A device and method for supercritical high efficiency extraction of caffeine from coffee beans

Abstract

The present application relates to the technical field of caffeine extraction, and particularly relates to a device and a method for supercritical high-efficiency extraction of caffeine in coffee beans; the device can optimize the internal structure of an extraction kettle, greatly prolong the effective travel of supercritical CO2 fluid in the kettle, improve the fluid utilization rate and the caffeine extraction efficiency, realize high-efficiency extraction of caffeine, improve the quality of caffeine coffee products, and improve the production economy and environmental protection; the device comprises a CO2 storage tank, a high-pressure pump, a heat exchanger, an extraction kettle, a separation kettle and a crystallization kettle; the CO2 storage tank is used for feeding supercritical CO2 into the extraction kettle; the high-pressure pump and the heat exchanger are used for adjusting the gas inlet pressure and the gas inlet temperature of CO2 into the extraction kettle; the extraction kettle is used for extraction of whole coffee beans; the separation kettle is used for separation of crude caffeine; the crystallization kettle is used for fine crystallization of crude caffeine; and the extraction kettle is provided with an "S"-shaped flow channel for prolonging the travel of coffee beans in the extraction kettle.

Description

Technical Field

[0001] This invention relates to the technical field of caffeine extraction, and in particular to an apparatus and method for supercritical high-efficiency extraction of caffeine from coffee beans. Background Technology

[0002] With the upgrading of the coffee consumption market, the market demand for decaffeinated coffee continues to grow. Supercritical CO2 extraction technology has become the mainstream technology for decaffeine removal from coffee beans due to its advantages such as being green and environmentally friendly, having no solvent residue, and protecting heat-sensitive components at low temperatures.

[0003] In existing supercritical CO2 extraction technologies for coffee beans, the core equipment is mostly a conventional cylindrical extraction vessel without internal components. Supercritical CO2 fluid is prone to channeling and short-circuiting within the vessel, resulting in a short effective stroke, insufficient contact with the coffee beans, and low mass transfer efficiency. This leads to low CO2 utilization, long extraction cycles, and insufficient caffeine extraction. Furthermore, existing technologies commonly employ coffee bean grinding to improve extraction efficiency. However, grinding severely damages the native cell structure and characteristic flavor compounds of the coffee beans, causing flavor loss and quality degradation in decaffeinated coffee. If the coffee beans are kept intact, conventional processes result in high caffeine diffusion resistance, with extraction rates typically below 70%, failing to meet the requirements of industrial mass production. In addition, existing pretreatment processes are not optimized for the dense cell wall structure of whole coffee beans, further limiting the caffeine extraction efficiency of whole coffee beans. Summary of the Invention

[0004] Technical problems to be solved To address the shortcomings of existing technologies, this invention provides an apparatus and method for supercritical high-efficiency extraction of caffeine from coffee beans, which optimizes the internal structure of the extraction vessel, significantly extends the effective travel of supercritical CO2 fluid within the vessel, improves fluid utilization and caffeine extraction efficiency, achieves high-efficiency caffeine extraction, enhances the quality of decaffeinated coffee products, and improves production economy and environmental friendliness. Technical solution

[0005] To achieve the above objectives, the present invention provides the following technical solution: a device for supercritical high-efficiency extraction of caffeine from coffee beans, comprising a CO2 storage tank, a high-pressure pump, a heat exchanger, an extraction vessel, a separation vessel, and a crystallization vessel. The CO2 storage tank is used to introduce supercritical CO2 into the extraction vessel. The high-pressure pump and heat exchanger are used to adjust the inlet pressure and inlet temperature of CO2 into the extraction vessel. The extraction vessel is used for extraction of whole coffee beans. The separation vessel is used for crude separation of caffeine. The crystallization vessel is used for refined crystallization of crude caffeine. The extraction vessel is provided with an "S"-shaped flow channel to extend the travel of coffee beans within the extraction vessel.

[0006] Preferably, the extraction vessel is a vertical vessel, and the extraction vessel is provided with multiple baffles arranged alternately vertically and horizontally. The baffles are semi-circular in structure, and their outer diameters are sealed to the inner wall of the extraction vessel. The adjacent and staggered baffles form an "S"-shaped flow channel that allows whole coffee beans to pass through. Furthermore, the main body of the extraction vessel is a vertical cylindrical pressure vessel made of food-grade stainless steel, which meets the pressure requirements of supercritical CO2 extraction and food safety production standards. The baffles are made of food-grade stainless steel and are fixedly and sealed to the inner wall of the extraction vessel.

[0007] Preferably, both the upper and lower ends of the extraction vessel are detachably fitted with sealing end caps. The upper sealing end cap of the extraction vessel is provided with a CO2 fluid outlet and a material inlet, while the lower sealing end cap of the extraction vessel is provided with a CO2 fluid inlet and a material outlet.

[0008] Preferably, the extraction vessel is provided with a sieve plate at both the bottom and the top. The sieve plate at the bottom of the extraction vessel is used to support whole coffee beans, and the sieve plate at the top of the extraction vessel is used to prevent whole coffee beans from escaping from the top of the extraction vessel. The aperture of the sieve plate is smaller than the particle size of the coffee beans. Furthermore, the two sets of sieve plates can be detachably installed at the top and bottom of the extraction vessel.

[0009] Preferably, it also includes a condenser and a circulation pump, wherein the condenser is used to condense the CO2 fluid, and the circulation pump is used to reintroduce the condensed CO2 fluid into the CO2 storage tank.

[0010] Preferably, the inner diameter of the extraction vessel is 200 mm, the width of the baffle is 140 mm, the vertical distance between two adjacent baffles is 50 mm, and the total height of all baffles in the extraction vessel is 1000 mm.

[0011] A method for supercritical high-efficiency extraction of caffeine from coffee beans, comprising the following steps: S1. Coffee bean pretreatment: Soak whole coffee beans in room temperature purified water for 7 hours; this allows the coffee beans to fully absorb water and swell, softening the cell walls and significantly reducing the diffusion resistance of caffeine. This, combined with the optimized extraction device, creates a synergistic effect, further improving the caffeine extraction efficiency of whole coffee beans. S2. Loading: Put the pre-treated whole coffee beans into the extraction vessel and fill them evenly in the "S" flow channel area formed by the baffles. The material filling height should be adapted to the baffle arrangement area to ensure that the fluid is in full contact with the material throughout the process. Seal the end cap of the extraction vessel. S3. Extraction in the extraction vessel: The extraction temperature of coffee beans in the extraction vessel is controlled at 35-40℃, and the extraction pressure is controlled at 28-32MPa; the CO2 flow rate is controlled at 100-200kg / h, and the dynamic extraction time is 3-4h; furthermore, this temperature and pressure ensure that CO2 is stably in a supercritical state, while avoiding the thermal destruction of heat-sensitive flavor substances; after being pressurized by a high-pressure pump and heated to a supercritical state by a heat exchanger, liquid CO2 enters the extraction vessel from the CO2 fluid inlet at the bottom of the extraction vessel, flows upward through the "S"-shaped flow channel formed by the baffle plate, and fully countercurrently contacts the whole coffee beans to selectively extract the caffeine from the coffee beans; S4. Analysis: Supercritical CO2 fluid rich in caffeine flows out from the CO2 fluid outlet at the top of the extraction vessel and enters the separation vessel for analysis; S5. Medium Circulation: The decomposed CO2 fluid is condensed by the condenser, pressurized by the circulation pump, and then returned to the CO2 storage tank; the entire process is recycled, with no solvent consumption or emission of toxic and harmful substances; S6. Coffee Bean Processing: After extraction, whole coffee beans are removed from the extraction vessel and dried at room temperature and in a well-ventilated environment to obtain decaffeinated coffee beans that retain their original shape and characteristic flavor. The remaining decaffeinated coffee beans can be directly used for subsequent coffee processing steps such as roasting and grinding. S7. Caffeine Refining: Crude caffeine can be recrystallized in a crystallizing vessel with distilled water and decolorized with activated carbon to obtain high-purity caffeine crystals; caffeine crystals can be used in the food, medicine and other fields.

[0012] Preferably, the caffeine separation and analysis parameters in S4 are as follows: after the supercritical CO2 fluid rich in caffeine enters the separation vessel, the pressure is reduced to 6-8 MPa and the temperature is increased to 45-50℃; the CO2 is converted from the supercritical state to the gaseous state, and the caffeine is precipitated due to the sharp decrease in solubility, thus obtaining crude caffeine; the gaseous CO2 is condensed and recycled.

[0013] Beneficial effects

[0014] Compared with the prior art, the present invention provides an apparatus and method for supercritical high-efficiency extraction of caffeine from coffee beans, which has the following beneficial effects: The apparatus and method for supercritical high-efficiency extraction of caffeine from coffee beans: (1) By using the “S”-shaped flow channel inside the extraction vessel, the core defects of traditional supercritical extraction vessels, such as short fluid travel and low mass transfer efficiency, can be solved. The internal structure of the extraction vessel is optimized, the effective travel of supercritical CO2 fluid inside the vessel is greatly extended, and the fluid utilization rate and caffeine extraction efficiency are improved.

[0015] (2) To resolve the contradiction between extraction efficiency and coffee bean flavor preservation in the industry, and to achieve efficient extraction of caffeine without breaking the coffee beans and fully preserving their original form and characteristic flavor substances, thereby improving the quality of low-decaffeinated coffee products.

[0016] (3) Optimize the special pretreatment process for whole coffee beans, soften the cell walls of coffee beans, reduce the resistance to caffeine diffusion, and form a synergistic effect with the optimized extraction device to further improve the caffeine extraction efficiency of whole coffee beans.

[0017] (4) Provide a supercritical extraction device and supporting process that is simple in structure, highly adaptable, green and low in consumption, and can be mass-produced industrially, taking into account both low-caffeine coffee bean production and high-purity caffeine extraction, and improving production economy and environmental protection. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the planar structure of the "S"-shaped flow channel inside the extraction vessel of the present invention; Figure 2 This is a schematic diagram of the planar structure of the first and second baffle plates in the upper part of the extraction vessel of the present invention; Figure 3 This is a schematic diagram of the process flow of the present invention; The following labels are used in the attached diagram: 1. CO2 storage tank; 2. High-pressure pump; 3. Heat exchanger; 4. Extraction vessel; 5. Separation vessel; 6. Crystallization vessel; 7. Baffle plate; 8. Condenser; 9. Circulation pump. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Please see Figures 1-3 The present invention discloses an apparatus for supercritical high-efficiency extraction of caffeine from coffee beans, comprising a CO2 storage tank 1, a high-pressure pump 2, a heat exchanger 3, an extraction vessel 4, a separation vessel 5, and a crystallization vessel 6. The CO2 storage tank 1 is used to introduce supercritical CO2 into the extraction vessel 4. The high-pressure pump 2 and the heat exchanger 3 are used to adjust the inlet pressure and inlet temperature of CO2 into the extraction vessel 4. The extraction vessel 4 is used for extraction of whole coffee beans, the separation vessel 5 is used for crude separation of caffeine, and the crystallization vessel 6 is used for refined crystallization of crude caffeine. The extraction vessel 4 is provided with an "S"-shaped flow channel to extend the travel of coffee beans within the extraction vessel 4.

[0021] For details, please refer to Figures 1-2The extraction vessel 4 is a vertical vessel, and inside the extraction vessel 4 are multiple baffles 7 arranged alternately vertically and horizontally. The baffles 7 have a semi-circular structure, and their outer diameter is sealed to the inner wall of the extraction vessel 4. The adjacent and staggered baffles 7 form an "S"-shaped flow channel that allows whole coffee beans to pass through. Furthermore, the main body of the extraction vessel 4 is a vertical cylindrical pressure vessel made of food-grade stainless steel, which meets the pressure requirements of supercritical CO2 extraction and food safety production standards. The baffles 7 are made of food-grade stainless steel and are fixedly and sealed to the inner wall of the extraction vessel 4.

[0022] To address the structural defects of traditional supercritical extraction vessel 4, the main body of extraction vessel 4 is innovatively optimized. The conventional cylindrical extraction vessel 4 is improved into a cylindrical structure with alternating baffles 7. The baffles 7 are mostly semi-circular and arranged in a vertically spaced, horizontally alternating manner, with a vertical spacing of 50mm between adjacent upper and lower baffles 7. This structure forces the supercritical CO2 fluid to form an "S"-shaped flow channel inside the vessel, significantly extending the effective travel of the fluid inside the vessel, avoiding channeling and short-circuiting problems, enhancing the mass transfer contact between the fluid and coffee beans, and significantly improving CO2 utilization and caffeine extraction efficiency.

[0023] Specifically, both the upper and lower ends of the extraction vessel 4 are detachably equipped with sealing end caps. The upper sealing end cap of the extraction vessel 4 is provided with a CO2 fluid outlet and a material inlet, while the lower sealing end cap of the extraction vessel 4 is provided with a CO2 fluid inlet and a material outlet. The pre-treated coffee beans are placed into the "S"-shaped flow channel inside the extraction vessel 4 through the material inlet, and the material outlet is used for the discharge of decaffeinated coffee beans after extraction.

[0024] Specifically, the extraction vessel 4 is equipped with sieve plates at both the bottom and top. The sieve plate at the bottom of the extraction vessel 4 is used to support whole coffee beans, and the sieve plate at the top of the extraction vessel 4 is used to prevent whole coffee beans from escaping from the top of the extraction vessel 4. The aperture of the sieve plates is smaller than the particle size of the coffee beans. Furthermore, the two sets of sieve plates can be detachably installed at the top and bottom of the extraction vessel 4. The sieve plates can confine the coffee beans within the "S"-shaped flow channel to ensure that the caffeine is in full contact with the supercritical CO2 fluid flowing through it.

[0025] Specifically, it also includes a condenser 8 and a circulation pump 9. The condenser 8 is used to condense the CO2 fluid, and the circulation pump 9 is used to reintroduce the condensed CO2 fluid into the CO2 storage tank 1. The desorbed CO2 fluid is condensed and returned to the CO2 storage tank 1 by the circulation pump 9. The whole process is recycled, with no solvent consumption and no emission of toxic and harmful substances.

[0026] Specifically, the inner diameter of the extraction vessel 4 is 200mm, the width of the baffle 7 is 140mm, the vertical distance between two adjacent baffles 7 is 50mm, and the total height of all baffles 7 inside the extraction vessel 4 is 1000mm.

[0027] A method for supercritical high-efficiency extraction of caffeine from coffee beans, wherein the coffee beans are extracted using the aforementioned supercritical high-efficiency extraction apparatus.

[0028] Example 1

[0029] Two kilograms of whole Arabica coffee beans were taken, sieved to remove foreign matter and bad beans, and soaked in purified water at room temperature for 7 hours without any crushing. The moisture content of the coffee beans was measured to be 52%. After draining the surface free water, the beans were placed into a 30L vertical cylindrical extraction vessel 4 with baffles 7 (the specific dimensions of the extraction vessel are described above). The extraction vessel 4 is equipped with alternating semi-circular baffles 7, with a vertical spacing of 50mm between adjacent upper and lower baffles 7. The material was evenly filled into the flow channel of the baffles 7, and the vessel was sealed. The extraction temperature was set at 38℃, the extraction pressure at 30MPa, and the CO2 flow rate at 150kg / h, and the extraction was performed dynamically for 3.5 hours. After extraction, the whole coffee beans were removed, and after ventilation and drying, decaffeinated coffee beans with intact shape were obtained. HPLC analysis showed that the caffeine removal rate reached 98.3%, and the retention rate of the original flavor substances of the coffee beans reached over 95%. 24 g of crude caffeine was obtained from the separation vessel 5, and after purification, a purity of 99.1% was obtained. 20g of caffeine crystals.

[0030] Example 2

[0031] Two kilograms of whole Arabica coffee beans were sieved to remove impurities, then soaked in room temperature purified water for 7 hours without crushing. The moisture content was measured to be 48%. After draining, the beans were placed into the extraction vessel 4 with baffles 7 of this invention. The extraction temperature was set at 36°C, the extraction pressure at 32 MPa, and the CO2 flow rate at 180 kg / h. At the same time, 2% of the weight of the raw material in food-grade pure water was added to the extraction vessel 4 as an entrainer, and dynamic extraction was carried out for 3 hours. After extraction, whole decaffeinated coffee beans were obtained. The caffeine removal rate was tested to be 98.7%, and the flavor substance retention rate was over 94%. 26g of crude caffeine was separated, and after refining, 22g of caffeine crystals with a purity of 99.3% were obtained.

[0032] Example 3

[0033] Take 2 kg of Arabica coffee beans from the same batch, with the same raw material grade, origin, and moisture content as in the above example. Crush the coffee beans using a food-grade grinder, controlling the particle size to 20-40 mesh. After crushing, sieve to remove impurities, including broken shells, dust, and other contaminants. Soak the beans in purified water of the same specification at room temperature for 7 hours. After soaking, the moisture content of the material is measured to be 48%. After thoroughly draining the water, the beans are placed in a conventional extraction vessel without baffles. Strictly match the same extraction process parameters, setting the extraction temperature to 36℃, extraction pressure to 32MPa, and CO2 flow rate to 180kg / h. Simultaneously add 2% (by weight) of food-grade purified water as an entrainer to the extraction vessel and extract dynamically for 3 hours under the same conditions. After extraction, the processed broken coffee beans were collected. The results showed that the caffeine removal rate of the control group coffee beans was 89.2%, and the retention rate of aromatic substances and lipid flavor substances inside the coffee beans was only 81.5%. After extraction and separation, 21g of crude caffeine was obtained. After processing with the same refining and purification process, 16g of caffeine crystals with a purity of 99.1% were obtained.

[0034] A comparison of the coffee bean crushing processes in Examples 1 and 2 with those in Example 3 shows that the retention rates of aromatic and lipid flavor compounds in the coffee beans after crushing are lower than those after non-crushing, and the yield of caffeine crystals is also better than that after crushing.

[0035] Addressing the industry pain point of flavor loss due to coffee bean breakage in existing technologies, this invention preserves the original, intact shape of coffee beans throughout the entire process, without any crushing or pulverizing. While efficiently extracting caffeine, it maximizes the preservation of the original flavor compounds and structural integrity of the coffee beans, completely resolving the industry contradiction of balancing extraction efficiency and flavor retention. To address the issue of dense cell walls and high caffeine diffusion resistance in whole coffee beans, a dedicated pretreatment process is optimized. Whole coffee beans are soaked in room-temperature purified water for 7 hours, allowing them to fully absorb water and swell, softening the cell walls and significantly reducing caffeine diffusion resistance. This synergistic effect with the optimized extraction device further enhances the caffeine extraction efficiency of whole coffee beans. Furthermore, the supercritical extraction process parameters are optimized to suit whole coffee beans and the baffled extraction vessel 4, achieving high-efficiency extraction at low temperature and low pressure. This reduces equipment investment and operating energy consumption, is entirely green and environmentally friendly, leaves no organic solvent residue, and is suitable for industrial mass production needs.

[0036] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A device for supercritical high-efficiency extraction of caffeine from coffee beans, characterized in that, The system includes a CO2 storage tank (1), a high-pressure pump (2), a heat exchanger (3), an extraction vessel (4), a separation vessel (5), and a crystallization vessel (6). The CO2 storage tank (1) is used to introduce supercritical CO2 into the extraction vessel (4). The high-pressure pump (2) and the heat exchanger (3) are used to adjust the inlet pressure and inlet temperature of CO2 into the extraction vessel (4). The extraction vessel (4) is used for the extraction of whole coffee beans. The separation vessel (5) is used for the crude separation of caffeine. The crystallization vessel (6) is used for the refined crystallization of crude caffeine. The extraction vessel (4) is provided with an "S"-shaped flow channel to extend the travel of coffee beans in the extraction vessel (4).

2. The apparatus for supercritical high-efficiency extraction of caffeine from coffee beans according to claim 1, characterized in that, The extraction vessel (4) is a vertical vessel. The extraction vessel (4) is equipped with multiple baffles (7) arranged alternately in the upper and lower parts and in the left and right parts. The baffles (7) are semi-circular structures. The outer diameter of the baffles (7) is sealed and fitted to the inner wall of the extraction vessel (4). The baffles (7) that are adjacent to each other form an "S" shaped flow channel that allows whole coffee beans to pass through.

3. The apparatus for supercritical high-efficiency extraction of caffeine from coffee beans according to claim 2, characterized in that, Both ends of the extraction vessel (4) are detachably fitted with sealing end caps. The upper sealing end cap of the extraction vessel (4) is provided with a CO2 fluid outlet and a material inlet, and the lower sealing end cap of the extraction vessel (4) is provided with a CO2 fluid inlet and a material outlet.

4. The apparatus for supercritical high-efficiency extraction of caffeine from coffee beans according to claim 3, characterized in that, The extraction vessel (4) is equipped with sieve plates at both the bottom and top. The bottom sieve plate of the extraction vessel (4) is used to support whole coffee beans, and the top sieve plate of the extraction vessel (4) is used to prevent whole coffee beans from escaping from the top of the extraction vessel (4). The aperture of the sieve plate is smaller than the particle size of the coffee beans.

5. The apparatus for supercritical high-efficiency extraction of caffeine from coffee beans according to claim 1, characterized in that, It also includes a condenser (8) and a circulation pump (9), the condenser (8) being used for condensing CO2 fluid and the circulation pump (9) being used for reintroducing the condensed CO2 fluid into the CO2 storage tank (1).

6. The apparatus for supercritical high-efficiency extraction of caffeine from coffee beans according to claim 4, characterized in that, The inner diameter of the extraction vessel (4) is 200 mm, the width of the baffle (7) is 140 mm, the vertical distance between two adjacent baffles (7) is 50 mm, and the total height of each baffle (7) in the extraction vessel (4) is 1000 mm.

7. A method for supercritical efficient extraction of caffeine from coffee beans, characterized in that, The apparatus for supercritical high-efficiency extraction of caffeine from coffee beans according to any one of claims 1-6 is used to extract caffeine from coffee beans, comprising the following steps: S1. Coffee bean pretreatment: Soak whole coffee beans in room temperature purified water for 7 hours; S2, Loading: Put the pre-treated whole coffee beans into the extraction vessel (4), and fill them evenly in the "S" flow channel area formed by the baffle (7). The material filling height is adapted to the baffle (7) arrangement area to ensure that the fluid is in full contact with the material throughout the process. Seal the end cap of the extraction vessel (4). S3, Extraction in extraction vessel (4); The extraction temperature of coffee beans in extraction vessel (4) is controlled at 35-40℃, the extraction pressure is controlled at 28-32MPa; the CO2 flow rate is controlled at 100-200kg / h, and the dynamic extraction time is 3-4h; S4, Analysis: Supercritical CO2 fluid rich in caffeine flows out from the CO2 fluid outlet at the top of the extraction vessel (4) and enters the separation vessel (5) for analysis; S5, Medium circulation: The CO2 fluid after analysis is condensed by the condenser (8), pressurized by the circulation pump (9), and then returned to the CO2 storage tank (1); S6. Coffee bean product processing: After extraction, whole coffee beans are taken out from the extraction vessel (4) and dried at room temperature and ventilation to obtain low-decaffeinated coffee beans that retain their original complete shape and characteristic flavor. S7. Caffeine Refining: Crude caffeine can be recrystallized with distilled water and decolorized with activated carbon in a crystallization kettle (6) to obtain high-purity caffeine crystals.

8. The method for supercritical high-efficiency extraction of caffeine from coffee beans according to claim 7, characterized in that, The caffeine separation and analysis parameters in S4 are as follows: after the supercritical CO2 fluid rich in caffeine enters the separation vessel (5), the pressure is reduced to 6-8 MPa and the temperature is increased to 45-50℃.

Images