US20080223267A1 - Direct sorbent preparation/feed apparatus and method for circulating fluidized bed boiler systems - Google Patents

Direct sorbent preparation/feed apparatus and method for circulating fluidized bed boiler systems Download PDF

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Publication number
US20080223267A1
US20080223267A1 US11/685,447 US68544707A US2008223267A1 US 20080223267 A1 US20080223267 A1 US 20080223267A1 US 68544707 A US68544707 A US 68544707A US 2008223267 A1 US2008223267 A1 US 2008223267A1
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United States
Prior art keywords
sorbent
boiler
dryer
dryer apparatus
fluidized bed
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Abandoned
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US11/685,447
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English (en)
Inventor
Robert Van Etten Jacobs
James F. Durant
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General Electric Technology GmbH
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Alstom Technology AG
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Priority to US11/685,447 priority Critical patent/US20080223267A1/en
Assigned to ALSTOM POWER INCORPORATED reassignment ALSTOM POWER INCORPORATED ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: DURANT, JAMES F., JACOBS, ROBERT VAN ETTEN
Assigned to ALSTOM TECHNOLOGY LTD reassignment ALSTOM TECHNOLOGY LTD CORRECTIVE ASSIGNMENT TO CORRECT THE TO CORRECT THE ASSIGNEE'S NAME FROM ALSTOM POWER INCORPORATED TO ALSTOM TECHNOLOGY LTD. PREVIOUSLY RECORDED ON REEL 019003 FRAME 0684. ASSIGNOR(S) HEREBY CONFIRMS THE CORRECTED ASSIGNMENT. Assignors: DURANT, JAMES F., JACOBS, ROBERT VAN ETTEN
Priority to EP08727709A priority patent/EP2118568A1/en
Priority to PCT/US2008/051114 priority patent/WO2008112339A1/en
Priority to CN2008800080973A priority patent/CN101641553B/zh
Publication of US20080223267A1 publication Critical patent/US20080223267A1/en
Abandoned legal-status Critical Current

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES 
    • F23J7/00—Arrangement of devices for supplying chemicals to fire

Definitions

  • the present disclosure relates generally to circulating fluidized bed (CFB) combustion systems and, more particularly, to an improved direct sorbent preparation/feed apparatus and method for a CFB boiler system.
  • CFB circulating fluidized bed
  • Fluidized bed combustion is a combustion technology used in power plants primarily to burn solid fuels. FBC plants are more flexible than conventional plants in that they can be fired on coal, coal waste or biomass, among other fuels.
  • the term FBC covers a range of fluidized bed processes which include Circulating Fluidized Bed (CFB) boilers, Bubbling Fluidized Bed (BFB) boilers and other variants. Fluidized beds suspend solid fuels on upward-blowing jets of air during the combustion process, resulting in a turbulent mixing of gas and solids. The tumbling action, much like a bubbling fluid, provides a means for more effective chemical reactions and heat transfer.
  • FBC reduces the amount of sulfur emitted in the form of SO 2 by a desulfurization process.
  • a suitable sorbent such as limestone containing CaCO 3 , for example, is used to absorb SO 2 from the flue gas during combustion.
  • FBC combustion operates at temperatures lower than conventional combustion systems. FBC systems operate in a range typically between about 780° C. and about 1000° C. Since this allows coal to combust at cooler temperatures, NO x production during combustion is lower than other coal combustion processes. Fluidized-bed boilers evolved from efforts to find a combustion process able to control pollutant emissions without external emission controls (such as scrubbers).
  • CFB boiler systems are generally associated with limestone feed systems for sulfur capture.
  • Processed limestone fed to a boiler is typically conditioned by means of size reduction machines to specific size ranges to allow for the desulfurization process to proceed efficiently. If the particles are too large, the desulfurization process will not be efficient because there is insufficient limestone particle surface area to react with the flue gas. On the other hand, if the particles are too small, the limestone will be carried out of the desulfurization zone with the flue gas before it can react to remove the sulfur.
  • limestone is fed to the boiler with a median particle diameter in the range of (as an example, but not limited to) about 100 to about 400 microns.
  • raw limestone is reduced in both size and moisture content by size reducing machines.
  • machines available for crushing limestone including for example, hammer mills, roll crushers and roller mills. Regardless of the type of equipment used for limestone crushing, the particles are dried either before or during crushing in order to produce a freely flowing material.
  • CFB boilers may be equipped with an integrated limestone preparation and feed system that resides in the boiler building. Such a system that dries and prepares limestone as needed is also referred to a Just-In-Time (JIT) limestone system.
  • JIT Just-In-Time
  • Roller mill systems utilize hot air (mill air) for drying of limestone and transportation to the CFB.
  • Mill air is typically obtained from the primary air stream as the mills utilize air at elevated pressures.
  • hot primary air in the range of about 400° F. to about 600° F. is typically available.
  • the hot air is used to dry the entering limestone, sweep the limestone out of the mill, and convey it to the boiler.
  • the operating temperatures thereof are kept relatively low, for example in the range of about 170° F. to about 200° F.
  • limestone generally contains low quantities of moisture (e.g., less than 5%).
  • the air temperature entering the roller mills is a function of the acceptable mill mechanical operating temperature, the limestone moisture content, and the ratio of air to limestone.
  • air temperatures entering the mill will generally be less than about 250° F. Therefore, given the available primary air temperature in the range of about 500° F., the mill air obtained from the primary air stream is therefore tempered in order to produce a mill exit air temperature, typically in the range of about 180° F. to 225° F.
  • a sorbent conditioning and feed apparatus for a circulating fluidized bed combustion system includes a dryer apparatus configured to dry unprocessed sorbent material transported thereto from a raw storage container; a sorbent crushing device configured to reduce the particle size of dried sorbent material discharged from the dryer apparatus; and a circulating fluidized bed (CFB) boiler configured to receive processed sorbent material conveyed from the sorbent crushing device; wherein the dryer apparatus utilizes an untempered hot air source diverted directly from a primary air stream input to the circulating fluidized bed boiler.
  • CFB circulating fluidized bed
  • a direct limestone conditioning and feed apparatus for a circulating fluidized bed combustion system includes a dryer apparatus configured to dry unprocessed limestone material transported thereto from a raw storage container; a roll crushing device configured to reduce the particle size of dried limestone material discharged from the dryer apparatus; and a circulating fluidized bed (CFB) boiler configured to receive processed limestone material conveyed from the roll crushing device; wherein the dryer apparatus utilizes an untempered hot air source diverted directly from a primary air stream input to the circulating fluidized bed boiler.
  • CFB circulating fluidized bed
  • a method of conditioning and feeding sorbent material for a circulating fluidized bed combustion system includes transporting raw, unprocessed sorbent material from a raw storage container to a dryer apparatus; diverting untempered hot air directly from a primary air stream input to the circulating fluidized bed boiler, the untempered hot air used to dry the raw sorbent material; directing dried raw sorbent material from the dryer apparatus to a crushing device configured to reduce the particle size of the dried raw sorbent material discharged from the dryer apparatus; and conveying processed sorbent material from the crushing device to the CFB boiler.
  • FIG. 1 is a schematic block diagram of an existing sorbent preparation/feed apparatus, including a roller mill which utilizes tempered air to dry and separate sorbent material;
  • FIG. 2 is a schematic block diagram of an improved direct sorbent preparation/feed apparatus and method for a CFB boiler system, utilizing untempered air for sorbent drying, in accordance with an embodiment of the invention.
  • FIG. 3 is a schematic diagram of a CFB boiler system incorporating an improved direct sorbent preparation/feed apparatus, utilizing untempered air for sorbent drying, in accordance with a further embodiment of the invention.
  • a sorbent preparation/feed apparatus utilizes an alternate crushing device (i.e., one that does not need the use of tempered air) with a separate, high temperature dryer apparatus in order to supply dry, sized limestone on a just-in-time basis to a CFB boiler without reducing boiler efficiency.
  • an alternate crushing device i.e., one that does not need the use of tempered air
  • a separate, high temperature dryer apparatus in order to supply dry, sized limestone on a just-in-time basis to a CFB boiler without reducing boiler efficiency.
  • CFB boilers equipped with roller mill JIT limestone systems employ tempering air in order to control the entering air temperature, which results in reduced heat recovery from the flue gas.
  • the reduced heat recovery in turn lowers boiler efficiency (e.g., on the order of about 1%) and thus increases equipment size and operating costs.
  • a JIT system incorporating one or more roll crushers and utilizing a separate limestone drying apparatus eliminates the use of tempering air, thus allowing for maximum heat recovery from a boiler air heater.
  • Primary Air in the context of FBC boilers, refers to combustion air delivered to the bed fluidization grate at the bottom of the furnace. Primary air is generated at relatively high pressures. In addition, some primary air may be diverted to other equipment, as well as enter the furnace at locations other than the grate. Furthermore, in the context of FBC boilers, “Secondary Air” (SA) refers to combustion air delivered through openings in the furnace walls. Secondary air is generated at pressures lower than primary air, and is used to fluidize the bed and stage combustion for emission control. “Tempered Air” refers to hot air that is cooled (i.e., tempered) with relatively cold air, such as ambient air for example.
  • Untempered hot air refers to hot air leaving an air heater of the FBC system. Both primary air and secondary air leaving the air heater are considered untempered hot air streams.
  • Unprocessed Sorbent refers to raw sorbent delivered to the FBC boiler conditioning (size reduction & drying) system. Unprocessed sorbent has not been conditioned to the proper size and moisture content required for feeding to the FBC boiler.
  • FIG. 1 there is shown a schematic block diagram of an existing sorbent preparation/feed apparatus 100 .
  • the apparatus 100 utilizes a roller mill 102 to both dry and separate the raw sorbent material.
  • hot primary air (PA) exiting the boiler system air heater 104 is mixed with tempering air (e.g., from cold primary air entering the air heater 104 ) so as to produce tempered primary air for input to the roller mill 102 .
  • tempering air e.g., from cold primary air entering the air heater 104
  • dampers 106 may be utilized in the hot primary air path and the tempering air path in order to produce the tempered air of a desired temperature and pressure.
  • FIG. 1 For purposes of illustration, FIG.
  • FIG. 1 further illustrates additional inputs and outputs of the air heater 104 , including cold input secondary air (SA), hot secondary air output to a CFB boiler (not shown), hot gas input to the heater 104 from a boiler backpass heat exchanger 108 , and exiting warm flue gas.
  • SA cold input secondary air
  • CFB boiler CFB boiler
  • One reason for requiring tempered air in a conventional roller mill preparation/feed apparatus 100 relates to the temperature limits of the crushing device (roller mill) itself.
  • the velocity of the air conveying the conditioned limestone from the roller mill to the CFB boiler is controlled. If, for example, the velocity of the conveying air is too low, sorbent particles may settle out in the pipe, leading to blockage.
  • FIG. 2 is a schematic block diagram of an improved direct sorbent preparation/feed apparatus 200 for a CFB boiler system, utilizing untempered air for sorbent drying, in accordance with an embodiment of the invention.
  • the apparatus 200 utilizes a sorbent dryer 202 and separate roll crusher device 204 .
  • the wet, raw sorbent is received into the sorbent dryer 202 , wherein hot, untempered primary air (e.g., on the order of 400° F. or higher is directly input to the dryer 202 to dry the wet, raw sorbent.
  • hot, untempered primary air e.g., on the order of 400° F. or higher is directly input to the dryer 202 to dry the wet, raw sorbent.
  • the sorbent dryer 202 is configured to discharge warm air, which carries sorbent fines (fine particles) directly to the boiler, thus bypassing the roll crusher device 204 .
  • the sorbent dryer 202 has a particle separation capability.
  • the remaining dry, raw sorbent that is not already of a fine particulate size is input from the sorbent dryer 202 to the roll crusher 204 .
  • the need to temper the air used to dry the particles is eliminated.
  • the dry, raw sorbent particles are conditioned (i.e., reduced to the desired size), they are conveyed (e.g., pneumatically or mechanically) to the boiler (not shown in FIG. 2 ) in accordance with a direct (JIT) feed system.
  • FIG. 3 is a schematic diagram of a CFB boiler system 300 incorporating an improved direct sorbent preparation/feed apparatus (such as apparatus 200 of FIG. 2 , for example), utilizing untempered air for sorbent drying, in accordance with a further embodiment of the invention.
  • the system 300 further includes a CFB boiler 302 , a raw sorbent (e.g., limestone) storage facility/container 304 and cyclone 306 .
  • Raw, wet limestone is conveyed from the storage container 304 , is metered and conveyed to the dryer 202 .
  • limestone metering may be controlled by sulfur reduction signals received from the associated boiler control system.
  • hot, untempered air from the primary air system is directly used as the source of heat to dry the limestone, wherein only enough hot air is diverted from the primary air stream to the dryer 202 as may be needed to dry the limestone.
  • the dryer 202 having the capability of operating at high temperatures, is therefore is not subject to tempering.
  • the dryer 202 may include a particle separation capability so as to remove sorbent fines with exiting warm air to the boiler, thereby preventing an unnecessary feeding of sorbent fines into the roll crusher 204 .
  • One exemplary type of dryer in this regard may be a fluidized bed dryer. However, other types of high-temperature dryers may also be used.
  • warm air containing evaporated water and limestone dust (sorbent fines) is conveyed directly to the boiler 302 as part of the combustion air.
  • limestone discharged from the dryer 202 is conveyed to one or more roll type crushers 204 arranged in series where it is crushed to a desired size and discharged.
  • the dried, sized limestone is conveyed (e.g., pneumatically or mechanically) to the CFB boiler 302 .
  • the system 300 may also include surge hoppers and metering systems downstream of the roll crusher 304 to enhance system operation and flexibility.
  • the total amount of pressurized primary air in the system may be reduced. Because the elimination of tempering air reduces the amount of primary air needed to dry the sorbent, the total primary air is reduced and replaced by lower pressure secondary air.
  • the above exemplary embodiments further improve particle size distribution of the conditioned limestone to the CFB boiler.
  • limestone (sorbent) to the boiler requires a specific range of sizes for optimum sulfur capture. If the size distribution becomes coarser, the quantity of unused sorbent rises. Larger particles are not sufficiently broken down in the furnace before removal, thus resulting in a greater amount of unused sorbent. On the other hand, if the size distribution becomes too fine, the quantity of unused sorbent rises due to reduced residence time for the sulfur capture reactions.
  • the disclosed embodiments reduce the amount of high pressure air (primary and tempering) in the CFB system. This reduction is obtained primarily by using higher temperature air to dry the sorbent. The reduction lowers total power consumption of the air fans, which in turn improves boiler economics. For example, the use of primary air at a maximum air heater outlet temperature maximizes energy recovery from the flue gas, thus increasing boiler efficiency with respect to a JIT system using tempering air. As the boiler efficiency is significantly increased, a long-term savings in plant operating costs is realized. By way of example, the boiler efficiency may be increased in the range of about 0.5% to about 1.5%.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Air Supply (AREA)
  • Treating Waste Gases (AREA)
  • Solid-Sorbent Or Filter-Aiding Compositions (AREA)
US11/685,447 2007-03-13 2007-03-13 Direct sorbent preparation/feed apparatus and method for circulating fluidized bed boiler systems Abandoned US20080223267A1 (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
US11/685,447 US20080223267A1 (en) 2007-03-13 2007-03-13 Direct sorbent preparation/feed apparatus and method for circulating fluidized bed boiler systems
EP08727709A EP2118568A1 (en) 2007-03-13 2008-01-16 Improved direct sorbent preparation/feed apparatus and method for circulating fluidized bed boiler systems
PCT/US2008/051114 WO2008112339A1 (en) 2007-03-13 2008-01-16 Improved direct sorbent preparation/feed apparatus and method for circulating fluidized bed boiler systems
CN2008800080973A CN101641553B (zh) 2007-03-13 2008-01-16 改进的直接吸收剂制备/进给设备和循环流化床锅炉系统的方法

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US11/685,447 US20080223267A1 (en) 2007-03-13 2007-03-13 Direct sorbent preparation/feed apparatus and method for circulating fluidized bed boiler systems

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EP (1) EP2118568A1 (zh)
CN (1) CN101641553B (zh)
WO (1) WO2008112339A1 (zh)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104338422A (zh) * 2013-07-29 2015-02-11 碧水蓝天环境工程有限公司 脱硫装置及脱硫方法
CN106168377A (zh) * 2016-08-15 2016-11-30 南京工程学院 一种锅炉热烟气点火装置
CN114857577A (zh) * 2022-04-28 2022-08-05 江苏运能能源科技有限公司 一种实现热渣输送再利用的自动化气动输送装置及工艺

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CN102297439A (zh) * 2011-07-05 2011-12-28 哈尔滨工业大学 一种超低温排烟节能锅炉
CN104548920B (zh) * 2014-12-03 2017-02-22 河南神马尼龙化工有限责任公司 一种脱硫装置及脱硫方法
CN106693629A (zh) * 2017-02-28 2017-05-24 重庆三峰环境产业集团有限公司 一种减少垃圾焚烧飞灰产生量的系统及方法

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US4292742A (en) * 1978-06-21 1981-10-06 Stal-Laval Turbin Ab Plant for drying fuel
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US5950322A (en) * 1996-12-23 1999-09-14 Firma Starcosa-Tag, Division Of Braunschweigische Maschinenbauanstalt Ag Drier with exhaust gas purification
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US20030150365A1 (en) * 2002-02-11 2003-08-14 Alstom (Switzerland) Ltd Sorbent conditioning and direct feed apparatus for a steam generator and a method for retrofitting a steam generator with same
US20060075682A1 (en) * 2004-10-12 2006-04-13 Great River Energy Method of enhancing the quality of high-moisture materials using system heat sources

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US3190627A (en) * 1963-01-07 1965-06-22 Phillips Petroleum Co Process and apparatus for drying solids
US4292742A (en) * 1978-06-21 1981-10-06 Stal-Laval Turbin Ab Plant for drying fuel
US5575984A (en) * 1994-06-09 1996-11-19 Abb Environmental Systems, Div. Of Abb Flakt, Inc. Method for preparing calcium carbonate for scrubbing sulfur oxides from combustion effluents
US5950322A (en) * 1996-12-23 1999-09-14 Firma Starcosa-Tag, Division Of Braunschweigische Maschinenbauanstalt Ag Drier with exhaust gas purification
US6058619A (en) * 1997-09-23 2000-05-09 Andritz-Patentverwaltungs-Gesellschaft M.B.H. Process and apparatus for drying material with indirectly heated driers and for decontaminating waste gas
US20030150365A1 (en) * 2002-02-11 2003-08-14 Alstom (Switzerland) Ltd Sorbent conditioning and direct feed apparatus for a steam generator and a method for retrofitting a steam generator with same
US6615750B2 (en) * 2002-02-11 2003-09-09 Alstom (Switzerland) Ltd Sorbent conditioning and direct feed apparatus for a steam generator and a method for retrofitting a steam generator with same
US20060075682A1 (en) * 2004-10-12 2006-04-13 Great River Energy Method of enhancing the quality of high-moisture materials using system heat sources

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104338422A (zh) * 2013-07-29 2015-02-11 碧水蓝天环境工程有限公司 脱硫装置及脱硫方法
CN106168377A (zh) * 2016-08-15 2016-11-30 南京工程学院 一种锅炉热烟气点火装置
CN114857577A (zh) * 2022-04-28 2022-08-05 江苏运能能源科技有限公司 一种实现热渣输送再利用的自动化气动输送装置及工艺

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CN101641553B (zh) 2012-02-15
CN101641553A (zh) 2010-02-03
EP2118568A1 (en) 2009-11-18
WO2008112339A1 (en) 2008-09-18

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