Patent Publication Number: US-4148405-A

Title: Solid feeder and method

Description:
BACKGROUND OF THE INVENTION 
     This invention was made during the course of, or under a contract with the U.S. Energy Research and Development Administration. 
    
    
     In the field of coal gasification, it is desirable to load coal from a low pressure ambient atmosphere to a high temperature reactor at pressures up to 1500 psig or more for producing fuel gas from the coal. One system for loading the coal into the reactor heretofore employed a slurry feeder. However, this system required slurrys, which were difficult and dirty to handle; they also limited the size of the coal used to a substantially uniform small diameter. On the other hand, the dry systems used heretofore, required hot gas valves and/or lock hoppers from which the high pressure gas from the reactor was allowed to escape. The latter resulted in substantial power losses from the reactor. Moreover, the typical lock hopper seals and hot gas valves that were required therewith, were expensive, subject to rapid wear, or were otherwise troublesome. 
     SUMMARY OF THE INVENTION 
     This invention eliminates the problems and short-comings of the prior art by employing a longitudinally extending, rotatable coal bucket that is sealed at its ends in a housing and loaded and unloaded between the seals while trapping high pressure gas from the reactor in the bucket between the seals, and by wedging a cone-shaped plunger end against a closed end of the bucket to displace the trapped high pressure bucket gas by expelling it back into the reactor from between the seals for conserving the gas power in the reactor, and for preventing wear on the seals. To this end, this invention provides a sleeve forming a longitudinally extending housing means, a rotable bucket having its ends sealed in the housing and having a reciprocal plunger forming a cone-shaped end that mates with the closed end of the bucket for displacing the high pressure gas trapped in the bucket back into the reactor from between the seals, and a non-rotating piston in the sleeve for biasing the plunger back and forth longitudinally while the bucket and housing are sealed against the release of the high pressure gas from the reactor. 
     More particularly, in one embodiment the process of this invention involves the steps of loading a longitudinally extending bucket with coal having sealed ends in a housing, a closed end, an open end and an orifice, the coal being loaded through the orifice between the seals to displace ambient low pressure gas from the bucket during a loading mode, rotating the bucket for unloading the coal into the reactor from between the seals during a delivery mode so that the coal is dropped by gravity through the orifice and replaced by high pressure gas from the reactor but any other leakage therefrom is substantially prevented; displacing the high pressure gas from the bucket by biasing a plunger having a cone-shaped end through the open end of the bucket into mating engagement with the closed end of the bucket to expel the displaced high pressure gas back into the reactor during the closed mode, to center the plunger in the bucket, and to crush any residual coal therein; and rotating the bucket for filling the bucket with ambient low pressure gas during a reloading mode substantially without letting the high pressure gas escape to the ambient during said filling, loading, unloading and displacing so as to conserve the high pressure gas power in the reactor during all said modes. With the proper selection of elements and their operation, as described in more detail hereinafter, the desired loading and conservation are achieved. 
     OBJECTS OF THE INVENTION 
     It is an object of this invention, therefore, to feed coal from an ambient atmosphere at low pressure into a reactor for producing fuel gas at high pressure; 
     It is another object to feed dry and/or variable-size coal to a high pressure reactor substantially without causing excessive wear on any sealing surfaces; 
     It is still further object to provide a rotatable bucket from which coal is displaced by a high pressure gas from a container having means for displacing the gas to expel it back into the container for conserving the gas power in the container. 
     The above and further novel features and objects of this invention will appear more fully from the following detailed description of one embodiment when the same is read in connection with the accompanying drawings, and the novel features will be particularly pointed out in the appended claims. It is to be expressly understood, however, that the drawings are not a definition of the invention but are for illustration only. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Referring to the drawings in which like elements are referenced alike: 
     FIG. 1 is a partial cross-section of one embodiment of the dry coal feeder of this invention illustrating the loading mode thereof; 
     FIG. 2 is another view of the apparatus of FIG. 1 illustrating the delivery mode of this invention; 
     FIG. 3 illustrates the closed mode of the apparatus of FIG. 1; 
     FIG. 4 illustrates the reload mode of the apparatus of FIG. 1; 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     This invention is useful in introducing substances from a low temperature ambient atmosphere at low pressure into a high pressure, high temperature container system. To this end, this invention is particularly useful for introducing coal from a hopper at atmospheric pressure into a high temperature coal gasifier at pressures up to 1500 psig or more. It will be understood, however, that this invention is useful for a wide variety of applications requiring the loading of solids from a low pressure to a high pressure ambient in a simple, efficient and effective manner. 
     Referring to FIG. 1, coal 11 from coal bin 13 fills lock 15 formed by a scoop-shaped shoe 17 having a non-rotating plunger 19 forming a truncated cone-shaped end 20 that is longitudinally wedged into the open end 21 thereof to form a rotatable coal bucket 22 in which only the plunger reciprocates selectively to close and open the rotatable orifice 23 from the low pressure ambient atmosphere 24 while preventing leakage of gas across the lock 15. To this end, the plunger has a circular seal 25 in sealing contact with the inside surface 27 of the bucket 22, and the bucket has circular seals 31, 33, 35 and 37 on its outside diameter in sealing contact with the inside surface 41 of a cylindrical housing 43 forming coal feed bin 13 and an outlet port 47 connected to a high pressure, high temperature gasifier-reactor 48 having suitable inlets 49, outlets 50, and gas sources 51. By selectively reciprocating the non-rotating plunger 19 and selectively rotating the non-reciprocating coal bucket 22, the bucket orifice 23 first selectively rotates to communicate the lock 15 with the low pressure ambient through coal bin 13, while the lock is closed from communication with the high pressure gas in gasifier-reactor 48, and then selectively communicates the lock 15 with the gasifier while selectively blocking communication of the lock with the low pressure ambient atmosphere. 
     During rotation of the shoe and/or reciprocation of the plunger, the seals substantially block any gas from leaking from the gasifier-reactor to the ambient 24 through the lock 15. To this end, seals 25, 31 and 33 are positive circular seals centered on the z--z axis, and seals 35 and 37 are circular seals centered on the y--y axis at right angles to the z--z axis for maintaining the desired pressure differential across the housing and the bucket means from the gasifier-reactor to the low pressure ambient and across the lock, discharge port and the single coal receiving and discharge port in the bucket means. The annular seals 31 and 33 are in parallel verticle planes and these seals are interposed between the sealing surface 41 of the cylindrical housing means and the bucket means on the opposite sides of the coal feed bin and the coal discharge port, as well as the single coal receiving and discharging orifice 23 in the bucket means. The annular second seals 35 and 37 are in parallel horizontal planes and these seals are interposed between the inside of the housing and the outside of the bucket means so as to be arranged around the open end at the top of the coal discharge port 47 and the open end of the bottom of the coal feed bin 13 respectively for substantially preventing verticle gas flow across the bucket from the coal feed bin to the coal discharge port. 
     As will be understood in more detail hereinafter, none of the seals are in the path of the coal as it is transported from the coal bin to the reactor, so the seals are substantially not eroded by the moving coal and the seals are substantially free from abrasion by any residual coal during the loading operation. Additionally, the plunger 19 forms a truncated, cone-shaped punch 20 in cross-section whose cameo is wedged into a rigid locking engagement with the closed end of the bucket, whose intaglio forms a mating matrix for the punch 20. 
     Additional circular seals 53 and 55 are provided for means 57 for biasing the plunger 19 back and forth in the bucket 22. Seal 53 is interposed between the outside of piston 59 and the sealing surface 41 of the cylindrical housing 43, and the seal 55 is interposed between the connecting rod 61 for the piston 59 and a partition 63 between the plunger 19 and the piston 59. 
     A source 71 of fluid under pressure connects through two-way valve 73 and line 75 with chamber 77 to bias the piston 59 and plunger 19 in one direction along the z--z axis. The same source also connects through valve 79 and line 81 having a selectively closed vent valve 82 with chamber 83 to move the piston 59 and plunger 19 in the opposite direction along the z--z axis. This reciprocation has the advantage that the plunger moves away from the coal bin to open the lock 15 for receiving the coal 11 from coal bin 13. Later, after the bucket 22 is rotated to dump the coal into the gasifier-reactor, the lock 15 fills with a corresponding volume of high pressure gas that is trapped in the lock 15. Then, the plunger 19 is biased back toward the coal bin and the coal discharge port to expel this trapped volume of high pressure gas back into the reactor so that there is substantially no loss of high pressure gas every time the lock is filled with coal. 
     The truncated cone-shaped cross-sectional end 20 of plunger 19 mates with and wedges into sealing contact with the correspondingly shaped intaglio of recess 60 in the closed end of bucket 22. This wedging action centers the plunger along the z--z axis and crushes any coal particles that may be lodged between the plunger and the closed end of the bucket so as to purge the same. Also, the wedge shaped recess deflects the coal away from the sealing surface 41 between the bucket 22 and the cylindrical housing 43, and it also substantially completely expels all the trapped gas back into reactor 48, while preventing any high pressure gas from entering the lock during the time the lock is being rotated. 
     Handle 91, which is mounted at the closed end of the bucket 22, rotates the bucket 22 first to line up the orifice 23 with the coal feed bin, and, later, after the coal is loaded into the lock 15, to line up the orifice 23 with the coal discharge port to dump the coal into the gasifier-reactor. Then the handle rotates the bucket back again to line up the orifice 23 with the coal feed bin for the beginning of a new cycle. Bearing 93 permits the bucket to rotate freely in cylindrical housing 43. 
     In one sequence, which is illustrated in FIGS. 1-4, the lock is alternately, selectively, opened and closed from either the low pressure ambient or the high pressure gasifier-reactor respectively to prevent the escape of high pressure gas to the ambient atmosphere through the lock. 
     In FIG. 1, the orifice 23 is lined up with the coal feed bin so that the lock 15 is filled with coal. 
     Then handle 91 rotates the bucket to line up the orifice 23 with the coal discharge port 47. This dumps the coal 11 into the gasifier-reactor so as to displace the coal with a corresponding volume of high pressure gas, which is trapped in lock 15, as illustrated in FIG. 2. 
     FIG. 3 illustrates the next step, which biases the piston 59 and plunger 19 to expel the trapped gas volume back into the gasifier-reactor. To this end, valve 79 opens while valve 82 is closed so that fluid source 71 pressurizes chamber 83. The gas in chamber 77 is vented to the atmosphere through vent 95 by suitably positioning two-way valve 73 when the piston moves the plunger away from the coal feed bin. 
     When the plunger moves in the opposite direction, the gas in chamber 101 is vented to the atmosphere through vent 103, as illustrated in FIG. 4. 
     In operation, coal 11 is automatically fed through orifice 23 to the lock 15 from the coal feed bin 13 at ambient pressure and temperature by simply rotating the coal bucket to line up the orifice 23 with the coal bin. Then handle 91 rotates the bucket to dump the coal into the gasifier-reactor, which contains hydrogen or another gas at a pressure of up to 1500 psi or more at a temperature of 800° C. or more. This lines up the orifice with the discharge port 47. The coal then is thus dumped into the gasifier-reactor where it forms fuel gas and char that are removed from the bottom of the reactor by conventional means, such as through the valves and lines shown in FIG. 1. Also, the high temperature is produced by conventional heater means, such as the heating element shown in FIG. 1. 
     After the coal is dumped from the lock 15 to displace the coal with high pressure gas that is trapped in the lock 15, the plunger reduces the volume of lock 15 to expel the trapped gas back into the gasifier-reactor through the orifice 23 and the coal discharge port. Then the coal bucket is rotated to line up the orifice with the coal feed bin, and the plunger is retracted from the lock to increase the volume of the lock 15 for the beginning of a new cycle in which more coal automatically falls by gravity into the lock to fill the same. 
     This invention has the advantage of efficiently feeding coal into a high-temperature, high-pressure gasifier-reactor substantially without losing any of the high-pressure, high-temperature gas therefrom or abraiding any of the seals thereof. To this end, this invention provides a shoe-shaped coal bucket in a sleeve forming a lock to dump the coal into the gasifier-reactor substantially without abraiding any of the seals thereof. Also, when the coal is dumped it is displaced by high-pressure gas that is trapped in the lock. Then the trapped gas is expelled back into the gasifier-reactor by a plunger that reduces the volume of the lock before it is rotated to receive more coal. After the bucket is rotated to its initial position for the beginning of a new cycle, the plunger is retracted from the lock to increase its volume, and coal automatically fills the lock again at ambient low pressure and temperature substantially without eroding or abraiding the seals and substantially without leaking any high-pressure high-temperature gas out of the gasifier-reactor to the ambient through the lock. 
     This invention also has the advantage that it provides single malfunction safety protection in case of failure of any single actuation system component. To this end, the coal feed bin is always sealed off from the gasifier. 
     This invention has the additional advantage that it can feed all types of coal and any size required. 
     A still further advantage is that the coal is not physically or chemically altered, e.g., crushed, compacted, agglomerated or devolatilized.