Water vapour, emissivity

Rather different circumstances are encountered when considering THz remote sensing of extraterrestrial sources. The major source of THz opacity in the Earth s atmosphere is water vapour, and from either high, dry mountain sites or from space there are windows in which the background becomes very small. Incoherent instruments which detect the faint emission from astronomical sources can therefore be considerably more sensitive than their laboratory... 

Combustion processes are the most important source of air pollutants. Normal products of complete combustion of fossil fuel, e.g. coal, oil or natural gas, are carbon dioxide, water vapour and nitrogen. However, traces of sulphur and incomplete combustion result in emissions of carbon monoxide, sulphur oxides, oxides of nitrogen, unburned hydrocarbons and particulates. These are primary pollutants . Some may take part in reactions in the atmosphere producing secondary pollutants , e.g. photochemical smogs and acid mists. Escaping gas, or vapour, may... 

Figure 9.44. Emissivity of water vapour in a mixture of non-radiating gases at iOl.3kN/m2(54)...

The C02 stream obtained from oxy-fuel combustion shows high levels of water vapour, sulphur compounds, N 02 and impurities such as mercury in the flue gas. NOx emission is low when compared with air combustion. 

The mass of Halley s Comet is about 1014kg, and thus its mean density is only 200 kg/m3. The rate of loss of material has been estimated as 5,000 kg/s. The nucleus is loosely packed and exhibits point craters and chasms from which gas and dust escape. These emissions consist mainly of water vapour (—80% by volume) as well as 6% CO, < 3% C02, -2.5% CH4, -1.2% NH3 and < 6% N2 (Flechtig and Keller, 1987). At the point where Giotto came nearest to the comet, the estimated amount of water being ejected was close to 15,000 kg/s, while that of dust particles was between 6,000 and 10,000 kg/s. Ions derived from water were detected in the... 

Complex pyrolysis chemistry takes place in the conversion system of any conventional solid-fuel combustion system. The pyrolytic properties of biomass are controlled by the chemical composition of its major components, namely cellulose, hemicellulose, and lignin. Pyrolysis of these biopolymers proceeds through a series of complex, concurrent and consecutive reactions and provides a variety of products which can be divided into char, volatile (non-condensible) organic compounds (VOC), condensible organic compounds (tar), and permanent gases (water vapour, nitrogen oxides, carbon dioxide). The pyrolysis products should finally be completely oxidised in the combustion system (Figure 14). Emission problems arise as a consequence of bad control over the combustion system. 

Off-gas from the coke burner ( -Gas) contains nitrogen, sulphur dioxide (SO2), hydrogen sulphide (H2S), carbon monoxide (CO), carbon dioxide (CO2), water vapour and other trace contaminants. The -Gas is directed to the CO Boiler for incineration where sulphur compounds are converted to SO2. The Boiler flue gas is passed through electrostatic precipitators for particulate control and then emission to atmosphere. The CO Boiler also serves as the Sulphur Plant tail gas incinerator. Maximum sulphur emissions are 146 tonnes/day or 10.6% of sulphur contained in bitumen feed to the cokers. 

Future projected temperature changes due to greenhouse warming and their effects on water vapour and biogenic NMHC emissions. 

Abstract. The impact of future aircraft emissions on concentrations of reactive nitrogen, water vapour and ozone has been calculated using the 3-dimensional stratospheric chemical transport model SCTM-1. Emissions of NOx (N0+N02) and H20 from both sub- and supersonic aircraft have been considered. 

The scenarios for aircraft emissions are from the NASA data base [1]. Emissions of NOx and water vapour from sub- and supersonic aircraft were considered. For the projected fleet of 500 supersonic aircraft, different emission indices for NOx and cruising altitudes were assumed. 

Night-time emission rates in rural and urban areas are listed in Table I together with initial concentrations and land deposition velocities. The initial concentrations were chosen to reflect unpolluted air arriving at the West Coast of England. Methane is assumed to be present in the atmospheric boundary layer at a constant concentration of 1.6 ppm. Water vapour is also assumed to be invariant in rural and urban air at a concentration of 104 ppm. This corresponds to ca. 60% relative humidity at 288 K. The initial concentration and emission over land of DMS have been taken to be zero as have all other species in the chemical scheme which are not listed in Table I. Emissions over land of NO, SO hydrocarbons, CO and H are subject to diurnal variation and this has been treated as before (13.141. Rural emission rates are assumed to prevail throughout the traversal of Scandinavia. All species are assumed to be hilly mixed within an atmospheric boundary layer of constant depth, taken to be... 

The glow is exhibited by ordinary phosphorus trioxide,2 but is then really due to small quantities of dissolved phosphorus. The oxide when purified as described on p. 126 gave only a momentary glow at the commencement of the oxidation (by oxygen), which afterwards proceeded without emission of light. The glow of phosphorus, which actually is inhibited by the trioxide, is restored continuously as this is hydrated by small amounts of water vapour.3 The inhibitory effect of P4Og is also removed by ozone. 

By the compression of 1 gr. of saturated water vapour at 100° to saturated water vapour at 101°, we have an emission of 1-2 cal. If this heat is not allowed to escape, we do not obtain saturated water vapour at 101°, but superheated steam at a correspondingly higher temperature. Conversely, if we allow saturated water vapour to expand adiabatically, condensation takes place. We may mention that this spontaneous condensation of water vapour, which for a slight expansion takes place only in the presence of dust particles or ions, has been successfully employed in counting the number of ions or nuclei in the vapour. 

As can be seen from the gas analysis in Figure 4 there is also a peak in CO- and a dip in CO2 -emissions followed by a peak in CO2 while CO goes to zero. The peak in CO coincides with a dip in temperature. When char combustion starts the production of water vapour from drying and combustion falls and the CO-emission increases because of lack of water vapour for CO-oxidation as illustrated by the expression -d[CO]/dt = ko[COJ[02] [H20] cxp(-E/RT> from Howard (9). The final increase in CO2 follows from an increase in 02-concentration, enhancing combustion, when the bed is almost finished and very shallow. This dip-and-peak behaviour is not seen at high air mass flows (above 0.17 kg/m s for wood cylinders and above 0.40 kg/m s for pellets). 

Hydroxyl emission sources have been applied also in shock tube studies of hydroxyl radical reactions " . In this case the required time resolution (see refs. 18, 19) was obtained by using a flash discharge in water vapour. Similar methods have been described in which the Cj Swan bands are excited by a discharge in butane . 

Fig. 5.75 Total emissivity h2o f°r water vapour at p = 1 bar, extrapolated to pu2o — 0, as a function of temperature T, with the product of the partial pressure pe2o and the mean beam length sm as parameter. 1 bar = 100 kPa = 0.1 MPa...

For mass production of hydrogen, tlie most cost-effective and widely used process is currently the reforming of natural gas by water vapour. A production method using nuclear power, by high-temperature electrolysis or themiochemical cycles, would meet the requirements of sustainable development, both in resources and in polluting gas emissions. The technical feasibility of these solutions remains to be demonstrated, as does their economic feasibility. 

Indoor combustion sources are related mainly to cooking, heating and tobacco smoking. In addition, outdoor combustion products, which in urban environments originate most commonly from vehicle emissions, penetrate inside and contribute to indoor pollution. Under ideal conditions, complete combustion of carbon results only in the generation of CO2 and water vapour. Any products other than CO2 are often called products of incomplete combustion and include particulate matter and gases. 

Decomposition of water vapour inside the gas film by the electrochemical discharges by energy transfer resulting in the formation of hydrogen and excess oxygen. This mechanism is probably responsible for the observation of H lines and OH bands in the emission spectra. 

It follows from this discussion that the inadvertent ozone depletion in the past and at present is not expected to be measurable. This conclusion is supported by observational data on total ozone showing a net increase during recent years. This is confirmed by observations carried out at various places on the Earth s surface. Thus, according to Komhyr et al. (1971) between 1958 and 1970 the rate of this increase has been as large as several percent per decade (see Fig. 57). It is to be noted in this respect that Mastenbrock (1971) found that the stratospheric water vapour burden over the U.S.A. also increased significantly in recent years and this was attributed to the water vapour emission of supersonic aircraft. In Subsection 3.4.3 we mentioned that free radicals formed from water vapour can play a certain role in... 

---