Chemical apparatus and process disinfecting – deodorizing – preser – Chemical reactor – Waste gas purifier
Patent
1985-09-26
1987-07-21
Chiesa, Richard L.
Chemical apparatus and process disinfecting, deodorizing, preser
Chemical reactor
Waste gas purifier
55 73, 55222, 55240, 55269, 165 60, 165133, 1651341, 208 47, 261 3, 261153, 261DIG9, 422200, B01D 5334
Patent
active
046817441
DESCRIPTION:
BRIEF SUMMARY
The invention is related to a heat recovery device to recover heat from corrosive gases such as sulphurous flue gases and/or flue gases containing organic acids, said corrosive gases being conducted through a primary side of heat exchanger means provided in a gas duct.
When oil, coal and similar sulphurous fuels are burned, the flue gases emitted therefrom will typically bring with them about 10-15 percent of the combustion heat of the fuel. Therefore, great efforts are made to cool said flue gases in order to recover as much energy as possible. However, corrosion problems occur in the heat exchangers through which said flue gases are conducted. It is known that the greatest corrosion effects on the surfaces of said heat exchanger means occur when the temperature of said surfaces being in contact with said flue gases is lowered past the acid dew point and until the temperature passes the water dew point.
Recovering a large portion of the heat of the flue gases requires, for many common fuels, that the flue gases are cooled well below the acid dew point, which necessitates that the consequent corrosion problems be managed. In known applications the surfaces of heat exchangers placed in a flue gas duct are protected from a corrosion attack by using glass, ceramics or other corrosion resistant materials in the heat exchangers. However, such heat exchangers are expensive and difficult to manufacture, due, e.g., to sealing problems at the tube ends.
When less expensive heat exchangers of metal are used, the main problem heretofore has been to protect the surfaces of the cooling devices and, therefore, a great demand exists for an improved method to recover as much energy as possible.
By spraying water into the flue gases, it is possible to increase the water dew point of the flue gases. It can be shown that this will decrease the acid concentration of the condensing acid drops, when formed on the cooling surfaces. However, when spraying water into the flue gases and/or onto the cooling surfaces, the temperature of the flue gases is lowered substantially, thus increasing the portion of low grade waste heat (below water dew point) at the expense of the more valuable waste heat initially available at higher temperatures.
The energy which can be recovered from the flue gases by heat exchanging is a function of the enthalpy of the flue gases. The total enthalpy can, with sufficient practical accuracy, be written as i.sub.tot =i.sub.dry +i.sub.wet, where i.sub.dry is the energy due to dry heat, and i.sub.wet is the condensation heat of the water wapor.
Accordingly, a main object of the invention is to provide a versatile heat recovery method and device which, in general application, permits both i.sub.dry and i.sub.wet to be recovered with as small restrictions as possible with respect to the thermo-technical aspects. The ideal thermo-technical characteristics must not be sacrificed for the corrosion aspects.
This object is achieved according to the invention by means of a heat recovery device, which is characterized in that said heat exchanger means are provided with means for repeatedly applying, during normal operation of said heat exchanger means, a protective controllable thin layer onto the surfaces of said heat exchanger means, at least when the temperature of said corrosive gases exceeds the water dew point, in order to protect said surfaces from corrosion.
While primarily aiming at a thermodynamically efficient and, from a practical point of view, very flexible and versatile method and equipment for heat recovery from the flue gases, the invention also incorporates methods and means for removing, from the flue gases, environmentally hazardous substances, like SO.sub.2. Said cleaning of the flue gases is accomplished by using the second stage of the recovery system as a combined heat exchanger and a wet scrubber,. The scrubbing liquid may, whenever alkaline waste waters are available, be the alkaline waste water itself, thereby providing a possibility to neutralize alkaline waste waters before being discharge
REFERENCES:
patent: 2280633 (1942-04-01), Crawford
patent: 2798570 (1957-07-01), Kelley
patent: 2911351 (1959-11-01), Hill
patent: 3522000 (1970-07-01), Kinney
patent: 3844740 (1974-10-01), Brandt
patent: 3927153 (1975-12-01), Tarhan
patent: 4287938 (1981-09-01), Lagerquist et al.
patent: 4305909 (1981-12-01), Willett et al.
LandOfFree
Heat recovery device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Heat recovery device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Heat recovery device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-206335