Liquid heaters and vaporizers – Stand boiler – Heated by liquid or steam
Patent
1981-05-01
1983-06-28
Yuen, Henry C.
Liquid heaters and vaporizers
Stand boiler
Heated by liquid or steam
110244, 110347, 110348, 110235, 432 99, F23G 700, F22B 500
Patent
active
043899790
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND AND GENERAL DESCRIPTION OF THE INVENTION
The invention relates to a method and an apparatus for the operation of a boiler installation with stoker-like firing, comprising a stoker chamber with a burner grating for the supply of the primary air, nozzles distributed over the periphery and a tubular boiler placed coaxially adjacent to the stoker chamber with an approximately circular inner chamber and annular gas aspiration.
Boiler installations with stoker-like firing are known in the prior art. In them the primary air is urged under pressure through the bars of the combustion grate which defines a bowl-shaped bottom for the fuel. The combustion takes place in two phases with a pre-combustion taking place in the bowl defined by the grating bars, while a post-combustion occurs, also called residual combustion, in the stoker chamber located above the bowl. The fuels burned in such installations develop, under a combustion of this kind, gases burnable on a large scale to which secondary air is admixed through nozzles placed in a crown-like arrangement, whereby the combustion in the stoker chamber takes place substantially free from residue.
It is known to design the firing equipment with a vertical axis and with an approximately circular cross-section, and to place the tubular boiler immediately above the stoker chamber which is open on top, so that the inner pipe crown practically forms a continuation of the stoker chamber. The inner chamber accommodating the pipe coils or pipe clusters is closed to a large extent at the top side, and the combustion gases are aspirated after having transferred their heat annularly to the pipe clusters, whereby it is possible to guide the gases several times annularly and, under reversal in axial direction, through pipe clusters surrounding each other concentrically.
In such boiler installations one considerable problem consists in that very high temperatures build up under optimal operation in the stoker chamber, so that the chamber walls are exposed to high thermal loads. It has been demonstrated in the art that a reduction of this thermal load, so that an optimal and economical operation is possible without too frequent shutdowns of the stoker firing system for a repair of the chamber walls, is extremely difficult. Therefore, the installations in most cases must be designed and built with higher expenses than what is necessary for actual operations under optimal conditions. This serious problem adversely affected the extended application of such boiler installations, although in principle they are extremely simple in their design and very economical in their operation, particularly since it became possible to provide for a reliable and satisfactory removal of the ashes without the necessity of a shutdown of the installation.
The invention is based on the problem of disclosing a method and an apparatus of the type defined initially in detail, with the aid of which it is possible to operate such a boiler installation with stoker firing under optimal conditions from a combustion-engineering point of view, without the need of frequent shutdowns for repairs at the chamber wall means. In this respect, care shall be taken primarily that with an improved manner of operation the installation can be built in a more space-saving manner and at a lower cost.
According to the invention this problem is solved by supplying the stoker chamber with primary air and secondary air sufficient only for a partial combustion of the fuel, by substantially constricting the cross-section of the flow of combustion gases and inflammable gases discharging from the stoker chamber, and by generating a pressure reduced with respect to the ambient pressure, whereby tertiary air is introduced tangentially at the circumference of the constricted flow at a pressure increased with regard to the ambient pressure and, subsequently, the cross-section of the entire flow again is flared upon its entry into the interior chamber.
As a result of the incomplete combustion in the grate bowl and in the stoker ch
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