Conveyors: fluid current – Selective delivery – Destination controlled by sensed condition
Reexamination Certificate
1998-04-17
2001-04-24
Valenza, Joseph E. (Department: 3651)
Conveyors: fluid current
Selective delivery
Destination controlled by sensed condition
C406S155000, C406S183000, C141S236000
Reexamination Certificate
active
06220790
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a process for continuously conveying fine-grained or pulverized solid to two or several target points by means of a conveying medium. The solid is charged into a distribution vessel and, from there, the solid is conveyed to a selected one of a plurality of target points by means of the conveying medium moving the solid via one supply line each in the desired target flow rate. The invention also relates to apparatus for performance of the process.
The process of conveying fine-grained to pulverized solids by compressed air from a distribution vessel to several target points, and especially conveying of coal
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dust to several consumers, such as tuyeres of a blast furnace, is known (DE-A 26 46 130, DE-C -30 50 394 and DE-A -25 37 370). In this process, especially close-grained flow conveying is applied. Coal dust is first pneumatically fed into a distribution vessel at the flow rate in which the coal dust is further delivered from this vessel. From the distribution vessel, several supply lines lead to the several target points, i.e., the tuyeres of the blast furnace. Each tuyere is charged with a material flow conveyed via a separate supply line.
It has turned out that the coal dust in the distribution vessel that acts as a static distributor is distributed to the individual supply lines with a relatively high accuracy (±15% of the desired target flow rate). For instance, the target flow rate conveyed to the target points can be easily adjusted by adjusting the difference between the pressure at the target point and the pressure inside the distribution vessel.
Serious problems will occur if the target flow rate of the solid has to be adjusted or controlled individually for the target points commonly supplied by one distribution vessel. That requires installing control fittings, such as dampers, valves, etc., which allow flow rate adjustment, and mass flow meters in each supply line. However, insurmountable difficulties have been encountered in practice because such control fittings and mass flow meters are subject to extremely high wear from conveying fine-grained or pulverized solids. The failure of one control fitting will cause irregularities at the other target points. The replacement of a control fitting is expensive as conveying has to be interrupted.
SUMMARY OF THE INVENTION
The object of the invention is to avoid these disadvantages and problems and to provide a process for conveying a fine-grained solid of the aforementioned type, where the target points which are commonly fed from one distribution vessel can also be charged with individually adjustable target quantities/unit of time of fine-grained or pulverized solids in a simple way. The process should be low cost, and the facility serving this purpose should be little susceptible to failure and have a long service life.
The invention solves the problem by dividing the target flow rate intended for one target point into two or several partial target flow rates. Each separate partial supply line from the distribution vessel conveys solid by action of the conveying medium, and the flow is divided into several partial flows at the partial flow rate. The partial target flows are reunited at the latest at the respective target point. In order to adjust the target flow rate at a target point to a specific level, the various partial supply lines leading to this target point are alternatively either shut-off or open preferably by respective valves.
The target flow rate intended for a target point can thus be easily selected by summation of the partial target flow rates that are conveyed to this target point by means of the partial supply lines, by keeping one or several of the partial supply lines leading to this target point open or shut off, depending on the desired target flow rate intended for this target point. This is easy to implement because only valves with on/off function are required in the partial supply lines, as these are practically not subject to higher wear than other equipment parts required for executing the process. Special control valves and flow meters may be omitted.
It is expedient to select the same volume for all partial target flow rates intended for one target point, thus ensuring a particularly uniform and trouble free distribution of the partial target flow rates in the distribution vessel.
To graduate the target flow rate intended for a target point not only into equally large volume steps, different volumes as compared to other partial target flow rates are selected for one or several partial target flow rate(s) intended for a target point according to a preferred design.
The process according to the invention can be accomplished particularly advantageously if pressure gas is used as the conveying medium. However, it can also be accomplished if a liquid is used as the conveying medium.
If the target flow rate is to be changed at one target point and the target flow rates are to be kept strictly constant at this target point or the other target points, the flow rate charged into the distribution vessel is preferably changed when the target flow rate intended for the one target point is changed.
Apparatus for implementing this process features a combination of the following features: a distribution vessel into which a supply line for the fine-grained solid to be conveyed and for a conveying medium leads; two or more target points to which fine-grained solids is to be conveyed; at least two partial supply lines leading out of the distribution vessel to each target point; and a shut-off valve each in each partial supply line, which can be set to off or on position.
In a simple and low cost design, the shut-off valves are installed near the distribution vessel and each partial supply line leading to one target point runs into a supply main leading to this target point in the flow direction downstream of the shut-off valves.
The partial supply lines leading to each of the target points advantageously have equally dimensioned cross sections.
A preferred design, which allows for finer graduation of the target flow rates intended for a target point, uses differently dimensioned cross sections of the partial supply lines leading to a target point.
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Kastner Walter-Rainer
Nagl Michael
Schenk Johannes
Dillon, Jr. Joe
Valenza Joseph E.
Voest Alpine Industrieanlagenbau
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