WO2015052727A2

WO2015052727A2 - A multi-compression system and process for capturing carbon dioxide

Info

Publication number: WO2015052727A2
Application number: PCT/IN2014/000631
Authority: WO
Inventors: Vinay AMTE; Asit Kumar Das; Surajit Sengupta; Manoj Yadav; Sukumar Mandal; Alok Pal; Ajay Gupta; Ramesh Bhujade; Satyanarayana Reddy Akuri; Rajeshwer Dongara
Original assignee: Reliance Industries Limited
Priority date: 2013-10-09
Filing date: 2014-09-29
Publication date: 2015-04-16
Also published as: WO2015052727A3; IN2013MU03192A

Abstract

The present disclosure provides a multiple compression system and a process for capturing carbon dioxide (C02) from a flue gas stream containing C02, by using a carbon dioxide capture media. The disclosure also provides a process for regeneration of the capture media.

Description

A MULTI-COMPRESSION SYSTEM AND PROCESS FOR CAPTURING CARBON DIOXIDE

FIELD

The present disclosure relates to a system and process for capturing carbon dioxide from flue gas using carbon dioxide absorbent capture media.

BACKGROUND

Flue gases originating from oil refineries, fossil fuel based power plants, cement plants contain hazardous gaseous pollutants such as sulfur oxides (SO_x), nitrogen oxides (NO_x), hydrogen sulfide (H₂S), hydrogen chloride (HC1), hydrogen fluoride (HF) and carbon dioxide (C0₂) that have some severe adverse short-term as well as long-term effects on human health as well as the environment. Different strategies have therefore been devised for reducing the amount of the afore-stated pollutants from flue gases before they are released into the atmosphere.

The amount of C0₂ present in flue gas can be reduced by strategies such as burning less coal, improving the efficiency of coal-fired power plants and capturing, followed by storing the captured C0₂. Among the C0₂ capture techniques such as pre- combustion, post combustion and oxy-combustion, post combustion carbon capture techniques are the most effective since they do not require any extensive rebuilding of the existing process plant.

Absorption technique such as wet scrubbing amine absorption is another conventional technique for carbon dioxide capture. US 20120312020 discloses an apparatus and a method for regeneration of the capture media such as an absorption solution and recovery of the absorbed gas from the capture media. US 20120312020 further discloses an apparatus and method for the removal and recovery of a target gas from a gas stream and its application in post combustion carbon capture in a thermal power l plant. However, the process of US 20120312020 employs heating means such as reboilers that increase the operating cost.

The conventional absorption techniques for C0₂ capture are associated with several drawbacks such as high energy requirement for capturing carbon dioxide and amine regeneration (2.5 - 4.0 GJ/ton) and oxidative degradation that reduces the overall efficiency of the power plant by up to 13%. Most of the processes for capturing carbon dioxide from air or flue gas stream utilize heat from an external source together with the heat made available by compressing the desorbed vapor product (pure carbon dioxide). However, this type of heat utilization does not significantly increase the cost-efficiency of the process.

Therefore, there is felt for developing a simple, energy efficient and economic process as well as a system for the removal of carbon dioxide present in flue gases that overcomes the drawbacks associated with the prior art.

OBJECTS

Some of the objects of the present disclosure, which at least one embodiment is able to achieve, are discussed herein below.

It is an object of the present disclosure to provide a multi-compression process for capturing carbon dioxide using a C0₂ capture media.

It is another object of the present disclosure to provide a cost-efficient and environment friendly process for capturing carbon dioxide using a C0₂ capture media.

It is still another object of the present disclosure to provide a multi-compression system for capturing carbon dioxide using a C0₂ capture media.

It is yet another object of the present disclosure to provide a-cost efficient and environment friendly system for the regeneration of the carbon dioxide using a C0₂ capture media.

It is still another object of the present disclosure to ameliorate one or more problems of the prior art or to at least provide a useful alternative. Other objects and advantages of the present disclosure will be apparent from the following description and accompanying drawing which is not intended to limit the scope of the present disclosure.

SUMMARY

The present disclosure provides a multi-compression process for capturing carbon dioxide (CO₂) from a flue gas stream containing CO₂; said process comprising the following steps: i. directing the flow of the flue gas stream through a blower (B) to obtain a pressurized flue gas stream with elevated temperature; ii. extracting the heat from the pressurized flue gas stream in a first heat exchanger (Hex-B) using circulating thermic fluid to obtain a heated thermic fluid and a cooled pressurized flue gas stream; iii. directing the cooled pressurized flue gas stream to a CO₂ absorber (A); iv. passing in the absorber (A) a fluidized lean CO₂ capture media to generate a rich capture media stream; v. heating said rich capture media stream in a second heat exchanger (Hex-E) to near regeneration temperature, at least partially, using lean, hot capture media stream to obtain a heated rich capture media stream; vi. feeding said heated rich capture media stream to a desorber (D); vii. maintaining the temperature inside the desorber (D) to a regeneration temperature by recycling lean, hot capture media stream, heated outside the desorber (D) with the help of circulating heated, pressurized and vaporized non-thermic fluid to desorb CO₂ from the heated rich capture media stream and separately emit (a) a CO₂ rich vapor mixture and (b) lean capture media stream; viii. subjecting the C0₂ rich vapor mixture to condensation in a condenser (Cd) with the help of an external supply of cold water to obtain a two-phase mixture; ix. separating the two-phase mixture in a first separator (SI) to obtain a condensate and pure C0₂ gas, said condensate being recycled to the desorber (D); x. heating the separated lean capture media stream externally, emitted from the desorber (D), in a third heat exchanger (Hex-C) with the help of circulating heated, pressurized and vaporized non-thermic fluid to obtain lean, hot capture media stream; xi. circulating heated, pressurized and vaporized non-thermic fluid through the third heat exchanger (Hex-C) using heat sourced from an external heat source (IN) and heat extracted from said pressurized flue gas stream using circulating thermic fluid; xii. leading the lean, hot capture media stream exiting the third heat exchanger (Hex-C) to the second heat exchanger (Hex-E) and the fourth heat exchanger (Hex-D), serially arranged with the second heat exchanger

^' (Hex-E), to cool the lean, hot capture media stream to a temperature at which it is adapted to absorb C0₂ in the absorber (A); and xiii. obtaining pure C0₂ gas from the first separator (SI).

The rich capture media stream emerging from the absorber (A) can be directed to the second heat exchanger (Hex-E) via a first pump (PI). The adsorption reaction in the adsorber (A), takes place efficiently at a temperature ranging from 50-70 °C.

The heated rich capture media emerging from the second heat exchanger (Hex-E) can be directed to a third separator (S3) to separate the generated C0₂ gas and the rich capture media, said separated C0₂ gas being converged along with the C0₂ rich vapor mixture emerging from the desorber (D) in a second converger (Cv2) to provide a converged stream and said rich capture media being directed to the desorber (D). The converged stream can be passed through the condenser (Cd) to obtain a two-phase mixture, followed by separating the two-phase mixture in the first separator (SI) to obtain condensate and pure C0₂ gas, said condensate being recycled to the desorber (D) and said pure C0₂ gas being isolated for further processing.

The condensate emerging from the first separator (S I) can be passed through a second pump (P2) before entering the desorber (D).

The rich capture media upon heating in the desorber (D) drives off a pre-determined quantity of water, said pre-determined quantity of water exits the desorber (D), gets heated in the third heat exchanger (Hex-C) to provide steam, said steam re-enters the desorber (D) to aid the desorption of C0₂ from the rich capture media. The heated rich capture media in the desorber (D) may be heated to a temperature ranging from ISO- ISO °C for efficiently desorbing C0₂ from the heated rich capture media.

The lean, hot capture media stream emerging from the third heat exchanger (Hex-C), can pass through a third pump (P3), before entering the second heat exchanger (Hex- E).

The non-thermic fluid can be circulated by heating the non-thermic fluid emerging from the third heat exchanger (Hex-C) with the help of external heat source (IN) in the fifth heat exchanger (Hex-A) and further heating the non-thermic fluid in a sixth heat exchanger (Hex-F) where-after, the heated non-thermic fluid is fully pressurized and vaporized and at an elevated pressure and temperature, is supplied to the third heat exchanger (Hex-C) for heating the lean capture media stream emerging from the desorber (D).

The non-thermic fluid emerging from the third heat exchanger (Hex-C) can be passed through a valve (V) before entering the fifth heat exchanger (Hex-A).

The vapor and liquid exiting the fifth heat exchanger (Hex-A) are separated using a second separator (S2) and only the liquid portion is supplied to the sixth heat exchanger (Hex-F). The vapor collected from the second separator (S2) and vapor emanating from the sixth heat exchanger (Hex-F) can be converged in a first converger (Cvl) before being compressed in a booster compressor (BC) for supply to the third heat exchanger (Hex- C).

The thermic fluid can be circulated using a thermic fluid cycle in which the thermic fluid is heated using compressed flue gas in the first heat exchanger (Hex-B), the heated thermic fluid is supplied to the sixth heat exchanger (Hex-F) where it loses heat to the circulating heated, vaporized non-thermic fluid, resulting in the emanation of warm thermic fluid from the sixth heat exchanger (Hex-F) which is further cooled by external cold water in a seventh heat exchanger (Hex-G) for reiteration through the first heat exchanger (Hex-B).

The lean, warm capture media stream emerging from the second heat exchanger (Hex- E) can be cooled in the fourth heat exchanger (Hex-D) with the help of external supply of cold water for supplying the cool lean capture media stream to the absorber (A).

The capture media can be an aqueous solution of at least one inorganic metal carbonate or at least one amine, wherein said amine is selected from the group consisting of primary amine, secondary amine, tertiary amine, and mixtures thereof.

The non-thermic fluid can be at least one selected from the group consisting of water, methanol, acetone, and propanol.

The present disclosure further provides a multi-compression system for capturing carbon dioxide (C0₂) from a flue gas stream having C0₂; said system comprising: i. a blower (B) adapted to receive the flue gas stream and pressurize said flue gas stream to generate a pressurized flue gas stream with elevated temperature; ii. a first heat exchanger (Hex-B) adapted to receive said pressurized flue gas stream and thermic fluid and transfer heat from said pressurized flue gas stream to said thermic fluid to obtain heated thermic fluid and a cooled pressurized flue gas stream; iii. an absorber (A) adapted to receive said cooled pressurized flue gas stream and a cool and lean capture media stream, said cool and lean capture media stream adapted to absorb C0₂ to generate a rich capture media stream; iv. a second heat exchanger (Hex-E) adapted to receive said rich capture media stream and heat said rich capture media stream to near a predefined regeneration temperature, to obtain a heated rich capture media stream; v. a desorber (D) adapted to receive said heated rich capture media stream and maintain heat therein to desorb C0₂ from said heated rich capture media stream to emit C0₂ rich vapor and a lean capture media stream; vi. a condenser (Cd) adapted to condense the C0₂ rich vapor emerging from the desorber (D) and provide a two phase mixture of C0₂ gas and condensate; vii. a first separator (SI) adapted to receive the two phase mixture emerging from the condenser (Cd) and separate the pure C0₂ gas and condensate and direct said condensate to the desorber (D); viii. a third heat exchanger (Hex-C) adapted to receive and heat the lean capture media stream exiting the desorber (D) and direct the lean, hot capture media to the second heat exchanger (Hex-E) to heat the rich capture media stream emerging from the absorber (A); ix. a fourth heat exchanger (Hex-D) adapted to receive warm lean capture media stream from said second heat exchanger (Hex-E) and further adapted to transfer heat from said warm lean capture media stream to an external supply of cold water to emit cool lean capture media stream to be supplied to said absorber (A) for absorbing C0₂ from the flue gas stream; x. a non-thermic fluid cycle adapted to provide heat in the third heat exchanger (Hex-C) to heat the lean capture media stream emerging from the desorber (D); and xi. a thermic fluid cycle adapted to supply heat to the non-thermic fluid cycle; said thermic fluid cycle being driven by heat supplied by the pressurized flue gas stream received by the blower (B).

The system can further comprise a first pump (PI) provided in-line between the absorber (A) and the second heat exchanger (Hex-E), adapted to pressurize the rich capture media stream emerging from the absorber (A).

The system can further comprise a third separator (S3) provided in-line between the second heat exchanger (Hex-E) and the desorber (D) and a second converger (Cv2) and the desorber (D), adapted to receive the heated rich capture media stream emerging from the second heat exchanger (Hex-E) and separate the generated C0₂ gas and the rich capture media.

The second converger (Cv2) is provided in-line between the condenser (Cd) and the desorber (D) and the condenser (Cd) and the third separator (S3) and is adapted to converge the separated C0₂ gas emerging from the third separator (S3) and the C0₂ rich vapor mixture emerging from the desorber (D) and direct the converged stream to the condenser (Cd).

The system can further comprise a second pump (P2) provided in-line between the first separator (SI) and the desorber (D), adapted to pressurize the condensate emerging from the first separator (SI).

The system can further comprise a third pump (P3) provided in-line between the third heat exchanger (Hex-C) and the second heat exchanger (Hex-E), adapted to pressurize the lean, hot capture media stream emerging from the third heat exchanger (Hex-C).

The third heat exchanger (Hex-C) is further adapted to receive a predetermined quantity of water emerging from the desorber (D), heat the predetermined quantity of water to provide steam and recycle said steam to the desorber (D). A second separator (S2) is provided in-line between the fifth heat exchanger (Hex-A) and the sixth heat exchanger (Hex-F) and is adapted to separate vapor and liquid exiting the fifth heat exchanger (Hex-A) and supply the liquid portion to the sixth heat exchanger (Hex-F).

The non-thermic fluid cycle comprises a fifth heat exchanger (Hex-A) adapted to heat the non-thermic fluid emanating from the third heat exchanger (Hex-C) using external process heat (IN), a second separator (S2) adapted to separate liquid and vapor emanating from the fifth heat exchanger (Hex-A), a sixth heat exchanger (Hex-F) adapted to heat and vaporize the liquid received from the second separator (S2), a first converger (Cvl) for converging the vapors received from the second separator (SI) and from the sixth heat exchanger (Hex-F) and a booster compressor (BC) adapted to receive vapor from the first converger (Cvl) and adapted to vaporize, pressurize and heat the vapor for onward supply to the third heat exchanger (Hex-C) to heat the lean capture media stream emerging from the desorber (D).

The system can further comprise a valve (V) provided in-line between the third heat exchanger (Hex-C) and the fifth heat exchanger (Hex-A) to de-pressurize the stream of non-thermic fluid emerging from the third heat exchanger (Hex-C).

The thermic fluid cycle comprises the blower (B) adapted to receive, heat and pressurize the flue gas stream containing C0₂, the first heat exchanger (Hex-B) adapted to receive the heated and pressurized flue gas stream and cooled thermic fluid and further adapted to transfer heat from said flue gas stream to said cooled thermic fluid to emit cool, pressurized flue gas stream and hot thermic fluid, the sixth heat exchanger (Hex-F) adapted to receive the hot thermic fluid and transfer heat from the hot thermic fluid to the liquid component of the non-thermic fluid and emit warm thermic fluid and a seventh heat exchanger (Hex-G) adapted to receive the warm thermic fluid and further adapted to exchange heat in the warm thermic fluid with an external supply of cold water to emit cool thermic fluid for further reiteration in the cycle. The capture media can be an aqueous solution of at least one inorganic metal carbonate or at least one amine, wherein said amine is selected from the group consisting of primary amine, secondary amine, tertiary amine, and mixtures thereof.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The disclosure will now be described with reference to accompanying non-limiting drawing:

Fig. 1 illustrates a schematic diagram of a multi-compression system (100) for capturing carbon dioxide contained in flue gas using a carbon dioxide absorbent capture media.

Fig. 2 illustrates a schematic diagram of a multi-compression system (100) including a first pump (PI), a second pump (P2), a third pump (P3), a valve (V), a second converger (Cv') and a third separator (S3) in accordance with one embodiment of the present disclosure.

DETAILED DESCRIPTION

The present disclosure relates generally to the capture of carbon dioxide from a variety of flue gas sources including, without limitation, those from oil refineries, fossil fuel based power plants, cement plants and any other potential source of emissions. The invention of the present disclosure involves a multiple-compression cycle for compressing excess flue gas produced from the afore-stated sources that involves use of a high temperature heat transfer fluid (thermic fluid) for extracting the heat generated due to the compression and a heat pump for selective compression and expansion of a circulating non-thermic fluid that utilizes the process plant waste heat, together, for compensating the heat demand in the step of regeneration of the capture media. In accordance with the present disclosure, there is provided a system (100) and a process for capturing carbon dioxide (C0₂) from a flue gas stream containing C0₂. The disclosure also provides a process for the regeneration of the carbon dioxide capture media. The system and process will now be explained with reference to Figure 1; the key components of the system being referenced generally by numerals as indicated in the accompanying drawing.

In accordance with the present disclosure the system (100) comprises the following components:

• a blower (B);

• a first heat exchanger (Hex-B);

• an absorber (A);

• a second heat exchanger (Hex-E);

• a first separator (SI);

• a desorber (D);

• a condenser (Cd);

• a second separator (S2);

• a third heat exchanger (Hex-C);

• a fourth heat exchanger (Hex-D);

• a non-thermic fluid cycle; and

• a thermic fluid cycle.

The process of the present disclosure initially includes directing the flow of a hot flue gas stream, containing C0₂, sourced from an external plant or apparatus, through a blower (B). The blower is employed to increase the pressure and the temperature of the flue gas stream.

The pressurized flue gas stream from the blower (B) is passed through the first heat exchanger (Hex-B), which also receives a stream of cool thermic fluid. The cool thermic fluid stream extracts heat from the pressurized flue gas stream and a heated thermic fluid stream and a cooled pressurized flue gas stream are found to emerge from the first heat exchanger (Hex-B). Typically, the thermic fluid includes but is not limited to oils, hydrocarbon oils such as Dowtherm and glycols.

The cooled pressurized flue gas stream is then directed to a C0₂ absorber (A), which also receives a cool and lean capture media stream. The cooled pressurized flue gas stream and the cool and lean capture media stream run counter current to each other. The lean capture media stream reacts chemically with the C0₂ gas in the incoming cooled pressurized flue gas stream to generate a stream of capture media rich in C0₂ as well as a treated flue gas stream devoid of C0₂. The adsorption reaction in the adsorber (A), takes place efficiently at a temperature ranging from 50-70 °C.

Typically, the capture media includes but is not limited to an aqueous solution of at least one inorganic metal carbonate or at least one amine, wherein said amine is selected from the group consisting of primary amine, secondary amine, tertiary amine, and mixtures thereof. The treated flue gas stream devoid of C0₂ is vented to the atmosphere, whereas the stream of capture media rich in C0₂ is directed to the second heat exchanger (Hex-E). In another embodiment, demonstrated in Figure 2, the capture media rich in C0₂ emerging from the absorber (A) is directed to the second heat exchanger (Hex-E) via a first pump (PI). The pump is employed to increase the pressure of the capture media rich in C0₂.

The stream of capture media rich in C0₂ is heated in the second heat exchanger (Hex- E) to its regeneration temperature by a lean, hot capture media stream sourced from the third heat exchanger (Hex-C). The second heat exchanger (Hex-E) reduces the thermal load on the desorber (D) which is used downstream. A stream of a heated rich capture media results, which is further directed to the desorber (D) for complete regeneration. In the other embodiment demonstrated in Figure 2, the stream of heated rich capture media that emerges from the second heat exchanger (Hex-E) is passed through a third separator (S3), before being directed to the desorber (D). This is done in order to separate the C0₂ gas generated from the rich capture media due to the increase in temperature. The separated rich capture media is directed further to the desorber (D). The desorber (D), at the regeneration temperature, desorbs the C0₂ gas from the heated rich capture media stream to separately yield a vapor mixture of steam and C0₂ gas and a lean capture media stream. The heated rich capture media in the desorber (D) may be heated to a temperature ranging from 130-150 °C for efficiently desorbing C0₂ from the heated rich capture media. The vapor mixture is passed through the condenser (Cd), where an external supply of cold water (C W) is provided for effecting partial condensation. The resulting two phase stream of C0₂ gas and condensate is separated in the first separator (SI) and the condensate (water) is refluxed back to the desorber (D). In another embodiment demonstrated by Figure 2, the vapor mixture emerging from the desorber (D) along with the separated C0₂ gas provided by the third separator (S3) are converged into a second converger (Cv2) to provide a converged stream. The converged stream is then forwarded to the condenser (Cd) to obtain a two-phase mixture. In accordance with the embodiment demonstrated in Figure 2, the condensate emerging from the first separator (SI) is passed through a second pump (P2) before entering the desorber (D).

The lean capture media stream emerging from the desorber (D) is heated in the third heat exchanger (Hex-C) by utilization of latent heat of condensation of circulating compressed non-thermic fluid. Typically, the non-thermic fluid is selected from the group that includes but is not limited to water, methanol, acetone, and propanol. Further, the non-thermic fluid has boiling point in range of 25 to 105 °C and workable under pressure range of 1 - 10 bar and also with higher latent heat of vaporization/condensation. Initially, a cool non-thermic fluid is heated by means of external heat source (IN) in the fifth heat exchanger (Hex-A) so that the non-thermic fluid partially vaporizes. The vapor and the liquid components of the non-thermic fluid stream are separated in a second separator (S2) after which, the liquid component is passed through a sixth heat exchanger (Hex-F). The previously mentioned stream of heated thermic fluid emerging from the first heat exchanger (Hex-B) is made to pass through the sixth heat exchanger (Hex-F), which vaporizes the liquid component of the non-thermic fluid stream. Thus, the vaporized non-thermic fluid emerging from the sixth heat exchanger (Hex-F) as well as the vaporized non-thermic fluid emerging from the second separator (S2) is passed through a first converger (Cvl). The converged vaporized non-thermic fluid emerging from the first converger (Cvl) is passed through a booster compressor (BC) which further vaporizes, pressurizes and heats the vaporized non-thermic fluid to provide further vaporized, pressurized and heated non-thermic fluid which heats up the lean capture media stream emerging from the desorber (D). The booster compressor (BC) receives the resultant vaporized non- thermic fluid and compresses the same to a pressure such that the condensation temperature of the non-thermic fluid is higher than the regeneration temperature. The booster compressor provides the resultant compressed non-thermic fluid to the third heat exchanger (Hex-C) from where it further moves to the fifth heat exchanger (Hex- A). In an embodiment demonstrated by Figure 2, the heated non-thermic fluid emerging from the third heat exchanger (Hex-C) is made to pass through a valve (V) before entering the fifth heat exchanger (Hex-A). This, in totality, is the non-thermic fluid cycle which aids in maintaining the regeneration temperature in the desorber (D). The thermic fluid emerging from the sixth heat exchanger (Hex-F) is cooled in a seventh heat exchanger (Hex-G) before entering the first heat exchanger (Hex-B). In accordance with the embodiment demonstrated by Figure 2, the capture media in the desorber (D) upon gaining regeneration temperature drives off a pre-determined quantity of water. This pre-determined quantity of water is characteristic of the amount of water present in the capture media. This pre-determined quantity of water is passed through and heated in the third heat exchanger (Hex-C), to provide steam. Thus, the generated steam is recycled back to the desorber (D) to aid the desorption process.

A portion of the lean, hot capture media emerging from the desorber (D) is directed to the second heat exchanger (Hex-E), where it heats the incoming rich capture media stream. The resultant lean, warm capture media stream is then directed to the fourth heat exchanger (Hex-D) where it is cooled by an external source of water (C/W) to provide a cool lean capture media stream that is recycled to the absorber (A) for reiteration of the process. A make-up capture media solution is introduced into the absorber (A) along with the cool lean capture media stream in order to compensate for any further loss due to degradation. In an embodiment demonstrated by Figure 2, the lean, hot capture media emerging from the desorber (D) is made to pass through a third pump before being directed to the second heat exchanger (Hex-E).

The invention of the present disclosure employs a heat pump concept for upgrading the heat quality of the non-thermic fluid. The heat pump concept involves cyclic evaporation, compression, condensation and expansion of the non-thermic fluid. The sources of low temperature process waste heat in oil refineries include, without limitation, refinery column overhead products where the streams are cooled using fin- fan coolers; while in power plants, the sources of low temperature process waste heat include thermal process streams or from other industrial process. Although, any temperature level of process plant waste heat can be utilized for its usage in capture media regeneration, use of heat pumps for transferring heat energy from a heat source to a heat sink against a temperature gradient is preferred by using a relatively small amount of high quality drive energy such as electricity, fuel and high-temperature waste heat.

The invention of the present disclosure employs a multi-compression cycle. The compression cycle in each stream loop, like flue gas stream and the non-thermic fluid stream, provides necessary heat and its re-utilization for regeneration of capture media. The flue gas with/without excess quantity, with the aid of the circulating thermic fluid, is compressed in a first compression cycle to generate the required quantity of heat that can be used within the capture process. The compression of the non-thermic fluid in the second compression cycle generates sufficient energy which finds its usage in regeneration of capture media and also within the process to compensate the heat demand.

The present invention distinctly characterizes the method to compensate the shortfall in heat demand within the process by use, in combination, of recovery of low temperature process waste heat by the non-thermic fluid using the heat pump principle and recovery of flue gas heat by the thermic fluids. The low temperature process waste heat streams which are available in process plants cannot be used for steam generation. Sources of low temperature process waste heat in oil refinery may include without limitation particularly refinery column overhead products where the streams are cooled using fin-fan coolers, while in power plant may include thermal process streams or from other industrial process. Thus, a huge amount of heat which is wasted today can be reused for regeneration of the capture media in the process of carbon dioxide capture.

The invention of the present disclosure, therefore, offers several advantages over the conventional amine based absorption process, for all key performance parameters. The total heat required for regeneration of the capture media in the conventional amine based absorption process is higher than that required in the process of the present disclosure. The flue gas cooler in the present invention recovers maximum heat associated with the flue gas stream to utilize within the process. On the other hand, most of the heat is lost during cooling of the flue gas prior to absorption in the conventional amine process. In any capture process, the steam requirement significantly influences the operating cost associated with the regeneration of the capture media, but the present invention judiciously tackles the problem of heat demand for the regeneration step by utilizing the heat available with flue gas stream, which is an insignificant value as compared to the generation of steam. Similarly, the quantity of the cooling water required in the present disclosure is appreciably lower than that required in the conventional amine based process.

The present disclosure will now be discussed in the light of the following non-limiting embodiments:

Example 1: The process of capture of C0₂ according to the present disclosure and its comparison with the conventional absorption process

A] The process of capture of CO₂ according to the present disclosure:

A stream of 62.5 (tonnes per hour) TPH of flue gas [carbon dioxide: 15, oxygen: 5 and nitrogen: rest, composition on the dry basis (vol %)] at 160 °C temperature and 1.013 bar pressure was introduced into a blower (B-1.2 MW) to obtain a 62.5 TPH flue gas stream at 225 °C temperature and 1.5 bar pressure. The pressurized flue gas stream was forwarded into a first heat exchanger (Hex-B) where the heat from the pressurized stream was extracted by circulating 38.4 TPH of Dowtherm as the thermic fluid at 35 °C, sourced from the seventh heat exchanger (Hex-G). 39.5 TPH of heated thermic fluid stream at 240 °C was sent to the sixth heat exchanger (Hex-F), whereas 62.5 TPH of the cooled pressurized flue gas stream at 45 °C and 1.3 bar pressure was directed to the absorber (A) having a temperature of 45 °C. 320.6 TPH of an aqueous solution of amine, as the capture media, at 40 °C was also introduced into the absorber (A). The aqueous solution of amine absorbed the C0₂ gas contained in the flue gas stream in the absorber (A) and the resultant 50.15 TPH treated flue gas stream at 45 °C was vented to the atmosphere whereas the 333.7 TPH of the rich capture media at 59.2 °C and 1.25 bar pressure was directed to the second heat exchanger (Hex-E).

The stream of the rich capture media at 59.2 °C and 1.25 bars was passed through a first pump (PI) and the resulting 1.8 bar rich capture media stream was directed to the second heat exchanger (Hex-E) for heating near its regeneration temperature by means of a 318.85 TPH of a lean, hot capture media stream at 115 °C, 2.5 bar pressure sourced from the third heat exchanger (Hex-C). 333.7 TPH of heated rich capture media at 105 °C resulted, which was further directed to a third separator (S3) where the generated C0₂ gas was separated from the rich capture media and then resultant 329.6 TPH of rich capture media at 105 °C was fed to the top of desorber (D) for complete regeneration.

Desorption of the C0₂ gas from the 105 °C rich capture media took place in the desorber (D), at the regeneration temperature of 115 °C, to yield a 23.13 TPH of C0₂ - rich vapor mixture at 101 °C and 346 TPH of lean capture media at 113.7 °C.

The vapor mixture from the third separator (S3) and the desorber (D) was fed to a second converger (Cv2) and the combined vapor stream from the second converger (Cv2) was passed through a condenser (Cd), where an external supply of cold water at 30 °C partially condensed the vapor stream. The two phase mixture of pure C0₂ gas and condensate were separated in the first separator (SI) and the condensate was refluxed back to the desorber (D). The lean capture media emerging from the desorber (D) was heated in the third heat exchanger (Hex-C) by means of 26 TPH of water vapor, as the non-thermic fluid, at 143 °C at 1.75 bar pressure. Initially, 26 TPH of waste cool water at 114 °C and 1.55 bar pressure was heated by means of external heat source (IN) in the fifth heat exchanger (Hex- A) so that the water vaporized partially to give a 26 TPH stream at 113 °C and 1.5 bar pressure. The vapor (steam) and the liquid (water) components of the partially vaporized water stream were separated in a second separator (S2) after which, 2.54 TPH of the water at 113.1 °C and 1.5 bar pressure was passed through a sixth heat exchanger (Hex-F). The heated thermic fluid emerging from the first heat exchanger (Hex-B) was made to pass through the sixth heat exchanger (Hex-F), which vaporized the water. The steam emerging from the sixth heat exchanger (Hex-F) as well as the 23.45 TPH of steam from the second separator (S2) at 113.1 °C and 1.5 bar pressure was passed through a first converger (Cvl). 26 TPH of the converged steam emerging from the first converger (Cvl) at 112.6 °C and at 1.4 bar pressure was passed through a booster compressor (BC-0.41 MW) which further vaporized, pressurized and heated stream to provide 26 TPH of steam at 142.75 °C at 1.75 bar pressure. The steam was used for heating 346 TPH of the lean capture media emerging from the desorber (D) at 113.67 °C. The heated Dowtherm emerging from the sixth heat exchanger (Hex-F) was cooled in a seventh heat exchanger (Hex-G) before entering the first heat exchanger (Hex-B).

318.85 TPH of lean, hot capture media at 115 °C was further directed to the second heat exchanger (Hex-E), where it heated the incoming rich capture media at 59.22 °C. The resultant 318.85 TPH of lean, warm capture media at 62.95 °C was then directed to the fourth heat exchanger (Hex-D) where it was cooled by an external source of cold water at 30 °C to provide a 318.85 TPH of cool lean capture media at 40 °C that is recycled to the absorber (A) for reiteration of the process. A 1.75 TPH of make-up amine solution at 40 °C was introduced into the absorber (A) along with the cool lean capture media at 45 °C in order to compensate for any further loss due to degradation.

B] Comparison of the process of the present disclosure with the conventional absorption process: CO₂ capture achieved by the conventional amine based absorption process and the process of the present disclosure has been provided in Table 1 that illustrates the efficacy of the process of the present disclosure vis-a-vis the conventional amine based absorption process, on the basis per tonnes of carbon dioxide.

Table 1. Comparison of the process of the present disclosure with the conventional absorption process

The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.

The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

TECHNICAL ADVANTAGES AND ECONOMIC SIGND7ICANCE

The process and system of the present disclosure harness the heat associated with the flue gas along with the process waste heat and utilizes it to replenish the heat requirement within the process.

The invention of the present disclosure also provides a heat integrated process that significantly reduces the operating cost by using a multiple-compression cycle for regeneration of the capture media used for carbon dioxide capture from flue gas stream.

The process and system of the present disclosure can be easily retrofitted to existing facilities.

Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

The use of the expression "at least" or "at least one" suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the invention to achieve one or more of the desired objects or results.

The numerical values given for various physical parameters, dimensions and quantities are only approximate values and it is envisaged that the values higher than the numerical value assigned to the physical parameters, dimensions and quantities fall within the scope of the invention and the claims unless there is a statement in the specification to the contrary.

While certain embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Variations or modifications in the process or compound or formulation or combination of this invention, within the scope of the invention, may occur to those skilled in the art upon reviewing the disclosure herein. Such variations or modifications are well within the spirit of this invention. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the invention.

Claims

CLAIMS:

1. A multi-compression process for capturing carbon dioxide (C0₂) from a flue gas stream containing C0₂; said process comprising the following steps: i. directing the flow of the flue gas stream through a blower (B) to obtain a pressurized flue gas stream with elevated temperature; ii. extracting the heat from the pressurized flue gas stream in a first heat exchanger (Hex-B) using circulating thermic fluid to obtain a heated thermic fluid and a cooled pressurized flue gas stream; iii. directing the cooled pressurized flue gas stream to a C0₂ absorber (A); iv. passing in the absorber (A) a fluidized lean C0₂ capture media to generate a rich capture media stream; v. heating said rich capture media stream in a second heat exchanger (Hex-E) to near regeneration temperature, at least partially, using lean, hot capture media stream to obtain a heated rich capture media stream; vi. feeding said heated rich capture media stream to a desorber (D); vii. maintaining the temperature inside the desorber (D) to a regeneration temperature by recycling lean, hot capture media stream, heated outside the desorber (D) with the help of circulating heated, pressurized and vaporized non-thermic fluid to desorb C0₂ from the heated rich capture media stream and separately emit (a) a C0₂ rich vapor mixture and (b) lean capture media stream; viii. subjecting the C0₂ rich vapor mixture to condensation in a condenser (Cd) with the help of an external supply of cold water to obtain a two-phase mixture; ix. separating the two-phase mixture in a- first separator (SI) to obtain a condensate and pure C0₂ gas, said condensate being recycled to the desorber (D); x. heating the separated lean capture media stream externally, emitted from the desorber (D), in a third heat exchanger (Hex-C) with the help of circulating heated, pressurized and vaporized non-thermic fluid to obtain lean, hot capture media stream; xi. circulating heated, pressurized and vaporized non-thermic fluid through the third heat exchanger (Hex-C) using heat sourced from an external heat source (IN) and heat extracted from said pressurized flue gas stream using circulating thermic fluid; xii. leading the lean, hot capture media stream exiting the third heat exchanger (Hex-C) to the second heat exchanger (Hex-E) and the fourth heat exchanger (Hex-D), serially arranged with the second heat exchanger (Hex-E), to cool the lean, hot capture media stream to a temperature at which it is adapted to absorb C0₂ in the absorber (A); and xiii. obtaining pure C0₂ gas from the first separator (SI).

2. The process as claimed in claim 1, wherein said rich capture media stream emerging from the absorber (A) is directed to the second heat exchanger (Hex- E) via a first pump (PI).

3. The process as claimed in claim 1, wherein said heated rich capture media emerging from the second heat exchanger (Hex-E) is directed to a third separator (S3) to separate the generated C0₂ gas and the rich capture media, said separated C0₂ gas being converged along with the C0₂ rich vapor mixture emerging from the desorber (D) in a second converger (Cv2) to provide a converged stream and said rich capture media being directed to the desorber (D); wherein the converged stream is passed through the condenser (Cd) to obtain a two-phase mixture, followed by separating the two-phase mixture in the first separator (SI) to obtain condensate and pure C0₂ gas, said condensate being recycled to the desorber (D) and said pure C0₂ gas being isolated for further processing.

4. The process as claimed in claim 1, wherein the condensate emerging from the first separator (SI) is passed through a second pump (P2) before entering the desorber (D).

5. The process as claimed in claim 1, wherein the rich capture media upon heating in the desorber (D) drives off a pre-determined quantity of water, said predetermined quantity of water exits the desorber (D), gets heated in the third heat exchanger (Hex-C) to provide steam and said steam re-enters the desorber (D) to aid the desorption of C0₂ from the rich capture media.

6. The process as claimed in claim 1, wherein the lean, hot capture media stream emerging from the third heat exchanger (Hex-C), passes through a third pump (P3), before entering the second heat exchanger (Hex-E).

7. The process as claimed in claim 1, wherein non-thermic fluid is circulated by heating the non-thermic fluid emerging from the third heat exchanger (Hex-C) with the help of external heat source (IN) in the fifth heat exchanger (Hex-A) and further heating the non-thermic fluid in a sixth heat exchanger (Hex-F) where-after, the heated non-thermic fluid is fully pressurized and vaporized and at an elevated pressure and temperature, is supplied to the third heat exchanger (Hex-C) for heating the lean capture media stream emerging from the desorber (D); wherein the non-thermic fluid emerging from the third heat exchanger (Hex-C) is passed through a valve (V) before entering the fifth heat exchanger (Hex-A); wherein the vapor and liquid exiting the fifth heat exchanger (Hex-A) are separated using a second separator (S2) and only the liquid portion is supplied to the sixth heat exchanger (Hex-F); wherein the vapor collected from the second separator (S2) and vapor emanating from the sixth heat exchanger (Hex-F) are converged in a first converger (Cvl) before being compressed in a booster compressor (BC) for supply to the third heat exchanger (Hex-C).

8. The process as claimed in claim 1, wherein the thermic fluid is circulated using a thermic fluid cycle in which the thermic fluid is heated using compressed flue gas in the first heat exchanger (Hex-B), the heated thermic fluid is supplied to the sixth heat exchanger (Hex-F) where it loses heat to the circulating heated, vaporized non-thermic fluid, resulting in the emanation of warm thermic fluid from the sixth heat exchanger (Hex-F) which is further cooled by external cold water in a seventh heat exchanger (Hex-G) for reiteration through the first heat exchanger (Hex-B).

9. The process as claimed in claim 1, wherein lean, warm capture media stream emerging from the second heat exchanger (Hex-E) is cooled in the fourth heat exchanger (Hex-D) with the help of external supply of cold water for supplying the cool lean capture media stream to the absorber (A).

10. The process as claimed in claim 1, wherein the capture media is an aqueous solution of at least one inorganic metal carbonate or at least one amine, wherein said amine is selected from the group consisting of primary amine, secondary amine, tertiary amine, and mixtures thereof; and wherein the non-thermic fluid is at least one selected from the group consisting of water, methanol, acetone, and propanol.

11. A multi-compression system for capturing carbon dioxide (C0₂) from a flue gas stream having C0₂; said system comprising: i. a blower (B) adapted to receive the flue gas stream and pressurize said flue gas stream to generate a pressurized flue gas stream with elevated temperature; ii. a first heat exchanger (Hex-B) adapted to receive said pressurized flue gas stream and thermic fluid and transfer heat from said pressurized flue gas stream to said thermic fluid to obtain heated thermic fluid and a cooled pressurized flue gas stream; iii. an absorber (A) adapted to receive said cooled pressurized flue gas stream and a cool and lean capture media stream, said cool and lean capture media stream adapted to absorb C0₂ to generate a rich capture media stream; iv. a second heat exchanger (Hex-E) adapted to receive said rich capture media stream and heat said rich capture media stream to near a predefined regeneration temperature, to obtain a heated rich capture media stream; v. a desorber (D) adapted to receive said heated rich capture media stream and maintain heat therein to desorb C0₂ from said heated rich capture media stream to emit C0₂ rich vapor and a lean capture media stream; vi. a condenser (Cd) adapted to condense the C0₂ rich vapor emerging from the desorber (D) and provide a two phase mixture of C0₂ gas and condensate; vii. a first separator (SI) adapted to receive the two phase mixture emerging from the condenser (Cd) and separate the pure C0₂ gas and condensate and direct said condensate to the desorber (D); viii. a third heat exchanger (Hex-C) adapted to receive and heat the lean capture media stream exiting the desorber (D) and direct the lean, hot capture media to the second heat exchanger (Hex-E) to heat the rich capture media stream emerging from the absorber (A); ix. a fourth heat exchanger (Hex-D) adapted to receive warm lean capture media stream from said second heat exchanger (Hex-E) and further adapted to transfer heat from said warm lean capture media stream to an external supply of cold water to emit cool lean capture media stream to be supplied to said absorber (A) for absorbing C0₂ from the flue gas stream; x. a non-thermic fluid cycle adapted to provide heat in the third heat exchanger (Hex-C) to heat the lean capture media stream emerging from the desorber (D); and xi.^' a thermic fluid cycle adapted to supply heat to the non-thermic fluid cycle; said thermic fluid cycle being driven by heat supplied by the pressurized flue gas stream received by the blower (B).

12. The system as claimed in claim 11, further comprises a first pump (PI) provided in-line between the absorber (A) and the second heat exchanger (Hex- E), adapted to pressurize the rich capture media stream emerging from the absorber (A).

13. The system as claimed in claim 11, further comprises a third separator (S3) provided in-line between the second heat exchanger (Hex-E) and the desorber (D) and a second converger (Cv2) and the desorber (D), adapted to receive the heated rich capture media stream emerging from the second heat exchanger (Hex-E) and separate the generated C0₂ gas and the rich capture media; wherein the second converger (Cv2) is provided in-line between the condenser (Cd) and the desorber (D) and the condenser (Cd) and the third separator (S3) and is adapted to converge the separated C0₂ gas emerging from the third separator (S3) and the C0₂ rich vapor mixture emerging from the desorber (D) and direct the converged stream to the condenser (Cd).

14. The system as claimed in claim 11, further comprises a second pump (P2) provided in-line between the first separator (SI) and the desorber (D), adapted to pressurize the condensate emerging from the first separator (SI).

15. The system as claimed in claim 11, further comprises a third pump (P3) provided in-line between the third heat exchanger (Hex-C) and the second heat exchanger (Hex-E), adapted to pressurize the lean, hot capture media stream emerging from the third heat exchanger (Hex-C).

16. The system as claimed in claim 11, wherein said third heat exchanger (Hex-C) is further adapted to receive a predetermined quantity of water emerging from the desorber (D), heat the predetermined quantity of water to provide steam and recycle said steam to the desorber (D).

17. The system as claimed in claim 11, wherein a second separator (S2) is provided in-line between the fifth heat exchanger (Hex-A) and the sixth heat exchanger (Hex-F) and is adapted to separate vapor and liquid exiting the fifth heat exchanger (Hex-A) and supply the liquid portion to the sixth heat exchanger (Hex-F).

18. The system as claimed in claim 11, wherein said non-thermic fluid cycle comprises a fifth heat exchanger (Hex-A) adapted to heat the non-thermic fluid emanating from the third heat exchanger (Hex-C) using external process heat (IN), a second separator (S2) adapted to separate liquid and vapor emanating from the fifth heat exchanger (Hex-A), a sixth heat exchanger (Hex-F) adapted to heat and vaporize the liquid received from the second separator (S2), a first converger (Cvl) for converging the vapors received from the second separator (SI) and from the sixth heat exchanger (Hex-F) and a booster compressor (BC) adapted to receive vapor from the first converger (Cvl) and adapted to vaporize, pressurize and heat the vapor for onward supply to the third heat exchanger (Hex-C) to heat the lean capture media stream emerging from the desorber (D); and wherein the system further comprises a valve (V) provided in-line between the third heat exchanger (Hex-C) and the fifth heat exchanger (Hex-A) to de-pressurize the stream of non-thermic fluid emerging from the third heat exchanger (Hex-C).

19. The system as claimed in claim 11, in which the thermic fluid cycle comprises the blower (B) adapted to receive, heat and pressurize the flue gas stream containing C0₂, the first heat exchanger (Hex-B) adapted to receive the heated and pressurized flue gas stream and cooled thermic fluid and further adapted to transfer heat from said flue gas stream to said cooled thermic fluid to emit cool, pressurized flue gas stream and hot thermic fluid, the sixth heat exchanger (Hex-F) adapted to receive the hot thermic fluid and transfer heat from the hot thermic fluid to the liquid component of the non-thermic fluid and emit warm thermic fluid and a seventh heat exchanger (Hex-G) adapted to receive the warm thermic fluid and further adapted to exchange heat in the warm thermic fluid with an external supply of cold water to emit cool thermic fluid for further reiteration in the cycle.

20. The system as claimed in claim 11, wherein the capture media is an aqueous solution of at least one inorganic metal carbonate or at least one amine, wherein said amine is selected from the group consisting of primary amine, secondary amine, tertiary amine, and mixtures thereof; and wherein the non-thermic fluid is at least one selected from the group consisting of water, methanol, acetone, and propanol.