DE3539466C1 - Installation for dewatering a solids-laden liquid - Google Patents

Abstract

In an installation for dewatering a solids-laden liquid, especially a gypsum suspension from a flue gas desulphurising installation, comprising at least one hydrocyclone and a screen centrifuge downstream of the hydrocyclone, the invention provides, in order to improve the installation in respect of the feeding of solids-laden liquid to the screen centrifuge for optimum operation of the latter, that a vessel (6) to receive the underflow of the hydrocyclone is arranged upstream of the screen centrifuge (10), into which vessel a feedline (7), equipped with a regulating valve (9), for water for diluting purposes terminates, with the regulating valve (9) being regulated as a function of the density of the solids-laden liquid flowing in a line (12) between the vessel (6) and the screen centrifuge (10), and by the liquid level in the vessel (6), a line (8) being branched off the line (12) and leading back to the vessel (6). <IMAGE>

Description

The invention relates to a system for drainage a solid-laden liquid, in particular Gypsum suspension from a flue gas desulfurization plant, consisting of at least one hydrocyclone and one Hydrocyclone downstream screen centrifuge.

From the applicant's prospectus on environmental technology "Flue gas cleaning" P 83 02-14-06 / 0.5 N / S is known one occurring in a flue gas desulfurization plant Solid loaded liquid, especially a Gypsum suspension, in an apparatus combination either in a hydrocyclone with a vacuum filter or in one Dewater pre-thickener with a centrifuge. in the If a pre-thickener is combined with a Centrifuge is like a clarifier thickener with a Sieve centrifuge proven. For reasons of space and the energy expenditure of such a system is available however, at least one instead of the clarifier Use hydrocyclone as a pre-thickener. A such a combination of devices is already in the essay by W. Gundelach - H. F. Trawinski "The Hydrocyclone" in Chemical engineering technology, 32nd year, (1960), No. 4, Pages 279-284. This combination has one low space requirement and energy consumption,  with a liquid after the hydrocyclone a high solids content, the originally existing and outgoing in the cyclone overflow Fine grain content is missing. Through this versus Clarifier thicker enriched solid Liquid will increase the performance of the centrifuge enables.

With this system, however, can uncontrolled supply of solids loaded Liquid and / or when the load changes Flue gas desulphurization plant the lower reaches of the Hydrocyclones both in volume flow and in solids content Strengthen the solid-enriched liquid Subject to fluctuations, with which the drainage of the Solid enriched liquid in the Sieve centrifuge can be difficult.

The invention is based on the object improve the system so that the screen centrifuge that solid-laden liquid is supplied, the optimal operation of the drainage system guaranteed.

This object is achieved in that the Sieve centrifuge to hold the underflow of the Hydrocyclone provided container is connected upstream one equipped with a control valve Delivery line for dilution water opens, the Control valve depending on the density of the between the container and the screen centrifuge in one line flowing, solid-laden liquid and from which Liquid level in the container is regulated and where a line branches off the line and to the container is returned.  

The hydrocyclone can be unaffected by the Sieve centrifuge operated and provides one with Solid enriched liquid, the poor of fine grain. Due to the density and liquid level dependent Dosing of dilution water to the pre-thickened Solid-laden liquid in the container becomes from this the screen centrifuge is a liquid with a whole determined, constant solids content and due to the return line in a constant volume flow fed, making the centrifuge under optimal Operating conditions can be operated.

An embodiment of the invention is in the Drawing shown and is explained in more detail below.

A liquid loaded in a flue gas desulfurization plant working according to a wet process, in particular a gypsum suspension with a high solids content, for example 10% by weight, is fed to a multicyclone 2 via a delivery line 1 . An overflow liquid emerging from the multicyclone 2 and having a solids content of a fine grain fraction reduced to 1.5% by weight passes via a line 3 to a circulating water tank 4 and from there to a further treatment plant, not shown in any more detail.

An underflow liquid emerging from the multicyclone 2 , the solids content of which in the context of this numerical example is 30-50% by weight, flows directly in a line 5 to a container 6 for intermediate storage. Two further lines 7, 8 open into this container 6 . One line 7 is equipped with a control valve 9 and is provided for the supply of dilution water, for example filtrate water from a screen centrifuge 10 and / or make-up water.

In the other line 8 , a branched partial flow of solid-enriched liquid is returned to the container 6 before entering the sieve centrifuge 10 connected downstream of the container 6 , for example a discontinuously operating pendulum centrifuge or a continuously operating peeling centrifuge.

From the container 6 , the solids-laden liquid set to a desired density is conveyed in the direction of the sieve centrifuge 10 by means of a feed pump 11 in a line 12 .

The density is adjusted by a density measuring and control device 13 (density indicating control) in the line 12 and a liquid level measuring and control device 14 (level indicating control) on the container 6 . Both devices 13, 14 each deliver either a control signal directly, the two signals being linked to one for the control valve 9 , or a measurement signal to a computing unit 15 , in which they are processed in a control signal for the control valve 9 . In both cases, an exact setting of the amount of dilution water is possible, while overshooting the control is avoided.

In line 12 there is the branch for the partial flow of the solid-enriched liquid returned in line 8 to container 6 . A valve 16 is also arranged between the branch and the screen centrifuge 10 . In the event that the sieve centrifuge 10 is a discontinuously operating pendulum centrifuge, the valve 16 is opened during the loading process of the centrifuge and closed during the centrifuging process, the solid-enriched liquid being pumped through line 8 in a partial flow or in its entirety. In the event that the screen centrifuge works continuously, the setting of the valve 16 continuously feeds both a constant flow of solids-enriched liquid for dewatering the screen centrifuge 10 and returns a small partial stream via line 8 to the container 6 .

The amounts of substance separated from one another in the screen centrifuge 10 are discharged to further treatment devices, not shown in any more detail.

Claims (2)

Plant for dewatering a solid-laden liquid, in particular gypsum suspension from a flue gas desulphurization plant, consisting of

• - at least one hydrocyclone and
• a sieve centrifuge downstream of the hydrocyclone,

characterized in that the screen centrifuge ( 10 ) is preceded by a container ( 6 ) provided for receiving the underflow of the hydrocyclone, in which a delivery line ( 7 ) for dilution water equipped with a control valve ( 9 ) opens, the control valve ( 9 ) depending is regulated by the density of the solid-laden liquid flowing between the container ( 6 ) and the screen centrifuge ( 10 ) in a line ( 12 ) and by the liquid level in the container ( 6 ), and a line ( 8 ) from the line ( 12 ) branches off and is returned to the container ( 6 ).