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
  • B01D53/14—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 by absorption
  • B01D53/1418—Recovery of products
• • 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
  • B01D53/14—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 by absorption
  • B01D53/1456—Removing acid components
  • B01D53/1475—Removing carbon dioxide
• • 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
  • B01D53/14—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 by absorption
  • B01D53/18—Absorbing units; Liquid distributors therefor
• • 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
  • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
  • Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
  • Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
• • 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

Definitions

• the invention relates to recovery of carbon di- 5 oxide from gaseous sources using low amounts of energy. More in particular the invention relates to a method for recovery of carbon dioxide by chemical absorption of carbon dioxide from a flue gas, followed by recovery of the carbon dioxide from the chemical 10 absorbent.
• recovery of carbon dioxide is performed by introduction 20 of the gas in an absorber, where the gas contacts a lean solvent containing a chemical absorbent flowing down the absorber.
• the carbon dioxide is at least partially absorbed by the lean solvent and the depleted gas leaves the absorber for further processing
• the solvent containing the carbon dioxide flows through a heating device to the regenerator where the carbon dioxide is released because of the high temperature, and may be recovered and optionally further purified.
• the stripped solvent is cooled and
• the absorber-regeneration system typically allows continuous operation for recovery of carbon dioxide.
• EP 0 588 175 A2 describes a process for remov- 35 ing carbon dioxide from combustion gases where the carbon dioxide is absorbed from the combustion gas through contact at atmospheric pressure with an aqueous amine solution in an absorber.
• the aqueous amine solution containing bound carbon dioxide is transferred to a regenerator where the solution is heated to release the carbon dioxide and the depleted amine solution is cooled and returned to the absorber.
• WO 9521683 describes a method for removing carbon dioxide from exhaust gas from heat engines where carbon dioxide is removed from the gas by absorption of a absorption liquid, which liquid is transferred to a stripping column where it is heated to 120-150 °C to release the carbon dioxide, and returned to the absorption column via a cooler.
• WO 0030738 describes a modification of the split flow process where the semi rich solvent is taken out of the absorber and mixed with semi lean solvent coming from the regenerator, and said mixture is cooled in a heat exchanger before being introduced in the absorber as the semi lean solvent .
• US 5,145,658 disclose partial reclaiming of the reaction thermal energy by passing the rich solvent from the absorber through a rich-reflux reboiler and next through a rich-lean reboiler under a reduced pressure. In this way a reduction of steam require- ments for regeneration of the absorbing solution of at least 10 % can be realized.
• US 4,318,872 disclose an absorber intercooler, where a heat exchanger is formed internally in an absorber.
• the absorber intercooler is particular suited for the absorption of ethylene by a hydrocarbon liquid.
• One object of the present invention is to re- prise the overall energy consumption for recovery of carbon dioxide.
• reduction of overall energy consumption means that the factual energy supplied is reduced or the amount of utilizable energy recovered is increased.
• utilizable energy in form of electricity, high pressure steam, low pressure steam and hot water for warming purposes.
• Increasing the amount of at least one of these forms of utilizable energy is to be understood as a reduction of overall energy consumption.
• Another object of the present invention is to improve the efficiency of chemical absorption of carbon dioxide in an absorber.
• the absorber providing means for transfer of thermal energy from the solution contain- ing the chemical absorbent to a receiving medium.
• the temperature in the absorber may be kept at a suitable low temperature to provide for a more opti- mal absorption of carbon dioxide from the gas.
• the improved absorption of carbon dioxide means that a smaller absorber volume as well as a smaller amount of the chemical absorbent is necessary in order to provide for the same removal of carbon dioxide from the gas than would have been necessary without the means for removal of thermal energy.
• means for transfer of thermal energy to a receiving medium may provide the chemical reaction heat from the absorption in a useful form.
• the receiving medium is water, and in one preferred embodiment the receiving medium is water for domestic heating.
• gaseous source is flue gas
• gaseous source for carbon dioxide is flue gas from a power plant .
• Figure 1 shows a temperature profile of the temperature in a typical absorber and in an absorber according to the present invention.
• FIG. 2 shows an absorber-regenerator circuit for carbon dioxide recovery according to the prior art.
• accessory equipments such as valves, pumps, means for replenishing the chemical absorbent or water etc. are not shown, however, the person skilled in the art will appreciate that such equipment must be inserted at appropriate positions.
• Figure 3 shows an absorber-regenerator circuit for carbon dioxide recovery according to the present invention where means for transfer of thermal energy is provided in the absorber.
• an external incoming stream such as water for domestic heating serves as receiving medium.
• Figure 4 shows an embodiment of the absorber- regenerator circuit according to the present invention where the rich chemical absorbent serves as receiving medium.
• An absorber for use according to the invention is an absorber, where the gaseous source is intimately contacted with the chemical absorbent in order to ensure a high transfer of carbon dioxide from the gas to the chemical absorbent .
• Such absorbers are constructed as a column where the gaseous source is introduced in the lower part and rises through the column to the top where it is discharged.
• the chemical absorbent is introduced in the upper part of the column and flows down through the column where it contacts the rising gas.
• the absorber may be filled with an inert solid material in order to ensure a better contact between the gas and the chemical absorbent.
• An example of such inert solid material is Rashig rings made of a ceramic material .
• FIG 2 a traditional absorber-regenerator circuit shown where 10 is the absorber having an inlet 11 for the gaseous source and a outlet 12 for gas depleted of carbon dioxide, an inlet 13 for lean chemical absorbent, i.e. containing a low amount of absorbed carbon dioxide, and an outlet 14 for rich chemical absorbent, i.e. containing a high amount of absorbed carbon dioxide .
• a reflux section 16 On the top of the absorber 10 is placed a reflux section 16, where an cooling liquid is circulating via a collector tray 17 and pipe 18 to a cooler 19 where the temperature of the cooling liquid is adjusted to keep the water balance; after the cooler, the cooling liquid is returned to the reflux section 16.
• regenerator 20 is the regenerator, having an inlet 21 for rich chemical absorbent, an outlet 22 for lean chemical absorbent, an outlet 23 for carbon dioxide a heater 25 having a inlet for high temperature steam and an outlet 27 low temperature steam and/or condensate, which heater is connected to the regenerator via conduit 24.
• the regenerator may be filled with a solid inert material in order to facilitate the escape of carbon dioxide from the chemical absorbent .
• the absorber 10 is connected with the regenera- tor 20 via a conduit 30 for rich chemical absorbent and conduit 31 for lean chemical absorbent.
• a heat exchanger 32 is provided in order to transfer heat from the hot lean chemical absorbent leaving the re- generator to the rich chemical absorbent leaving the absorber.
• a cooler 33 is provided in order to cool the lean chemical absorbent before entering the absorber.
• refluxcooler 28 is a refluxcooler connected to the outlet 23 for carbon dioxide, where the recovered carbon dioxide is cooled by a cooling stream connected to the refluxcooler 28 via the tubes 44 and 45.
• the condensate formed in refluxcooler 28 is returned to the regenerator via conduit 29. Below the inlet for conden- sate a section for distribution of the condensate may be provided.
• accessory equipments are not included in this and the following figure, however the person skilled in the art will appreciate the type and positions for such equipment.
• accessory equipment can be mentioned pumps, valves, condensers for condensation of water and/or chemical absorbent from the discharged gases, means for replenishing water and/or chemical absorbent etc.
• the inlet temperature of an absorber using an amine solution as a chemical absorbent according to the art is usually in the range of 40 - 50 °C for the gaseous source entering the column in the lower part and similar in the range of 40-50 °C for the chemical absorbent entering in the upper part of the column.
• the absorption of carbon dioxide from a gaseous source is performed at approximately atmospheric pressure, but the absorption and/or regenera- tion may also be performed under a higher pressure.
• the efficiency of carbon dioxide absorption by the chemical and physical absorbent varies with the temperature, as it will be known in the area.
• the present invention is based on the recognition that chemical absorbents tend to have better abilities to react with carbon dioxide at lower temperature than at a higher temperature . Due to the heat generated by the binding of carbon dioxide to the chemical absorbent, in a absorption column where the chemical ab- sorbent is fed in the upper end and the gas is fed in the bottom the temperature will rise down through the column until it peaks, and below said peak the temperature will decrease due to the gas being fed into the lower part of the column.
• An example of a tem- perature profile of an absorption column is shown in figure 1.
• the temperature may be so high that the absorption proceeds less favourable with the consequence that a larger volume of the column is necessary than if the absorption took place under a lower temperature .
• thermo energy for transfer of thermal energy, having an inlet 41 and an outlet 42 for receiving me- dium, is inserted into the absorber 10 in accordance with the present invention.
• the fact that thermal energy is removed from the absorber means that the temperature through the absorber will be more even as shown in figure 1, approximating an isothermal ab- sorption in the absorber.
• the heat transferred to the receiving medium may be used e.g. for domestic heating.
• the removal of the thermal energy from the ab- sorber has little effect on the stream of rich chemical absorbent leaving the absorber 10 through the outlet 14, because the leaving temperature is to a high extend determined by the temperature of the in- coming gas 11.
• the temperature of the receiving medium 42 can be further raised by leading it through pipe 44 to the refluxcooler; the outlet stream 45 can reach a temperature few degrees below temperature of the product stream 23 leaving the regenerator 20. If for example a 30% w/w solution of monoethanol amine is used as chemical absorbent and the gaseous source is containing 15 % v/v carbon dioxide the temperature of the chemical absorbent will increase approximately 27 °C due to absorption as the absorp- tion heat of carbon dioxide by monoethanol amine is approximately 450 kcal/kg absorbed carbon dioxide. If the receiving medium is kept approximately 10°C below the temperature of the chemical absorbent approximately 63 % of the reaction heat will be transferred to the receiving medium.
• refluxcooler 28 and the cooler 19 also prevent excessive loss of water and/or chemical absorbent from the system. These considerations are often re- ferred to as the water balance.
• the rich chemical absorbent leaving the absorber is used as receiving medium in the means for transfer of thermal energy 40.
• the temperature of the lean chemical absorbent will be higher after the heat exchanger 32.
• the higher temperature of this stream can be exchanged in heat exchanger 34 with a heat transferring medium.
• the heat transferring medium enters 34 via the tube 46, where it absorbs the heat recovered 40.
• This medium is further transferred through 44 to refluxcooler 28; the outlet stream 45 can reach a temperature few de- grees below the temperature of the product stream 23 leaving the regenerator 20.
• the gaseous source according to the invention may in principle be any gaseous source containing carbon dioxide. Suitable amounts for use according to the invention are in the range of 1-40%, preferably 5-25 % and particular preferred in the range of 10- 20%. The remaining of the gas may be any gases that do not bind to the chemical absorbent to a significant extent, such as nitrogen, atmospheric air and similar.
• gaseous sources can be mentioned flue gas, combustion gas, exhaust gas from engines; exhaust gas from fermentation and natural gas.
• Flue gases from power and/or boiler plants are preferred gaseous sources.
• the chemical absorbent may in principle be any chemical that is capable of binding carbon dioxide by an exothermic reaction at one temperature and releasing carbon dioxide by an endothermic reaction at a second temperature, which is higher that said first temperature.
• a chemical absorbent may be selected for a particular application based on the actual conditions, in particular the temperature of the source gas and presence of reactive components such as oxy- gen in the gas.
• the chemical absorbent may be a solution of one or more chemical compound in a solvent or it may be a pure compound.
• the chemical absorbent may be selected among primary, secondary or tertiary amines having a molecular weight less that 1000 Da.
• Examples of chemical absorbents that may be used according to the present invention are aqueous solutions of: potassium carbonate, monoethanol amine, diethanol amine, triethanol amine, methyl diethanol amine, diisopropyl amine, diglycol amine, potassium carbonates and sodium carbonates .
• Monoethanol amine is a preferred chemical absorbent.
• Water is a preferred solvent for the chemical absorbent and a preferred concentration of the chemical absorbent is 5-60%, more preferred 10-40 %, even more preferred approximately 30%.
• aqueous solution of an amine as a chemical absorbent is often referred to as "lye" .
• lean is intended to mean containing low amount of absorbed carbon dioxide.
• a lean chemical absorbent is less that 50 % saturated with carbon dioxide, preferably less than 30 % saturated.
• rich is intended to mean containing a high amount of absorbed carbon dioxide.
• a rich chemical absorbent according to the invention is more than 50% saturated with car- bon dioxide, preferably more that 80% saturated and even more preferred more that 90% saturated.
• saturated with respect to the chemical absorbent is intended to mean the fraction of the chemical absorbent that is com- bined with carbon dioxide.
• a corrosion inhibitor may be useful to add a corrosion inhibitor to the chemical absorbent in or- der to protect the plant.
• a number of corrosion inhibitors are known in the art such as cupper compounds and vanadium compounds .
• additives e.g. antifoaming agents
• means for transfer of thermal energy to a receiving medium is provided in the absorber. This has the effect that the temperature in the absorber is lowered and the absorption proceeds more efficiently. This results in that a smaller volume of the absorber and the regen- erator as well as the chemical absorbent is necessary in order to recover the same amount of carbon dioxide compared with an absorber-regenerator plant without means for transfer of thermal energy to a receiving medium according to the invention. Further because energy is removed from the absorber by the means for transfer of thermal energy less water and/or chemical absorbent will be evaporated from the column, which water and/or chemical absorbent has to be replaced in order to keep a con- stant volume of the chemical absorbent.
• the means for transfer of heat is preferably arranged in the part of the absorber where the temperature is higher.
• the means for transfer of thermal energy are arranged in a section where in between usual inert solid material is placed.
• means for transfer of thermal energy are arranged at different positions along the column.
• the absorber is parted in two or more absorbers having means for transfer of thermal heat from the chemical absorbent inserted between the absorbers.
• the means for transfer of thermal energy is placed outside the absorber where chemical absorbent is taken out from the absorber, cooled in the means for transfer of thermal energy and without any further mixing returned essentially to the same height of the absorber column.
• the means for transfer of thermal energy may be any suitable means for performing this effect, as it is known for the person skilled in the art, such as a heat exchanger.
• the means for transfer of thermal energy is placed in the warmest part of the absorber.
• the circulation of the absorbing liquid controls the warm front. At low circulation the warm front is pushed to the top of the absorber section. At high circulation the front is pushed downwards.
• the warmest part is preferably below the middle of the efficient absorber, where the efficient absorber is to be understood as the distance between the inlets of lean chemical absorbent and the inlet of gaseous source, or if the absorber is filled with a inert solid material the height of this filling .
• Heat exchangers for use according to the pre- sent invention may in principle be of any type. It is within the skills of the person skilled in the art to select a suitable heat exchanger based on the estimated flows of absorbent, gas and receiving medium as well as the estimated amount of thermal energy to be transferred in order to provide for a more optimal temperature in the absorber, and in order to recover heat in order to improve the energy economics of the total plant.
• heat exchangers for use according to the present invention are: finned tube radiators, ribbed tube radiators and plate heat exchangers.
• one heat exchanger of more than one type may be arranged at different position along the absorber column.
• the heat exchangers are preferably made of a material that is resistant to the conditions created by the actual chosen chemical absorbent, the gaseous source and the pressure.
• the chemical absorbent is an amine such as monoethanol amine
• the gaseous source contains oxygen and the temperature is in the range of 55-120°C a harsh corrosive environment is created in the absorber, which has to be tolerated by the heat exchanger.
• the heat exchangers are connected so that the receiving medium flows counter current to the gaseous source, i.e. the receiving medium is introduced in the upper end and discharged from the lower end of the heat exchanger.
• transferring the thermal energy transferred to the receiving medium to a useful form, preferably water reduces the overall energy consumption of the proc- ess.
• the hot water may be used directly e.g. for heating purposes, or it may be further heated using steam. In this way the overall energy consumption is reduced because either less steam is used for producing hot water, or because more hot water is produced.
• the receiving medium is a process stream which is partially or completely heated to a desired temperature by the transfer of thermal energy inside the absorber. In this way the overall energy consumption is reduced because less steam is used for heating said process streams.
• the receiving medium may be any medium having an suitable temperature, which is available in an ap- suitable amount to receive the estimated amount of energy.
• a process stream or an external incoming stream may be used.
• the receiving medium may be the rich absorbent stream, which is preheated before being transferred to the regenerator.
• the receiving medium is water for domestic heating or process water, which water usually returns to the power plant at a temperature in the range of 30-60°C.
• the heat exchange according to the invention may serve as a partial or complete heating of the water for domestic heating before it is discharged from the power plant e.g. with a temperature of e.g. 70-
• the receiving medium may also be a medium circulating in a closed circuit for delivering the energy in another place where it can be utilized.
• a different receiving medium may be used for each means for transfer of thermal energy.
• the receiving medium is preferably water, and even more preferred water for domestic heating.
• the receiving medium is water for domestic heating, which enters into the heat exchanger placed in the absorber according to the invention, and subsequently the water is further heated by heat exchanging with the hot chemical absorbent and/or carbon dioxide leaving the regenera- tor.
• the receiving medium is water for domestic heating, which enters into the heat exchanger placed in the absorber according to the invention, and subsequently the water is further heated by heat exchanging with the hot chemical absorbent and/or carbon dioxide leaving the regenera- tor.
• Feed gas temperature (11) 43.5°C
• Depleted gas temperature (below section 16) 65°C Peak temperature in absorber (10) 78°C Feed reflux temperature (after heat exchanger 19 38°C Max reflux temperature (18) 60°C Reflux circulation (18) 20 kg/kg C ⁇ 2 MEA (monoethanol amine) concentration 30 % w/w
• Reboiler steam feed temperature (stream 26) 139°C Reboiler condensate temperature (stream 27) 126°C
• a plant essential as figure 2 was used for this comparative example.
• the domestic heating water was used as cooling medium in the absorber reflux cooler (19) and next introduced in pipe (44) in order to recover the heat generated in the reflux condensator (28) .
• the following recovery of heat was calculated:
• a plant essentially as in figure 3 was used for these calculations.
• the domestic heating water was used as receiving medium in the heat exchanger 40 in the absorber 10.
• the domestic heating water was let in via tube 41 and from the outlet 42 of the absorber 40 in the absorber led to the reflux condensator 28 via tube 44 for further recovery of heat.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Analytical Chemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Health & Medical Sciences (AREA)
• Biomedical Technology (AREA)
• Environmental & Geological Engineering (AREA)
• Gas Separation By Absorption (AREA)

Applications Claiming Priority (3)

Publications (1)

Family

ID=8160745

Family Applications (1)

Country Status (2)

Cited By (1)

Families Citing this family (3)

Citations (3)

Family Cites Families (7)

• 2002
  • 2002-10-01 WO PCT/DK2002/000650 patent/WO2003028854A1/en not_active Application Discontinuation
  • 2002-10-01 EP EP02800046A patent/EP1432495A1/de not_active Withdrawn

Patent Citations (3)

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events