Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/34—Chemical or biological purification of waste gases
  • B01D53/46—Removing components of defined structure
  • B01D53/62—Carbon oxides
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/34—Chemical or biological purification of waste gases
  • B01D53/46—Removing components of defined structure
  • B01D53/48—Sulfur compounds
  • B01D53/50—Sulfur oxides
  • B01D53/508—Sulfur oxides by treating the gases with solids
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/34—Chemical or biological purification of waste gases
  • B01D53/96—Regeneration, reactivation or recycling of reactants
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
  • B01J20/04—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising compounds of alkali metals, alkaline earth metals or magnesium
  • B01J20/041—Oxides or hydroxides
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
  • B01J20/04—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising compounds of alkali metals, alkaline earth metals or magnesium
  • B01J20/043—Carbonates or bicarbonates, e.g. limestone, dolomite, aragonite
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/30—Processes for preparing, regenerating, or reactivating
  • B01J20/34—Regenerating or reactivating
  • B01J20/3433—Regenerating or reactivating of sorbents or filter aids other than those covered by B01J20/3408 - B01J20/3425
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/30—Processes for preparing, regenerating, or reactivating
  • B01J20/34—Regenerating or reactivating
  • B01J20/3483—Regenerating or reactivating by thermal treatment not covered by groups B01J20/3441 - B01J20/3475, e.g. by heating or cooling
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/30—Processes for preparing, regenerating, or reactivating
  • B01J20/34—Regenerating or reactivating
  • B01J20/3491—Regenerating or reactivating by pressure treatment
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
  • C01F11/00—Compounds of calcium, strontium, or barium
  • C01F11/02—Oxides or hydroxides
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2251/00—Reactants
  • B01D2251/40—Alkaline earth metal or magnesium compounds
  • B01D2251/404—Alkaline earth metal or magnesium compounds of calcium
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2257/00—Components to be removed
  • B01D2257/30—Sulfur compounds
  • B01D2257/302—Sulfur oxides
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2257/00—Components to be removed
  • B01D2257/50—Carbon oxides
  • B01D2257/504—Carbon dioxide
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02C—CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
  • Y02C20/00—Capture or disposal of greenhouse gases
  • Y02C20/40—Capture or disposal of greenhouse gases of CO2
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P20/00—Technologies relating to chemical industry
  • Y02P20/10—Process efficiency
  • Y02P20/129—Energy recovery, e.g. by cogeneration, H2recovery or pressure recovery turbines
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P20/00—Technologies relating to chemical industry
  • Y02P20/151—Reduction of greenhouse gas [GHG] emissions, e.g. CO2

Definitions

• Exemplary embodiments relate to elimination in pollutants from flue gas stream. More specifically, exemplary embodiments relate to reactivation of a sorbent for elimination of pollutants from a flue gas stream.
• Zeeman et al. have integrated the hydration process as a reactivation step in the CO 2 removal process. They hydrate the sorbent at 300° C in the presence of CO 2 and steam at atmospheric pressure. There has been no mention about the extent of hydration achieved by this process and the amount of carbonation occurring during the hydration process. Although this method was found to reduce sintering and reactivate the sorbent a steady decline in the reactivity of the sorbent was still observed.
• Embodiments of the present invention detail a process for the efficient capture of CO 2 and sulfur from combustion flue gas streams and gasification based fuel gas mixtures using regenerable and recyclable calcium based sorbents.
• the solid sorbent is predominantly a meatl oxide that can be converted into a hydrate.
• Exemplary embodiments specifically provide a method of reactivating the sorbent by hydrating it at a high temperature of 600° C and a pressure higher than 6 bars to lower the parasitic energy consumption of the process.
• hydration occurs at temperatures high enough such that heat generated from exothermic reaction can be extracted to generate steam for a steam turbine or used for heat exchange; minimum of at least 300° C and greater for steam turbine integration.
• process efficiency increases, but hydration must operate at pressures greater than 1 atm.
• temperatures between about 300° C to about 500° C hydration may occur at about 1 atmosphere. More specifically, temperature from between 350° C and about 512° C.
• Figure 1 is an illustration of an exemplary embodiment of a carbonation calcination reaction process for CO 2 removal from combustion flue gas.
• Figure 2 is a schematic diagram of the calcium looping process for hydrogen production used with exemplary embodiments of the present invention.
• Figure 3 is an illustration of an exemplary embodiment of a pressure hydrator.
• Figure 4 is a diagram of an exemplary embodiment of the carbonation calcination reaction process in a cola fired power plant.
• Figure 5 is a diagram of an exemplary embodiment of a combined hydration dehydration reactor for sorbent reactivation.
• Figure 6 is another exemplary embodiment illustrating the integration of the carbonation calcination reaction ("CCR") process in a coal fired power plant.
• Figure 7 is another exemplary embodiment illustrating the integration of the CCR process in a coal fired power plant.
• Figure 8 is another exemplary embodiment illustrating the integration of the CCR process in a coal fired power plant.
• Figure 9 is another exemplary embodiment illustrating the integration of the CCR process in a coal fired power plant.
• Figure 10 is a diagram of a thermo gravimetric analyzer.
• Figure 1 1 is a diagram of an integral fixed-bed reactor setup.
• Figure 12 is a photo of the rotary calciner experimental setup.
• Figure 13 is a photo of a sub-pilot plant demonstration of the CCR process for CO 2 and SO 2 capture.
• Figure 14 is a comparison in the CO 2 capture capacity of calcium oxide sorbents obtained from different precursors.
• Figure 15 illustrates the effect of steam calcination on the reactivity of the sorbent.
• Figure 16 illustrates the effect of the number of cycles on the capture capacity of the sorbent.
• Figure 17 illustrates the effect of water hydration on the CO 2 capture capacity of the sorbent.
• Figure 18 is a comparison of the extent of reactivation by water and steam hydration.
• Figure 19 is a thermodynamic plot for the hydration and carbonation reactions.
• Figure 20 illustrates the effect of pressure hydration on the capture capacity of the sorbent.
• Figure 21 illustrates the percent CO 2 removal versus Calcium :Carbon mol ratio for multiple sorbents.
• Figure 22 illustrates the percent of CO 2 removed versus
• Figure 23 illustrates sulfur dioxide removals as a function of calcium :carbon mol ratio for multiple calcium-based sorbents.
• Figure 24 illustrates the effect of residence time on CO 2 removal.
• Figure 25 illustrates CO 2 removal versus cycle number for calcium hydroxide and lime.
• Figure 26 illustrates multi-cyclic CO 2 capture capacity for Atmospheric
• Pressure hydration of high calcium content oxides is conducted at temperatures equal to or higher than that used for the dehydration reaction to improve the quality of the heat generated by hydration (for example, at about 300 psi, the hydration temperature is about 600° C) and making it possible to use this energy for the dehydration reaction.
• An illustration of the CCR process for CO 2 capture from combustion flue gas is provided in Figure 1.
• the sorbent mixture consisting of recycled as well as fresh calcium sorbent is fed to a calciner 1 where it is calcined at 950° C.
• the resultant lime is conveyed to a pressure hydrator 2 where steam and the lime react to produce Ca(OH) 2 .
• the Ca(OH) 2 is dehydrated to form CaO either in a separate dehydration reactor (not shown in Figure 1 ) or in the carbonation reactor 3 where the CaO reacts with the flue gas to form CaCO 3 and
• SO 2 may be independently removed prior to CO 2 removal.
• the sorbent from the carbonation reactor is then conveyed back to the calciner 1 and the process is continued.
• the exemplary embodiments use pressure hydration of high calcium content oxides to improve the quality of the heat generated by hydration (for example, at 300 psi, the hydration temperature is 600° C) and lower the energy penalty associated with the sorbent enhanced WGS Reaction .
• An illustration of the calcium looping process is shown in Figure 2. The
• Ca(OH) 2 along with the syngas is fed to the carbonation reactor 30 which is operated at 600° C.
• the Ca(OH) 2 decomposes at 600° C to form steam and CaO.
• the steam reacts with the CO in syngas to form CO 2 and H 2 while the CaO captures the CO 2 , sulfur and halide impurities. Since all the steam required for the water gas shift reaction is supplied by the decomposition of Ca(OH) 2 no excess steam needs to be added to the carbonation reactor 30.
• the carbonated sorbent is then regenerated in the calciner 10 to form CaO and a sequestration ready CO 2 stream if operated below the decomposition temperature of CaSO 4 .
• calciner 10 operating temperatures may be lowered with the addition of diluted gas that can be separated from CO 2 , such as steam.
• the heat for the calciner 30 may be provided through indirect-fired, oxyfule fired with natural gas, coal, or other fossil fuels.
• the regenerated sorbent is then injected into a hydrator 20 where it is converted to Ca(OH) 2 in the presence of steam at high pressures and temperatures.
• the reactivated Ca(OH) 2 sorbent is then reinjected into the carbonation reactor 30 and the cycle is continued.
• the WGS reaction approaches nearly 70 to 90% conversion to H 2 at one atmosphere pressure.
• reaction in the hydrator is:
• the lime removes the carbon dioxide from the reaction system permitting more hydrogen to be formed. These same reactions at greater than 5 atmospheres pressure (about 75 psi) achieve nearly 99% hydrogen purity.
• Table 1 Comparison of Pressure and Atmospheric Hydrated Lime [0070] The data in Table 1 indicate that hydration results in the increase in
• FIG. 3 depicts the design of a pressure hydrator 100 in which the powdered sorbent is pumped into the hydrator 100 which is maintained at high pressure. Steam at high pressure is also fed into the hydrator 100 which has a paddle mixer 50 to promote mixing of the solids with the steam. The hydrated sorbent then exits the hydrator through a lock hopper 60.
• Figure 4 illustrates an exemplary embodiment of the integration of the
• the pure CO 2 108 produced in the kiln 700 is cooled and compressed for transportation 1 10 to the sequestration site.
• the calcined sorbent 107 is cooled down from >900° C to 600° C and fed 109 into the sorbent reactivation reactor 760 shown in more detail in Figure 5.
• the high quality heat obtained from the reheat boiler 1 19 and from cooling the solids and the CO 2 is used to generate steam 122 for additional electricity production or to supply the parasitic energy requirement of the process.
• Steam 1 1 1 is fed into the sorbent reactivation reactor 760 which is shown in Figure 5.
• the reactivated calcium oxide sorbent 1 12 is then fed to the carbonation reactor 740.
• Flue gas generated from burning coal 1 14 in the primary boiler 740 in addition to the flue gas 1 13 generated in the reheat boiler 720 is fed to the carbonation reactor 780 where 99% of the CO 2 and SO 2 in the flue gas are removed by the calcium oxide sorbent.
• the exothermic energy 120 produced in the carbonator 780 is used to generate additional electricity.
• the flue gas is separated from the sorbent and emitted into the atmosphere 1 16. About 1 -5% of the sorbent is purged to waste 1 18 and the rest is recycled back103 to the kiln 700 and the whole process is repeated.
• FIG. 5 depicts an exemplary embodiment of a pressure hydration system 760 which is energy efficient and reduces the parasitic energy requirement of the coal to electricity system.
• pressure hydration unit 902 can be combined with atmospheric dehydration unit 904 to recover the hydration energy.
• the calcium oxide from the calciner 700 is fed into the hydration system 760 along with steam.
• the hydration system consists of two concentric cylindrical reactors 902 and 904.
• the inner reactor 902 is a pressurized vessel where hydration occurs at pressures above 6 bar and at a temperature of 600° C.
• the CaO reacts with the steam to produced calcium hydroxide which is separated from steam and gravity fed to the outer reactor 904.
• the outer concentric reactor 904 is at ambient pressure and the sorbent at 600° C undergoes dehydration to form CaO.
• the exothermic heat generated in the inner concentric reactor 902 from the formation of Ca(OH) 2 is transferred to the outer reactor 904 where it supplies the endothermic energy required for the dehydration reaction.
• the calcium oxide sorbent produced from the hydration-dehydration reactor 760 is then fed into the carbonator 740 along with the flue gas.
• FIG. 6 depicts another exemplary embodiment for the integration of the CCR process in a coal fired power plant.
• the Calcium oxide 209 produced in the kiln 700 is fed into the pressure hydrator 800 along with steam 21 1 to form Ca(OH) 2 .
• the Ca(OH) 2 212 produced in the hydrator 800 is then directly fed into the carbonator 780 where it simultaneously dehydrates and captures the CO 2 and SO 2 from the flue gas.
• the endothermic energy for the dehydration reaction is obtained from the exothermic energy released by the carbonation.
• both the carbonator 780 and the pressure hydrator 800 are exothermic and the high quality (600° C) heat produced 220 and 223 are used to generate additional electricity.
• the pressure hydrator 800 may be a simple fixed, fluidized or moving bed reactor and the need for a separate reactor of dehydration is obviated.
• FIG. 7 illustrates another exemplary embodiment for the integration of the CCR process in a coal fired power plant.
• the hydration and dehydration of the sorbent is conducted in two separate reactors 800 and 820 and the heat is transferred from the hydrator 800 to the dehydrator 820 by a working fluid.
• the calcined sorbent 309 from the calciner 700 is fed into the hydration reactor 800 with steam 31 1 where they are mixed together at a pressure above 6 bar pressure and a temperature of about 600° C. This causes the calcium oxide to hydrate liberating heat which is absorbed by a working fluid.
• the hydrated lime 323 is reduced in pressure to 1 atmosphere and conveyed to the dehydration reactor 820 where the 600° C hydrate begins to dehydrate and the endothermic energy required for the dehydration reaction is provided by the working fluid.
• the CaO sorbent 312 from the dehydrator 820 is then fed into the carbonation reactor 780 for the capture of CO 2 and SO 2 from the flue gas.
• Figure 8 illustrates an exemplary embodiment of heat integration for a coal fired power plant with CO 2 capture using the CCR process.
• Flue gas 405 from the reheat boiler 720 provides the calcination energy and is sent back 408 through the reheat boiler 420 to be heated up further and fed 410 into the primary boiler 740. This is an innovative method of recovering the heat generated in the reheat boiler 720 and producing additional electricity.
• Figure 9 illustrates an exemplary embodiment of integration of CO 2 removal by the calcium looping process in a traditional gasification system.
• Syngas 505 from the gasifier 840 is fed to the carbonator 780 along with steam 506 from the HRSG and Ca(OH) 2 507 from the hydrator 800.
• the Ca(OH) 2 dehydrates in the carbonator 780 providing steam required for the water gas shift reaction and CaO for the removal of CO 2 , sulfur and halide impurities.
• the insitu removal of CO 2 during the water gas shift reaction improves the yield of hydrogen produced and the product hydrogen stream 510 is cooled down 524 and used as a fuel, to produce electricity, liquid fuels or chemicals.
• a portion of the sorbent stream from the carbonator 780 is purged and a make up of fresh limestone 512 is added before entering the calciner 700.
• the energy for the calcination reaction is provided by combusting coal 517 in a reheat boiler 720 and using the flue gas 518 to heat the calciner 700 indirectly.
• the hot flue gas 514 from the calciner 700 is then cooled down to 600° C in a HRSG 860 and sent 523 to the carbonator 780 where the CaO sorbent reacts with the CO 2 and SO 2 in the gas during hydrogen production.
• the CO 2 514 produced in the calciner 700 is cooled in an HRSG 860 and compressed for transportation and sequestration.
• a small amount of the hydrogen 516 may also be combusted in the calciner 700 to provide heat directly and steam (which is a product of the combustion) which is a carrier gas and aids in reducing the temperature of calcination.
• the calcined CaO sorbent 519 is then reactivated by pressure hydration with steam at about 600° C and a pressure greater than about 6 bars.
• the Ca(OH) 2 507 produced is then fed directly into the carbonator 780.
• the exothermic energy 509 from the carbonation reactor 780, hydrator 800, cooling of the CO 2 , H 2 , flue gas and solids is used to produce additional electricity a part of which is used to supply the parasitic energy requirement of the process.
• the reacted sorbent that exits the carbonation reactor 780 contains calcium carbonate, calcium sulfate and unreacted calcium oxide.
• One method of operation is to send substantially all the reacted sorbent exiting the carbonator 780 to back into the calciner 700, and through the reactivation process.
• a second method of operation exists in which the reacted sorbent exiting the carbonator 780 is split into two streams. The first stream may be sent to the calciner 700 for reactivation while a second stream may be sent directly back into the carbonator 780. The two stream approach may aid in reducing the parasitic energy requirement as all the reacted sorbent need not be calcined and recycled every cycle.
• In still other exemplary hydration of the sorbent may either be done every cycle after calcination or once every few cycles depending on the extent of sintering of the sorbent.
• hydration may be conducted at temperatures between about 300° C to about 500° C and about 1 atmosphere. More specifically, between about 350° C and about 512 °C and about 1 atmosphere. Hydration at temperatures above about 300° C is sufficient such that heat generated from exothermic reaction can be extracted to generate steam for a steam turbine or used for heat exchange.
• FIG. 1 1 is an illustration of an integral fixed-bed reactor setup.
• Figure 12 is an illustration of a rotary calciner experimental setup.
• the bench scale experimental setup consists of a fixed bed reactor connected to a continuous gas analysis system and a rotary calciner connected to a CO 2 analyzer. Calcination under realistic conditions was conducted in the rotary calciner at various temperatures ranging from 800° to 1000° C. Different carrier gases such as steam and CO 2 were evaluated and a residence time of 30 minutes was maintained.
• a fixed bed reactor was used to conduct carbonation, pressure hydration and experiments for the production of hydrogen from syngas by the simultaneous water gas shift and carbonation reaction.
• the mixture of gases from the cylinders is regulated and sent into the fixed bed reactor by means of mass flow controllers.
• the mass flow controllers can handle a pressure of about 21 atmospheres.
• the steam generating unit is maintained at a temperature of 200° C and contains a packing of quartz chips which provide a large surface area of contact between the reactant gases and the water.
• the steam generating unit not only facilitates the complete evaporation on the water being pumped into the steam generating unit but it also serves to preheat the reactant gases entering the reactor.
• the reactor has been provided with a pressure gauge and a thermocouple to monitor the temperature and pressure within.
• the reactant gases leaving the reactor enter the back pressure regulator which builds pressure by regulating the flow rate of the gases.
• the pressure regulator is very sensitive and the pressure within the reactor can be changed quickly without any fluctuations.
• the back pressure regulator is also capable of maintaining a constant pressure for a long period of time thereby increasing the accuracy of the experiments conducted.
• This back pressure regulator is capable of building pressures of up to 68.9 atmospheres (1000 psig).
• the inlet of the backpressure regulator is connected to the reactor rod and the outlet is connected to a heat exchanger.
• the product gas at the exit of the heat exchanger is conditioned in a tower containing a desiccant and is sent to a set of continuous analyzers capable of determining the concentrations of CO, CO 2 , H 2 S, CH4 and H 2 in the gas stream. 5 g of the sorbent is loaded into the reactor and the pressure, temperature and gas flow rates are adjusted for each run.
• the steam free gas compositions at the outlet of the reactor are monitored continuously using the CO, CO 2 , H 2 S, CH4 and H 2 gas analyzer system described above.
• the carrier gas containing a mixture of CO 2 and steam is fed into a rotating reactor containing the solid to be calcined.
• the reactor is enclosed in a furnace and heated to the required temperature which is monitored by means of a thermocouple fixed to the reactor.
• the exit gas is conditioned and fed into a CO 2 analyzer which is used to detect the onset and completion of the calcination reaction.
• Figure 13 is a photo of a sub-pilot plant demonstration of the CCR process for CO 2 and SO 2 capture.
• An underfed stoker combusts approximately 20 pounds per hour of stoker-grade coal.
• the generated flue gas stream contains 10%- 15% carbon dioxide (CO 2 ) and approximately 5000 ppm of sulfur dioxide (SO 2 ).
• a variable-frequency Induced Draft (ID) fan located at the end of the process, pulls the flue gas stream through the ductwork. A zero-pressure point is maintained in the stoker, where the negative pressure of the ID fan is balanced by the positive pressure of the air blower, which is used as the source of oxygen for coal- combustion.
• ID variable-frequency Induced Draft
• the feed rate of the sorbent is set by controlling the revolutions per minute of the screw and obtained through correlations between the feed rate and the revolutions per minute.
• the FEECO rotary calciner is indirectly-heated via electricity and has a variable residence time between 30 minutes and 45 minutes.
• the residence time is controlled by a variable frequency drive that determines the revolutions per minute of the rotary calciner.
• the sorbent while in the calciner, can be preheated to minimize the temperature drop that occurs in the carbonator reactor.
• a double-dump valve which acts as a gas-solid separator, and an exhaust are located at the outlet of the calciner. The double-dump valve allows the pressure in the rotary calciner to be maintained without being affected by the pressure in the flue gas stream, while also allowing the solids to enter the carbonation reactor, where the sorbent contacts the flue gas stream.
• the carbonation reactor contacts the flue gas stream and the solid sorbent in the temperature range between 400° C and 750° C.
• the solid sorbent is injected in the downer of the carbonation reactor and is entrained by the flue gas stream.
• the solid sorbent simultaneously decomposes into calcium oxide (CaO, commercially known as lime) and water (H 2 O ) and reacts with both carbon dioxide (CO 2 ) and (SO 2 ) present in the flue gas stream to form calcium carbonate (CaCO 3 , commercially known as limestone) and calcium sulfate (CaSO 4 , commercially known as gypsum).
• the residence time in the entrained bed reactor can be varied between 0.3 seconds and 0.6 seconds.
• a cyclone Following the carbonation reactor is a cyclone.
• the flue gas, and any solids not captured by the cyclone report to a Torit-Donaldson down-flow baghouse, where any captured solids report to a 55-gallon drum and the particulate-free flue gas stream exits to the outside atmosphere.
• the solids captured by the cyclone then enter into the calciner.
• the calciner outlet is disconnected from the carbonation reactor and connected directly to a 55-gallon drum.
• the solids collected in the baghouse are then placed into the Schenck- Accurate hopper.
• the calciner is pre-heated to a maximum temperature of 950 C. Upon completion of heating, the solid from the carbonation reactor are fed into the calciner.
• the limestone decomposes into calcium oxide and carbon dioxide (CO 2 ). Due to the stability of the calcium sulfate, it remains as calcium sulfate in the calciner.
• the pure, dry CO 2 gas exits through the exhaust of the calciner, while the solid mixture, consisting of calcium oxide, calcium carbonate, and calcium sulfate, reports to the 55-gallon drum.
• the collected solids are then hydrated at atmospheric conditions to produce a dry hydrate, which completes the cycle.
• the dry hydrate formed is used as the feed for the next cycle.
• two sets of gas analyzers are employed.
• One set of gas analyzers is located upstream of sorbent injection and is used as the baseline.
• the other set of gas analyzers is located downstream of the sorbent injection. The difference between the two measurements determines the percent removal.
• the gas analyzers are CAI 600 analyzers and continuously monitor the concentrations of CO 2 , SO 2 , and CO.
• a CAI NOxygen analyzer monitors the upstream oxygen and nitrogen oxides concentration
• a Teledyne Analytical P100 analyzer monitors the downstream oxygen concentration. All data is continuously recorded to a computer.
• thermocouples continuously measure the temperature throughout the system.
• Several manometers are used to measure the pressure drop and static pressure of the system.
• the CO 2 capture capacity of calcium oxide obtained from calcium hydroxide, PCC and as received ground lime was determined in a thermogravimetric analyzer. In order to improve the strength of the PCC particles, the PCC powder was pelletized into 2mm pellets and then ground to a size of 150 microns. The CO 2 capture capacity of the PCC pellets as well as the pelletized and broken sorbent was also determined. During these test the calcination was conducted under ideal conditions in 100% N 2 at 700° C and the carbonation was conducted in 10% CO 2 at 650° C.
• the CO 2 capture capacity has been defined by the weight % capture which is the grams of CO 2 removed/gram of the CaO sorbent. It can be seen that the weight % capture attained by the sorbent obtained from PCC powder is 74% when compared to that of 60% attained by the calcium hydroxide sorbent and 20% attained by the ground lime sorbent. The CO 2 capture capacity of the pelletized and broken PCC is almost the same (71 %) as the PCC powder as shown in Figure 14. The PCC pellet requires a very large residence time due to mass transfer resistance but reaches the same final CO 2 capture capacity of 71 % as that of the PCC pelletized and broken sorbent.
• the effect of the concentration of steam in the carrier gas was also investigated on the CO 2 capture capacity of the sorbent.
• the concentration of steam in the carrier gas With the increase in the concentration of steam in the carrier gas, the sintering of the sorbent is reduced and the CO 2 capture capacity of the sorbent is increased.
• a solution for decreasing the parasitic energy consumption is to hydrate the sorbent at a temperature higher than the dehydration temperature so that the exothermic hydration energy can be used to supply energy required for the endothermic dehydration reaction.
• the hydration temperature is between the temperature of calcination and carbonation, cooling and reheating of the solids is avoided.
• Figure 20 shows the effect of pressure hydration at 600° C for pressures ranging from 100 psig to 300 psig. It was found that the reactivity of the sorbent increases from 18% to 45% by pressure hydration at 600° C and 100 psig. The reactivity of the sorbent was found to increase with the decrease in pressure although the extent of hydration remained the same at all pressures.
• Figure 21 shows the effect of Calcium :Carbon mol ratio on carbon dioxide removal for multiple sorbents on a once-through basis.
• Commercial-grade calcium hydroxide clearly outperforms the commercial-grade lime in removing carbon dioxide from a coal-combustion flue gas stream. At a calcium :carbon mol ratio of approximately 1.7, virtually all CO 2 can be removed using calcium hydroxide.
• Figure 22 shows the percent of CO 2 removed from a coal-combustion flue gas stream for calcium hydroxide and provides a logarithmic relationship between the CO 2 removed and the calcium :carbon mol ratio with a high-degree of correlation. Approximately 1.5:1 Calcium :Carbon mol ratio would be required for complete CO 2 removal, according to the regression equation.
• Figure 23 shows the removal of sulfur dioxide from the flue gas stream for multiple sorbents and calcium :carbon ratios.
• the SO 2 removal is independent of the calcium :carbon mol ratio due to calcium hydroxide's high degree of reactivity.
• the sulfur content of coal is significantly lower than the carbon content of coal, the calcium :sulfur ratio will always be greater. For example, if a coal has 75% carbon and 5% sulfur, a 1 :1 calcium :carbon mol ratio would be equivalent to a 40:1 calciunrsulfur ratio. This allows even the commercial- grade lime, which had poor CO 2 removals, to remove sulfur dioxide to a high degree at modest calcium :carbon ratios.
• Figure 23 is obtained for single-cycle studies; however, complete SO 2 removal has been obtained for multiple cycles. [00112] Finally, it is important to note the effect of residence time on the CO 2 removal. In the entrained bed reactor set-up, the residence time was varied between 0.3 and 0.6 seconds, while maintaining a constant calcium :carbon mol ratio. The results are shown in Figure 24. Clearly, increasing the residence time increases the CO 2 removed.
• Figure 25 shows the results from the cyclic studies.
• the calcium :carbon mol ratio was kept constant, with a value around 0.65.
• the calcium hydroxide sorbent with hydration during every cycle maintained its reactivity over the course of 4 cycles, with no indication of loss of reactivity. This shows that hydration completely reactivates the sorbent and reverses the effect of sintering.
• the initial sorbent in the first cycle was calcium hydroxide.
• the calcium hydroxide was not regenerated, and the calcium carbonate formed in the carbonation reaction was calcined to form calcium oxide. The calcium oxide was then carbonated, and the cycle repeated.
• carbon dioxide capture decreases dramatically.
• Figure 26 shows the reactivity of the sorbent for multicyclic CO 2 capture with hydration for which the % CO 2 removal is illustrated in Figure25. Calcination in the subpilot plant kiln reduces the CO 2 capture capacity of the sorbent from 55% (12.5 moles/Kg CaO) to 20% (4.54 moles/Kg CaO). The subsequent hydration of the sorbent at the Carmeuse Limestone company facility resulted in the increase in the capture capacity of the sorbent back to 55% (12.5 moles/Kg CaO). Three cycles of carbonation and calcination at OSU and hydration at Carmeuse Limestone Company have been conducted and the CO 2 capture capacity has remained constant at 55% (12.5 moles/Kg CaO).

Priority Applications (5)

Applications Claiming Priority (2)

Related Child Applications (1)

Publications (2)

Family

ID=42198813

Family Applications (1)

Country Status (6)

Cited By (7)

Families Citing this family (30)

Family Cites Families (15)

• 2009
  • 2009-11-19 EP EP09828257.7A patent/EP2385873B1/en active Active
  • 2009-11-19 CA CA2743911A patent/CA2743911C/en active Active
  • 2009-11-19 WO PCT/US2009/065224 patent/WO2010059882A2/en active Application Filing
  • 2009-11-19 ES ES09828257.7T patent/ES2684133T3/es active Active
  • 2009-11-19 CN CN200980154994.XA patent/CN102307646B/zh active Active
• 2011
  • 2011-05-19 US US13/111,794 patent/US8512661B2/en active Active

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events