DRYING OF FILTER ELEMENTS IN A FILTER SYSTEM

A filter system including a filter housing with an inlet part, a clean-gas outlet, and a partition wall defining a product chamber and a clean-gas chamber. The partition wall having openings from which filter elements extend downward into the product chamber. The inlet part is placed in an upper part of the product chamber and configured for supplying a product-containing flow of gas to the product chamber. The gas flow being conveyed through the filter elements and into the clean-gas chamber, where the filter system is provided with an air or gas supply placed in the product chamber and configured for leading drying air or gas into or out of the filter system. A method of drying filter elements in a filter system by passing drying air or gas through a filter inlet and/or through a drying air or gas supply.

FIELD OF THE INVENTION

The invention relates to a filter system comprising a filter housing with an inlet part and a clean-gas outlet and further comprising a partition wall dividing the filter housing into a product chamber and a clean-gas chamber, said partition wall being provided with a number of openings from which a plurality of filter elements extends downwards into the product chamber, which inlet part is placed in an upper part of the product chamber and in open communication with the product chamber, and configured for supplying a product-containing flow of gas to the product chamber, said gas flow being conveyed through the filter elements and upwards into the clean-gas chamber, from where the filtered gas is discharged through the clean-gas outlet.

The invention also relates to a method of drying filter elements in a filter system.

BACKGROUND OF THE INVENTION

When cleaning filter elements in a filter housing most often CIP wet cleaning (cleaning in place) is used for cleaning of the filter system including the filter elements. After wet cleaning of the filter system including the filter elements, the filter system must be dried before it can be used again. To dry the filter system including the filter elements, drying air is passed through the filter system and filter elements in the same way as when the filter system is in operation. Heated air is used to speed-up the drying process.

OBJECTIVE OF THE INVENTION

The objective of the invention is to optimize drying of wet-cleaned filter elements by reducing drying time and to ensure that the elements are dry to an acceptable level/extent over the total length of the elements.

Optimizing drying of the filter system including the filter elements after wet-cleaning should be understood as reducing one or more of the parameters comprising temperature, drying time or air or gas flow, still ensuring that the filter elements are dry to an acceptable level/extent over the total length of the filter element.

This is achieved with a filter system where the filter system is provided with one or more air or gas supplies placed in the product chamber below said inlet part and configured for leading drying air or gas into or out of the filter system.

Here air or gas supplies should be understood as capable of leading air or gas into the filter system and/or to leading out air or gas from the filter system.

Filter elements can be filter bags, filter cartridges, filter envelopes or similar elements.

Hereby is achieved a more efficient drying of the filter system and filter elements as well as a significant reduction in drying time and thereby a significant reduction of down-time of a plant in which the filter system is installed, optimizing the production time of the plant.

In an embodiment, the one or more drying air or gas supplies is placed in a lower part of the filter housing and having openings placed below the filter elements.

Hereby it is possible to supply drying gas or air from both ends of a filter element, thereby optimizing the drying process, for example by shortening the drying time for the filter elements.

In an embodiment, the one or more drying air or gas supplies is placed in a lower part of the filter housing and having openings placed at a level corresponding to a lower part of the filter elements.

Hereby it is possible to supply drying gas or air from almost both ends of a filter element, thereby optimizing the drying process, for example by shortening the drying time for the filter elements.

In an embodiment, the one or more drying air or gas supplies is placed in an upper part of the filter housing and having openings directing drying air or gas towards the lower part of the filter elements.

Hereby it is possible to provide drying air or gas from an upper side of the filter housing to the outside of the filter elements.

In an embodiment the air or gas supplies directs the drying air or gas in a downwards angle towards the lower part of the filter elements.

In an alternative embodiment, the drying air or gas is directed towards the filter elements by use of baffles, guide elements or the like (not shown).

Hereby it is possible to provide a circulation of the drying air or gas between the filter elements, thereby optimizing the drying process, for example by reducing drying time.

In an embodiment, the one or more drying air or gas supplies is connected to the filter inlet passing drying air or gas through the filter inlet and through one or more drying air or gas supplies.

Hereby it is possible to provide drying air or gas from a top side of the filter housing and at the same time provide drying air or gas from another place of the filter housing.

In an embodiment an additional drying air or gas inlet and/or an air or gas inlet through a product discharge outlet supplies an additional drying air or gas to the filter system.

In an alternative embodiment, one or more drying air or gas supplies are replaced by an additional drying air or gas supply connected to a bottom of the filter housing.

In an alternative embodiment, one or more drying air or gas supplies are replaced by an additional drying air or gas supply supplied through a product discharge outlet connected to a bottom of the filter housing.

Hereby is achieved alternative solutions of supplying drying air or gas to filter elements in a filter where the size of the filter limits possibilities of placing the drying air or gas supplies to the side of the product chamber.

In an embodiment, the one or more drying air or gas supplies is placed as a combination of one or more placements mentioned in one or more of the above embodiments.

Hereby it is possible to provide different drying air or gas streams, in different directions optimizing drying of the filter elements.

In an embodiment, the one or more drying air or gas supplies is connected to the filter inlet and/or the clean-gas outlet, said one or more drying air or gas supplies being closed by closing means during normal operation and open during drying of the filter elements.

In an alternative embodiment, the one or more drying air or gas supplies is connected to the bottom of the filter housing or to the discharge outlet for removing product.

Hereby it is possible to direct the drying air or gas in a selected direction by opening or closing one or more of the drying air or gas supplies.

In an embodiment the drying air or gas or a part of the drying air or gas is directed to the further drying air or gas supplies and into the filter system.

Hereby it is possible to divide the drying air or gas stream into different directions of drying air or gas streams.

In an embodiment the drying air or gas or a part of the drying air or gas is directed through the filter inlet and into the filter system and out of the filter system through the one or more drying air or gas supplies.

Hereby it is possible to create a flow of drying air or gas passing the filter elements through the filter housing optimizing the drying process.

The objective of the invention is also achieved by a method of drying filter elements in a filter system according to any one or more of the embodiments mentioned above, where drying air or gas is supplied to the filter elements after wet cleaning of the filter elements, and where drying air or gas is passed through the filter inlet and/or through one or more drying air or gas supplies.

Hereby it is possible to provide a more optimized and efficient drying of the filter system including filter elements. This for example leads to a significant reduction in drying time and thereby a significant reduction of down-time of a plant in which the filter system is installed, optimizing the production time of the plant.

In an embodiment of the method, the drying air or gas is passed into the filter system through the filter inlet and directing at least a part of the drying air or gas out of the filter system through the one or more drying air or gas supplies.

Hereby it is possible to create a flow of drying air or gas passing the filter elements through the filter housing optimizing the drying process.

Various embodiments are described hereinafter with reference to the figures. Like reference numerals refer to like elements throughout. Like elements will, thus, not be described in detail with respect to the description of each figure.

It should also be noted that the figures are only intended to facilitate the description of the embodiments.

They are not intended as an exhaustive description of the claimed invention or as a limitation on the scope of the claimed invention. In addition, an illustrated embodiment needs not have all the aspects or advantages shown.

An aspect or an advantage described in conjunction with a particular embodiment is not necessarily limited to that embodiment and can be practiced in any other embodiments even if not so illustrated, or if not so explicitly described.

Throughout, the same reference numerals are used for identical or corresponding parts.

According to the invention, a filter system1comprises a filter housing2with an inlet part3and a clean-gas outlet4. The filter system1further comprises a partition wall5dividing the filter housing2into a product chamber6and a clean-gas chamber7, said partition wall5being provided with a number of openings from which a plurality of filter elements8extends downwards into the product chamber6, which inlet part3is placed in an upper part of the product chamber6and in open communication with the product chamber6, and configured for supplying a product-containing flow of gas to the product chamber6, said gas flow being conveyed through the filter elements8and upwards into the clean-gas chamber7, from where the filtered gas is discharged through the clean-gas outlet4.

The partition wall5is most often an apertured plate or tube sheet, which divides the filter housing into a gas-cleaning chamber or product chamber6and a clean-gas take-off chamber or plenum7. The partition wall5supports a plurality of tubular filter elements8within the product chamber6, so when a product-containing gas is directed through the inlet3into the product chamber6, the gas passes through the filter elements8and leave the filter housing2through the clean-gas chamber7and the clean-gas outlet4. Particulate materials separated from the product-containing gases are deposited on the exterior of each filter element8and are afterwards lead out through a discharge outlet13at the bottom9of the filter housing2, which is well known in the art. To accommodate cleaning of the filter elements8, the filter housing2(or bag house in case bag filters are used) includes a reverse-flow flushing arrangement, pulse cleaning, a filter element shaking system or the like (not shown). Further, when the filter system1is stopped due to wet cleaning, the filter elements8are cleaned with liquid, which liquid is to be dried before the filter system1can enter operational mode again.

The product discharge outlet13is connected to the bottom9of the filter housing2and the outlet13can be provided with a valve17in a valve housing15, which valve17can rotate in the housing15around an axle16in order to open and close the valve17. When the valve17is open, product from the filter housing can be removed and after wet cleaning of the filter elements8, liquid can be removed through the valve. Between the discharge outlet and the filter housing, an air or gas inlet14for drying air or gas can be placed. The valve17in this embodiment is configured as a rotor shown inFIG.1with four wings or vanes, forming four cells within the housing15. Hereby is obtained that the valve or rotor17can be turned for discharging product through the outlet13as a kind of airlock without opening for free passage of air through the lock. In other embodiments, the valve or rotor can be provided with six, eight or ten wings or vanes forming the same number of cells in the rotor17. If drying air or gas is to be injected into the filter system1through the discharge outlet13in this embodiment, the valve or rotor17must be removed first. The valve or rotor17can have any number of wings or vanes, as long as it is able to function as an airlock.

In an embodiment (not shown) two or more valves can be placed in series one above the other in the discharge outlet13. Hereby it is possible to close the lower valve and open the upper valve. Then product powder will enter a space between the two valves. Now the upper valve can be closed and the lower valve opened, and product is thereby discharged from the filter. This sequence can be repeated discharging product from the filter housing without need for pausing the filtering process.

The valves17can be butterfly valves, flap valves or similar valves. When more than one valve17are used, both or all valves are open, when injecting drying air or gas through the valves17in the product discharge opening13.

In an embodiment the drying air or gas inlet14and/or an air or gas inlet through the product discharge outlet13, can be used as an additional drying air or gas supply.

Here an additional drying air or gas inlet14and/or an air or gas inlet through a product discharge outlet13supplies an additional drying air or gas to the filter system1.

In an alternative embodiment, one or more drying air or gas supplies10are replaced by an additional drying air or gas supply14connected to a bottom9of the filter housing2.

In an alternative embodiment, one or more drying air or gas supplies10are replaced by an additional drying air or gas supply supplied through a product discharge outlet13connected to a bottom9of the filter housing2.

In these embodiments the drying air or gas inlet14and/or an air or gas inlet through the product discharge outlet13, can be used as main supply of drying air or gas and even as the only drying air or gas supplies.

Hereby the drying air or gas supply14and/or a drying air or gas supply through the product discharge outlet13replaces the drying air or gas supplies10connected to the filter inlet3or to the filter housing2.

This is illustrated inFIG.1showing also the air or gas supplies10, but these embodiments can also be carried out without the drying air or gas supplies10as well as being added to the rest of the embodiments shown in the rest of the figures.

It is clear that if drying air or gas is supplied through the product discharge outlet13, the valve or valves17must be open.

To be able to minimize the down time for the filter system1after wet cleaning, the filter system1is provided with one or more air or gas supplies10placed in the product chamber6below said inlet part3and configured for leading drying air or gas into or out of the filter system1.

Down time for the filter system1can be explained as the time from stopping the filter system1and until the filter elements8are dried. Only the drying time of the down time can be shortened by this invention.

Drying air or gas should be understood as drying air or drying gas.

In an embodiment, the one or more drying air or gas supplies10is placed in a lower part of the filter housing2and having openings11placed below the filter elements8. Placing the one or more drying air or gas supplies10in a lower part of the filter housing2and the drying air or gas supplies10having openings11placed below the filter elements8ensures a flow of drying air or gas from below and up along sides of the filter elements8, optimizing the drying process.

In an embodiment, the one or more drying air or gas supplies10is placed in a lower part of the filter housing2and having openings11placed at a level corresponding to a lower part of the filter elements8. Hereby is also ensured that drying air or gas is supplied along or along most of a length of the filter elements8.

In an alternative embodiment, the one or more drying air or gas supplies is connected to the bottom9of the filter housing2or to the discharge outlet for removing product.

In an embodiment, the one or more drying air or gas supplies10is placed in an upper part of the filter housing2and having openings11directing drying air or gas towards the lower part of the filter elements8. Hereby the drying air or gas is entered into the filter housing2in a direction different from a perpendicular direction in relation to the filter elements8giving a flow of drying air or gas within the filer being substantially in a lengthwise direction in relation to the filter elements8giving a circulation of drying air or gas from the upper part of the filter housing2in a downwards direction towards the lower part of the filter housing2along the filter elements8.

In an embodiment the air or gas supplies10directs the drying air or gas in a downwards angle towards the lower part of the filter elements8.

In an alternative embodiment, the drying air or gas is directed towards the filter elements8by use of baffles, guide elements or the like (not shown).

In an embodiment the one or more drying air or gas supplies10is connected to the filter inlet3passing drying air or gas through the filter inlet3and through one or more drying air or gas supplies10.

In an embodiment, the drying air or gas can also be supplied through the clean-gas outlet tube4to pass drying air or gas into the filter system1in a reverse direction (not shown) compared to normal operation.

In an alternative embodiment, the drying air or gas supplies10can be connected directly to the clean gas outlet tube4.

These embodiments provides for supply of drying air or gas in a flow from the upper part of the filter elements8and downwards along the filter elements8.

In an embodiment one or more drying air or gas supplies10is placed as a combination of one or more placements mentioned in one or more of the above embodiments, leaving a possibility for supplying and/or extracting or leading out drying air or gas from the filter housing2from different or several connection points.

In an embodiment the one or more drying air or gas supplies10is connected to the filter inlet3and/or the clean-gas outlet4and/or discharge outlet for removing product (not shown), said one or more drying air or gas supplies10being closed by closing means12during normal operation and open during drying of the filter elements8. Here it is possible to make use of existing piping in the filter system1the supply or extract drying air or gas from the filter housing2. The closing means12can be butterfly valves, flap valves or similar closing means12.

In an embodiment, the drying air or gas is passed into the filter system1through the clean-gas chamber7and out of the filter system1through the one or more drying air or gas supplies10. Hereby a reverse flow in the filter system is obtained as an option of supply of drying air or gas. This is a situation as opposed to normal operation of the filter system. Hereby the filter elements8are dried by blowing drying air or gas from inside the filter elements8.

In an alternative embodiment, drying air or gas can provided through the filter inlet3using the drying air or gas supplies10as outlets for the drying air or gas.

To dry the filter elements8of a filter system1method is provided, where drying air or gas is supplied to the filter elements8after wet cleaning of the filter elements8, by passing drying air or gas through the filter inlet3and/or through one or more drying air or gas supplies10.

In an embodiment of the method, drying air or gas is passed into the filter1through the filter inlet3and at least a part of the drying air or gas is directed out of the filter1through the one or more drying air or gas supplies10.

The person skilled in the art realizes that the present disclosure is not limited to the preferred embodiments described above. The person skilled in the art further realizes that modifications and variations are possible within the scope of the appended claims. Additionally, variations to the disclosed embodiments can be understood and effected by the skilled person in practicing the claimed disclosure, from a study of the drawings, the disclosure, and the appended claims.