JPH028765B2 - - Google Patents

Description

[Detailed description of the invention]

The invention is based on French patent application no. 7504525 of February 13, 1975 (French patent application no. 2300607).
This invention relates to an improved method for reducing the energy consumption and improving the efficiency of the method described in No. The process described in the above-mentioned patent application involves passing a gas mixture through a column packed with a selective adsorbent and purged with a carrier gas stream to separate at least one of the components of the gas mixture in a purified state. It's a method. The process is characterized by a first stage of injecting the gas mixture to be treated up to saturation of the selective solid adsorbent and, after the end of the continuous injection of the gas mixture, of the carrier gas and less than 40% of the gas injected in the first stage. The second step is to periodically inject the mixture and sequentially collect a fraction rich in unadsorbed portions and a fraction containing purified adsorbed components at the outlet of the column. This phenomenon is illustrated by the graph in FIG. 1, which shows the change in column outlet mole fraction over time. The saturation of the column, the start of elution 1 of adsorbed compounds, and peak 2 of unadsorbed compounds are clear from the graph. The interval t' between the beginnings of two consecutive peaks 2 indicates the duration of one cycle. In the second stage, the periodic injection of the gas mixture to be treated is continued for 1 to 120 seconds. The duration of each cycle is between 10 and 800 seconds, and the ratio of injection duration/cycle duration is less than 0.4.
The temperature at which this process is carried out is from 20 to 500°C and the pressure from 1 to 100 bar. Water is used as the carrier gas. According to the improved method of the present invention, it is possible to improve the purity of the components retained on the molecular sieve or selective adsorbent, and to obtain a mixture containing a high concentration of unretained components. be. Processing conditions are determined by preference, ie, whether a pure product or a concentrated mixture is desired. The method can be used with any gas mixture, especially gas mixtures containing two or more compounds. In this case, the various components can be separated into two different groups. However, it is necessary to carefully select the most suitable selective adsorbent based on the components of the gas mixture to be treated. Selective adsorbents include activated carbon, alumina, silica gel, natural or synthetic fluorites, especially zeolites A, Y, X, L, Omega ZSM5, mordenite,
It is selected from the group consisting of chabazite, erionite, and offretite. The fluorites may be exchanged with various cations. The choice of adsorbent is primarily based on the mixture to be separated. A feature of the improved method of the present invention is the use of unique equipment to adjust operating conditions to provide improved performance and energy savings. First, the device includes a plurality of adsorbent-filled columns arranged in parallel and operates in such a way that the injection into the columns is maintained constantly so that evaporation of the treated material occurs continuously at a constant rate. . If a pure product is desired, a shunt is provided for discharging the vaporized process material. The heating of the carrier gas and the evaporation of the processing material may take place in the same furnace or by two separate furnaces. The column effluent exchanges heat with the carrier gas and the process material in an exchanger. The column effluent is cooled and the fractions are collected by condensation. The carrier gas is normally recycled. When it is desired to obtain pure product, uncondensable products are removed from the carrier gas prior to recycling. This process is carried out using conventional adsorbents (activated carbon, molecular sieves, alumina, silica gel). Above the effluent of each column is placed an analyzer, a comparison catalometer, which emits a signal similar to that of FIG. A unique microprocessor device coupled to the programmable automatic controls the direction of the effluent and delivers it to either of the two product groups. Furthermore, the automaton controls the injections between the various columns. Preferably the process is carried out under pressure. The method of the present invention has the following improvements compared to the original method described at the outset. - While in the original process some of the non-condensable material was lost along with the carrier gas, the process according to the invention recirculates the carrier gas and is thus more economical. - In the original method, evaporation occurred discontinuously, but in the method of the present invention, evaporation can occur continuously due to the parallel arrangement of multiple columns. While discontinuous processing is economical only for small-scale production, continuous processing using industrial furnaces can be economical for production on any scale. Furthermore, for equal material throughput, discontinuous systems consume more energy than continuous systems. - heat can be saved due to the heat exchange between the treated material and the effluent; - Since the effluent of each column is measured continuously, it is possible to adjust the optimal conditions for the production of the desired fraction. That is, production of a fraction with a predetermined composition or a predetermined yield is ensured. - Product recovery efficiency is high as the process is usually carried out under pressure. In the present invention, a selective hydrogenation step of aromatics is added. FIG. 2 is a schematic diagram of a specific embodiment of manufacturing equipment based on the improved method. The material to be treated is introduced through pump 1, preheated and partially evaporated in 2, and then passed through pipe 5.
It reaches the furnace 4 through the furnace 4, where it is heated to the processing temperature, and enters the separation columns 22, 23, 24. Three separation columns 22, 23, 24 are packed with selected adsorbents and simultaneously use a hydrogenation catalyst. The recirculated carrier gas is preheated in exchanger 3 and enters furnace 4 via pipe 6 where it is heated to processing temperature. The recirculated gas reaches the three columns via pipe 8 and is distributed by valves 12, 13, 14 into three equal flow rates. The vaporized processing material is transferred to valves 9 and 1.
0, 11 into columns 22, 23 or 24 or bypass 34 by valve 16.
injected into. The product leaving the column mixed with the carrier gas is, depending on its composition, passed through valves 17,1.
8, 19, 20, 21, 35 to line 25 or 26. The gaseous effluents passing through lines 25 and 26 are cooled in exchangers 2 and 3, respectively;
The condensate collected at 29, 30 is sent to a storage tank or to a stabilization system to remove dissolved trace carrier gas. The carrier gas collected at 29 and 30 is recycled and pressurized by compressor 31. Two types of fractions with high concentrations of specific substances (Figure 2)
The effluent of the column can be directed in two or three directions, depending on whether it is desired to separate into three fractions or into three fractions (FIG. 3). FIG. 3 is a schematic diagram of an apparatus capable of producing three concentrated fractions. Valves 39, 40, 41 capable of directing the effluent in a third direction are arranged at the outlet of the column, through which the effluent is directed to a condenser 42, and the condensed fraction is recovered in line 45. , 43 is recycled to the compressor 31. Valve 9, 10, 11, 15, 16, 12, 13,
14, 17, 35, 18, 19, 20, 21 are
Three analyzers 36,3 placed at the outlet of the column
7, 38. The automation of the system is shown in FIG. In FIG. 7, process material 7 and carrier gas 8 are supplied to column 22 via a remotely controlled valve 9.
reach. A casalometer-type analyzer 36 is connected to the outlet 17 of the column via a line 48 . This cassalometer continuously measures the molar flow rate of hydrocarbons exiting the column. This flow rate is the first
As shown in the figure. This continuous information is analyzed by microprocessor 103. Based on this signal, microprocessor 103 measures the time elapsed between the opening of valve 9 and the appearance of hydrocarbons on line 48. This time is transmitted to the programmable automaton 109, and the automaton 109
controls valves 46 and 47 based on this time value. Furthermore, the automant 109 periodically keeps the valve 9 open for a given period of time and communicates this to the microprocessor. The invention will now be described on the basis of non-limiting examples. Example 1 Using the experimental apparatus shown in FIG. 6, the following processing was carried out. Carrier gas (nitrogen) is continuously introduced through line 82 at a constant flow rate. The sample arriving from line 80 is injected into the carrier gas via valve 81 and line 91.
This injection is continued for a specified period of time, which is called the “infusion time”.
It is designated as. The length of the injection time is determined based on a predetermined period designated as a so-called cycle time, and the injection is repeated discontinuously. The mixture is vaporized in vaporizer 83 and then
enters the flask 84 filled with molecular sieve in gaseous state. The mixture is drawn off from line 94 and, depending on its composition, is sent to condensers 89, 8 via valves 92, 93, respectively.
8. The two-phase mixture obtained in the condenser is transferred to flask 10.
Separate into components at 0.87. 2 with high concentrations of n-paraffins and isoparaffins, respectively.
The liquid phase of the seeds is collected. The carrier gas is recovered and purified in unit 86. Example 2 In this example, a comparative test using a device containing one column is performed to demonstrate the improvements obtained with recirculation and pressure (pressurization was already used in the original patent). The treated sample is technical n-pentane with the following composition. n-butane 140ppm isopentane 5% n-pentane 92.4% 2,2-dimethylbutane 0.21% cyclopentane 2.15% Treatment conditions

【table】

[Table] The processing capacity of the same column has increased by 2.2 times. Does not consume liquid nitrogen. Does not consume carrier gas nitrogen. The yield of n-pentane increases. The above results are attributed to the use of recirculation and pressure. Example 3 The same sample as in Example 12 of the original patent is processed. Sample % Isoparaffins 61.07 Normal paraffins 31.25 Naphthenes 7.68 RON 77.30 RON: Mixture research method Octane number treatment conditions

【table】

[Table] When treated at an evaporation temperature of 250°C, the improved method produces RON89 containing only 10% normal paraffins.
An iso fraction of 60% is obtained. Example 4 From a safety or purity standpoint, it is often necessary to de-aromatize the resulting compound and hydrogenate the aromatics it contains. For this purpose, a hydrogenation catalyst layer is added to the molecular sieve as shown in FIG. In FIG. 5, a molecular sieve 141 is packed above a hydrogenation catalyst layer 142 in a column 140, and a sample 143 and a carrier gas 14
4 is evaporated at 145 and introduced into the column, and the effluent is taken out at 146. When an n-heptane fraction was treated using a hydrogenation catalyst containing 0.6% platinum to alumina (catalyst thickness 17 cm for 2.30 m adsorbent layer), the following results were obtained.

[Table] Example 5 If you want to hydrogenate only the n-fraction, use the fourth
It is sufficient to employ the apparatus shown in the figure. A catalyst is housed in a reactor 59 similar to that shown in FIG. 5, and placed on the normal paraffin extraction line 26 before the exchanger 3. Example 6 Desulfurized light gasoline having the following composition is separated and treated. Weight % Isoparaffins 54.78 N-paraffins 42 Benzene 2.52 Toluene 0.7 The separation column is operated under the following conditions. - VVH (flow rate of liquid sample per sieve volume)
0.8 - molar ratio of carrier gas flow rate/liquid sample flow rate per hour = 4 - special 5Å sieve - injection time 1 minute - cycle time 4 minutes - 1st fraction collection time 1 minute - 2nd fraction collection time 1 minute 20 seconds - 3rd fraction collection time 1 minute 40 seconds - Temperature 280°C - Pressure 12 bar. Three fractionated products are obtained. - In the first fraction there is a high concentration of isoparaffins and aromatics. - High concentration of aromatics in the second fraction. - The third fraction has a high concentration of normal-paraffins. Sample flow rate: 1Kg/hour.

[Table] Example 7 The treated sample contains 61.07% isoparaffins and n-
It consists of 31.25% paraffins and 7.68% naphthenes. The unit is weight %. The RON of this sample is
It is 77.30. The process is carried out in a pilot unit with one recirculation system and three parallel working columns under the following conditions: Pressure 20 bar Temperature 160°C Carrier gas Recirculated hydrogen flow rate
1200/hour Injection time for each column 1 minute 15 seconds Cycle time 4 minutes Sample flow rate 100 g/iso fraction obtained at the outlet 540 g/hour RON of iso fraction 88 Flow rate of n- fraction 560 g/hour. The research method octane number increases in the improved method compared to the original patent method (84−→88). This improvement is attributed to the use of three columns operating in parallel and the use of hydrogen recirculation. Example 8 In this example, hydrogen-treated light gasoline is used as a sample. The experimental apparatus is used to simulate the operation of the apparatus shown in FIG. The following processing conditions are used. - Pressure 16 bar - Temperature 250°C - Cycle time 3 minutes - Injection time for each column 1 minute - Iso fraction collection time 1 minute - Sample flow rate 1000 g/hour - Number of columns 3 - Flow rate 1000/hour - Liquid sample Capacity/Sieve Capacity=1 Sample Analysis The sample is a hydrotreated straight-run light gasoline obtained from heavy Arabian crude oil and having the following characteristic values. Density at 15°C 0.645 Vapor pressure TVR 0.720b Distillation at 70°C 100% Distillation at 100°C 100% Lead-free MON 69 Pb0.4g/added RON 84.2 Lead-free MON 68 Pb0.4g/added MON 83.3 n-paraffins 51% Naphthenes + aromatics 4% Isoparaffins 45% S content < 1 ppm Analysis of sample extracted from heavy Arabian crude oil (mol%) 1 Hydrogen 2 Methane 3 Ethane 4 Propane 5 Isobutane 6 n-Butane 0.44 7 Iso -Pentane 14.73 8 n-pentane 33.16 9 cycloC ₅ 1.71 10 3-methyl C ₅ 29.89 11 n-hexane 17.38 12 cycloC ₆ 2.09 13 Benzene 0.29 14 Iso-heptane 0.29 15 n-heptane 0.02 16 Methyl-hexane Kuro C ₆ 0.0 next In the table, - all numbers indicate mol%. - The second column shows the mol% of the chemical components of the sample. - the third and fourth columns show the components of the iso- and n-cuts, respectively, after separation in mol %; - Column 6 shows the composition of the chemical groups in mol %. - Columns 7 and 8 are iso fraction and n-
The composition of the chemical groups of the fractions is given in mole %.

【table】

【table】 [Brief explanation of drawings]

FIG. 1 is a graph showing the change in mole fraction at the column outlet over time; FIG. 2 is a schematic diagram of a specific embodiment of the apparatus for carrying out the improved method of the present invention; and FIG. 3 shows the production of three concentrated fractions. Fig. 4 is an explanatory diagram of the equipment used for hydrogenation of n-fraction, Fig. 5 is an explanatory diagram of the hydrogenation catalyst layer added to the molecular sieve, Fig. 6 is an explanatory diagram of the experimental apparatus used in Example 1, and FIG. 7 is an explanatory diagram showing automation of the system. 2, 3... Exchanger, 4... Furnace, 22, 23, 2
4... Separation column, 36, 37, 38... Analyzer, 42... Condenser, 103... Microprocessor, 109... Automaton.

Claims (1)

[Claims] 1. A first stage in which a gas mixture to be treated is injected into a column packed with a selective adsorbent together with a carrier gas until the selective adsorbent is saturated, and a purification solution injected in the first stage. a second stage in which a mixture of less than 40% of the desired gaseous product and a carrier gas is periodically injected into the column, and then a fraction rich in unadsorbed components and a purified fraction containing adsorbed components are sequentially collected. A process for separating the components of a gaseous mixture containing a mixture of gases, using an apparatus equipped with a plurality of parallel columns packed with selective adsorbents supplemented with hydrogenation catalyst beds, at a temperature and pressure determined for each product to be purified. An improved method for the separation of components of a gaseous mixture, characterized in that the evaporation of the material to be treated occurs continuously at a constant rate under the conditions of A separation method using hydrogen, characterized in that the gas mixture to be treated contains n-paraffins and isoparaffins together with at least one aromatic hydrocarbon. 2. The evaporation of the gas mixture takes place at least once, with preheating of the material to be treated and the carrier gas by the effluent.
2. The method of claim 1, wherein the carrier gas is produced in a separate furnace and the carrier gas may or may not be recycled gas. 3 Continuous evaporation of the treated material in the column
Method according to claim 1, characterized in that an injection time of 10 to 40 minutes in one stage and an injection time and cycle time of 10 seconds to 1 minute in a second stage are ensured. 4. Process according to claim 1, characterized in that the evaporation temperature is in the range from 20°C to 500°C and the pressure is in the range from 1 to 100 bar.