Drying and gas or vapor contact with solids – Process – With contacting of material treated with solid or liquid agent
Reexamination Certificate
1999-11-08
2001-07-31
Gravini, Stephen (Department: 3749)
Drying and gas or vapor contact with solids
Process
With contacting of material treated with solid or liquid agent
C034S360000, C034S370000, C034S095000, C034S216000
Reexamination Certificate
active
06266894
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to processing a charge of solid material in a vessel under conditions which include high mass flow rate of gas through the vessel and removal of gas from the vessel.
BACKGROUND AND SUMMARY OF THE INVENTION
The present invention extends to processing solid material by heating or by cooling.
The present invention relates particularly, although by no means exclusively, to processing a charge of solid material (which, optionally, has a low thermal conductivity) in a vessel under conditions (which include high pressure and temperature) that produce liquid from the solid material and high mass flow rate of gas (produced from the solid material and/or added to the vessel as part of the process).
The present invention relates more particularly to a process and an apparatus for upgrading carbonaceous materials, typically coal, particularly low rank coal, under conditions which include high pressure and temperature to increase the BTU value of the carbonaceous materials by removing water from the carbonaceous materials, which process and apparatus includes separating solids, liquid, and gas phases produced by or supplied to the process.
The following discussion of the prior art is in relation to difficulties separating solids, gas and liquid phases produced when coal is dewatered by heating the coal under elevated pressure conditions. It is noted that in more general terms the present invention extends to difficulties caused by high mass flow rate of gas through vessels containing solids, with or without liquid present, under heating or cooling conditions.
U.S. Pat. No. 5,290,523 to Koppelman discloses a process for upgrading coal by the simultaneous application of pressure and temperature.
Koppelman discloses thermal dewatering of coal by heating coal under conditions which include elevated pressure and temperature to cause physical changes in the coal that results in water being removed from the coal by a “squeeze” reaction.
Koppelman also discloses maintaining the pressure sufficiently high during the upgrading process so that the by-product water is produced mainly as a liquid rather than steam.
Koppelman also discloses a range of different apparatus options for carrying out the upgrading process. In general terms, the options are based on the use of a pressure vessel which includes an inverted conical inlet, a cylindrical body, a conical outlet with a single outlet at the apex of the conical outlet, ie the lowest section of the vessel, and an assembly of vertically or horizontally disposed heat exchange tubes positioned in the body.
In one proposal to use a Koppelman-type apparatus, the vertically disposed tubes and the outlet end are packed with coal, and nitrogen is injected to pressurise the tubes and the outlet end. The coal is heated by indirect heat exchange with a heat exchange medium supplied to the cylindrical body externally of the tubes. Further heat is generated by supplying water to the tubes, which subsequently forms steam that acts as a heat transfer medium. The combination of elevated pressure and temperature conditions evaporates some of the water from the coal and thereafter condenses some of the water as a liquid. A portion of the steam generated following the addition of water also condenses as a liquid due to the elevated pressure. Steam which is not condensed, and which is in excess of the requirements for optimum pressurisation of the packed bed, must be vented. In addition, noncondensable gases (eg CO, CO
2
) are evolved and need to be vented. Periodically, liquid is drained from the outlet end. Finally, after a prescribed residence time, the vessel is depressurised and the upgraded coal is discharged via the same outlet end.
It has been found that the configuration of the outlet end of the above-described Koppelman-type apparatus has not been altogether satisfactory in terms of separating the solid/liquid/gas phases and, more particularly liquid/gas phases. The problems encountered include high pressure drop and high gas velocity in the outlet end which results in:
(i) two phase flow of liquid and gas from the outlet end that is difficult to control;
(ii) blockage preventing discharge; and
(iii) fine and sometimes coarse material being discharged with liquid (and gas).
More particularly, in general terms, gas and liquid exiting a vessel through the same outlet duct tend to flow in a most irregular fashion due to the different flow resistances of the gas and liquid in the bed, ducts and control valves. The compressible nature of the gas, the rapidly varying resistances, and the comparatively high density of the liquid leads to a flow with high acceleration forces which can lead to disturbance and probable transport of particles in the packed bed.
One object of the present invention is to provide improved separation of solids, liquid, and gas generated in or supplied to the Koppelman-type apparatus.
A more general object of the present invention is to provide an apparatus for separating solids, liquid, and gas in pressure vessels operated at high pressures and temperatures.
A further more general object of the present invention is to provide an apparatus for introducing and/or removing high mass flow rate of gas into and/or from vessels containing solid material which is being processed in the vessels.
The term “high” in the context of “mass flow rate of gas” is understood herein as indicating that the total amount of the gas is a significant proportion, typically 5-10%, of the mass of the solid material and/or that the mass flow rate of gas approaches the threshold for fluidising the solid material in the vessel.
In the broadest sense, the present invention provides an improvement to a vessel for processing a charge of solid material under conditions which include high mass flow rate of gas through the vessel, the improvement including providing the vessel with at least one solids outlet for discharging solids from the vessel and a plurality of gas inlets and/or gas outlets for introducing gas into or discharging gas from the vessel at one or more levels of the vessel above the gas outlet or outlets.
More particularly, according to the present invention there is provided an improvement to a vessel for processing a charge of solid material under conditions which include high mass flow rate of gas through the vessel and which produce liquid from the solid material, the improvement including an outlet end of the vessel having at least one solids outlet, at least one liquids outlet, and at least one gas outlet, and the at least one gas outlet being positioned above the at least one solids outlet and the at least one liquid outlet.
The aspect of the present invention described in the preceding paragraph is based on the realisation that effective separation of solids, liquid, and gas from a vessel, with minimum entrainment of solids and gas with liquid, can be achieved by providing separate removal of liquid and gas at different levels of the outlet end, and with the gas outlet (or outlets) being at a higher level than that of the liquid outlet (or outlets).
This aspect of the present invention can also be described as an apparatus for processing a charge of a solid material under conditions which include high mass flow rate of gas through the apparatus and which produce liquid from the solid material, which apparatus includes:
(a) a vessel having:
(i) an inlet end having an inlet for supplying the solid material to form a packed bed in the vessel; and
(ii) an outlet end having at least one solids outlet, at least one liquids outlet, and at least one gas outlet positioned above the solids/liquid outlets;
(b) a means for supplying a fluid to pressurise the packed bed; and
(c) a means for supplying a heat exchange medium to heat the solid material in the packed bed.
It is preferred that the outlet end be in a lower section of the vessel.
It is preferred that the outlet end converges to one (or possibly more) solids outlets.
It is preferred particularly that the outlet end be conical.
It is preferred that the outl
Gravini Stephen
Harness & Dickey & Pierce P.L.C.
KFx Inc.
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