US2912132A - Method for pressurizing hot pulverized coal - Google Patents

Description

2 Nov. 10, 1959 ALSPAUH ETAL 2,912,132

METHOD FOR PRESSURIZING HOT PULVERIZED COAL Original Filed Nov. 16, 1953 INVENTORS PAUL L. ALSPAUGH ROBERT G. KEISTER & RICHARD .PERRY 49 ATTORN Y Un ted W Pam O METHOD FOR PRESSURIZ'ING Hoi PULVERIZED GOAL Paul L. Alspaugh, South Charleston, Robert G. Keister, St. Albans, and Richard C. Perry, Charleston, W. Va., assignors to Union Carbide Corporation, a corporation 'of New York Original application November '16, .1953, Serial No. 392,255. Divided and this application December 29, 1958, Serial No. 783,314

2 Claims. (31. 214-152) This invention relates to a method and apparatus for receiving hot pulverized coal at atmospheric pressure and delivering it under pressure. into another vessel. This application claims the method and is a division of our co-pending application Serial No. 392,255, filed November 16, 1953, which claims the apparatus.

There are several methods known in the art for pressurizing granular, materials, including pulverized coal. These processes of the prior art, however, are designed for handling granular materials at normal or only slightly elevated temperatures. Pulverized coal'particles at a temperature of 350 C. to 400 C. present special problems in handling and no mechanism known in the art can be used successfully to pressurize coal at these temperatures, nor can any known apparatus be readily converted to such use, all such apparatus being suitable only for free-flowing materials. Throughout this specification of the invention and the claims, the term hot pulverized coal refers to pulverized coal particles at a temperature above 300 C.

The diificulties in pressurizing coal at such high temperatures arise from the fact that temperatures of 350 C. to 400 C. are above the softening temperature of bituminous coal. Therefore, pulverized coal particles at such temperatures tend to agglomerate and stick together, forming a thick pasty mass. This problem occurs whenever hot pulverized coal is allowed to stand in a vessel, even at atmospheric pressure, and is greatly intensified when the hot pulverized coal is put under pressure. Using any method known in the art, any attempt to pressurize hot pulverized coal particles would result in the coal agglomerating into a semi-solid mass and hanging up in the pressurizing apparatus.

We have discovered a method whereby hot pulverized coal may be introduced into a pressurizing chamber, put under pressure and delivered from the chamber still in granular form, without any agglomeration or solidification occurring.

The process of the invention comprises admitting the hot pulverized coal at atmospheric pressure to. a pressuretight chamber, sealing the chamber, diifusing through the coal an unreactive gas such as steam or an inert gas or a mixture of the two, while admitting the coal and while building up the pressure in the chamber to slightly above the pressure in the mixing chamber to which the coal is to be admitted, and then opening the pressure chamber to admit the coal to the mixing chamber.

An apparatus of the invention comprises a pressuretight chamber having an inlet means and outlet means for hot pulverized coal and inlet and outlet means for steam or inert gas. The coal inlet and outlet means are straight through construction valves, preferably of the clapper type. The various inlet and outlet means in the apparatus, with the exception of the aerating valve are all controlled so as to operate in a definite time sequence, thereby acc'omplishing the pressurizing of the coal in a matter of minutes so as to permit semi-continuous operation. i

In the drawing:

Fig. 1 is a view of the entire apparatus, with the upper coal inlet valve A shown in section.

Fig. 2 is a section view of the lower coal valve B, showing construction details common to all three coal valves.

Fig. 3 is a partial section of the upper part of the apparatus, showing the operating mechanism for the lower coal inlet valve B.

The apparatus shown in the drawing comprises a pressure chamber 11 with a removable top 12 bolted thereto to form one pressure-tight chamber.

The hot pulverized coal which is to be pressurized is conducted to the chamber 11 through a supply pipe 13. It is admitted through two clapper type inlet valves A and B. The upper 'coal inlet valve A consists essentially of an orifice having a flange 14 with smaller diameter pipe 15 mounted therein and cooperating therewith a circular disc 16 mounted on a rotating rocker arm 17. The arm 17 is afiixed to a shaft 18 which is held by brackets mounted inside the pipe section 19. The construction and operation of this upper coal inlet valve A is otherwise identical with that of the lower coal inlet valve B through which the coal next passes. This latter valve is described in detail below.

While the hot coal is entering the chamber 11, an unreactive gas for instance steam or an inert gas such as nitrogen, or a mixture of such gases, is continually entering the chamber 11 through aerating valve 20. This steam or inert gas aerates the hot coal and forms a gas film around the individual particles. This film forming action serves to prevent the particles from agglomerating and sticking together. Thus the coal remains in the pulverized state and there is no formation of semi-solid masses of the hot coal. The aerating valve 2t"; is kept open through all phases of the operational cycle because there is at least some hot coal in the chamber for all but a few seconds of the cycle, as will be seen later.

When a full charge of hot coal has entered the pressure chamber 11 through the two coal inlet valves A and B, these valves are closed to seal the chamber, except for the positive flow of gas through the aerating valve 20. The upper coal inlet valve A closes first, stopping the flow of coal, and a few seconds later the second valve B closes, effecting a pressure-tight seal. By employing two valves a better seal is etfected because the lower valve B does not close while coal is passing through.

The pressure chamber 11 thus having been sealed with a charge of coal inside, the vapor valve 21 opens to admit a large volume of the aerating gas. The pressure in the chamber is rapidly built up to a value of from one-half to one pound above the pressure in the mixing chamber to which the hot coal is to be admitted. This latter pressure may be as low as one pound or as high as 50 pounds per square inch. Should it be necessary, even higher pressures could be obtained readily.

The three clapper-type valves A, B and C which admit the hot coal into and out of the pressure chamber are all of the same general design and construction. A detailed description is given below of the lower coal inlet valve B, as shown in Figs. 2 and 3. The other two valves differ only in that they are mounted in sections of pipe rather than in the body of the pressure chamber.

The lower coal inlet valve B is constructed as follows: An entrance pipe 24 is mounted in a flange 22 which is attached to the upper end of the vessel 12. The end 23 of the entrance pipe 24 is preferably hardened in a suitable manner to resist wear and forms the valve seat. A disc 25, having a face similarly hardened, when in the closed position, as shown in Fig. 2, abuts against the pipe end 23 to stop completely the flow of hot pulverized coal into the pressure chamber 11. The disc 25 is at tached to brackets 26 attached by a pin 27 to a hinged member, an arm 28, which in turn is attached to a rotating shaft 29, the shaft 29 being held pivotally by two brackets 31 attached to the inside wall of the pressure chamber 11. Thus, when the shaft 29 is'-rotated,;the

disc swings from the closed position-described above to,

an open position, through an arcofsomewhatmore than 90. When the disc is back, in-the open position, as.

shown in Fig. 1 of the drawing, the entrance pipe. 24.

mounted on the arm 28. The inner, surface of thehole through the arm 28 through which ;the pin 21 passes is concavely rounded so as to permit a small amount of movement in the otherdirection by the disc 25. These pivotal arrangements are for the purpose of allowing some;

compensating movement by disc 25in order to, effect a tight seal with the pipe end 23.

The disc 25, being connected through the arm.28 .tov

the shaft 29, moves througha 90 degree are between the open and closed position when the shaft 29 is rotated. The shaft 29 extends outside -the pressurized.cham ber 11, being supported outside by the support bracket 32.

To prevent the escape of pressure from the pressure chamber 11, the shaft 29 passes out of the pressure chamber 11 through a packing follower 33, held in a packing gland 34. This packing gland 34 holds a lantern.

ring of packing material 35 around the shaft 29 to prevent pressure leakage. As a further safeguard, a positive pressure of inert gas is introduced into the packing gland 34 through the inlet 36, from the supply line 37.so as to prevent hot abrasive solids from getting into the packing.

The outer end of the shaft 29, in the embodiment of the invention shown in the drawing, is connected to an air piston, though other driving meanscould be used.

A connecting arm 33 is shown fixed at one end totheshaft 29 and pivotally attached at the other to a connecting shaft 39. The connecting shaft 39 is in turn connected to the piston shaft 40 of the compressed air cylinder 41. The motion of the piston shaft 40- is suitably transferred through the connecting shaft 39 and the connecting arm 38 to cause rotation of the shaft 29.

The movement of the piston shaft in and out of the cylinder 41 is determined by the flow of compressed air into the cylinder 41 which is controlled by the valve 42.

When the desired pressure in the chamber has been attained the vapor valve-21 is closed and the-coal outlet valve C is opened and the chamber emptied of coal."

This valve C is then closed and an exhaust valve- 43 isopened, reducing the pressure toatmospheric once more;

The coal inlet valves A and B are then opened, and the pressure chamber received another load of coal.

The construction and mode of operation ofthe coal H outlet valve Cis identical with the-upper coal inlet valve A, and differs from the lower coal inlet-valve B,-de-

scribed indetail above, only inthattherotating shaft is mounted in a pipe 44 rather' than in the body 11.' A

thermocouple well 45 is provided for recording the temperature of the coal in the chamber.

The operation of the invention is held closely to' a definite time sequence. The overall period for a pressurizing cycle may vary from one to. twenty minutes,

depending on the size of the apparatus, the temperature of the coal, the pressure towhich-it-is to beraised and similar factors.

The cycle-to be described is of two; and

one-half minutes duration and was used toprocess-four tons ,of-coal per hour, the coal being at a temperature of 360 C. and being raised to a pressure of 30 pounds...

amount. .The coal exit valve.C then opens and empties J the chamber in forty-five seconds. The coal exit 0 valve then closes, preferably with a rapping action to clear the face and form a good seal.: The vapor exhaust valve 43 is then opened briefly to depressurize the chamber and complete the cycle. The chamber is now ready to receive a new load of coal. ,Throughout the cycle the aerating valve 20 is open and admitting aerating gas.

A pressurizing chamber, embodying the invention as shown in the drawings, has been operated successfully on the time cycle just described, receiving hot pulverized coal at atmospheric pressure and at temperatures of 350 Cato 400 C., and delivering it under pressures of 35 to 40 pounds per square inch, still in the pulverized state and without agglomerated masses. provided by the introduction of the steam and inert gas through the hot coal, such operation would be impossible.-

While the valve used to admit and deliver the hot pulverized coal could be modified without exceeding the distinct advantages.

without the interference of solid particles. Preferably, the valve should be located in a vertical or nearly vertical position. To prevent wear of the seating surface, both the end of the pipe and the face of the valve disc may be hardened or otherwise treated by any suitable method to resist abrasion due to leakage of high velocity coal dust particles.

A further advantage of the clapper-type valve shown is that the entrance pipe is a separate and removable part. Thus, entrance pipes with various sized orifices may be substituted when desired, to control flow. All parts of the valve are readily accessible for replacement and repair.

The apparatus embodied in the drawing is tilted at an angle from the vertical, which provides somewhat easier control of the coal flow through the apparatus, due to decreased velocity. The apparatus could be completely vertical however.

not be greater than 30 degrees for the body of the ap paratus or for any of the coal entrance or exit valves.

What is claimed is: 1. A method for pressurizing hot pulverized coal particles which comprises introducing said hot coal particles into a chamber at substantially atmospheric pressure;

sealing said chamber; introducing an unreactive gas into said chamber until the pressure within said chamber is between two to fifty pounds per square inch gage; removing said coal from said chamber under said pressure; releasing the pressure from said chamber; and concurrently introducing a further amount of unreactive gas into said chamber, at least during said introduction of coal into said chamber and said pressurizing of said chamber, for the purpose of preventing the agglomeration of said hot pulverized coal particles.

2. A method for pressurizing hot pulverized coal particles for introduction into a mixing chamber which com-- prises introducing said hot coal particles into a pressuriz ing chamber at substantially atmospheric pressure; sealing Without the aeration- In order not to exceed the angle of repose of the hot coal the angle with the vertical mustsaid pressurizing chamber; introducing an unreactive gas into said pressurizing chamber until the pressure insaid p'ressurizing chamber is built up to a selected value above the pressure in the mixing chamber to which said hot coal is admitted, without agglomeration of the particles; delivering said coal from said pressurizing chamber to said mixing chamber under said pressure without agglomeration of the particles; releasing the pressure from said pressurizing chamber; and concurrently introducing a further amount of unreactive gas into said pressurizing chamber, at least during said introduction of coal into said pressurizing chamber and said pressurizing of said pressurizing chamber all without agglomeration of said hot pulverized coal particles.

No references cited.

Claims (1)

1. A METHOD FOR PRESURIZING HOT PULVERIZED COAL PARTICLES WHICH COMPRISES INTRODUCING SAID HOT COAL PARTICLES INTO A CHAMBER AT SUBSTANTIALLY ATOMSPHERIC PRESSURE; SEALING SAID CHAMBER; INTRODUCING AN UNREACTIVE GAS INTO SAID CHAMBER UNTIL THE PRESSURE WITHIN SAID CHAMBER IS BETWEEN TWO TO FIFTY POUNDS PER SQUARE INCH GAGE; REMOVING SAID COAL FROM SAID CHAMBER UNDER SAID PRESSURE; RELEASING THE PRESSURE FROM SAID CHAMBER; AND CONCURRENTLY INTRODUCING A FURTHER AMOUNT OF UNREACTIVE GAS INTO SAID CHAMBER, AT LEAST DURING SAID INTRODUCTION OF COAL INTO SAID CHAMBER AND SAID PRESSURIZING OF SAID CHAMBER, FOR THE PURPOSE OF PREVENTING THE AGGLOMERATION OF SAID HOT PULVERIZED COAL PARTICLES.

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