Furnaces – With exhaust gas treatment means – Means separating particles from exhaust gas
Patent
1995-09-29
1998-04-14
Bennett, Henry A.
Furnaces
With exhaust gas treatment means
Means separating particles from exhaust gas
110265, 110309, F23C 900
Patent
active
057380236
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an apparatus for burning fuel, for instance oil, gas, coal, biogas formed from organic waste, or the like in which the apparatus comprises a combustion means for burning this fuel in addition to a converting means for converting the energy becoming available during this combustion into heat, cold or into a combination of thermal energy with power. For instance, a burner which can transfer the combustion heat to a heat exchanger for heating of a heating medium, such as air, tap water, or a combustion motor, for the purpose of heat/power generation, in which the apparatus further comprises a supply conduit for combustion air and a discharge conduit for flue gases.
2. Description of the Prior Art
Such an apparatus is known in diverse embodiments, for instance, heating furnaces for heating room areas either indirectly via water as heating medium or by direct heating of air, for private use or for professional purposes, for heating of tap water and the like.
Another example of such an apparatus is a thermally driven absorption heat pump or cooling installation for heating and/or cooling purposes.
Yet another example of such an apparatus is a heat/power installation, wherein the heat from the cooling water and the flue gases is used for heating purposes and the power is used to generate electricity by means of a generator or to drive one or more heat pumps.
The object of the invention is to provide an apparatus which is adapted relative to the prior art such that its efficiency is considerably increased.
Forming the basis of the invention to be described hereinafter is the insight that it is possible to increase the efficiency of known apparatus by reducing the latent and sensible enthalpy in the flue gases of such a known apparatus.
It is known that for instance the flue gas of natural gas-fired heating furnaces contains considerable amounts of so-called latent energy in the form of water vapour. In gas-fired, non-condensing so-called "improved efficiency furnaces", wherein the flue gas has a temperature between 130.degree. C. and 230.degree. C., the loss of latent heat content via the flue gases amounts to roughly 9.5% and of sensible heat content is between 6% and 9%. The total efficiency of these furnaces lies between 80% and 85%. At an air excess of 10% each 10K temperature fall in flue gas of non-condensing furnaces implies an increase in efficiency of about 0.5%.
The energy yield of gas-fired heating furnaces can thus be considerably increased by further cooling of the flue gas to below the dew-point of the flue gases. This dew-point depends on the air excess that is applied. At an air excess of for instance 1.27 the dew-point lies at roughly 53.degree. C.
Such condensing heating installations which, when properly embodied, have using efficiencies of over 90% of the upper calorific value of natural gas are called high efficiency (HE) installations. The desired temperature decrease of the flue gases is achieved by enlarging the heat exchanging surface between the flue gases and the medium to which heat is relinquished. In central heating systems for house heating an additional so-called flue gas condenser was originally added for this purpose to the already present heat exchanger, and later both were integrated into one heat exchanger. The low temperature of the flue gases also required an additional flue gas vent for discharge of these gases.
A drawback of this known method is that the efficiency gain to be made in this manner is limited and greatly determined by the installed heating surface, because condensation of the flue gases only occurs at a return water temperature lower than 50.degree. C., and the installed heating surface in dwellings is designed at a feed/return water temperature usually of 90/70.degree. C. at maximum heat demand. The actual return water temperature will thus lie above the dew-point temperature for a considerable part of the heating season, wherein no condensation therefore occurs and efficiency lie
REFERENCES:
patent: 3903694 (1975-09-01), Aine
patent: 4242972 (1981-01-01), Sicard
patent: 4443183 (1984-04-01), Shimizu et al.
Bennett Henry A.
Wilson Gregory A.
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