US1520923A - Steam drier - Google Patents

Description

Dec. 1924. 1,520,923

J. M. BALDWIN STEAM DRIER Filed April 7, 1922 avwe 02:

@51 A awe/WW Patented Dec. 30, 1924.

' by passin UNITED STATES H 1,520,923 PATENT OFFICE.

.mmns n. BALDWIN, or naownvnmn, NEW YORK; MARY n. BALDWIN Anmmsran- TBIX or SAID JAMES m. BALDWIN, nncnasnn.

Application filed April 7,

To all whom it may concem.

Be it known that I, JAMES M. BALDWIN, a citizen of the United States, residing at Brownville, in the county of J eflerson, State of New York, have invented certain new and usefill Improvements in Steam Driers; and I do hereby declare the following to be a full, clear, andexact dBSCI'lPtlOn of the invention, such as will enable others. skilled in the art. to which it appertains, to make and use the same.

In paper manufacture, when the aper web leaves the felts or presses of the orming machine it still contains some 65% or more of water, the bulk of which is removed the paper throu h a battery of rotating rying cylinders. ese cylinders are steam heated. In order to utilize efiiciently the heat of the steam it should, of course, be condensed within the cylinders, and not merely passed through them 1n gaseous form. Thus arises the problem of removing the condensate and inert gases from the rotating cylinders, for it is clear that a cylinder half filled with water is not only ineflicient as a drying instrument, but requires unnecessary power for its rotation. 1 The system most commonly employed for removing this condensate involves the use of siphons. A pipe enters each drier through one of its trunnions, and bends down to within an inch or so of the lowest line of the cylinder; Its other end is connected to a common drip header situated below the level of the cylinders and sealed by a water trap from the atmosphere. Steam from a common header is introduced to the cylinders likewise through one of the trunnions, ordinarily the same one through which the siphon pipe passes. In starting the drier in operation, most of the steam passing. into the cold cylinders will condense there until after a time the condensate will rise and cover the inner ends of the exhaust siphons. If the pressure difli'erential between the cylinders and the drip header is suflicient this condensate will be forced up the siphon pipes through the trunnions and down unti a siphoning action is set up and the cylinders emptied. At first the pressure within the drip header is low and this necessary difi'erential exists. Gradually, however, as the system warmsup the pressure within the drip header rises and the pressure differential between the cyl1n.

DRIER.

sure differential is suificient to raise the con-.

densate from its level in the cylinder to the trunnion and force it down the other leg of the siphon far enough to start the siphon action, and that in the nature of things this differential must be small. What is the result? The condensed water accumulates in many of the cylinders until they are almost half filled, or until, by its own condensation, it raises its level to such operation steam is a'point that the slight pressure within the cylinder is suflicient to start the siphon act1on.'

It is also to be noted that the system makes no provision for the elimination of entrapped air. The cylinders are originally filled with air and the steam brings some air with it. The steam condenses and is removed, but the air does notcondense and remains. It remains in the system and gradually cuts down the amount of steam which can enter. As less steam enters the cylinders they become less effective. Besides, as less steam enters less steam is condensed, and the level of the condensate approaches the effective siphon level more and more slowly. Finally it gives up the attempt andthe air-bound cylinders almost half filled with water turn merrily on, cold and dead, consuming power to no good. In a battery of 72 drying cylinders it is common'to find from 6 to 10 in this condition. Under the. circumstances there is just one thing to doblow the battery out. High pressure steam is turned on and the 'whole battery emptied of its water. This is heroic treatment and indicates that something is wrong with the system which requires 1t.

To recapitulate then, we see that the present siphon system for removing the condensate is ineflicient. It permits the cylinders to half fill with water before they are emptied. It provides no automatic means for eliminating air and so after a time the cylinders become dead and air-bound. It is the object of the present invention to reduce. these inefficiencies to a minimum.

Now when the siphon acts it draws over all of the water in the cylinder above the level of its end, and the siphon pipe then fills with steam mixed with a little air. When this steam condenses it reduces the pressure within the siphon pipe. Ordinarily this is automatically taken up by the back pressure steam from the drip header which in present practice is always in open communication with some empty cylinders. It occurred to me that if each siphon were automatically cut off from the drip header after each emptying, and sealed, after a while this drop in pressure, due to condensation, would establish a sufhcient pressure difierential to initiate the siphon action. And besides each cylinder would be acting independently of every other cylinder. As a simple and satisfactory method of efieoting this seal, I lead the the down-coming siphon pipe into the drip header, not through its top, as is customary, but through its bottom, after first making a U bend. As the drip header is always partly filled with water (or can be made so by slightly inclining the end which enters the trap), the U-bend of each siphon will also be filled with water. I also provide means through which the air entrapped in the siphon pipe can be forced out. This is preferably a thermostatic air valve.

The invention will be more clearly understood after a study of the accompanying drawing which discloses a preferred embodiment of it, although other arrangements of the parts might be made to operate in accordance with the principles discussed above. In this drawing the single figure represents a Vertical section through a batterv of drying cylinders showing one end of an upper cylinder and some of the connections in section, and one end of a lower cylinder and its connections in elevation. The general arrangement of these cylinders, the method of driving them and supplying steam to them is well understood and, as it ,forms' no part of the present invention, will be described only very briefly.

In this drawing 1 represents the drying cylinders provided with hollow trunnions 2' journaled at 3 upon standards 4: and driven by means of intermeshing gear wheels 5. Steam is supplied from anysuitable source through a steam header 6, from which it passes through vertical pipes 7 to each individual drier passing through the hollow trunnions 2. The condensate Which forms in the bottom of each cylinder is removed through a siphon pipe '8 which extends from a point near the bottom of, the cylinder, through the center of a hollow trunnion, and into a vertical extension 9 which leads di 3. passes Tit) water, and this, of course, flows into the a bend l1 and seals the lower end of the pipe 9, as clearly shown in the drawing.

The only other change contemplated by the present invention is the provision of a thermostatic air valve 12 situated at the upper end of pipe 9 and the outer end of pipe 8, that is, at the bend of the siphon.

The operation of the driers when modified in accordance with the present inventien as follows: Steam is introduced into the cylinders 1 from the steam header 6 and, the cylinders being cold the .steam condenses within them. The condensate collects in the bottom of the cylinder and gradualiy extends above the lower end of the siphon pipe 8. As the cylinder warms up the swarm pressure within it increases and this pressure rises to a point where it is suficient to :torce the condensate up the pipe 8 through the trunmonand down the pipe 9 far enough te lnltiate a siphoning action. The cylinder is then immediately emptied of its water. the last water passes over the siphon, pipe 8-9 becomes filled with steam mixed with a little air under the steam pressure of the cyi- 1 inder. Gradually a second volume of condensate forms and seals the lower end of pipe 8. The entrapped steam in pipe 8-9 graduallycondenses and thus 'reduces the pressure within the siphon. In response this decrease in pressure a column of water rises in pipe'8 and a second column from the U-bend 11 in pipe 9. Any air within the siphon pipe is forced out through the thermostatic air valve 12 by pressure from cyi inder and drip header; condensate from the cyl1nd er is forced over and the siphon action is again set up. This operation is repeated indefinitely.

Thus by the simple expedient of sealing the lower end of the siphon pipe and providing an air valve within it, it becomes unnecessary to wait until each cylinder is half tilled wlth water before the siphoning action can begin. This action is automatically set up through the reduced pressure in the siphon pipe from either condensation of entrapped steam or the escape of air through valve No. 12 long before the cylinder has half filled with condensate. no danger that the cylinder will become airbound, forwith each siphoning action some of the air is carried over into the siphon pipe and expelled through valve 12 before the next siphoning action.

There is aiso I claim:

1. A steam drier comprisin the combination of a rotary drying cylinder, means for introducing steam thereinto, a hollow trunnion, a siphon pipe for removing the condensate passing upwardly from a point near the bottom of the cylinder, through the trunnion and then bending downwardly, said siphon pipe being provided at its outer end with a water seal, and an air valve at the bend of the siphon.

2. A steam drier comprisin the combination of a rotary drying cylinc ler, means for introducing steam thereinto, a hollow trunnion, a drip header for receiving the condensate from thevcylinder, a siphon pipe for removin the condensate from the cylinder to the rip header passing upwardly from a point near the bottom of the cylinder,

through the trunnion and then bending downwardly to the drip header, the lower end of the siphon pipe terminating in a U- bend and entering the drip header from below, and a thermostatic air valve at the bend of the siphon.

In testimony whereof i afiix my signature.

JAMES BALDWIN.

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