WO2009038472A1

WO2009038472A1 - Method and system for absorption of selective specific gaseous compounds from a fluid in a microchannel module, and screening of the absorbent mixture

Info

Publication number: WO2009038472A1
Application number: PCT/NO2008/000334
Authority: WO
Inventors: Bernd Wittgens; Paal Skjetne
Original assignee: Sinvent AS
Current assignee: Sinvent AS
Priority date: 2007-09-17
Filing date: 2008-09-17
Publication date: 2009-03-26
Anticipated expiration: 2010-03-17
Also published as: NO20074747L

Abstract

The present invention comprises a method and system for rapid screening, characterization and optimization of absorbent mixtures for selective removal of specific gaseous compounds from a fluid flow, said fluid flow and absorbent mixture being conveyed to a modular microchannel system wherein fluid and absorbent mixture are mixed in at least one microchannel structure residence time module for optimized mass transfer from fluid to absorbent mixture mixture at a temperature in the range from -40°C to 450°C, and a pressure in the range from 0,1 bar(a) to 900 bar(g), temperature and pressure being controlled by means of a process control, a safety system and analysis system for systematic and continuous screening and characterization of said absorbent mixture. The present invention also comprises use of the above mentioned method.

Description

Screening of an absorbent mixture and system thereof

The present invention comprises a method and system for selective removal of specific gaseous compounds from a fluid flow and use thereof.

Background

In the field of gas processing, absorbent mixtures are frequently used for the removal of gaseous compounds from the bulk gas mixture. Absorption processes are regularly used in oil and gas processing and chemical industries. Typical examples are the removal of sour or aqueous components in natural gas or the removal of carbon dioxide and acidic components from flue gas of combustion processes.

It is expected that the costs of an absorption process and the environmental effects of the utilized chemicals will be more relevant in the near future. Some common absorbents for the removal of H₂S and CO₂ from natural gas have an environmentally adverse effect. For the exploration of gas fields in arctic environment or for large scale removal of CO₂ from fossil fuel fired power plants, more efficient and environmentally acceptable absorption mixtures have to be developed and thoroughly tested. Today, the selection, characterization of absorbents and the evaluation of operation conditions is time consuming and performed batchwise in laboratory equipment at moderate temperature and pressure. Especially absorbent mixtures for natural gas processing are not yet regularly characterized at operation pressure or temperature. Those systems are investigated at moderate temperature and pressure, their performance at given operation conditions are estimated based on numerical models.

Concerning prior art reference should also be made to Hessel, V. et al. "Gas/liquid microreactors for direct fluorination of aromatic compounds using elemental fluorine" in Ehrfeld, W. (Ed.) Microreaction Technology: 3^th International Conference on Microreaction Technology, Proceedings of IMRET 3, pp.526-540, Springer- Verlag, Berlin, (2000). Further, reference should also be made to Hessel, V. et al. "Gas/liquid microreactors: hydrodynamics and mass transfer", in Proceedings of the 4^th International Conference on Microreaction Technology, Proceedings of IMRET 4, 5-9 March, 2000, pp.174-186, Atlanta, USA. Concerning prior art rereference is also made to DE 10 2004 007 527 Al.

Traditionally, gas has been conveyed to containers with stirring equipment, the gas is recycled between individual containers for some time to ensure establishing of equilibrium between gas and liquid phase. One of the problems with said batch experiment is to know when equilibrium between the phases is established. Since there is little information concerning the conveyance from the gas to the liquid phase and knowledge to the reaction kinetic is insufficient, the stirring in the container continues for a long time to ensure that equilibrium is established.

Objective of the invention

The present invention is conceived to solve or at least alleviate the problems identified above. Specially, an object of the invention is to provide a method for optimization of the selection of absorbents for removal of specific gaseous compounds from a fluid flow. More specifically, characterisation of absorbent mixtures for natural gas processing at operation pressure and temperature or processing of flue gas from fossil fuel fired processes is performed according to the present invention. Mass transfer between fluid phases to achieve equilibrium between said phases is intensified by means of microchannel structures. Performing the optimization and characterization of absorbents in said apparatus with said procedure reduces the time and amount of chemicals spend.

Description of the invention

The objective of the invention may be obtained by the features as set forth in the following description of the invention.

The present invention comprises a method for selective removal of specific gaseous compounds from a fluid flow by means of an absorbent mixture, said fluid flow and absorbent mixture being conveyed to a modular microchannel system wherein fluid and absorbent mixture are mixed in at least one microchannel structure residence time module for optimized mass transfer from fluid to absorbent mixture at a temperature in the range from -40°C to 450⁰C, and a pressure in the range from 0,1 bar(a) to 900 bar(g), temperature and pressure being controlled by means of a a process control, a safety system and an analysis system for the systematic and continuous screening and characterization of said absorbent mixture.

The method includes that said absorbent mixture is dragged by the fluid flow along microchannel structures. Further, said fluid flow is dragged by the absorbent mixture along microchannel structures. Fluid flow and absorbent mixture are present in the ratio of 500: 1 to 1:500 (ratio gas: liquid) in said microchannel structure .

The present invention also comprises a system for selective removal of at least one specific gaseous compound from a fluid flow by means of an absorbent mixture, said system comprising a mass transfer assembly combined with a process control, safety system and an analysis system, in which said mass transfer assembly comprises at least one microchannel structure residence time module. Said mass transfer assembly comprises at least one microchannel absorbent mixture and fluid supply, at least one microchannel mixer module and at least one microchannel gas-liquid separator. At least two modular microchannel modules of the present system can be arranged in parallel or series. Further, at least one modular microchannel module is arranged in series and at least two modular microchannel modules are added in parallel, hi the present invention at least two modular microchannel modules are arranged in parallel and at least one modular microchannel module is added in series. At least two modular microchannel modules are arranged in parallel and at least two modular microchannel modules are added in parallel.

Use of a system for systematic and continuous screening and characterization of an absorbent mixture is also described by the present invention in which said system comprises a modular microchannel system as described in the previous, said modular microchannel system comprises at least one microchannel structure residence time module, at least one absorbent mixture and fluid supply, at least one gas and liquid mixer module and at least one gas-liquid separator. The present invention can be used in cryogenic absorption, desorption or gas-liquid reactions in the temperature range from -40 to 0 °C or for sweetening of natural gas in the temperature range from 0 to 30°C or from 30 to 150°C. Further said invention can be used for removal of acidic components from exhaust and flue gas in which the temperature is > 150 °C, from 20-200 °C or > 200 ⁰C. Acidic components can be removed from high temperature gas mixtures according to the present invention at temperatures below 450 °C

In the present invention operation conditions as e.g.: temperature, pressure, fluid (liquid and gas) flow rates, but not limited to these, can be varied independent of each other within the specified ranges. Examples of pressure ranges (in bar) are as follow: 0,1-20, 20-30, 30- 700, 40-500, 50-500, 60-400, 70-300, 80-200, 90-100, 20-350, 100-200, 200-300, 300-400, 400-500, 500-600, 600-700, 700-800, 800-900. Examples of temperature ranges according to the present invention are as follow: -30 - 0; 0 - 30; 30 - 80; 60 - 120; 80 - 140; 120 - 45O⁰C .

The present invention comprises a comprehensive method and system for the rapid, systematic and effective screening of absorbent chemicals and their mixtures for selective removal of individual gaseous compounds from a fluid flow subjected to a given pressure and temperature. The object of the present invention is to obtain a method and system for characterization and optimization of absorption chemicals and process conditions for absorption and desorption processes, e.g. sweetening of natural gas or capture of acidic components such as e.g. CO₂, SO₂, H₂S from exhaust and flue gases but not limited to these components. Characterization according to the present invention describes the reaction kinetics and equilibrium data of a given combination of gas (both matrix and impurities) and absorbent liquid for a given set of operation conditions. Operations conditions are temperature, pressure and composition of fluid phases. The present invention comprises a modular designed microchannel system for the intensive mixing of a fluid flow and absorbent mixture (gas and liquid phase) for an optimized mass transfer from fluid to absorbent mixture (gas to liquid phase), interchangeable microchannel structure residence time modules, separation module, data collection and analysis equipment. The system will be under close control of gas and liquid flow as well as temperature (max. range -40 to 450⁰C) and pressure (max. range 0.1 bar(a) - 900 bar(g)), the composition of gas and liquid phase will be analysed frequently. Analysis will give information on the reaction rate and equilibrium data. Reaction rate and equilibrium data will be used in the design and optimization process of commercial absorption units. MicroChannel devices offer many economical, safety and technical advantages over conventional technologies in chemical processing. The overall objective of a microchannel system is to achieve high throughput per unit reactor volume by means of devices with high contact area to volume ratios, micro-scale film thickness and a uniform flow distribution. The design of these units facilitates improvement in heat and mass transfer rates which in turn improve efficiency of the device. Efficiency is defined as the time required performing a systematic evaluation of a given absorbent type or mixture at different gas composition or operation conditions as temperature and pressure.

The object of the present invention is a comprehensive system for effective characterization of absorption chemicals. Improvements of the apparatus compared to traditional batch systems are:

1.) Measuring time: a. Time required for testing and analyzing of a given absorbent mixture at different operation conditions can be considerably reduced because of continuous operation of the present intervention in combination with an integrated process control system b. Time required for screening and analyzing of absorbent mixtures can be considerably reduced by means of improving the mass transfer between fluid phases such that time to approach equilibrium is reduced

2.) Analysis: online analysis of the gas and liquid composition for evaluation of reaction rate and equilibrium for determination of the optimum operation conditions and absorbent mixtures

3.) Flexibility: Operation of the system over a wide range of operation conditions 4.) Operation: Simple and easy to use system were changeover from one experiment to the other is easily facilitated by means of the integrated process control system 5.) Minimized consumption of chemicals, because of reduced time and miniaturized dimensions of the apparatus

6.) Minimized health, environmental and safety issues due to the miniaturization of the process equipment the amount of contained chemicals is reduced, for high pressure applications will a miniaturized system vastly reduce consequences of a possible breakdown. Embodiments of the invention will now be described with reference to the following drawings, where:

Figure 1 shows a flowsheet and possible design of the present invention. Figure 1 comprises the following devices: fluid and absorbent mixture supply including flow, temperature and pressure control - microchannel gas and liquid contactor/mixer module microchannel structure residence time module - microchannel gas/ liquid separator analysis system process control and safety system

in which: FT = Flow Transmitter

PCV = Pressure Control Valve PSV = Pressure Safety Valve PT = Pressure Transmitter TT = Temperature transmitter

The gas/liquid contactor might be T-mixer or cyclone-mixer (but not limited to these principles) with individual opposing/perpentdicular or radial inlets for gas and liquid. Inside the cyclone-mixer the fluids are divided into thin layers and subsequently superimposed such that an intense mass transfer is ensured, for a schematic, see figure 2. Figure 2 shows the principle of a cyclone mixer, for simplicity, only four gas and liquid streams into the mixing chamber are presented.

Dependent on the loading of gas and liquid, a flow pattern varying from stratified, stratified wavy, wavy, bubbly, slug, slug-annular, annular or churn is generated.

The generated two phase fluid flow, entering the microchannel structure residence time module, see figure 3, will be conveyed through microchannels in which mass transfer between gas and liquid phase proceeds. The gas/liquid mixture will be transported through the residence time module because of a pressure gradient between inlet and outlet, the faster moving fluid will disperse the other phase, friction forces between phases (drag) ensures transport through the device.

The configuration (serial or parallel), number, length and dimensions of the microchannel structureresidence time modules depend on the type of absorption system to be investigated. The time scale necessary for approach to equilibrium or conclusion of a reaction determines configuration and length/dimension of the residence time module. For applications were long residence times are required to approach equilibrium or conclude the reaction, meandering channels in the residence time module are applied to minimize the footprint of the arrangement. Multiple residence time modules with channel structures can be stacked side-by-side (parallel) or on-top of each other (serial) or in a combination of these two basic configurations.

From figure 4 it can be seen that the liquid gas mixture is entering a gas/liquid separator where the two-phase flow is split into a gas and liquid phase. Possible separation devices are metallic sinter inlay or a hydro cyclone, but not limited to these designs. Said phases are subjected to analysis to determine the contents of both gaseous phase and liquid phase. Analysis concerns the concentration in the individual phases, reaction products in gas and liquid phase.

The operation conditions in the invention are variable during an experiment because of the installed control system, adjustment of gas and liquid flow, temperature and pressure is facilitated by means of online controlled valves, pumps and heating elements. Experiments to determine operation conditions can therefore be performed automated without operator intervention.

Having described preferred embodiments of the invention it will be apparent to those skilled in the art that other embodiments incorporating the concepts may be used. These and other examples of the invention illustrated above are intended by way of example only and the actual scope of the invention is to be determined from the following claims.

Claims

C l a i m s

1. Method for selective removal of specific gaseous compounds from a fluid flow by means of a selected absorbent mixture, said fluid flow and absorbent mixture being conveyed to a modular microchannel system wherein fluid and absorbent mixture are mixed in at least one microchannel structure residence time module for optimized mass transfer from fluid to absorbent mixture at a temperature in the range from -40°C to 450°C, and a pressure in the range from 0,1 bar(a) to 900 bar(g), temperature and pressure being controlled by means of a process control, and a safety system, and further systematic and continuous screening and characterization of said absorbent mixture by means of an analysis system.

2. Method according to claim 1, wherein said absorbent mixture is dragged by the fluid flow along microchannel structure.

3. Method according to claim 1, wherein said fluid flow is dragged by the absorbent mixture along microchannel structures.

4. Method according to claim 1, wherein fluid flow and absorbent mixture are present in the ratio gas: liquid of 500:1 to 1:500 in said microchannel structure residence time module.

5. System for selective removal of at least one specific gaseous compound from a fluid flow by means of a selected absorbent mixture, said system comprising a mass transfer assembly combined with a process control, a safety system and an analysis system, in which said mass transfer assembly comprises at least one microchannel structure residence time module.

6. System according to claim 5, wherein said mass transfer assembly comprises at least one microchannel absorbent mixture- and fluid supply.

7. System according to claim 5, wherein said mass transfer assembly comprises at least one microchannel mixer module.

8. System according to claim 5, wherein said mass transfer assembly comprises at least one microchannel gas-liquid separator.

9. System according to claim 5, wherein at least two modular microchannel modules are arranged in parallel.

10. System according to claim 5, wherein at least two modular microchannel modules are arranged in series.

11. System according to claim 5, wherein at least one modular microchannel modules is arranged in series and at least two modular microchannel modules are added in parallel.

12. System according to claim 5, wherein at least two modular microchannel modules are arranged in parallel and at least one modular microchannel module is added in series.

13. System according to claim 5, wherein at least two modular microchannel modules are arranged in parallel and at least two modular microchannel modules are added in parallel.

14. Use of a system for systematic and continuous screening and characterization of an absorbent mixture comprising a modular microchannel system according to claim 1, said modular microchannel system comprises at least one structure residence time module.

15. Use according to claim 14, said modular microchannel system comprises at least one absorbent mixture- and fluid supply.

16. Use according to claim 14, said modular microchannel system comprises at least one gas and liquid mixer module.

17. Use according to claim 14, said modular microchannel system comprises at least one gas-liquid separator.

18. Use according to claim 14, for cryogenic absorption, desorption or gas-liquid reactions in the temperature range from -40 to 0 °C.

19. Use according to claim 14, for sweetening of natural gas.

20. Use according to claim 19, in the temperature range from 0 to 30°C.

21. Use according to claim 19, in the temperature range from 30 to 150°C.

22. Use according to claim 14, for removal of CO2 from flue gas.

23. Use according to claim 14, for removal of acidic components from exhaust and flue gas in which the temperature is from 20-200 °C.

24. Use according to claim 14, for removal of acidic components from high temperature gas mixtures in which the temperature is less than 450°C.