Fuel and related compositions – Consolidated solids – Containing specified binder
Reexamination Certificate
2000-03-10
2004-03-23
Toomer, Cephia D. (Department: 1714)
Fuel and related compositions
Consolidated solids
Containing specified binder
C044S554000, C044S596000, C044S620000
Reexamination Certificate
active
06709472
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a bio-based binding agent that is particularly effective when used in conjunction with a process disclosed herein for making impermeable agglomerates from finely divided minerals, such as coal, and for making insoluble composite materials from particulated lignocellulosics.
Many finely divided but otherwise useful materials are neglected or abandoned merely because they contain unwanted moisture; clearly, a low cost means for bonding such materials into durable products with a permanently reduced moisture content would enhance both their utility and value.
Providing such a means is a principal objective of this invention.
Earlier, attempts were made to adapt techniques disclosed in Applicant's U.S. Pat. No. 5,371,194 “Biomass Derived Thermoset Resin” & U.S. Pat. No. 5,582,682 “Process For Making Cellulosic Composites” to the production of synthetic solid fuel from fines created during the mining of Wyodak coal in the western United States. Although acceptable quality syn-fuel products were made, the cost of energy required to remove all entrained water and to polymerize the binder was prohibitive. These results underscored the need for a less energy-intensive, and altogether cheaper method of making weather-resistant products from particulate materials—a need now satisfied by the technology disclosed herein.
An exceptionally promising embodiment of this invention provides a long-sought alternative to coal mining's most waste-intensive practice—the improvident discard of huge quantities of moisture-laden fine coal. In particular, this synthetic-fuel-making process has the capacity to open a new and profitable outlet for this energy-rich debris—which at present creates environment tensions and financial burdens throughout the coal industry.
The novelty and economic merit of this new syn-fuel-making process, and the bio-based composition on which it relies, are unequivocally established by eliminating the need for the thermal energy invariably required by the prior art to dewater and dry coal fines, and to cure binders. The ability to dewater, shape and bond a variety of particulate feedstocks in a single continuous operation—without the input of thermal energy—is a distinguishing feature of processes employing this new bio-based composition. Coalescing, as used herein, means to quantify, shape, compress and express essentially all free water from a mixture of particulate, a wet-tack lubricant solution and a water-insoluble binding agent. When a chemically-inert particulate is agglomerated, coalescing may include both direct and indirect transfer of heat generated by compressive friction to the incipient agglomerate.
Essential to the dewatering method utilized in this invention is the presence on particulate surfaces of a substance, defined herein as a wet-tack lubricant, in very dilute solution. The preferred wet-tack lubricant is polyethylene oxide (PEO), a non-ionic water-soluble resin particularized by Union Carbide Corporation (UCI), Danbury, Conn. 06817, in brochure UC-876 5/95-5M. Relevant properties of PEO mentioned in the brochure include: “Lubricity, Friction Reduction, Water Thickening, Wet-Tack, and Shear-Thinning, and a high affinity for coal-fines, lignin and paper fines”. PEO is known to flocculate lignocellulosics but not hydrophobic coal-fines, and it is hydrophilic but not a surfactant. While it is a relatively new chemical, the use of PEO in coal and paper processing has become extensive.
U.S. Pat. No. 4,322,219 of Burns discloses a process for removing moisture by contacting coal—either run-of-mine or pipeline slurry coal—with a dilute aqueous solution of PEO and allowing the moisture to evaporate; alcohol may be added to accelerate evaporation. The use of PEO solutions to “. . . avoid the tendency of high-moisture low-rank coal to slack or degrade in size . . . ” is mentioned; however, no mention is made of small particles, or fines, and no suggestion that PEO could be used to facilitate the forcible expression of water from coal, or coal fines, or that de-watered coal, or coal-fines, could be agglomerated into a fuel product—with or without a binder.
The use of hydrophilic PEO in the process of present invention distinguishes it from U.S. Pat. No. 5,670,056 Yoon et al, which utilizes a hydrophobic reagent—preferably, mono unsaturated fatty esters or polysiloxane polymers—to aid mechanical means for dewatering coal-fines. No treatment beyond the dewatering of fine materials, such as agglomeration or bonding, is mentioned or suggested.
U.S. Pat. No. 5,658,357 of Liu et al. “Process For Forming Coal Compact Without A Binder” uses the surface tension of water and the absence of air-bubbles to furnish”. . . a binding effect which holds the carboniferous particles together and imparts mechanical strength in the compact . . . ”. If the surface-tension-producing water is removed from such a compact, disintegration quickly follows. Aside from reducing coal-log drag in a pipe line, the sole purpose of using a very dilute solution of PEO is reduction of the zeta potential to lessen electrostatic repulsion between particles in a coal slurry. In the present invention, the hydrophilicity, lubricity, thickening, shear-thinning, and fines affinity of PEO combine to facilitate particulate dewatering, densification and, unexpectedly, bonding during coalition.
Except for pellets made on a disc pelletizer, agglomerates made from mineral particulate by the process of the present invention have no need for the interim strength provided by PEO or supplemental heat; they are inherently insoluble and impermeable and—because they have been subjected to the frictional heat of compressive coalition—strong and durable. But no appreciable heat is produced during disc pelletizing; therefore, although agglomerates made on these machines are impermeable and insoluble, supplemental heat is needed to obtain a peak strength product. As used herein, the terms insoluble and impermeable refer to the behavior of a product or substance with respect to water.
White's U.S. Pat. No. 4,865,691 exploits a unique property of normally insoluble but water swellable polyvinyl alcohol (PVOH) particles: Swollen particles are dispersed in a dilute aqueous suspension of cellulosic fiber which, as excess water is drained, acts as a sieve retaining the swollen PVOH particles within the web. When heated, the entrapped swollen particles melt, dissolve into residual free water and diffuse into the web and, on cooling, solidify into a paper-reinforcing binder.
In U.S. Pat. Nos. 5,498,314, 5,328,567, and 5,800,675, Kinsley describes newer domestic grades of PVOH powder available from Air Products and Chemicals, Inc. (APCI) of Allentown, Pa. and specifies Airvol 125SF, 165SF, 350SF, 107SF, and 325SF as grades will allow the use of larger quantities of PVOH without undesirable side effects. None of the four aforementioned patents specify or suggest the use of PVOH in an unswollen state, or for a purpose other than paper-making.
Because PVOH is employed in a dissolved state as a coal-fines binder in the processes described in U.S. Pat. No. 4,787,913 of Goleczka, et al, and U.S. Pat. Nos. 4,586,936 and 4,863,485 of Schaffer, et al, they are easily distinguished from the present invention, wherein PVOH is used in an undissolved state. Neither swelling or dissolving PVOH powder is necessary to the present invention.
The ‘cook-out’ (dissolution) temperature of PVOH is specified by the manufacturer, APCI, as below 205° F. (93° C.) for all grades. In addition to the bio-based composition of the present invention and suitable grades of PVOH listed above, there are numerous water-insoluble binding agents, e.g., phenolic, acrylic, epoxy, thermosetting, or thermoplastic resins that melt or become temporarily soluble within the coalition temperature range (150-220° F.) and would, therefore, be technically suitable for this duty. Without exception, however, such plastics have been found to be uneconomic.
Little if any frictional heat is created by the apparatus du
Ferretti Arthur
Wilt Louise C.
Toomer Cephia D.
Wasson George W.
Wilt Louise C.
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