Fuel and related compositions – Coal treating process or product thereof – Removal of undesirable
Reexamination Certificate
2000-05-12
2003-01-14
Toomer, Cephia D. (Department: 1714)
Fuel and related compositions
Coal treating process or product thereof
Removal of undesirable
C044S629000
Reexamination Certificate
active
06506224
ABSTRACT:
The present invention relates to upgrading a solid material.
The present invention relates particularly, although by no means exclusively, to upgrading a solid material which has low thermal conductivity.
The present invention relates more particularly to upgrading a solid material by removing water from the material in a process that includes:
(i) heating the material to an elevated temperature while the material is being maintained under high pressure; and thereafter
(ii) cooling the upgraded material to an ambient temperature.
One particular application of the present invention is to upgrade carbonaceous material, typically coal, to increase the BTU value of the carbonaceous material.
U.S. Pat. No. 5,290,523 to Koppelman discloses a process for upgrading coal by the simultaneous application of temperature and pressure.
Koppelman discloses thermal dewatering of coal by heating coal under conditions including elevated temperature and pressure 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 as steam.
Koppelman also discloses a range of different apparatus options for carrying out the upgrading process.
In general terms, the options are based on heating coal in a pressure vessel which includes an inverted conical inlet, a cylindrical body, a conical outlet, and an assembly of vertically or horizontally disposed heat exchange tubes positioned in the body.
In one proposal the vertically disposed tubes and the outlet end are packed with coal, and nitrogen is injected to pre-pressurise the tubes and the outlet end. The coal is heated by indirect heat exchange with oil that is supplied as a heat transfer fluid to the cylindrical body externally of the tubes. Further heating is promoted by direct heat exchange between the coal and steam that acts as a working fluid within the packed bed. In addition, the steam pressurises the tubes and the outlet end to a required pressure.
The combination of elevated pressure and temperature conditions in the tubes and the outlet end 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 in colder regions of the tubes due to the elevated pressure. Steam which is not condensed and which is in excess of the requirements for optimum pressurization of the packed bed, must be vented. In addition, non-condensable 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 hot upgraded coal is discharged via the outlet end onto a conveyor which transports the coal to a wet auger. Water is sprayed onto the hot upgraded coal as the conveyor transports the coal to the auger. The coal is cooled further in the auger and thereafter is spread out in a thin layer in a stockpile region and allowed to cool to ambient temperature.
An object of the present invention is to provide an improved method and apparatus for upgrading coal compared to that described by Koppelman.
According to a first aspect of the present invention there is provided a method of upgrading a solid material which comprises heating the solid material to an elevated temperature to remove water and thereafter cooling the upgraded solid material, and which method is characterised by:
(i) providing a plurality of vessels containing packed beds of the solid material and one or more than one heat exchange circuit for heating and cooling the solid material in the packed beds in the vessels by heat exchange with a heat transfer fluid; and
(ii) controlling the method so that the solid material in a first group of the vessels is at one or more stages of a heating cycle and the solid material in a second group of vessels is at one or more stages of a cooling cycle, and the controlling step(s) comprises selectively connecting the one or more than one heat exchange circuit to the vessels so that the heat transfer recovers heat from the solid material undergoing the cooling cycle in at least one of the vessels in the first group and transfers the recovered heat to the solid material undergoing the heating cycle in at least one of the vessels in the second group.
The basis of the above-described aspect of the present invention is recovery of energy from the solid material being cooled in one group of vessels and subsequent use of that energy to heat the solid material in another group of vessels.
In one embodiment of the present invention a plurality of heat exchange circuits are provided and the heat exchange circuits selectively connect pairs of the vessels so that the heat transfer fluid of each heat exchange circuit cools the solid material in one vessel in each pair and thereafter heats the solid material in the other vessel in each pair by heat exchange with the solid material in the pair of vessels.
The heat transfer fluid in each heat exchange circuit heats and cools the solid material in the pairs of vessels to respective different temperatures in the heating and cooling cycles, with the result that the solid material in each vessel is heated or cooled by a series of steps by sequentially connecting the heat exchange circuits to the vessel.
For example, one heat exchange circuit heats solid material in one vessel from an ambient temperature to a temperature T
1
and another heat exchange circuit that is subsequently connected to that vessel heats the solid material from the temperature T
1
to a higher temperature T
2
. At the same time, the heat exchange circuits cool the solid material in another vessel from the maximum temperature of the heating cycle to a lower temperature.
It is preferred that the contents of the vessel be at an elevated pressure during the heating and cooling cycles.
Solid material may be retained in one vessel during both the heating cycle and the cooling cycle.
Alternatively, solid material may be heated in one vessel during the heating cycle, transferred hot to another vessel, and cooled in accordance with the cooling cycle in the other vessel.
It is preferred that the heat exchange circuits heat and cool the solid material by indirect heat exchange.
The method of the present invention has great flexibility in terms of the heating and cooling cycles that can be applied to the solid material while obtaining the benefit of using heat recovered from the solid material that is undergoing the cooling cycle to heat the solid material that is undergoing the heating cycle.
By way of example, the method can be used to upgrade a solid carbonaceous material, such as coal, by the combined application of pressure and temperature which removes water from the coal in two stages, with:
(i) water being “squeezed” from the coal and drained as a liquid phase to a lower section of the vessel in a first, “wet”, stage; and
(ii) a substantial part of the remaining water in the coal being removed as a vapour phase in a second, “dry”, stage.
The heat transfer fluid may be any suitable fluid for transferring energy by indirect heat exchange.
By way of example, the heat transfer fluid may be a fluid, such as oil, that is a single phase in the operating temperature range of the heating and cooling cycles.
By way of further example, the heat transfer fluid may be a fluid, such as water, that is in liquid and gaseous phases in the operating temperature range of the hea ting and cooling cycles and at suitable pressures.
The method may comprise one or more additional heating stages to complete the heating cycle.
The method may comprise one or more additional cooling stages to complete the cooling cycle.
The additional heating stage(s) may be provided by any suitable means, such as by oxidative heating in the vessels by supplying an oxygen-containing gas to the vessels.
The additional cooling stage(s) may be provided by
K-Fuel L.L.C.
Toomer Cephia D.
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