Zeolite sorbent that effectively removes mercury from flue gases

The measurement and control of mercury (Hg) emissions from utility power plants continue to be the subjects of much study. In a programme funded by the Department of Energy, Physical Sciences Inc (PSI) has developed a Hg sorbent using a zeolite material with a proprietary agent for improved capture of elemental as well as oxidized Hg. Joseph R Morency, Thomai Panagiotou & Constance L Senior present some promising laboratory results.     

Degradation of concrete by flue gases from coal combustion

The effect of flue gases from coal combustion on the concrete shell of a power plant stack was analyzed and the damage to the concrete was evaluated. The compressive and tensile strengths of concrete were determined by rebound hammer test and pull-off test on the site. Samples of concrete taken from various zones of the stack shell were analyzed in detail. The examination techniques used included chemical analysis, water suspension analyses, XRD, thermal analysis, SEM and EDS. It was found that the flue gases and the acid condensate, acted very aggressively at an elevated temperature and caused severe degradation of the inside surface zone of the concrete shell. The binding material in this zone was converted into sulfur-bearing compounds. Gypsum was identified as the dominant compound in the degraded zone of concrete in the upper parts, while anhydrite in the lower parts of the stack. Carbonated zone was located below the clearly delimitated sulfated zone of the concrete. The aggressive environment in the stack did not affect the internal zones in the concrete.     

Determining the coefficients of air consumption from volumetric analysis of flue gases during the breakdown of material being calcined

Conclusions A formula is proposed for determining the quantity of carbon dioxide evolved from material being burnt (dolomite, magnesite, or limestone) per 1 kg or 1 Nm³ for fuel, and also a formula for determining the coefficient of air consumption during the combustion of any fuel in the presence or absence, within the combustion products, of gases from the material being broken down (CO₂).Translated from Ogneupory, No. 7, pp. 9–12, July, 1970.Here and subsequently instead of coefficient of excess air, the term coefficient of air consumption will be used.     

Thermoneutral tri-reforming of flue gases from coal- and gas-fired power stations

The treatment of flue gases from fossil fuel fired power stations by tri-reforming with natural gas or by coal gasification could become an attractive approach for converting the CO₂, H₂O, O₂, and N₂ contained in these flue gases via syngas processing into useful products, such as methanol, hydrogen, ammonia, or urea. The present study determines the constraints for achieving such thermochemical reactions under conditions of thermoneutrality, by reacting the flue gases with water, air, and natural gas or coal at 1000–1200 K. The implications of such reactions are examined in terms of CO₂ emission avoidance, fuel saving, economic viability, and exergy efficiency.     

改性活性炭脱除模拟烟气中气态汞的实验研究

以椰壳活性炭为原料,经硝酸活化再采用NaCl或NaBr溶液化学浸渍改性制备燃煤烟气脱汞吸附剂。通过N_2吸附-脱附(BET),扫描电子显微镜(SEM),X射线光电子能谱(XPS)对制备的吸附剂进行表征,并且采用模拟烟气在管道喷射装置内考察汞吸附脱除性能。结果表明:与原始椰壳活性炭相比,经硝酸活化后的椰壳活性炭汞吸附能力得到提高;而采用NaBr改性后的椰壳活性炭脱汞效果最好。在管道喷射实验装置内,经过1 mol/L NaBr改性后的椰壳活性炭,在模拟烟气温度120℃,碳汞质量比8 000,停留时间2 s条件下,脱汞率达到92.7%。改性后的椰壳活性炭是一种具有潜在应用价值的优良脱汞吸附剂。     

碱液吸收法治理含NOx工艺尾气实验研究

为了提高碱液吸收氮氧化物废气的吸收效率,控制氮氧化物废气的排放,在直径为25 mm,高度1 000 mm的填料吸收塔内,对碱液吸收法治理含NOx工艺尾气的过程进行了研究,主要探讨了填料塔中的填料、吸收液、喷淋密度和氧化度对氮氧化物脱除效果的影响。结果表明:相对于同样的吸收条件,填料的表面积越大,空隙率越高,则吸收效果越好;NaOH溶液和Na2CO3溶液对氮氧化物都能达到较好的脱除效果,但是相对于最佳的脱除效果,NaOH溶液的质量浓度却比Na2CO3溶液的质量浓度低;碱液吸收含NOx工艺尾气的适宜喷淋密度为12 m3/(m2.h);当氧化度为50%左右时,吸收效果可以达到更好。     

低浓度二氧化硫冶炼烟气处理工艺

介绍了有色冶炼行业低浓度二氧化硫烟气的处理工艺,包括烟气脱硫、非稳态转化工艺、WSA工艺、一转一吸加尾吸工艺、常规两转两吸制酸工艺。企业应结合自身的实际情况,根据冶炼系统不同的烟气浓度和烟气量,选择合适的处理工艺。     

Understanding the effects of sulfur on mercury capture from coal-fired utility flue gases

Coal combustion continues to be a major source of energy throughout the world and is the leading contributor to anthropogenic mercury emissions. Effective control of these emissions requires a good understanding of how other flue gas constituents such as sulfur dioxide (SO₂) and sulfur trioxide (SO₃) may interfere in the removal process. Most of the current literature suggests that SO₂ hinders elemental mercury (Hg⁰) oxidation by scavenging oxidizing species such as chlorine (Cl₂) and reduces the overall efficiency of mercury capture, while there is evidence to suggest that SO₂ with oxygen (O₂) enhances Hg⁰ oxidation by promoting Cl₂ formation below 100 °C. However, studies in which SO₂ was shown to have a positive correlation with Hg⁰ oxidation in full-scale utilities indicate that these interactions may be heavily dependent on operating conditions, particularly chlorine content of the coal and temperature. While bench-scale studies explicitly targeting SO₃ are scarce, the general consensus among full-scale coal-fired utilities is that its presence in flue gas has a strong negative correlation with mercury capture efficiency. The exact reason behind this observed correlation is not completely clear, however. While SO₃ is an inevitable product of SO₂ oxidation by O₂, a reaction that hinders Hg⁰ oxidation, it readily reacts with water vapor, forms sulfuric acid (H₂SO₄) at the surface of carbon, and physically blocks active sites of carbon. On the other hand, H₂SO₄ on carbon surfaces may increase mercury capacity either through the creation of oxidation sites on the carbon surface or through a direct reaction of mercury with the acid. However, neither of these beneficial impacts is expected to be of practical significance for an activated carbon injection system in a real coal-fired utility flue gas.     

Removal of nitric oxide and sulfur dioxide from flue gases using a FeII-ethylenediamineteraacetate solution

The combined absorption of NO and SO₂ into the Fe(II)-ethylenediamineteraacetate(EDTA) solution has been realized. Activated carbon is used to catalyze the reduction of Fe^III-EDTA to Fe^II-EDTA to maintain the ability to remove NO with the Fe-EDTA solution. The reductant is the sulfite/bisulfite ions produced by SO₂ dissolved into the aqueous solution. Experiments have been performed to determine the effects of activated carbon of coconut shell, pH value, temperature of absorption and regeneration, O₂ partial pressure, sulfite/bisulfite and chloride concentration on the combined elimination of NO and SO₂ with Fe^II-EDTA solution coupled with the Fe^II-EDTA regeneration catalyzed by activated carbon. The experimental results indicate that NO removal efficiency increases with activated carbon mass. There is an optimum pH of 7.5 for this process. The NO removal efficiency increases with the liquid flow rate but it is not necessary to increase the liquid flow rate beyond 25 ml min^?1. The NO removal efficiency decreases with the absorption temperature as the temperature is over 35 °C. The Fe²⁺ regeneration rate may be speeded up with temperature. The NO removal efficiency decreases with O₂ partial pressure in the gas streams. The NO removal efficiency is enhanced with the sulfite/bisulfite concentration. Chloride does not affect the NO removal. Ca(OH)₂ and MgO slurries have little influence on NO removal. High NO and SO₂ removal efficiencies can be maintained at a high level for a long period of time with this heterogeneous catalytic process.     

Mathematical modeling of desublimation of carbon dioxide from flue gases of heat power systems

A quasi-nonstationary mathematical model of the low-temperature desublimation of carbon dioxide from purified flue gases of heat power systems has been developed. Process calculation results at parameters that correspond to its integration into the power trigeneration module based on a combination of Rankine and refrigeration cycles are given. Optimal operation estimates were obtained, which could be used to select an optimal engineering solution (changing the diameter of the heat exchanger tubes or the use of parallel units).     

Energy-saving technology for scrubbing waste gases from frit furnaces

Translated from Steklo i Keramika, No. 2, pp. 14–15, February, 1992.     

Pith based spherical activated carbon for CO2 removal from flue gases

Serials of pitch based spherical activated carbons (PSACs) were prepared and used as adsorbent for CO₂ adsorption from flue gases. The results indicate that the ultrafine micropores (<1 nm) are effective pores for CO₂ adsorption, and the equilibrium adsorption capacity of CO₂ has a linear relationship with the specific surface area of ultrafine micropores (S_{<1 nm}). The adsorption capacity of CO₂ can obtain 1.12 mmol/g at 15 kPa and 30 °C on one of PSAC sample due to its high S_{<1 nm} (845 m²_/g). Because the molecular CO₂ can be polarized into polar molecules and has four kinds of adsorption configuration, the adsorption selectivities of CO₂ vs. N₂ and O₂ are 86.99% and 69.91%, respectively. When the combined Electric Swing Adsorption and Vacuum Swing Adsorption were applied for CO₂ desorption, about 100% desorption efficiency can be obtained, the desorption rate is twice of that with Temperature Swing Adsorption (TSA) and the energy consumption is only 69% of that with TSA.     

An innovative dual fuel cell to capture and collect pure NO X from flue gases

Nitrogen monoxide (NO), a major air pollutant, can be directly used as a precursor for nitrogen fertilizer production as long as it is collected in a pure form. In this study, an innovative dual fuel cell system was designed for the efficient capture and collection of pure NO _X from industrial flue gases as well as for electricity generation. The system consisted of a methanol/ferric-EDTA fuel cell for NO _X capture and a ferrous-EDTA–NO/air fuel cell for captured NO _X collection. In a separation operation, the maximum power densities, which were obtained at pH 2 and 20 °C, were 785 and 1,840 mW m^?2 in FC1 and FC2, respectively, and increased with temperature. The highest overall outputs from FC1 and FC2 were measured at pH 2, a result that is possibly attributable to the redox potential difference between the anolyte and catholyte in the fuel cells. In the combined operation, ferrous-EDTA–NO prepared in the cathode compartment of FC1 was successfully and efficiently converted to ferric-EDTA and NO in the anode compartment of FC2. The present approach was considered advantageous for advanced NO _X reuse technology in the respect that valuable products, such as fertilizer, could be produced.     

Application of active coke in processes of SO2- and NOx-removal from flue gases

In the field of flue gas cleaning, active coke plays an important role as adsorbant and catalyst. In the temperature range usually prevailing downstream of the air preheater of power plants, SO₂ becomes adsorbed on carbonaceous materials and in a consecutive step is catalysed by the carbonaceous surface and converted to sulphuric acid. The quality demands for a cyclic regenerative process for SO₂ removal are fulfilled by the active coke which is used in the BF-process. The same active coke catalyses the reaction of NO with NH₃ to N₂ and steam. This is the basis for processes for simultaneous SO₂ and NO_x removal. By the addition of ammonia the SO₂ removal by active coke is improved. Two processes are described and results from the laboratory and from the demonstration plant for the BF-process are presented. These show that SO₂ removal efficiences exceed 95% and NO conversions of > 80% can be realized without problems. The cost of the processes using active coke with ammonia addition are comparable with those of wet flue gas desulphurization processes without any additional equipment should NO have to be removed.     

烟道气回收CO2的工业应用

本文阐述烟道气CO2回收技术以及榆林天然气化工有限公司回收烟道气CO2的应用总结。     

玻璃窑炉烟气脱硝脱硫除尘一体化技术

针对玻璃窑炉烟气特性和排放情况以及脱硝脱硫除尘一体化技术进行了介绍,并通过实际案例分析,对玻璃窑炉的烟气处理提出了针对性的一体化解决方案。