Experimental and model investigation on the mass balance of a dry circulating fluidized bed for flue gas desulfurization system

Yuan Li,Changfu You 한국화학공학회 2011 Korean Journal of Chemical Engineering Vol.28 No.9

A moderate temperature dry circulating fluidized bed flue gas desulfurization (CFB-FGD) process was developed using rapidly hydrated sorbent. This technique has the advantages of low cost, no water consumption, and a valuable dry product CaSO_4. To keep the system operation stable, a mass balance model, based on cell model considering flow state, particle abrasion, particle residence time, particle segregation and desulfurization processes, was built to predict the system state and optimize the operating condition. Experimental studies were conducted on a pilotscale CFB-FGD system with rapidly hydrated sorbent made from CFB circulating ash and lime (circulating ash sorbent)or coal fly ash and lime (coal fly ash sorbent). Calculated results were compared with experimental results and the relative error was less than 10%. The results indicated that feed sorbent mass, feed sorbent size, superficial gas velocity, particle abrasion coefficient and cyclone efficiency had significant influence on the mass balance of CFB system. The circulating ash sorbent was better than the coal fly ash sorbent, for providing higher desulfurization efficiency and being better for the CFB-FGD system to achieve mass balance.

화학기상증착시킨 이산화 티탄(TiO₂)의 가시광 조사에 의한 유기성 폐수 처리

김영규 ( Young-kyu Kim ),송재환 ( Jae-hwan Song ),박재현 ( Jae-hyeon Park ) 한국환경기술학회 2006 한국환경기술학회지 Vol.7 No.4

본 연구의 목적은 가시광/TiO₂ 광촉매를 이용하여 반영구적으로 사용할 수 있는 광촉매의 효능을 면밀히 검토하고 난분해성 물질인 페놀과 유기화합물의 아세트산을 실험에 사용하여 유기물 제거 효과를 보았다. 페놀에 의한 COD_Cr 100mg/L에서 alumina bead 50g과 glass bead 30g을 넣어 형광등 빛을 조사하여 시간별 제거효율을 조사한 결과, glass-Ⅱ에서는 COD_Cr이 15~27%, alumina-Ⅱ에서 30~45% 정도로 난분해성 물질의 분해율은 glass bead에서 64.3%, alumina bead에서 83.3%로 약 30%의 증가를 보여 alumina beads가 난분해성 물질 제거에 유리한 것으로 확인되었다. Acetic acid로 COD_Cr 100mg/L을 조제하였을 때는 glass-Ⅱ가 56%로 alumina-Ⅱ의 48%보다 높은 효율을 보였다. 각 bead의 부피를 같게 하기 위해 bead의 양을 달리한 유기물 제거 정도 분석에서 alumina bead의 효율은 25g에서 제거 효율이 현저히 낮았으며 75g에서는 50g과 거의 같은 효율을 보였고, glass bead의 경우에는 15g에서 제거효율이 현저히 낮았으며 30g과 45g에서대등한 효율을 보였다. 일정공간에서 광촉매가 많다고 해도 OH라디칼의 생성은 거의 같음을 알 수 있었다. 본 연구에서 제작된 광촉매는 일반 가시광에서도 충분한 유기물 제거 정도를 나타내었다. 이상의 결과로 유동층 화학기상증착법(CFB-CVD)에 의해 제조된 TiO₂ 광촉매는 유기물 분해에 유효한 것으로 판단되었으며 일반적인 자외선 조사가 아닌 미량의 자외선 조사를 하는 형광등에서도 유기물 제거가 충분한 것으로 입증되었다. The purpose of this study is to make a novel TiO₂ photocatalyst which can used by visible light semipermanently and to determine an organic removal capacity for this one. In order to determine organic removal efficiency for a novel TiO₂ photocatalyst made by CFB-CVD (Circulating Fluidized Bed Chemical Vapor Deposition) method, experiments were carried out by using phenol and acetic acid as a non-biodegradable, biodegradable compound, and the visible light from blue fluorescent lamp. According to elapsed time of visible light irradiation on TiO₂ photocatalysts consisted with alumina bead 50g, glass bead 30g in COD_Cr 100mg/L, CODCr removal efficiencies were recorded 15~27% in glass-Ⅱ, 30~45% alumina-Ⅱ respectively. And the decomposition rates of non-degradable compounds were calculated as 64.3% on glass beads and 83.3% on alumina beads. On the experiments of COD_Cr 100mg/L by acetic acid, its removal rates showed as 56% on glass-Ⅱ and 48% on alumina-Ⅱ. From the results, the novel TiO₂ photocatalyst made by CFB-CVD method was founded to be effective in decomposing the organic matter on a lesser of ultraviolet lays.

석탄화력 발전소에서 순산소 연소기술개발 동향

이재구 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.1

순산소 연소기술은 화력발전소에서 CO₂ 포집기술 중 하나로 개발되고 있다. 공기대신에 순산소를 사용하는 방식으로, 실제 화력발전소에서는 화염온도 제어를 위하여 순산소와 연소배가스 일부를 재순환, 혼합하여 사용하고 있다. 순산소 연소발전소는 공기분리장치-보일러-연소배가스처리-CO₂ 처리공정 순서로 구성된다. 석탄을 연소하여 터빈용 스팀을 생산하는 보일러로는 미분탄(Pulverized Coal) 보일러와 순환유동층(Circulating Fluidized Bed) 보일러가 이용되고 있다. 연소보일러 차이에 따라 순산소 연소를 위한 핵심기술 개발내용이 달라지며, 배기가스 오염정도에 따라 배가스 재순환 공정설계가 달라진다. 본 발표에서는 세계적으로 순산소 연소기술개발 현황과 연구단에서 진행 중인 CFB 보일러에서 순산소 연소기술 개발방향을 소개하고자 한다.

CFB 모드에 기반한 2 차원 페이지 데이터의 광학적 암호화 응용

길상근,Gil, Sang-Keun 한국전기전자학회 2015 전기전자학회논문지 Vol.19 No.3

본 논문은 CFB(Cipher Feedback) 모드에 기반한 2 차원 페이지 데이터의 광학적 암호화 응용 시스템을 제안한다. 광학적으로 구현된 CFB 암호화 시스템은 2 차원 페이지 데이터 암호화를 위해 자유공간 광 연결 이중 인코딩 기법을 이용한다. 또한, 제안된 방법은 기존의 1 차원 암호화키를 처리하는 CFB 방식보다 2 차원 페이지 단위로 배열된 매우 큰 암호화키를 제공하기 때문에 암호강도가 한층 더 강화된 암호화 시스템을 구현한다. 제안한 CFB 알고리즘의 성능을 검증하기 위해 컴퓨터 시뮬레이션을 통하여 2 차원 페이지 데이터의 암호화 및 복호화 과정을 보여주고 오차 분석을 수행하였다. 시뮬레이션 결과, 제안한 CFB 방식은 기존의 1 차원 블록 방식보다 데이터 처리용량과 긴 암호화키를 가지는 강력한 광학적 페이지 암호화 시스템을 가능하게 한다. This paper proposes an optical cryptography application to 2-D page-oriented data based on CFB(Cipher Feedback) mode algorithm. The proposed method uses a free-space optical interconnected dual-encoding technique which performs XOR logic operations in order to implement 2-D page-oriented data encryption. The proposed method provides more enhanced cryptosystem with greater security strength than the conventional CFB block mode with 1-D encryption key due to the huge encryption key with 2-D arrayed page type. To verify the proposed method, encryption and decryption of 2-D page data and error analysis are carried out by computer simulations. The results show that the proposed CFB optical encryption system makes it possible to implement stronger cryptosystem with massive data processing and long encryption key compared to 1-D block method.

Co-combustion of Korean anthracite with bituminous coal in two circulating fluidized bed combustors

Jong Min Lee,Dong Won Kim,Jae Sung Kim,Jong Jin Kim 한국화학공학회 2007 Korean Journal of Chemical Engineering Vol.24 No.3

co-combustion characteristics for Korean anthracites and bituminous coals were determined in a lab-scale CFB reactor and the comercial scale Tonghae CFB Power Plant. In the lab-scale CFB combustion tests, thewhen each coal burned. As the bituminous coal was added, however, the effluent rate of the emissions increased. Theamount of the unburned carbon in ash decreased with increasing the ratio of the bituminous coal during the co-com-bustion. When the co-combustion was tested in the Tonghae CFB power plant, the temperatures at the upper part ofthe combustor and the cyclones, which were somewhat higher than designed and expected, could be reduced as thebituminous coal ratio increased. Consequently, more stable operation of the CFB boiler was achieved. The efficiency

Prediction of Axial Solid Holdups in a CFB Riser

박상순,채호정,김태완,정광은,김철웅,정순용,임종훈,박영권,이동현 한국화학공학회 2018 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.56 No.6

A circulating fluidized bed (CFB) has been used in various chemical industries because of good heat and mass transfer. In addition, the methanol to olefins (MTO) process requiring the CFB reactor has attracted a great deal of interest due to steep increase of oil price. To design a CFB reactor for MTO pilot process, therefore, we has examined the hydrodynamic properties of spherical catalysts with different particle size and developed a correlation equation to predict catalyst holdup in a riser of CFB reactor. The hydrodynamics of micro-spherical catalysts with average particle size of 53, 90 and 140 mm was evaluated in a 0.025 m-ID x 4 m-high CFB riser. We also developed a model described by a decay coefficient to predict solid hold-up distribution in the riser. The decay coefficient developed in this study could be expressed as a function of Froude number and dimensionless velocity ratio. This model could predict well the experimental data obtained from this work.

무선 통신망 암호동기에 적합한 Statistical CFB 방식의 암호 알고리즘 성능 분석

박대선,김동수,김영수,윤장홍,Park Dae-seon,Kim Dong-soo,Kim Young-soo,Yoon Jang-hong 한국정보통신학회 2005 한국정보통신학회논문지 Vol.9 No.7

본 논문에서는 통신 채널의 오류로 인하여 통신 단말간에 서로 송수신되는 정보중에 임의의 비트가 삭제되거나 추가되어 암호 알고리즘을 사용하여 통신이 불가능해지는 경우, 이를 극복하기 위한 기법으로 Statistical CFB 방식의 암호 알고리즘을 제안한다. 먼저, 비트 삽입 또는 비트 삭제 발생 시 오류 전파의 영향을 수학적으로 모델링하여 이론적인 Statistical CFB 암호 알고리즘의 성능을 분석한다. 이 경우, Statistical CFB 방식의 성능을 결정하는 요소인 농기 패턴의 길이와 피프백되는 키의 길이를 변화해가며 분석하도록 한다. 또한 이론적인 분석과 함께 실제로 특정 길이의 동기 패턴과 피드백되는 키를 선택한 후, Statistical CFB 방식을 적용한 암호 알고리즘을 사용하여 성능을 분석하였다. 이를 이론적인 분석 결과와 비교하여 제안된 암호 알고리즘의 타당성을 검증한다. This paper suggests a new cipher mode of operation which can recover cryptographic synchronization. First, we study the typical cipher modes of operation, especially focused on cryptographic synchronization problems. Then, we suggest a statistical cipher-feedback mode of operation. We define the error sources mathmatically and simulate propagation errors caused by a bit insertion or bit deletion. In the simulation, we compare the effects of changing the synchronization pattern length and feedback key length. After that, we analyze the simulation results with the calculated propagation errors. finally. we evaluate the performance of the statistical cipher-feedback mode of operation and recommand the implementation considerations.

석탄화력 발전용 순환유동층 보일러 내 고온 증기부 운전의 동특성 이해와 응용

이후경(Hookyung Lee),김효준(Hyojun Kim),김영운(Youngoon Kim),이기현(Kihyun Lee) 대한기계학회 2016 대한기계학회 춘추학술대회 Vol.2016 No.12

In a thermal plant for power generation, transient behavior caused by load changes is largely controlled by a firing rate of fuel and a feeding rate of water. Different time constants in the boiler system which is composed of the complex configuration of heating surfaces lead considerable response time. The CFB boiler is one of the alternatives for environmental regulations aimed at controlling air emissions at coal-fired power plants. According to the previous presentation results associated with air/gas side in the CFB furnace, this paper reports dynamic simulation and analysis results for thermal process design of water/steam side in the back-pass part of the CFB boiler. The deviation between simulated results and design values is acceptable in engineering application. Finally, the CFB boiler module will be connected on the computational domain of our own dynamic plant simulation tool. It may provide strong support for the furnace and back-pass design in ultra-supercritical CFB boiler system ultimately.

Optical Encryption Scheme for Cipher Feedback Block Mode Using Two-step Phase-shifting Interferometry

Seok Hee Jeon,길상근 한국광학회 2021 Current Optics and Photonics Vol.5 No.2

We propose a novel optical encryption scheme for cipher-feedback-block (CFB) mode, capable of encrypting two-dimensional (2D) page data with the use of two-step phase-shifting digital interferometry utilizing orthogonal polarization, in which the CFB algorithm is modified into an optical method to enhance security. The encryption is performed in the Fourier domain to record interferograms on charge-coupled devices (CCD)s with 256 quantized gray levels. A page of plaintext is encrypted into digital interferograms of ciphertexts, which are transmitted over a digital information network and then can be decrypted by digital computation according to the given CFB algorithm. The encryption key used in the decryption procedure and the plaintext are reconstructed by dual phase-shifting interferometry, providing high security in the cryptosystem. Also, each plaintext is sequentially encrypted using different encryption keys. The random-phase mask attached to the plaintext provides resistance against possible attacks. The feasibility and reliability of the proposed CFB method are verified and analyzed with numerical simulations.

Efficiency Investigation for a Coal-Fired Circulating Fluidized Bed Boiler of Power Generation Plant

Purimpat Sujumnongtokul,Tanakit Chummontean 대한전자공학회 2009 ITC-CSCC :International Technical Conference on Ci Vol.2009 No.7

Circulating Fluidized Bed Boiler or CFB boiler was introduced to power generating industry in Thailand in the past decade. There are less than 15 stations with in the country. This present paper is aiming at an investigation of operating thermal efficiency of a CFB boiler with the capacity of 130 ton/hr of steam. The steam is produced to supply the processes within pulp and paper mill and part of the steam supplied to generate the electricity. The fuel of the boiler furnace was sub-bituminous coal. The benefit of using circulating fluidized bed technology is that the low-temperature combustion minimizes the unwanted emission such as NOx and SOx [1-5]. Two well-known methods for efficiency assessment were used for the investigation: they are the Input-Output Method and the Heat-Balance Method [6-9]. The calculations revealed that both methods agreed well to each other and the thermal efficiency was about 90.7 percents. However, the heat-balance method disclosed significant details for each type of losses namely loss due to flue gas, loss due to water from burning hydrogen in fuel, loss due to moisture in fuel. The heat-balance method also considered the credits which were taken into account during the efficiency calculations. Finally, the results showed that major thermal loss of CFB boiler was the flue gas loss at the amount of 3.5 percents.