Fuel and related compositions – Coal treating process or product thereof
Patent
1998-09-25
2000-07-04
Howard, Jacqueline V.
Fuel and related compositions
Coal treating process or product thereof
44628, 44641, C10L 910, C21B 500
Patent
active
060832894
DESCRIPTION:
BRIEF SUMMARY
This application is the national phase under 35 U.S.C. .sctn.371 of prior PCT International Application No. PCT/JP97/00668 which has an International filing date of Mar. 5, 1997 which designated the United States of America, the entire contents of which are hereby incorporated by reference.
The present invention relates to a transportability improver for pulverized coal which can improve the transportability of pulverized coal to enable the stable injection of pulverized coal into a metallurgical or combustion furnace at an enhanced feed rate, and a process for operating a metallurgical or combustion furnace by the use of the improver.
In the operation of a metallurgical furnace such as a blast furnace, it has been a general practice to charge coke and iron ore into the furnace from the top alternately. However, another operation process has recently been employed frequently, wherein pulverized coal which is inexpensive and excellent in combustibility and exhibits a high calorific value is injected into a blast furnace through an injection port together with hot air to substitute for part of the coke to be charged from the top. This process permits a decrease in the fuel cost, thus being superior to the all-coke operation in this respect.
Further, coal has been reconsidered also as a fuel for combustion furnaces (such as a boiler) substituting for fuel oil. In a combustion furnace, coal is used in the form of CWM (coal/water mixture), COM (coal/oil mixture), pulverized coal or the like. In particular, pulverized coal firing furnaces attract considerable attention, because they can dispense with the use of other media such as water or oil. However, such furnaces as well as blast furnaces have problems resulting from the use of pulverized coal.
Pulverized coal injection is conducted through the steps of preparation of pulverized coal from raw coal by dry pulverization, classification of the obtained pulverized coal, storage of the resulting pulverized coal in a hopper and discharge thereof from the hopper, pneumatic transportation thereof through piping, injection thereof into a metallurgical or combustion furnace through an injection port, and combustion thereof in the furnace, among which the discharge of pulverized coal from a hopper and the pneumatic transportation thereof through piping are accompanied with the problems which will now be described.
That is, the fluidity and other basic physical properties of pulverized coal have significant influence on the discharge and transportation characteristics thereof, while the physical properties vary depending on the kind, particle size and water content thereof. Accordingly, it is difficult to continue the stable injection of pulverized coal having basic physical properties of pulverized coal deviating from the optimum ranges for a long period, because such pulverized coal causes bridging or channelling in a hopper or piping choking in pneumatic transportation.
In order to solve these problems, there have been made attempts to improve the transportability of pulverized coal and various methods therefor have been proposed. Examples of such methods include a method of adding 5 to 20% of char to pulverized coal (JP-A 4-268004), methods of controlling the inert content of coal (the total content of micrinite, 1/3 semifusinite, fusinite and minerals as stipulated in JIS M8816-1979) prior to pulverization (JP-A 5-9518, JP-A 5-25516 and JP-A 5-222415), a method of enhancing the fluidity index of pulverized coal to at least the nominal value of the blast furnace to be used by limiting the kind of the coal (JP-A 4-224610), a method of controlling the coefficient of friction between pulverized coal and piping (JP-A 5-214417), a method of regulating the water content of pulverized coal to a proper level (JP-A 5-78675) and soon. Further, a method of improving the efficiency of pulverization of coal by making a dispersant adhere to the coal has also been proposed in JP-A 63-224744, but this patent document is silent on the transportability of pulverized coal.
However, th
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Ichimoto Takehiko
Kamijo Tsunao
Kimura Yoshio
Matoba Takashi
Miyamoto Ken'ichi
Howard Jacqueline V.
Kao Corporation
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