Liquid heaters and vaporizers – Indirectly heated separate injected fluid – Submerged flame
Reexamination Certificate
2000-03-20
2001-05-01
Wilson, Gregory (Department: 3749)
Liquid heaters and vaporizers
Indirectly heated separate injected fluid
Submerged flame
C122S018300
Reexamination Certificate
active
06223698
ABSTRACT:
FIELD OF THE INVENTION
The invention concerns a new device for producing hot water of the type comprising a burner, in particular a gas burner, sustaining rapid combustion in a combustion chamber.
BACKGROUND OF THE INVENTION
Conventional devices for producing hot water comprise a (generally tubular) exchanger wherein the water to be heated circulates in order to transfer calories through an exchange wall. The main drawback of these exchange circuit devices lies in the poor heat transfer efficiency level.
A new type of device for producing hot water, referred to as direct contact device, has appeared in the past ten years, wherein the water to be heated is sprayed and flows through the combustion chamber so that the exchange occurs directly without any interposed exchange wall; this type of direct contact device is characterized in that the combustion chamber is wide open so as to allow direct contact between the flame and the sprayed water. In this new type of device, a layer of transfer nodules is most often arranged on the path of the smoke gases in order to ensure more complete heat transfer. An excellent transfer efficiency is thus obtained, that can be illustrated by the outlet temperature of the smoke gases which exceeds the temperature of the hot water obtained by a few degrees only (of the order of 5 to 10° C.). External hot gases are sometimes recovered and used as an additional heat input.
These direct contact devices are described in particular in the following patents U.S. Pat. No. 4,275,708, U.S. Pat. No. 4,574,775, U.S. Pat. No. 5,293,861, EP-0,082,139. It can be noted that this recent hot water production technique by direct contact had already been proposed in a very ancient U.S. patent (U.S. Pat. No. 884,223 delivered on Apr. 7, 1908) which describes a gas ramp C arranged at the base of an open combustion chamber E above which the water to be heated trickles.
Direct contact devices such as those described for example in patents GB-2,129,916 and EP-0,387,983 allow to reach remarkable transfer efficiency levels but they have several drawbacks. The most serious one, which considerably limits the development thereof, lies in the very high carbon monoxide ratio observed in the smoke gases produced by this type of device. This ratio, generally of the order of 500 to 700 ppm, remains, in the best case, above 150 to 200 ppm, which exceeds the ratios authorized by most standards (housing: ratio below 100 ppm in France). Another drawback of these devices comes from the very high temperature of the walls delimiting the combustion chamber (temperature of the order of 800° to 900° close to that of the flame): these walls, situated in an air/sprayed water/steam atmosphere, undergo great corrosion stresses; they can be equipped with cooling circuits, but this considerably increases the complexity and the cost of the device.
SUMMARY OF THE INVENTION
The present invention proposes a new device for producing hot water that allows to reach the transfer efficiency levels of direct contact devices without presenting the drawbacks thereof.
The main objective of the invention is to reduce the CO ratio of the gases discharged by direct contact devices to values equal or similar to those of the gases discharged by conventional exchange circuit devices; ratios of the order of 20 to 40 ppm are obtained according to the invention. These ratios can be obtained essentially for the following reasons:
in the first place, in the device according to the invention, the combustion obtained is a dry combustion carried out in a dry atmosphere in the hearth-container,
furthermore, this combustion is a complete combustion.
Dry combustion is obtained in the device of the invention by designing and by arranging the smoke gas diffuser as defined in claim
1
, so as to strictly prevent any water inflow and any steam entry in the hearth-container. The water and the steam are forced back in the vicinity of the discharge ports of the diffuser by suitable overpressure of the diffuser and of the hearth-container. Furthermore, the position of the diffuser and of its ports creates, in the vicinity of said ports, an air-lift type network that eliminates the internal secondary circulations that tend to form at the gas outlet (a phenomenon referred to as slipstream), these secondary circulations producing an effect of suction of the damp atmosphere of the enclosure towards the combustion chamber.
Complete combustion is obtained in the device of the invention by collecting the smoke gases at the end of the hearth-container situated on the opposite side from the burner. These gases have thus stayed long enough in the hearth-container for the combustion to be complete. Furthermore, the upstream portion of the diffuser connecting the hearth-container to the diffusion portion extends this residence time and allows in some cases (propane gas burner notably) to complete the combustion before discharge of the smoke gases in the enclosure.
Another objective of the invention is to eliminate the drawbacks of direct contact devices due to the high-temperature corrosive atmosphere to which the walls of the combustion chambers are subjected in this type of device.
The device for producing hot water according to the invention therefore comprises an enclosure provided, in the upper part thereof, with smoke gas discharge means, a combustion chamber consisting of at least one sealed contained referred to as hearth-container, extending along a substantially horizontal axis and arranged in a water section situated in the lower part of the enclosure, a burner associated with each hearth-container and arranged at one end thereof to produce rapid combustion extending along the horizontal axis of said hearth-container over the length thereof, water spraying means, associated with cold water delivery means and arranged so as to shower water in the upper part of the enclosure, hot water extraction means situated in the lower part of the enclosure, said device being characterized in that:
each hearth-container is extended, at its end situated on the opposite side from the burner, by a smoke gas diffuser comprising an upstream portion connected to said end situated on the opposite side from the burner and a diffusion portion extending in the enclosure above the hearth-container according to a substantially horizontal axis,
the diffusion portion of the diffuser comprises smoke gas discharge ports provided in the lower half of the section of said portion so as to allow to establish an overpressure inside the diffuser and the hearth-container and to prevent water and steam entry in order to obtain a dry complete combustion inside said hearth-container,
water level control means being associated with the water section to ensure, in said section, such a water level H that the hearth-container(s) are immersed in the water of said section and that the diffusion portion of the smoke gas diffuser remains constantly above said water level.
In the device of the invention, the smoke gases are brought into direct contact, at the diffuser outlet, with the water showered into the enclosure, but the combustion is carried out in a confined space separated from the water and the steam. Heat transfer occurs, on the one hand, by direct contact between the water and the smoke gases, and on the other hand by conduction through the walls of the hearth-container to the water of the water section; said diffuser(s) can also form an exchange surface in their upstream part connected to the hearth-container(s). Experiments have shown that, under such conditions, it is possible to simultaneously obtain:
a remarkable transfer efficiency level, of the same order as that of the aforementioned direct contact devices,
a reduced CO ratio in the smoke gases, of the same order as that of conventional exchange circuit devices (20 to 40 ppm).
Achieving such a CO ratio, much lower than that of known direct contact devices, can be explained by the fact that, in the device of the invention, the combustion that takes place is a dry combustion protected from water and steam, whereas
Antonelli Terry Stout & Kraus LLP
Institut Francais du Pe'trole
Wilson Gregory
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