US2565857A

US2565857A - Method of and apparatus for preventing slagging in tubular element gas heating furnaces

Info

Publication number: US2565857A
Application number: US669867A
Authority: US
Inventors: Kleiber Heinz
Original assignee: Aktiengesellschaft fuer Technische Studien
Current assignee: Aktiengesellschaft fuer Technische Studien
Priority date: 1945-05-28
Filing date: 1946-05-15
Publication date: 1951-08-28
Anticipated expiration: 1968-08-28
Also published as: DE873462C

Description

Aug. 28, 1951 2,565,857

5 H. KLEIBER METHOD OF AND APPARATUS FOR PREVENTI SLA NG IN TUB ING F ACE 2 Sheets-Sheet 1 ULAR ELEMENT GAS HEAT Filed May 15. 1946 Fig.1

A I lnucn'ior 19 19 Hanna Kleib er Attorneys 1951 KLEIBER 2,565,357

METHOD OF AND AP RATU OR R VENTI SLAGGING IN TUBULAR ELEMENT s 1-1 ING F AGES 7 2 Sheets-Sheet 2 Filed May 15, 1946 Inventor Heinz Kleiber Patented Aug. 28, 1951 PAT ENT oF icE-- i i2;565,s57 r I METHQD omsnmmrnsiros liliE- NENI N SL GGI N IUB GAS HEATING FURNACES Heinz "Kleiber, "Zurich, Switzerland, assigndr to Aktiengesellschaft 'Fuer Technische Studien, Zurich, Switzerland, a corporation of Switzerland Application May15,?1946, Serial No. 669.867 *ln switzerlahd May 28,1945

z-ciaims. ---(c1. 126-409) This invention relates to a tubular gas heater which is designed lin -particular for thermal power plants in which a gaseous'working medium, preferably air, is to be brought to a'higher temperature in a heater'by an indirect supply of heat from an external source.

In heaters of this kind'theworking medium has to be heated to temperatures between 600 and 700 C. and even more,thetempe'rature in the furnace chamber becoming in such case correspon'dingly high. If therefore fuels'which slag, such as pulverizedcoal for example have to be burnt in'the heater, there is risk that liquid particles of slag will'remainattach'ed tothe very hot heater tubes which ishighly'undesirable, asthis can lead to heavy slagging in thefurnace chamber in a shorttiiher The heater tubes must also be protected from the radiant heat of the fire gases, to which end it has already been proposed to return part of the flue gases to the furnace chamber in such a way that they form a cooling layer between the fire gases and the heater tubes. Inthis connectionthe'object"of'the present invention is to enable further improvements tooe achieved by causing the returned flue gases to enter the furnace chamber through g'ap s between the tubes of the heater, at leastat those parts which are most endangered and hottest. In this way it can be ensuredthat the fluegases which enter through the --gaps and are already cooled down, will blow the sticky or even liquid particles of slag away from the tubes and also cool them down below their melting point, so that they solidify and liquid slag cannot in any case become deposited on the tubes. The application of the invention is therefore desirable when the fuel burnt in the furnace chamber gives rise to the production of solid or liquid constituents (that is to say sand for example when blast furnace gases are burnt). The flame also will be forced away from the tubes by the returned flue gases so that no tongues of fire can come into contact with the tubes. The layer of flue gases, which, on account of the contained carbonic acid and water affords efficient protection against radiation, can never be churned up into eddies, overheated and torn away in the furnace chamber, by the turbulence of the flue gases, as it is continually renewed from the heating surface. The new technical rule according to this invention also enables an equalisation of the tube wall temperature and heat supply to be brought about, as the cold parts of the tubes, that is to say the sides of them which are turned away from the flame are heated by the returned flue gases, while those parts ofthetubes which are too hot are cooled. Furthermore the combustion'chamber has only to .be isolated-from the temperature of the returned flue "gases; any'p'ossibly irradiated and heated p'artsiof the walls of this chamber, are co'ol'edby thereturnedfluega's'es. 1

Several constructional forms of the. subject matter of the invention-are: shown by way-of example in' a simplified-form of representation the accompanying drawings? in which:

- -:'Fig. 1 shows a heater in'whichair'usedas'work-' mg medium in a power plant isto'b'e heated, said air. .flowirigfthrough-a part of the 'heater heated.

by" radiation and through a part heated by contact in two parallelcurrentsxfl I V 'Fig.-.-2-is a section onrthe line 11-11 of -'Fig. 1, the parts of the heaterwhich ar'e"situated-below this section being omitted for the sake of simplicity, the tubes b'einginot sectioned.

Fig. 3 shows in a view corresponding to'that'iof Fig. 1 a second embodiment of the invention.

*Figef4shows'inaaf'horizontal section a part of anh'eaterinWhichthe tubesare fixed in their relative position by distance piecesya'nd Fig. 5ash'ows a part of a heater'in'which-gaps are provided between groups of tubes only, each of these groups consisting of two tubes and being afi'ixed. to the, boundary fwall of :the. furnace chamber, "and the tubes being not shown in :sec-

' tion. I

In the Figures 1 and 2 numeral i denotes the furnace chamber, that is to say the combustion chamber, of a coal dust-fired heater A of a thermal power plant, in which air serving as working medium describes a cycle and in doing so is brought in a two-casing compressor 2, 3 to a higher pressure, then heated indirectly in the heater A by an external supply of heat and afterwards expanded in a turbine 4 which supplies energy both to the compressor 2, 3 and also to a consumer of useful output 5. Air for the support of combustion is mixed with the coal dust in a pipe 6. This air for the support of combustion is brought to the required temperature in a preheater 1, which is heated by the flue gases escap ing from the heater A, and it then passes through a pipe 8 into the pipe 6. The combustion chamber t is lined with tubes 9 through which a part of the air of the cycle which is to be heated flows. A part of the heat contained in the fire gases is given up to these tubes 9 in the combustion chamber I mainly by radiation. From the combustion chamber 1 the fire gases pass into a second chamber ID, in which a heating system I l is ar-- ranged to which the fire gases give up heat by 3 contact. The air to be heated in the heater A enters through a pipe I2 and divides at the distributor [3 into two parallel currents, one of which flows in the same direction as the fire gases through the. tubes 9 and theother in the opposite direction to the fire gases through the heating system H. The parallel currents thus heated combine again at the collector M, where they enter a pipe l connected to the inlet of the turbine 4 and thus forming a further component of the cycle which the air, heated in the manner described, has to pursue. A part of the gases escaping from the chamber 10, that is to say, a

part of what is usually termed flue gases, passes.

into a pipe IS, in which a blower I1 is arranged, so that said part of the flue gases is returned to the furnace chamber I. Theremainder of the flue gases passes, after flowing through the pass [8, in which the above mentioned air preheater I is arranged, out into the open air.

.The tubes 9, which line the furnace chamber I, are so arranged that gaps I9. (Fig. 2) are left free between them. Through these gaps IS the flue gases delivered by the blower I! pass into the furnace chamber I, blowing any particles of slag present off the tubes 9 in the manner shown in Fig. 2.

As shown in Fig. 3, thegaps between the heater tubes do not need to extend over the whole length of these tubes, as it may sufiice for the returned flue gases to pass between the tubes into the furnace chamber at those parts of the heater at least which are most endangered and hottest, i. e. only between the lower end of these tubes 20 up to the point B. In this second embodiment of the invention the tubes 20 are fixed in their relative positions by distance pieces 2| (Fig. 4), so that the necessary Width of the gaps between the tubes 20 for the blowing in of returned flue gases is preserved.

As shown in Fig. 5, instead of providing a gap between every two adjacent tubes for blowing returned flue gases into the combustion chamber, gaps may be provided between groups 23 only which consist each of two pipes 24. Each group 23 is afiixed to the boundary wall 21 of the furnace chamber 25 by a support 26.

The invention can be ,used with any arrangement and position of the tubes in the furnace chamber. The arrangement and direction of the 4 flame in the furnace chamber likewise do not constitute essential features of the invention.

What is claimed is: 1. In a tubular gas heater, the combination of a furnace structure having walls enclosing a combustion chamber and an oiftake passage leading therefrom; a tubular heat exchanger lining the combustion chamber and comprising a plurality oftubes spaced from one another and from the walls of the combustion chamber, the spacing of the tubes from the walls being greater than the spacing of the tubes from one another and the two spacings being so chosen that the interval between the lining and the chamber walls serves as a manifold space for distributing gases to be discharged through the inter-tube spaces; connections for passing gas to be heated through said tubular exchanger; a burner communicating with the combustion chamber and arranged to cause combustion therein within the space lined by said tubular heat exchanger; and means for drawing a portion of the products of combustion from said ofitake passage and discharging it under pressure into said manifold space.

2. The method of resisting deposition of slag on the surfaces of a row of spaced heat exchange tubes, which comprises burning a slag evolving fuel at one side of said row of spaced tubes whereby the tubes are exposed on that side to radiant heat generated by combustion; and delivering a hot gaseous medium at a temperature lower than the temperature of combustion against the other side of said row of tubes under pressure sufficient to cause said medium to flow through the vari-' ous inter-tube spaces and in a direction toward said burning fuel.

HEIN Z KLEIBER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Gygi July 10, 1945