Patent ID: 12221382

DETAILED DESCRIPTION

The present disclosure describes example implementations of a high temperature hydrator system that may enable two or more solid feedstocks and any resulting solid reaction products to separate into two distinctly different fluidization regimes, based on the different solid physical properties, such as density, particle size distribution and shape. For example, a portion of the feedstocks and a portion of the resulting reaction products, consisting of, for example, more dense particles, larger particles and/or particles of a geometry, which, in the given fluidization environment, favor a bubbling bed regime, while another portion of the feedstocks and reaction products, consisting for example of less dense particles, smaller particles, and/or particles of a geometry, which, in the given fluidization environment, favor a turbulent or transport regime. Regimes of fluidization may result from the fact that fluidized solid beds behave differently as gas properties, velocity, and solid properties are varied. For example, when a solid bed (having a defined set of solid properties) is exposed to an upward flowing fluid, such as a gas (having a defined set of fluid properties), a pressure drop develops across the bed. As the upward flow rate of the fluid increases, there are a range of fluidization regimes that may develop.

One example of a distinct fluidization regime is the bubbling bed regime. A bubbling bed regime is one where the solid material is fluidized above the material's incipient fluidization point but below the point where the material becomes entrained in the gas and capable of leaving the reactor with the gas flow. Another example of a distinct fluidization regime is a turbulent, or transport regime. The turbulent or transport regime is one where the solid material is fluidized to the point where the material becomes entrained in the gas and is transported out of the reactor with the gas. Other examples of distinct fluidization regimes seen in fluidized bed reactors may include homogeneous, dense suspension upflow, slugging, spouted bed, turbulent, fast fluidizing, and pneumatic transport.

In addition to fluidizing the solids, this system provides a desirable environment to allow for the hydrating reaction to occur, whereby incoming calcium oxide mixes with water, in the form of liquid and/or steam, to produce calcium hydroxide. The sensible heat from some of the hot solid feed material, as well as the heat generated from the hydrating reaction itself are used to dry and preheat the other cooler, moist solid materials. Both the hydrating reaction and the heat transfer processes take place in a fluidized bed reactor vessel wherein solid calcium carbonate, solid calcium oxide, steam and liquid water come into contact.

This system includes multiple components, for example dryer, hydrators and heat exchange componentry, in a single unit. In some aspects, conventional components for hydrating processes, such as a dryer, hydrator and heat exchange equipment, are replaced by one fluidized bed reactor. This resulting high temperature fluidized bed hydrator unit has higher thermal efficiency than the previously separated equipment, due to having the process streams in direct contact with heat sources (for example, other process streams, fluidizing gases). By using process streams in this manner, the desired multiple approach temperatures associated with separate heat exchangers are also reduced, for example, from multiple approaches to a single approach. The fluidized bed reactor unit has no moving parts, unlike conventional hydrator and dryer units, and as such, has lower maintenance than such conventional units.

Each of the configurations described later may include process streams (also called “streams”) within a system for converting calcium oxide to calcium hydroxide including a fluidized bed. The process streams can be flowed using one or more flow control systems implemented throughout the system. A flow control system can include one or more flow pumps to pump the process streams, one or more flow pipes through which the process streams are flowed and one or more valves to regulate the flow of streams through the pipes.

In some implementations, a flow control system can be operated manually. For example, an operator can set a flow rate for each pump and set valve open or close positions to regulate the flow of the process streams through the pipes in the flow control system. Once the operator has set the flow rates and the valve open or close positions for all flow control systems distributed across the system for converting calcium oxide to calcium hydroxide, the flow control system can flow the streams under constant flow conditions, for example, constant volumetric rate or other flow conditions. To change the flow conditions, the operator can manually operate the flow control system, for example, by changing the pump flow rate or the valve open or close position.

In some implementations, a flow control system can be operated automatically. For example, the flow control system can be connected to a computer or control system (e.g., control system999) to operate the flow control system. The control system can include a computer-readable medium storing instructions (such as flow control instructions and other instructions) executable by one or more processors to perform operations (such as flow control operations). An operator can set the flow rates and the valve open or close positions for all flow control systems distributed across the facility using the control system. In such implementations, the operator can manually change the flow conditions by providing inputs through the control system. Also, in such implementations, the control system can automatically (that is, without manual intervention) control one or more of the flow control systems, for example, using feedback systems connected to the control system. For example, a sensor (such as a pressure sensor, temperature sensor or other sensor) can be connected to a pipe through which a process stream flows. The sensor can monitor and provide a flow condition (such as a pressure, temperature, or other flow condition) of the process stream to the control system. In response to the flow condition exceeding a threshold (such as a threshold pressure value, a threshold temperature value, or other threshold value), the control system can automatically perform operations. For example, if the pressure or temperature in the pipe exceeds the threshold pressure value or the threshold temperature value, respectively, the control system can provide a signal to the pump to decrease a flow rate, a signal to open a valve to relieve the pressure, a signal to shut down process stream flow, or other signals.

Referring toFIG.1, calcium oxide conversion to calcium hydroxide in the presence of a fluid bed is described with respect to illustrative system100. In some implementations, system100may include feed ports for streams101,102and105fluidly coupled to the main system100, and a discharge port for stream104fluidly coupled to the main system100. In some aspects a gas distribution plate106may be fluidly coupled to the main vessel body of system100. In some aspects system100may include a cyclone111fluidly coupled to feed ports for stream109and discharge ports for streams112,110. In some aspects system100may include a control system999coupled to the components (illustrated or otherwise).

In some implementations, fluidization gases include, for example, air, steam, and the like. As depicted inFIG.1, gaseous stream102including one or more fluidization gases is provided to the hydrator system100through the bottom entry zone113, also known as the plenum chamber, which is below the fluidization distribution plate106. Gaseous stream102may be, for example, air, steam or a combination of these gases and their sub-components. Stream101is one of the solid feedstocks, which enters the system above the fluidization distribution plate106and becomes fluidized in the bed or bubbling bed regimes within the fluidized bed system100and as such it remains in the bubbling bed zone107, unless discharged as stream104. Stream101may, for example, consist mostly of calcium carbonate or calcium oxide, and may also consist in part of aqueous solutions such as liquid water. Stream105is the solid feedstock which becomes fluidized in the turbulent or transport fluidization regime and it also enters the system above the distribution plate106. Stream105may, for example, consist mostly of calcium oxide or calcium carbonate and may also consist in part of liquid or gaseous water. The distribution plate106is designed to prevent backflow of any solids into the fluidization gas entry zone113. Solid material105, any associated reaction products and any steam generated from liquid water content present in the system are carried out of the bubbling bed107and transported through the reactor freeboard zone108. The resulting mixed stream of fluidization gases and solids is mixed-stream109, and after leaving the reactor freeboard zone108, the stream109is sent to a cyclone111, to separate the solids112, from the gases110. The fluidization gas102, is blown into the fluidization gas entry zone113, of the fluidized bed reactor100. This fluidizing gas102, could be partially recycled from the gas stream110leaving the cyclone111.

The hydrating reaction, where calcium oxide is converted to calcium hydroxide, takes place within the fluidized bed reactor system100:
CaO(s)+H2O(l)→Ca(OH)2(s) hydrating reaction using liquid water.
CaO(s)+H2O(g)→Ca(OH)2(s) hydrating reaction using steam.

In some cases the water required for the hydrating reaction can be supplied into system100through excess steam brought in with stream102, or it could also be brought into the system100as part of the solids material requiring heating/drying, via stream101or105. In some cases, the stream requiring heat transfer (and that may contain liquid water) could be either stream101or105, depending on the application. For example, in a Kraft caustic recovery system, the calcium carbonate material may be introduced as smaller particles, which may be more comparable to lime mud in particle size, while the calcium oxide material may be introduced as larger particles or clumps, and could have sizes closer to approximately one (1) centimeter in diameter.

In some implementations, a portion of the material normally fluidized within the turbulent/transport regime may leave with the material in the bubbling bed regime. In these implementations, it can be separated based on the difference in physical properties and re-introduced into the reactor system100or combined with the finished circulating solids stream112.

In some implementations, the system100could be heat insulated with, for example insulation material. In these cases, care would need to be taken in selecting both the insulation material for heat economy, as well as the vessel material of construction. In some aspects, metal compositions that are capable of maintaining structural integrity under operating pressures and temperatures of around 300° C. would be selected, for example stainless steel or other metal compositions.

In another implementation, system100could instead be insulated with refractory lining, allowing for more economical options for vessel material of construction, for example carbon steel.

Referring toFIG.2, calcium oxide conversion to calcium hydroxide in the presence of a fluid bed is described with respect to illustrative system200. In some implementations, system200may include feed ports for streams201,202,205and214fluidly coupled to the main system200, and a discharge port for stream204fluidly coupled to the main system200. In some aspects a gas distribution plate206may be fluidly coupled to the main vessel body of system200. In some aspects system200may include a cyclone211fluidly coupled to feed ports for stream209and discharge ports for streams212,210. In some aspects system200may include a control system999coupled to the components (illustrated or otherwise).

In some implementations, fluidization gases include, for example, air, steam, and the like. As depicted inFIG.2, gaseous stream202including one or more fluidization gases is provided to the hydrator system200through the bottom entry zone213, also known as the plenum chamber, which is below the fluidization distribution plate206. Gaseous stream202may be, for example, air, steam or a combination of these gases and their sub-components. Stream201is one of the solid feedstocks, which enters the system above the fluidization distribution plate206and becomes fluidized in the bed or bubbling bed regimes within the fluidized bed system200and as such it remains in the bubbling bed zone207, unless discharged as stream204. Stream201may, for example, consist mostly of calcium carbonate or calcium oxide, and may also consist in part of aqueous solutions such as liquid water. Stream205is the solid feedstock which becomes fluidized in the turbulent or transport fluidization regime and it also enters the system above the distribution plate206. Stream205may, for example, consist mostly of calcium oxide or calcium carbonate and may also consist in part of liquid or gaseous water. The distribution plate206is designed to prevent backflow of any solids into the fluidization gas entry zone213. Solid material205, any associated reaction products and any steam generated from liquid water content present in the system are carried out of the bubbling bed207and transported through the reactor freeboard zone208. The resulting mixed stream of fluidization gases and solids is mixed-stream209, and after leaving the reactor freeboard zone208, the stream209is sent to a cyclone211, to separate the solids212, from the gases210. The fluidization gas202, is blown into the fluidization gas entry zone,213, of the fluidized bed reactor,200. This fluidizing gas202, could be partially recycled from the gas stream210leaving the cyclone211. A portion of the water required for the hydrating reaction can be supplied into system200through a variety of feed methods including excess steam brought in with stream202, as a direct, separate spray of liquid water,214, which could be fed into either the bubbling bed207or freeboard zone208, or a combination of these methods.

Referring toFIG.3A, calcium oxide conversion to calcium hydroxide in the presence of a fluid bed is described with respect to illustrative system300. In some implementations, system300may include feed ports for streams301,302, and305fluidly coupled to the main system300, and a discharge port for stream304fluidly coupled to the main system300. In some aspects a gas distribution plate306may be fluidly coupled to the main vessel body of system300. In some aspects system300may include a cyclone311fluidly coupled to feed ports for stream309and discharge ports for streams312,310. In some aspects the cyclone discharge port for stream312is fluidly coupled back to the main body of system300, and may include a non-mechanical valve and feed port on the main body for recirculation of stream315back into the main body and a discharge port for stream316. In some aspects system300may include a control system999coupled to the components (illustrated or otherwise).

In some implementations, fluidization gases include, for example, air, steam, and the like. As depicted inFIG.3A, gaseous stream302including one or more fluidization gases is provided to the hydrator system300through the bottom entry zone313, also known as the plenum chamber, which is below the fluidization distribution plate306. Gaseous stream302may be, for example, air, steam or a combination of these gases and their sub-components. Stream301is one of the solid feedstocks, which enters the system above the fluidization distribution plate306and becomes fluidized in the bed or bubbling bed regimes within the fluidized bed system300and as such it remains in the bubbling bed zone307, unless discharged as stream304. Stream301may, for example, consist mostly of calcium carbonate or calcium oxide, and may also consist in part of aqueous solutions such as liquid water. Stream305is the solid feedstock which becomes fluidized in the turbulent or transport fluidization regime and it also enters the system above the distribution plate306. Stream305may, for example, consist mostly of calcium oxide or calcium carbonate and may also consist in part of liquid or gaseous water. The distribution plate306is designed to prevent backflow of any solids into the fluidization gas entry zone313. Solid material305, any associated reaction products and any steam generated from liquid water content present in the system are carried out of the bubbling bed307and transported through the reactor freeboard zone308. The resulting mixed stream of fluidization gases and solids is mixed-stream309, and after leaving the reactor freeboard zone308, the stream309is sent to a cyclone311, to separate the solids312, from the gases310. The fluidization gas302, is blown into the fluidization gas entry zone,313, of the fluidized bed reactor,300. This fluidizing gas302, could be partially recycled from the gas stream310leaving the cyclone311. A portion of the solid stream312leaving the cyclone311is recycled back into system300as stream315. If additional residence time is required for the solids being discharged from the cyclone311, these solids can be fully or partially re-introduced back into the fluidization vessel of system300, via stream315, for example, in a similar fashion to that of a circulating fluidized bed reactor. In some aspects, stream315can be re-introduced into the fluidization vessel of system300by means of a non-mechanical valve. Some examples of non-mechanical valves are L-valves, J-valves, V-valves, loop seals, seal pots, reverse seals and the like. Stream316can be used to withdraw a portion of the circulating solid material from system300.

Referring toFIG.3B, calcium oxide conversion to calcium hydroxide in the presence of a fluid bed is described with respect to illustrative system300. In some implementations, system300may include feed ports for streams301,302, and305fluidly coupled to the main system300, and a discharge port for stream304fluidly coupled to the main system300. In some aspects a gas distribution plate306may be fluidly coupled to the main vessel body of system300. In some aspects system300may include a cyclone311fluidly coupled to feed ports for stream309and discharge ports for streams312,310. In some aspects the cyclone discharge port for stream312is fluidly coupled back to the main body of system300, and may include a non-mechanical valve such as a loop seal317fluidly coupled to a feed port on the main body for recirculation of stream315back into the main body and a discharge port for stream316. In some aspects system300may include a control system999coupled to the components (illustrated or otherwise). In some aspects the loop seal317is fluidly coupled to a distribution plate319and feed port for stream318.

In some implementations, fluidization gases include, for example, air, steam, and the like. As depicted inFIG.3A, gaseous stream302including one or more fluidization gases is provided to the hydrator system300through the bottom entry zone313, also known as the plenum chamber, which is below the fluidization distribution plate306. Gaseous stream302may be, for example, air, steam or a combination of these gases and their sub-components. Stream301is one of the solid feedstocks, which enters the system above the fluidization distribution plate306and becomes fluidized in the bed or bubbling bed regimes within the fluidized bed system300and as such it remains in the bubbling bed zone307, unless discharged as stream304. Stream301may, for example, consist mostly of calcium carbonate or calcium oxide, and may also consist in part of aqueous solutions such as liquid water. Stream305is the solid feedstock which becomes fluidized in the turbulent or transport fluidization regime and it also enters the system above the distribution plate306. Stream305may, for example, consist mostly of calcium oxide or calcium carbonate and may also consist in part of liquid or gaseous water. The distribution plate306is designed to prevent backflow of any solids into the fluidization gas entry zone313. Solid material305, any associated reaction products and any steam generated from liquid water content present in the system are carried out of the bubbling bed307and transported through the reactor freeboard zone308. The resulting mixed stream of fluidization gases and solids is mixed-stream309, and after leaving the reactor freeboard zone308, the stream309is sent to a cyclone311, to separate the solids312, from the gases310. The fluidization gas302, is blown into the fluidization gas entry zone,313, of the fluidized bed reactor300. This fluidizing gas302, could be partially recycled from the gas stream310leaving the cyclone311.

A portion of the solid stream312leaving the cyclone311is recycled back into system300as stream315. If additional residence time is required for the solids being discharged from the cyclone311, these solids can be fully or partially re-introduced back into the fluidization vessel of system300, via stream315, for example, in a similar fashion to that of a circulating fluidized bed reactor. In some aspects, stream315can be re-introduced into the fluidization vessel of system300by means of a non-mechanical valve.

Some examples of non-mechanical valves are L-valves, J-valves, V-valves, loop seals, seal pots, reverse seals and the like. Stream316can be used to withdraw a portion of the circulating solid material from system300. All components in the system300are substantially the same as in the embodiment of the system300illustrated inFIG.3A, with the exception being that more detail is shown on how the system300could be built to accommodate the recirculation of solid stream312. In this implementation, solid stream312is shown moving down a vertical length of pipe that connects the cyclone311back to the main vessel body of system300. In some example aspects, this pipe may include a non-mechanical valve, such as a loop seal317complete with a gas stream318being fed through a distribution plate319. In some aspects the distribution plate319may instead be nozzles. In some aspects the gas stream318may for example include air, steam or the like. Stream318provides sufficient backpressure through the loop seal317so that fluidizing gases from the main vessel system300do not divert backwards through the loop seal317.

Referring toFIG.4A, calcium oxide conversion to calcium hydroxide in the presence of a fluid bed is described with respect to illustrative system400. In some implementations, system400may include feed ports for streams401,402, and405fluidly coupled to the main system400, and a discharge port for stream404fluidly coupled to the main system400. In some aspects the discharge port404is fluidly coupled to a solids classifier unit, for example an external sieve unit420. The external sieve unit420is fluidly coupled to discharge ports for streams422and421. In some aspects a gas distribution plate406may be fluidly coupled to the main vessel body of system400. In some aspects system400may include a cyclone411fluidly coupled to feed ports for stream409and discharge ports for streams412,410. In some aspects system400may include a control system999coupled to the components (illustrated or otherwise).

In some implementations, fluidization gases include, for example, air, steam, and the like. As depicted inFIG.4A, gaseous stream402including one or more fluidization gases is provided to the hydrator system400through the bottom entry zone413, also known as the plenum chamber, which is below the fluidization distribution plate406. Gaseous stream402may be, for example, air, steam or a combination of these gases and their sub-components. Stream401is one of the solid feedstocks, which enters the system above the fluidization distribution plate406and becomes fluidized in the bed or bubbling bed regimes within the fluidized bed system400and as such it remains in the bubbling bed zone407, unless discharged as stream404. Stream401may, for example, consist mostly of calcium carbonate or calcium oxide, and may also consist in part of aqueous solutions such as liquid water. Stream405is the solid feedstock which becomes fluidized in the turbulent or transport fluidization regime and it also enters the system above the distribution plate406. Stream405may, for example, consist mostly of calcium oxide or calcium carbonate and may also consist in part of liquid or gaseous water. The distribution plate406is designed to prevent backflow of any solids into the fluidization gas entry zone413. Solid material405, any associated reaction products and any steam generated from liquid water content present in the system are carried out of the bubbling bed407and transported through the reactor freeboard zone408. The resulting mixed stream of fluidization gases and solids is mixed-stream409, and after leaving the reactor freeboard zone408, the stream409is sent to a cyclone411, to separate the solids412, from the gases410. The fluidization gas402, is blown into the fluidization gas entry zone413, of the fluidized bed reactor400. This fluidizing gas402, could be partially recycled from the gas stream410leaving the cyclone411. An external sieve unit420is used to segregate material withdrawn from the bubbling bed zone407based on physical properties, for example particle size. A portion of the material normally fluidized within the turbulent/transport regime may leave with the material in the bubbling bed regime in stream404.

In this implementation, the turbulent or transport regime material can be separated from the bubbling regime material based on the difference in physical properties, using sieve unit420such that the smaller material drops through the sieve420and leaves as stream421, and the larger material remains above the sieve holes and leaves as stream422. Stream421can be re-introduced into the reactor system400for further reaction, or combined with the finished circulating solids stream412and sent to downstream processing, for example to cooling and/or lime slurry systems that can be used in carbon dioxide capture facilities such as industrial (point source) facilities and facilities that capture more dilute carbon dioxide sources such as direct air capture facilities, as well as waste water treatment facilities or Kraft caustic recover processes. Stream422could also be sent to downstream processing, for example to heat exchangers and fluid bed calciner systems sometimes used in direct air capture facilities.

In some aspects, stream421may include for example calcium oxide and calcium hydroxide particles, and stream422may include for example calcium carbonate pellets.

Referring toFIG.4B, calcium oxide conversion to calcium hydroxide in the presence of a fluid bed is described with respect to illustrative system400. In some implementations, system400may include feed ports for streams401,402, and405fluidly coupled to the main system400, and a discharge port for stream404fluidly coupled to the main system400. In some aspects the discharge port404is fluidly coupled to an internal solids classifier unit430, which is internal to system100. In some aspects, the internal solids classifier unit430can be a cone and cap sloped stripper. In some aspects the internal solids classifier unit430is fluidly coupled to a feed port for stream431and a discharge port for stream404. In some aspects a gas distribution plate406may be fluidly coupled to the main vessel body of system400. In some aspects system400may include a cyclone411fluidly coupled to feed ports for stream409and discharge ports for streams412,410. In some aspects system400may include a control system999coupled to the components (illustrated or otherwise).

In some implementations, fluidization gases include, for example, air, steam, and the like. As depicted inFIG.4B, gaseous stream402including one or more fluidization gases is provided to the hydrator system400through the bottom entry zone413, also known as the plenum chamber, which is below the fluidization distribution plate406. Gaseous stream402may be, for example, air, steam or a combination of these gases and their sub-components. Stream401is one of the solid feedstocks, which enters the system above the fluidization distribution plate406and becomes fluidized in the bed or bubbling bed regimes within the fluidized bed system400and as such it remains in the bubbling bed zone407, unless discharged as stream404. Stream401may, for example, consist mostly of calcium carbonate or calcium oxide, and may also consist in part of aqueous solutions such as liquid water. Stream405is the solid feedstock which becomes fluidized in the turbulent or transport fluidization regime and it also enters the system above the distribution plate406. Stream405may, for example, consist mostly of calcium oxide or calcium carbonate and may also consist in part of liquid or gaseous water. The distribution plate406is designed to prevent backflow of any solids into the fluidization gas entry zone413. Solid material405, any associated reaction products and any steam generated from liquid water content present in the system are carried out of the bubbling bed407and transported through the reactor freeboard zone408. The resulting mixed stream of fluidization gases and solids is mixed-stream409, and after leaving the reactor freeboard zone408, the stream409is sent to a cyclone411, to separate the solids412, from the gases410. The fluidization gas402, is blown into the fluidization gas entry zone413, of the fluidized bed reactor,400. This fluidizing gas402, could be partially recycled from the gas stream410leaving the cyclone411. Componentry internal to system400is used to segregate material withdrawn from the bubbling bed zone407based on physical properties, for example particle size and/or density.

In this implementation, material is segregated based on physical properties such as size, and/or mass, through use of a baffled channel or annulus solids classifier component430. Material from the bubbling bed zone407enters this component430, and the baffles and upward flowing gases from stream431prevent smaller or lighter particles from making it to the bottom discharge section and instead act to push the smaller and/or lighter material back into the main vessel body of system400. The larger or heavier material moves down through component430to the bottom discharge portion where it can then be discharged as stream404. In some aspects, stream431includes gases such as air or steam and the like. In some aspects, component430may for example be a cone and cap sloped stripper. In other aspects, component430could be similar to the mechanisms of discharging spent catalyst material from gas-solid fluidized beds, such as those found in fluidized beds used for catalytic cracking of hydrocarbons. In catalytic cracking fluidized beds, the spent catalyst solids are discharged, for example, from a fluidized bubbling (non-circulating) bed via a baffled annulus such that larger catalyst moves downward and out into a discharge channel, and finer material and gases move upward back into fluidization vessel.

Referring toFIG.5A, calcium oxide conversion to calcium hydroxide in the presence of a fluid bed is described with respect to illustrative system500. In some implementations, system500may include feed ports for streams501,502, and505and fluidly coupled to the main system500, and a discharge port for stream504fluidly coupled to the main system500. In some aspects a gas distribution plate506may be fluidly coupled to the main vessel body of system500. In some aspects system500may include a cyclone511fluidly coupled to feed ports for stream509and discharge ports for streams512,510. In some aspects system500may include heat tubing componentry544fluidly coupled to system500, including a feed port for stream549and a discharge port for stream550fluidly coupled to the heat tubing componentry544. In some aspects system500may include a control system999coupled to the components (illustrated or otherwise).

In some implementations, fluidization gases include, for example, air, steam, and the like. As depicted inFIG.5A, gaseous stream502including one or more fluidization gases is provided to the hydrator system500through the bottom entry zone513, also known as the plenum chamber, which is below the fluidization distribution plate506. Gaseous stream502may be, for example, air, steam or a combination of these gases and their sub-components. Stream501is one of the solid feedstocks, which enters the system above the fluidization distribution plate506and becomes fluidized in the bed or bubbling bed regimes within the fluidized bed system500and as such it remains in the bubbling bed zone507, unless discharged as stream504. Stream501may, for example, consist mostly of calcium carbonate or calcium oxide, and may also consist in part of aqueous solutions such as liquid water. Stream505is the solid feedstock which becomes fluidized in the turbulent or transport fluidization regime and it also enters the system above the distribution plate506. Stream505may, for example, consist mostly of calcium oxide or calcium carbonate and may also consist in part of liquid or gaseous water. The distribution plate506is designed to prevent backflow of any solids into the fluidization gas entry zone513. Solid material505, any associated reaction products and any steam generated from liquid water content present in the system are carried out of the bubbling bed507and transported through the reactor freeboard zone508. The resulting mixed stream of fluidization gases and solids is mixed-stream509, and after leaving the reactor freeboard zone508, the stream509is sent to a cyclone511, to separate the solids512, from the gases510. The fluidization gas502, is blown into the fluidization gas entry zone513, of the fluidized bed reactor500. This fluidizing gas502, could be partially recycled from the gas stream510leaving the cyclone511. heating tube componentry544, has been added to the vessel walls of system500in the bubbling bed zone507.

In this implementation, any portions of either the sensible heat or heat from the hydrating reaction, which is not consumed to heat the pellets and supply the enthalpy to bring the pellets to the operating temperature of the fluid bed, is used instead to make saturated steam for subsequent superheat and power generation. In this implementation, The high temperature hydrator system500is built with heat tubing componentry544which lines the inner wall of the unit, within the bubbling bed zone507. During operation of system500, a stream549which could be for example, boiler feed water another appropriate heat exchange fluid, or another process fluid stream, is fed into the tube componentry544, where the heat from the fluidized bed zone507moves through the tubes and into the contents of stream549as they move through the tubes. In some aspects, stream549is boiler feed water and this indirect heating converts the boiler feed water into saturated steam that leaves the tube componentry as stream550. In some aspects, the saturated steam from these tubes is sent as stream550to downstream heat consumers or power producers, for example other process heat exchangers or a steam superheater unit and/or steam turbine.

Referring toFIG.5B, calcium oxide conversion to calcium hydroxide in the presence of a fluid bed is described with respect to illustrative system500. In some implementations, system500may include feed ports for streams501,502, and505and fluidly coupled to the main system500, and a discharge port for stream504fluidly coupled to the main system500. In some aspects a gas distribution plate506may be fluidly coupled to the main vessel body of system500. In some aspects system500may include a cyclone511fluidly coupled to feed ports for stream509and discharge ports for streams512,510. In some aspects system500may include heat tubing componentry554fluidly coupled to system500, including a feed port for stream555and a discharge port for stream556fluidly coupled to the heat tubing componentry554. In some aspects system500may include a control system999coupled to the components (illustrated or otherwise).

In some implementations, fluidization gases include, for example, air, steam, and the like. As depicted inFIG.5B, gaseous stream502including one or more fluidization gases is provided to the hydrator system500through the bottom entry zone513, also known as the plenum chamber, which is below the fluidization distribution plate506. Gaseous stream502may be, for example, air, steam or a combination of these gases and their sub-components. Stream501is one of the solid feedstocks, which enters the system above the fluidization distribution plate506and becomes fluidized in the bed or bubbling bed regimes within the fluidized bed system500and as such it remains in the bubbling bed zone507, unless discharged as stream504. Stream501may, for example, consist mostly of calcium carbonate or calcium oxide, and may also consist in part of aqueous solutions such as liquid water. Stream505is the solid feedstock which becomes fluidized in the turbulent or transport fluidization regime and it also enters the system above the distribution plate506. Stream505may, for example, consist mostly of calcium oxide or calcium carbonate and may also consist in part of liquid or gaseous water. The distribution plate506is designed to prevent backflow of any solids into the fluidization gas entry zone513. Solid material505, any associated reaction products and any steam generated from liquid water content present in the system are carried out of the bubbling bed507and transported through the reactor freeboard zone508. The resulting mixed stream of fluidization gases and solids is mixed-stream509, and after leaving the reactor freeboard zone508, the stream509is sent to a cyclone511, to separate the solids512, from the gases510. The fluidization gas502, is blown into the fluidization gas entry zone513, of the fluidized bed reactor500. This fluidizing gas502, could be partially recycled from the gas stream510leaving the cyclone511. The heat tube componentry554is positioned away from the vessel wall of system500, and instead is protruding across a substantial portion of the cross section of the bubbling bed zone507. In this implementation, any portions of either the sensible heat or heat from the hydrating reaction, which is not consumed to heat the pellets and supply the enthalpy to bring the pellets to the operating temperature of the fluid bed, is used instead to make saturated steam for subsequent superheat and power generation. In this implementation, The high temperature hydrator system500is built with heat tubing componentry554which protrudes across a substantial portion of the cross section of the bubbling bed zone507. During operation of system500, a stream555which could be for example, boiler feed water another appropriate heat exchange fluid, or another process fluid stream, is fed into the tube componentry554, where the heat from the fluidized bed zone507moves through the tubes and into the contents of stream555as they move through the tubes. In some aspects, stream555is boiler feed water and this indirect heating converts the boiler feed water into saturated steam that leaves the tube componentry as stream556. In some aspects, the saturated steam from these tubes is sent as stream556to downstream heat consumers or power producers, for example other process heat exchangers or a steam superheater unit and/or steam turbine.

Referring toFIG.6, calcium oxide conversion to calcium hydroxide in the presence of a fluid bed is described with respect to illustrative system600. In some implementations, system600may include feed ports for streams601,602, and605and fluidly coupled to the main system600, and a discharge port for stream604fluidly coupled to the main system600. In some aspects a gas distribution plate606may be fluidly coupled to the main vessel body of system600. In some aspects system600may include a cyclone611fluidly coupled to feed ports for stream609and discharge ports for streams612,610. In some aspects system600may be fluidly coupled to an external fluidized bed system660, including discharge ports fluidly coupled to the external fluidized bed system660for streams621,665and feed ports for stream620and663. In some aspects system600may be fluidly coupled to a feed port for stream665. In some aspects, the external fluidized bed system660may be fluidly coupled to heat tubing componentry668and system660and heat tubing componentry668may also be fluidly coupled to a feed port for stream661and a discharge port for stream664. In some aspects system600may include a control system999coupled to the components (illustrated or otherwise).

In some implementations, fluidization gases include, for example, air, steam, and the like. As depicted inFIG.6, gaseous stream602including one or more fluidization gases is provided to the hydrator system600through the bottom entry zone613, also known as the plenum chamber, which is below the fluidization distribution plate606. Gaseous stream602may be, for example, air, steam or a combination of these gases and their sub-components. Stream601is one of the solid feedstocks, which enters the system above the fluidization distribution plate606and becomes fluidized in the bed or bubbling bed regimes within the fluidized bed system600and as such it remains in the bubbling bed zone607, unless discharged as stream604. Stream201may, for example, consist mostly of calcium carbonate or calcium oxide, and may also consist in part of aqueous solutions such as liquid water. Stream605is the solid feedstock which becomes fluidized in the turbulent or transport fluidization regime and it also enters the system above the distribution plate606. Stream605may, for example, consist mostly of calcium oxide or calcium carbonate and may also consist in part of liquid or gaseous water. The distribution plate606is designed to prevent backflow of any solids into the fluidization gas entry zone613. Solid material605, any associated reaction products and any steam generated from liquid water content present in the system are carried out of the bubbling bed607and transported through the reactor freeboard zone608. The resulting mixed stream of fluidization gases and solids is mixed-stream609, and after leaving the reactor freeboard zone608, the stream609is sent to a cyclone611, to separate the solids612, from the gases610. The fluidization gas602, is blown into the fluidization gas entry zone613, of the fluidized bed reactor600. This fluidizing gas602, could be partially recycled from the gas stream610leaving the cyclone611. An indirectly heated external fluidized bed system660is connected to system600such that material from the bubbling bed607can be discharged to the external fluidized bed system660and after being processed in660, the material can be sent back to system600. The separate fluidized bed vessel660may include componentry such as heat tubing668, heat exchange medium entering the heat tubing668as stream661and leaving as stream664, a densely fluidized bed667, and a fluidization gas stream663.

In some implementations, system660is operated under significantly higher density bed conditions so that heat tubing668can be densely packed within the vessel660and come in close contact with the fluidized pellet bed667.

In some implementations, the pellets from the bubbling bed zone607of the main high temperature hydrator vessel600may be moved back and forth between vessel660and vessel600in order to exchange heat from vessel600to vessel660and its componentry, for example the heat tubing system668.

In some implementations, steam generation may be split between the high temperature hydrator system600and the external dense fluidized bed vessel660. In this implementation, a portion of the discharged stream604would feed into system660as stream620. Both boiler feed water heating and steam generation could occur within the tubing668, and the resultant cooled pellet material is transferred back to system600via stream665. In some aspects, the heat exchange occurring within system660is such that stream665is cooled to below 300° C. and is recycled to the bubbling bed zone607. In some aspects, sending the cooler stream665back to system600allows for control of temperature within system600.

In some aspects, there is another portion of stream604that does not feed into system660, but instead leaves as stream621. This stream621could be sent to downstream processing, for example to a fluidized calciner unit as part of a direct air capture system.

In some implementations, system600might be configured such that it produces a low bed-side heat transfer film coefficient. This, combined with heat transfer surface mechanical limitations, for example, a low heat tube surface area to bed surface area ratio, might not allow for full heat extraction from the bubbling bed zone607in system600.

In some aspects heat coils are used inside system600, where the heat coils are as illustrated inFIGS.5A and5B. In some of these cases, the fluid in the streams feeding the heat coils is boiler feed water and the temperature of the boiler feed water, may not provide enough of a differential temperature drive to overcome the above mentioned mechanical surface area limitations (that result in a low approach temperature requirement). In these cases, the use of an external densely fluidized bed system such as660as illustrated inFIG.6, would utilize a lower fluidization velocity (resulting in a denser bubbling bed, for example) in comparison to the bubbling bed in system600, and as such should have both a higher surface area ratio and bed-side coefficient to overcome the low boiler feed water approach temperature requirements.

FIG.7illustrates how a high temperature hydrator may, for example, be connected to other processes such as a direct air capture process. In some implementations, the direct air capture (DAC) process is configured to capture dilute concentrations of carbon dioxide from the atmosphere and produce a concentrated liquid or gaseous stream of carbon dioxide which can be utilized in applications such as Enhanced Oil Recovery (EOR), as feedstock for the production of synthetic hydrocarbons. In some cases, the concentrated liquid or gaseous carbon dioxide can instead be sequestered in a subsurface saline aquifer, reservoirs or aging oil fields as part of the previously mentioned EOR process. In some cases, the concentrated liquid or gaseous stream of carbon dioxide may instead be combined with other chemical feedstock, for example hydrogen, and further processed into a synthetic hydrocarbon such as diesel, gasoline and waxes.

In some implementations, the DAC process operates as a continuous, closed-loop system that inputs water, energy and small material make-up streams, and delivers highly concentrated, pressurized carbon dioxide.

Some examples of major process equipment involved in an implementation of this type of direct air capture commercial process include air contactors, fluidized bed reactive crystallizers also known as pellet reactors, oxy-fired circulating fluidized bed calciners, and some types of lime slakers or hydrators. Auxiliary equipment also involved in this type of direct air capture process may include, for example, compressors, turbines, boilers, heat exchangers, steam systems and oxygen production units such as Air Separation Units (ASU) or a variety of water electrolyzer units.

In some implementations, the DAC process draws air through an air contactor, where it contacts a strong aqueous hydroxide solution, such as potassium hydroxide (KOH). The carbon dioxide in the air reacts with the potassium hydroxide to form a solution of potassium carbonate (K2CO3) and water, absorbing about three-quarters of the available carbon dioxide.

In some implementations, the DAC process potassium carbonate solution is transferred to a fluidize bed reactive crystallizer or pellet reactor. In some aspects the fluidized bed reactive crystallizer or pellet reactor is a liquid-solid fluidized bed, where the potassium carbonate solution can contact calcium hydroxide (Ca(OH)2), also known as hydrated lime, and precipitate calcium carbonate pellets through a process known as causticization.

In some implementations, the DAC process calcium carbonate pellets from the fluidized bed reactive crystallizer pass through a slaker to absorb heat before being fed into a circulating fluidized bed calciner, which is essentially a type of high-temperature kiln or furnace. The heat releases the carbon dioxide as a highly concentrated, gaseous stream, leaving calcium oxide (CaO) as by-product, through a process known as calcination. In some aspects, heat for the calciner is provided by combusting natural gas with oxygen (known as “oxy-firing”), so that the combustion exhaust may contain mostly carbon dioxide with some water, and can be combined with the carbon dioxide stream leaving the calciner. In some aspects the oxygen used for oxy-firing is separated from air using an air separator.

In some implementations of the DAC process, the calcium oxide is fed into the slaker, where it may combine with steam to regenerate hydrated lime, which can then be fed into the fluidized bed reactive crystallizer or pellet reactor for reuse. In some aspects, the slaker may be configured as a high temperature hydrator.

In some implementations, at least a portion of the electrical power for the DAC process derives from on-site generation. In some aspects, the on-site power generation uses natural gas as fuel, or from external, grid-supplied renewable electricity sources. In some aspects, some of the DAC process electrical power is generated on-site using waste or excess steam, for example from the calciner or high temperature hydrator.

FIG.7does not show all the major equipment involved in a direct air capture process, rather, it illustrates one embodiment of how the key interfaces, for example heat and material stream exchanges, could be set up between a high temperature hydrator system and the immediate upstream and downstream process and heat exchange equipment of a direct air capture process. In the implementation illustrated inFIG.7, calcium carbonate pellets, which may have been processed upstream to remove process solution, are fed, slightly wet, via stream700to the high temperature hydrator unit740. In some aspects the direct air capture process may include a control system999coupled to the components (illustrated or otherwise).

The wet calcium carbonate pellets in stream700, and hot calcium oxide (quicklime) in stream710that originated from the calciner system800, are both fed into the high temperature hydrator unit740and mixed. The high temperature hydrator740is fluidized by recirculating steam, as stream705. In some aspects, a portion of the steam stream705takes part in the slaking reaction that converts the feed stream of calcium oxide material in stream710into calcium hydroxide material.

The calcium carbonate pellets in stream700that are fed into the high temperature hydrator unit740do not participate in the slaking reaction; instead, they are dried and heated using the process heat within the high temperature hydrator unit740. The calcium oxide in stream710is delivered at a temperature of approximately 694° C. The calcium oxide stream710may include, for example, approximately 94.5% reactive calcium oxide, 3.4% unreactive calcium oxide, and 2.1% impurities.

A stream of mostly preheated and dried pellets are drawn out of the bubbling bed zone of the high temperature hydrator unit740and sent as stream708to the solid sieve unit760to separate the solids into a stream of larger pellets, stream719, and any smaller particles, such as calcium oxide and calcium hydroxide, as stream709. The larger solids in stream719can be fed to the calciner preheat cyclone system790at an approximate temperature of 300° C.

The calcium hydroxide solid particles can be separated from the calcium carbonate pellets due to a substantial size difference between the small, micron sized calcium hydroxide particles and the larger, millimeter sized calcium carbonate pellets. The calcium hydroxide will therefore pass through the solid sieve unit760, which may for example have a mesh with 0.8 mm diameter holes, while the pellets, being larger, will not pass through the holes in the mesh and will instead move along the top of the mesh and out a separate exit. Any unreacted calcium oxide present in the feed stream to the solid sieve unit760will, depending on size, either recycle back to the calciner unit800with stream719or continue onto the cooler unit750in stream711, where it has another opportunity to react with water, in a hydration reaction, to form calcium hydroxide.

After passing through the high temperature hydrator unit740, the steam stream701may be further cleaned of solids using for example a cyclone unit765and a baghouse unit770, then recirculated back to the inlet gas distributor, or “windbox,” of the high temperature hydrator unit740using a high temperature blower820.

Any solid material that passes the primary cyclone of the high temperature hydrator unit740will be fine particles that may be captured further downstream by a cyclone unit765, leaving this unit as stream706or even further downstream in a baghouse unit770, leaving this unit as stream707.

In some implementations, a portion of the calcium carbonate pellets may be small enough to transport along with the circulating material and as such, wind up in any one or a combination of streams706,707, and709. Depending on the amount of calcium carbonate pellet material present in these streams, this may introduce a form of dead load propagating forward into downstream processes within the system. This dead load can be mitigated by including, for example, one or more hot sieve screens to process at least a portion of one or both of streams706and707to capture the calcium carbonate material and direct it over to the calciner system800.

In some implementations, all three streams706,707, and709, could be combined into stream711and sent to a cooler unit750, where they are cooled using water from streams715and718. In some aspects, cooling unit750is built with a cooled screw, where stream718is boiler feed water from a steam condenser unit745that flows through an internal cavity in the screw, allowing for indirect cooling of the contents of the cooling unit750. This screw may mix stream711with a water stream715. In some aspects, stream711may include for example unreacted calcium oxide, which as a result of mixing in cooling unit750with stream715, could react via the hydrating reaction to produce calcium hydroxide. In some aspects, unit750also allows some heat from stream711and some heat resulting from any hydrating reaction to transfer indirectly to the boiler feed water stream718, providing a further preheated stream712of boiler feed water that can then be sent to the high temperature hydrator unit740for conversion into saturated steam stream703.

In some implementations, the cooler unit750carries out two functions: a) it cools exiting stream716to below 100° C. so that it can be safely mixed with water in mixing tank755to form the required Ca(OH)2slurry and b) it provides for a small amount of water (stream715) to be sprayed onto the solid Ca(OH)2to complete the remaining slaking reaction.

In some implementations, after leaving the cooler unit750, the Ca(OH)2stream716is sent to the mixing tank755, where it is formed into a slurry mix using a water source (stream714). This slurry mix could be, for example, diluted with water to a slurry having a consistency of between 20 wt % to 40 wt % solids. In some aspects, the water source may be for example potable, non-potable, process water knocked out from on-site compressor units, recovered from washing systems or other process units.

In some implementations, the cooled Ca(OH)2that is now retained within unit755can be sent further downstream to other processes that require the use of hydrated lime in either solid Ca(OH)2form or a wetter slurry form. Examples of some types of downstream processes that may be fed from stream717include the pellet reactor units found within some types of carbon dioxide capture processes such as direct air capture, water treatment facilities, and caustic recovery units within the Kraft pulp and paper process.

In some implementations, the heat generated in the high temperature hydrator740may not be fully consumed in the process of drying and preheating the pellets. The excess heat could be used to generate steam, which could then be use for example for other process heat requirements or for power production via stream703, which in the implementation shown inFIG.7, feeds into a steam superheater unit785. In other aspects, the excess heat from the high temperature hydrator740could be removed from unit740by means of direct exchange with internal fluids within unit740that then leave the unit and are fed through downstream heat exchangers (not shown). In other aspects, the excess heat from the high temperature hydrator unit740could be removed by means of indirect exchange with heating tubes or coils located either within the vessel walls of740as shown inFIG.7, or for example by heat tubes or coils located further into the bubbling bed zone of unit740as illustrated inFIG.5B, or via a separate external fluidizing vessel as illustrated inFIG.6.

In some aspects, the oxy-fired calciner800is a circulating fluidized bed, which is fluidized with a flow of pure oxygen shown in the process flow diagram ofFIG.7as stream723.

The calciner800is used to decompose the calcium carbonate (CaCO3) pellets from stream719into calcium oxide (CaO) and carbon dioxide at a temperature of approximately 900° C. High temperature is required to drive the endothermic calcination reaction to the desired 98% conversion of calcium carbonate to calcium oxide.

The hot pellets from the high temperature hydrator740are sent to the calcination system via stream719by way of two consecutive cyclone preheat stages (790followed by795) to raise the temperature of the pellets further before entering the calciner unit800via stream721.

Hot gas from the calciner unit800output stream725(primarily carbon dioxide), is fed to preheating cyclone stage795at approximately 900° C., and then via stream726to preheat cyclone stage790at approximately 650° C. The gas stream727is then extracted from the calciner unit800and may be sent through coolers such as unit785before being sent to clean-up units such as775and compression unit815.

The gas leaving the calciner800in stream727contains all the carbon dioxide from the calcination of the pellets. In some implementations where for example natural gas combustion is used as the heat to drive the endothermic calcination reaction, stream727would also contain the carbon dioxide from the combustion of natural gas. In some aspects, the composition of this gas stream727is 82.8 wt % CO2, 14.6 wt % H2O, 1.13 wt % O2, and 1.43 wt % N2.

In some aspects, a small amount of the calciner800off-gas (primarily carbon dioxide) is re-circulated back into the system through stream734after passing the last cooling unit785, but before the water vapor has been removed. This stream can be used as a supply for various minor fluid bed requirements such as instrument purges, and to aid the circulation of the solids from the primary cyclone795back into the main calciner bed. This can be done with air but recycled carbon dioxide is used in this implementation instead to prevent dilution of the calciner off-gases with nitrogen.

The stream739of remaining hot solid reaction product leaving calciner unit800—which includes for example mostly quicklime or calcium oxide (CaO)—may be used to preheat the incoming oxygen feed stream722via a heat exchange unit805before being sent to downstream cooling and/or processing units. This solid calcium oxide product from the calcination reaction is shown as stream739inFIG.7. In some implementations, the very hot material in stream739may be close-coupled to the high temperature hydrator unit740to avoid an expensive transport device. This may also require, for example, a grade level high temperature hydrator pellet screen with a vertical 300° C. pellet pneumatic transport to carry the pellet feed (stream719) to the calciner pre-heat cyclone790. In some aspects it is desirable to minimize, for example, capital expense and operational difficulties of this configuration; in this case, a portion of the supplemental (in addition to feed pellet water) reactive steam (stream729), could be diverted as a slipstream and used for the pneumatic transport of stream719to the pre-heat cyclone790, before being returned to the recirculation stream704(not shown).

In some aspects, unit805could be a bubbling fluidized bed. In some aspects where unit805is a bubbling fluidized bed, the hot calcium oxide in stream739from the calciner unit800is fluidized by the oxygen stream722, which could transfer heat directly from the calcium oxide stream739to the oxygen stream722. This could raise the temperature of the oxygen stream722from ambient to approximately 700° C. in stream723. In some aspects this bubbling fluid bed805may be refractory lined, suitable for service with high temperature oxygen, and completely gas-tight to prevent release of oxygen from the system.

In some aspects, the heat for the calciner unit800is supplied by combustion of natural gas fed from stream724.

The heat for the calcination endothermic reaction could be provided from a variety of sources, depending on the economics and resources associated with the location of a particular commercial plant. In an example aspect, the heat source is electric. In another example aspect, the heat source is combustion of a hydrocarbon such as natural gas. In another example aspect, the heat source is solar or solar thermal. In another example aspect, the heat source is combustion of biomass. In yet another example aspect the heat source is combustion of hydrogen.

Oxygen for the calciner unit800is provided via stream722. In some aspects, the oxygen stream722is supplied by an air separation unit (ASU) which may for example operate at a pressure of approximately 20 kPag. In other aspects the oxygen source for stream722may be a by-product of water electrolysis.

In some implementations, the high temperature hydrator unit740may be built as a refractory lined circulating fluidized bed, or CFB. In some aspects, the fluidization velocity in the high temperature hydrator is chosen such that the calcium carbonate pellets remain as a fluidized bed in the bottom of the device while smaller calcium oxide particles recirculate through the primary cyclone and loop seal that are shown as being integral to unit740inFIG.7and which are called out in more detail inFIG.3B. As the calcium oxide particles are transported around the high temperature hydrator740, they may react with the steam and slake to form Ca(OH)2and, as a result of this reaction, heat may be released. The sensible heat of the circulating calcium oxide material, fluidization gases, and the heat from the hydrating reaction contribute to heating the calcium carbonate pellets in the bubbling bed zone up to 300° C. The heated and dried pellets (708) are drawn out of the bubbling zone of the high temperature hydrator unit740and sent to downstream processes. Any fine material which passes the primary cyclone of the high temperature hydrator unit740may be, for example, Ca(OH)2and could be captured by the cyclone (765) and/or baghouse (770) units. These units may be used If the downstream high temperature fluidization fan (820) is not able to withstand the small amount of solids in the recirculating steam stream704. All three streams of hydrated lime (706,707,709) may be combined as stream711and sent to another unit in the process, for example a cooling unit750as illustrated inFIG.7.

In one aspect, heat generated in the high temperature hydrator unit740shown inFIG.7may not be fully consumed in drying and preheating the calcium carbonate pellets; in this case, the excess or waste heat could be used to generate steam for other heat or power requirements. One example of how this could be done is illustrated inFIG.7, where superheated steam stream703is produced indirectly by flowing boiler feedwater as part of stream712through a set of heating coils imbedded in the high temperature hydrator unit740. This steam leaves the high temperature hydrator740as stream703, is sent to a steam superheater unit785where it is further heated and then used to feed a steam turbine780.

In another implementation, the high temperature hydrator unit740as illustrated inFIG.7may be operated such that the fluidization velocity within this unit740is set as high as possible while keeping the calcium carbonate pellets in a bubbling fluidized bed mode. In an example aspect, this fluidization velocity is set to 0.75 m/s. At This velocity, the calcium oxide will be elutriated out of the bed, captured by the primary cyclone and re-introduced back into the bed via the recirculation leg. In some aspects this recirculation leg may be as shown inFIG.4Band may include for example a loop seal. In this implementation the calcium oxide material could behave as a circulating fluid bed while the calcium carbonate pellets behave as a back mixed bubbling fluid bed. There is a recirculating flow of steam, stream705, which is used to fluidize the bed. Upon leaving the high temperature hydrator unit740, the steam stream701goes through a dust collection system, which may include for example a baghouse unit770and/or cyclone unit765to remove any calcium oxide and calcium hydroxide particles from the steam stream before being sent to a high temperature fan820which then boosts the stream pressure for reintroduction into the fluidized bed.

In some implementations, in addition to any water carried into the high temperature hydrator unit740along with the pellet stream700, some additional steam is necessary to convert 85% of the quicklime to hydrated lime via the hydrating reaction,
CaO(s)+H2O(g)→Ca(OH)2(s)+105.2 kJ

In some aspects of this implementation, the additional steam can be provided by pulling a low pressure steam stream729off of a turbine780(as shown inFIG.7) and injecting this stream729into the fluidizing steam flow after it has passed through the high temperature baghouse unit770. In some other aspects, the additional water needed to complete the above hydrating reaction could be directly injected into streams704or705as liquid water (not shown).

The choice between feeding water into the recirculating steam loop and using low pressure steam from the steam turbine780is determined by the economic trade-off between the additional energy generated by having the extra steam flow through the steam turbine780, and the additional capital and operating costs of generating extra boiler feed water and processing the extra steam.

A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims. Further modifications and alternative embodiments of various aspects will be apparent to those skilled in the art in view of this description. Accordingly, this description is to be construed as illustrative only. It is to be understood that the forms shown and described herein are to be taken as examples of embodiments. Elements and materials may be substituted for those illustrated and described herein, parts and processes may be reversed, and certain features may be utilized independently, all as would be apparent to one skilled in the art after having the benefit of this description. Changes may be made in the elements described herein without departing from the spirit and scope as described in the following claims.