems and waste hierarchy. It is used to treat approximately 63% of the waste in European countries. The flue gas volumetric rate and its composition are essential to determine and monitor the emissions from waste incineration plants. This paper presents two methodologies used to evaluate the emissions from incinerators during the design phase. The first consists of a set of equations applicable in Excel (calculation model), while the second is the built-in components in Ebsilon 13.2 software which simulates the emissions from a furnace. This paper also proposes a comprehensive flue gas cleaning system for a simulated waste incineration plant in Jordan. According to Ebsilon, the results showed that for a 25 kg/s loading rate, there was 258,514 mg/Nm3, 749.90 mg/Nm3, 890.20 mg/Nm3, and 717 mg/Nm3 of CO2, NO2, SO2, and HCL, respectively. It was noted that these values relate to 1.5 of excess air ratio, where the effect of excess air ratio as the main driver for any combustion process was examined. The calculation method (set of equations) evaluated the flue gas volumetric rate, the CO2 emissions, and N2O and SO2 levels. Ebsilon allows for simulation of the treatment stages and calculates the amount of materials required. Selective non-catalytic reduction (SNCR) (a built-in component in the Ebsilon library) was used to treat the NO2 emissions. For 1.5 of excess air ratio, those emissions were reduced from 749 mg/Nm3 to 180 mg/Nm3, while the Ca(OH)2 injector used to treat the SO2 and HCL emissions reduced emissions from 890.20 mg/Nm3 and 717 mg/Nm3 to 44 mg/Nm3 and 7.16 mg/Nm3, respectively. Regarding the reduction in CO2, the spherical carbon absorption concept was simulated using 9.4 kg/s of carbon which was adequate to verify a 91% reduction rate of CO2. Furthermore, the calculation model was validated and approved as a valuable model to predict the flue gas volume, the oxygen required, and flue gas emissions at the design stage.

Flue gas cleaning by periodic absorption

AbstractSimulations and designs are presented of conventional and periodic SO2 absorption from exhaust gases using salt water as absorption solvent. Operating conditions resemble those of a maritime operation, involving relatively small amounts of SO2, so the separation is in the linear region. The advantages of periodic operation, as already demonstrated for conventional distillation remain valid for absorption processes: Less tall towers, than staged towers are possible, or substantially less salt water is required for the process employing periodic cycling.

Waste Originating from the Cleaning of Flue Gases from the Combustion of Industrial Wastes as a Lime Partial Replacement in Autoclaved Aerated Concrete

This paper aims to study the suitability of partial replacement of lime by waste originating from the cleaning of flue gases from the combustion of industrial wastes in the production of autoclaved aerated concrete (AAC). The compressive strength, bulk density, pore structure, phase composition, and microstructure of hydration products of the AAC were analyzed. According to the results, the addition of the waste can effectively enhance the mechanical properties of AAC due to the differences in morphology of hydration product—1.1 nm tobermorite and related dense microstructure. The pore size distribution was significantly influenced by waste addition, which was one of the main reasons for the increase in thermal conductivity. The XRD and SEM results showed that foreign ions introduced with the wastes affect the synthesis of 1.1 nm tobermorite. Moreover, it was shown that waste containing a high content of CaO can be used as lime replacement, which allows reducing CO2 emissions during the AAC production process.

Experimental Investigation of SO2 Removal from Flue Gases by Cleaning with Solution of Lime Suspension and Formic Acid

The experimental investigation presented in this research was performed in order to examine the possibility of the removal of SO2 from flue gases by cleaning with a solution of lime suspension and formic acid (Ca(OH)2 and HCOOH). Research was conducted in a laboratory plant (rotary kiln) of 44 kW. The mass of the lime suspension (LS) was 400 g. The mass of the LS was homogenized (mixed) in a sample cup with 2 g (0.5%), 4 g (1%) and 8 g (2%) of 60% formic acid. The solution was placed in a gas washing bottle, where a partial flow of flue gas generated by the combustion of diesel fuel was injected. Simultaneously with the diesel fuel combustion, SO2 from a bottle was injected in a rotary kiln. The average mass concentration of SO2 in the flue gas at the entry point of the gas washing bottle was around 2900 ppm. The results indicated that the absorption of SO2 by the cleaning of flue gas with LS was 96.83%. Adding formic acid to the LS in mass ratios of 0.5% (2 g), 1% (4 g) and 2% (8 g) resulted in absorptions of 99.25%, 98.77% and 98%, respectively. The absorption of flue gases in the gas washing bottle with LS, with the addition of formic acid in the mentioned ratios, showed a reduction in sulfates and pH value, and a rise in sulfides and calcium, respectively.

Comparative analysis of thermal economy of two SOFC-GT-ST triple hybrid power systems with carbon capture and LNG cold energy utilization

This paper studies the coupling of fuel cell power generation technology and conventional thermal power generation technology, constructs the thermodynamic model of combined cycle power generation of fuel cell, gas turbine and steam turbine, and analyzes the thermodynamic performance of the system from the important links such as compressor pressure ratio, steam carbon ratio, fuel utilization, fuel cell operating temperature and gas recirculation. Since natural gas as fuel will emit a lot of greenhouse gases, two new low-carbon power generation systems including composite power system, carbon capture and liquified natural gas cold energy utilization are proposed. In this paper, the post-combustion carbon capture which is more practical and conducive to the safe operation of the system is used. The adsorbents used in the two carbon capture methods are MDEA and CaO respectively. In the MDEA carbon capture process, flash tower and split flow process are added to reduce energy consumption. In the calcium looping carbon capture process, CO2 reflux process is set to optimize the calcination temperature, and two-stage waste heat boilers are set to recover a large amount of waste heat of CO2 and clean flue gas respectively. After that, to further save energy consumption, a method of cascade utilization of liquified natural gas cold energy is proposed. It can not only increase power output, but also provide natural gas at normal temperature and pressure for the system and the outside. The calculation results show that the efficiency of the optimized combined cycle system of fuel cell, gas turbine and steam turbine reaches 70.32%. In terms of energy saving, the system efficiency of MDEA carbon capture process is 1.81% higher than that of calcium looping carbon capture process, and calcium looping carbon capture process has more advantages in economic cost. In addition, the cascade utilization of liquified natural gas cold energy provides additional 410.86 kW, 382.64 kW electric energy and more directly usable natural gas for the two systems. The research results of this paper can provide meaningful guidance for the design of low-carbon and high-efficiency power generation system based on fuel cell.

Data-driven Models for Advanced Control of Acid Gas Treatment in Waste-to-energy Plants

This paper presents a study of identification and validation of data-driven models for the description of the acid gas treatment process, a key step of flue gas cleaning in waste-to-energy plants. The acid gas removal line of an Italian plant, based on the injection of hydrated lime, Ca(OH) 2 , for the abatement of hydrogen chloride, HCl, is investigated. The final goal is to minimize the feed rate of reactant needed to achieve the required HCl removal performance, also reducing as a consequence the production of solid process residues. Process data are collected during dedicated plant tests carried out by imposing Generalized Binary Noise (GBN) sequences to the flow rate of Ca(OH) 2 . Various input-output and state-space models are identified with success, and related model orders are optimized. The models are then validated on different datasets of routine plant operation. The proposed modeling approach appears reliable and promising for control purposes, once implemented into advanced model-based control structures.

Chemical Speciation Distribution and Thermal Stability of Heavy Metals Along Flue Gas Cleaning Systems in a Hazardous Waste Incinerator

Chemical Speciation Distribution and Thermal Stability of Heavy Metals Along Flue Gas Cleaning Systems in a Hazardous Waste Incinerator

Experimental study on the washing characteristics of fly ash from municipal solid waste incineration.

The disposal of fly ash with high salt content has become an important bottleneck for the further application of municipal solid waste incineration (MSWI). In this study, the soluble salt content and composition of fly ash from different MSWI were analysed. The composition of fly ash was affected by incinerator type and flue gas cleaning system, especially the type of deacidification solvent. The soluble salt content in fly ash from MSW grate incinerator can be over 35.16%. Most of the soluble salt was calcium salt and chloride salt. The effect of washing parameters including liquid/solid (L/S) ratio and washing time on salt removal from fly ash were studied. Raw fly ash contained high chlorine (Cl) with the maximum of 19.83% and it can be significantly reduced by washing. Double-washing and secondary-washing had better performance than single-washing on salt removal. The secondary-washing did not only save water, but also reduced the energy cost during evaporation for crystallising soluble salt. Based on the analysis of variance (ANOVA), L/S ratio was the most principal factor for salt and Cl removal of fly ash by washing.

Lab-Scale Carbonation of Wood Ash for CO2-Sequestration

This study evaluated the CO2 sequestration potential with combustion ashes in the aqueous phase. The aim was to provide a cost-effective carbon sequestration method for combustion unit operators (flue gas cleaning) or biogas producers (biogas upgrading). Therefore, two separate test series were executed to identify the carbonation efficiency (CE) of bottom wood ash (1) at different mixing ratios with water in batch experiments and (2) under dynamic flow conditions. It was furthermore evaluated whether subsequent use of the carbonated wood ash for soil amendment could be possible and whether the process water could be passed into the sewage. The batch test series showed that different mixing ratios of wood ash and water had an influence on the CE. The flow series showed that the mean CE varied between approximately 14% and 17%. Thus, the ash proved to be suitable for carbonation processes. The process water was dischargeable, and the carbonated wood ash has potential for chalking, as no legal thresholds were exceeded. Therefore, wood ash carbonation could be used as a low-tech CO2 sequestration technology. Compared to existing energy consuming and cost intensive carbon capture and storage technologies, sequestration with ash could be beneficial, as it represents a low-tech approach.

Investigation of the effect of condensed phase on the energy conditions for the initiation of the plasma-chemical process of flue gas cleaning by a pulsed electron beam

This work investigates the processes of dissipation of the charge and energy of a pulsed electron beam in gas compositions (nitrogen, carbon dioxide and oxygen) in the presence of ammonium sulphate and nitrate. A pulsed electron beam generated by the TEA-500 accelerator (Tomsk, Russia) with an electron energy of up to 410 keV, a beam current of up to 5 kA (I0 ), and a half-amplitude voltage pulse duration of 60 ns was injected into a 46 cm long drift chamber filled with a gas mixture. The pulsed electron beam current (IFC ) passing through the drift chamber was registered using a sectioned calorimeter with beam charge monitor function, and the efficiency of the current passage of the beam was determined as the ratio qFC/q0 , where q0 is the beam charge measured at the place of its injection into the chamber drift. The pressure in the drift chamber varied (375, 560 and 760 Torr, humidity value 15% ± 5% and 50% ± 5%). The geometric dimensions of the plasma-chemical reactor for initiating plasma-chemical reactions of flue gas cleaning were determined.

CHISA 2021 virtually – Worldwide Chemical Engineers Meeting

CHISA 2021 virtually – Worldwide Chemical Engineers Meeting You have just accessed a special issue of Chemical Engineering & Technology which is composed of contributions presented at the 24th International Congress of Chemical and Process Engineering CHISA held virtually on March 15–18, 2021 due to the pandemic of covid-19. Despite the difficult situation for both the organizers and the participants in regard to a new conference format, I feel that a nice virtual meeting of chemical engineers from all over the world was organized. However, it is clear that face-to-face discussions and meeting others in person cannot be easily replaced. The CHISA 2021 congress addressed the full spectrum of chemical and process engineering topics, such as reaction and catalysis engineering, separation processes, fluid flow and multiphase systems, computer-aided process engineering, and pharmaceutical engineering. Many interesting lectures and talks were presented, some of which are part of this special issue. The presented topics reflect the current focus of chemical engineering research on socially relevant subjects, such as decreasing environmental pollution. Studies on this topic deal with, e.g., introducing a new technology for efficient cleaning and heat recovery of flue gas from small-scale boilers, optimizing combustion processes via plasma activation while minimizing harmful emissions or removal of VOCs using an ionic liquid membrane. Another important topic is the transition from coal to green energy sources and the utilization of energy from waste; this is covered in studies on biomass gasification/combustion and fast pyrolysis of biomass and PE waste. Also included are studies of two-phase flow CFD modeling and image analysis of flow maldistribution during boiling in parallel minichannels and the utilization of catalytic processes to produce alkanes, biofuels, or synthesis gas. This is just a small sample of studies contained in this issue and I wish every reader to find a topic of interest. I want to thank the CHISA 2021 Scientific and Organizing Committees for providing an excellent platform and I hope that the next conference in 2022 will be in the usual format, allowing us again to meet in person in Prague. Prof. Dr.-Ing. Lucie Obalová Institute of Environmental Technology, CEET, VSB-Technical University of Ostrava Lucie Obalová

Efficient Cleaning and Heat Recovery of Flue Gas from a Small‐Scale Boiler

AbstractSmall‐scale biomass boilers contribute to the emission of particulate matter (PM) to the environment. In this study, the performance of a wet‐scrubber purification system for flue gas was experimentally investigated. The experimental setup consisted of a boiler, a wet scrubber, a generator, and heat exchangers. The results showed an average PM collection efficiency of ca. 42 % for a PM size range of 0.08–10 µm over a testing period of five months. Furthermore, the results showed an improvement in the heat recovery of about 18 %. Focusing only on the heat losses through exhaust flue gases, the losses were shown to have decreased by 72 %. During the total testing period of 8.5 months, no decrease could be noticed in the absorption solution ability.

Ways to reduce harmful emissions from the operation of power plants in special environmental control areas

The article examines the specifics of operating power plants in special environmental control areas, following the restrictions of the International Maritime Organization introduced in 2020. It focuses on innovative technologies such as the use of low-sulphur fuels, the implementation of SCR technology, the development of new logistical solutions and the use of new fuels. The method for controlling the emission of sulphur oxides into the atmosphere from power plants must be an integrated one, combining primary and secondary measures. Primary activities include purification of fuel from pollutants - improvement of fuel quality (enrichment of feedstock, use of alternative fuels); suppression of formation of harmful substances during combustion by improving fossil fuel combustion processes (by improving furnace designs, technological methods and regime measures, organization of mixture formation and combustion processes, improvement of fuel injection system). Secondary measures include technologies for capturing pollutants from flue gases, including methods designed for coarse and fine flue gas cleaning (flue gas recirculation, catalytic flue gas cleaning, wet methods, dry methods, absorbers for the cleaning of combustion products of sulphur oxides, cyclone-foam apparatus). The solution to the pollution of the World ocean, and in particular the special environmental control zones, by sulphur emissions from diesel engines primarily depends on the development of highly effective technologies to reduce its concentration at the diesel plant outlet.

Complex flue gas cleaning of thermal power plants

Currently, there are significant emissions of pollutants from electric power facilities in our country. At the TPP, sulfur and nitrogen purification technologies are practically not used, most of the installed ash collectors operate with low efficiency and using outdated technology, and environmental indicators are significantly inferior to foreign analogues. At the same time, there is experience in the development and development on an industrial scale of various methods and tools that provide a significant reduction in emissions of particulate matter, sulfur oxides and nitrogen. The article considers an example of such a technology. For particle cleaning, a ceramic high-temperature filter with a catalytic coating is used to selectively remove nitric oxide when interacting with carbomide. The sulfur is removed by chemical neutralization with a lime sorbent.