Stack burn

Redstone Arsenal, Ala. 50-60 pits, 100 yards long x 20 ft wide used by technical escort unit to dispose of U.S. and foreign CWM after World War II CWM stacked, burned, and buried Large quantity of CWM expected, but most are likely to be empty due to burn/ burial process significant amount of foreign CWM is expected ... 

Closed system (to vent stack, burning stack or scrubber) Open system (to atmosphere)... 

In magnesium casting, sulfur dioxide is employed as an inert blanketing gas. Another foundry appHcation is as a rapid curing catalyst for furfuryl resins in cores. Surprisingly, in view of the many efforts to remove sulfur dioxide from flue gases, there are situations where sulfur dioxide is deHberately introduced. In power plants burning low sulfur coal and where particulate stack emissions are a problem, a controUed amount of sulfur dioxide injection improves particulate removal. 

In early years the contact process frequentiy employed only two or three catalyst stages (passes) to obtain overall SO2 conversions of approximately 95—96%. Later, four pass converters were used to obtain conversions of from 97% to slightiy better than 98%. For sulfur-burning plants, this typically resulted in sulfur dioxide stack emissions of 1500—2000 ppm. 

Process air in sulfur-burning plants is dried by contacting it with 93—98 wt % sulfuric acid in a countercurrent packed tower. Dry process air is used to minimise sulfuric acid mist formation in downstream equipment, thus reducing corrosion problems and stack mist emissions. 

The soft-mud process is used to make handmade btick. Mote water is added to the clay to make a thinner paste, typicaHy about 20 to 30% by weight of water. The resulting slurry is packed into molds that have a sand or water coating on them that acts as a release agent. The wet brick shapes ate removed from the molds when they have set up enough to handle and ate then stacked for drying and burning. 

Typically, the biggest lost that occurs in chemical processes is in the combustion step (6). One-third of the work potential of natural gas is lost when it is burned with unpreheated air. Eigure 3 shows a conventional and a second law heat balance. The conventional analysis only points to recovery of heat from the stack as an energy improvement. Second law analysis shows that other losses are much greater. 

A more obvious energy loss is the heat to the stack flue gases. The sensible heat losses can be minimized by reduced total air flow, ie, low excess air operation. Flue gas losses are also minimized by lowering the discharge temperature via increased heat recovery in economizers, air preheaters, etc. When fuels containing sulfur are burned, the final exit flue gas temperature is usually not permitted to go below about 100°C because of severe problems relating to sulfuric acid corrosion. Special economizers having Teflon-coated tubes permit lower temperatures but are not commonly used. 

Not only does the material have excellent resistance to burning but smoke emission values are reported to be much less than for fire-retardant polyester resin. The laminates are being increasingly used in situations where corrosion is associated with organic media, where corrosion is encountered at temperatures above 100°C as in fume stacks and where both fire retardance and corrosion resistance are desired as in fume ducts. 

Consider coal burning in a boiler house. The assessor may not be able to measure the mass of sulfur dioxide (SOj) leaving the boiler stack, because of access problems and the lack of suitable sampling ports on the stack. The only information available is that the coal is of soft quality, containing 3% sulfur by weight and, on average, 1,000 kg of coal is burned each day. 

The stripped catalyst is picked up by a stream of air and carried into the regenerator where the carbon is burned at temperamres about 1100-1300°F. Entrained catalyst is again removed by cyclones and the flue gas goes out the stack. The hot, regenerated catalyst leaves the regenerator and takes with it much of the heat of combustion. This is carried over to the reactor to vaporize the feed and to balance the endothermic heat of cracking. Thus, the process is heat balanced. 

The purpose of a blowdown drum is to disengage closed safety valve releases and various drainage, blowdown and diverted materials into liquid and vapor streams which can be safely disposed of to appropriate storage and flaring facilities, respectively. Entrainment of liquid hydrocarbons into a flare stack is not acceptable, since the potential exists for burning liquid falling onto the ground or adjacent facilities. For this reason, a blowdown drum is required. 

It is important to note that even if the blowdown is effective in disengaging liquid and vapor, further condensation could occur downstream especially if the vented vapor exits the drum at a temperature above ambient conditions. A proportion of such condensible materials in the blowdown drum vapor release may condense as a result of cooling in the flare header and contact with seal water, and then disengage in the flare seal drum while condensible vapors which are not condensed out at this stage may condense in the flare stack or its inlet line, thus creating the potential for hazardous fallout of burning liquid from the flare. Condensed hydrocarbon in the seal drum can be entrained out with the... 

Flameholder - Flameholders are necessary to prevent the flame from "riding" up to the top of the stack. They provide a surface at which burning can take place and also promote better mixing of air and gas by the additional turbulence which they cause above the jets. Construction is simply a solid, 25 mm diameter rod of refractory material (silicon carbide) supported horizontally above each burner line. The bottom of the rod should be 13 mm above the tips of the jets. 

In the case of heavier-than-air purge gas, there is no buoyancy mechanism causing air entry into the stack, and there is thus no incentive to include a dry seal. Unlike a water seal, a dry seal cannot prevent a flashback from traveling upstream if a combustible mixture has been formed by the entry of air into the safety valve or flare headers. It only protects against internal burning flashback... 

Relieving vapors from various pressure-relief and depressuring valves in the system must be collected in individual flare headers that should be appropriately located near each process area. Subheaders must be interconnected to a main flare header which feeds to a knock- out drum and disposal system. Condensates that are carried over by vapors are separated in the knock-out drum. The vapors that exit the vessel go to the flare stack where they are burned. 

Exhaust gases from the gas turbine are used to raise steam in the lower cycle without the burning of additional fuel (Fig. 7.3) the temperatures of the gas and water/steam flows are as indicated. A limitation on this application lies in the heat recovery system steam generator choice of the evaporation pres.sure (p ) is related to the temperature difference (Tft — T ) at the pinch point as shown in the figure, and a compromise has to be reached between that pressure and the stack temperature of the gases leaving the exchanger, (and the consequent heat loss ). ... 

Leaks of process materials are the process industries biggest hazard. Most of the materials handled will not burn or explode unless mixed with air in certain proportions. To prevent fires and explosions, we must therefore keep the fuel in the plant and the air out of the plant. The latter is relatively easy because most plants operate at pressure. Nitrogen is widely used to keep air out of low-pressure equipment, such as storage tanks (Section 5.4), stacks (Section 6.1). centrifuges (Section 10.1), and equipment that is dcpressured for maintenance (Section 1.3). 

Meiler, m. circular pile (esp. that used in charcoal burning), mound, stack Brick) clamp, -kohle, /. charcoal, -verfohren, n., -ver-kohlung,/. pile charring, -verkokung,/. pile coking. 

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