The present invention comprises a pressurized carbonator reactor that circulates the mother carbonate/bicarbonate liquor to maximize the yield of the separated solids and reduce reaction time. In the cyclic process C0 ₂ gas combines with soluble hydroxides to produce high purity carbonate/bicarbonate slurry under controlled pH conditions. The invention also comprises a process for controlled

carbonate/bicarbonate production through the use of the indicated

scrubber/reactor. TECHNICAL FIELD OF THE INVENTION

The present invention relates to a method and a plant design for reacting soluble hydroxides (e.g. NaOH, KOH, NH ₄ OH, ...) with C0 ₂ from a pure source, air/C0 ₂ source, exhaust gas/C0 ₂ source or natural gas/C0 ₂ source. The product of the invention is C0 ₂ scrubbed gas stream, and a solid bicarbonate (e.g. NaHC0 ₃ ) and/or carbonate (e.g. Na ₂ C0 ₃ ) product. The products bicarbonate/carbonate are high purity thus are readily marketable to specialty industry or decomposed under a circulation stream to produce high purity C0 ₂ gas stream ready for industrial usage or storage.

BACKGROUND OF THE INVENTION Energy usage for regenerating the C0 ₂ adsorbent is critical to all present C0 ₂ sequestration processes. Lowering the energy use for sequestering C0 ₂ is needed for achieving goals of reduction of C0 ₂ emissions. Process economics is also a vital part of the solution. Conventional amine processes are claimed to use about 4 MJ/kg C0 ₂ sequestered and some other processes claim a use down to 3.2 MJ/kg C0 ₂ sequestered. The process according to the present invention achieves results that are better than this by using less energy and at the same time produce a saleable product.

Currently C0 ₂ is removed from power plant flue gas by few different methods mainly absorbing it in some form of amine solution and producing pure compressed C0 ₂ to be deposited. Energy use is estimated at between everything between 10 to 18% of power plant production. Another goal for present developments is less than about 5% by using low temperature decomposable bicarbonates to produce high purity streams of C0 ₂ . Some processes in early stages also target the relatively rare pressurized energy conversion technologies. This needs retrofits to be carried out on boilers.

Common to most of these known technologies is that C0 ₂ must be deposited, typically to old oil and gas fields. This limits the applicability of these technologies as an optimal solution in many areas.

Thus, there is clearly a need for better solutions, and the present invention aims at filling this need.

GENERAL DISCLOSURE OF THE INVENTION More precisely the main objective of the present invention is to achieve a method and a novel plant design for using soluble basic solutions such as NaOH, KOH, NH ₄ OH, etc. to absorb C0 ₂ from any industrial C0 ₂ emission sources and

consequently produce the corresponding high purity bicarbonates and/or carbonates. The low temperature bicarbonates can be circulated to produce high purity C0 ₂ gas. For example, the bicarbonates of potassium or ammonium can be decomposed at chimney temperatures between 60 to 120 °C to produce the pure C0 ₂ streams while the other products are circulated back to the cyclic carbonator reactor.

Particularly, the present invention includes a new and optimised Carbonation reactor. This Carbonation reactor has been designed to ensure for optimised chemical reaction between the C0 ₂ in the exhaust gas and the saturated basic solution (i.e. M ₂ C0 ₃ /MHC0 ₃ , M is alkali or ammonium). The Carbonation reactor's agitator is specially designed to optimise the contact area between the C0 ₂ and the reacting solution components, thus providing an improved carbonation reactor. This is provided for based on kinetics and optimised bubble size and bubble spread distribution. The said method after it enters the cyclic mode can reduce reaction time from an average of six hours to an average of 30 to 40 minutes.

As a result, the present invention uses substantially less than 18% of the energy from the power plant and produces useful and marketable products: alkali and ammonium bicarbonates/carbonates and for separation process pure C0 ₂ streams. In the first case there is no C0 ₂ to be deposited, as this is mainly incorporated in the products. Thus, the carbonator of the present invention is characterized in that it comprises a steel tank with stirrer and cooled double walls, a heat exchanger that cools the carbonator, a coolant volume, a cooled surface area, an impeller that disperses the gas, where said impeller is mounted on a hollow shaft drawing gas from the gas volume at the top of the reactor, three baffles that extend through almost all of the working volume of said tank, motors with variable speed drives, and the shaft seal is double mechanical type with cooling.

Preferably, the carbonator is a 316 stainless steel tank reactor with stirrer and about 70% cooled double walls, with a heat exchanger volume of 1 m ³ - 0.275m ^3, a coolant volume of 56 litres, a cooled surface area of approximately 4m ² , a maximum height of 1835 mm and a diameter of 1000 mm, where the heat that can be removed is about 5kw/°C, and the heat exchanger cools the full carbonator reactor at 4°C/h, while the gas is dispersed from an impeller mounted on a hollow shaft drawing gas from the gas volume at the top of the reactor, while three baffles of 100 mm width extend through almost all of the working volume, and said carbonator reactors have a max filling of 1200 mm recorded height, motors are nominally 5 hp with variable speed drives and a usual operating rpm of about 282, and the carbonator reactor volume to cooled surface area is about 0.23m ³ /m ² , while the shaft seal is double mechanical type with cooling. The industrial plant assembly according to the present invention is characterized by that it includes a carbonator reactor according to claim 1.

In the industrial plant assembly the alkali or ammonium solution is preferably reacted with the C0 ₂ containing flue gas to produce the corresponding

bicarbonates/carbonates for further processing based on a pH control of the basic liquor. The C0 ₂ is preferably fed into the carbonator reactor and bubbled to react with the basic solution producing precipitates of bicarbonates/carbonates in the slurry, and the slurry is preferably separated into precipitate of bicarbonates/carbonates in a filter cake and filtrated in a slurry filter, where the cake is dried. The bicarbonate product is either sold or further processed to carbonate product and pure C0 ₂ stream while the carbonate is marketable. The filter is recycled back to the mother liquor in the carbonator reactors, which has a positive impact on the seeding of crystals in the carbonator reactor reactions. The cyclic mechanism is a novel mechanism that enhances the efficiency and performance of the carbonation process. DETAILED DESCRIPTION OF THE INVENTION

The present invention will now be described in detail with reference to the following figures:

Fig. 1 a-e shows a process plant overview according to the present invention together with a process and instrumentation diagram of the C0 ₂ scrubbing plant according to the present invention.

Fig. 2 shows a diagram of the carbonator reactor according to the present invention.

The novel plant design according to the invention uses a new, revised and optimised version of traditional production processes of sodium bicarbonate and/or sodium carbonate using C0 ₂ by using competitively produced basic solutions based on a cyclic usage of the primitive mother liquor.

The process according to the present invention starts with soluble hydroxide and saturated basic solution feeds, which predominantly consists of any alkali or ammonium hydroxide and their corresponding carbonates/bicarbonates. With reference to figures 1 and 2, the carbonates/bicarbonates is stored in a Water Storage Tank (1, V-100) while the Caustic Solution Vessel (2, V-110) is supplied with a Transfer Pump (Centrifugal) (P-100). Caustic Lye from the Caustic Lye Barrel (3, V-120) is dosed into the Caustic Solution Vessel (2, V-110) via the Caustic Lye Dosing Pump (Diaphragm type) (P-120). The caustic lye, made from either concentrated (up to 47wt%) or flakes of NaOH, or any other base chemical is stirred well with water to create caustic solution in the Caustic Solution Vessel (2, V-110) and the temperature is controlled by using chilled water from the Chiller (CH-400). The caustic solution is transferred to the Carbonator (4, R-200) via the Caustic Solution Transfer Pump (Centrifugal type) (P-130).

There are two Carbonator reactors (R-200 and R-201 in figure 2), both lm ³ CSTR's with gas inducing sparger.

The Carbonator reactors, as shown in figure 2, are 316 stainless steel tank reactor with stirrer and about 70% cooled double walls. Specification is max 10 bars at 200°C. Water from heat exchanger is used. Useful volumes are 1 m ³ each and minimum 0.275m ³ . The coolant volume is 56 litres. Cooled surface area is approximately 4.2m2. Maximum height is 1835 mm and diameter is 1000 mm. Steel thickness is 10 mm. The heat that can be removed is about 5kw/°C. The heat exchanger cools the full carbonator reactor at 4°C/h. The gas is dispersed from an impeller mounted on a hollow shaft drawing gas from the gas volume at the top of the reactor. Impeller diameter is about 400 mm. There are three baffles of 100 mm width and extending through almost all of the working volume. This type of impeller is said to draw gas to a dept of approximately 3.5 m. They are mounted 150 mm from Carbonator reactor bottom. Normal max filling of the carbonator reactors (R- 200 and R-201) will be 1200 mm recorded height. Motors are nominally 5 hp with variable speed drives. Usual operating rpm is about 282. Carbonator reactor volume to cooled surface area is about 0.23m ³ /m ² . Shaft seal is double mechanical type with cooling.

Illustrative process to make NaHCQ3: As can be seen in figure la-e, the caustic solution inlet is at top of the carbonator reactors (R-200 and R-201). Gas, for example C0 ₂ from C0 ₂ cylinder (WT-300) mixed with air (controlled by Air Mass Flow Controller (FT/FV-301) through Static Mixer (ST-300) is introduced to the top of the Carbonators. Gas is drawn from headspace in through hollow impeller shaft and well dispersed in the liquid mix (caustic solution) with a gas inducing impeller. The C0 ₂ in the gas reacts with the saturated caustic solution, to create NaHC0 ₃ Metering is through thermal gas flow meters and mixed with static mixer.

Discharge, mainly water and NaHC0 ₃ as slurry, from each Carbonator reactor (R- 200 and R-201) is run through Reducer and forwarded to common header for both reactors. Upstream from Reducer there are sampling arrangements. The pH and conductivity meters of discharged liquid/slurry from Carbonators (R-200 and R- 201) are set to measure the extent of the reaction and the type of products formed. Both Carbonators (R-200 and R-201) have C0 ₂ measurements on headspace gas. Heat balance over the Carbonator reactors (R-200 and R-201) is also used to follow the reaction.

The slurry discharge from the two Carbonator reactors (R-200 and R-201) goes through a Slurry Transfer Pump (Peristaltic or centrifugal) (P-210A) and the slurry is further taken to a Slurry Filter (SF-300). This Filtration is batch wise in a pressure filter, from which NaHC0 ₃ filter cake is an output. Continuous operation of the whole unit implies a new/extra filter unit. The filtrate output from the Slurry Filter (SF-300) goes to the Filtrate Storage Vessel (V-300). From the Filtrate Storage Tank (V-300) the filtrate is taken back to the Caustic Solution Vessel (V- 110) or directly to the Carbonator reactors (R-200 and R-201). The demo unit provides for good flexibility in recirculation of the filtrate.

The adsorption and precipitation process can be operated continuously through cyclic operation of the two Carbonators (R-200 and R-201) or in series. Seeding of crystals is done by recirculation of filtrate or through only partial emptying of the Carbonator reactors (R-200 and R-201) or a combination of these.

The process is carried through at ambient total pressure and preferably at the highest available C0 ₂ partial pressure. The process is run at near to ambient temperature, starting at about 25°C to 33°C and at the end of the cycle down to 15°C.

Process control may be achieved with a PC-based SCADA system from GE/Fanuk.

The demo-unit shown in detail herein is constructed to produce maximum of design data for the next scale up, not to serve a C0 ₂ emission source optimally.

Shortly summarized the present invention may be presented through the following points. i) The invention concerns in one embodiment a cyclic pressurized carbonator reactor for scrubbing C0 ₂ from industrial gas streams to produce high purity carbonates/bicarbonates, and pure C0 ₂ streams, wherein the said carbonator reactor comprises a steel tank with stirrer and cooled double walls, a heat exchanger that cools the carbonator, a coolant volume, a cooled surface area, an impeller that disperses the gas, where said impeller is mounted on a hollow shaft drawing gas from the gas volume at the top of the reactor, a number of, e.g. three, baffles that extend through almost all of the working volume of the said tank, motors with variable speed drives, and the shaft seal is preferably double mechanical type with cooling. ii) Furthermore the invention comprises a carbonator reactor in accordance with point i) surpa, wherein said carbonator reactor is preferably a 316 stainless steel tank reactor with stirrer and preferably about 70% cooled double walls, with a heat exchanger volume of preferably 1 m ³ - 0.275m ³ a coolant volume of 56 litres, a cooled surface area of preferably approximately 4m ² , a maximum height of preferably 1835 mm and a diameter of preferably 1000 mm, where the heat that can be removed is preferably about 5kw/°C, and the chiller cools the full carbonator reactor preferably at 4°C/h, while the gas is preferably dispersed from an impeller that may be mounted on a hollow shaft drawing gas from the gas volume at the top of the reactor, while e.g. three baffles of preferably 100 mm width extend through almost all of the working volume, and said carbonator reactors have a max filling of e.g. 1200 mm recorded height, motors are preferably nominally 5 hp with variable speed drives and a usual operating rpm of preferably about 282, and the

carbonator reactor volume to cooled surface area is preferably about 0.23m ³ /m ² , while the shaft seal is preferably double mechanical type with cooling. iii) The invention also comprises an industrial demo plant assembly for conducting a reaction of removing of C0 ₂ from combustion gases, wherein said assembly includes a carbonator reactor according to points i) and ii) supra. iv) The invention also comprises an industrial plant assembly according to point iii) supra, wherein all soluble hydroxide and saturated carbonates/bi-carbonates mixture is reacted with the C0 ₂ containing flue gas to produce high purity carbonates/bicarbonates for further processing. v) Furthermore the invention comprises an industrial demo plant assembly according to point iii) supra, wherein the C0 ₂ is fed into the carbonator reactor and bubbled to react with soluble hydroxide and saturated carbonates/bicarbonates mixture, producing precipitates of high purity carbonates/bicarbonates in a slurry. vi) The invention also comprises an industrial demo plant assembly according to point iii) supra, wherein the slurry is separated into precipitate of

carbonates/bicarbonates in a filter cake and filtrated in a slurry filter, where the cake is dried or further processed to carbonates or pure C0 ₂ stream. vii) The invention also comprises an industrial demo plant assembly according to point vi) supra, wherein the filtrate is recycled back to the saturated

carbonates/bicarbonates tank or recycled directly back to the Carbonator reactors, which has a positive impact on the seeding of crystals in the Carbonator reactor reactions.

Also the invention comprises: viii) a process for scrubbing C0 ₂ from industrial gas streams through a cyclic pressurized carbonator reactor to produce high purity carbonates/bicarbonates, and pure C0 ₂ streams, wherein the said carbonator reactor comprises a steel tank with stirrer and cooled double walls, a heat exchanger that cools the carbonator, a coolant volume, a cooled surface area, an impeller that disperses the gas, where said impeller is mounted on a hollow shaft drawing gas from the gas volume at the top of the reactor, preferably three baffles that extend through almost all of the working volume of the said tank, motors with variable speed drives, and the shaft seal is preferably of a double mechanical type with cooling. More specifically the process according to point viii) surpa may be conducted by ix) said carbonator reactor being a 316 stainless steel tank reactor with stirrer and about 70% cooled double walls, with a heat exchanger volume of 1 m ³ - 0.275m ³ a coolant volume of 56 litres, a cooled surface area of approximately 4m ² , a maximum height of 1835 mm and a diameter of 1000 mm, where the heat that can be removed is about 5kw/°C, and the chiller cools the full carbonator reactor at 4°C/h, while the gas is dispersed from an impeller mounted on a hollow shaft drawing gas from the gas volume at the top of the reactor, while three baffles of 100 mm width extend through almost all of the working volume, and said carbonator reactors have a max filling of 1200 mm recorded height, motors are nominally 5 hp with variable speed drives and a usual operating rpm of about 282, and the carbonator reactor volume to cooled surface area is about 0.23m ³ /m ² , while the shaft seal is double mechanical type with cooling. x) The process indicated supra in point ix) may be performed in an industrial demo plant assembly for conducting a reaction of removing of C0 ₂ from combustion gases and including a carbonator reactor according to points i) and ii) surpa. xi) The process according to the inventikon may be conducted as indicated in point x) supra wherein all soluble hydroxide and saturated carbonates/bi-carbonates mixture is reacted with the C0 ₂ containing flue gas to produce high purity carbonates/bicarbonates for further processing. xii) The process according to the present invention may also be conducted in accordance with point x) supra, wherein the C0 ₂ is fed into the carbonator reactor and bubbled to react with soluble hydroxide and saturated carbonates/bicarbonates mixture, producing precipitates of high purity carbonates/bicarbonates in a slurry. xiii) The process according to the present invention may also be conducted according to point x) supra, wherein the slurry is separated into precipitate of carbonates/bicarbonates in a filter cake and filtrated in a slurry filter, where the cake is dried or further processed to carbonates or pure C0 ₂ stream. xiv) The process according to the present invention may also be conducted according to point xiii) supra, wherein the filtrate is recycled back to the saturated carbonates/bicarbonates tank or recycled directly back to the Carbonator reactors, which has a positive impact on the seeding of crystals in the Carbonator reactor reactions.