US3452490A - Cleaning surface deposits from raschig rings - Google Patents

Description

United States Patent Office 3,452,490 Patented July 1, 1969 Int. Cl. B24]: 1/00 US. Cl. 51-314 7 Claims ABSTRACT OF THE DISCLOSURE Surface deposits are cleaned from Raschig rings by tumbling same with an abrasive such as sand. The Raschig ring and sand mix can be tumbled dry or wetted with a cleaning solution. The method is especially suitable for cleaning dirty or fouled Raschig rings constructed of aluminum. The tumbling is advantageously carried out at elevated temperatures on the order of about 100 to 200 F.

This invention relates to cleaning surface deposits from Raschig rings used in processing equipment, and more particularly relates to an improved method of cleaning carbonaceous and/or polymeric deposits from dirty or fouled Raschig rings used as packing in commercial distillation or extraction columns, so that they may be reused by tumbling the Raschig rings together with an abrasive such as sand.

Raschig rings are well-known packing materials used for a plethora of varying processes. In distillation towers and many other process vessels or other equipment related to varying process steps, the conditions prevailing in the vessel operate on the materials being processed to cause surface deposits of widely differing natures and as a result of a virtual plethora of phenomena to form on the inner and outer surfaces of the Raschig rings. When such deposits form, it becomes necessary from time to time either to remove these deposits or to replace the coated Raschig rings with a fresh charge of clean Raschig rings. In cases where the rings are cleaned, those deposits which are diflicult to remove, which is the usual case, require severe methods to clean the rings, especially the inner annular surfaces thereof. The simplest, most effective, convenient, least time consuming methods of cleaning the rings all over, including the inner surfaces, heretofore has been by one or the other of two fairly competitive methods: (1) by treating the rings with highly corrosive or caustic cleaning solutions or (2) by burning the deposits off. These techniques, however, frequently damage the rings due to the severity of the treatment. The damage problem is greatly accentuated when the rings are constructed of materials such as aluminum which is attacked by the highly caustic solutions and weakened structurally by the heats of the burning techniques.

It is, accordingly, highly desirous to find a technique of cleaning Raschig rings which minimizes damage to the ring surfaces and structure generally.

A special object is to provide a method suitable for cleaning Raschig rings constructed of materials such as aluminum.

Other objects are to provide a technique broadly applicable to Raschig rings constructed of different materials, which will reduce the costs and the time involved in removing surface deposits.

Still another object is to provide a broad method generally applicable to the removal of various and different kinds of surface deposits from all surfaces of Raschig rings, including the inaccessible inner surfaces.

Other objects will become apparent from viewing this disclosure in its entirety.

To the accomplishment of the foregoing and related ends, the present invention comprises in brief and broadest respect, admixing the Raschig rings with sand or other abrasive and subjecting the mix to tumbling action. In more narrow but still broad respect the invention comprises the alteration of additional treatments of the mix of (1) applying heat sufiicient to obtain temperatures in the range of about F. to 200 F. whereby it is tumbled dry and free of lumps; or adding a cleaning solution thereto such as an aqueous caustic solution and tumbling same in a very wet state.

We have found that the sand and Raschig ring mix should either be dry with regard to both Water and organic matter, or else very wet with a cleaning solution.

Usually at least about 0.1 volume of sand per volume of Raschig rings are used. On the other hand, not more than about 0.4 volume of sand per volume of Raschig rings are employed because of reduced efliciency in terms of the amount of rings cleaned per volume of tumbler, and ultimately in the time required to clean large volumes of rings, etc., although such would undoubtedly work. Preferably about 0.2 to 0.3 volume of sand per volume of Raschig rings is employed.

One cautionary comment is in order in connection with the tumbling operation. Although the present invention is applicable to clean Raschig rings of all materials of construction, the tumbling action is to be conducted with care in the case of ceramic and such materials unable to take considerable shock unlike those constructed of steel and aluminum. A padded tumbler can be used as a means to reduce the shock during tumbling. 'Ihe tumbling action is conveniently and effectively achieved by using known and existing equipment such as a concrete mixer, although other equipment capable of a regulated tumbling already known can be used or easily devised.

The heat is conveniently applied in the dry technique, where that technique is used, by inserting a large blowtorch of the kerosene fueled type into the opening of the mixer, although other heating means can also be used. During the tumbling, temperatures of the sand and Raschig mix as high as about 200 F. may be desired, but typically the mix is heated to about 100 to 150 F., and preferably it is heated to about to F.

When a cleaning solution is used, it should be one that dissolves the deposit or otherwise actively aids the loosening or removal of this deposit as by reaction therewith or operating thereon. It can be an aqueous solution of a wetting agent, a detergent, an alkaline material, or an acid depending on the particular deposit. It should not be too corrosive on the tumbler or Raschig rings and preferably is completely compatible with the mateirals of construction in the mixer or Raschig rings. Generally a suitable cleaning agent will already be known for the particular deposit but if not a suitable one can be determined by routine experimentation. Generally the concentration is selected to minimize corrosion of the equipment and the Raschig rings, if it is corrosive at all on either, subject to the limitation that a concentration ufiicient to be effective as a cleaning aid is always to be employed. Examples of materials that may be used as cleaning solutions alone and some in combination are sodium hydroxide, potassium hydroxide, sulfuric acid, nitric acid, trichloroethylene, methanol, dimethyl sulfoxide, citric acid, sulfamic acid, sodium naphthenate, sodium sulfonates and sodium carbonate, etc. Certain of the foregoing are known to present some hazard in regard to toxicity and/or flammability, but this can be easily obviated by proper precautions readily apparent to those skilled in the art. The reason why cleaning solutions can be used here is that the use of sand shortens the cleaning operation sufficiently that the Raschig rings are not harmed by corrosive cleaning solutions nearly so much as in conventional techniques using the same cleaning solutions. Batches of Raschig rings have been cleaned in about ten minutes using sand wetted with cleaning solution. The rings are not significantly damaged by the dilute caustic cleaning solutions at such short contact times.

The amount of cleaning solution to be used is not critical but enough is used to completely wet the abrasive and Raschig ring mix. Typically about 0.1 to 0.2 volumes of cleaning solution per volume of Raschig rings is used.

To facilitate the understanding of the invention, certain details and illustrative embodiments will now be set forth; however, of course, it is to be fully understood and appreciated that the invention is not limited to the specific conditions or details set forth in these examples, since the process is capable of many modifications and variations and conditions, such modifications and variations being aided, suggested, or indicated by the discussion of the EXAMPLE 1 Dry cleaning About 30 ft. of Raschig rings were placed in a charge hopper. 400 pounds of No. 2 sandblasting sand were added and the mix charged to a conventional /2 yard concrete mixer and tumbled for 20-30 minutes. During the tumbling a large kerosene fueled blow-torch (about 3" nozzle) was placed in the charge opening to provide heat for drying. After tumbling for a time within the foregoing range but sufficient to remove most of the deposit, the mixer contents were dumped onto about a A" to /2" mesh wire screen and water washed with a hose to remove loose sand and deposit.

EXAMPLE 2 Wet cleaning About 30 ft. of Raschig rings were placed in a charge hopper. 100 pounds of No. 2 sandblasting sand, 30 gallons of hot water (about 180 F.) and 1 pound of Oakite 77 (a designation of Oakite Products Inc. for an alkaline cleaning material it markets) were added. The mix was then charged to a concrete mixer (described above) and ,was tumbledfor about minutes..The contents of the mixer was then dumped onto a coarse screen and water washed similar to Example 1 to remove the loose sand and deposit and residual cleaning chemical.

We claim:

1. A method of cleaning deposits from fouled Raschig rings constructed of aluminum wherein said deposits have been formed on said Raschig rings by their use as'a packing in a distillation or solvent extraction column which comprises admixing said fouled Raschig rings with sand to form a mixture and subjecting said mixture to a tumbling action.

2. A method according to claim 1 wherein said mixture is tumbled at a temperature in the range of about lOO to 200 F. 3. A method according to claim 1 wherein about 0.1

to 0.4 volumes of sand per volume of Raschig rings is used.

. 4. A method according to claim 1 wherein a cleaning solution is added to said sand and Raschig ring mixture and the so formed wet mixture is tumbled in the wet state.

5. A method according to cleaim 4 wherein said mixture is tumbled at a temperature in the range of about to 200 F. r

6. A method according to claim 5 wherein the cleaning solution comprises a mixture of sodium hydroxide and sodium carbonate.

- 7. A method according to claim 6 wherein about 0.1 to 0.4 volumes of sand per volume of Raschig rings and about 0.1 to 0.2 volume of said cleaning solution per volume of rings is employed.

References Cited UNITED STATES PATENTS 'LESTER M. SWINGLE, Primar Examiner.

US. Cl. X.R. 134-7, 25, 33