Earlier attempts in developing a modular pyrolysis unit include U.S. Pat. Nos. 5,589,599 and 6,039,774 (McMullen '599 and McMullen '774). McMullen ('599 col. 18, lines 49-50; '774: col. 18, lines 46-48) states “[f]urthermore, the present plant can be incrementally expanded in capacity at separate and strategic sites due to its modular and comparatively compact design.” In the McMullen '599 and '774 patents, a single pyrolysis unit is a module. McMullen's plant is modular only in the sense that McMullen can install multiple modules to meet customer requirements. McMullen's “modular” plant requires a pre-determined number of retorts that will be permanently installed into a static assembly. McMullen's FIG. 2, referenced for its modular construction, does not show that the retorts are separable and replaceable on an ad hoc basis after installation in the field. McMullen ('599 col. 29, lines 45-54; '774 col. 29, lines 39-48) also discloses a feedstock plug (i.e., a stack of feedstock at the inlet of the retort creates an air seal or plug). By keeping the feedstock hopper full, McMullen prevents ambient air from entering the pyrolysis unit. Of course, McMullen's feedstock will have “entrained” air inherently included within the feedstock. McMullen's feedstock plug is a passive system relying only on the level of feedstock at the inlet to the system to prevent ambient air from entering. McMullen fails to show or suggest any means for removing entrained air from the feedstock. McMullen FIG. 9 (both '599 and '774) shows a multiple pitch auger ('599: col. 26, lines 19-22; '774: col. 26, lines 15-17) in a dewatering assembly 40 to move a carbon slurry to a dryer. The multiple pitch in this figure is used to move the slurry faster toward the dryer. McMullen's multiple pitch auger is not located within the pyrolysis unit and has no effect on pyrolysis reaction time. FIG. 9 is representative of standard uses for variable pitch augers moving stock from a short pitch to a long pitch. This orientation makes the stock move faster toward its destination. McMullen notes (599: col. 20, lines 42-43; '774: col. 20, lines 39-41) that as feedstock undergoes pyrolysis, there is a “sequential reduction of solid mass.” McMullen discloses that due to this reduction, two retorts 14, 16 can feed pyrolyzed feedstock into one retort 18. Thus, McMullen uses a reduced retort volume to complete pyrolysis. McMullen, however, fails to recognize in any way that a consistent level of feedstock in a retort is beneficial to the process.
U.S. Pat. No. 6,653,517 (Bullock '517) addresses other issues in feedstock gasification units. Before addressing Bullock as a prior design, it is important to consider that Bullock does not disclose a pyrolysis unit. Bullock discloses a gasification system utilizing a fluidized bed, which is not the same technology as pyrolysis. Given the different technologies at issue, Bullock's augers are not located within a pyrolysis unit or any heated chamber at all. See Bullock column 4, lines 59-64 (“no internal moving parts within a part of a heated environment of the system”). Bullock discloses that “feedstock material is conveyed, preferably by pumping, into system 10 from tank 12 and hopper 14 via grinder 16 and blending tank 18 in such a manner that the ambient atmosphere is excluded from the interior of the operating system at all times.” Bullock column 7, lines 15-19. Bullock, therefore, is similar to McMullen in that Bullock only addresses ambient air exclusion by using the feedstock plug. Bullock has no mechanism to vent entrained air from the feedstock. In fact, Bullock teaches against any kind of restriction device for air exclusion by squeezing the feedstock according to the new invention. See Bullock col. 5, lines 17-20 (disclosing “a double auger in-feed system which operates so as to positively displace the feedstock into the processing environment without blockage or other impediment . . . .”) Bullock incorporates entry and exit plates about its auger and describes these plates in FIGS. 2A-2E and column 8, lines 49-60. FIG. 3, Reference 30 shows these plates (not numbered) as supporting the dual augers but not being related in any way to air exclusion.
Another known pyrolysis system is set forth in U.S. Pat. No. 7,878,131 (Becchetti '131). Becchetti is a combined pyrolysis and gasification process. The only relevant portions of the Becchetti disclosure are those portions related to pyrolysis (i.e., pyrolysis drum 14). Becchetti discloses (col. 3, lines 38-42) that the process uses a conventional pyrolysis system to provide carbon residue to the gasification process. This reduces the amount of carbon that has to be transported to the site. Becchetti's disclosure explains common features of standard pyrolysis systems.
Two prior publications addressing pyrolysis direction are U.S. Publication No. 20080286557 (Richard Tucker) and PCT Application WO 2010/144,354. Richard Tucker discloses and claims removing noxious gases from the pyrolysis system by filtering through carbon “at a controlled temperature.” The specification notes temperatures of 700° F. to 2000° F. in Paragraph 0052 (bottom). Richard Tucker's process eliminates the step of adding steam to the pyrolysis as disclosed in prior patents, but the overall effect is that R. Tucker's system would produce a very low quality activated carbon that he uses for filtration. These documents also disclose R. Tucker's attempts to patent control systems connected to gas composition monitors.