EP1432495A1

EP1432495A1 - Method and device for recovery of thermal from an exothermic carbon dioxide absorption process

Info

Publication number: EP1432495A1
Application number: EP02800046A
Authority: EP
Inventors: Svend Andreas Geleff
Original assignee: Union Engineering AS
Current assignee: Union Engineering AS
Priority date: 2001-10-02
Filing date: 2002-10-01
Publication date: 2004-06-30
Also published as: WO2003028854A1

Abstract

An improved process for recovery of thermal energy from an exothermic absorption process is disclosed; such as a process for recovery of carbon dioxide from a gaseous source e.g. flue gas. In a traditional absorber for carbon dioxide the absorption may be impaired by high temperature in the absorber caused by the reaction energy released by absorption of carbon dioxide to a chemical absorbent such as monoethanol amine. According to the invention the efficiency of the absorption improved by securing that the temperature is lowered in the absorber by insertion of means for transfer of thermal energy in the absorber. This has further the benefit that the released reaction energy may be utilized for example for heating of water for domestic heating. The net benefit of these contributions makes it possible to recover carbon dioxide from flue gas by spending a significant lower amount of energy.

Description

METHOD AND DEVICE FOR RECOVERY OF THERMAL ENERGY FROM AN EXOTHERMIC CARBON

DIOXIDE ABSORPTION PROCESS

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.

BACKGROUND FOR THE INVENTION

15 Various methods for recovery of carbon dioxide from process gases are well known.

In a typical absorber-regenerator system, 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

25 or discharge. 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

30 returned to the absorber for further absorption of carbon dioxide. 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.

As the reaction of carbon dioxide and the absorbent is exothermic, a temperature rise in the absorber is encountered, which may be disadvantageous because a high temperature makes the absorption reaction less efficient.

In US patent 5,085,839 monitoring the temperature profile down through the absorber and adjusting the flow of incoming gas and aqueous amino absorbent address the problem of the temperature rise in the absorption column.

Another way to address the problem of high temperature in the absorber is the split flow process originally described in US 1,971,798. In this process a cool lean solvent is introduced in the top of the absorber and flows down through the rising gas absorbing carbon dioxide and is removed from the absorber as a warm semi rich solvent before it reaches the bottom of the absorber. At approximately the same point a cold semi lean solvent is introduced in the absorber where it flows down through the absorber to the bottom of the column where it leaves as a rich solvent. The introduction of the absorbing solvent in two streams may provide for a more optimal tempera- ture in the absorber, which gives a better absorption of carbon dioxide with the consequence that a smaller total volume of the absorber may be necessary. Even though the split flow process is an efficient process for recovery of carbon dioxide it inherently has some disadvantages. The fact that the semi rich solvent is removed from the absorber before it is fully saturated with carbon dioxide and the semi lean solvent is taken from the regenerator before it is fully depleted for carbon dioxide means that the full capacity of the chemical absorbent is not utilized. Consequently, larger amounts of chemi- cal absorbent are needed than would have been necessary if the full capacity for carbon dioxide was utilized, which also means that the volume of the absorber and of the regenerator must be larger.

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.

Despite all the progress that have been disclosed there is still a need for measures to further optimise the process and reduce the energy required for recovering carbon dioxide from a gaseous source . SHORT DESCRIPTION OF THE INVENTION

One object of the present invention is to re- duce the overall energy consumption for recovery of carbon dioxide.

The term reduce overall energy consumption has to be understand broad. According to the present invention reduction of overall energy consumption means that the factual energy supplied is reduced or the amount of utilizable energy recovered is increased. Thus for example in a power plant combustion of fuel leads to 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 objects according to the invention is achieved by in the absorber providing means for transfer of thermal energy from the solution contain- ing the chemical absorbent to a receiving medium.

By providing means for removal of thermal energy from the solution containing the chemical absorbent 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.

Further the means for transfer of thermal energy to a receiving medium may provide the chemical reaction heat from the absorption in a useful form.

In one embodiment the receiving medium is water, and in one preferred embodiment the receiving medium is water for domestic heating.

In another embodiment the gaseous source is flue gas, and in one preferred embodiment the gaseous source for carbon dioxide is flue gas from a power plant .

SHORT DESCRIPTION OF THE DRAWINGS

Figure 1 shows a temperature profile of the temperature in a typical absorber and in an absorber according to the present invention.

Figure 2 shows an absorber-regenerator circuit for carbon dioxide recovery according to the prior art. For sake of simplicity in this and the following figures 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. In this embodiment 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.

DETAILLED DESCRIPTION OF THE INVENTION

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 . In figure 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 . 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.

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.

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.

For simplicity 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. As examples of 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. During operation 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. When the concentration of carbon dioxide and the chemical absorbent are high a significant temperature rise in the column can be observed due to the reaction energy released during absorbing carbon dioxide to the chemical absorbent. Dependent on the actual system this increase in the column may be in the range of 20-50°C, i.e. the temperature may reach up to approximately 100 °C.

Usually 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. Thus in the section of the column with the highest temperature 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 .

In the absorber-regenerator circuit shown in figure 3 means 40 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.

It will be appreciated that energy introduced into the absorber, such as the reaction energy from the absorption, leads to evaporation of chemical absorbent or water if the chemical absorbent is an aqueous solution, which vapours will be discharged from the circuit via the outlet 12 for depleted gas. Consequently, the removal of heat from the absorber further has the benefit that less chemical absorbent and/or water has to be replenished in order to oper- ate continuous.

The person skilled in the art will appreciate that 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.

In figure 4 the rich chemical absorbent leaving the absorber is used as receiving medium in the means for transfer of thermal energy 40. In this embodiment 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.

As examples of 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%.

Within the area an aqueous solution of an amine as a chemical absorbent is often referred to as "lye" .

In the present description the term "lean" is intended to mean containing low amount of absorbed carbon dioxide. Thus a lean chemical absorbent is less that 50 % saturated with carbon dioxide, preferably less than 30 % saturated. The term "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.

In this connection the term "saturated" with respect to the chemical absorbent is intended to mean the fraction of the chemical absorbent that is com- bined with carbon dioxide.

Due to the basic properties of many of the chemical absorbents and optional the presence of oxygen in the gaseous source is 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 .

Other additives, e.g. antifoaming agents, may also be added to the chemical absorbent in order to obtain a certain property of the liquid, as it will be known in the art .

According to the present invention 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.

In one embodiment the means for transfer of thermal energy are arranged in a section where in between usual inert solid material is placed.

In another embodiment means for transfer of thermal energy are arranged at different positions along the column. In still another embodiment of the invention the absorber is parted in two or more absorbers having means for transfer of thermal heat from the chemical absorbent inserted between the absorbers.

In another embodiment 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.

Preferably 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. In this connection in 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.

Examples of heat exchangers for use according to the present invention are: finned tube radiators, ribbed tube radiators and plate heat exchangers.

More that 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. For example, if 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.

Preferably 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.

In one preferred embodiment of the invention 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. In another preferred embodiment 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. As receiving medium a process stream or an external incoming stream may be used. In one embodiment the receiving medium may be the rich absorbent stream, which is preheated before being transferred to the regenerator. In another embodiment 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. In the latter case 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-

105°C. 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.

If more that one means for transfer of thermal energy are provided 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.

In a preferred embodiment 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. In this way a major part of the energy spent for the carbon dioxide recovery can be recovered as heating of the water for domestic heating, which overall improves the useful effect of a power plant .

At present in power plants low pressure steam at a pressure of 2-3 bar and a temperature of approximately 200°C is often used for heating of water for domestic heating. If this steam instead is used in a carbon dioxide recovery process according to the invention and the water for domestic heating is used as receiving medium it is possible by operating the carbon dioxide recovery plant and to a large extend maintain the overall useful thermic efficiency of the power plant.

Even though the invention in the above has been explained for use in a "single-flow" system the person skilled in the art will appreciate that it may also by applied for a split flow. The invention will now be explained in further details by the following examples, which are intended to serve as illustration and should not be regarded as limiting for the present invention.

EXAMPLES

In the following examples plants comprising a absorber and a regenerator equipped with a reflux condensator essentially as depicted in figure 2 and 3 is used for the calculations. For both the comparative and the examples the following temperatures and streams as used in the calculations:

Absorber:

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 Cθ₂ MEA (monoethanol amine) concentration 30 % w/w

MEA circulation (in stream 31) 17 kg lye/kg C0₂

Regenerator:

Top temperature (stream 23) 103°C

Reflux temperature (stream 29) 49°C Bottom steam flow (stream 26) 1.85 kg/kg Cθ₂ Bottom steam enthalpy (stream 26) 2190 kJ/kg

Reboiler steam feed temperature (stream 26) 139°C Reboiler condensate temperature (stream 27) 126°C

Bottom product temperature (stream 22) 121.2°C

Top feed temperature (stream 21) 112.8°C

Top stream flow (stream 23) 0.60 kg/kg Cθ₂

Steam condensation 103°C -80°C (stream 23) 2100 kJ/kg steam

Condensate fraction 103°C-80°C (stream 29) 60%

Domestic heating water inlet temperature 45°C

Temperature pinch over all other heat exchangers: 5°C

Temperature pinch on regenerator tower: Bottom product temperature (stream 22)- Top feed temperature (stream 21) (121.1 - 112.8)= 8.3 °C

Comparative example

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) . Using these connections the following recovery of heat was calculated:

Recovery from absorber reflux (19) 20* ( (60-5) - (45) )*4.18 836 kJ/kg C0₂

Recovery from reflux condensator (28) : 0.60 * 60% *2100 = 756 kJ/kg C0₂

Total recovery 1592 kJ/kg C0₂ Temperature increase for domestic water:

1592/(20*4.18) = 19°C

Final temperature for domestic water: 45°C + 19°C = 64°C

Heat effiency 1592/(1.85*2192) = 39%

Example

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.

Recovery from heat exchanger in absorber (40) :

17* ( (78-5) - (45) )*4.18 = 1634 kJ/kg C0₂ Recovery from reflux condensator (28) :

0.60 * 60%*2100 = 756 kJ/kg C0₂

Total recovery = 2390 kJ/kg C0₂

Temperature increase for domestic water

2390/(17*4.18) = 33.6 °C

Final temperature for domestic water

45 °C + 33.6 °C = 78.6 °C Heat efficiency 2390/(1.85*2192)= 59?

Claims

P A T E N T C L A I M S

1. Process for recovery of carbon dioxide from a gaseous source comprising absorbing carbon dioxide using a chemical absorbent and recovering the carbon dioxide by release from the chemical absorbent by heating wherein the absorption of carbon dioxide is an exothermic reaction and release of carbon dioxide from the absorbent is an endothermic reaction c h a r a c t e r i s e d in that, the chemical absorbent is cooled during the absorption by use of means for transfer of thermal energy to a receiving medium.

2. Process according to claim 1, wherein the overall energy consumption is reduced by transferring the thermal energy received by the receiving medium into an useful form.

3. Process according to claim 1 or 2 , wherein the chemical absorbent is an aqueous solution of one or more compounds selected from: monoethanol amine, diethanol amine, triethanol amine, methanol diethanol amine, dimethanol ethanol amine, diiospropanol amine, potassium carbonates and sodium carbonates.

4. Process according to claim 1 to 3 , wherein the gaseous source is a flue gas.

5. Process according to any of claim 1 to 4 , wherein the means for transfer of thermal energy is arranged in the absorbing part of the absorber.

6. Process according to any of the preceding claims, wherein the means for transfer of thermal energy is one or more heat exchangers.

7. Process according to claim 6, wherein the receiving medium flows counter current flows counter current or concurrent or in any direction between the heat exchangers .

8. Process according to any of the preceding claims, wherein the receiving medium is water.

9. Process according to claim 8, wherein the receiving medium is a process stream.

10. Process according to claim 8, wherein the receiving medium is water for domestic heating.

11. Process according to claim 9 or 10, wherein the water is further heated by heat exchange with the hot regenerated chemical absorbent and/or released carbon dioxide .

12. Process according to any of the preceding claims, wherein the means for thermal transfer is arranged in separate sections surrounded by sections filled with mass and energy transferring sections, such as Rashig rings.

13. Plant for recovery of carbon dioxide from a gaseous source comprising an absorber (10) , wherein carbon dioxide is absorbed using a chemical absorbent, and a regenerator (20) , wherein the carbon di- oxide is released from the chemical absorbent by heating, and wherein the absorption of carbon dioxide is an exothermic reaction and the release of carbon dioxide from the absorbent is an endothermic reaction c h a r a c t e r i s e d in that, the absorber is provided with means (40) for transfer of thermal energy to a receiving medium.

14. Plant according to claim 13, wherein the means for transfer of thermal energy is placed inside the absorber.

15. Plant according to claim 13 or 14, wherein the means for transfer of thermal energy is one or more heat exchangers .

16. Plant according to claim 15, where the one or more heat exchangers are selected among finned tube radiators, ribbed tube radiators and plate heat exchangers .