Key information

Title
Gas cooler assembly and proccess for cooling flue gas
Application number
20170837
Case type
National
Status
07.12.2018 P.g.a. manglende svar. Søker har ikke begjært gjenopptakelse
Filed
22.05.2017
Effective date
22.05.2017
Publicly available
23.11.2018
Applicant
AITOS GASIFICATION TECHNOLOGY AS (NO)
Inventor
Helge Rosvold (NO)
Agent
CURO AS (NO)

Abstract and drawing

Disclaimer: This text has been machine-scanned and may contain errors – please refer to "Publications" for legally binding content.
Flue gas cooler assembly (100) and process for cooling flue gas from a combustion furnace, particularly a combustion furnace for combustion of solid material. The flue gas cooler assembly comprises a radiation chamber (200) with waterfilled walls (203), an evaporator section (300) comprising evaporators (301) and/or super heaters (302, 303), a second cooler section (400) with a flow duct having a gas flow direction (F) and provided with one or more water boilers (401), and an economizer unit (500). Each water boiler (401) exhibits a closed casing (402) with a water inlet (403), one or more water inlets (403) and water outlets (404), a flue gas inlet (405), a flue gas outlet (406), a number of gas flow tubes (407). The flow tubes (407) are arranged with their respective longitudinal axis substantially along the gas flow direction (F), and arranged to cool gas flowing inside the gas flow tubes (407) by surrounding water (W).

Publications

Latest published versionA1

Documents

 Expand Download files (24)
Date
 Date Doc. No. Process Case number In/Out Journal description To/from
 24.04.2019 16-01 Saksbehandling 20170837 UT Endelig Henleggelse CURO AS
 02.04.2019 15-01 Saksbehandling 20170837 UT PT Varsel om betaling av første årsavgift (3317) (PT20170837)
19.12.2018 14-01 Saksbehandling 20170837 UT Henlagt manglede svar CURO AS
 08.10.2018 13-02 Saksbehandling 20170837 INN Hovedbrev CURO AS
 08.10.2018 13-01 Saksbehandling 20170837 INN Korrespondanse (Hovedbrev inn) CURO AS
 07.08.2018 12-02 Saksbehandling 20170837 INN Hovedbrev CURO AS
 07.08.2018 12-01 Saksbehandling 20170837 INN Korrespondanse (Hovedbrev inn) CURO AS
 07.05.2018 11-01 Saksbehandling 20170837 UT Realitet patent CURO AS
 13.04.2018 10-01 Saksbehandling 20170837 UT Generelt Brev Patent CURO AS
 06.04.2018 09-01 Saksbehandling 20170837 INN Korrespondanse (Hovedbrev inn) CURO AS
 06.02.2018 08-02 Saksbehandling 20170837 INN Hovedbrev CURO AS
 06.02.2018 08-01 Saksbehandling 20170837 INN Korrespondanse (Hovedbrev inn) CURO AS
 30.11.2017 07-02 Saksbehandling 20170837 UT PT report 09:08:41
30.11.2017 07-01 Saksbehandling 20170837 UT Realitet patent Curo AS
 26.10.2017 06-01 Saksbehandling 20170837 UT Generelt Brev Patent Curo AS
 25.10.2017 05-01 Saksbehandling 20170837 INN Korrespondanse (Hovedbrev inn) Curo AS
 17.08.2017 04-03 Saksbehandling 20170837 INN Fullmakt Curo AS
 17.08.2017 04-02 Saksbehandling 20170837 INN Overdragelsesdokument Curo AS
 17.08.2017 04-01 Saksbehandling 20170837 INN Korrespondanse (Hovedbrev inn) Curo AS
 23.05.2017 03-01 Saksbehandling 20170837 UT Formalia 1 Curo AS
 23.05.2017 02-01 Saksbehandling 20170837 UT Infobrev til oppfinner Curo AS
 22.05.2017 01-03 Saksbehandling 20170837 INN Beskrivelse Curo AS
 22.05.2017 01-02 Saksbehandling 20170837 INN Tegninger Curo AS
 22.05.2017 01-01 Saksbehandling 20170837 INN Søknadsskjema Patent Curo AS

Description, claims and drawings

Disclaimer: This text has been machine-scanned and may contain errors – please refer to "Publications" for legally binding content. Description
The present invention is related to an improved flue gas cooler assembly according to the preamble of claim 1 and a process for cooling flue gas according to claim 2.BackgroundThe present invention is related to a flue gas cooler assembly for cooling and purification of flue gas from a combustion process, such as a combustion furnace for combustion of solid material, such as different types of Refused Derived Fuel (RDF), for production of energy and to reduce pollution to a minimum. The flue gas leave the combustion process at an elevated temperature, is passed through numerous evaporators, super heaters, and filters before being emitted to the atmosphere.However, the flue gas emitted to the atmosphere still contain toxic compounds, particularly dioxins formed during favourable conditions in water tube boilers within the flue gas cooler. A water tube boiler is a boiler unit containing water tube boilers where water is circulated inside the water tubes and flue gas is passing outside the water tubes. However, over time, solid deposit is formed on the outer surface of the water tubes. Deposit in the form of copper chloride and iron chloride is particularly critical by providing a surface for catalytic (re)formation of dioxin precursors and dioxins. The catalytic formation occurs rapidly in the temperature range of about 250 °C to about 350°C. ObjectThe object of the present invention is to provide an improved flue gas cooler assembly and process that supresses or prevents formation of dioxins during the gas cooling process.InventionThis object is achieved by a flue gas cooler assembly, and by a process for operating the flue gas cooler assembly according to the characterizing part of claims 1 and 2, respectively. Additional advantageous features appear from the dependent claims.The invention concerns a gas cooler assembly for cooling flue gas from a combustion furnace, particularly a combustion furnace for combustion of solid material, including Refused Derived Fuel (RDF) for production of energy. The flue gas cooler assembly comprises:• an initial radiation chamber with an inlet and an outlet, said radiation chamber being provided with water-filled walls,• an evaporator section comprising a number of evaporators and/or a number of super heaters, • a second cooler section with a flow duct having a gas flow direction and provided with one or more water boilers, and• an economizer unit exhibiting means for additional cooling of flue gas,The respective water boiler exhibits a closed casing with one or more water inlets and water outlets, a flue gas inlet, a flue gas outlet, a number of gas flow tubes with one end in flow connection with said flue gas inlet and an opposite end of the gas flow tubes in flow connection with the flue gas outlet, wherein said gas flow tubes are arranged with their respective longitudinal axis substantially along the gas flow direction.The present invention also concerns a process for cooling flue gas from a combustion furnace as described above, wherein the process comprises the following steps:• flowing the flue gas at a temperature above about 900°C through a radiation chamber provided with water-cooled walls to decrease the flue gas temperature to less than about 800°C,• flowing flue gas through an evaporator section provided with a number of super heaters and/or evaporators to bring the flue gas temperature down to about 350-400°C,• flowing flue gas through a second cooler section exhibiting one or more water boilers, • flowing cooled flue gas through an economizer, and• ejecting cooled flue gas to the atmosphere.According to the invention, the flue gas is led through the cooler section provided with said at least one or more water boilers as described above, at a flow rate providing a residence time for flue gas flowing through said at least one water boiler of less than about 1 second, preferably less than about 0.8 seconds, and cool the flue gas to a temperature of less than about 250-260°C.Accordingly, the flue gas rate is controlled to decrease the flue gas temperature at the flue gas outlet to less than about 250°C. This will suppress formation of dioxins and their precursors during the gas travel downstream of the water boiler.The flow rate of flue gas through the respective water boiler can be kept at about 20 m/s, particularly about 22 m/s. This is a substantial improvement compared to water boilers in prior art flue gas cooler assemblies, which operate with a flow rate of about 6 m/s. As a result, an existing plant can be reengineered to process substantially more flue gas, or new flue gas cooler assemblies can be designed with a smaller size. DrawingsThe present invention is now described in further detail with reference to drawings, where Fig.1 is a strongly schematic illustration of a flue gas cooler according to the invention, Fig.2 is a drawing illustrating a water boiler with water tube bundles,Fig.3A is a drawing illustrating a water boiler with flue gas tubes in a vertical cross-section, and Fig.3B is a horizontal cross-section through the water boiler in fig.3A.Now with reference to Fig.1, a flue gas cooler assembly is indicated in general by reference numeral 100. Flue gas, e.g. from a solid fuel combustion process, at a temperature of more than about 900°C enters the flue gas cooler assembly 100 at the inlet 201 of a radiation chamber 200 provided with water filled walls 203 to perform an initial cooling of the flue gas to bring the temperature down to less than about 850°C. In the radiation chamber 200, heat is transferred by radiation from the flue gas to the chamber walls 203 and further by convection through the chamber walls 203 and finally to the water in the walls. The water is usually circulated by natural convection.Then, the flue gas leaving the radiation chamber 200 at outlet 204, continues to an evaporator section 300 provided with numerous evaporators 301 and/or super heaters 302, 303. Flue gas leaving the evaporator section has a temperature of more than about 430°C before entering a second cooler section 400 provided with one or more water boilers 401 where the flue gas temperature is decreased to less than about 250°C. Finally, the flue gas is led through an economizer unit 501 before entering the surrounding atmosphere at outlet 502.The cooling step in the second cooler section 400 is critical with respect to (re)formation of dioxins. Prior art flue gas coolers employ water tube boilers at a flow rate of about 6 m/s and has a substantial pressure drop across the water boiler 401. The long flue gas residence time in prior art water boilers, combined with tube fouling serving as a catalyst surface for the formation of dioxins in the above mentioned temperature range, is highly favourable for the formation of dioxins. According to the invention, the prior art water boiler 401 with water-filled tubes has been replaced by a water boiler 401 with flue gas pipes or tubes, where flue gas is led through flue gas pipes or tubes in a casing filled with circulating water. The flue gas pipes or tubes are arranged with their longitudinal axis extending in the main flue gas flow in the second cooler section 400. The water boiler is designed to provide a flue gas residence time within the water boiler 401 of less than about 1 second, particularly less than about 0.8 seconds. As an example, flue gas can now flow through the water boiler 401 at a rate above about 20 m/s, particularly about 22 m/s, compared to about 6 m/s with prior art water boilers 401. As a result, the flue gas is cooled in the critical temperature range for the formation of dioxins during a very short period of time, thus preventing formation of dioxins. Another advantage of the water boiler 401 in the flue gas cooler assembly 100 according to the present invention, is that the internal surface of the flue gas tubes are to a low degree subject to fouling than prior art arrangements where flue gas hit the outer tube surface perpendicularly or at an angle.A water boiler being used in prior art flue gas cooler assemblies is shown in Fig.2, where a bundle of water-conducting pipes 408 are arranged within a casing, arranged to cool flue gas passing the water boiler and flowing on the outside of the water-conducting pipes 408.Now referring to Figs.3A and 3B, a water boiler 401 is illustrated. The water boiler 401 comprises a closed casing 402 with one or more water inlets 403, one or more water outlets 404, a flue gas inlet 405, and a flue gas outlet 406. An array or bundle of gas flow ducts/tubes 407 are arranged within the casing 402, with one end of respective gas flow tubes 407 in flow connection with the flue gas inlet 405 and an opposite end of the gas flow tubes 407 in flow connection with the flue gas outlet 406. As can be seen from Fig.3A, a longitudinal extension of the respective gas flow tubes 407 are arranged with their respective longitudinal axis along the gas flow direction F. The gas flow tubes 407 are surrounded by water W circulating by forced or natural convection. In Fig.3B we can see the array of gas flow tubes 407 within the casing 402. This arrangement provides a flow path for flue gas with a substantially smaller pressure drop between gas inlet 405 and gas outlet 406. Another advantage is that the (inner) tube surface is to a far lesser degree subject to fouling, which otherwise will provide a surface for catalytic formation of dioxins and their precursors.Technical effectAccordingly, the process according to the present invention and the flue gas cooler assembly with the novel and inventive water boiler enables cooling of flue gas through the critical temperature range of from about 350°C down to about 250°C which is favourable for formation of toxic dioxins and their precursors, with practically no formation of toxic dioxins and their precursors, which heretofore has been unattainable. The present invention also enables existing reengineered assemblies to process larger volumes of flue gas, or new gas cooler assemblies to be designed with a smaller size. ModificationsA person skilled in the art will be able to modify the flue gas cooler assembly according to the present invention. For example, the number and type of cooling devices 301, 302 and 303 in the evaporator section 300 may vary with varying parameters. Moreover, while the water boiler 401 has been illustrated as a single-pass water boiler, the boiler 401 can be provided with two or more passes. The boiler 401 can also be realized in the form of numerous boilers 401 arranged in parallel or in series. It should also be emphasized that the temperatures given shall not be interpreted as exact, but as indications of temperature levels or ranges. The temperature the design of the equipment chosen will affect the temperature profiles throughout the cooler. For example, the inlet temperature to water cooler 401 could be within the range 400°C to 430°C, which is different from the inlet temperature of > 350°C as indicated in Fig.1. However, the important aspect in accordance with the invention is to keep the flue gas in the critical temperature range of about 250-350°C with respect to dioxin formation as short as possible.While the illustration of the process and cooler unit in Fig.1 may lead the reader to interpret the gas flow to occur in particular directions, it should be noted that the gas flow could occur in upward direction as well as downward direction.While the maximum residence time of flue gas in water boiler 401 has been set to about 1 second, the minimum residence time is dependent on the pressure drop in flue gas across the water boiler 401. Hence, a person skilled in the art will chose a design that provides the desired residence time, e.g. about 0.5 s.
Claims
Claims1. Flue gas cooler assembly (100) for cooling flue gas from a combustion furnace, particularly a combustion furnace for combustion of solid material, including Refused Derived Fuel (RDF) for production of energy, wherein said flue gas cooler assembly (100) comprises:• an initial radiation chamber (200) with an inlet (201) and an outlet (204), said radiation chamber (200) being provided with water-filled walls (203),• an evaporator section (300) comprising a number of evaporators (301) and/or a number of super heaters (302, 303),• a second cooler section (400) with a flow duct having a gas flow direction (F) and provided with one or more water boilers (401), and• an economizer unit (500) exhibiting means (501) for additional cooling of flue gas,characterized in that said at least one or more water boilers (401) exhibit a closed casing (402) with one or more water inlets (403) and water outlets (404), a flue gas inlet (405), a flue gas outlet (406), a number of gas flow tubes (407) with one end in flow connection with said flue gas inlet (405) and an opposite end of the gas flow tubes (407) in flow connection with the flue gas outlet (406), wherein said gas flow tubes (407) are arranged with their respective longitudinal axis substantially along the gas flow direction (F).2. Process for cooling flue gas from a combustion furnace, particularly a combustion furnace for combustion of solid material, including Refused Derived Fuel (RDF) for production of energy, wherein the process comprises the following steps:• flowing the flue gas at a temperature above about 900°C through a radiation chamber (200) provided with water-cooled walls (203) to decrease the flue gas temperature to less than about 800°C,• flowing flue gas through an evaporator section (300) provided with a number of evaporators (301) and/or super heaters (302, 303) to bring the flue gas temperature down to about 350-400°C,• flowing flue gas through a second cooler section (400) exhibiting one or more water boilers (401),• flowing cooled flue gas through an economizer (500) exhibiting additional cooling devices to cool flue gas down to a temperature of about 150°C or less, and• ejecting cooled flue gas to the atmosphere,characterized inflowing flue gas through the cooler section provided with said at least one or more water boilers (401) according to claim 1, at a flow rate providing a residence time for flue gas flowing through said at least one water boiler (401) of less than about 1 second, and cool the flue gas to a temperature of less than about 250-260°C.3. The process of claim 2, wherein the residence time of flue gas in said at least on water boiler (401) is kept below about 0.8 seconds, particularly about 0.5-0.8 seconds.4. The process of claim 2, wherein the flue gas exits the evaporator section (300) at a temperature of about 300-430°C.5. The process of claim 2 or 3, wherein the flow rate of flue gas through said at least one water boiler (401) is about 20 m/s, particularly about 22 m/s.
Drawings

Priority

No priority

Patent classes

IPC classesF23J 15/06CPC classesF23J 15/06Y02E 20/363

Citations

JP 2005180880 A (A)EP 1273866 A1 (A1)CN 1584401 A ( A)US 5687657 A (A)

Applicants, owners and inventors

Applicants
AITOS GASIFICATION TECHNOLOGY AS
Schultz gate 2 7013 TRONDHEIM NO (TRONDHEIM Municipality, Trøndelag county)Org. number: 918020349Inventors
Helge Rosvold
Nardoskrenten 8 7032 TRONDHEIM NO (TRONDHEIM Municipality, Trøndelag county)

Agent

CURO AS
CURO AS

Org. number: 936803911

Name and address are automatically synchronized with the Brønnøysund Register Centre.

Open in The Brønnøysund Register Centre
Vestre Rosten 81 7075 TILLER NO (TRONDHEIM Municipality, Trøndelag county)
Org. number: 936803911
Reference: P20170837NO

Status history

Payment history

Oppositions and appeals

No oppositions or appeals

Administrative limitation

No administrative limitation

Liens and licences

No liens or licenses registered

Gazette entries

No Gazette entries foundOnly events from 2024.03.04 and onwards are shown.