US1946721A - Process of obtaining valuable light oils from the distillation of coal - Google Patents

Description

Feb. 13; 1934. Q sTlLL PROCESS OF OBTAINING VALUABLE LIGHT OILS FROM THE DISTILLATION 0F COAL File d Aug. 26, 1931 Patented Feb. 13, 1934 PROCESS OF OBTAINING VALUABLE LIGHT OILS FROM THE DISTILLATION OF COAL Carl Still, Reckiinghausen, Germany Application August 26,

1931, Serial No. 559,573,

and in Germany August 29, 1930 7 Claims.

The subject of this invention is a process for obtaining valuable light oils from the distillatlon of fuel in chamber or retort ovens. In carrying out the process, ovens for the distillation of coal provided with external heating, that is,

chamber or retort ovens for the production of gas and coal, can be used.

According to the invention, the products from which the valuable light oils are to be obtained are themselves obtained by forming channels or ducts in the mass of coal, for example by ramming, boring or embedding forming bodies such as rods or tubes, which may be entirely or partially withdrawn. The distillation products evolved in the interior of the mass of coal are drawn on through these ducts, collected in a pipe common to all the ducts and then led in the usual manner into one or more gas and tar mains. The distillation products are, preferably,

, drawn off from the said ducts by tubes connect- All ed gas-tight to the discharge ends of the ducts or by perforated tubes inserted in the ducts, the tubes being carried through the oven walls, for example in the case of vertically arranged ducts, through the oven roof or still within the oven, and open into a common collecting pipe leading from the oven chamber.

It is important, in this case, that the suction apparatus should be provided with pressure regulating devices which enable the suction pressure in the ducts to be controlled as required, and, if required, to be modified during the course of and according to the phase of the distillation process. For the particular purpose of the application, namely the production of valuable light oils of new composition, the suction pressure used in the ducts is preferably maintained at least at mm. of the water gauge below atmospheric.

For particular classes of coal, and also in the later stages of the distillation process, much higher suction pressures may be employed. For instance, in the distillation and coking of Westphalian coals, suction pressures up to 200 mm. W. G. below atmospheric and even more have been found advisable. The pressure regulation is, preferably, effected by means of resistances, such as throttling devices or liquid seal resistances, inserted between the suction ducts and the gas and tar main.

The distillation products which are obtained in this manner are then treated at first in the usual manner. The light oils, the recovery and treatment of which form the main object of this invention, are contained partly in the tar condensed by cooling the distillation gas and partly remain as vapours in the cooled gas itself and can be removed from it, for example, by an oil wash.

As an example, one embodiment of a plant for w carrying out the process according to the invention is shown diagrammatically in the accompanying drawing.

An oven for the distillation of coal, for example a horizontal chamber oven, suitable for carry- 6 ing out the process, is shown at l. Ducts 3 are formed in the loosely shaken or embedded mass of coal 2 by forming bodies rammed or bored in the coal, and from these ducts the distillation products evolved in the interior of the coal are drawn off by suction by means of inserted tubular members 4. The tubular members 4 are inserted in discharge tubes 6 and are, preferably, provided with packing 5 to seal the members 4 against the interior of the discharge tubes 6. The tubes 6, in the case of vertically arranged ducts are, preferably, led through the oven roof and are connected to a collecting pipe 7 disposed over or outside the brickwork of the roof. The individual collecting pipes of the chambers lead into a gas and tar main 8, the connection of each individual pipe 7 to the gas and tar main 8 including, besides the usual closing valve, a controlling member 9 formed, for example, as a throttling cap. The controlling members 9 enable the suction pressure in the ducts 3 to be regulated as required for the particular coal being employed or as called for by the particular phase of the distillation process.

While only one discharge tube 6, member 4 .90 and duct 3 is shown in the drawing, it is to be understood that the description given thereof applies equally to a plurality of such organizations which may be, and in the most practical form are, provided at spaced intervals over the v 5 whole area of the oven roof.

The distillation products obtained pass through a pipe 10 into one or more gas coolers 11 and thence, by a pipe 12 into a tar extractor 13. The apparatus 14 represents an ammonia washer of any suitable kind and 15 a benzol washer operating with washing oil, which in known manner are arranged and designed to be traversed in succession by the distillation products. The gas is led away from the benzol washer 15 through a .105 pipe 16, while the saturated wash oil passes through a pipe 1'7 into an oil heater 18 from which it is led through a pipe 19 into a stripping still 20. The stripping still allows the washing oil freed from light oil to be discharged at 410 the bottom, while the light oil passes from the top of the stripping still into a cooler 21 and after condensation therein into a pipe 22. From this point the further treatment of the light oil product is effected through a rectifying column 23 which separates out the remainder of the washing oil, while the crude light oil passes through a pipe 24 into a cooler 26 and from there into a pipe 27. The pipe 27 leads the crude oil into an apparatus 28 in which the first, or acid wash treatment is carried out. The first acid wash is succeeded according to the invention by a second wash, which is carried out with highly concentrated sulphuric acid. The same apparatus 28 can serve for the second wash, but it is preferable to insert a second washer 29. The crude light oil, after being passed through both washers 28 and 29 is subjected to an alkali and water wash in a washing apparatus 30 and then is passed into a further rectifying column 31. From this, the residues are collected at 32, while the light oil, which is now pure, is led again into a cooler 33 and is then stored.

Crude tar is separated out in the cooling of the distillation products by the gas cooler 11 and this tar also contains light oils. In order to extract these light oils from the tar, the crude tar in the cooler 11 is led by a pipe 43 to an indirectly heated stripping still 34, where the crude light oil is separated from the tar. The tar forming the residue is, pref rably, led away at 35, while the crude light oil passes into a cooler 36 and from there into a pipe 37. By an extension 38 of the pipe 37 the crude light oil may be led directly into the washer 28, but it is preferable to lead the crude light oil by a pipe 39 into the pipe 22 at the junction l0, so that the crude light oil obtained from the crude tar is also rectified in the column 23. For the purpose of leading the light oil either through the pipe 38 or through the pipe 39 it is necessary to close or open the valve 41 or 42.

These light oils obtained in the described distillation process have a special composition and chemical properties. They do not consist exclusively of aromatic hydrocarbons, i. e. benzol and its higher homologues, as in the fomer proc esses for the distillation of coal conducted at higher temperature and without the use of the interior suction ducts. They consist essentially in a mixture of aromatic and aliphatic hydrocarbons with a greater or less proportion of the latter.

To finally convert this light oil of new composition into a valuable product, especially adapted as the working medium for motors, it has been found necessary to carry out the further treatment, in particular the final purification of this distillation product, in a new manner. If the crude light oil is treated in the ordinary manner with highly concentrated sulphuric acid there are considerable losses in the purification of from about 20-25 per cent. of the original quantity. By the use of less concentrated sulphuric acid, these losses can certainly be diminished, but the degree of purity required for the usual commercial purposes is not obtained. Also, the light oils purified in this way are not resistant to light and air, but after some time are discolored.

On the other hand, the applicant has found that all the requirements as regards the purity of the light oil and its resistance to light and air are complied with, if the purifying treatment is conducted in two stages; in the first stage the light oil being treated with a polymerizing mebent. HzSOrat ordinary temperature. The tomdium of restricted activity, such as, for example, moderately concentrated or dilute sulphuric acid or haloid salts or with adsorption media, such as silica gels, activated coal, infusorial earths, or with mixtures of such materials, while in the second stage a treatment is effected with concentrated acid or other similarly strongly active medium.

Practically, this treatment can be carried out, if, for example, sulphuric acid of at the most per cent. H2804 is employed at ordinary or only slightly higher temperatures, and then sulphuric acid of at least 90 per cent. H2SO4 at a higher temperature, preferably between the limits of about 30-35 C. This can be followed by the usual treatment with alkali lye and washing with water and distillation.

The action of the proposed combined treatment and its results, as compared with the usual single treatment with highly concentrated acid, can be explained by the fact that certain proportions of the crude light oil, when directly attacked by highly concentrated acids, are changed into valueless waste material, for example by addition and formation of sulphur compounds soll.

uble in water. On the other hand, these constituents in the combined treatment in the first stage, for example with moderately concentrated sulphuric acid, are polymerized to lower molecular oils, that is stabilized and brought into a l form in which they are resistant to the succeeding attack of the highly concentrated sulphuric acid and remain as valuable constituents of the light oil.

An essential advantage of the new process is 1 that a larger quantity of the distillation products, drawn by suction from the charge of coal, is obtained as improved light oils, and not again lost wholly or partly as Worthless waste materials in the later stages of the purifying processes. In 1 the process according to the invention, therefore, a very essential diminution of the losses due to purification is obtained and at the same time the yield in light oil is considerably increased.

As a polymerizing medium for the treatment in the first stage, moderately concentrated or dilute sulphuric acid can, as explained, be employed, or haloid salts, for example ferric chloride, zinc chloride, aluminium chloride, chloride, of lime; also materials such as ferric sulphate, sodium methylate, sodium ethylate, boric acid, phosphoric acid; also solid adsorption materials such as silica gels, activated coals, infusorial earths, fullers earth, or mixtures of several such materials.

The first described treatment can be varied in many ways, for example, by the first treatment with sulphuric acid being effected by means of a considerably lower content in H2504 than 80 per cent. and in order to obtain a similar polymerizing action, as with, for example, 80 per cent. acid, the temperature must be correspondingly raised. In the succeeding second treatment with sulphuric acid of higher concentration the said temperature must, however, be

maintained between 30 and 35 C.

Examples perature rise amounts at the most to 2 or 3 C. After the sediment has been withdrawn, the remaining light oil is treated with 50 grams sulphuric acid of 91 per cent. H2804. The acid is imparted slowly and the temperature is maintained at 32 C. by watching or by special external cooling. After the waste acid settling at the bottom has been discharged, the washed light oil is subjected to the usual treatment with soda lye and water and, finally, is distilled so as to obtain a pure product. In this way 920 grams of pure distillate are obtained from sulphuric acid, Type 1, the total loss of the purification, including the distillation, amounting to grams, viz. 8 per cent. of the original quantity.

(2) The same quantity of 1000 grams of the same light oil as in Example 1 is washed with regenerated sulphuric acid from the benzol purification of about 44 B=54 per cent. H2804, While the temperature is maintained at 55 C., which is obtained by a preliminary heating of the light oil. The light oil remaining after the discharge of the sediment at the bottom is first cooled to about 30 C. and then undergoes the whole further treatment as described in Example 1. In that way 898 grams of pure distillate are obtained from sulphuric acid, Type 2, as the final product, so that the total losses amount to 10.2 per cent.

(3) 1000 grams are again taken of the light oil as before and treated at ordinary temperature with 5 grams of aluminium chloride free from water and stirred, whereby a rise of temperature of about 3 C. occurs. The further treatment is similar to that described in Example 1. 905 grams pure distillate are obtained from the sulphuric acid, Type 1, as the final product, so that the total losses amount to 9.5 per cent.

What I claim is:--

1. The process of obtaining valuable light oils from the distillation of coal which consists in forming ducts in the interior of a coal charge, withdrawing the products of distillation by suction from said ducts, separating the light oils from the other distillation products, stabilizing the separated light oils with a polymerizing agent of moderate activity, and then washing with a polymerizing agent of greater activity.

2. A process according to claim 1, in which the first treatment is effected at ordinary temperature and the after treatment at between 30 and 35 C.

3. A process according to claim 1, in which the light oil is first washed with sulphuric acid of approximately 80 per cent. concentration at ordinary temperature, and is then washed with sulphuric acid of approximately 90 per cent. concentration at a temperature between 30 and 35 C.

4. A process according to claim 1, in which the light oil is first washed with sulphuric acid of approximately 54 per cent. concentration at a temperature of approximately 55 C. and is then washed with sulphuric acid of approximately 90 per cent. concentration at a temperature between 30 and 35 C.

5. A process according to claim 1, in which the suction pressure used is of the order of 40 mm. of the water gauge below atmospheric.

6. The process of obtaining valuable light oils, containing a considerable portion of aliphatic hydrocarbons, from the distillation of coal in chamber or retort ovens which consists in forming ducts in the interior of a coal charge, withdrawing the products of distillation by suction from said ducts, separating the light oils from the other distillation products, stabilizing the separatedflight oils with a polymerizing agent of moderate activity, and then washing with a polymerizing agent of greater activity.

7. Process for obtaining a higher yield of light oils from the distillation of coal in coke or retort ovens consisting in that the distillation gases are drawn off by suction below atmospheric pressure from ducts provided in the interior of the coal charge and the light oils after being separated from the other distillation products are first treated with sulphuric acid of low or moderate concentration, and then with sulphuric acid of at least 90 per cent. concentration.

CARL STILL.

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