EP1257345A2

EP1257345A2 - Gas purifier device with foam absorbent

Info

Publication number: EP1257345A2
Application number: EP01906118A
Authority: EP
Inventors: Ekaterina Klark
Original assignee: Klark Srl
Current assignee: Klark Srl
Priority date: 2000-02-15
Filing date: 2001-02-12
Publication date: 2002-11-20
Also published as: WO2001060498A3; ITFI20000026A0; WO2001060498A2; ITFI20000026A1; IT1314480B1; AU2001234081A1

Abstract

A container (1) is divided into a lower chamber (1A) for the entry of the gas and an upper chamber (1B) for the outlet of the purified gas, by means of a separating diaphragm (3) which forms a collector for the absorbent foam and liquid; a tubular wall (5) passes through the diaphragm and delimits the operating area (5A) through which passes the gas to be purified, which enters a static bladed centrifugal separator (7); at least one duct (13) for supplying foam opens into the lower part of said operating area (5A); the purified gas is separated by a centrifugal effect from the foam, which is collected by gravity in the partition (3) so that it can be recycled.

Description

GAS PURIFIER DEVICE WITH FOAM ABSORBENT

DESCRIPTION

The invention can considerably increase the efficiency of the removal of all types of harmful impurities from gases, and can be used in chemical and metallurgical processes and in other industries, and in particular it enables aerosol particles of vapors and dusts to be removed from gases.

According to the invention, efficient purification is achieved by means of the interaction of the gaseous and liquid phases and of the impurities with the foam, which takes place as a result of turbulence in the operating area of the rising fluid consisting of gas and foam.

Gas purifying installations of both dry and wet types are known and are in use: centrifugal and cyclone devices are widely used for preliminary or coarse purification, and installations (absorbers) in which harmful impurities are extracted from the gas by means of absorbent liquid are used for fine purification processes. The use of absorbers is more widespread, since their efficiency is greater than that of cyclones. (See USSR Inventor's Certificate No. 333848 held by A.M. Yurlov and Y.G. Yaroshchenko, "Efficient wet dust extractors", Sverdlovsk, 1990). The known absorbers are of various types. They are generally bulky, have a complicated structure, and require spray nozzles, absorbent circulation pumps and absorbent collection containers. Known absorbers operate on the principle of interaction of the gas and absorbent phases in countercurrent and usually with low relative velocities of less than 4 m/s.

The absorber device most similar to that described herein is a Venturi absorber (Wet Scrubbers, by Kenneth C. Schifftner and Howard E. Hesketh, Ann Arbor Science Publishers Inc., Washington, USA, 1983); in this device, the velocity of the gas in the neck of the Venturi spray tube can be as much as 12 m/s, enabling the efficiency of purification to be considerably increased, although the disadvantages mentioned above are still present. A Venturi absorber cannot be used to purify gases by removing dusts which tend to create foam suddenly or which have agglomerative properties.

According to the invention, in order to avoid the aforesaid disadvantages and to achieve other objects, a main chamber of the absorber contains a horizontal partition, in the center of which is placed a vertical tube which forms the operating area, in other words the passage and contact area; projecting into this tube are foam recirculating ducts whose ends are cut off at an angle and positioned near the center of the tube, while their other ends open above said partition. Thus the foam absorbent is fed into the tube and recycled through these ducts. In the upper part of the tube, forming the operating area, there is a static bladed centrifugal separator which is used to centrifugally separate the foam containing harmful impurities extracted from the gas, while the gas which has been thus purified is removed upward and returned to the environment or sent to a consumer.

The absorbent foam and liquid enter the operating area where it is mixed with the gas to be purified thus creating the foam, and the impurities are transferred from the gas into the foam in conditions of turbulent flow of the foam; the purified gas is separated from the foam at the outlet from the centrifugal separator, by the centrifugal effect, as a result of which the purified gas is emitted, while the particles of foam and liquid containing the impurities are collected, as a result of the centrifugal effect and the effect of gravity, in the partition and recycled into the operating area by the flow of incoming gas for purification.

In one advantageous embodiment of the absorber device, the absorbent substance which it contains is taken from above the partition and then enters the lower part of the operating tube. The kinetic energy of the gas arriving in said tube from below entrains the absorbent, thus breaking it up into a foam, and raises it in the tube in a turbulent flow. Neither pumps, whether high-power or otherwise, for spraying the absorbent, nor sophisticated spray nozzles achieve the above, and moreover the dimensions of the absorber purifier device are very small, since the velocity of the gas in the tube spontaneously attains 20 m/s, which is markedly higher than the velocity reached in known devices. Thus the present invention makes it possible to construct an absorption device which is free of the aforesaid disadvantages.

These objects are achieved by the interaction of the gas, harmful impurity, and foam phases, flowing in the same direction and in conditions of high velocity (up to 20 m/s) in the turbulent rising flow of gas and foam in the tube which in practice forms the operating area of the absorber.

The invention is additionally defined by the claims which follow the present description.

The invention will be more clearly understood from the description and the attached drawing, which shows a practical example, without restrictive intent, of the invention. In the drawing,

Fig. 1 shows a first embodiment, in vertical section; Fig. 2 is a section through ll-ll in Fig. 1 ; Fig. 3 shows a second embodiment, in vertical section; and Fig. 4 shows, in isolation, a view of a bladed centrifugal separator which is applicable to the invention.

In the drawing (see Figs. 1 , 2 and 4 in particular), the number 1 indicates a main container, divided into a lower chamber 1A and an upper chamber 1 B by a dividing diaphragm 3; the center of said dividing diaphragm 3 is pierced by a vertical tubular wall 5 which forms the operating area 5A; the diaphragm 3 forms a reservoir for collecting liquid and foam. At the upper end of said tubular wall 5 there is fixed a static centrifugal separator 7 which has (see also Fig. 4) a set of shaped blades 7A capable of imparting an essentially centrifugal acceleration in the direction f7 to the flow of the fluid which reaches it by rising within the tubular wall 5; the blades 7A are located between an upper wall 7A and an optional lower rim 7C. The blades 7A can be vertical (as in Fig. 1), or inclined (as in Fig. 3) to provide an additional action which is inclined with respect to the radial direction. The gas to be purified reaches the lower chamber 1A from a lower inlet 9, and passes through the operating area 5A and the centrifugal separator 7 to reach the chamber 1 B and pass out, in the purified state, through an upper discharge aperture 11. ln order to circulate the active foam used for the purification, the lower part of the tubular wall 5 is penetrated by small tubes 13, which start from the diaphragm 3 and which terminate within the operating area 5A formed by the tubular wall 5, with their outlet ends cut at 30° or 45° with respect to the horizontal, in the central space of said operating area 5A and with the inclined outlets facing upward. To create a closed circulation, the small tubes 13 are supplied with the foam-creating and absorbent liquid D which is collected above the partition 3, in the base of the chamber 1 B. The absorbent is drawn off by the small tubes 13 and passes into the operating area 5A where it creates the foam as a result of the accelerated movement produced in the fluid rising in said area 5A. The level of the absorbent on the partition can be kept constant by automatic control means.

The gas which contains harmful impurities and is to be purified is introduced into the lower chamber 1 A and passes to the inside of the tubular wall 5 in the operating area 5A, where the velocity of the gas increases sharply as a result of the decrease of the outflow cross-section towards the top. At the same time, the absorbent enters the operating area 5A through the small tubes 13, and in these conditions it creates the foam. Owing to the kinetic energy of the gas traveling at high speed, the foam is mixed intensively with the gas to be purified. As the gas and foam rise in the operating area 5A, there is a partial breakdown of the foam which has incorporated the suspended particles and which finally enters the centrifugal separator 7; at this point a powerful centrifugal action is produced, which separates the purified gas phase from the foam and liquid phase. This is because the velocities decrease abruptly at the exit from the blades of the separator 7. The purified gas, being the lighter phase, rises again and is removed through the discharge aperture 11 and can be expelled into the environment or used in other ways, while, as a result of the action of the separator 7 and the centrifugal forces generated in the separator 7, the liquid and foam particles with the impurities incorporated in them are diverted from the flow of the outgoing gas, and fall, being collected in the partition 3, from which they pass again through the tubes 13 into the operating area 5A, in a continuous cycle. When a certain concentration of particles in the foam is exceeded, the saturated absorbent is replaced on the partition, by an automatic or manual process.

According to the invention, the absorber can be used to completely purify even those gases which contain harmful dusts which tend to create foams rapidly, for example where detergents are present; the known absorbers cannot be used in these cases. For these purposes, the absorber according to the invention can be constructed in the variant embodiment shown in Fig. 3. The small tubes 113 - which are equivalent to the small tubes 13 in the solution described previously - leave the body 1 of the absorber above the diaphragm 3, with an upper connection 113A in a position approximately 5-10 mm above the level of the liquid absorbent A collected on the diaphragm 3, and with a lower connection 113B positioned below this level, and fitted with a valve 115. There are also two sensors, namely a maximum one 117 and a minimum one 119, which can detect when the level of the foam D exceeds a maximum level or falls below the minimum level. These sensors can be used to cause the closing or opening of the valve 115. Thus the surplus foam D on top of the liquid of the absorbent can be excluded, and the foam level can be returned to above the minimum level by controlling the supply of liquid A supplied through the valve 115 to at least one of the ducts 113. If the foam rises above said level of the absorbent liquid, the control valve 115 is automatically operated by means of the sensor 117, and prevents the entry of the absorbent liquid into the cycle, so that the foam "settles". The sensor 119 can reopen the valve 115 when the absorbent liquid has to be brought back into circulation.

To prevent the absorbent from falling if there is a decrease in the volume of the incoming gas to be purified, the lower part of the tubular wall has an annular diaphragm 5E, designed to have an appropriate internal diameter.

The absorber according to the invention has been tested in conditions of industrial use. In the test installation, the purification process matched industrial conditions. Calculated concentrations of harmful impurities such as organic solvent or dust were introduced into a pure gas delivered by a fan. The purification efficiency in the test installation reached not less than 98% to 99%, with approximately 3000 m³/hr of gas to be purified. The overall size of the system is much smaller than that of an absorber of any other known type.

The advantages of the present absorber also include the possibility of achieving a high rate of efficient purification across a wide range of harmful impurities, using equipment of simple construction and small size. It is to be understood that the drawing shows only an example provided solely as a practical demonstration of the invention, and that said invention can be varied in its forms and arrangements without departure from the scope of the guiding principle of the invention. The presence of any reference numbers in the attached claims has the purpose of facilitating the reading of the claims with reference to the description and to the drawing, and does not limit the scope of protection represented by the claims.

Claims

1. A gas purifier device with foam absorbent, characterized in that it comprises: a container (1) divided into a lower chamber (1 A) for the entry of the gas and an upper chamber (1 B) for the outlet of the purified gas, by means of a separating diaphragm (3) which forms a collector for the absorbent foam and liquid; in a central position of the diaphragm (3), a tubular wall (5) which delimits the operating area (5A) of the foam, through which the gas to be purified passes; on said tubular wall (5), a static bladed centrifugal separator (7), and, in the lower part of said operating area (5A), at least one duct (13) opening therein to supply absorbent foam and liquid, by means of which absorbent foam and liquid enters the operating area (5A) where it is mixed with the gas to be purified,

2. The device as claimed in claim 1 , characterized in that it comprises a plurality of ducts (13) which open into the lower central part of the operating area (5A), with its outlet ends cut at angles of 30° to 45° to facilitate the entrainment of the absorbent by the ascending flow of gas.

3. The device as claimed in claim 1 or 2, characterized in that, in order to prevent the absorbent from falling if the rate of flow of gas in the operating area (5A) decreases, the tubular wall (5) delimiting the operating area (5A) has an annular retaining diaphragm (5E) in its lower part.

4. The device as claimed in at least one of the preceding claims, characterized in that it comprises a branch (113B) for drawing off absorbent liquid, fitted with a manually or automatically controlled valve (115).

5. The device as claimed in claim 4, characterized in that said valve (115) is operated by at least one level sensor (117 and/or 119) provided above the dividing diaphragm (3).

6. A gas purifier device with foam absorbent, the whole as described above and represented by way of example in the attached drawing.