BE445339A - - Google Patents

Description

       

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 process for extracting fuel gas for engines. for the fuel gas mixtures for engines (liquefied gas-oil) which are used in increasing quantities to drive engines and vehicles, there are no generally valid standards with regard to their physical and chemical properties, but already them. Engine manufacturers often have certain conditions for gasoline fuel for engines. On the other hand, as a result of the increasing use of fuel gases for engines, it becomes necessary to strictly observe the correct composition of these gases, their boiling limits and other properties. important for their combustion.

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   When it is desired to avoid complicated and expensive subsequent treatments of the fuel gases obtained, this desideratum must be taken into account as much as possible as soon as possible.



   Although gas fuels for engines constitute relatively inexpensive fuels compared to other fuels, especially in comparison with gasoline blends, it is in the interests of the economy as a whole not to render their fuel. more expensive to manufacture as their consumption increases and despite the improvement in their quality, but to even try to make it as economical as possible.



   Various processes are known for the separation of hydrocarbons having two or more carbon atoms, included for example under the name of "gasol" and obtained from dry distillation gas, natural gas or the residual gases of the synthesis. gasoline; they require, almost without exception, the use of special refrigeration installations, for example ammonia installations, in order to be able to achieve the low temperatures necessary for the separation. These refrigeration installations constitute an important factor in manufacturing costs and investment costs.



   The present invention greatly simplifies and makes much less expensive the separation of the fuel gases from the raw gas, which is available to it and which most often contains hydrogen and nitrogen, while making it possible to obtain fractions. clearly distinct from each other and without in principle additional refrigeration installations being necessary, so that the above requirements can be met to a large extent. ,
The invention consists in that the fractions to be separated from the raw gas are first separated all together in the liquid state by cooling to low temperature under a suitable pressure.

   After the separation has taken place, mainly of hydrogen, nitrogen and methane, which would be

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 very troublesome at the next rectification, the division of the hydrocarbons into clearly separated fractions takes place much more simply than hitherto. In accordance with the invention, the cold necessary to compensate for the losses of cold is generated in part by the expansion of the residual gas and, in part, by the expansion of the liquefied part.

   When it is considered that the proportion of the residual gas is, for most of the gases taken into account, only of the order of magnitude of 40% of the raw gas, and that however it is possible, according to the invention, of continuously compensating by their-relaxation, a considerable part of the cold losses, without additional refrigerating installations, it is immediately understood that the invention also ensures a considerable advantage as regards the expenditure. of energy.



   As the subsequent rectification of the hydrocarbons must take place under pressure, it is quite necessary, after evaporation and heating, to compress the liquid part again to the pressure at which the separation will take place, but the work at providing here is not only less important than the work of compressing ammonia in other installations; because the whole work is also much simpler. When, as is necessary to obtain good refrigeration efficiency with a relatively low initial pressure, mainly when the hydrogen content is high, the expansion of the residual gas takes place with the production of external work, for example, in an expansion machine, the energy thus recovered contributes to lowering manufacturing costs.



   The method according to the invention will be described, in what follows, in relation to the appended drawing showing, by way of example, one embodiment of the invention.



   The raw gas is compressed, for example a residual synthesis gas with a content of 75 to 80% of hydrocarbons, in major

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 part saturated, and about 15% in hydrogen, in a compressor K1 for example at 20 atmospheres and, after abduction, in the refrigerant K3, of the heat produced by the compression, it is conducted through pipe 5 to the apparatus countercurrent 1 and cooled to a temperature of -150 or less. Almost all of the hydrocarbons with two or more carbon atoms are thus liquefied and separated from the residual gas in separator 2.

   The residual gas (for example hydrogen, nitrogen, carbon monoxide and methane) is dependent approximately at atmospheric pressure, preferably in an expansion machine E or in an expansion turbine. , which can transfer the recovered work, for example to the installation of compressors. The expanded residual gas leaves the installation through pipe 8 after it has given up, in the counter-current apparatus 1, its cold to the incoming raw gas. To achieve favorable temperature conditions, it is advantageous to heat a little in the counter-current device 1, before entering the expansion machine, the residual gas leaving the separator 2 through the pipe 7.

   The liquid obtained in separator 2, which contains almost all the hydrocarbons, is expanded to approximately atmospheric pressure by means of the regulating valve 9, and is evaporated in the counter-current apparatus 1, also by heat exchange with the incoming raw gas, and it is heated to approximately room temperature, and then condensed, in compressor K2, to a pressure of approximately 25 to 30 atmospheres, at which separation takes place.



  After this compressor K2 is the refrigerant K4 intended to dissipate the heat generated by the compression. The condensed gas then passes through the pipe 10 into the rectification column 3 where the fractionation takes place, according to the invention, at a temperature equal to or greater than approximately + 20.



  Hydrocarbons with one or two carbon atoms (fraction of

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 thane) are removed in this column and can be withdrawn at the top of the column, while the hydrocarbons with three atoms or a greater number of carbon atoms are brought from the bottom of column 3, through pipe 11, to the rectification column 4 which is operated, for example, under a pressure of about 15 atmospheres and at the same temperature. The fuel gases for engines with three carbon atoms (propane fraction) and those with four carbon atoms (butane fraction) are then withdrawn from this column.



   As the gas led through the pipe 10 to the rectification apparatus is practically free of hydrogen, nitrogen and carbon monoxide, it is possible, under the relatively simple working conditions described, to carry out the rectification with more of success, and with a more distinct separation of one fraction from the other in columns 3 and 4 than would be possible even in columns cooled with ammonia, working with less pure mixtures of gases.



   The process according to the invention can also be extended to the extraction of two-carbon hydrocarbons, working in the known manner, to produce methane, ethane and ethylene. mixture of hydrocarbons with one and two carbon atoms which comes out of the top of column 3. ge an additional refrigeration installation. In this way, this process can optionally be applied to obtaining hydrocarbons with two carbon atoms only.


    

Claims (1)

R e v e n d i c a ti o n s. 1.- Process for extracting fuel gases for engines to capture residual gases from gasoline synthesis, from gas from the dry distillation of lignite, or from mixtures of <Desc / Clms Page number 6> similar crude gases containing hydrocarbons with two or more carbon atoms in sufficient quantity, by cooling the crude gas to low temperature, by partial liquefaction of the crude gas followed by rectification of the condensation product, but without use of an additional refrigerant circuit, characterized in that the condensation of the hydrocarbons with two or more carbon atoms takes place with the aid of the cold generated by the evaporation of the condensation product which is obtained from gas crude and which is sent directly against this gas, so as to produce a direct heat exchange in the known manner and in that the additional losses of cold are compensated in the same temperature zone by the expansion, with production of work; non-liquefied residual gas. 2. A method according to claim 1, characterized in that heating, by heat exchange with the incoming raw gas, the non-liquefied part before it expands, expands in the manner known by producing work. 3. A method according to claim 1, characterized in that the separation of the liquefied and evaporated part again takes place, in two rectification columns, in three fractions containing, as main constituents, one to two, or three or even four carbon atoms. 4. - Method according to claim 1, characterized in that the gas mixture escaping at the top of the column (3) is decomposed, in the known manner, into two or more fractions.