Direct Exhaustion Process

Exhaust Gases Table IV shows the analytical results of exhaust gas from drying-pyrolysis process and from direct pyrolysis process and incineration process on cake A, 3 to 83 % of S in the fed cake remains in the residue, 17 to 51 % of S converts... 

A novel fuel processor is configured at NETL to integrate the fuel cell system for process optimization and system control. In the proposed system, startup occurs by firing an internal combustor in the dual reactor reformer, which provides heat to the ATR reformer via conduction as well as supplying heat to the fuel cell cathode via direct exhaust from the combustor. 

The output from the turbine might be superheated or partially condensed, as is the case in Fig. 6.32. If the exhaust steam is to be used for process heating, ideally it should be close to saturated conditions. If the exhaust steam is significantly superheated, it can be desuperheated by direct injection of boiler feedwater, which vaporizes and cools the steam. However, if saturated steam is fed to a steam main, with significant potential for heat losses from the main, then it is desirable to retain some superheat rather than desuperheat the steam to saturated conditions. If saturated steam is fed to the main, then heat losses will cause excessive condensation in the main, which is not desirable. On the other hand, if the exhaust steam from the turbine is partially condensed, the condensate is separated and the steam used for heating. 

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). 

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,...

Exhaust emissions of CO, unbumed hydrocarbons, and nitrogen oxides reflect combustion conditions rather than fuel properties. The only fuel component that degrades exhaust is sulfur the SO2 concentrations ia emissions are directly proportional to the content of bound sulfur ia the fuel. Sulfur concentrations ia fuel are determined by cmde type and desulfurization processes. Specifications for aircraft fuels impose limits of 3000 —4000 ppm total sulfur but the average is half of these values. Sulfur content ia heavier fuels is determined by legal limits on stack emissions. 

Precious Meta.1 Ca.ta.lysts, Precious metals are deposited throughout the TWC-activated coating layer. Rhodium plays an important role ia the reduction of NO, and is combiaed with platinum and/or palladium for the oxidation of HC and CO. Only a small amount of these expensive materials is used (31) (see Platinum-GROUP metals). The metals are dispersed on the high surface area particles as precious metal solutions, and then reduced to small metal crystals by various techniques. Catalytic reactions occur on the precious metal surfaces. Whereas metal within the crystal caimot directly participate ia the catalytic process, it can play a role when surface metal oxides are influenced through strong metal to support reactions (SMSI) (32,33). Some exhaust gas reactions, for instance the oxidation of alkanes, require larger Pt crystals than other reactions, such as the oxidation of CO (34). 

Dearation can be either vacuum or over pressure dearation. Most systems use vacuum dearation because all the feedwater heating can be done in the feedwater tank and there is no need for additional heat exchangers. The heating steam in the vacuum dearation process is a lower quality steam thus leaving the steam in the steam cycle for expansion work through the steam turbine. This increases the output of the steam turbine and therefore the efficiency of the combined cycle. In the case of the overpressure dearation, the gases can be exhausted directly to the atmosphere independently of the condenser evacuation system. 

The pH of rainwater is normally about 6 but can be reduced significantly by absorption of acidic exhaust gases from power stations, industrial combustion or other processes, and vehicles. Acids may also enter the waterways as a component of industrial effluent. In addition to the direct adverse effects on aquatic systems (Table 16.12) low pH can result in the leaching of toxic metals from land, etc. 

The specific problems for BEOs are mostly related to the specific processes at which they are used. One problem that does not, directly, depend on the process is the use of the exhaust system. If an exhaust is not used, naturally it cannot remove contaminants. Although BEOs are less efficient than total or partial booths, their use is still justified. When the location of the BEO is not perfect, higher flow rates are usually required for contaminant control. However, it is better to use this type of hood than to have no local exhaust. 

Capture opening(s) locations should be chosen to take advantage of the initial release direction of the contaminant. This leads to locating exhaust openings in the back, floor, ceiling (e.g., for heat-emitting processes), or side walls of the booth. In many cases it is useful to combine exhaust openings in different sides of the booth. 

Simple exhaust hoods have a very short effective range and the hood must be placed very close to the contaminant source to be efficient, which may interfere with technological processes. This lack of direction of the flow may result in the use of excessive exhaust flow rates with large source-to-hood distances and this may result in a large amount of wasted energy. 

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