SE515625C2 - Device and method for purification of gas - Google Patents

Abstract

The invention concerns an apparatus for purifying gases, comprising a column (2), inlet and outlet means (3 and 4, respectively) for introduction of and removal of gases to and from the column (2), a group of trays (5a-5e) arranged sequentially inside the column (2) and so as to be filled with a fluid (10) by way of feeder pipes, and a fan (6) for conveyance of gas through said column (2). The fan (6) is adjustable as to its rotational speed and that parts of said group of trays (5a-5e) are provided with individually controllable fluid feeder pipes (7a-7e), preferably intended for supply of water, to allow essentially individual filling of said trays (5a-5e). The invention likewise concerns a method for optimising a gas purification appartus (1) comprising a column (2), inlet and outlet means (3 and 4, respectively) for introduction of and removal of gases to and from the column (2), a group of trays (5a-5e) arranged sequentially inside the column (2) and so as to be filled with a fluid (10) by way of feeder pipes (7a-7e), and a fan (6) for conveyance of gas through said column (2), said method comprising the steps of establishing (101) a flow of gas by way of the inlet (3), regulating (102) the rotational speed of the fan (6) to ensure that the flow volume of the fan essentially coincides with said gas flow, and individually regulating (103) the intake of fluid, preferably water, to parts of said group of trays (5a-5e).

Description

»- .., lO 15 20 25 30 35 515 625 2 en. This dimensioning is done on the basis of the desired gas purification capacity, incoming flows etc. In galvanizing plants, for example, however, this dimensioning can cause problems. In order to obtain efficient treatment when the plant is fully used, and consequently the largest amount of pollutants is formed, the plant must be dimensioned for maximum flow. This means that the suction of the fan must be large enough for a large amount of gas and that the number of bottoms in the column must be so large that a sufficiently large contact area between gas and water, for purification of this large amount of pollutants, is obtained. In this type of plant, however, the need for purification is maximum only for short periods of time, for example when immersing a galvanizing object in a zinc melt. Between these dips, the amount of pollutants in the gas is much smaller, but not insignificant. There is thus a desire to purify these gases as well. However, this is very costly, because the fan, due to the dimensioning of the system, must be run at full speed, in order to be able to suck the polluted gas through the bottom column. If the fan is run at a lower speed, the cleaning thus stops.

Object of the invention The object of the invention is thus to provide a purification device which allows a good purification of polluted gases at both small and large gas flows.

Summary of the invention This and other objects are achieved according to the invention by means of a device of the kind initially stated which has the features which appear from the appended claim 1 with preferred embodiments in the appended claims 2-6. The object is also achieved by a method according to the following claims 7-9.

The device according to claim 1 is characterized in that the fan is adjustable to the speed and that parts of said group of bottoms are provided with individually controllable 10 15 20 25 30 35 u. N. -. u .. ~. i -. - | -. u. a | v f. -. -. f. u. r v - u. n. s. v- -. «v. n n. - 1>. . v v 1 1. . H U 3 fluid inlet, preferably for water, for substantially individual filling of the bottoms. This individual filling option, in connection with the adjustability of the fan, enables the number of active bottoms to be regulated, depending on temporary needs. At maximum flow, all bottoms are filled to achieve maximum purification. At smaller flows, the fan speed is reduced, and the inlet to a number of bottoms is interrupted, whereby the resistance that the flow experiences when passing these bottoms is very small. The total flow resistance of the device is thereby reduced, whereby the fan is able to keep the flow going. Even at the same flow, but with less contaminants, the number of active bottoms can be reduced, thanks to a smaller need for treatment. This control can be arranged so that each bottom has an individual fluid inlet. Furthermore, according to a preferred embodiment of the invention, the amount of gas entering the column through the inlet is variable.

Preferably, two or more separate gas ducts are connected to the inlet and the flows from these gas ducts to the inlet are further individually controllable by means of dampers, valves or the like arranged in each of the gas ducts. lead polluted gases from two or more different gas sources. Preferably, the gas channels are arranged to lead to the inlet for purification in a common gas purification device. These may, for example, be gases from pretreatment or zinc dipping at a galvanizing plant. In this way, the device can partly be used for purification of the highly polluted gases that arise during zinc dipping, but also of the less polluted gases that arise in connection with pre-treatment. Thanks to the dampers, the flow from, for example, the pretreatment can be shut off during zinc dipping, in order to achieve maximum purification of the heavily polluted gas thus produced. The location of the dampers can also be used to determine the speed of the fan, and thus the number of active bottoms. 5 15 20 25 30 35 515 625 4 According to a further preferred embodiment, a pump is arranged for pumping fluid, via a fluid line common to two or more fluid inlets, to said fluid inlet, so that the pump only pumps exactly as much fluid as and the strength of the pump is adjustable. This is needed to fill the currently active bottoms, which allows for reduced operating costs.

Preferably, the bottoms of so-called bell bottoms are forced to type, whereby the gas passes freely past a bottom, which fluid inlet is prevented, pass through a fluid layer at a bottom, to which fluid inlet takes place, whereby the gas flow resistance of the device is controllable.

The method according to claim 7, for optimizing a gas purification device comprises the steps of determining a gas inflow through the inlet, regulating the speed of the fan, so that the extraction volume of the fan substantially coincides with said gas inflow, and individually regulating the inflow of fluid, preferably water, to parts of said group of bottoms. This method achieves the previously described advantages. Further preferred embodiments of this method are described in the appended claims 8-9.

Brief Description of the Drawings The invention will be described in more detail in the following with reference to the accompanying drawings, which for exemplary purposes show a presently preferred embodiment of the invention.

Fig. 1 is a schematic view of the scrubber system in which the device and the method according to the invention are implemented.

Fig. 2 is a flow chart and describes a method for optimizing a gas purification device according to the invention.

Fig. 3 shows details of the flow chart of Fig. 2 in accordance with the present invention.

Fig. 4 shows further details of the flow chart of Fig. 2 in accordance with the present invention. Description of Preferred Embodiments The system shown in Fig. 1, intended for implementation in a galvanizing plant, comprises a scrubber-type gas purification device 1, three gas sources 13a-13c, in this case a first zinc pot 13a , a second zinc boiler 13c and a pre-treatment line, shown in Fig. 1 as a pre-treatment vessel 13b, intended to conduct polluted gases from the gas sources 13a-13c and gas ducts 11a-11c, which are to the gas cleaning device 1. In each of the gas ducts 11a llc is a damper l2a-l2c located. The gas cleaning device 1 further comprises a column 2, having an inlet 3 and an outlet 4. The inlet 3 is connected to said gas ducts 11a-11c. The inlet opens into the lower part of the column, but with a certain distance to the bottom of the column. The outlet 4 is located in the upper part of the column 4 and the column 4 is placed substantially vertically.

At the outlet, a fan 6 is further located. Inside the column, five bottoms 5a-5e are located, and each of these bottoms 5a-5e covers the entire cross-sectional area of the column 2.

The bottoms 5a-5e are further arranged in series along the longitudinal direction of the column 2, at a mutual distance from each other.

In this exemplary embodiment, the bottoms 5a-5e are of the so-called bell bottom type. reaches an inlet 7a-7e, which is regulated by means of a valve in connection with each bottom 5a-5e opening 14a-14e. These inlets 7a-7e originate in a common inlet line, which leads a fluid 10, in this case water, pump unit 8 to the respective valve 14a-14e at and from the lower part of the column 2, respectively, via an inlet 7a-7e. In addition, the gas purification device comprises a bottom outlet 15 for emptying sludge, a water filling line 16, for replacement of evaporated water and a drip separator 17, but these elements have no real significance for the invention as defined by the following claims.

During operation of the system, it is determined which flow of polluted gases is to be purified by opening and closing the dampers 12a-122c, respectively. This flow originates from one of the gas sources 13a-13c or from a combination of these. For example, the first zinc pot 13a may be the main one in the galvanizing plant, in which large objects to be galvanized are immersed, whereby large amounts of contaminants are generated from this pot for a limited period of time. The two other sources, i.e. the second zinc pot 133 and the pretreatment line / pretreatment vessel 13b, in this embodiment give rise to significantly much smaller amounts of contaminants, over longer periods of time. With the above-mentioned dampers 12a-12c, there is thus the possibility of controlling the plant for purification of the flows where it is currently most needed. The gas ducts 11a-11c open after the dampers l2a-l2c in a common duct leading to the inlet 3 of the gas purification device 1, the gases being led from the current gas source / current gas sources into column 2. Depending on which inflow one is and how polluted this flow is , has entered the column, the speed of the fan 6 is regulated, in order to optimize the suction power of the fan 6 relative to its power consumption. In connection with the regulation of the fan's 6 speeds, the number of active bottoms is also regulated. The total number of bottoms N is dimensioned according to the maximum suction capacity of the fan 6 and at lower speeds of the fan 6 it is unable to draw air through all the bottoms. The regulation takes place in such a way that the inflow of water via the inlets 7a-7e is stopped by means of valves l4a-l4e for the X top bottoms, where X depends on the fan speed, whereby the water level of these X top bottoms drops to such a low level that air can pass the bottom substantially without being forced through a resistive water layer. As a result, the number of active bottoms has dropped from N to N-X, and the gas can pass through the column, even at smaller flows. This means that the device is useful for purifying both larger, highly polluted gas flows and smaller flows of gas with small pollutant contents. The power consumption of the plant can be further reduced further, by letting a common pump pump water to the inlets 7a-7e. The pumping power of the pump 8 can thus be regulated, so that the fluid line 9 connected to the pump 8, which leads to the inlets 7a-7e, only delivers the amount of water required for filling the NX active bottoms, which results in an outer - more efficient power saving.

Fig. 2 shows a block diagram of a method for optimizing a gas purification device. The method essentially comprises three steps, determining 101 of the inflow volume of gas through the inlet to the column, regulating 102 the fan speed so that its extraction volume corresponds to the inflow volume and regulating 103 of the inflow of fluid, in this case water, the bottoms. It should be noted in particular that these three steps individually to each of may not necessarily take place in this order, but the method steps depicted in Fig. 2 and subsequent Fig. 3 and Fig. 4 are shown for illustrative purposes only. The step of determining the inflow may, for example, consist of the steps of regulating the inflow by individually regulating dampers arranged in each gas duct and of determining the gas inflow through inlet by determining which dampers are open, as shown in Fig. 3.

Furthermore, the step of controlling 103 the inflow of fluid individually to each of the bottoms may comprise the steps of feeding 301 a plurality of fluid inlets via a common fluid line, pumping 302 fluid through the fluid line with a pump / one of the bottoms by opening and closing a wide one, respectively. control 303 the individual inlet to each of the valves disposed and control 304 the power of the pump to pump the amount of fluid required to feed the actual open fluid inlets, as shown in Fig. 4. Suitably, the various method steps are applied. on the above-mentioned device, controlled from a central computer unit or the like (not shown). For example, an operator can decide that a dip in the first (large) zinc pot 13a should take place, whereby the purification in the device should be concentrated to polluted gases from this process. 10 15 20 25 30 515 625 8 The operator sends, for example by pressing a button on a control panel, this information to the control unit, after which the control unit sends an opening signal to the damper l2a and / or closing signals to the dampers l2b-l2c. In this case, only the gas from the first zinc pot 13a is led into the purification device. Thus, the flow through the device is also determined, and the control unit sends a control signal to the fan 6 for adjusting its speed to the actual flow. Furthermore, the control unit determines how many active bottoms N-X are required for said flow, and transmits closing signals to the valves 14 belonging to the X uppermost bottoms. The control unit also calculates the water supply required to fill the active bottoms, and then sends out a signal for regulating the pump strength of the pump 8.

It will be appreciated that a variety of modifications of the above-described embodiments of the invention are possible within the scope of the invention, as defined by the appended claims. For example, the pump 8 may be unregulated, and constantly pump the same flow to the inlets 7a-7e. Furthermore, the number of gas sources 13 and associated gas ducts 11 and dampers 12 can be varied on the basis of the design of the plant. Furthermore, the total number of bottoms can vary, for adaptation to the maximum flow through the device, for example when all dampers 12 are open. Furthermore, the fluid inflow of the bottoms can be regulated individually to each bottom, or individually to subgroups of said group of bottoms. As previously mentioned, the method steps can take place in different order, and to a certain extent, for example with regard to regulation of the fan speed and the number of bottoms, take place simultaneously.

Claims (9)

10 15 20 25 30 35 515 625 ~ - «~. . CLAIMS comprising a coil and outlet (4) Device for purifying gas, (2), from the column lonn for gas intended inlets (3) (2), a group of bottoms (5a-5e) arranged serially inside the column (2), are fillable with a fluid (10 ), a gate arranged through the column (2), characterized in that said fan (6) which bottoms via inlet and one for gas transmission (6), is adjustable to (5a-5e) (7a- knene - the speed and that parts of said group of bottoms are provided with individually controllable fluid inlets 7e), for substantially individual (5a-5e), fluid-filled bottoms are adjustable taking into account preferably water, or filling of said bottoms whereby the number of active, to the fan, effective purification of both larger and smaller gas flows. depending on its speed, suction power, for Device according to claim 1, characterized in that the amount of gas entering the column (2) through the inlet (3) is variable. Device according to any one of the preceding claims, characterized in that two or more separate (11a-11c) (3), and that the flows from these gas ducts (11a-11c) to in- are individually controllable by means of each ( lla-1lC) gas ducts are connected to said inlet bore (3) by the gas ducts arranged dampers (l2a-l2c), valves or the like. Device according to claim 3, characterized (11a-11c) polluted gases from two or more different gas sources in that said gas ducts are arranged to lead (13a-13c), for example from different processing steps in the case of galvanizing, to said inlets (3) for purification in a common gas purification device (1). Device according to any one of the preceding claims, characterized in that a pump (8) is arranged for pumping fluid (1), via one for two or more fluid (7a-7e) (9), common to said inlet. fluidledning 10 l5 20 25 30 35 515 625 zšhwšsjjfa. >.> .... _ ¿= - u n. 10 fluid inlets (7a-7e), and that the flow of the pump (8) is controllable. Device according to any one of the preceding claims, (5a-5e) called bell bottom type, wherein the gas passes freely past characterized by said bottoms is of such a bottom (5a-Se) to which fluid inflow is prevented, but is forced to pass through a fluid layer at a bottom to which fluid inlet takes place, the gas flow resistance of the device (1) being controllable. Method for optimizing a gas purification device From the column for gas inlets (2), arranged bottoms (1), comprising a column (3) to and outletP (4) serially inside the column (2) (7a-7e) a group of (Sa-5e), which via inlet are fillable with a fluid (io), nad fan (6) comprising the steps of: determining (101) (102) desvolume substantially coinciding with said gas inflow, and one for gas transport through the column (2 ) arrange a gas inflow through the inlet, regulate the speed of the fan, so that the flow of the fan and (103) precede parts of said group of bottoms. individually regulate the supply of fluid, preferably water, A method of optimizing a gas purification device (1) (101), a gas inflow through the inlet further comprising the steps of: (201) individually opening and closing dampers or valves, respectively, according to claim 7, wherein the step of determining regulates the gas inflow through the inlet by means of in two or more gas channels, opening at the inlet, and determining (202) to determine which dampers are open. the inflow of gas through the inlet through A method for optimizing a gas purification device according to any one of claims 7 or 8, wherein the step of individually (103) to parts of said group of bottoms, further individually regulates the inflow of fluid, preferably water, comprises the steps of: feeding (301) a plurality of fluid inlets via a common fluid line, pumping (302) fluid through said fluid line by means of a pump, directing (303) the individual fluid inlet to each part of said group of bottoms by opening or closing a vein and control (BO4) arranged at the respective fluid inlet (BO4) of the pump to pump substantially the amount of fluid required to supply the relevant open fluid inlets.