Compositions: coating or plastic – Coating or plastic compositions – Inorganic settable ingredient containing
Reexamination Certificate
1996-08-14
2002-10-22
Marcantoni, Paul (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Inorganic settable ingredient containing
C106S709000, C106S739000, C106S745000, C106S758000, C106S763000, C106S767000, C106SDIG001, C060S645000, C060S648000
Reexamination Certificate
active
06468345
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a process for producing both steam power and cement clinker simultaneously in one apparatus, to the apparatus composed mainly of a coal-powder-burning boiler system which is especially designed to embody said process, to the cement clinker obtainable by said process and also to the use of this cement clinker, the present invention further relates to a process for producing both steam power and a fast-burnt modified coal ash simultaneously while the coal powder is burning in the furnace, to the fast-burnt modified coal ash obtainable by this process, to the apparatus composed mainly of a existing coal-powder-burning boiler system for carrying out this process, to the use of this modified coal ash as cement clinker, and to the use of the existing coal-powder-burning boiler system in production of the fast-burnt modified coal ash, the present invention still further relates to a process for desulfurization from the flue gas of the coal-powder-burning boiler.
Cement is one of the three fundamental materials of the construction industry, it is widely used in a great amount. The most commonly used is portland series cement, GB 175-92 is referred to as its chinese national standard.
The principal raw material for the production of cement clinker is lime stone, clay and iron powder, the fuel used is mainly coal. The active component of the cement clinker is mineral composition comprised mainly of calcium silicates which can be formed usually at 1450° C., or at 1300° C. while mineralizing agent is added thereinto. The main segments for cement production can, whatever a process and a kiln is used, be summarized as “two pulverizing and one burning”, namely, the three basic procedures: raw material blending and pulverizing; clinker burning; and cement pulverizing.
FIG. 1
is a layout of the rotary kiln technological flow chart for an advanced out-of-kiln predecomposition dry process wherein the most critical apparatus is the clinker burning rotary kiln. In the clinker burning procedure, fuel and raw material are respectively fed into the kiln; the coal powder is injected into the burning kiln through a burner at the kiln end of clinker discharge, a flame like a head of Chinese writing brush is formed at the position of the central line with its high temperature flame up to 1600° C.-1700° C., heat is transferred by means of convection and radiation to the materials advancing in stacks as the kiln rotates and having a filling rate of about 12-14% in the rotary kiln. There exist two main problems for such heat transfer: one is its low heat efficiency, generally only about 22%, even the advanced out-of-kiln predecomposition rotary kiln dry process has its heat efficiency but up to about 50%; the other is its inhomogeneous heat transfer because the materials is in stacks, causing a longer period of time for the procedures from entry of raw material in the kiln to formation of clinker as well as its cooling (generally it needs about 1.5-2 hour, the out-of-kiln decomposition kiln also needs 40 minutes to 1 hour). The characters of this technology can be summarized as “slow burning and slow cooling”; additionally, the clinker is also likely to be over-burnt. The existance of very high burning temperature, inhomogeneous burning and over burning cause a negative influence on cementitious mineral activity and finally influences the performances of the cement clinker. In addition to the above-indicated defects such as high energy consumption, inhomogeneous heat transfer affecting negatively its product quality because the heat transfer is not well, the cement production further brings forth other problems such as consuming huge amount of mine resources, occupying much land, spending large amount of materials transportation coast and resulting in environmental pollution as of land, water source, atmosphere etc.
Coal-powder-burning boiler system is an apparatus widely used for producing steam power, high temperature and high pressure steam produced can be used, for example, for electrical power generation or other purpose. Its principal apparatus flowchart is shown in FIG.
2
. It can be seen from
FIG. 2
that the coal powder burning boiler system is mainly composed of the following subsystems: Raw coal blending system (including
1
,
2
,
3
), coal pulverization system (including
4
,
5
,
6
), coal powder convey and combustion and heat supply system (including
7
,
8
,
9
,
10
), and by-product treatment system (including
11
,
12
,
13
). Among them, the main device is the coal-powder-burning boiler (
9
). The coal powder, after being injected by a burner into the furnace chamber, is in a form of highly disperse and fludized suspension; while contacting with and being heated by the gas flow of high temperature in range of 1300-1600° C. in the furnace combustion zone, the said coal powder burns and release heat; the high temperature and high pressure steam produced in the boiler can be directly used for driving turbine and/or other power or thermal engineering apparatus. The residence time of coal powder or its ash substances in the high temperature zone of furnace chamber averages generally about 2-6 seconds with the possibly highest reaching 8 seconds. The coal ash formed exits the furnace chamber along with the flue gas flow at the temperature of about 1200° C. and enters the dust-containing flue gas duct, and carries out indirect heat exchange with the steam, feed water and blowing-in air of the boiler, during this procedure, the formed coal ash cools down quickly and homogeneously, and then enters in the electrical dust-remover (
11
) and is collected therein. Meanwhile, a small amount of slag fall down to the bottom of furnace and is quenched by water and then collected and discharged. The characters of this process, i.e. the fast burning and heat releasing in the furnace, and the fast formation and cooling down of the coal ash and slag can be summarized as “fast-burning and fast cooling; the collected coal ash is usually delivered hydraulically into the specially-built ash pits (
13
) and/or pneumatically into the tanks for storage; after coal ash is removed, the exhaust gas containing a minor amount of coal ash dust and some SO
2
is emitted into the atmosphere.
Such a coal-powder-burning boiler has large heat-transfer area and large heatransfer coefficient, so its thermal efficiency can reach 90% or even ligher. However, the operation of such coal-powder-burning boiler brings forth two rather serious problems: one is: a large amount of by-produced coal ash gives rise to rather serious pollution, e.g., a 850 mw thermal power plant will spend each year 20 millions RMB or more and occupies much land for building or extending works of ash piling pits, will consume much water and power for transporting coal ash, and will pollute the environment because the coal ash flies with the wind or leaking along with rain water from the ash piling pits; the other is that the exhaust gas emitted from the chimneys carries rather large amount of SO
2
and the residue of fly ash into air which also cause atmospheric pollution.
Since a long term, many approaches have been researched and developed in order to treat and utilize comprehensively the waste ash and slag collected from the coal powder-burning boiler. Among them, the main one is to use it as an admixture i.e., the filler to produce coal ash cement, but the addition of coal ash is generally limited to 20-40% (refer to GB 1344-92), so both the rate and the value thereof are not high; further, the coal ash transporting from the steam powder plant to the cement works needs again large amount of transport fee. One of the main reasons which causes the addition of coal ash being incapable of going beyond 40% is that the coal ash turns out to be a kind of pozzolan, featuring a chemical composition of Si-riched and Ca-lack, it has some potential hydrauric cementitious activity. In order to develop such a potential activity, many measures have been taken, but these measures mostly have been directing to
Liu Ben'en
Zhu Xuefang
Marcantoni Paul
Reed Smith LLP
The Chinese Academy of Sciences
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