Combined Non-Catalytic Reduction of NOx and SO2 by Ammonia Liquor during Staged Fluidized-Bed Combustion

Emissions of NOx and SO2 were monitored in the presence of ammonia liquor in a 0.09 m2 and 2 m high stainless-steel fluidized-bed combustor. Experiments were carried out at 2 m/s fluidizing velocity, 40% excess air, and 870 °C bed temperature. Ammonia liquor with 7% ammonia by weight was injected into the freeboard of the combustor 52 cm above the distributor through a water-cooled injector. A 65 : 34 primary/secondary air ratio was maintained throughout the investigation. Approximately 70% of NO and 20% of SO2 was reduced at an NH3/NO molar ratio of 2 : 1, respectively. However, a higher reduction in SO2 emissions (62%) was achieved at a very high NH3/NO molar ratio of 7 : 1. These experiments showed that ammonia addition did have a significant effect in SO2 reduction if injected in an excess amount. The injection of ammonia liquor combined with staged combustion was found to be very effective in reducing NOx emissions. A reduction of about 50% was achieved at an NH3/NO molar ratio of 0.6 : 1 which is also coupled with a very low level of ammonia in the flue.     

Reduction of SO2 Emissions by Ammonia Gas During Staged Combustion

To reduce SO2 emissions, ammonia gas was injected into a coal-fired fluidized-bed combustor under staged commbustion condition. The combustor was 2 m high with a 30 cm static bed height and a freeboard height of 170 cm. The ammonia gas was injected at 52 cm and 65 cm above the distributor, which had a temperature of ca. 700 °C, by an uncooled stainless-steel tube injector. The experiments investigated the effects of ammonia gas injection on sulphur dioxide emissions at staged conditions, varying the: (i) excess air level, (ii) secondary air ratio, (iii) fluidizing velocity, (iv) ammonia injection position, and (v) the ammonia : sulphur dioxide molar ratio.A maximum reduction of 66% in SO2 emissions was found at 40% excess air, 65 : 35 staging, 1.5 m/s fluidizing velocity, 65 cm injection height, and an NH3 : SO2 molar ratio of 1.2. The onset of SO2 reduction occurred at an NH3 : SO2 ratio of 0.5. The fluidizing velocity, excess air, level of staging, and ammonia injection height all have a significant influence on SO2 reduction.It is difficult to determine how the SO2 reduction varies with the operating conditions when ammonia is injected in the high temperature zone of the combustor. As sulphur oxides-ammonia reactions are low temperature reactions, the findings confirm the occurrence of reactions above the freeboard or near the exit to the cyclone.     

Greenhouse gas emissions from Australian open-cut coal mines: contribution from spontaneous combustion and low-temperature oxidation

Spontaneous combustion and low-temperature oxidation of waste coal and other carbonaceous material at open-cut coal mines are potentially significant sources of greenhouse gas emissions. However, the magnitude of these emissions is largely unknown. In this study, emissions from spontaneous combustion and low-temperature oxidation were estimated for six Australian open-cut coal mines with annual coal production ranging from 1.7 to more than 16 Mt. Greenhouse emissions from all other sources at these mines were also estimated and compared to those from spontaneous combustion and low-temperature oxidation. In all cases, fugitive emission of methane was the largest source of greenhouse gas; however, in some mines, spontaneous combustion accounted for almost a third of all emissions. For one mine, it was estimated that emissions from spontaneous combustion were around 250,000 t CO₂-e per annum. The contribution from low-temperature oxidation was generally less than about 1% of the total for all six mines. Estimating areas of spoil affected by spontaneous combustion by ground-based surveys was prone to under-report the area. Airborne infrared imaging appears to be a more reliable method.     

Seasonal characteristics of SO2, NO2, and CO emissions in and around the Indo-Gangetic Plain

Anthropogenic emissions of sulfur dioxide (SO₂), nitrogen dioxide (NO₂), and carbon monoxide (CO) exert significant influence on local and regional atmospheric chemistry. Temporal and spatial variability of these gases are investigated using surface measurements by the Central Pollution Control Board (India) during 2005–2009 over six urban locations in and around the Indo-Gangetic Plain (IGP) and supported using the satellite measurements of these gases. The stations chosen are Jodhpur (west of IGP), Delhi (central IGP), Kolkata and Durgapur (eastern IGP), Guwahati (east of IGP), and Nagpur (south of IGP). Among the stations studied, SO₂ concentrations are found to be the highest over Kolkata megacity. Elevated levels of NO₂ occur over the IGP stations of Durgapur, Kolkata, and Delhi. Columnar NO₂ values are also found to be elevated over these regions during winter due to high surface concentrations while columnar SO₂ values show a monsoon maximum. Elevated columnar CO over Guwahati during pre-monsoon are attributed to biomass burning. Statistically significant correlations between columnar NO₂ and surface NO₂ obtained for Delhi, Kolkata, and Durgapur along with very low SO₂ to NO₂ ratios (≤0.2) indicate fossil fuel combustion from mobile sources as major contributors to the ambient air over these regions.     

The effect of metals and ammonia on SO2 oxidation to sulphates in the ambient air

The effect of metals and ammonia on the relationship between mass concentrations of sulphur dioxide and sulphate in the air was studied near an aluminium plant over a 1-year period. Sulphur dioxide, sulphates and ammonia in the air as well as metals (Pb, Fe, Mn, Zn, Cu, Cd and Al) in the deposit were measured at four measuring sites.The levels of mass concentrations of SO₂ were low at all measuring sites while the levels of mass concentrations of sulphates in the air and concentrations of metals in the deposit were high. The levels of ammonia were found to decrease in relationship to the distance from the source of pollution.The relationship between the mass concentrations of sulphate and SO₂ can be described by the equation y=ax ^b ;where y is the percentage of sulphate sulphur in the total sulphur (sulphate and SO₂) and x is the mass concentration of the total sulphur in the air. The values of the coefficients a and b are characteristic of individual areas.As the results show the coefficients a and b obtained at a measuring site close to the plant and outside the urban area are characteristic of an industrial area. At control sites in the urban area the coefficients are characteristic of an urban area. At the measuring site close to the industrial zone and the centre of the urban area the interaction of the effects occurs. Therefore, the coefficient a is characteristic of an urban area and b of an industrial one.     

Non-CO2 gaseous emissions from upstream oil and gas operations in Nigeria

The Nigerian crude oil is formed in association with natural gas. The associated gas has mostly been flared in the process of crude oil exploitation. Current estimates are that approximately 70% of produced natural gas is flared. Carbon monoxide, volatile organic compounds and nitrogen oxides emissions from oil and gas exploitation activities are presented for major combustion activities: gas flares and power generation at oil fields for oil and gas gathering systems. The emissions rates and combustion efficiency for a newly tested modified flaring system with enhanced air supply and liquid aspiration system for the atomization of the condensate phases of the flared gas was found to be capable of improving combustion efficiency by 20% or more in comparison with the conventional flare-type currently in vogue. Flare emissions for CO and NO_x are an order of magnitude higher than other sources in the oil and gas sector.     

Long-term relationships between SO2 and NOx emissions and SO4(2-) and NO3- concentration in bulk deposition at the Hubbard Brook Experimental Forest, NH

A highly significant second-order polynomial relation between SO(2) emissions and SO(4)(2-) concentrations during 1970-2000 (r(2)= 0.80, p= <0.001), and a linear relation between NO(x) and NO(3)(-) concentrations during 1991-2000 (r(2)= 0.67, p= 0.004) in bulk precipitation were found for the Hubbard Brook Experimental Forest, NH based on emissions from a 24 h, back-trajectory determined source area. Earlier periods (1965-1980) for SO(2)ratio SO(4)(2-) and longer periods (1965-2000) for NO(x)ratio NO(3)(-) had poorer linear relations, r(2)= 0.03, p= 0.51 and r(2)= 0.22, p= 0.004, respectively. Methodology by the US Environmental Protection Agency for calculating emissions data during this period has changed significantly and frequently, making trend analysis difficult. Given the large potential for errors in estimating emissions and to a lesser extent, deposition, the robust relations between SO(2) emissions and SO(4)(2-) concentrations in bulk precipitation at the Hubbard Brook Experimental Forest show that careful, long-term measurements from a single monitoring site can provide sound and reasonable data on trends in air pollution.     

Monitoring and dispersion modelling of emissions from the fluidised bed combustion of poultry litter

Gaseous emissions from the fluidised bed combustion of chickenlitter were monitored and recorded. Emission data was used tocreate a dispersion model for a proposed site on a poultry farmin Limerick, Ireland. Variables within the combustion unit notonly influenced combustion but also emission levels ofpollutants such as SO₂ and NO_x. CO emissions decreased withuse of the correct ratio between fluidising and secondary air,the staging of secondary air and the degree of turbulence withwhich the secondary air is introduced. Dispersion modelling ofactual combustion at a proposed poultry unit predicted thatground level concentrations for the set of emissions data wouldbe below the limits and guidelines set by air quality standards.This was true for both and line source. Line sourceconcentration levels were less than those for point source.     

二氧化硫光谱检测技术

介绍了二氧化硫的性质,综述了紫外荧光分析检测技术、长程吸收光谱检测技术、激光红外吸收检测技术和遥感傅里叶变换红外光谱检测技术的原理及在二氧化硫检测中的应用。     

EDTA容量法测定硫酸根离子的误差分析

系统分析了ＥＤＴＡ容量法测定硫酸根离子的误差产生环节,并对各个环节提出了相应的误差控制办法。文中着重分析了由移液过程和滴定过程所产生的误差,最后指出,作为测定硫酸根离子的方法标准,ＥＤＴＡ容量法无法保证应有的精度,应由离子色谱法取代之     

离子色谱法同时测定大气中二氧化硫和氮氧化物

建立以2.2mmol/L的Na2CO3和2.7mmol/L的NaHCO3的混合溶液为吸收液,同时串联两个大气采样瓶采样,第一个采样瓶的吸收液内含质量体积比为0.05%的乙二胺四乙酸二钠盐(EDTA)吸收大气中SO2和NO2,第二个采样瓶的吸收液中内舍质量体积比为0.9%的过氧化氢采集大气中的NO,采样后用离子色谱法测定,若用10ml吸收液,采样体积为30L时,SO2的检出限为0.004mg/m3,可测浓度范围为0.03～26.7mg/m3;NO2的检出限为6.7×10-4mg/m3,可测浓度范围为0.03～20mg/m3.方法简便快速、准确、选择性好,完全满足环境监测对大气中二氧化硫和氮氧化物的同时测定.     

Estimation of green house gas emissions from Koteshwar hydropower reservoir,India

The emissions of greenhouse gas (GHG) from soils are of significant importance for global warming. The biological and physico-chemical characteristics of soil affect the GHG emissions from soils of different land use types. Methane (CH₄), nitrous oxide (N₂O), and carbon dioxide (CO₂) production rates from six forest and agricultural soil types in the Koteshwar hydropower reservoir catchments located in the Uttarakhand, India, were estimated and their relations with physico-chemical characteristics of soils were examined. The samples of different land use types were flooded and incubated under anaerobic condition at 30 °C for 60 days. The cumulative GHG production rates in reservoir catchment are found as 1.52 ± 0.26, 0.13 ± 0.02, and 0.0004 ± 0.0001 μg g soil^?1 day^?1 for CO₂, CH₄, and N₂O, respectively, which is lower than global reservoirs located in the same eco-region. The significant positive correlation between CO₂ productions and labile organic carbon (LOC), CH₄ and C/N ratio, while N₂O and N/P ratio, while pH of soils is negatively correlated, conforms their key role in GHG emissions. Carbon available as LOC in the reservoir catchment is found as 3–14% of the total ?C” available in soils and 0–23% is retained in the soil after the completion of incubation. The key objective of this study to signify the C, N, and P ratios, LOC, and pH with GHG production rate by creating an incubation experiment (as in the case of benthic soil/sediment) in the lab for 60 days. In summary, the results suggest that carbon, as LOC were more sensitive indicators for CO₂ emissions and significant C, N, and P ratios, affects the GHG emissions. This study is useful for the hydropower industry to know the GHG production rates after the construction of reservoir so that its effect could be minimized by taking care of catchment area treatment plan.     

Comparison of mass concentrations of SO2 determined in air by two different methods

Mass concentrations of sulphur dioxide were determined in parallel 24-hour samples of ambient air at a measuring site in Zagreb during a period of eight years. The methods used were the West-Gaeke's tetrachloromercurate-pararosaniline method (TCM) and the Standard British Method (SBM). Total results for the annual intervals of measuring were analyzed statistically and also discussed separately for winter and summer periods, in order to see whether they are influenced by seasonal rhythm.     

乌鲁木齐市煤改气工程对采暖期 SO2和 NO2浓度变化的影响分析

通过对乌鲁木齐市2011-2013年采暖期SO2、NO2、PM10的年均浓度、月均浓度、日均浓度的变化比较,分析了乌鲁木齐市煤改气工程实施前后大气环境发生的变化趋势,论证了乌鲁木齐市煤改气工程对城市大气环境的改善作用,为该工程今后的推广与发展得到了可靠的实践依据。     

SO2 modeling in İzmit Gulf, Turkey during the winter of 1997: 3 cases

In this study, SO₂ dispersion over İzmit Gulf is simulated by California Puff (CALPUFF) model for three air pollution cases, which occurred on January 28, February 12, and February 26, 1997. These days are generally characterized by dominant high-pressure systems – pressure values reaching 1032 mb, low wind speeds and sometimes calm conditions, and low temperatures with a minimum of 0°C. Hourly simulations during those critical cases were carried out and results revealed very high concentrations of SO₂ transported to the downwind regions of Tüpraş and Gebze, and values sometimes exceeded 1,000 μg/m³. Nighttime and morning simulations associated with inversion produced considerably higher values of SO₂ than the afternoon simulations associated with breeze. Model verification was conducted by comparing the measured daily average values of eight stations with the model predicted values at the same receptor points. Results showed that the model well predicted the values at station Gebze in all three cases. The model sometimes underestimated and sometimes overestimated the concentrations at other receptor stations.     

分光光度比浊法测定氢氟酸中SO2-4

在混合稳定剂的存在下,利用BaSO4的比浊法测定氢氟酸中的SO2-4.SO2-4浓度在0-50mg/L保持线性,最低检出量为1mg/L.该方法已用于实际样品的测定.     

Methane emissions of differently fed dairy cows and corresponding methane and nitrogen emissions from their manure during storage

This study investigated the effects of supplementing 40 g lauric acid (C₁₂) kg^-1 dry matter (DM) in feed on methane emissions from early-lactating dairy cows and the associated effects on methane, nitrous oxide and ammonia release from the manure during storage. Stearic acid (C₁₈), a fatty acid without assumed methane-suppressing potential in the digestive tract of ruminants, was added at 40 g kg^-1 DM to a control diet. The complete feed consisted of forage and concentrate in a ratio of 1.5:1 (DM basis). The manure was stored for 14 weeks either as complete slurry or, separately, as urine-rich slurry and farmyard manure representing two common storage systems. Methane release of the cows, as measured in respiratory chambers, was lower with C₁₂ by about 20%, but this was mostly resulting from a reduced feed intake and, partly, from a lower rate of fibre digestion. As milk yield declined less than feed intake, methane emission per kg of milk was significantly lower with C₁₂ (11.4 g) than with C₁₈ (14.0 g). Faeces of C₁₂-fed cows had a higher proportion of undigested fibre and accordingly methane release from their manure was higher compared with the manure obtained from the C₁₈-fed cows. Overall, manure-derived methane accounted for8.2% and 15.4% of total methane after 7 and 14 weeks of storage, respectively. The evolution of methane widely differed between manure types and dietary treatments, with a retarded onset of release in complete slurry particularly in the C₁₂ treatment. Emissions of nitrous oxide were lower in the manures from the C₁₂ treatment. This partially compensated for the higher methane release from the C₁₂ manure with respect to the greenhouse gas potential. The total greenhouse gas potential (cow and manure together) accounted for 8.7 and 10.5 kg equivalents of CO₂ cow^-1 d^-1with C₁₂ and C₁₈, respectively. At unaffected urine-N proportion ammonia and total nitrogen losses from stored manure were lower with C₁₂ than with C₁₈ corresponding to the differences in feed and nitrogen intake. The present results suggest that manure storage significantly contributes to total methane emission from dairy husbandry, and that the identification of effective dietary mitigation strategies has to consider both the digestive tract of the animals and the corresponding manure.     

Availability of disaggregated greenhouse gas emissions from beef cattle production: A systematic review

Agriculture is a significant source of anthropogenic greenhouse gas (GHG) emissions, and beef cattle are particularly emissions intensive. GHG emissions are typically expressed as a carbon dioxide equivalent (CO₂e) ‘carbon footprint’ per unit output. The 100-year Global Warming Potential (GWP₁₀₀) is the most commonly used CO₂e metric, but others have also been proposed, and there is no universal reason to prefer GWP₁₀₀ over alternative metrics. The weightings assigned to non-CO₂ GHGs can differ significantly depending on the metric used, and relying upon a single metric can obscure important differences in the climate impacts of different GHGs. This loss of detail is especially relevant to beef production systems, as the majority of GHG emissions (as conventionally reported) are in the form of methane (CH₄) and nitrous oxide (N₂O), rather than CO₂. This paper presents a systematic literature review of harmonised cradle to farm-gate beef carbon footprints from bottom-up studies on individual or representative systems, collecting the emissions data for each separate GHG, rather than a single CO₂e value. Disaggregated GHG emissions could not be obtained for the majority of studies, highlighting the loss of information resulting from the standard reporting of total GWP₁₀₀ CO₂e alone. Where individual GHG compositions were available, significant variation was found for all gases. A comparison of grass fed and non-grass fed beef production systems was used to illustrate dynamics that are not sufficiently captured through a single CO₂e footprint. Few clear trends emerged between the two dietary groups, but there was a non-significant indication that under GWP₁₀₀ non-grass fed systems generally appear more emissions efficient, but under an alternative metric, the 100-year global temperature potential (GTP₁₀₀), grass-fed beef had lower footprints. Despite recent focus on agricultural emissions, this review concludes there are insufficient data available to fully address important questions regarding the climate impacts of agricultural production, and calls for researchers to include separate GHG emissions in addition to aggregated CO₂e footprints.     

极大负压条件下定电位电解法测定SO2

针对用定电位电解法SO2测定仪测定高负压排气管道中SO2时测定值偏低及无法测定等问题进行了探讨,并提出可行的解决方案。