Carbonaceous gases and

The chemistry of carbon, and radiocarbon, in the atmosphere represents one of the most important areas of environmental research today. The primary practical reason for this is the increasing attention which must be paid to the critical balance between energy and the environment, especially from the viewpoint of man s perturbations of natural processes and his need to maintain control. Probably more than other species, carbonaceous molecules play a central role in this balance. Some of the deleterious effects of carbonaceous gases and particles in the atmosphere are set down in Table 3. The potential effects of increased local or global concentrations of these species on health and climate have led to renewed interest in the carbon cycle and the "C02 Problem". It should be evident from the table, however, that carbon dioxide is not the only problem. In fact, the so-called "trace gases and particles" in the atmosphere present an important challenge to our interpretation of the climatic effects of carbon dioxide, itself [20]. 

The question of the compatibility of metals and alloys with carbon and carbonaceous gases has assumed considerable importance in connection with the development of the gas-cooled nuclear reactor in which graphite is used as a moderator and a constituent of the fuel element, and carbon dioxide as the coolant. Tests of up to 1 000 h on a series of metals and nickel-containing alloys under pressure contact with graphite at 1 010°C" showed that only copper was more resistant than nickel to diffusion of carbon and that the high-nickel alloys were superior to those of lower nickel content. The more complex nickel-chromium alloys containing titanium, niobium and aluminium were better than the basic nickel-chromium materials. 

The biological treatment process involves the use of microorganisms such as bacteria and fungi to convert finely divided colloidal and dissolved carbonaceous organic matter in wastewater into various gases and into cell tissues that are then removed from sedimentation tanks as flocculent settle-able organic and inorganic solids. This process often complements both physical and chemical processes and it is classified as follows. 

WSA [Wet gas sulphuric acid] A process for recovering sulfur from flue-gases and other gaseous effluents in the form of concentrated sulfuric acid. It can be used in conjunction with the SCR process if oxides of nitrogen are present too. The sulfur dioxide is catalytically oxidized to sulfur trioxide, and any ammonia, carbon monoxide, and carbonaceous combustibles are also oxidized. The sulfur trioxide is then hydrolyzed to sulfuric acid under conditions which produce commercial quality 95 percent acid. Developed by Haldor Topsoe 15 units were commissioned between 1980 and 1995. See also SNOX. 

The desorption of CO (m/e=28) and CO2 (m/e=44) was recorded by MS during the CO-TPD experiments for La(Co, Mn, Fe)i i(Cu, Pd)i03 samples. A quantitative analysis of the various carbonaceous gases desorbed from perovskites is summarized in Table 7. Both CO and CO2 desorptions were observed indicating that the oxidation of CO into CO2 occurs over those lanthanum perovskites during CO-TPD experiments. 

Carbon has been used in several forms. Activated charcoal found limited usage because of significant batch-to-batch variations. Kaiser (16) developed a carbonaceous material with pore structure similar to zeolites and referred to it as carbon molecular sieve. It is useful only for gases and very short chain compounds. It is unique in that it can be used for the analysis of oxygen, nitrogen, and carbon dioxide as shown in Figure 3.7. 

For carbonaceous gases such as CO and CH4 at relatively high temperatures (ca. > 800°C), carburization of steel surfaces takes place in the form of brittle interstitial carbides that may cause surface cracking. Cementite may also form on the surface of steel since its melting point is lower than the underlying metal, it may cause melting of the steel surface that is subsequently eroded by the gas stream. 

The other industrial kiln reactor that is examined in this chapter is the Conrad recycling process. This process uses an auger kiln reactor to transform plastic and/or tyres in the absence of oxygen into liquid petroleum, solid carbonaceous material and noncondensable gases at high temperatures. Conrad currently has two facilities in operation. They have a 200 Ib/h pilot unit and a 2000 Ib/h commercial scale unit at Chehalis research facility (Figure 19.4 shows the process diagram) [9]. 

The Conrad recycling process uses a horizontal auger kiln reactor that applies heat to plastics and/or tires in the absence of oxygen to produce liquid petroleum, solid carbonaceous material, and noncondensable gases [1-3]. The control of the pyrolysis process is decided by temperature and especially auger speed and temperature. 

---