US1977101A - Treatment of gas - Google Patents

Description

Patented Oct 16, 1934 UNITED STATES TREATMENT OF GAB .Waclaw von Piotrowski and Josef Winkler, Drohobycz, Poland No Drawing. Application August 30, 1933, Serial No. 687,514. In Poland November 12, 1932 9 Claims.

This invention relates to the treatment of town gas as is used for illuminating and other purposes. More particularly the invention relates to an improved method of preventing the deposition of solids in gas mains, meters, etc., whereby the expense heretofore involved in maintaining a gas-supply system fully operative-at all times,

is materially reduced.

It is well known that one of the disadvantages l0 occurring most frequently in cold weather is the deposition of solids in gas mains whereby they become clogged. Coal gas contains naphthalene vapors which have a high vapor tension, and when the temperature of the gas falls below the dew-point for naphthalene, solid naphthalene is deposited generally at diflicultly accessible or narrow passages in the gas mains.

Numerous attempts have been made to remedy this situation as by washing the gas with oils which dissolve naphthalene quite readily. This method is not satisfactory because it does not remove all of the traces of naphthalene which may be deposited. More recently naphthalene solvents, such as tetralin, have been injected into the gas, and upon cooling of the gases the solvent is deposited in liquid form and containing the naphthalene dissolved therein. This liquid condensate is drawn off by siphons without interrupting the operation of the system.

A. solvent which .is suitable for this purpose must have a high solvent power for naphthalene even at low temperatures. The vapor tension of the solvent must be great enough for it to be suilicient for complete solution of the naphtha- 36 lene, but it must not be too great as otherwise the cold gas will contain too large an amount of solvent dissolved in vaporous state, with the result that a larger quantity of solvent is necessary. The solvent must be insoluble in water 40 and have no corrosive action on the gas mains,

meters, etc. It must be also completely combustible and its combustion products must neither be disagreeable nor detrimental. Finally the solvent should be as cheap as possible.

As stated above, it has been proposed to employ tetralin (tetra-hydronaphthalene). It has also been proposed to employ xylol and its homologues, but these are even more expensive than tetralin.

It is an object of the present invention to provide an improved method of preventing deposition of solids in gas mains, particularly to prevent the deposition oi naphthalene, and to pro- .vide a more economical method than has hitherto been possible.

It has now been observed that the oxidation or dehydrogenation products obtained by oxidation of mineral oils form very cheap and highly efiicient solvents for the naphthalene contained in coal gas. The composition of these solvents varies in accordance with the extent of the oxidation, the nature of the raw material and other factors. The synthesis of these products forms no part of the present invention. It is sufiicient to observe that these solvents maybe readily and cheaply secured in known manner by the oxidation of hydrocarbon fractions either under pressure in the liquid phase, as is shown in the Penniman British Patents Nos. 255,020 and 256,922, and in the Burwell U. S. Patents Nos. 1,690,769 and. 1,770,875, or by oxidation in the vapor phase with or without the use of catalysts as has been described by Ellis 8; James.

The raw materialsused in these processes may be petroleum fractions, crude petroleum or petroleum residues, shale oils, tars and asphalts, wood distillation oils, 'etc. These oxidized dehydrogenated products have found use in various arts as, for example, in denaturing alcohol. Similarly other oxygenated hydrocarbons obtained from acetone oils, furfurohturpentine, and the compounds resulting in the catalytic conversion of water gas may also be used.

All of these products comprise high boiling point mixtures consisting of aromatic compounds, unsaturated compounds and high-molecular neutral oxygenated compounds. The proportions of each of these three broad classes of constituents may vary considerably, but in most cases very cheap and highly eilicient solventsfor the naphthalene contained in coal gas are secured. Compared, for instance, with the priceof tetralin, these mixtures may be obtained at one-fifth of the expense.

It should be observed that mineral oil hydrocarbons per se are not suitable for dissolving the naphthalene, while furthermore the solvents employed in accordance with the present invention have a far greater solvent capacity for the naphthalene than is possessed by a corresponding amount of tetralin.

In practicing the invention the non-corrosive combustible solvent which preferably hasa boiling point of between 150 and 250 C., and which may contain high molecular neutral oxygenated organic compounds, is injected into the gas, and upon cooling of the gas it is deposited and ex tracts from the gas all of the naphthalene which would be deposited in solid form in the gas mains. The solvent in liquid form is removable from 110 the gas mains by siphons without interfering with the operation of the gas supply system. As is indicated, the oils obtainable by oxidation of petroleum, are very suitable for the purposes of this 5 invention, and it will be appreciated that so long as all of the naphthalene which would separate,

below the dew-point therefor is 'efliciently removed, it is not necessary for attempts to be made to remove any remaining naphthalene which may still exist in the gas in vapor state and which will not be deposited at the lowest temperature to which the gas may be subjected. In the winter time the temperature in gas mains may be as low as C. or lower. So long as there is present in the gas mixture in vapor form a sufficient :Iecting oxygenated non-corrosive hydrocarbon oils into the gas and then vaporizing and condensing said oils.

5. The method of removing that portion of naphthalene contained in coal gas which is deposited at temperatures below the dew point for the naphthalene, which comprises the dissolution of the excess naphthalene in an oxygenated non-corrosive oil mixture having a vapor tension sufliciently great to retain the naphthalene in solution upon condensation, but low enough to avoid excess vaporization of said oil mixture in the gas stream, and subsequently separating out the oil.

6. The method of preventing clogging of gas mains in use which comprises injecting into the gas stream a non-corrosive combustible solvent for naphthalene, having a boiling point of between about 150 and 250 C. and containing dehydrogenated non-corrosive hydrocarbon .oils possessing high solvent power for naphthalene and relatively low vapor tension, and thereafter with- B011!!! Solvent 11mm:

Va r pressure in mxn. Hg.

For a gas which contains 130 m naphthalene per in at Solution of the naphthalone wt. percent 20 following are necessary At 2? O. 2? 10" 0 C.

INS-210 a 17 mm. 105

1300 g. per 1000 m The amounts secreted are not sufllcient (or dissolving the naphthalenesecreted.

0. H) mm. 750 g. per 1000 m As may be seen from the above table, the oxidized hydrocarbon oils have a far higher solvent capacity than has tetralin, and hence less quantitles of it are required in the eilicient operation of the process.

It will be appreciated that numerous variations will readily suggest themselves to those skilled in the art without departing from the spirit and scope of this invention as set forth in the appended claims.

We claim:

1. The method of preventing deposition of naphthalene in gas mains which comprises incorporting in the gas a non-corrosive liquid combustible solvent for naphthalene boiling between 150 and 250 C. and containing high-molecular neutral oxygenated organic compounds and thereafter removing said solvent.

2. The method of preventing deposition of naphthalene in gas mains which comprises in- .jecting non-corrosive oils obtainable by oxidation of crude petroleum oils into the gas, and thereafter removing said oils.

The method of preventing deposition of naphthalene in gas mains which comprises injecting into the gas, oxygenated non-corrosive hydrocarbon oils, and then separating the gas and oils.

4. The method of preventing deposition of naphthalene in gas mains, which comprises indrawing the solvent containing the dissolved naphthalene from the gas stream.

7. The method of preventing deposition of solids in gas mains which comprises introducing a substantially non-corrosive but combustible mixture of aromatic, saturated and unsaturated and highmolecular oxygenated organic compounds, having a boiling point of between 150 and 250 0., into contact with the gas, cooling the gas to condense the mixture and withdrawing the mixture from the gas stream.

8. The method of preventing naphthalene deposition in gas mains which comprises mingling the gas with a volatile non-corrosive solvent for naphthalene, and thereafter cooling the gaseous mixture to condense said solvent and removing it from the gas stream, said solvent containing such liquid fractions as are obtainable by the dehydrogenation of crude petroleum, petroleum distil- 13 lates, shale oils, petroleum residues, tars, and asphalts.

9. The method of preventing deposition of naphthalene-containing solids in gas v mains which comprises removing excess naphthalene from the gas by subjecting the gas while still hot to the solvent action of oxidized non-corrosive mineral oil, cooling the gas to condense said oil,

- and withdrawing the condensed oil from the gas.

JOSEF WINKLER.

WACLAW Von mo'mowsm.