Search

This study aims to optimize the oxy-circulating fluidized bed combustion (oxy-CFBC) process by reducing the amount of flue gas with high-purity carbon dioxide. To achieve this, the stable transition from air mode to oxy mode is tested and validated in a 0.1-MW oxy-CFBC test rig. The results prove that flue gas carbon dioxide separation can achieve 96 vol% (dry) through a stable transition from air mode to oxy mode. Moreover, flue gas production emitted in oxy mode is reduced to one fifth compared to air mode. The proven technologies and oxy-fuel combustion database from this test rig operating experience can be used as empirical operating parameters for the next steps such as demonstration and commercial-scale operation.

To improve the fluidity of a coal water mixture (CWM) having lower viscosity and higher solid concentration, the effects of surfactants (five kinds) and experimental variables such as temperature (5-65 °C), pH (1-11), particle size distribution (PSD) on the viscosity characteristics of two different coals (Shenhua and Kideco Coal) were investigated. Relatively economical surfactants were chosen in this study: sulfonated melamine formaldehyde polymer (SMF-30), naphthalene formaldehyde sulfonate (Sikament-NN), naphthalene sulfonate water reducer (NSWR), naphthalene formaldehyde sulfonate (PC-1000) and poly-carboxylate (PC). The SMF-30, an anionic surfactant, revealed the most significant reduction in viscosity of CWM among the five surfactants since the SMF-30 forms electric double layer on the surface of coal, and the repulsive force of this layer surpasses the aggregation of coal particles. In addition, the viscosity of CWM decreased with increasing pH and temperature, in particular, the increase in OH- on the surface of coals by the addition of NaOH caused the increase in the repulsive force between the negatively charged coal particles. Furthermore, the very fine particles (less than 45 μm) of coals should be removed before making CWMs since it revealed the increase in viscosity of CWMs.

Carbonization is a low-temperature thermochemical process that converts organic matter in the absence of oxygen mainly into char, gas, and liquids. Bio-coke is a char prepared from a mixture of biomass/charcoal and a coal blend. It can reduce greenhouse gas emissions by replacing coke and reducing coal consumption in the ironmaking process. In this study, the carbonization characteristics such as char conversion, gas and tar composition of bio-coke were determined using a batch-type carbonization reactor. Yellow poplar wood used as a biomass was added to a coking coal in different ratios (0, 10, 15, 20, and 30 wt%) and the resulting raw bio-coke was carbonized at different final temperatures (500–800 °C). The calorific value of bio-coke was higher than 7000 kcal/kg, exceeding the standard value. Moreover, the initiation combustion temperature of the resultant bio-coke determined using TGA was in the range of 400–600 °C. It is concluded that bio-coke is a suitable substitute for conventional fossil fuels reducing CO2 emissions.

Implementation of circulating fluidized bed (CFB) boilers in the energy sector has witnessed a steady increase owing to their afforded advantages of operational flexibility in terms of compliance with several low-grade fuels and in-situ DeSOx and DeNOx capabilities. In recent years, the rise in global warming and development of intermittent power-generation technologies have stressed the need for development of techniques to afford high-efficiency low-emission (HELE) power-generation, effective carbon capture and storage, and flexible operation of thermal power plants. To meet these demands, the Future Energy Plant Convergence Research Center (FEP CRC) has investigated oxy-combustion technologies for CFB boilers that use low-grade fuels with calorific values

Oxy-combustion with a circulating fluidized bed (Oxy-CFBC) can facilitate the separation of high CO2 concentration and reduce emissions by biomass co-firing. This study investigated Oxy-CFBC characteristics such as temperature, solid hold-up, flue gas concentrations including CO2, pollutant emissions (SO2, NO, and CO), combustion efficiency and ash properties (slagging, fouling index) with increasing input oxygen levels (21–29 vol%), and biomass co-firing ratios (50, 70, and 100 wt% with domestic wood pellet). The possibility of bio-energy carbon capture and storage for negative CO2 emission was also evaluated using a 0.1 MWth Oxy-CFBC test-rig. The results show that combustion stably achieved with at least 90 vol% CO2 in the flue gas. Compared to air-firing, oxy-firing (with 24 vol% oxygen) reduced pollutant emissions to 29.4% NO, 31.9% SO2 and 18.5% CO. Increasing the biomass co-firing from 50 to 100 wt% decreased the NO, SO2 and CO content from 19.2 mg/MJ to 16.1 mg/MJ, 92.8 mg/MJ to 25.0 mg/MJ, and 7.5 mg/MJ to 5.5 mg/MJ, respectively. In contrast to blends of sub-bituminous coal and lignite, negative CO2 emission (approximately −647 g/kWth) was predicted for oxy-combustion only biomass.

The adoption of oxy-combustion in a circulating fluidized bed (CFB) producing ultra-supercritical (USC) steam has been investigated to increase energy efficiency and reduce CO2 emissions of coal-fired power plants. This paper presents a techno-economic analysis for 500 MWe USC-CFB power plants with air- and oxy-combustion in the presence of CO2 capture. An amine absorber unit (AAU) and a CO2 processing unit (CPU) were used to capture CO2 in the air- and oxy-combustion power plants, respectively. The air-combustion power plant without CO2 capture (Case 1) showed the highest net electricity efficiency (46%), whereas the introduction of an AAU in the air-combustion power plant (Case 2) reduced the net efficiency to 36%. The net efficiency (39%) of the oxy-combustion power plant with CPU (Case 3) was higher than that of Case 2 owing to the recycling of hot flue gas. The levelized cost of electricity (LCOE) of Case 3 (59 $/MWh) was lower than that of Case 2 (64 $/MWh), which demonstrated that oxy-combustion was advantageous compared to air-combustion in a scenario with CO2 capture. The sensitivity analyses of the electricity price and CO2 credit showed economic situations where Cases 2 and 3 would be profitable.

Considering the importance of the detailed resolution of the reacting flow field inside a gasifier, the objective of this study lies on to investigate the effect of important variables to influence on the reacting flow and thereby to clarify the physical feature occurring inside the gasifier using a comprehensive gasifier computer program. Thus, in this study the gasification process of a 1.0 ton/day gasifier are numerically modeled using the Fluent code. And parametric investigation has been made in terms of swirl intensity and aspect ratio of the gasifier. Doing this, special attention is given on the detailed change of the reacting flow field inside a gasifier especially with the change of this kind of design and operation parameters. Based on this study, a number of useful conclusions can be drawn in the view of flow pattern inside gasifier together with the consequence of the gasification process caused by the change of the flow pattern. Especially, swirl effect gives rise to a feature of a central delayed recirculation zone, which is different from the typical strong central recirculation appeared near the inlet nozzle. The delayed feature of central recirculation appearance could be explained by the increased axial momentum due to the substantial amount of the presence of the coal slurry occupying over the entire gasifier in gasification process. Further, the changes of flow pattern are explained in detail with the gasifier aspect ratio. In general, the results obtained are physically acceptable in parametric study.

A wire mesh reactor was used to investigate the devolatilization process of coal particle during entrained flow gasification. Coal from Indonesia East Kalimantan mine, which has high moisture and high volatile matter, was chosen as a sample. Experiments were carried out at the heating rate of 1,000 °C/s and isothermal condition was kept at peak temperature under atmospheric pressure. The char, tar and gas formation characteristics of the coal as well as the composition of the gas components at peak temperatures were determined. The experimental results showed that devolatilization process terminated when temperature reached above 1,100 °C. Most of tar was formed at about 800 °C, while the rate of tar formation decreased gradually as the temperature increased. CH4 was observed at temperatures above 600 °C, whereas H2 was detected above 1,000 °C. The amount of formed gases such as H2, CO, CH4 and C n H m increased as the temperature increased. From the characteristics of devolatilization with residence time, it was concluded that devolatilization terminated within about 0.7 second when the temperature reached 1,000 °C. As the operating temperature in an entrained flow gasifier is higher than ash melting temperature, it is expected that the devolatilization time of high volatile coal should be less than one second in an entrained flow gasifier.

To investigate the kinetic characteristics of coking coal mixed with biomass during pyrolysis, thermogravimetric (TG) and thermo-balance reactor (TBR) analyses were conducted under non-isothermal and isothermal condition. Yellow poplar as a biomass (B) was mixed with weak coking coal (WC) and hard coking coal (HC), respectively. The calculated activation energies of WC/B blends were higher than those of HC/B blends under non-isothermal and isothermal conditions. The coal/biomass blends show increased reactivity and decreased activation energy with increasing biomass blend ratio, regardless of the coking properties of the coal. The different char structures of the WC/B and HC/B blends were analyzed by BET and SEM.

>> Study on clean and efficient utilization technology for low rank coal with high moisture content is actively ongoing due to limited reserves of petroleum and of high grade coal and serious climate change causedby fossil fuel usage. In the present study, supercritical water gasification of low rank coal was performed. Withincreasing reaction temperature, content of combustible gases such as H 2 and CH 4 in the syngas increased while the CO 2 content decreased. As the reaction pressure increased from 210 to 300 bar, the CO 2 content in the syngasincreased while the hydrocarbon gas content decreased. The H 2 and CH 4 content in the syngas increased slightlywith pressure. With the addition of Pd, Pt, and Ru catalysts, it was possible to improve the production of H 2 .Moreover, the increase of active metal content in the catalyst increased the H 2 productivity. The Ru catalyst showsthe best performance for increasing the H 2 content in the syngas, while decreasing the CO 2

In the present study, microwave plasma gasification of two kinds of coal and one kind of charcoal was performed with various O2/fuel ratios of 0e0.544. Plasma-forming gases used under 5 kW microwave plasma power were steam and air. The changes in the syngas composition and gasification efficiency in relation to the location of the coal supply to the reactor were also compared. As the O2/fuel ratio was increased, the H2 and CH4 contents in the syngas decreased, and CO and CO2 increased. When steam plasma was used to gasify the fuel with the O2/fuel ratio being zero, it was possible to produce syngas with a high content of hydrogen in excess of 60% with an H2/CO ratio greater than 3. Depending on the O2/fuel ratio, the composition of the syngas varied widely, and the H2/CO ratio necessary for using the syngas to produce synthetic fuel could be adjusted by changing the O2/fuel ratio alone. Carbon conversion increased as the O2/fuel ratio was increased, and cold gas efficiency was maximized when the O2/fuel ratio was 0.272. Charcoal with high carbon and fixed carbon content had a lower carbon conversion and cold gas efficiency than the coals used in this study.

Plasma gasification is widely applied because of its clean syngas production performance and high chemical reactivity accelerated by the free radicals produced by plasma. In the present study, the plasma gasification of four kinds of coal with various conditions of O2/fuel ratio, steam/fuel ratio, and coal particle sizes was performed by using a 2 kW microwave plasma unit. Nitrogen was used as a plasma forming gas. Gasification was conducted with an O2/fuel ratio of 0–1.3, a steam/fuel ratio of 0–1.5, and a coal particle size of 45–150 μm. With an increasing O2/fuel ratio, the H2 composition in the syngas decreased while the CO2 content increased. The CO composition increased until reaching an O2/fuel ratio of approximately 0.6, depending on the coal type, and decreased thereafter. CH4 was not observed in a syngas, which is typical of high temperature plasma gasification. The H2 and CO2 contents tend to increase, and the CO content in the product gas decreased with increasing steam/fuel ratio. The syngas ...

Wallboards with micro encapsulated phase changing material (micro PCM) were used to investigate the performance and the energy saving characteristics as building materials in winter and summer climate conditions. The test house consisted of a boiler with under floor heating system, an air conditioner, micro PCM wallboard room and conventional wallboard room. The outer temperature of the rooms could be artificially controlled at the temperature range of −12 to 35 °C. Micro PCM content in wallboards was 0–4 kg/m2. The melting temperature and latent heat of Micro PCM are 23 °C and 211 J/g. Also, micro PCM shows stable mechanical strength under 500 psi. As micro PCM content increased, the temperature fluctuations decreased. In case of micro PCM wallboard, temperature profiles in the room show stable and comfortable ranges. The optimum amount of micro PCM in wallboard to maximize energy saving efficiency was around 3 kg/m2.

To enhance clean energy utilization and reduce greenhouse gases, various gasification technologies have been developed in the world. The gasification characteristics, such as syngas flow rate, compositions, cold gas efficiency and carbon conversion, of petroleum coke and mixture of petroleum coke and lignite were investigated in a 1 T/d entrained-flow gasifier (I.D. 0.2 m × height 1.7 m) with quencher as a syngas cooler. CO concentration was 31–42 vol% and H 2 concentration was almost 22 vol% in the gasification experiments of petroleum coke. In the case of mixture of petroleum coke and lignite, CO concentration was 37–47 vol% and H 2 concentration was almost 25 vol% due to synergy effect. The gasification of mixture resulted in higher syngas heating value and cold gas efficiency because of the higher H 2 and CO composition in syngas.

Pyrolysis characteristics of the sub-bituminous coal, Refuse Derived Fuel (RDF) and their blends were determined at non-isothermal (15 ◦C/min) and isothermal (500–800 ◦C) conditions in thermogravimetric analyzer (TGA) and a thermobalance reactor. The decomposition rates of coal and RDF blends are higher than the calculated values of each fuel at the lower temperature ranges (300–385 ◦ C). In the isothermal condition, activation energies of coal and RDF blends are lower and the pyrolysis reactivity is higher than the calculated values of each fuel. The synergistic effect exhibits remarkably with the RDF blend ratio of 50% at 700 ◦C. The structural variation and inorganic matters of chars from coal and RDF were determined by using BET, SEM, and XRD techniques. Surface area of the blend char increases and the average pore size decreases with pyrolysis. The addition of RDF into coal produces sulfur fixation of CaS and CaSO3 based on the XRD data.

As a preliminary study for the gasification of an anthracite and petroleum coke mixture, viscosity was measured at various temperatures (20-50 o C), slurry concentrations (60-70 wt%) and additive amounts (0-0.8 wt%) by using an LV-II type viscometer. In addition, four types of different additives, sodium naphthalene sulfonate, poly(methyl methacrylate), polypropylene and a polypropylene glycol based additive, were applied to Korean anthracite, petroleum coke and mixtures of these materials, and the viscosity data were compared. Viscosity dependency values for coal, anthracite, bituminous and sub-bituminous coal, were compared, and it was found that a high content of moisture and particularly ash increases CWS viscosity. The four types of additives tested in this research can effectively diminish the viscosity of coal and especially petroleum coke-water slurry by more than 70% to 95%, respectively. Moreover, the sodium naphthalene sulfonate-based additive reduced the viscosity of coal and petroleum coke-water slurry best, especially at concentrations in excess of 65 wt%. Based on these results, highly loaded slurry created by mixing anthracite and petroleum coke with additives was achieved.

This paper presents novel low-cost CMOS temperature sensor for controlling the self-refresh period of a mobile DRAM. In the proposed temperature sensor, the temperature dependency of poly resistance is used to generate a temperature-dependent bias current, and a ring oscillator driven by this bias current is employed to obtain the digital code pertaining to on-chip temperature. This method is highly area-efficient, simple and easy for IC implementation as compared to traditional temperature sensors based on bandgap reference. The proposed CMOS temperature sensor was fabricated with an 80nm 3-metal DRAM process, which occupies extremely small silicon area of only about 0.016mm^2 with under 1@mW power consumption for providing 0.7^oC effective resolution at 1 sample/s processing rate. This result indicates that as much as 73% area reduction was obtained with improved resolution as compared to the conventional temperature sensor in mobile DRAM.

As a preliminary study of gasification of coal and petroleum coke mixtures, thermogravimetric analyses were performed at various temperatures (1,100, 1,200, 1,300, and 1,400 °C) and the isothermal kinetics were analyzed and compared. The activation energies of coal, petroleum coke and coal/petroleum coke mixture were calculated by using both a shrinking core model and a modified volumetric model. The results showed that the activation energies for the anthracite and petroleum coke used in this study were 9.56 and 11.92 kcal/mol and reaction times were 15.8 and 27.0 min. In the case of mixed fuel, however, the activation energy (6.97 kcal/mol) and reaction time (17.0 min) were lower than the average value of the individual fuels, confirming that a synergistic effect was observed in the coprocessing of coal and petroleum coke.

High temperature air-blown gasification is a new concept to utilize the waste heat from gasifier that is called multi-staged enthalpy extraction technology. This process was developed to solve the economic problems due to air separation costs for the oxygen-blown as a gasifying agent. In this study, we have constructed a pebble bed gasifier and operated it by controlling the pebble size and bed height with three different types of coal (Kideco, Datong and Drayton coal). As a result, we can produce syngas with a calorific value of 700 kcal/Nm3 at an air temperature of 650 °C; the performance of high temperature air gasification was strong in the order of Kideco coal, Datong coal and Drayton coal. Also, from the data of the exterior analysis of slag that is attached to the surface of pebbles, we can know that the iron component is considerably high. This means the increase in restored metallic iron component seems to contribute to the solidification of slag.

The characteristics of hydrogasification to generate substitute natural gas (SNG) by using various bituminous coals such as Alaska, Cyprus, Curragh, and Datong have been determined in an entrained-flow hydrogasifier (0.025 m I.D.×1 m high) with high pressure coal feeder and data acquisition system. The effects of reaction pressure (60–80 atm), reaction temperature (600–800 °C) and H2/coal ratio (0.3–0.5) on composition of product gas and carbon conversion have been determined. The concentration of SNG and carbon conversion increased with an increasing of reaction pressure and temperature, but the carbon conversion and concentration of each bituminous coal were quite different because of different coal properties. Also the H2/coal ratio affected the carbon conversion and the concentration of SNG.

A numerical and experimental study has been made in order to figure out the combustion characteristics of Orimulsion fuel for the possible substitution of traditional fuels in existing boilers. To this end, a comprehensive computer model has been developed using Patankar’s SIMPLE algorithm for the complex process associated with the turbulent reaction of this fuel. The program includes several phenomenological models such as behavior of fuel droplet, multi-phase reaction and formation of pollutant species such as NO and SO 2 in radiation-participating, turbulent flows. The calculation results of species and temperature profiles have been successfully compared with the experimental data measured in a small-scale combustor. Comparing the combustion characteristics of Orimulsion with that of heavy fuel oil, one of the noticeable features of Orimulsion combustion is relatively low flame temperature together with the delayed appearance of the peak flame. This is considered to be attributed to the effect of moisture content and the increased flow rate of Orimulsion fuel on the basis of an equivalent calorific value. Further this feature of Orimulsion flame observed in calculation and experiment are consistent with other experimental findings reported in open literature. It is found that the flame characteristics of Orimulsion fuel can be changed to some extent by the variation of operation conditions such as the injection velocity of Orimulsion fuel and the swirl strength of air stream. Further, other parametric study has been made in terms of the type of atomizing fluid, equivalence ratio, radiation model and grid size. In general the results are physically acceptable and consistent. Therefore the computer program developed is considered as a viable tool for the advanced design and determination of optimal operating condition for the large scale of Orimulsion combustor.

With increasing environmental considerations and stricter regulations, gasification of waste is considered to be a more attractive technology than conventional incineration for energy recovery as well as material recycling. The experiment for combustible waste mixed with plastic and cellulosic materials was performed in a fixed-bed gasifier to investigate the gasification behaviour with the operating conditions. Waste pelletized to a diameter of 2–3 cm and 5 cm length, was gasified in the temperature range 1100–1450 °C. The composition of H2 was in the range 30–40% and CO 15–30% depending upon the oxygen/waste ratio. Gasification of waste due to the thermoplastic property of the mixed-plastic melting and thermal cracking shows a prominent difference from that of coal or coke. It was desirable to maintain the top temperature at 400 °C to ensure the mass transfer and uniform reaction throughout the packed bed. As the bed height was increased, the formation of H2 and CO was increased, whilst the CO2 decreased by the char-CO2 reaction and plastic cracking. From the experimental results, the cold gas efficiency was around 61% and the heating values of product the gases were in the range of 2800–3200 kcal/Nm3.

The coal gasification process of a slurry feed type, entrained-flow coal gasifier was numerically predicted in this paper. By dividing the complicated coal gasification process into several simplified stages such as slurry evaporation, coal devolatilization and two-phase reactions coupled with turbulent flow and two-phase heat transfer, a comprehensive numerical model was constructed to simulate the coal gasification process. The k–e turbulence model was used for the gas phase flow while the Random-Trajectory model was applied to describe the behavior of the coal slurry particles. The unreacted-core shrinking model and modified Eddy break-up (EBU) model, were used to simulate the heterogeneous and homogeneous reactions, respectively. The simulation results obtained the detailed information about the flow field, temperature and species concentration distributions inside the gasifier. Meanwhile, the simulation results were compared with the experimental data as a function of O2/coal ratio. It illustrated that the calculated carbon conversions agreed with the measured ones and that the measured quality of the syngas was better than the calculated one when the O2/coal ratio increases. This result was related with the total heat loss through the gasifier and uncertain kinetics for the heterogeneous reactions.

Experimental Studies of a 1 Ton/Day coal slurry feed type oxygen blown, entrained flow gasifier have been performed with the slurry concentration and gasifier temperature at 65% and above 1,300 ‡C, respectively. The characteristics of ash fusion temperature with addition of CaO as a flux were investigated to maintain the proper slag tapping condition in the range of reaction temperature. As the flux addition increased, ash fusion temperature showed a eutectic effect with the eutectic at around 20–30% CaO. In order to analyze the gasification characteristics, the effects of O2/coal feed ratio on the product gas composition, heating value, gasifier temperature and cold gas efficiency were evaluated. From the results, it was shown in the case of Kideco coal that the cold gas efficiency was 44–60% and the heating value was 1,700-2,200 kcal/Nm3, while Drayton coal showed a cold gas efficiency of 55–62% and a heating value of 1,800-2,200 kcal/Nm3. In the case of Datong coal, the cold gas efficiency was 38–65%, and the heating value was 2,000-2,300 kcal/Nm3. Also, the results showed that the optimal operating condition of O2/coal ratio for the three different coals was 0.9.

The effects of reaction temperature, oxygen/coal and steam/coal ratios and residence time on coal gasification performance in entrained flow were determined by means of a drop tube reactor (0.05 m.i.d. × 1.0 m high). The H 2 CO molar ratio decreases with increasing reaction temperature and the H2 + CO content of the product gas exhibit a maximum around the ash fusion temperature. With increasing O2 content, carbon conversion increases and the rate of production of H2 and CO increases initially to a maximum value. The optimum O 2 coal ratio is in the range 0.6-0.9 for different coals.

Coal is relative cheaper than petroleum, widely distributed across the globe, and abounds in reserves. Moreover, strict clean air policies and CO2 emission regulation lead increased interest and researches in the clean utilization of coal. Coal gasification is recognized as a one of the clean coal technology that has come into the spotlight for its environment-friendliness and better efficiency than conventional generation system [Minchener, 2005; Higman et al., 2008]. During coal gasification, sulfur compound in coal is converted to gaseous phase of H2S. The H2S in a syngas generated from the coal gasifier must be removed before the engine or turbine because it leads the corrosion and erosion of the system and eliminated to clean use of syngas as a feedstock of chemicals.

Line inversion-based mobile TFT-LCD driver IC with novel quadruple-gamma-curve correction is presented. The driver IC allows for a cost-effective accurate curve correction for multiple gamma values of γ1.0, γ1.8, γ2.2, and γ2.5 by adopting novel voltage-symmetric gray curve synthesis and variable reference resistor-tap biasing schemes. A test chip in a 6 V/0.7-μm triple-well CMOS process indicated a gray voltage error of ±8 mV with gray-to-gray error difference under ±3 mV.

This paper analyzes and compares the penal power consumption for mobile TFT-LCDs. Three representative penal driving schemes (the basic data driving, the charge-recycling data driving, and the stepwise data driving) based on the line inversion driving method are considered in this analysis, and equations for representing the penal power consumption of respective driving schemes are derived. This is the first to analyze the panel power consumption of line inversion-based mobile TFT-LCDs including parasitic capacitance effect. The analysis procedure presented here is helpful for power study, and gives benefits of providing accurate estimation of the total power consumption of mobile TFT-LCDs driven a line inversion driving.

Co-pyrolysis characteristics of sawdust and coal blend were determined in TGA and a fixed bed reactor. The yield and conversion of co-pyrolysis of sawdust and coal blend based on volatile matters are higher than those of the sum of sawdust and coal individually. Form TGA experiments, weight loss rate of sawdust and coal blend increases above 400 degrees C and additional weight loss was observed at 700 degrees C. In a fixed bed at isothermal condition, the synergy to produce more volatiles is appeared at 500-700 degrees C, and the maximum synergy exhibits with a sawdust blending ratio of 0.6 at 600 degrees C. The gas product yields remarkably increase at lower temperature range by reducing tar yield. The CO yield increases up to 26% at 400 degrees C and CH(4) yield increases up to 62% at 600 degrees C compared with the calculated value from the additive model.

A circuit technique to detect unexpected power condition such as battery separation is presented. Abrupt power-off due to this unexpected power condition may cause an abnormal display in mobile TFT-LCD because adequate power-off sequence cannot be performed. To demonstrate feasibility of the APD, test chip was designed and fabricated in a 30-V/4-um 5-V/0.8-um 2.5-V/0.25-um triple-well CMOS process. Experimental results show that the proposed APD improves display quality by allowing a proper power-off sequence at all abrupt power-off conditions.

An opportunistic source line driving (OSLD) scheme is proposed for use in mobile TFT_LCD driver ICs (T-LDIs). In OSLD scheme, the operation of the source drivers of a T-LDI is controlled by the equivalence of RGB color data for adjacent pixels. That is, one source driver drives the neighboring source lines as well as the corresponding one when the color data of adjacent pixcels are identical to each other. With this scheme, all the source drivers associated with the neighboring source lines can be completely turned off, allowing the reduction of static and dynamic current of these drivers. Test chip was fabricated in a 5-V/0.8-um 2.5V/0.25-um triple-metal CMOS process, and the experimental result shows that the power reduction of 12% ~ 21% was obtained with die size overhead less than 0.5%.

90 nm DRAM technology and beyond requires the robust memory cell capacitor structure in order to increase cell capacitance for high performance and low power applications. Thus, the cell technology must have the feature of high capacitance of memory cell capacitor while maintaining its mechanical stability. To accomplish these purposes, we develop the multi-stack storage node structure whose enlarged bottom size of OCS(One Cylindrical Storage node) can give much better mechanical stability of the capacitor than that of the conventional capacitor. Using Al/sub 2/O/sub 3//HfO/sub 2/ dielectric material together with this structure can give high cell capacitance 30fF/cell and low leakage current less than 1fA/cell.

A novel dual CSL column redundancy scheme (DCCR) that can improve effectiveness of repair and minimize overhead of die area is proposed. DCCR can repair failure bits of self-half I/O block by the unit of single bit, not by CSL. DCCR can also improve the data access speed by reducing the local I/O loading.

A novel data serializer is proposed for use in mobile TFT-LCD driver ICs. The proposed data serializer adopting hierarchical switching and repeater/separator schemes provides 82% power reduction and 27% speed improvement with 27% area saving. Measured overall power consumption of a TFT-LCD driver IC with the proposed data serializer was reduced by as much as 49%.

A circuit technique to detect unexpected power conditions such as battery separation is presented. Abrupt power-off owing to unexpected power conditions may cause an abnormal display in mobile TFT-LCDs because an adequate power-off sequence cannot be performed. The proposed abrupt power-off detector (APD) recognises decay of supply voltage and generates a signal to perform a proper power-off sequence. As mobile TFT-LCD driver ICs are usually operated with dual power supply, the APD detects abrupt power-off for both of the power supplies. To demonstrate the feasibility of the APD, a test chip was designed and fabricated in a 30 V/4 µm 5 V/0.8 µm 2.5 V/0.25 µm triple-well CMOS process. Experimental results show that the proposed APD improves display quality by allowing a proper power-off sequence at all abrupt power-off conditions.

A novel source driving scheme called opportunistic multichannel driving (OMCD) is proposed for use in mobile TFT-LCD driver ICs (T-LDIs). In the OMCD scheme, the operation of the source drivers of a T-LDI is controlled by the equivalence of RGB colour data for adjacent pixels. That is, one source driver drives the neighbouring source lines as well as the corresponding one when the colour data of adjacent pixcels are identical to each other. With this scheme, all the source drivers associated with the neighbouring source lines can be completely turned off, allowing the reduction of static and dynamic current of these drivers. A test chip was fabricated in a 5 V/0.8 /spl mu/m 2.5 V/0.25 /spl mu/m triple-metal CMOS process, and the experimental result shows that the power reduction of 12-21% was obtained with die size overhead less than 0.5%.

An analogue synchronous mirror delay with duty cycle-correction scheme (ASMDCC), to improve the data transmission performance between DRAM and system, is proposed. The ASMDCC achieves duty cycle correction and clock synchronisation at once within two clock cycles, by using a half value current source. The simulation results show the duty cycle of the internal clock is stabilised with less than /spl plusmn/100 ps deviation from 50% for the wide duty cycle range.