Solids feeder apparatus
BACKGROUND OF THE INVENTION 
     In coal gasification technology and practice, it is required to load coal into a high pressure reactor or gasifier, and the lock hoppers and slurry feed systems used heretofore for such purpose have many problems associated therewith. Notable among these problems is the inherent escape and loss of gas from the gasifier as a consequence of loading coal thereinto. What has been needed then is an alternate system or apparatus which, besides ancillary features, prevents the loss of gas while feeding, which uses high pressure process gas, and means which does not require a carrier fluid for the coal or like solids. 
     SUMMARY OF INVENTION 
     This invention provides apparatus for feeding coal into a high pressure gasifier, comprising housing means having a single discharge port and a plurality of laterally disposed inlet ports, shaft assembly means having two first pistons that are spaced at a fixed distance apart, and second piston means alternately floatable between the fixed pistons to admit coal to the housing and deliver it to the discharge port. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a partial cross-section of one embodiment of this invention in the loading mode; 
     FIG. 2 shows the apparatus of FIG. 1 in a first delivery mode; 
     FIG. 3 shows the loading and simultaneous gas return mode of operation of the embodiment; and 
     FIG. 4 shows the second delivery mode of operation. 
     FIG. 5a is a detailed view of the floating piston shown in FIGS. 1 and 2; and 
     FIG. 5b is a detailed view of the floating piston shown in FIGS. 3 and 4. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1, the main elements of this invention for loading coal 9 into a gasifier line 10, comprise a housing means 11 having a single discharge port 13 and two laterally disposed inlet ports 15 and 17. A shaft assembly 19 rides back and forth in the housing means. This assembly has two first pistons 21 and 23 at a fixed distance apart. Carried on the connecting shaft 25 between the two first pistons is a floating second piston 27. The shaft 25 has a center passage 29 and first and second orifice means or feed ports 31 and 33. Connected to the housing means 11 are a first low-pressure fluid-actuating means 35, a second high-pressure fluid-actuating means 41, and a sump 59. 
     The two first pistons 21 and 23 have probes 37 that alternately close upon and engage housing end plates 39 to provide a connection between the passages 29 and a high-pressure fluid-actuating or actuation means 41. Actuation means 41 is connected to the end plate ports 43 and 43a through lines 45 and 45a and two-way valves 47 and 47a. 
     The first fluid-actuating or actuation means 35 is provided for biasing or translating the first pistons 21 and 23 back and forth. It comprises a low-pressure source of fluid that is selectively connected (by control means not shown) to an inlet port 51 through a line 53 and a check valve 55. The outlet port 57 connects with a sump 59 through valve 61 and line 63. These components are shown in association with the right-hand (as viewed in the Figure) side or end of the apparatus. As can be seen, however, corresponding ports and lines are associated with the opposite end of the apparatus; the same carry like or same index numbers, as those just detailed, to denote like or same functions. 
     In operation, the coal 9 is charged into the housing 11 through feed port 15, as shown in FIG. 1, to fill a cavity &#34;A&#34;. To actuate to the right, so as to feed the cavity-A coal into the discharge port 13, low-pressure fluid is introduced through corresponding (left-hand side) port 51a from low pressure actuation means 35 by way of line 53a and check valve 55a. This delivers the coal (to the gasifier) via port 13 and line 10. 
     In the next step, the floating piston 27 is moved (to the left) to cause the high pressure gas to return to the gasifier and to permit the introduction of coal through the second feed port 17. With the translation of piston 27 (to the left) into cavity-A, a cavity &#34;B&#34; is defined. This action is accomplished by introducing high pressure fluid from the actuation means 41 through line 45 and valve 47. This simultaneously loads coal cavity-B. 
     Shaft 25 carries a limit-stop means or abutment 70 which is enclosed by a compartment 72 formed within piston 27. Abutment 70 alternately engages end walls of the compartment 72, upon the piston 27 being caused to translate along shaft 25, to delimit the travel of the piston 27. Now then, as high pressure fluid is admitted into port 43, probe 37 and passage 29, it vents through orifice means or feed ports 33. These ports open externally of the shaft 25 onto the left-hand side of the abutment. The high-pressure fluid operates on the interfaced surfaces of the piston compartment 72 and abutment 70 to cause them to separate and move the piston to the left--into a closure of port 13, while returning gas back into line 10. 
     To deliver the coal from cavity-B to the discharge port 13 and line 10, all pistons are biased in unison to the left, to the positioning as shown in FIG. 4. This is accomplished by pressurizing port 51 through actuation means 35 by way of line 53 and check valve 55. To vent the fluid trapped behind piston 21, valve 61a is opened to dump the trapped fluid to the sump. This valve 61a is opened simultaneously with the initiation of low pressure actuation means 35. 
     The floating piston is moved from the position shown in FIG. 4 to the position shown in FIG. 1 for introducing coal into cavity-A again in the beginning of a new cycle by introducing high pressure fluid from means 41 through probe 29a, port 43a, and ports 31 via line 45a. To this end, valve 47a is opened. Ports 31 open externally of the shaft 25 onto the right-hand side of the abutment 70--to separate the interfaced surfaces of the right-hand side of the abutment and the inner, right-hand wall of the compartment 72. 
     This displaces the floating piston from the position shown in FIG. 4 to the position shown in FIG. 1. This simultaneously displaces the high pressure gas from cavity-B into the gasifier. 
     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. 
     While I have described my invention in connection with a specific embodiment thereof, it is to be clearly understood that this is done only by way of example, and not as a limitation to the scope of my invention as set forth in the objects thereof and in the appended claims.