MX2008001816A - Method for enabling the provision of purified carbon dioxide - Google Patents

Abstract

The invention provides a method for enabling the provision of purified carbon dioxide for direct use in operations requiring purified carbon dioxide, the method comprising passing impure carbon dioxide through various purification units for the removal of sulfur compounds, oxygenates, and aromatics. The present invention provides for a carbon dioxide supply systems, method and apparatus for purifying carbon dioxide and method for providing backup carbon dioxide. Sulfur species and other impurities are removed from the carbon dioxide by adsorption and reaction means.

Description

METHOD FOR ENABLING THE PROVISION OF PURIFIED CARBON DIOXIDE FIELD OF THE INVENTION The present invention provides a method for disposing of gases. In particular, this invention is directed to a method for enabling the disposition of purified carbon dioxide gases.

BACKGROUND OF THE INVENTION Carbon dioxide is used in various industrial and domestic applications, many of which require that carbon dioxide be free of different impurities. Unfortunately, the carbon dioxide obtained from natural sources such as gas wells, chemical processes, fermentation processes or produced in the industry, particularly the carbon dioxide produced by the combustion of hydrocarbon products, often contains levels of carbon dioxide. impurity of sulfur compounds, such as carbonyl sulfide (COS) and hydrogen sulfide (H2S) as well as oxygenates such as acetaldehydes and alcohols as well as aromatics such as benzene, when carbon dioxide is intended for use in an application that requires that carbon dioxide be of high purity, such as in the manufacture and cleaning of food products and carbonation of beverages, medical products and electronic devices, the sulfur compounds and other hydrocarbon impurities contained in the gas stream must be eliminated very low levels before use. The level of impurity removal required varies according to the application of carbon dioxide. For example, for beverage applications, the total sulfur level in carbon dioxide (C02) should theoretically be below 0.1 ppm, and aromatic hydrocarbons need to be below 0.02 ppm. For electronic cleaning applications, heavy hydrocarbon removal is required below 0.1 ppm.

Various methods are known for removing sulfur compounds and hydrocarbon impurities from gases such as carbon dioxide. For example, US Patent No. 4,332,781, issued to Lieder et al., Describes the removal of COS and H2S from a gas stream by first removing the H2S from the hydrocarbon gas stream by contacting the gas stream with an aqueous solution. of a regenerable oxidizing reagent, which may be a polyvalent metal ion, such as iron, vanadium, copper, etc., to produce a gas stream containing COS and an aqueous mixture containing sulfur and the reduced reactant.

US Patent Nos. 5,858,068 and 6,099,619 disclose the use of a faujasite with silver exchange and an MFI type molecular sieve for the removal of sulfur, oxygen and other impurities from carbon dioxide intended for food-related use. US Patent No. 5,674,463 describes the use of hydrolysis and reaction with metal oxides such as ferric oxide for the removal of carbonyl sulphide and impurities of hydrogen sulfide from carbon dioxide.

It is known to directly remove sulfur compounds, such as H2S, from a gaseous stream, by contacting the gas stream with metal oxides such as copper oxide, zinc oxide or mixtures of these. It is also known to remove sulfur impurities such as COS by first hydrolyzing COS to H2S on a hydrolysis catalyst and then removing H2S by reaction with metal oxides.

Since many of the carbon dioxide end-users require that the carbon dioxide they use be virtually free of sulfur, hydrocarbon and other impurities, and because natural sources of carbon dioxide and carbon dioxide are Manufacturing in the industry often contains sulfur and hydrocarbon compounds, economic and efficient methods are continuously sought for practically complete elimination of sulfur and hydrocarbon compounds from gaseous carbon dioxide streams without concomitantly introducing other impurities into carbon dioxide . We also look for lower cost analysis methods for the different impurities. In addition, reliable methods are sought to provide high purity carbon dioxide for manufacturing operations. The present invention provides a simple and efficient method to achieve these objectives.

COMPENDIUM OF THE INVENTION In one embodiment, this invention provides a method for enabling the arrangement of purified gas, such as carbon dioxide, to direct use in operations that require purified gas such as carbon dioxide, the method is to send carbon dioxide from a production facility to a place where purified carbon dioxide is to be used, pass carbon dioxide through different purification units for the removal of impurities, such as sulfur, oxygenates and aromatics, analyze the impurities of the purified carbon dioxide using minus one analyzer, and move to operations a part of the purified carbon dioxide that meets the purity specification of the product.

In one embodiment, the method herein provides the direct user with use in a remote location. In addition, at least a part of the purified carbon dioxide can be used for reserve storage.

The method of the present is to supply carbon dioxide from a production plant, pass carbon dioxide through different units for the elimination of impurities such as sulfur and hydrocarbons including oxygenates, and aromatics, providing analytical means to guarantee the purity of carbon dioxide and supply purified carbon dioxide for manufacturing operations. The method also consists of liquefying part of the purified carbon dioxide and storing it as a reserve.

The purity of carbon dioxide is sufficient to meet the needs of quality assurance. In one embodiment, carbon dioxide is analyzed using detectors and the impurities are concentrated before analysis. The operations in which the purified carbon dioxide is used are selected from the group consisting of the manufacture of food and beverage products, medical products and customers of electronic cleaning devices.

BRIEF DESCRIPTION OF THE DRAWINGS Although the specification concludes that the claims distinctly state the subject that the applicants consider to be their invention, the invention will be better understood when taken together with the accompanying drawing in which: Figure 1 is a diagram of the production and purification of carbon dioxide from a carbon dioxide purification plant.

DETAILED DESCRIPTION OF THE INVENTION The carbon dioxide that is normally produced for industrial operations has various impurities present. These impurities will often be a problem for multiple uses of carbon dioxide, but in the production of products intended for human consumption such as carbonated beverages, and in the manufacture of electronics, the purity of carbon dioxide is paramount and may affect the taste, quality and legal compliance of the finished product. In addition to purity, the reliability of the carbon dioxide supply is also a problem for manufacturing operations that are usually continuous or semi-continuous. The present invention provides a method for reliably providing high purity carbon dioxide to manufacturing operations. Various applications of point of use of carbon dioxide include a full plant of beverages, a food freezing plant, an electronic manufacturing plant and a source-type carbon dioxide dispenser.

One embodiment of the invention is shown in Figure 1. In Figure 1, liquid carbon dioxide is obtained from a C02 300 production plant located in the vicinity of facility 310 where C02 is used in manufacturing operations. . The installation 310 can be a full beverage plant or an electronic manufacturing plant. The carbon dioxide is sent to a storage tank 315, vaporized in the vaporizer 320 and a stream 325 is sent to the analysis system 400. If the current is within the predetermined specifications with respect to the impurities of the feed, this is sent to the mobile purification system 330. A part of the current leaving the mobile purification system 330 is taken as stream 335 and analyzed by the analysis system 400. If this is within the predetermined limits with respect to the impurities of the product, a greater part of this purified stream is sent to the manufacturing operation 355 as stream 350, and a smaller portion, 345, is sent for the liquefaction and reserve storage. If the current leaving the mobile system 330 is not within the predetermined specifications, it is vented as stream 340. The reserve stream 345 is liquefied in the cooler 360 and pumped to the storage tank 370 using a pump 365. When it needs the reserve carbon dioxide, for example when the current leaving the unit 330 is not within the specifications, a stream of C02 from the storage tank 370 is vaporized in the vaporizer 375, and a part of this current is taken as 380 current for analysis in unit 400. If this current is within the specification for impurities, it is sent to unit 355 for manufacturing operations.

The industries or customers where the present invention will have utility include, but are not limited to, the manufacture and cleaning of food products; the manufacture of electronics, electronic components and sub-assemblies; the cleaning of medical products; carbonation of soft drinks, beer and water; the coating of storage tanks and containers containing flammable liquids or powders; the coating of materials that degrade in the air, such as vegetable oil, spices and aromas.

The potentially impure carbon dioxide from the storage tank 315 can be obtained from any available source of carbon dioxide and can contain as impurities sulfur compounds such as carbonyl sulfide, hydrogen sulfide, dimethyl sulfide, sulfur dioxide and mercaptans, impurities of hydrocarbons such as aldehydes, alcohols, aromatics, propane, ethylene and other impurities such as water, carbon monoxide. These impurities are eliminated in the purification unit 330 and analyzed in the analyzer system 400. The purification unit contains various modules for the removal of the impurities of sulfur, hydrocarbons, oxygenates and aromatics.

For the purpose of this invention, at least some of the sulfur impurities, such as hydrogen sulfide and carbonyl sulfide can be removed at an elevated temperature, a temperature of 50 to 150 ° C. These temperatures can be obtained by means of the heater and heat exchange means. The elimination of sulfur impurities at these temperatures significantly improves the efficiency of the removal of these impurities. Sulfur purification materials include carbonates and hydroxides such as hydroxides or carbonates of sodium and potassium on activated carbon; metal oxides such as copper oxide, zinc, chromium or iron alone or with support on the microporous adsorbent such as activated alumina, activated carbon or silica gel. Other materials such as zeolite CuY are effective for the removal of impurities carbonyl sulfide and sulfur dioxide by reaction. Activated carbon can also be used for the elimination of mercaptans. Some of the materials, and hydroxides and carbonates, may require oxygen to convert the sulfur compounds such as hydrogen sulfide into sulfur and oxygen and water to convert carbonyl sulfide into hydrogen sulfide and then into sulfur.

The hydrocarbon impurities are removed by a combination of catalytic oxidation and adsorption or by adsorption alone. The catalyst bed will be after the sulfur scavenger bed. The temperature of the current needs to be raised to a temperature between 150 ° and 450 ° C for the oxidation of the different hydrocarbon impurities by the heater and heat exchange means. The temperature of the reactor depends on the impurity that has to be eliminated, as well as the catalyst that is used. The materials used in the catalytic reactor are usually noble metals such as platinum or palladium on a particulate or monolithic support. The reactor bed purifies the carbon dioxide by oxidation reactions and oxygen is added before the catalyst bed in an appropriate amount. Common impurities removed in the reactor include propane, aldehydes, alcohols, acetates, aromatics, methane, ethane and carbon monoxide.

The current leaving the reactor beds or the beds for the removal of sulfur is cooled to almost ambient temperatures in the heat exchange media and sent to the bed or adsorbent beds for the removal of water and other impurities. The adsorption bed can remove any residual impurities and the reaction products of the catalyst bed as well as water and most of the impurities when the catalyst bed is not used. Usually, for the removal of moisture an adsorbent such as activated alumina (AA), a zeolite, such as 4A or 3X or silica gel will be used. Other adsorbents such as a NaY zeolite or its compound forms (mixed with other adsorbents such as activated alumina) can be used for the removal of impurities such as aldehydes, alcohols such as methanol and ethanol, acetates such as methyl and ethyl acetates and some of the trace sulfur compounds such as dimethyl sulfide compound. For these impurities, the Y zeolites have much greater capacity than other zeolites and non-zeolitic materials. For aromatics such as benzene and toluene, it is possible to use adsorbents such as activated carbon or dealuminated Y zeolite.

For the purpose of this invention, various impurities in different process steps are analyzed by a sulfur analyzer and a hydrocarbon analyzer. These two analyzers can be in a single unit, such as a gas chromatograph, or they can be in different units. Before the analysis, the different impurities of sulfur and hydrocarbon can be concentrated or increase their amounts in the sample. This step improves the detection limits for the various analyzers.

For the use of carbon dioxide in the filling of beverages or the manufacture of electronics, the carbon dioxide flow rates can range from 80 to 1,500 standard m3 / h (standard cubic meter per hour) depending on the final application and the size of the production facility. The carbon dioxide will usually be at a pressure in the range of about 1.7 to about 21.5 bar, about 16 to about 20 bar being common. In certain applications, particularly those related to carbon dioxide for electronics cleaning, pressures may range from 60 to several hundred bar.

The processes of the present invention are designed to solve problems with carbon dioxide impurities, particularly with carbon dioxide supplied at the point of use in the manufacturers process. By purification and analysis at the same time, the operator of the production facility can depend on a stable supply of purified carbon dioxide of guaranteed quality while the invention can also supply a reserve storage tank with purified carbon dioxide for be used in any given situation where the real-time supply of purified carbon dioxide is not sufficient or available to meet the demand. This allows the operator greater operational control over the purification process because the operator can stop or pause the purification process if the impurity levels are not satisfactory for the different impurities of the carbon dioxide.

Example 1 A test was made using a mobile purification system similar to that described in Figure 1 to purify carbon dioxide. The mobile purification system contained modules for the elimination of sulfur, a catalytic oxidation unit and an adsorbent bed for the elimination of water and the remaining impurities. The conditions of the carbon dioxide feed were as follows: Pressure 17 bar Temperature 25 ° C Flow rate 109.7 m3 standard / h H2S '5 to 9 ppm COS 5 ppm Benzene 2.5 ppm Methanol 160 ppm Acetaldehyde 11 ppm Oxygen Approximately 50 ppm above the amount needed for the removal of H2S, COS, benzene , acetaldehyde and methanol The sulfur reactor bed was operated at a temperature of 100 ° C and contained 17.1 kg of activated carbon impregnated with 20% potassium carbonate. The catalytic reactor bed was operated at 250 ° C and contained a catalyst coated with palladium.

The unit was operated for approximately one week and the product was analyzed using a gas chromatograph containing FID and FPD detectors and a sample concentrator. During the period of analysis, the total sulfur in the product leaving the sulfur eliminating bed 40 remained below 0.05 ppm and the benzene, methanol and acetaldehyde were all below the limit of detection of the instrument, less than 10 ppb each. . A sample concentrator based on adsorption allowed the increase in the concentration of hydrocarbon impurities by a factor of plus or minus 100 • significantly increasing the detection limits for these impurities.

Although the present invention has been described with reference to various embodiments and examples, numerous changes additions and omissions, as will be apparent to those skilled in the art, can be made without departing from the spirit and scope of the present invention.

Claims (21)

1. A method to enable the provision of purified carbon dioxide to direct the use in operations that require purified carbon dioxide, the method consists of: a) supplying carbon dioxide from a production facility to a place where carbon dioxide is used purified; b) passing carbon dioxide through different purification units for the removal of the impurities to produce purified carbon dioxide; c) analyzing the impurities of the purified carbon dioxide using at least one analyzer; and d) transfer to operations a part of the purified carbon dioxide that meets the purity specifications of the product.

2. The method as claimed in claim 1, characterized in that the direct use is in a remote location.

3. The method as claimed in claim 1, characterized in that a part of the purified carbon dioxide is provided as reserve storage.

4. The method as claimed in claim 1, further consists of analyzing the feed to guarantee the purity specifications.

5. The method as claimed in claim 1, characterized in that the impurities comprise sulfur compounds, and hydrocarbons including oxygenates and aromatics.

6. The method as claimed in claim 1, characterized in that the purity of carbon dioxide is sufficient to meet the needs of quality assurance.

7. The method as claimed in claim 1, characterized in that each of the operations is selected from the group consisting of manufacturing and cleaning of food products, medical products and customers of electronic devices.

8. The method as claimed in claim 1, characterized in that the purification units consist of a sulfur reactor bed.

9. The method as claimed in claim 8, characterized in that the sulfur bed contains a catalyst that reacts with H2S and COS.

10. The method as claimed in claim 8, characterized in that the catalyst is selected from the group consisting of carbonates and hydroxides, carbonates on activated carbon, carbonates on activated alumina, metal oxides, metal oxides supported on a microporous adsorbent and CuY zeolite.

11. The method as claimed in claim 1, characterized in that the purification units further comprises a particulate or monolithic reactor bed.

12. The method as claimed in claim 11, characterized in that the reactor bed contains one or more catalyst materials.

13. The method as claimed in claim 11, characterized in that the purification units further comprise beds containing activated alumina and 13X zeolite.

14. The method as claimed in claim 13, characterized in that the activated and 13X alumina are layered one on top of the other.

15. The method as claimed in claim 13, further consists of a NaY zeolite adsorbent.

16. The method as claimed in claim 9, further comprises the activated carbon adsorbent.

17. The method as claimed in claim 1, characterized in that the means for eliminating carbon dioxide consists of valve means for directing the carbon dioxide to a production or storage process or to both at the same time.

18. The method as claimed in claim 1, which consists of analyzing the purity of carbon dioxide using detectors and concentrating the impurities before analysis.

19. The method as claimed in claim 1, further consists of analytical means of sulfur and analytical means of hydrocarbons.

20. The method as claimed in claim 1, which operates at a pressure of about 1.7 to 21.5 bar.

21. The method as claimed in claim 1, wherein the purification units operate at temperatures from about 40 ° C to about 300 ° C.