Recovery of a secondary ethylene stream from an ethylene purification process

ES 2 186 014 T3

DESCRIPTION

Recovery of an ethylene side stream from an ethylene purification process.

This invention comprises a process for using pressurized charge gas mixtures of olefins, aliphatics, hydrogen, carbon monoxide, and other components, from a variety of olefin preparation / generation techniques, to produce suitable ethylene-rich product streams. For use in the manufacture of ethylene-bearing derivative products.

Background of the invention

Ethylene is the main petrochemical product in terms of volume of production, importance of sales and number of derivatives. Total world ethylene production in 1995 will be estimated at 76 million tons per year, expectations are for a growth rate of around 3% per year, and it finds that this growth will require significant capital investment in new plant facilities. production. Average selling prices in the order of $ 440 / tonne, which translates into global cash volume for ethylene businesses in excess of $ 30 trillion per year. The intermediate and final uses of ethylene include the production of plastics, resins and fibers, and a multitude of other products.

Before ethylene can be sold or used, it is necessary to employ a process that recovers the ethylene component in a desirable ethylene-rich product stream, separating it from a myriad of other components, including methane, ethane, hydrogen, and Carbon monoxide, among others, all the components are found together in a single stream obtained from a different process of preparation / generation of olefins. Currently, a desirable ethylene-rich product stream is defined, generally by those skilled in the art, as having more than about 95% by weight of ethylene, containing substantially inert components such as methane and ethane in proportions less than about 2000 molar for every ppm and potentially reactive components such as hydrogen, carbon monoxide, carbon dioxide, propylene and others, in proportions less than about 20 molar for each ppm. This definition stems from the nature of derivative processes that use the ethylene-rich product stream, each suffering varying degrees of adverse process efficiency and economic impact associated with levels of various components without ethylene in the stream. Such material is hereinafter referred to as an ethylene-rich primary product stream.

The separation and recovery process that produces a primary stream of product rich in ethylene from components received from an olefin preparation / generation process, represents the majority of the total capital investment and energy use required for the manufacture of ethylene. . This reflects the difficulty associated with the techniques required to handle the normal low boiling points and the low relative volatilities of ethylene and the other components received from an olefin preparation / generation process. Furthermore, as recognized by those skilled in the art, energy use and capital recovery are generally the two largest cost elements, respectively, in the total cost of ethylene manufacture. Thus, the process by which one carried out recovery and separation to produce an ethylene-rich primary product stream is an important factor in the economic viability of ethylene manufacture.

Methods for the recovery and separation of ethylene found in multicomponent streams have been under consideration since 1940, when the first practical technique of large-scale generation of olefins from hydrocarbon pyroolysis, also called steam cracking, was developed and applied commercially. This olefin generation technique, now a substantially mature technique, now dominates the industry, using several different hydrocarbon feedstocks. Alternative processes of potential commercial importance for olefin generation are also emerging, such as methanol for olefin process, Kaiser Cove, US Patent Document A-4,499,327 and now offered by commercial license from UOP. As shown in Table 1, commercially important olefin generation techniques generally create different amounts of various bi-product components in a mixture with the desired ethylene component.

ES 2 186 014 T3

TABLE 1

Typical Component Distribution from Various Olefin Generation Techniques

<td>Process feed material (excluding water)</td><td colspan="3">Steam Cracking (1)</td><td>Methanol to Olefins (2)</td>

<td></td><td>Ethane (C2H6)</td><td>Light naphtha (boiling range 35-149 ° C95-300^°F)</td><td>Diesel oil atmospheric (interval of boiling 185-335^°C- 365-635^°F)</td><td>Methanol (CH₃OH)</td>

<td>Production,% by weight (excluding water) H2</td><td> 3,93</td><td> 1,00</td><td> 0,63</td><td> 0,03</td>

<td>CO</td><td>Clues</td><td>Clues</td><td>Clues</td><td> 0,49</td>

<td>CO2</td><td>Clues</td><td>Clues</td><td>Clues</td><td> 2,46</td>

<td>ch₄</td><td> 3,82</td><td> 18,00</td><td> 11,20</td><td> 1,45</td>

<td>C2H2</td><td> 0,43</td><td> 0,95</td><td> 0,47</td><td> 0,00</td>

<td>C2H4</td><td> 53,00</td><td> 34,30</td><td> 26,50</td><td> 53,73</td>

<td>C2H6</td><td> 35,00</td><td> 3,80</td><td> 3,40</td><td> 1,67</td>

<td>C3H4</td><td> 0,06</td><td> 1,02</td><td> 0,80</td><td> 0,00</td>

<td>C3H6</td><td> 0,89</td><td> 14,10</td><td> 13,40</td><td> 26,37</td>

<td>C3H8</td><td> 0,17</td><td> 0,35</td><td> 0,25</td><td> 1,53</td>

<td>C4H6</td><td> 1,19</td><td> 4,45</td><td> 5,00</td><td> 0,00</td>

<td>C4H8</td><td> 0,18</td><td> 3,70</td><td> 3,70</td><td> 6,64</td>

<td>C4H10</td><td> 0,22</td><td> 0,10</td><td> 0,10</td><td> 1,21</td>

<td>C5</td><td> 0,27</td><td> 2,75</td><td> 2,75</td><td> 3,37</td>

<td>C₆- C8</td><td> 0,39</td><td> 1,20</td><td> 1,20</td><td> 0,88</td>

<td>Benzene</td><td> 0,37</td><td> 6,90</td><td> 6,90</td><td> 0,00</td>

<td>Toluene</td><td> 0,08</td><td> 3,20</td><td> 3,20</td><td> 0,00</td>

<td>Xylene +</td><td> 0,00</td><td> 1,30</td><td> 1,30</td><td> 0,00</td>

<td>Ethylbenzene Styrene</td><td> 0,00</td><td> 0,79</td><td> 0,79</td><td> 0,00</td>

<td>C₉ - 400 ° F</td><td> 0,00</td><td> 2,96</td><td> 2,96</td><td> 0,00</td>

<td>Gasoline</td><td> 0,00</td><td> 15,45</td><td> 15,45</td><td> 0,00</td>

<td>Coal</td><td>Clues</td><td>Clues</td><td>Clues</td><td> 0,17</td>

<td>Total</td><td> 100,00</td><td> 100,00</td><td> 100,00</td><td> 100,00</td>

Note:

(1) by Howe-Grant, M.-Ed. Encyclopedia of Chemical Technology, Fourth Edition, Volume 9, page 880 (1994)

ES 2 186 014 T3 (2) by Nirula, SC, Ethylene from Methane, Stanford Research Institute International Procedure Economic Program Report No. 208, page 4-2 (1994)

This mixture is generally unsuitable for further commercial use, therefore a different separation and recovery procedure is needed. It should be noted that this is the case for many other olefin generation techniques not shown in Table 1, and for blending combinations from those techniques, a commercially important example being off-gas blends generated in various refinery processes. , combined with mixtures created in steam cracking. Additionally, such a mixture may be a combination of those created by the olefin generation process and recycled streams from other parts of an ethylene-derived or ethylene-derived manufacturing facility, and may contain other components than those listed in the Table 1.

The prevailing conventional wisdom regarding the manufacture of ethylene is also directed, to create ethylene and by-product components in a mixed stream by an olefin generation technique or combination of techniques, to also prepare that stream for introduction to the subsequent separation and recovery procedure. . This may include, in various embodiments and sequences, the actions of cooling the stream from conditions to which the olefin generation reaction is carried out under close ambient conditions, comprising the gaseous stream normally mixed at pressures between 1, 3 x 10³ y4,2x10³ kPa (200 and 600 psia), which remove almost all of the water, carbon dioxide, and sulfur compounds used or produced in the olefin generation stage, and which typically removes various liquid components at various pressures from the mixed stream. Therefore, the combination of the steps described above, namely those of olefin generation and olefin preparation, is expressed as being referred to in this context as the olefin preparation / generation process. It is recognized by those skilled in the art that the result of employing an olefin preparation / generation process is the production of a stream known as "charge gas", called thus because it is both the gaseous charge of the mixed component from expensive compressors and large within the process, and the gas charge of the mixed component to the subsequent separation and recovery process. This latter stream was referred to in this context as a pressurized mixed olefin carrier charge gas.

Although methods are known for the recovery and separation of ethylene from a mixed and pressurized olefin-bearing charge gas, the normal low boiling points of ethylene and other components require the use of fractional distillation techniques and liquid-vapor subabite. very low temperature, to have a high recovery of the ethylene molecules present in a primary stream of product rich in ethylene, and thereby provide the ethylene manufacture with sufficient efficiency for economic viability. Of particular expense in these processes are equipment that serves to separate ethylene from lower boiling components such as hydrogen, carbon monoxide and methane. In today's state-of-the-art separation and recovery procedures dominating the industry, temperatures on the order of -51 to -137 are used topically.^°C (-60 to -215^°F) in certain equipments, which require special refrigeration and metallurgical systems for the effect, which represents an important part of the total capital cost and energy consumption of the ethylene manufacture. These are generally known to those skilled in the art as a cooling train and demethanizer tower and a substantially dedicated cooling system is needed to run the equipment at the requisite low temperatures, which normally use ethylene as the coolant but sometimes use methane and methane. light hydrocarbon mixtures, among other refrigerants. They are also in the separation and recovery process to produce a product stream rich in ethylene, the C2 separator and deethanizer fractional distillation towers, and reactors to eradicate the presence of acetylenes and dienes, together with heat exchangers, pumps and others support teams.

A less frequently practiced alternative for the recovery and separation of ethylene from methane and lower boiling components using temperatures in the range of -51 to -137^°C (-60 to -215^°F), comprises employing a combined fractional distillation and absorption technique in a demethanizer tower, known to those familiar with the technique as an absorber demethanizer. In this technique, a large volume of ethylene-free material of substantially higher boiling point than ethylene, called lean oil, is introduced to the absorber demethanizer on top of the feed plate (s), typically the condenser drum or top plate, in liquid state at around -28 to -46^° C (-20 to -50^°F). The dominant amount of lean oil provides the volume of the molecules in the vapor phase of the resulting total liquid-vapor equilibrium in the middle of all the components, and thereby serves to force the volume of the ethylene in the liquid phase, absorbing it effectively. Methane and the lower boiling components, which are more volatile, tend to

ES 2 186 014 T3 allowed to remain in the vapor phase, and thus over the course of numerous plates in the absorbent demethanizer tower, the ethylene separation is carried out as the lean oil with the absorbed ethylene falls to the bottom from the tower, and the methane and low boiling components rise to the top of the tower. The absorber demethanizer has the potential advantage of eliminating the cooling train, substantially dedicated cooling system, and some of the special metallurgy required to operate at temperatures below -48 ° C (-55 ° F). However, with most types of mixed and pressurized olefin carrier charge gas, these advantages are outweighed by associated increases in high temperature refrigeration loads, power consumption, and cooling equipment to handle absorptive heat. of ethylene in the lean oil inside the absorber demethanizer. In addition, additional size and power consumption is required in subsequent distillation towers in the stripping and total recovery process to separate the large volume of lean oil from the desired ethylene and other by-product components. For a representative example, see US Patent A-5,019,143 issued to Mehra, et. to the.

An advanced technology in the field of ethylene separation and recovery processes is that of non-cryogenic and non-distillative techniques, especially those that serve to separate olefins from non-olefins. A practical example is that of chemical absorption and desorption, such that the use of aqueous silver nitrate solutions in the British Petroleum "Selective Olefin Recovery" technology, described by Barchas in his presentation conference entitled Olefin Recovery Via Chemical Absorption and currently offered Per license from Stone and Webster, Inc., operating at intervals between about 4,137 kPa / 21^°C (600 psia / 70^°C) and 13.8 kPa / 202^°C (2 psia / 400^°F) by absorption and desorption, respectively. Another is the use of membrane spacers, such as described in US Patent A-5,082,481 to Barchas, et. al., to remove approximately 20% of the hydrogen from a mixed and pressurized olefin-bearing charge gas, prior to any cooling of the charge gas. These techniques have the advantage of a low capital cost per unit of ethylene processed, yet are currently not capable by themselves of transforming a sufficient amount of ethylene into the pressurized mixed olefin-bearing charge gas into a rich product stream. in ethylene of sufficient purity for the cost-effective manufacture of ethylene. They can be synergistically combined with distillation equipment to produce some advantageous results, as described in US Patent A-5,452,581 to Dinh, et. al., in which membranes are used to remove hydrogen in the cooling train, thus saving energy by moving the refrigeration load from a low-temperature refrigeration system substantially dedicated to a high-temperature refrigeration system. However, they cannot totally eliminate the cooling train, low temperature cooling system, or fractional or absorptive distillation. Rather, its high value mine seems to be in applications in streams containing relatively low volume secondary ethylene, such as a purification process that is high in ethylene content in the case of chemical absorption. Hereinafter such equipment and techniques should be called volume separation techniques.

Despite the specific realization of a separation and recovery process used in the manufacture of ethylene, the vast majority of such processes refer, in conventional wisdom, to producing a primary stream of product rich in ethylene, individual, suitable for all the possible end uses in the subsequent manufacture of ethylene derivatives. The predominance of the processes that produce a primary stream of product rich in ethylene, individually pass historically through the manufacture of polyethylene, which comprises the majority of the total use of ethylene for the manufacture of derivatives, and which has the most rigorous descriptive memories of all. derivatives, which normally require a high purity ethylene rich product stream.

However, the prevailing conventional wisdom regarding the compositional requirements of the resulting ethylene-rich primary product stream for the manufacture of derivatives has just been tested in the industry. In the Purvis conference presentation titled Cracker / Derivative Unit Integration, the recognition that many derivative procedures do not require the historically high levels of ethylene purity required by polyethylene to function properly is discussed. One such process is for the manufacture of ethylbenzene, as described in US Patent A-5,476,978 to Smith, et. al., presenting the ethylene-rich product stream used as a feed may contain ethylene in concentrations as low as 5% by weight, and such a process, which is licensed from CDTech, Inc., of Texas, claims that the product stream rich in ethylene can contain considerable levels of hydrogen and carbon monoxide. Another derivative process is that for the manufacture of aldehyde, alcohol or ester, as described in the serial number of European Patent Application PCT / EP96 / 00361 of Kiss, et. al., wherein suitable feeds include an ethylene rich product stream that needs to contain only between 30 and 75% by weight of ethylene, and which may contain considerable amounts of hydrogen and carbon monoxide. In addition, the question of the purity of a primary product stream rich in

ES 2 186 014 T3 ethylene for use in making polyethylene itself, starts with ethylene concentrations as low as the 85% being treated. The reason for entertaining the production and application of an ethylene-rich primary product stream lower in ethylene content than historically dominant is to allow for reductions in energy and capital requirements associated with the production of a primary product stream. rich in ethylene, and finally providing cost reductions in the ethylene-bearing by-product.

US Patent A-3,055,183 describes a process for recovering high purity ethylene in which a stream is preliminarily treated, in column 2, to remove unwanted components such as carbon dioxide, water , materials such as tar, and liquid aromatics. The overhead 28 from the demethanizer is described as consisting primarily of methane and ethylene and may be returned to an upstream processing unit.

US-A-4,460,396 describes a process for producing ethylene in which the deethanizer overhead contains ethylene. Light hydrocarbons can be concentrated and removed from separating flask 11.

US Patent A-3,098,107 describes a cryogenic distillation light olefin recovery system with a complex heat exchange system interposed in a fairly conventional ethylene recovery and purification train. An adiabatic suubbit distillation is used to pre-separate the inorganic gaseous components plus residual amounts of methane from the volume of the hydrocarbon mixture before feeding the charge gas to the demethanizer.

Faced with the changing needs of the primary streams of product rich in ethylene for the manufacture of various derivatives, almost all current teachings in patents and open documentation continued to refer to making a primary stream of product rich in ethylene, individual from the separation procedure. and recovery. The few articles that refer to a different ethylene rich side product stream teach that the stream coming from the deethanizer fractional distillation tower to save the additional load on the separator tower C2. Until the applicant is aware, it is hitherto unknown to use a demethanizer tower to supply as an overhead product, an ethylene-rich side product stream for possible use in certain derivative processes, or to feed advantageous applications of the advanced art in low cost non-cryogenic and non-distillative separation techniques, while it continued to supply a primary stream of product rich in ethylene with more stringent compositional requirements for other derivatives, and that simultaneously reduce the energy requirements and capital costs for the recovery and total separation procedure, potentially eliminating the train. cooling system and dedicated low temperature cooling system, or alternatively that potentially eliminates the circulation and handling of the poor oil to the demethanizer tower.

Exhibition of the invention

The invention comprises a method of producing ethylene-rich product streams from a pressurized charge gas mixture of olefins, alifaotics, carbon monoxide and hydrogens made by olefin preparation / generation processes. The demethanizer tower condenser temperature within the total olefin separation / recovery facilities is increased above normal operating levels currently accepted as state-of-the-art technology, namely, above about -95.6 ° C ( -140 ° C). In a preferred embodiment, the method of this invention eliminates the need for cryogenic fractional distillation and other special separation equipment operating at temperatures below about -48^°C (-55^°F), and thus the heat exchange and refrigeration equipment necessary to achieve these low temperatures are also eliminated. Alternatively, in another preferred embodiment, the method of this invention eliminates the need for a circulating poor oil absorbent material, and thus also eliminates heat exchange equipment and reduces the load of fractional distillation and cooling required to handle that material. According to the process of this invention, an ethylene-rich side product stream can be produced as the overhead product of a distillation column at a suitable ratio and composition for subsequent generation of an ethylene-rich primary product, substantially free of components with a boiling point at least as low as ethylene. Additionally, the ethylene-rich product side stream may be suitable as a feedstock in the production of ethylene derivatives, or be sensitive to additional concentrations of ethylene using volume separation techniques or combinations thereof. Consequently, the capital and operating cost associated with manufacturing ethylene-rich product streams from pressurized charge gas mixtures made by olefin generation processes is significantly reduced through the method of

ES 2 186 014 T3 this invention.

The process of this invention comprises introducing a mixed and pressurized olefin carrier charge gas to an olefin separation / recovery facility that functions to perform at least the demethanization function, where within such facility volume separation devices may or may not be introduced to modify the compositions of the process stream, operating the demethanizer column to produce an ethylene-rich overhead product side stream and a bottom stream remainder; which subsequently make a primary stream of product rich in ethylene from said remainder of the bottom, possibly providing the secondary stream of product rich in ethylene as a feed material for the manufacture of derivatives or burned for disposal or generating useful heat. In a preferred embodiment, the ethylene-rich side product stream contained substantially all of the input components of a boiling point at least as low as ethylene. In another preferred embodiment, the demethanizer tower operates with a condenser temperature above about -48 ° C (-55 ° C) in the absence of poor oil absorption, within the olefin recovery and separation facility in the absence of a cooling train.

Brief description of the drawings

Figure 1A is a schematic diagram of the olefin recovery and separation facilities of an ethylene plant using a preferred embodiment of the present invention, showing the production of an ethylene-rich side product stream from a distillation column. fractionated demethanizer that is the first column in the total series of columns, followed by a deethanizer, and a C2 separator that produces as overhead product, a primary stream of product rich in ethylene.

Figure 1B is a schematic diagram of the olefin recovery and separation process from an ethylene plant using a preferred embodiment of the present invention, showing the production of an ethylene-rich side product stream from a fractional distillation column. demethanizer which is the first column in the total series of columns, followed by a deethanizer that produces as the overhead product, a primary stream of product rich in ethylene.

Figure 1C is a schematic diagram of the olefin recovery and separation process from an ethylene plant using a preferred embodiment of the present invention, showing the production of an ethylene-rich side product stream from a fractional distillation column. demethanizer that is the first in the total series of columns, followed by a C2 separator that produces as a top product, a primary stream of product rich in ethylene.

Figure 1D is a schematic diagram of the olefin recovery and separation process from an ethylene plant using a preferred embodiment of the present invention, showing the production of an ethylene-rich side product stream from a fractional distillation column. demethanizer, which is the second in the total series of columns, preceded by a deethanizer column and followed by a C2 separator column.

Figure 2 is a modification of Figure 1D, in which lines of dots are used to indicate the potential presence of various pieces of equipment in the present invention as optional embodiments, as an example of how various pieces of equipment can be used with the series of columns of fractional distillation in any order or sequence.

Detailed description of the invention

Related to Figure 1A, an olefin preparation / generation process (0) creates a pressurized mixed olefin carrier charge gas (1) which is fed to a demethanizing fractional distillation column (2) at a pressure between about 1,379 and 5,516 kPa (200 and 800 psia), and preferably in the range of about 2,758 to 4,275 kPa (400 to 600 psia) which is converted to be between the optimal procedure (0) based on the energy and capital requirements for compression and final composition of the side stream. resulting ethylene-rich product treated below. In this embodiment, the charge gas is cooled to a temperature no lower than -48^°C (-55^°F), in a heat exchange equipment (3) before entering the feed plate of the demethanizer column as stream (4). Within the demethanizing column, fractional distillation takes place between multiple plates, which ultimately results in a stream of steam (5) that enters the overhead condenser (6). In the overhead condenser, heat is removed from the inlet steam until

ES 2 186 014 T3 that the material in the condenser (7) partially condenses near a refrigerant at a temperature between about -18 ° C (0 ° F) and not less than -48 ° C (-55 ° F ) in the range of about -29 to -46 ° C (-20 to -50 ° F), as one of the optimal condenser heat transfer areas, energy requirements of the refrigerant system, and the resulting composition of the product. ethylene-rich secondary treated below. Stream (7) is then introduced into a drum (8), or other liquid-vapor separation device. A liquid stream (9) is created and returned to the demethanizer column as reflux to facilitate fractional distillation, and it is observed that no lean oil is introduced to the demethanizer column at this or any other point. Furthermore, a vapor stream (10) manifests itself as an ethylene-rich side product stream, containing mainly ethylene and practically all input components with lower boiling points than ethylene, including hydrogen, carbon monoxide and methane. , and very little of the components boiling higher than ethylene.

Said demethanizing column also manifests a liquid bottom stream (11), a part of which (12) is introduced into the column boiler (13), in which heat is introduced to create a mixed liquid-vapor stream ( 14) that returns to the column to facilitate fractional distillation. The remainder is removed from the demethanizer column as a bottom liquid product (15), comprising the remainder of the input ethylene and the higher boiling components and practically none of the lower boiling components than ethylene.

The ratio of ethylene in the ethylene-rich side product stream relative to that of the mixed and pressurized olefin-bearing charge gas is mostly a function of the ratio of ethylene to hydrogen, ethylene to carbon monoxide, and ethylene to methane in the charge gas, and the temperature and operating pressure of the demethanizer condenser. The last parameters establish the set of liquid-vapor equilibrium compositions determined by the laws of nature in the drum (8), and the relationships of the previous component establish the material balance required to achieve the set of equilibrium compositions and therefore Therefore, the proportion of steam (10). In a preferred embodiment of the present invention, an olefin preparation / generation process will be selected that inherently creates, without the need for bulk separation devices, a pressurized mixed olefin-bearing charge gas with a very high ethylene-to-ethylene ratio. hydrogen, ethylene to carbon monoxide and ethylene to methane, such as Methanol to Olefins, or catalytic cracking of hydrocarbons as described in PCT patent document WO 96/16004, Application No.^°PCT / US95 / 15281 applicants Mohr, et. al., most preferably Methanol to Olefins. Table 2 defines the compositions and proportions of the ethylene-rich side product stream that will result from a given composition and proportions of the charge gas that may contain hydrogen, carbon monoxide, or methane in various ratios with ethylene.

TABLE 2

Compositions and ratios of ethylene-rich product side stream from demethanizer overhead to various feed compositions and condenser states

<td colspan="7">BASE: C₂H₄ with a lower boiling individual component at the demethanizer feed stream (1) in Figure 1A</td>

<td colspan="7">Capacitor states</td>

<td>Pres. KPa (psia)</td><td colspan="3"> 3103 (450)</td><td colspan="3"> 4137 (600)</td>

<td>Temp. ° C (° F)</td><td> -29(-20)</td><td> -37(-35)</td><td> -46(-50)</td><td> -29(-20)</td><td> -37(-35)</td><td> -46(-50)</td>

<td>Component of lower boiling in feed stream</td><td colspan="6">Rate and Proportion of Ethylene in the Ethylene-Rich Side Product Stream</td>

ES 2 186 014 T3

TABLE 2 (continued)

<td colspan="7">BASE: C₂H₄ with a lower boiling individual component at the demethanizer feed stream (1) in Figure 1A</td>

<td colspan="7">Capacitor states</td>

<td>Pres. KPa (psia)</td><td colspan="3"> 3103 (450)</td><td colspan="3"> 4137 (600)</td>

<td>Temp. ◦C (° F)</td><td> -29(-20)</td><td> -37(-35)</td><td> -46(-50)</td><td> -29(-20)</td><td> -37(-35)</td><td> -46(-50)</td>

<td>Hydrogen (H₂)</td><td rowspan="2"> 74</td><td rowspan="2"> 61</td><td rowspan="2"> 48</td><td rowspan="2"> 60</td><td rowspan="2"> 49</td><td rowspan="2"> 39</td>

<td>% C2H4 mold in the ethylene-rich by-product</td>

<td>Kg (lb.) deC₂H₄in the product secondary rich in ethylene per kg. (lb.) of H2 in the feed stream</td><td> 17,8 (39,2)</td><td> 9,7 (21,4)</td><td> 5,9 (13,0)</td><td> 9,6 (21,1)</td><td> 6 (13,3)</td><td> 4 (8,8)</td>

<td>Monoxide carbon (CO)</td><td rowspan="2"> 74</td><td rowspan="2"> 61</td><td rowspan="2"> 49</td><td rowspan="2"> 61</td><td rowspan="2"> 51</td><td rowspan="2"> 41</td>

<td>% C2H4 mold in the ethylene-rich by-product</td>

<td>Kg (lb.) deC₂H₄in the product ethylene-rich secondary per Kg. (lb.) of CO in the feed stream</td><td> 12,7 (27,9)</td><td> 4,5 (15,6)</td><td> 4,5 (9,8)</td><td> 0,7 (1,6)</td><td> 0,5 (1,0)</td><td> 0,3 (0,7)</td>

ES 2 186 014 T3

TABLE 2 (continued)

<td colspan="7">BASE: C₂H₄ with an individual lower boiling component at the feed stream of the demethanizer (1) in Figure 1A</td>

<td colspan="7">Capacitor states</td>

<td>Pres. KPa (psia)</td><td colspan="3"> 3103 (450)</td><td colspan="3"> 4137 (600)</td>

<td>Temp. ° C (° F)</td><td> -29(-20)</td><td> -37(-35)</td><td> -46(-50)</td><td> -29(-20)</td><td> -37(-35)</td><td> -46(-50)</td>

<td>Methane (CH₄)</td><td rowspan="2"> 69</td><td rowspan="2"> 55</td><td rowspan="2"> 43</td><td rowspan="2"> 68</td><td rowspan="2"> 43</td><td rowspan="2"> 34</td>

<td>% C2H4 mold in the ethylene-rich by-product</td>

<td>Kg (lb.) of C2H4 in the ethylene-rich byproduct per Kg (lb.) of CH4 in the feed stream</td><td> 1,7 (3,8)</td><td> 1 (2,1)</td><td> 0,6 (1,3)</td><td> 0,9 (1,9)</td><td> 0,5 (1,1)</td><td> 0,4 (0,9)</td>

Note: When compiled using the PRO / II chemistry simulation program, from Simulation Sciences, Inc. of California, which uses the Soave-Redlich-Kwong equation of state, which assumes at least five theoretical plates above the plate of they were fed higher.

As long as the ratio of ethylene to the lowest boiling component exceeds that listed in Table 2, it is possible to create an ethylene-rich side stream of product as a demethanizer overhead and have excess ethylene in the bottom stream with which to subsequently creating a primary stream of product rich in ethylene. The presence in the demethanizer feed of components with a higher boiling point than ethylene, will have only a minor impact on the data shown in Table 2, given that the number of fractional distillation plates, location of the feed between the plates and thermal charges of the condenser and tank, in any case, they are chosen to carry out a separation that ends in the overwhelming proportion of the components that leave the demethanizer in the bottom stream. This is generally the chosen mode of operation due to the presence of propylene in the demethanizer feed, while various ethylene-derived processes can tolerate hydrogen and inerts, they cannot tolerate other olefin species well, and propylene has a cost-effective value in its own good. However, to the extent that components with a higher boiling point than ethylene are present in the ethylene-rich side stream of product, particularly ethane if it is present in sufficiently large proportions in the feed to the demethanizer, the concentration of ethylene in the stream and the proportion of ethylene relative to the lowest boiling component was reduced from the figures shown in Table 2, without changing the nature of this invention.

The level impact of the low boiling components are approximately additive. If the hydrogen, carbon monoxide, and methane are all present in the demethanizer feed along with ethylene, the proportion of ethylene in the ethylene-rich side product stream would be approximately the sum of the independent proportions listed in Table 2. The composition of the stream will be approximately the average weight of the independent compositions listed in Table 2.

ES 2 186 014 T3

In one embodiment, given certain cost-effective circumstances and a relatively low proportion of the ethylene-rich product side stream, it may be desired to burn just this stream for disposal or to generate useful heat.

Returning to Figure 1A, the bottom stream from the demethanizer (15) is introduced into a deethanizer fractional distillation column (16). In this column, by techniques well known in the art, an overhead stream (17) is produced that contains substantially all of the input ethylene and very little of the higher boiling point components than ethane, and a stream background (18) containing very little ethylene among the rest of the input components.

The overhead product stream from the deethanizer (17) is then sent to a fractional distillation column of the C2 separator (19), where using well-established techniques in the art, an overhead stream (20) is produced that contains practically all the input ethylene and very little ethane, which is the ethylene-rich primary product stream of the total process of this invention. A bottom product (21) is also produced consisting of very little ethylene and most of all the input ethane and higher boiling components.

Additional embodiments of the immediate invention are shown in Figures 1B, 1C and 1D. In these figures, the sequence of fractional distillation columns is changed or certain columns are removed. Such permutations of the column sequence are common in the industry, known to those skilled in the art as "first deethanizer", "first depropanizer", etc., which refers to the initial distillation operation performed on the total sequence, and chosen based on capital and energy optimizations associated with the specific type of charge gas produced in the olefin preparation / generation stage (0). Despite the sequence of the columns, the impact of the present invention is the same. In a preferred embodiment, the demethanizer column is operated with a condenser temperature above about -48.^°C (-55^°F), and an ethylene-rich by-product is obtained as an overhead product, which allows the subsequent production of an ethylene-rich primary product without the use of a substantially dedicated cooling system, lean oil circulation, or a cooling train. .

In addition, additional embodiments of the present invention are shown in Figure 2. This figure represents a modification of Figure 1A, in which various pieces of equipment known to those skilled in the art are shown in dot lines, intermixed in logical parts of the procedure. recovery and total separation specified in this invention. An article of a particular signal is a non-distillative, non-cryogenic bulk separation procedure (21) installed at some point in the procedure before the demethanizer, which serves to remove a portion of the low-boiling components in the charge gas as stream (22), which leaves a stream reduced in lower boiling point components than ethylene as feed (23) to the demethanizer column. Some volume separation articles are well known to the industry, including commercial applications such as hollow fiber membranes offered by MEDAL Limited Partnership as described by Fleming and Dupuis in their articles Hydrogen Membrane Recovery Estimates, or chemical absorption technique called "Selective Olefin Recovery ”noted above. Another technique is a reactive removal of hydrogen and carbon monoxide as described in the attorney's certificate for US Patent Application number 96B082, to Ou, et. to the. By modifying the ratio of low-boiling components to ethylene in the feed to the demethanizer in the immediate invention, one can modify the ratio and composition of the ethylene-rich product side stream according to the information provided in Table 2. In addition, one can use such techniques in the ethylene-rich product side stream to reduce the amount of low-boiling components contained therein (24), potentially increasing its cost-effective value to a derived unit, and providing a rich stream. in lower boiling point components than ethylene, which can be profitable in its own good.

In addition, in Figure 2, a multitude of equipment may be present to serve a variety of uses. One such article (25) performs a reactive conversion of acetylene to ethylene and ethane in the presence of hydrogen, known to those skilled in the art as an acetylene converter. Such a technique would eliminate the presence of acetylene in both the primary ethylene-rich product stream and the secondary stream, or both, depending on where the separation and total recovery process is located.

Following the method of this invention, such auxiliary equipment of the type and use observed in the description of Figure 2 can be located in any logical place in the separation and recovery procedure.

ES 2 186 014 T3 total ratio, for any sequence of the fractional distillation columns, and the benefits of using the immediate invention are still achieved, and therefore are included within the scope of the immediate invention. This includes the use of compression stages normally found in the olefin preparation / generation process, but sometimes placed between columns in various overhead product streams to optimize between the compression energy requirements and piping necessary to move the streams together. to around various teams, and the pumps used to move the streams alongside various equipment or modify the pressure of the streams to and from the equipment. In addition, in still useful but less preferred embodiments, a cooling train, lean oil, or temperatures below about -48 may be employed.^°C (-55^°F), but at temperatures above those normally used in conventional wisdom, or the demethanizer can function to retain appreciable amounts of components of a boiling point at least as low as ethylene, which saves varying amounts of energy and capital while providing additional flexibility by controlling the ratio of the ethylene product side stream to the desired requirements for the ethylene rich primary product stream.

The invention is illustrated but not limited by the examples that follow. In each of the following examples, a feed rate of 45,360 kg / h (100,000 lb / h) of ethylene contained in the charge gas from an olefin preparation / generation process (0) is assumed. The amount of other components is defined by the composition of the total stream listed in each example.

Example 1

First demethanizer in unadulterated charge gas

Related to Figure 1, an olefin preparation / generation procedure (0) Methanol to Olefins, creates an olefin carrier charge gas mixed (1) with a composition reflected by that given in Table 1 that has all the carbon dioxide. carbon and carbon removed, as shown in Table 3, and a pressure of 4,205 kPa (610 psia) and a temperature of 32^°C (90^°F).

TABLE 3

Composition of mixed olefin carrier charge gas (1) for Example 1

<td>Component</td><td>% in weigh</td>

<td>H2</td><td> 0,03</td>

<td>CO</td><td> 0,50</td>

<td>ch₄</td><td> 1,49</td>

<td>C2H4</td><td> 55,18</td>

<td>C2H6</td><td> 1,72</td>

<td>C3 +</td><td> 41,08</td>

<td>Total</td><td> 100,00</td>

The charge gas is taken through the heat exchanger (3), where the heat is removed to provide the feed to the demethanizer (2) at a temperature of -18^°C (0^°F) and suffers a pressure drop of 55.16 kPa (8 psia). The demethanizer is operated, with the equivalent of 30 theoretical plates and the feeding in the eighth plate from the bottom, with a temperature in the drum (8) of -46^°C (-50^°F) and a pressure of 4,137 kPa (600 psia), with a thermal load of the pot and the condenser sufficient to provide an amount of propylene in the secondary product stream rich in ethylene (10) of 10 mol ppm. As obtained from Table 2, the amount and composition of the ethylene-rich side product stream would be approximately as shown in Table 4, which contains all of the hydrogen, carbon monoxide, and methane in the charge gas:

ES 2 186 014 T3

TABLE 4

Composition of the secondary product stream rich in ethylene (10) for Example 1

<td>Component</td><td>% Mol</td><td>Kg (Lb) -mol / h</td><td>% in weigh</td><td>Kg (Lb) / h</td>

<td>H2</td><td> 7,62</td><td> 12,3 (27,0)</td><td> 0,75</td><td> 24,5 (54)</td>

<td>CO</td><td> 9,14</td><td> 14,7 (32,4)</td><td> 12,59</td><td> 411 (906)</td>

<td>ch₄</td><td> 47,63</td><td> 76,6 (168,8)</td><td> 37,53</td><td> 1.224,7 (2.700)</td>

<td>C2H4</td><td> 35,27</td><td> 56,7 (125,00)</td><td> 48,64</td><td> 1.578,6 (3.500)</td>

<td>C2H6</td><td> 0,34</td><td> 0,5 (1,2)</td><td> 0,49</td><td> 15,9 (35)</td>

<td>C3 +</td><td> -</td><td> -</td><td> -</td><td>Clues</td>

<td>Total</td><td> 100,00</td><td> 160,8 (354,4)</td><td> 100,00</td><td> 3.263,7 (7.195)</td>

The bottom product stream from the demethanizer (15) is fed to the demethanizer column (16), which is supplied with enough trays, kettle load and condenser heat load to carry out a fractional distillation separation between ethane and propylene. , in which only 100 ppm by weight of propylene and practically all the input ethylene is contained in the overhead product (17), and it is contained in the bottom product (18) about 100 ppm by weight of ethane and all the input components of a higher boiling point.

The overhead product from the deethanizer (17) is sent to a C2 separator column (19), which is supplied with enough trays, pot thermal charge and condenser thermal charge to carry out a fractional distillation separation between ethylene and ethane in which the overhead product (20) contains practically all the input ethylene and only 500 molppm of ethane and practically no hydrogen, Carbon monoxide or methane initially present in the charge gas. Stream (20) constitutes the primary ethylene-rich product stream currently established by the industry as normal for commercial markets.

Example 2

First deethanizer to use volume separation prior to demethanization

Please refer to Figure 2. An Olefin Preparation / Generation Procedure Ethane vapor cracking (0) creates a mixed olefin carrier charge gas (1) with a composition reflected by the table 1 containing all carbon dioxide, carbon and most of C7 + molecules removed, as shown in Table 5, at a pressure of 2,758 kPa (400 psia) and a temperature of 32^°C (90^°F).

TABLE 5

Composition of the mixed olefin carrier charge gas (1) for Example 2

<td>Component</td><td>% in weigh</td>

<td>H2</td><td> 3,94</td>

<td>CO</td><td>Clues</td>

<td>ch₄</td><td> 3,83</td>

<td>C2H2</td><td> 0,43</td>

<td>C2H4</td><td> 53,14</td>

<td>C2H6</td><td> 35,09</td>

<td>C3 +</td><td> 3,57</td>

<td>Total</td><td> 100,00</td>

The load is introduced into the deethanizer column (16), which is supplied with enough plates,

ES 2 186 014 T3 thermal charge of the pilot tank and thermal charge of the condenser to carry out a separation by fractional distillation between ethane and propylene, in which only 100 ppm by weight of propylene was contained in the top product (17) and practically all the input ethylene, and is contained in the bottom product (18) around 100 ppm by weight of ethane and all the input components of a higher boiling point. The deethanizer column stage was introduced at a pressure drop of 68.95 kPa (10 psia), and the pressure of stream (17) is now 2689 kPa (390 psia).

The overhead product from the deethanizer is taken through a compressor (22) where the pressure is increased to 4,275 kPa (620 psia) at point (23), and is introduced into a commercial MEDAL hollow fiber membrane (24) designed and produced to effect a 60% removal of hydrogen to create a trapped stream (25), the composition of which is shown in Table 6, and whose pressure is now 3,241 kPa (470 psi). A stream (26) is also created as permeate, consisting of labeled hydrogen plus some diverted methane, acetylene, and ethylene removed from stream (23).

TABLE 6

Stream composition (25) from volume separation device (24) in Example 2

<td>Component</td><td>% in weigh</td><td>Kg (Lb) / h</td>

<td>H2</td><td> 1,69</td><td> 1.345 (2.966)</td>

<td>CO</td><td> -</td><td>Clues</td>

<td>ch₄</td><td> 3,95</td><td> 3.138,5 (6.919)</td>

<td>C2H2</td><td> 0,45</td><td> 359,7 (793)</td>

<td>C2H4</td><td> 56,45</td><td> 44.906,4 (99.000)</td>

<td>C2H6</td><td> 37,46</td><td> 29.802,9 (65.703)</td>

<td>C3 +</td><td> -</td><td>Clues</td>

<td>Total</td><td> 100,00</td><td> 79.442,8 (175.381)</td>

Stream (25) is introduced into an acetylene converter reactor (27), designed and produced to kill all acetylene with 70% converted to ethylene and 30% converted to ethane by a stoichiometric reaction with the hydrogen in the stream. . The result is a stream (28), which is taken through the heat exchanger (3), where the heat is removed to supply the demethanizer (2) at a temperature of -18^°C (0^°F), whose composition and proportion are given in Table

7.

TABLE 7

Composition of the feed of stream (4) to the demethanizer column in Example 2

<td>Component</td><td>% in weigh</td><td>Kg (Lb) / h</td>

<td>H2</td><td> 1,65</td><td> 1.309,5 (2.887)</td>

<td>CO</td><td> -</td><td>Clues</td>

<td>ch₄</td><td> 3,95</td><td> 3.138,5 (6.919)</td>

<td>C2H2</td><td> -</td><td> 0</td>

<td>C2H4</td><td> 56,79</td><td> 45.177,7 (99.598)</td>

<td>C2H6</td><td> 37,61</td><td> 29.927,2 (65.977)</td>

<td>C3 +</td><td> -</td><td>Clues</td>

<td>Total</td><td> 100,00</td><td> 79.552,8 (175.381)</td>

Through items (27) and (3), it suffers a pressure drop of 124.11 kPa (18 psi). The demethanizer, with the equivalent of 20 theoretical plates and fed into the eighth plate from the bottom, is operated with a temperature of the condenser in the drum (8) of -37^°C

ES 2 186 014 T3 (-35 ° F) and a pressure of 3,102.75 kPa (450 psia), with a thermal load of the pot and condenser sufficient to provide a quantity of methane in the bottom product stream of the demethanizer ( 15) of 135 mol ppm. In this case, due to the relatively high ratio of ethane to ethylene in the feed to the demethanizer, ethane is left in the side stream of ethylene-rich product (10) as an optimal potential among the cooling requirements in the condenser (6). and the recovery of ethylene in the bottom product stream (15) for subsequent manufacture of the ethylene-rich primary product stream. Thus, as previously discussed, the rate and proportion of ethylene in the secondary product stream rich in ethylene (10) will be somewhat lower than those predicted in Table 2, while still containing all the hydrogen, carbon monoxide and methane in the charge gas, as shown in Table 8.

TABLE 8

Composition of the secondary product stream rich in ethylene (10) for Example 2

<td>Component</td><td>% Mol.</td><td>Kg (Lb) -mol / h</td><td>% in weigh</td><td>Lb (Kg) / h</td>

<td>H2</td><td> 34,45</td><td> 654,8 (1.443,5)</td><td> 3,84</td><td> 1.390,5 (2.887)</td>

<td>CO</td><td>Clues</td><td>Clues</td><td>Clues</td><td>Clues</td>

<td>ch₄</td><td> 10,31</td><td> 196 (432,0)</td><td> 9,19</td><td> 3.135,3 (6.912)</td>

<td>C2H4</td><td> 47,85</td><td> 909,5 (2.005,0)</td><td> 74,63</td><td> 25.465,1 (56.140)</td>

<td>C2H6</td><td> 7,39</td><td> 140,3 (309,4)</td><td> 12,34</td><td> 4.210,8 (9.283)</td>

<td>C3 +</td><td> -</td><td> -</td><td> -</td><td> -</td>

<td>Total</td><td> 100,0</td><td> 1.900,5 (4.189,9)</td><td> 100,0</td><td> 34.120,7 (75.222)</td>

The bottom product stream from the demethanizer (15) is sent to separator column C2, which is supplied with enough trays, kettle heat and condenser heat load to carry out a fractional distillation separation between ethylene and ethane, in the one that was contained in the top product (20), practically all the input ethylene and only 500 molppm of ethane and practically no hydrogen, Carbon monoxide or methane initially present in the charge gas. Stream (20) constitutes the primary ethylene-rich product stream currently established by the industry as normal for commercial markets.

As one can see from these examples, the advantages of the present invention include that they are capable of achieving the same results, with substantially less capital equipment.

The invention has been described with reference to its preferred embodiments. In view of this description, one skilled in the art will appreciate changes and modifications that can be made that do not depart from the scope and spirit of the invention as described above and claimed in the future.