Review Oxy-co-gasification of coal a

Review Oxy-co-gasification of coal and biomass in an integrated gasification combined cycle (IGCC) power plant
Antonio Valero, Sergio Uso ´n *
Centre for Research of Energy Resources and Consumptions (CIRCE), University of Zaragoza, Marı ´a de Luna 3, 50018 Zaragoza, Spain
Received 1 April 2005
Abstract
Oxy-gasification, or oxygen-blown gasification, enables a clean and efficient use of coal and opens a promising way to CO2 capture. Moreover, oxy-co-gasification with biomass implies the use of a renewable resource and additional CO2 reduction. Proper gasifier operation is a key issue in both techniques. A model of an entrained flow gasifier, validated with nearby 3000 actual steady- state operation data (4800 h), is used to study co-gasification of coal, petroleum coke and up to 10% of several types of biomass. As a result, influence of fuel variation in gasifier efficiency and modifications in operation that should be made in oxy-co-gasification are obtained. The model is also used to build reference operation maps (graphs where the main gasification parameters are related to the degrees of freedom that the operator has). A general method for building experimental operation maps only from plant data has also been applied to the gasifier. Tendencies of the maps are the same of those of the model-made maps. In conclusion, oxy-co-gasification is possible providing that operation is adapted. A validated model can be very useful to predict operation points for new fuel mixtures. Operation maps are practical tools that help to operate and diagnose a system (e.g. a gasifier). They allow to understand how it works, to optimise its operation and to avoid wrong operation that may cause plant shut off. q 2006 Elsevier Ltd. All rights reserved.
Keywords: Oxy-gasification; Oxy-co-gasification; Biomass; IGCC; Operation map; Optimisation
1. Introduction
Concerning CO2 capture, gasification will play a key role in the future. Within this context, we mean oxy- gasification as the gasification of coal by using oxygen and steam as gasifying agents. Since nitrogen has been previously removed, oxy-gasification, and subsequent gas cleaning processes, produce a gas stream mainly composed of CO and H2, which opens a promising way to CO2 capture. Moreover, when biomass is gasified with coal, and then CO2 is captured, the emission balance of this component can reduce substantially and even could become negative. Thus, we define oxy-co-gasification as the gasification of coal and biomass by using oxygen and steam as gasifying agents. This technique appears as a very promising way not only to reduce CO2 emissions but also to increase the biomass contribution to electricity generation.
Energy 31 (2006) 1643–1655
www.elsevier.com/locate/energy
0360-5442/$ - see front matter q 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.energy.2006.01.005
* Corresponding author. Tel.: C34 976 76 25 82; fax: C34 976 73 20 78. E-mail address: [e-mail] (S. Uso ´n).
1.1. From gasification to oxy-co-gasification
Gasification (with air) is usually used in small plants of several megawatts. These plants are suitable for using biomass because this is usually a disperse resource and transport can increase its cost. They are composed of a gasifier, a quite simple gas cleaning system and an internal combustion engine [1,2]. Another interesting option that can achieve higher efficiency is the use of biomass-fired air blown gasification combined cycle (ABGCC) power plants like the Va ¨rnamo, Arable Biomass Renewable Energy (ARBRE) and Thermie Energy Farm demonstration projects [1,3–5]. The first plant provided 6 and 9 MW to a district heating system, while the others generate 8 and 14 MW, respectively. Due to the complexity and cost of an air separation unit, oxy-gasification is used in large coal-fired IGCC power plants, and for the production of H2 and chemicals [6–8]. The composition of the cleaned gas (mainly CO and H2) opens the way to CO2 capture by using several techniques (although this possibility is not yet used). For example, a
Nomenclature
ac O2 coefficient in combustion equation bc CO coefficient in combustion equation cc CO2 coefficient in combustion equation CGE cold gas efficiency d distance daf dry and ash free d.b. dry basis dc H2O coefficient in combustion equation ec H2S coefficient in combustion equation fc N2 coefficient in combustion equation h hydrogen subscript in char formula hf hydrogen subscript in fuel formula HRSG heat recovery steam generator i real operation point j point in an iso-line k point in a four-point group LHV low heating value max maximum min minimum n nitrogen subscript in char formula nf nitrogen subscript in fuel formula o oxygen subscript in char formula of oxygen subscript in fuel formula p parameter s sulphur subscript in char formula sf sulphur subscript in fuel formula w moisture subscript in fuel formula w.b. wet basis wt weight x independent variable y independent variable z dependent variable 0 coordinate of point in a iso-line d increment
A. Valero, S. Uso ´n / Energy 31 (2006) 1643–16551644
shift reactor can displace the equilibrium to produce CO2 and H2, and then chemical absorption or membranes [9] can be used to separate the CO2. Another option consists on burning separately H2 and CO by using oxygen [10]. Finally, the gas could be burnt with O2 plus CO2 recycled from the same combustion process in the gas turbine. Oxy-co-gasification is similar to oxy-gasification but replacing part of the coal by biomass, which implies an additional CO2 emissions reduction. Oxy-co-gasification of coal with straw or sewage sludge in an IGCC has been studied by British Coal. The University of Essen researched the use of coal/biomass combinations for IGCC applications, concluding that up to 10% biomass in an oxygen-blown entrained blown gasifier is technically feasible although net electrical efficiencies would be slightly lower due to energy needed for biomass pre-treatment [11]. Oxy-co-gasification of coal and biomass in Buggenum IGCC Power Plant has also been proposed in a study that consists of two parts: preliminary desk study [12] and exploratory experimental work [13]. It should be noted that the combined use of biomass and coal in the same power plant allows to use biomass without the main problems of small biomass-fired power plants (high specific cost, low efficiency and shut-off risk if there is a biomass shortage). One way to do this is by burning coal and biomass (co-firing) [14]. Another option consists on gasifying biomass and burning the gaseous fuel in a coal boiler [2]. Finally, co-gasification, mainly oxy- co-gasification, allows increased efficiency and reduced environmental impact.
1.2. Gasifier operation in oxy-gasification and oxy-co-gasification
A key issue in oxy-gasification and oxy-co-gasification is the operation of an oxygen-blown gasifier. Proper gasifier operation is more critical than boiler operation, because it does not consist in just maximising efficiency but other issues, that in turn requires keeping several output variables (gas composition and gasification temperature) in correct ranges and maximising fuel/gas conversion by adjusting two input variables (oxygen and steam that are introduced in the gasifier). Gasification temperature is a variable that cannot be measured but has to be kept in a right range because it determines not only efficiency but also safe operation. An error in oxygen measurement could cause either very high temperatures that can damage the equipment or (in slagging gasifiers) low temperatures that can stop slag flow and blocking. Besides, although output variables could be considered separately, a modification in an input variable implies changes in all output variables, so that all dependencies should be understood and integrated. In oxy-co-gasification, fuel modification is an additional difficulty. In this work, the problem of gasifier operation in oxy-gasification and oxy-co-gasification is tackled. First, a validated model of the gasifier of an IGCC power plant is applied to simulate the oxy-co-gasification of coal, coke and up to 10% of several types of biomass, in order to obtain the operation strategies depending on the fuel mixture. Second, the operation maps are applied as a tool for improving gasifier operation. These maps constitute a graphic tool that helps to operate the gasifier in a safe and efficient way. They can be built by using a model or directly from plant data. The case of study is Elcogas IGCC Power Plant in Puertollano (Spain). This is a demonstration project where several European companies have worked together (it was selected as a target project of the THERMIE program of the European Union).
2. The model of the gasifier
2.1. Description of the gasifier
Puertollano IGCC power plant furnishes an efficient pressurised entrained flow (PRENFLO) gasifier built by Krupp-Koppers. The fuel is a mixture of high-ash local coal and high-sulphur petroleum coke at 50% in weight. A small amount of limestone (2%) is added to favour ash fluidisation. The gasifying agents are oxygen (85% purity) and steam. Fuel, oxygen and steam are introduced in the reaction chamber by using four burners. They react very quickly (residence time around few seconds) at high temperatures generating a combustible gas mainly composed of CO and H2 that leaves the reaction chamber by its upper part. Due to the high temperatures, the ash of the fuel becomes slag that flows to the bottom. Walls of the reaction chamber are cooled by boiling water (Fig. 1). Gas leaving the reaction chamber is quenched with a cold gas stream in order to stop gas phase reactions and enter the evaporators with adequate operation conditions.
A. Valero, S. Uso ´n / Energy 31 (2006) 1643–1655 1645
The gas is then cooled in a heat recovery steam generator (HRSG) to produce a temperature at which it can be cleaned. The HRSG consists of two boilers. The first one generates high-press

ผลลัพธ์ (ไทย) 1:

ตรวจทาน Oxy-co-gasification ของถ่านหินและชีวมวลในการ gasification รวมรวม (IGCC) โรงไฟฟ้าพลังงานวาเลโร Antonio, Sergio Uso ´n *ศูนย์วิจัยทรัพยากรพลังงานและปริมาณการใช้ (CIRCE), มหาวิทยาลัยของซาราโกซา Marı ´a เดอลูนา 3, 50018 ซาราโกซา สเปนได้รับ 1 2548 เมษายนบทคัดย่อOxy-gasification, or oxygen-blown gasification, enables a clean and efficient use of coal and opens a promising way to CO2 capture. Moreover, oxy-co-gasification with biomass implies the use of a renewable resource and additional CO2 reduction. Proper gasifier operation is a key issue in both techniques. A model of an entrained flow gasifier, validated with nearby 3000 actual steady- state operation data (4800 h), is used to study co-gasification of coal, petroleum coke and up to 10% of several types of biomass. As a result, influence of fuel variation in gasifier efficiency and modifications in operation that should be made in oxy-co-gasification are obtained. The model is also used to build reference operation maps (graphs where the main gasification parameters are related to the degrees of freedom that the operator has). A general method for building experimental operation maps only from plant data has also been applied to the gasifier. Tendencies of the maps are the same of those of the model-made maps. In conclusion, oxy-co-gasification is possible providing that operation is adapted. A validated model can be very useful to predict operation points for new fuel mixtures. Operation maps are practical tools that help to operate and diagnose a system (e.g. a gasifier). They allow to understand how it works, to optimise its operation and to avoid wrong operation that may cause plant shut off. q 2006 Elsevier Ltd. All rights reserved.Keywords: Oxy-gasification; Oxy-co-gasification; Biomass; IGCC; Operation map; Optimisation1. IntroductionConcerning CO2 capture, gasification will play a key role in the future. Within this context, we mean oxy- gasification as the gasification of coal by using oxygen and steam as gasifying agents. Since nitrogen has been previously removed, oxy-gasification, and subsequent gas cleaning processes, produce a gas stream mainly composed of CO and H2, which opens a promising way to CO2 capture. Moreover, when biomass is gasified with coal, and then CO2 is captured, the emission balance of this component can reduce substantially and even could become negative. Thus, we define oxy-co-gasification as the gasification of coal and biomass by using oxygen and steam as gasifying agents. This technique appears as a very promising way not only to reduce CO2 emissions but also to increase the biomass contribution to electricity generation.Energy 31 (2006) 1643–1655www.elsevier.com/locate/energy0360-5442/$ - see front matter q 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.energy.2006.01.005* Corresponding author. Tel.: C34 976 76 25 82; fax: C34 976 73 20 78. E-mail address: [e-mail] (S. Uso ´n).1.1. From gasification to oxy-co-gasificationGasification (มีแอร์) มักจะใช้ในพืชขนาดเล็กของหลายเมกะวัตต์ พืชเหล่านี้เหมาะสำหรับการใช้ชีวมวลเนื่องจากโดยปกติทรัพยากร disperse และขนส่งสามารถเพิ่มต้นทุน จะประกอบด้วย gasifier แก๊สค่อนข้างง่ายที่ทำความสะอาดระบบและเครื่องยนต์สันดาปภายใน [1, 2] อีกตัวเลือกที่น่าสนใจที่สามารถบรรลุสูง efficiency คือ การใช้ชีวมวล fired อากาศเป่าไฟฟ้าวงจร (ABGCC) gasification รวม Va ¨rnamo เพาะปลูกชีวมวลทดแทนพลังงาน (ARBRE) และโครงการสาธิตฟาร์มพลังงาน Thermie [1,3-5] โรงงาน first ให้ 6 และ 9 MW เป็นอำเภอ ระบบทำความร้อนในขณะที่คนอื่น ๆ สร้าง 8 และ 14 MW ตามลำดับ ความซับซ้อนและต้นทุนของหน่วยแยกอากาศ เชื้อ gasification จะใช้ ในโรงไฟฟ้า IGCC fired ถ่านหินขนาดใหญ่ และการผลิต H2 และเคมี [6-8] องค์ประกอบของก๊าซสะอาด (ส่วนใหญ่เป็น CO และ H2) เปิดตามการจับ CO2 โดยการใช้เทคนิคต่าง ๆ (แม้ว่าโอกาสนี้ไม่ได้ใช้) ตัวอย่าง การระบบการตั้งชื่อac O2 coefficient in combustion equation bc CO coefficient in combustion equation cc CO2 coefficient in combustion equation CGE cold gas efficiency d distance daf dry and ash free d.b. dry basis dc H2O coefficient in combustion equation ec H2S coefficient in combustion equation fc N2 coefficient in combustion equation h hydrogen subscript in char formula hf hydrogen subscript in fuel formula HRSG heat recovery steam generator i real operation point j point in an iso-line k point in a four-point group LHV low heating value max maximum min minimum n nitrogen subscript in char formula nf nitrogen subscript in fuel formula o oxygen subscript in char formula of oxygen subscript in fuel formula p parameter s sulphur subscript in char formula sf sulphur subscript in fuel formula w moisture subscript in fuel formula w.b. wet basis wt weight x independent variable y independent variable z dependent variable 0 coordinate of point in a iso-line d incrementA. Valero, S. Uso ´n / Energy 31 (2006) 1643–16551644shift reactor can displace the equilibrium to produce CO2 and H2, and then chemical absorption or membranes [9] can be used to separate the CO2. Another option consists on burning separately H2 and CO by using oxygen [10]. Finally, the gas could be burnt with O2 plus CO2 recycled from the same combustion process in the gas turbine. Oxy-co-gasification is similar to oxy-gasification but replacing part of the coal by biomass, which implies an additional CO2 emissions reduction. Oxy-co-gasification of coal with straw or sewage sludge in an IGCC has been studied by British Coal. The University of Essen researched the use of coal/biomass combinations for IGCC applications, concluding that up to 10% biomass in an oxygen-blown entrained blown gasifier is technically feasible although net electrical efficiencies would be slightly lower due to energy needed for biomass pre-treatment [11]. Oxy-co-gasification of coal and biomass in Buggenum IGCC Power Plant has also been proposed in a study that consists of two parts: preliminary desk study [12] and exploratory experimental work [13]. It should be noted that the combined use of biomass and coal in the same power plant allows to use biomass without the main problems of small biomass-fired power plants (high specific cost, low efficiency and shut-off risk if there is a biomass shortage). One way to do this is by burning coal and biomass (co-firing) [14]. Another option consists on gasifying biomass and burning the gaseous fuel in a coal boiler [2]. Finally, co-gasification, mainly oxy- co-gasification, allows increased efficiency and reduced environmental impact.1.2. Gasifier operation in oxy-gasification and oxy-co-gasification
A key issue in oxy-gasification and oxy-co-gasification is the operation of an oxygen-blown gasifier. Proper gasifier operation is more critical than boiler operation, because it does not consist in just maximising efficiency but other issues, that in turn requires keeping several output variables (gas composition and gasification temperature) in correct ranges and maximising fuel/gas conversion by adjusting two input variables (oxygen and steam that are introduced in the gasifier). Gasification temperature is a variable that cannot be measured but has to be kept in a right range because it determines not only efficiency but also safe operation. An error in oxygen measurement could cause either very high temperatures that can damage the equipment or (in slagging gasifiers) low temperatures that can stop slag flow and blocking. Besides, although output variables could be considered separately, a modification in an input variable implies changes in all output variables, so that all dependencies should be understood and integrated. In oxy-co-gasification, fuel modification is an additional difficulty. In this work, the problem of gasifier operation in oxy-gasification and oxy-co-gasification is tackled. First, a validated model of the gasifier of an IGCC power plant is applied to simulate the oxy-co-gasification of coal, coke and up to 10% of several types of biomass, in order to obtain the operation strategies depending on the fuel mixture. Second, the operation maps are applied as a tool for improving gasifier operation. These maps constitute a graphic tool that helps to operate the gasifier in a safe and efficient way. They can be built by using a model or directly from plant data. The case of study is Elcogas IGCC Power Plant in Puertollano (Spain). This is a demonstration project where several European companies have worked together (it was selected as a target project of the THERMIE program of the European Union).
2. The model of the gasifier
2.1. Description of the gasifier
Puertollano IGCC power plant furnishes an efficient pressurised entrained flow (PRENFLO) gasifier built by Krupp-Koppers. The fuel is a mixture of high-ash local coal and high-sulphur petroleum coke at 50% in weight. A small amount of limestone (2%) is added to favour ash fluidisation. The gasifying agents are oxygen (85% purity) and steam. Fuel, oxygen and steam are introduced in the reaction chamber by using four burners. They react very quickly (residence time around few seconds) at high temperatures generating a combustible gas mainly composed of CO and H2 that leaves the reaction chamber by its upper part. Due to the high temperatures, the ash of the fuel becomes slag that flows to the bottom. Walls of the reaction chamber are cooled by boiling water (Fig. 1). Gas leaving the reaction chamber is quenched with a cold gas stream in order to stop gas phase reactions and enter the evaporators with adequate operation conditions.
A. Valero, S. Uso ´n / Energy 31 (2006) 1643–1655 1645
The gas is then cooled in a heat recovery steam generator (HRSG) to produce a temperature at which it can be cleaned. The HRSG consists of two boilers. The first one generates high-press

ผลลัพธ์ (ไทย) 3:

รีวิวยา Co gasi จึงไอออนบวกของถ่านหินและชีวมวลในการบูรณาการการถ่ายทอด gasi วงจรรวม ( igcc ) โรงไฟฟ้า
อันโตนิโอ Valero เซอร์จิโอใช้ใหม่ N *
ศูนย์วิจัยพลังงานทรัพยากรและการบริโภค ( Circe ) มหาวิทยาลัย Zaragoza , มาร์ıใหม่ de Luna 3
ได้รับ 1 50018 Zaragoza , สเปน เมษายน 2005

Oxy gasi จึงบวกบทคัดย่อ หรือเป่า gasi จึงบวกออกซิเจน ,ช่วยให้ทำความสะอาดและ EF จึงใช้ cient ของถ่านหินและเปิดวิธีมีแนวโน้มในการดักจับก๊าซคาร์บอนไดออกไซด์ . นอกจากนี้ ยา Co gasi จึงบวกกับชีวมวล หมายถึง การใช้ทรัพยากรพลังงานหมุนเวียนและการลด CO2 เพิ่มเติม จึง gasi เหมาะสมปฏิบัติการแปลง ER เป็นปัญหาสำคัญในทั้ง 2 วิธี รูปแบบของ entrained flโอ๊ย gasi จึงเอ่อขึ้นใกล้เคียงกับ 3000 จริงมั่นคง - การดำเนินการข้อมูล ( 4 ชั่วโมง )ถูกใช้เพื่อศึกษาการถ่ายทอด Co gasi ถ่านหินโค้ก และถึง 10% ของหลายประเภทของชีวมวล ปิโตรเลียม ผลของการเปลี่ยนแปลงในfl uence เชื้อเพลิงใน gasi จึงเอ้อ EF และถ่ายทอดประสิทธิภาพในการถ่ายทอดสาร Modi ที่ควรจะทำในการ gasi Oxy Co จึงจะรับรูปแบบ นอกจากนี้ยังใช้ในการสร้างแผนที่อ้างอิงการดําเนินงาน ( กราฟที่หลัก gasi จึงบวกค่าพารามิเตอร์ที่เกี่ยวข้องกับองศาของเสรีภาพที่ผู้ประกอบการได้ ) วิธีการทั่วไปสำหรับการสร้างแผนที่ทดลองเท่านั้น จากข้อมูลพืชยังได้รับการใช้ใน gasi จึงเอ้อ แนวโน้มของแผนที่จะเหมือนกันที่แบบสร้างแผนที่ สรุปยาประจุ Co gasi จึงเป็นไปได้ให้ดำเนินการคือ การปรับ ผ่านรูปแบบจะมีประโยชน์มากเพื่อทำนายการดำเนินงานจุดของผสมเชื้อเพลิงใหม่ แผนที่การดำเนินงานเป็นเครื่องมือในทางปฏิบัติที่ช่วยให้การใช้งานและวิเคราะห์ระบบ ( เช่น gasi จึงเอ้อ ) จะช่วยให้เข้าใจวิธีการทำงานเพื่อเพิ่มประสิทธิภาพการดำเนินงาน และเพื่อหลีกเลี่ยงการผิดพลาดอาจทำให้โรงงานปิดQ 2006 เอลส์ จำกัด .
คำสำคัญ : Oxy gasi จึงบวก ; ยา Co gasi จึงบวกมวลชีวภาพ การเพิ่มประสิทธิภาพ igcc ; แผนที่ ;
1 ความรู้เบื้องต้นเกี่ยวกับ CO2
gasi จึงจับไอออนบวกจะมีบทบาทสำคัญในอนาคต ในบริบทนี้เราหมายถึง Oxy - gasi ประจุบวกจึงเป็น gasi จึงถ่านหินโดยใช้ออกซิเจนและไอน้ำเป็น gasifying ตัวแทน เนื่องจากไนโตรเจนที่ได้รับก่อนหน้านี้ออกซี จึง gasi ไอออนบวก และกระบวนการต่อมาก๊าซซักแห้ง , ผลิตก๊าซกระแสส่วนใหญ่ประกอบด้วยโคบอลต์และ H2 ซึ่งเปิดวิธีมีแนวโน้มในการดักจับก๊าซคาร์บอนไดออกไซด์ . นอกจากนี้ เมื่อชีวมวลเป็น gasi จึงเอ็ดกับถ่านหิน และการปล่อย CO2 จะถูกจับ ปรับสมดุลขององค์ประกอบนี้สามารถลดอย่างมาก และแม้อาจกลายเป็นลบ ดังนั้น