US2007265A - Superheater boiler - Google Patents

Description

July 9, 1935.

W. H. ARMACOST SUPERHEATER BOILER Filed Nov. 8, 1952 ATTORNEY Patented July 9, 1935 SUPERHEATER BOILER Wilbur H. Armacost, New York, N. Y., assignor to The superheater Company, New York, N. Y.

Application November 8, 1932, Serial No. 641,705

2 Claims.

superheaters and particularly to those arrangements in which the superheaters lie in zonesin which the gas temperatures are high compared than the average with consequent local overheating of the superheater elements.

It is an object of the present invention to provide an arrangement whereby the said difilculties from local overheating may be minimized.

My present invention is based on the observation that the component parts of a stream of hot gases tend to mix to produce a more uniform temperature thruout the cross section of such stream when the stream of gases passes thru a channel of restricted free area as compared with the free area of the path of the gases leading up to and away from such restricted channel. In accordance with my invention, therefore, I place the superheater between twogenerating banks of a boiler; the free area for the flow of gases thru the superheater being reduced as compared with the free area for the flow of, gases thru the bank beyond the superheater by the use of bafiling for restricting or dimensioning the space for the superheater in the direction lengthwise of the generating tubes or by the close spacing of the superheater units or otherwise.

In order that my invention, together with its objects and advantages, may be more fully and easily understood, I will now describe in detail in connection with the accompanying drawing a superheater boiler forming a preferred embodiment of my invention, it being understood that apparatus. In the drawing:

such embodiment is illustrative only and that the invention may be embodied in other types of zontally inclined tubes I6, [6.

Tubes I6 connect My invention relates to boilers equipped with at their ends opposite headers l 4 with riser headers, one of which appears at [8 and the upper ends of which connect by means of the ordinary circulators and subheaders 2G, 22 and 24 with the drum [0 to provide a thermal circulation thru the generatingtubes I6.

Spaced from the bank of tubes I6 is a lower or slag screen bank composed of tubes l9, l9 ex tending parallel to the tubes Hi and connecting to lower headers 25 and upper headers 28. Headers 26 receive water from headers M by downcomer members 30 and the upper headers 28 connect with the riser headers l8 by riser members 32. As shown, tubes It are longer than tubes l6 but I do not limit myself to this. The bank of tubes IBbeing spaced from that of tubes I6 by the members 363 and 32, a space 34 is provided which is adapted to contain a superheater and I have illustrated therein a superheating means having a number of parallel units, one of which appears at 36 and each of which extends from an inlet header 38 to an outlet header 40. The bank composed of tubes l9, however, ordinarily is only a few rows high so that the gases from the furnace will be understood as leaving the tubes l9 and entering the space 34 while at a high temperature. If the temperature of the steam at any point in the superheater rises above a certain. maximum, damage can occur from either of two causes. Either the outer surface of the elements 36 will be oxidized or the steam will attack the inner surface of the elements. Both difficulties may, of course, occur simultaneously. It is, therefore, important that the gases be well mixed before striking the superheater elements 36 so that the maximum temperature of any portion of the gases will be as near as possible to the average temperature. In the arrangement shown, the free area for passage of gases of the space 34 is restricted compared to the free area for the passage of gases in both the banks above and below it by bafliing 42 and 44. Baffiing 42 extends inwardly from the upper ends of headers 28 and thence upwardly and outwardly to the lower ends of headers I8, similarly baffling 44 extends inwardly from headers 26 and thence upwardly and outwardly to headers M. The free area for flow of gases of space 34 is thereby considerably restricted in the direction longitudinally of the tubes I6 and I9 and the gases thereby well mixed to produce a nearly uniform temperature. I do not limit myself, however, to producing the restriction of free gas area thru the superheater space 34 in the manner illustrated and described herein above, but may obtain such an effect by other means. I may for instance produce suificient restriction of the free gas area in the space between the two groups of boiler tubes merely by placing the superheater units close enough together.

In the arrangement illustrated in the drawing, the bafliing 42 and 44 for restricting the space 34 is supported by sets of auxiliary connectors 46 and 48 respectively. The auxiliary connectors 46 between the riser headers I8 and 28, however, perform an important additional function in supplying sufficient space for the steam and water from tubes l9 to enter the lower ends of headers l8. Owing to the high rates at which the tubes l9 are operated in single-pass boilers difiiculty has been experienced with the circulation and I have found that such difiicnlty arises from insufiicient area in the connectors between the upper headers 28 of the lower set of generating tubes and the upper headers [8 of the upper set of generating tubes. The area obtainable in a set of connectors such as that shown at 32 is, of course, limited by the size of the headers and it is impossible to give the connectors as large a free area as the headers. However, auxiliary connectors running from vertical faces of headers such as 28 in U shape arrangement to the vertical faces of headers such as I8 provide ample space for the steam and water to pass between the two groups of headers and overcome the difficulty. It is evident that, tubes I8 being longer than tubes l6, headers 26 and 28 lie outside of headers l4 and I8 and members 36 and 32 must bend in order to connect the lower ends of the headers M to the upper ends of headers 26 and the lower ends of headers l8 to the upper ends of headers 28. There is therefore a resistance to the flow of water and steam through members 32 and to the flow of Water to the members 30 due to such bends so that the members 46 are valuable as supplying added capacity for flow between the headers 28 and I8. It will be evident also, that the path for water and steam from drum l0 through the tubes l9 and return is very long and that any additional resistance in such path may starve the tubes I9 of water. The additional capacity of auxiliary connecting members 48 between headers l4 and 26 is therefore of value in reducing the total resistance of the path through the tubes l9.

What I claim is:

1. The combination of a straight tube single pass boiler having a main generating bank and a transverse drum connected therewith so as to produce thermal circulation through said bank and drum, a slag screen bank below said main bank and spaced therefrom, headers at both ends of said banks, spacing members connecting the lower and upper ends respectively of the headers of said banks in the usual manner, a super-heater in the space between said banks, additional connecting members between those of said headers at the higher ends of the tubes of said banks and projecting inwardly toward the lower ends of the tubes of the banks, baffling material on said additional connecting members for constricting the length of the space between the two banks, additional connecting members between the headers at the lower ends of the tubes of the banks, such additional connecting members projecting inwardly toward the upper ends of the tubes of the banks, and bafiiing material on said additional connecting members at the lower ends of the tubes for further restricting the length of the opening between the two banks.

2. The combination of a straight tube single pass boiler having a main generating bank and a steam and water drum connected therewith so as to produce thermal circulation through said bank and drum, a slag screen bank below said main bank and spaced therefrom, headers at both ends of said banks, spacing members connecting the lower and upper ends respectively of the headers of said banks in the usual manner, additional connecting members between those of said headers at the higher ends of the tubes of said banks and projecting inwardly toward the lower ends of the tubes of said banks, additional connecting members between the headers at the lower ends of the tubes of the banks and projecting inwardly toward the upper ends of tubes of the banks, baffling material on said additional connecting members for constricting the length of the space between the two banks, and a superheater in the space between said banks, said superheater having one header between the spacing and connecting members at the higher ends of the tubes of said banks and another header between the spacing and connecting members at the lower ends of the tubes of such banks.

WILBUR H. ARMACOST.

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