FR2464985A1 - Oil prodn. by liquefaction of coal - by agitation with aq. alkali - Google Patents

Abstract

Liquefaction of coal is carried out by slurrying finely divided coal in an aq. soln. of at least one alkali(ne earth) metal hydroxide, maintaining the slurry in a turbulent state for several (pref. 24) hrs., and sepg. the oil phase from the aq. phase. The coal pref. has a particle size of 0.05-0.2 (esp. 0.07-0.15)mm. The aq. soln. is pref. a NaOH or KOH soln. or a residual liquor from the electrolytic prodn. of NaOH. The pH of the soln. is pref. 10 or more. Turbulence is pref. induced by agitation. The process is simpler and cheaper to operate than prior art processes and gives an oil prod. contg. a large proportion of material boiling in the 150-244 deg.C range, suitable for use as fuel.

Description

 The invention relates to a process for liquefying coal which can be carried out economically by using neither high pressure nor a rise in temperature and without using a hydrogenation reaction.

 To obtain the liquefaction of coal, the processes of dry distillation and solvent extraction have hitherto been known. These known methods have, however, substantial drawbacks, such as the need for a large consumption of energy in order to obtain a relatively small energy source, requiring the use of an expensive solvent and preventing the practical application of these methods on an industrial scale.

The applicant has previously proposed a coal liquefaction process in which an aqueous sodium hydroxide solution is impregnated with a crushed and granulated coal by immersing the granulated coal in said solution, by pulverizing the coal thus treated, after having extracted and dried, in a spraying device to obtain a powder having a particle size less than 0.15 mm (100 mesh) and by adding the powder thus prepared to an aqueous solution containing sodium hydroxide and l carboxylic acid to mix them with stirring, leaving the mixture to stand until the liquefaction of the charcoal begins and, after additional addition of water, heating the mixture to a temperature of 90 to 120 C. (request for Japanese patent published Sho 5415 564),
The aim of the present invention is to improve said process by making it more economical as will be explained below,
This object is achieved, according to the invention, by the fact that the carbon is dispersed in the pulverized state by suspending it in an aqueous solution of at least one alkali or alkaline earth metal hydroxide, while maintaining said carbon. sprayed in a turbulent state in said solution for several hours, preferably approximately 24 hours, and the oily phase obtained is separated from the aqueous phase.

 The process according to the invention offers a new solution to the problem of coal liquefaction, which is simpler to put into practice and more advantageous from the economic point of view than the process described in the aforementioned Japanese patent application, does not require any increase. pressure or temperature rise and allows its practical application on a large scale.

For the implementation of the present invention, all types of coal can be used, for example steam coals, bituminous coals, fatty coals and lignites and by offering the possibility of using insufficiently wetted carboniferous materials, such as than peat. Coal is used in the pulverized state, preferably at a particular average size of 0.05 to 0.2 mm (70 to 300 mesh), and more particularly about 0.07 to 0.15 mm (100 to 200 mesh), as can be obtained by conventional grinding means.

Among the aqueous solutions of hydroxide compounds which can be used in accordance with the invention, there may be mentioned, for example, solutions of alkali metal hydroxide such as lithium hydroxide sodium hydroxide and hydroxide potassium, or an aqueous liquor containing NaOH, and resulting from the manufacture by electrolysis of sodium hydroxide, or aqueous solutions of alkaline earth metal hydroxide, such as magnesium hydroxide and sodium hydroxide , as well as aqueous solutions containing two or more hydroxides in combination, Among these, it is possible to retain aqueous solutions of sodium hydroxide, and potassium hydroxide, as well as the residual liquors containing NaOH resulting of the electrolytic manufacture of sodium hydroxide.

 The pH of the aqueous mixture of pulverized coal and the aqueous hydroxide solution should preferably be equal to 10 or more, and more particularly from 11 to 13.5. It may be sufficient to use a quantitative proportion of the aqueous hydroxide solution relative to the pulverized carbon as it pulverized coal disperses in the solution in the most favorable way. It is preferable, however, that the quantitative ratio of the aqueous hydroxide solution relative to the pulverized coal is at least 1.5 times and more particularly 2 times greater.

 To obtain the turbulence conditions to which the pulverized coal must be subjected according to the present invention, all the known means of maintaining dispersed conditions of the pulverized coal in the suspension of aqueous hydroxide solution can be used effectively, but more particularly it will be preferred agitation and forced circulation. It is also possible to use means implementing ultrasound in addition to these turbulence means.

 The duration of the maintenance of the dispersed suspension conditions according to the present invention is, by definition, the time necessary to obtain the appearance of an oily component forming a layer which floats, a time of 15 to 26 hours which can generally be sufficient to this effect.

An increase in the amount of oily components is not observed if a superplementary agitation is carried out after constitution of the supernatant bed of oily component. Agitation is stopped after the oily component has risen to the surface. After a short instant of rest, the mixture separates into three layers consisting respectively of the oily layer, an aqueous layer and a solid layer almost entirely composed of powdered non-liquefied carbon. The oily layer consists mainly of oil,
A large amount of oil is also dispersed in the aqueous layer. The coal liquefaction oil is obtained both from the oily layer and from the aqueous layer by a usual process such as distillation.

The solid layer can be reused as it is as a raw material for liquefaction,
50% or more of the quantity of coal liquefaction oil obtained according to the present invention distills in a temperature zone of 155 ° C. to 2440 ° C. The fraction thus obtained can be used as it is as fuel. It is also possible to subject the liquefaction oil to fractionation or rectification so as to use each fraction for the most appropriate use in the petrochemical industry.

 The process according to the present invention can also be used with a view to increasing the yield of the most highly volatile fraction from a crude oil.

 Other characteristics and advantages of the invention will emerge from the examples will be given below, solely by way of example, non-limiting embodiments of the invention.

Example 1
300 g. of pulverized bituminous coal, from the Taiheiyo coal mine, with a particle size of 0.15 mm (100 mesh), are placed in a container with a capacity of 3 1, then 650 g of aqueous solution of
NaOH at a concentration of 0.85%. The starting pH of this aqueous mixture is approximately 13.2. This aqueous mixture is stirred at 500 to 600 rpm by means of an agitator having blades 6 cm long.

During a stirring period of 24 hours, an odor resembling that of petroleum emanating from the mixture appears, while an oily layer is simultaneously formed. Since oil is also in the form of a dispersion in the aqueous layer below the supernatant oily layer and formed after the cessation of agitation, not only the oily layer is subjected to a distillation treatment. also simultaneously the aqueous layer. After distillation, 62 g of an oily fraction having a boiling point of 150 to 244 ° C. and 51 g of another oily fraction having a higher boiling point are obtained.

Example 2
The procedure was as in Example 1, except that instead of using an aqueous solution at 0.85% NaOHr an aqueous solution of NaOH was used with a concentration of 0.65% prepared by adding water to a residual liquor containing NaOH at a concentration of 45% and resulting from the electrolytic manufacture of NaOH, the starting pH value being approximately 12.8.

64 g of an oily fraction having boiling points ranging from 150 to 240 ° C. and 45 g of another oily fraction having higher boiling points were then obtained.

Example 3
The procedure was as in Example 1, except that 650 μl of an aqueous KOH solution having a concentration of 0.84% was used and that the starting pH of the aqueous mixture was approximately 12.8.

 In this case, 58 g of an oily fraction having a boiling zone of 150 to 244 ° C. and 49 g of another oily fraction having higher boiling points were obtained.

Example 4
To the 200 g of the residual solid layer of Example 1 was added 450 g. of an aqueous solution of
NaOH having a concentration of 0.85%. The starting pH of this aqueous mixture was 13.6. The other conditions of the experiment were those of Example 1.

 In this case, 40 g of an oily fraction having a boiling zone of 150 to 2440 ° C. and 31 g of another oily fraction having higher boiling points were obtained.

 50% or more of the total coal liquefaction oil obtained by the process according to the present invention = distillation at a temperature between 150 and 2440C and the fraction thus obtained can be used as such as fusel , It is also possible to subject the liquefaction oil to fractionation distillation or to rectification with a view to using each fraction in its corresponding field of the petrochemical industry,

Claims (6)

10 / Coal liquefaction process, characterized in that the coal is dispersed in the pulverized state by suspending it in an aqueous solution of at least one alkali or alkaline earth metal hydroxide while maintaining said pulverized coal at the turbulent state in said solution for several hours and the oily phase obtained is separated from the aqueous phase. 20 / A method according to claim 1, characterized in that the turbulent state is maintained for 24 hours.  30 / A method according to claim 1, characterized in that the hydroxide solution is an aqueous solution of NaOH, KOH or residual liquor containing NaOH and resulting from the manufacture of NaOH by electrolysis.  40 / A method according to any one of claims 1 to 3, characterized in that the average particle size of the pulverized coal is about 0.05 to 0.2 mm. 50 / A method according to claim 4, characterized in that the average particle size of the pulverized coal is about 0.07 to 0.15 mm  6 / A method according to any one of the income indications 1 to 5, characterized in that the pH of the aqueous hydroxide solution is 10 or more, 70 / Method according to any one of the income indications 1 to 6, characterized in that the turbulent state is caused by agitation.