Academic literature on the topic 'Sulfur dioxide. Limestone. Chemical reactions Desulfurization'

AbstractMass transfer between the phases is a cornerstone of many technological processes and presents a topic whose understanding and modelling is of high importance. For instance, absorption of gases in liquid droplets is an underlying phenomenon for the desulfurization of flue gases in wet scrubbers. Wet scrubbing is an efficient cleaning method where the liquid is sprayed in a stream of rising gases, removing pollutants due to the concentration difference between the gas phase and droplets. A model for absorption in water droplets has been developed to describe the complex physical and chemical interactions during the exposure to flue gases. The main factors affecting the absorption are the mass transfer of pollutants through the gas–droplet interface and the aqueous phase chemistry in a droplet. The mass transfer coefficient, which has been modeled with several approaches, is the most significant parameter regulating the absorption dynamic into the droplet, while the in-droplet chemistry controls the maximum quantity of dissolved pollutants. Dissociation of sulfur dioxide and the chemical reactions in seawater have been described by the equilibrium reactions. Afterward, the influence of the mass transfer coefficient has been investigated, and the model has been validated against the literature data on a single droplet scale. Obtained results are comparable with the experimental measurements and indicate the applicability of the model for the design and development of industrial scrubbers.

The highly hydrophobic poly(ether sulfone)/fluorinated silica (PES/fSiO2) organic–inorganic composite membrane for sulfur dioxide (SO2) desulfurization was prepared by incorporating the fSiO2 particles on the PES membrane via sol–gel process and fluorination. The formation of PES/fSiO2 organic–inorganic composite membrane was examined by attenuated total reflectance Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermal gravimetric analysis, field-emission scanning electron microscopy, and water contact angle. The experimental results showed that the fSiO2 inorganic layer was tightly bonded to the PES membrane surface through silane chemical reactions. The incorporation of the fSiO2 inorganic layer on the PES membrane surface increases the surface roughness and reduces the surface free energy because of the hydrophobic dodecafluoroheptyl-propyl-trimethoxysilane. The hydrophobicity of the PES/fSiO2 composite membrane was dramatically enhanced from 78.0° of PES membrane to 128.2° of PES/fSiO2 membrane. Compared with PES membrane, the desulfurization performance of PES/fSiO2 membrane was investigated. PES/fSiO2 organic–inorganic composite membrane indicated a reasonably stable SO2 absorption flux of 7.69E-4 mol/m2 s during the 240-min-long time operation.

The unsteady state computational fluid dynamics model for gas-solid particle flow in industrial scale circulating fluidized bed boiler combining with combustion and desulfurization (using limestone solid sorbent) chemical reactions, both homogeneous and heterogeneous, was developed in this study. The effects of solid sorbent feeding position and solid sorbent particle size on sulfur dioxide concentration were investigated. The results showed that both the solid sorbent feeding position and solid sorbent particle size had an effect on the sulfur dioxide capture. Entering solid sorbent at the upper secondary air position gave lower sulfur dioxide concentration than the one at the lower secondary air position and fuel feed position, respectively. This can be explained by the influence of suitable temperature at the upper secondary air position for desulfurization chemical reaction. About the solid sorbent particle size, the sulfur dioxide capture was the lowest when using the largest solid sorbent particle size due to the system hydrodynamics.

A new wet FGD process in which sulfur dioxide was absorbed in the bubble reactor using granular limestone simultaneously adding acetic acid had been proposed. The main difference compared to conventional wet FGD process was the ability of the new process to utilize granular limestone directly as a desulphurization reagent simultaneously adding acetic acid. Thus, the pulverizing of limestone, which causes power consumption, can be saved. Only using granular limestone directly as absorbent without acetic acid, SO2 removal efficiency and limestone utilization were too low. Adding some concentration of acetic acid, the performance of the new wet FGD process was confirmed to be equal to or higher than that of a conventional process in various tests. Various parameters of the new FGD process which would affect the sulfur dioxide removal efficiency and limestone utilization were studied.

Abstract Sulfur dioxide is considered as an extremely harmful and toxic substance among the air pollutants emitted from the lignite- and other high-sulfur-coal based power plants, old tires processing units, smelters, and many other process industries. Various types of absorbents and desulfurization technologies have been developed and adopted by the industries to reduce the emission rate of SO2 gas. The present paper focuses on the ongoing advances in the development of varieties of regenerative and non-regenerative absorbents viz., Ca-based, Mg-based, Fe-based, Na-based, N2-based, and others along with various FGD technology, viz., wet, dry or semi-dry processes. Additionally, different types of contactors viz., packed column, jet column, spray tower, and slurry bubble columns along with their significant operational and design features have also been discussed. In the existing or newly installed limestone-based FGD plants, an increasing trend of the utilization of newly developed technologies such as limestone forced oxidation (LSFO) and magnesium-enhanced lime (MEL) are being used at an increasing rate. However, the development of low-cost sorbents, particularly suitable solid wastes, for the abatement of SO2 emission needs to be explored sincerely. Many such wastes cause air pollution by way of entrainment of fine particulate matter (PM), groundwater contamination by its leaching, or brings damage to crops due to its spreading onto the cultivation land. One such pollutant is marble waste and in this work, this has been suggested as a suitable substitute to limestone and cost-effective sorbent for the desulfurization of flue gases. The product of this process being sellable in the market or may be used as a raw material in several industries, it can also prove to be an important route of recycling and reuse of one of the air and water-polluting solid wastes.

Abstract Sulfur oxides, abbreviated to SOx, refer to both sulfur dioxide (SO2) and sulfur trioxide (SO3) that are gaseous pollutants emitted by the combustion of low-grade fuels, including heavy oils, sour gases and coal. Current Flue Gas Desulfurization (FGD) technologies mainly use limestone or CaO (quicklime) as sulfur scavenger. They consume water and produce significant stocks of calcium sulfate, a non-regenerable solid that has limited market outlets and is sometimes considered as waste. To tackle this problem, a multi-partner team has launched a two-phase program in order to develop a new, regenerative FGD concept. This partnership includes a GE Power team (Belfort, France), three research laboratories (IS2M-MPC, LGRE from University of Haute Alsace, Mulhouse and ICB-UTBM-LERMPS, Belfort), a ceramic material testing center (ICAR, Moncel les Luneville, France) and a consultancy organization skilled in materials (Zephir Alsace, Mulhouse). The main objective was to design a regenerable adsorbent that would not release any solid waste but would allow instead the recovery of sulfur in the form of H2SO4 (sulfuric acid) which is a valuable chemical commodity. A first subprogram, executed from September 2012 through March 2015 and called “DeSOx New Gen”, enabled the different partners to identify and test at lab scale a regenerable and durable adsorbent. This adsorbent, used initially in powder form, involved an organized mesoporous silica (SiO2), which was used as a support and was impregnated with copper oxide (CuO) likely to undergo reversible sulfation. Such binary system proved capable of achieving large numbers of successive adsorption/regeneration cycles (more than fifteen attained in the lab) without undergoing substantial activity loss. A second subprogram, initiated in September 2017 and called “AdSOx”, aimed to obtain and test a bead-shaped form of the previously developed adsorbent in view of industrial applications. This product in bead-shaped adsorbent was then evaluated in 2019 in a pilot combustion rig, the flue gases of which were representative of a real industrial combustion installation in terms of SOx, NOx, CO, CO2, H2O and PM (particulate matter). In these rig tests, the performances of the adsorbent for the capture of SOx, including its capability to be regenerated for multi-cyclic use, have been assessed in fluidized bed and most recently in fixed bed conditions. This paper outlines the most significant steps and outcomes of this collaborative two-phase development program. It also illustrates the interesting capabilities of mesoporous materials for the design of highly active sorption and catalytic systems.