Gases exhaust

The lead alkyls and scavengers contained in fuels cause rapid poisoning ol exhaust gas catalytic converters. They are tolerated only in trace quantities in fuels for vehicles having that equipment. The officially allowed content is 0.013 g Pb/1, but the contents observed in actual practice are less than 0.005 g Pb/1. 

Outside of carbon monoxide for which the toxicity is already well-known, five types of organic chemical compounds capable of being emitted by vehicles will be the focus of our particular attention these are benzene, 1-3 butadiene, formaldehyde, acetaldehyde and polynuclear aromatic hydrocarbons, PNA, taken as a whole. Among the latter, two, like benzo [a] pyrene, are viewed as carcinogens. Benzene is considered here not as a motor fuel component emitted by evaporation, but because of its presence in exhaust gas (see Figure 5.25). 

Type of pollutant Weight % of volatile organic compounds contained In exhaust gas Relative risk factor... 

Evaluation of the concentrations of four toxic pollutants in exhaust gas (ordeA of magnitude). ... 

To estimate the effect of automobile traffic and motor fuels on ozone formation, it is necessary to know the composition of exhaust gas in detail. Figure 5.26 gives an example of a gas phase chromatographic analysis of a conventional unleaded motor fuel. 

Example of an analysis of exhaust gas by gas phase chromatography and j relative reactivity of effluents with respect to tropospheric ozone formation. I... 

Exhaust gas temperature sensor Catalytic substrate Heat insulator... 

Heat and oil resistance coupled with its low swell have led automotive apphcations into laminated tubing and hoses (11) with this material. This resistance to the effects of ASTM No. 3 oil at service temperatures of 200°C makes it competitive with fluorocarbons and with the tetrafluoroethylene—propylene copolymer. Fluorosihcones are used to make exhaust gas recirculation (EGR) diaphragms for some passenger cars. 

Catalytic Incinerators. Catalytic incinerators, often used to remove hydrocarbons from exhaust gas streams, are more compact than direct-flame incinerators, operate at lower temperatures, often require Htfle fuel, and produce Httle or no NO from atmospheric fixation. However, the catalytic bed must be preheated and carefliUy temperature controlled. Thus these are generally unsuited to intermittent and highly variable gas flows. 

However, rotary furnaces tend to produce more exhaust gas and fumes, require more skill fill manipulation, and are more labor intensive. Also, the slags produced in the rotary furnaces, soda or fayaUte [13918-37-1] slags, normally do not pass the toxic characteristic leach procedure (TCLP) test and pose a disposal problem. 

Miscellaneous Kilns. A U.S. kiln, the Fluo-Sohds, appears to be another vertical kiln type, but this is its only similarity. It operates on a different principle. It utilizes as kiln feed only a discrete granulation of 0.225—2.4 mm (65—8 mesh) sizes. DeHcately controlled by air and exhaust gas pressure, the kiln feed of granules is fluidized as a dense suspension. Because it is instmmented, this kiln can produce a very reactive lime at better than average thermal efficiency. The kiln, however, has limited utifity because the cost of obtaining the kiln feed with many hard, compact limestones is prohibitive. 

Chemical Regeneration. In most MHD system designs the gas exiting the toppiag cycle exhausts either iato a radiant boiler and is used to raise steam, or it exhausts iato a direct-fired air heater and is used to preheat the primary combustion air. An alternative use of the exhaust gas is for chemical regeneration, ia which the exhaust gases are used to process the fuel from its as-received form iato a more beaeftcial oae. Chemical regeaeratioa has beea proposed for use with aatural gas and oil as well as with coal (14) (see Gas, natural Petroleum). 

Hydrochloric acid [7647-01-0], which is formed as by-product from unreacted chloroacetic acid, is fed into an absorption column. After the addition of acid and alcohol is complete, the mixture is heated at reflux for 6—8 h, whereby the intermediate malonic acid ester monoamide is hydroly2ed to a dialkyl malonate. The pure ester is obtained from the mixture of cmde esters by extraction with ben2ene [71-43-2], toluene [108-88-3], or xylene [1330-20-7]. The organic phase is washed with dilute sodium hydroxide [1310-73-2] to remove small amounts of the monoester. The diester is then separated from solvent by distillation at atmospheric pressure, and the malonic ester obtained by redistillation under vacuum as a colorless Hquid with a minimum assay of 99%. The aqueous phase contains considerable amounts of mineral acid and salts and must be treated before being fed to the waste treatment plant. The process is suitable for both the dimethyl and diethyl esters. The yield based on sodium chloroacetate is 75—85%. Various low molecular mass hydrocarbons, some of them partially chlorinated, are formed as by-products. Although a relatively simple plant is sufficient for the reaction itself, a si2eable investment is required for treatment of the wastewater and exhaust gas. 

Fig. 8. Combustion turbines with process heat recovery (a) represents direct use of exhaust gas for process heating where industrial process includes refinery, chemicals, food processing, and ethanol production and (b) exhaust-to-water heat exchanger where industrial process includes material drying,...

Continuous Emissions Monitoring. A key aspect of the new CAAA is the requirement that plants prove their continued compHance to new emissions limits by installing continuous emissions monitoring systems (CEMs). The CAAA imposes new requirements for monitoring NO, SO2, and CO2 levels in a plant s exhaust gas stream. Affected plants typically must gather data from stack monitoring systems, gas analyzers, and the plant s data acquisition system and provide the data in a format approved by the EPA and state regulators. CEM systems must be in place by November 1993 for boilers affected by Phase I of the CAAA, and byjanuary 1995 for plants impacted by Phase II. 

A further enhancement to the HRS process whereby the exhaust from a gas fired turbine is used to superheat steam from the HRS process is also possible (129). The superheated steam is then fed through a turbogenerator to produce additional electricity. This increases the efficiency of heat recovery of the turbine exhaust gas. With this arrangement, electric power generation of over 13.6 kW for 1 t/d (15 kW/STPD) is possible. Good general discussions on the sources of heat and the energy balance within a sulfuric acid plant are available (130,131). 

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