Turndown Ratio Research Articles

HiGee Stripper-Membrane System for Decentralized Bioethanol Recovery and Purification

Economic production of bioethanol from lignocellulosic feedstock is one of the important solutions to the rising environmental concerns and depleting crude-oil reserves. However, feedstock available for bulk production of bioethanol is spread over a wide horizon and is of low-energy density, and bioethanol produced in the fermentor is dilute (∼5 wt %), which significantly increases the energy required for and cost of bioethanol production. To address these issues, the present article introduces a process-intensified technology, namely, HiGee (short for high gravity) stripper combined with a membrane (HSM) process for concentrating bioethanol. The performance of HSM is compared with one of the best energy-efficient process for bioethanol purification in the literature. Design, optimization, and technoeconomic evaluation of both the processes are performed, and the HSM process is found to be compact, require lower capital and operating costs, and have a high turndown ratio over the conventional process. The...

Combustion characteristics and thermal efficiency for premixed porous-media types of burners

This research was conducted to experimentally compare the emission characteristics and thermal efficiency of porous-media types of burners and to determine which types to use with a condensing boiler to be developed later. Three types of porous-media burners; metal fiber (MF), ceramic (CM) and stainless steel fin (SF) were used with a commercial heat exchanger and tested for various equivalence ratios and burner capacities. The MF burner had the lowest CO emissions of the three burner types, and the SF burner had the highest CO emissions. However, The MF burner had the highest NOx emission and thermal efficiency, and the SF burner had the lowest NOx emissions and thermal efficiency. In other words, the smaller the burner porosity was (porosity: SF < CM < MF), the higher the CO emission was and the lower the thermal efficiency was. Based on the thermal efficiency, turn-down ratio and NOx and CO emissions with respect to the Korean industrial standard and European norms, the most appropriate burner type for the condensing boiler is the MF burner. The optimal operating equivalence ratio was 0.80 for the range of experimental factors considered in this research.

NUMERICAL AND EXPERIMENTAL STUDY OF A NONSPRAYED POROUS BURNER FOR LIQUID KEROSENE

In this work, the concept of a nonsprayed porous burner (NSPB) of liquid kerosene is presented by numerical and experimental studies. The porous media are designed and utilized for both evaporation and combustion processes. The NSPB consists of a porous evaporator (PE) and a porous combustor (PC). The kerosene complete evaporation within the PE is self-sustained via thermal radiation from the PC. Afterward, the vaporized kerosene and preheated air are mixed in the small mixing chamber which is located between two porous media. Then, the homogeneous combustion occurs in the PC, instead of heterogeneous combustion in conventional sprayed burner. The results show that the prediction of temperature profiles has similar trends to those of experimental. The NSPB can extend the operation conditions with higher turndown ratios (6:1) and wider equivalence ratios (0.52–0.84). The NSPB is a new strategy without spray atomizer to fulfill future requirements.

Hydrodynamic characteristic of Conical Cap tray: Experimental studies on dry and total pressure drop, weeping and entrainment

This paper addresses an experimental investigation in the hydrodynamic behavior of a new type of cap trays called Conical Cap tray (ConCap tray). The hydrodynamics of the tray was investigated in a commercial scale air–water column with an internal diameter of 1.2m. The experimental liquid loads were 29.9, 44.4, 60 and 74.4(m3/h)/m of weir length and gas flow in terms of Fs in the range of 0.2–1.5m/s(kg/m3)0.5. The dry pressure drop, total pressure drop, weeping and entrainment for the ConCap tray and a valve tray were measured and compared. Correlations for pressure drop, weeping and entrainment of the ConCap tray were provided using regression analysis method. Standard deviations of correlations, R2, are quoted. The ConCap tray was compared with a bubble cap tray using correlations. The pressure drop of the ConCap tray was less than the bubble cap and close to the valve tray. The weeping rate of the ConCap tray was less than the valve tray. Its entrainment is more than the valve tray and less than the bubble cap tray. Good turndown ratio is important characteristic of the ConCap tray which is achieved without having too much pressure drop.

Experimental investigation on an entrained flow type biomass gasification system using coconut coir dust as powdery biomass feedstock

Based on an entrained flow concept, a prototype atmospheric gasification system has been designed and developed in the laboratory for gasification of powdery biomass feedstock such as rice husks, coconut coir dust, saw dust etc. The reactor was developed by adopting L/D (height to diameter) ratio of 10, residence time of about 2s and a turn down ratio (TDR) of 1.5. The experimental investigation was carried out using coconut coir dust as biomass feedstock with a mean operating feed rate of 40kg/h The effects of equivalence ratio in the range of 0.21–0.3, steam feed at a fixed flow rate of 12kg/h, preheat on reactor temperature, product gas yield and tar content were investigated. The gasifier could able to attain high temperatures in the range of 976–1100°C with gas lower heating value (LHV) and peak cold gas efficiency (CGE) of 7.86MJ/Nm3 and 87.6% respectively.

The combustion behaviour of forced-draught industrial burners when fired within the EASEE-gas range of Wobbe Index

In Europe, a common business practice for the cross-border exchange of natural gases has been formulated by EASEE-gas. The proposed range of Wobbe Index for this purpose is 48.96–56.92 MJ/Nm 3 (25 °C/0 °C, 1013.25 hPa). However, it is unclear whether the entire range of end-use equipment can accept the suggested range and still function as desired. Research is currently underway tot assess whether this range of gases can be accepted by domestic appliances. To our knowledge, there has been little systematic investigation of the acceptable range of gas quality for large-scale, forced-draught industrial burners. Although natural gas is predominantly methane with lesser amounts of higher hydrocarbons and inerts, the variation in gas composition can have significant effects on burner performance. The vast majority of forced-draught industrial burners features a flow of air independent of the gas composition, therefore the air factor is (inversely) proportional to the Wobbe Index of the gas. In this paper we present the results of experiments on a number of generic large-scale industrial burners for boilers and industrial processes in which the Wobbe Index is varied across the EASEE-gas range. The combustion effects focused mainly on flame stability (burner overheating/blow-off and vibrations) and the pollutant emissions, such as CO, NO x and unburned hydrocarbons over the desired range of turndown ratio. The experimental results showed that, for the burners studied the measured oxygen concentration was the predominant factor governing burner behaviour; between 0.5 and 7% O 2, all burners showed a stable flame while emitting less than 400 ppmv (dry, air free) CO. Outside this O 2 range, the low-NO x boiler burners, being the most sensitive, showed decreasing flame stability and increasing CO production. One burner even exhibited blow-off, causing the safety system to shut down burner operation, an undesirable event in practice. In the burners studied, the NO x emission can increase significantly with increasing Wobbe Index. Even a relatively small increase can cause the burner to exceed the locally enforced NO x limit. The visible flame length increased with increasing Wobbe Index, due to the concomitant decrease in air factor and increase in thermal input. This can lead to a higher thermal load on furnaces, which may be unacceptable in some cases. The experimental results indicate that to widen the acceptable range some form of active control is necessary for the burners for boilers. The merits of using a feed-back control system, using oxygen measurement in the flue gas, compared to a feed-forward control using the Wobbe Index of the fuel gas are discussed. In particular, aspects regarding safety in the event of sensor malfunction are seen to be important when choosing a system. In this case, the Wobbe method seems technically preferable.

Laminar flow meter with straight glass capillary

The Center for Measurement Standards (CMS) developed a laminar flow meter (LFM) as a transfer standard. This LFM consists of a single, straight glass capillary or multiple straight glass capillaries connected in parallel. Two gauges and one thermometer measure the inlet/outlet pressure and inlet temperature, respectively, and the differential pressure was restricted to between 2 kPa and 100 kPa. The glass capillaries were manufactured by laser machining, which resulting in consistent inner diameter and straight flow path. Characteristics of the glass material also prevented the capillary from bending during installation. The LFMs were calibrated against the CMS piston prover primary standard and the calibration data were fitted using a theoretical LFM model and a 2nd order polynomial. The turndown ratio of this approach was higher than 20 and the residuals were within 0.11%. The reproducibility/repeatability within 0.03% indicated that this LFM could be used as a transfer standard. Measurement with dry air demonstrated that these four LFE meters could span flows from 0.8 to 986 µmol/s within the deviation of ± 0.15% (1µmol/s is 1.3 cm3/min at 0°C and 101.325 kPa). Additional measurement with nitrogen demonstrated the feasibility of measurement with multiple gases.

핀틀 로켓의 초기 최적 노즐 팽창비 결정 방법 연구

In this study, determination method of initial optimal nozzle expansion in pintle rocket was investigated. The initial optimal initial nozzle expansion was decided by maximizing the mass-averaged thrust coefficient that is calculated from thrust coefficient of minimum and maximum chamber pressure. The determination of initial optimal initial nozzle expansion was equivalent to that of the minimum propellant mass which was required for obtaining the desired mission performance. The highest pressure, thrust turndown ratio and total impulse ratio effected on the initial optimal nozzle expansion. Among them, total impulse ratio had great influence on the initial optimal nozzle expansion.

An experimental study of a cylindrical multi-hole premixed burner for the development of a condensing gas boiler

This study experimentally examined a cylindrical multi-hole premixed burner for its potential use for a condensing gas boiler, which produces less NO x emissions and performs better. In this study, the hole diameters and the arrangement of a multi-hole burner were investigated using a flat burner model. The combustion characteristics for the flame stability as well as the NO x and CO emissions were examined using a cylindrical burner. For an optimal operating condition, the equivalence ratio for the cylindrical burner was between 0.70 and 0.75. For this condition, the turn-down ratio was 3:1 or higher, which was suitable for appropriate control of the boiler operation. The NO x and CO emissions were less than 40 ppm and less than 30 ppm, respectively, for a 0% O 2 basis. The LPG and LNG were able to be used in this type of burner because there was no phenomenal difference in the stable combustion region between them.

Design and development of a SPMB (self-aspirating, porous medium burner) with a submerged flame

This work reports design and development of a SPMB (self-aspirating porous medium burner) for replacing the self-aspirating, CB (conventional gaseous fuel, free flame burners), which are widely used in heating process of SMEs (small and medium scale enterprises) in Thailand but they have relatively low thermal efficiency of about 30 percent. Design of the SPMB relies on the same important characteristics of the CB, i.e. using the same mixing tube and the same fuel nozzle. The SPMB is formed by a packed bed of alumina spheres. The pressure drop across the packed bed, diameter of particles and a combustion chamber diameter are estimated by Ergun’s equation in combination with Pe (Peclet number). The SPMB yields a submerged flame with an intense thermal radiation emitted downstream. An output radiation efficiency as high as 23 percent can be achieved at relatively high turn-down ratio of 2.65 and firing rate ranging from 23 to 61 kW. The SPMB shows a more complete combustion with relatively low CO emission of less than 200 ppm and acceptably high NO x emission of less than 98 ppm as compared with the CB throughout the range of firing rate studied, suggesting the possibility of the SPMB in replacing the CB.

An Analysis of Flaring and Venting Activity in the Alberta Upstream Oil and Gas Industry

ABSTRACT Alberta, Canada, is an important global producer of petroleum resources. In association with this production, large amounts of gas (1.14 billion m3 in 2008) are flared or vented. Although the amount of flaring and venting has been measurably reduced since 2002, data from 2005 reveal sharp increases in venting, which have important implications in terms of resource conservation and greenhouse gas emissions (which exceeded 8 million tonnes of carbon dioxide equivalent in 2008). With use of extensive monthly production data for 18,203 active batteries spanning the years 2002–2008 obtained in close cooperation with the Alberta Energy Resources Conservation Board, a detailed analysis has been completed to examine activity patterns of flaring and venting and reasons behind these trends in the Alberta upstream oil and gas industry. In any given year, ∼6000 batteries reported flaring and/or venting, but the distribution of volumes flared and vented at individual sites was highly skewed, such that small numbers of sites handled large fractions of the total gas flaring and venting in the Province. Examination of month-to-month volume variability at individual sites, cast in terms of a nominal turndown ratio that would be required for a compressor to capture that gas and direct it into a pipeline, further revealed that volumes at a majority of sites were reasonably stable and there was no evidence that larger or more stable sites had been preferentially reduced, leaving potential barriers to future mitigation. Through linking of geospatial data with production data coupled with additional statistical analysis, the 31.2% increase in venting volumes since 2005 was revealed to be predominantly associated with increased production of heavier oils and bitumen in the Lloydminster region of the Province. Overall, the data suggest that quite significant reductions in flaring and venting could be realized by seeking mitigation solutions for only the largest batteries in the Province. IMPLICATIONS Global flaring and venting of substantial volumes of waste flammable gases is a significant environmental concern. Alberta, Canada, is an example of a jurisdiction that has achieved significant reductions in flare and vent volumes from historic highs; however, these efforts have stalled in recent years. Through unprecedented access to several years of site-by-site production data for the entire upstream oil and gas industry in this region, a detailed analysis of current practices and activity trends in flaring and venting in Alberta has been made possible for the first time. The results of this analysis, including a specific investigation of potential barriers to mitigation of flaring and venting in a mature oil- and gas-producing region, have important implications for flaring and venting mitigation throughout the world.

Theoretical and Experimental Investigations of the Plasma-Assisted Combustion and Reformation System

Theoretical and experimental investigations of the working processes in a plasma-assisted combustion and reformation system have been conducted. The selected concept can provide higher performance, wider turndown ratios, more efficient propellant utilization, demonstration of potential fuel flexibility, and satisfaction of major gravimetric and volumetric density requirements. Obtained results and recommendations can be used for hybrid-type plasma-assisted system operation modes, including modeling, geometry optimization, prospective propulsion, and power-generation unit designs and engineering.

Hydrocyclones for De-oiling Applications—A Review

The de-oiling hydrocyclone is a device for liquid–liquid separation and production water cleanup. Significant progress has been made in the development of such a device since its first introduction and use in the late 1970s. The present article is a literature review of development and research work performed so far on de-oiling hydrocyclones. It reviews the performance parameters affecting the de-oiling hydrocyclone operation; namely, the inlet oil concentration and drop size distribution, the turn-down ratio, the pressure drop ratio, the flow split, and the geometrical parameters. The article addresses work done to elucidate the internal flow structure and performance of de-oiling hydrocylones in both experimental and computational fluid dynamics areas. Challenges and remaining research issues are also identified.

Control system design and experiment of needle-type gas regulating system for ducted rocket

The control system design and experimental investigation of the gas regulating system for a ducted rocket are studied in this article. First, the dynamic model of the gas regulating system for the ducted rocket was established, and comparison of the two regulating modes regarding non-linearity and uncertainty was done. In contrast with the area-regulated mode, the non-linearity of the pressure-balanced mode is smaller and the robustness is stronger. Then, the study of the the gas control system is performed based on the model established in this article. The introduction of high-gain feedback suppresses the effects of non-linearity and uncertainty in the pneumatic servo system. Also, a proportional-integral controller for the gas regulating system based on linear matrix inequality is designed. Lastly, an experimental investigation of the gas flow control system is done to verify the validity of the gas control system. The experimental result shows that the gas flow control system has good performance. The turndown ratio of mass flow through the control valve was up to 3.7:1.

Development of an Effervescent Atomizer for Industrial Burners

The present work is conducted with the purpose of developing an effervescent atomizer for industrial burners that will generate a fine and steady spray in large turn-down ratio. The atomizer is fed with light heating oil (LHO) and uses air as an atomizing medium. First, a basic classification is made of the published design concepts of effervescent atomizers investigated by different researchers. Three distinct types of such atomizers are recognized. A single-hole, plain-orifice atomizer with an “outside-in” gas injection configuration was chosen for this study. The basic geometric parameters that may significantly influence atomizer performance are described. An experimental study of the effervescent atomizer was conducted to evaluate the influence of operational conditions and that of several geometric parameters on the drop size in the spray. The Sauter mean diameter of drops was measured using a phase/Doppler particle analyzer. The study covers the size and number of aerator holes, their location, and the diameter of the mixing chamber. The influence of these parameters on the spray quality was evaluated at atomizing pressures of 0.1, 0.3, and 0.5 MPa and gas:liquid mass flow rate ratio (GLR) values of 2%, 5%, and 10%. The main goal of this work is to develop a new procedure for the design of effervescent atomizers. This procedure is based on our experimental results and it is also supported by the findings of other authors. It allows for the determination of the key geometric parameters of the atomizer to achieve sprays of minimum mean drop size for defined values of liquid flow rate, air supply pressure, and GLR. The article also studies the optimization of the exit orifice size and of other parameters, such as the size of the mixing chamber (internal diameter and length), and the number, size, and position of aeration holes.

Butane oxidation process development in a circulating fluidized bed

DuPont designed and operated a circulating fluidized bed reactor (CFB) to produce maleic anhydride from n-butane using a vanadium pyrophosphate catalyst (VPP) encapsulated in a silica shell. A fraction of the pyrophosphate was oxidized to the V 5+ state from the V 4+ state in an air fed fluidized bed regenerator. The oxidized VPP was shuttled to a transport bed reactor with a high concentration of butane and oxygen. The gas carried the catalyst up through the bed at velocities of 0.8 m/s and, in the commercial plant, solids circulation rates exceeding 7 kt/h. Early development work was conducted on an experimental scale facility containing 1 kg of catalyst. The pilot plant catalyst inventory exceeded 2000 kg and there was 175 t in the commercial reactor. Throughout the program, significant advances in catalyst manufacture and process design were achieved. The CFB reactor configuration is being considered for several unrelated processes including chemical looping combustion, methanol-to-olefins and hot gas desulphurization. Improvements in spray drying technology reduced attrition losses by an order of magnitude versus expectation based on the pilot plant. Together with the low attrition losses and good stability, catalyst consumption was reduced by successfully re-spray drying used/attrited catalyst. By modifying the solids entrance and exit configurations, we were able to double initial plant capacity. Operability of the plant was excellent with a turn-down ratio of 5 demonstrated. At a production rate of 65,000 t/year of maleic acid – one of the largest single train reactors for a partial oxidation of an alkane – the maximum temperature difference within the bed was less than 20 °C. Heat transfer had been a major design consideration but even at this rate, only 1/3 of the total coil surface for cooling was activated.

Model of a novel pressurized solid oxide fuel cell gas turbine hybrid engine

Solid oxide fuel cell gas turbine (SOFC-GT) hybrid systems for producing electricity have received much attention due to high-predicted efficiencies, low pollution and availability of natural gas. Due to the higher value of peak power, a system able to meet fluctuating power demands while retaining high efficiencies is strongly preferable to base load operation. SOFC systems and hybrid variants designed to date have had narrow operating ranges due largely to the necessity of heat management within the fuel cell. Such systems have a single degree of freedom controlled and limited by the fuel cell. This study will introduce a new SOFC-GT hybrid configuration designed to operate over a 5:1 turndown ratio, while maintaining the SOFC stack exit temperature at a constant 1000 °C. The proposed system introduces two new degrees of freedom through the use of a variable-geometry nozzle turbine to directly influence system airflow, and an auxiliary combustor to control the thermal and power needs of the turbomachinery.

핀틀 노즐형 로켓 모타의 추력 조절 성능에 관한 연구

Theoretical thrust equations for the diverse nozzle expansion condition were derived. By using the obtained thrust equations, parametric studies were carried out to estimate the effect of pressure exponent, minimum operation pressure, ambient pressure and extinguishment pressure on thrust modulation performance in pintle-nozzle solid rocket motors. Analysis results showed that thrust turndown ratio can be easily attained by small nozzle-throat area variation at high pressure exponent, low minimum operation pressure, high ambient pressure and high extinguishment pressure condition. At those conditions, the highest chamber pressure to obtain the intended thrust turndown ratio can be minimized.

Droplet size and spray pattern characteristics of PWM-based continuously variable spray

A Pulse-Width-Modulation-based (PWM-based) continuously variable sprayer was developed using a proportional regulating solenoid valve. Variable flow-rate was obtained by varying the duty cycle of the actuating signal with 24 kHz frequency. Flow-rate regulating ranges of the PWM-based continuously variable spray (i.e. the turndown ratio responding to 100%-40% duty cycle) are 7.14:1, 3.57:1, and 3.70:1 for flat-fan, hollow-cone and solid-cone nozzles, respectively. The purpose of the study was to evaluate the PWM-based continuously variable spray. The method was to quantify the effects of flow-rate control on spray characteristics in terms of droplet size spectra, spray distribution patterns, and spray angle for flat-fan, hollow-cone, solid-cone nozzles. For all nozzles tested, spray distribution concentrated on the center of the spray field with the decrease of flow-rate. But the spray shape is still symmetrical. The sensitivities of the spray angles to flow-rate were 0.83, 0.67, and 0.58 (o)/% respectively for flat-fan, hollow-cone and solid-cone nozzles. Compared with the sensitivities of spray angle for PWM-based intermittent variable spray, they are somewhat larger. As flow-rate was reduced from the maximum (100% flow-rate) to the minimum controllable rate, the observed median diameter of spray droplets decreased by 5.4%, 9.8%, and 9.9 % for flat-fan, hollow-cone and solid-cone nozzles, respectively. This indicates that spray droplet size was affected slightly by flow-rate control. Keywords: Pulse Width Modulation (PWM), continuously variable spray, droplet size, spray distribution pattern, spray angle DOI: 10.3965/j.issn.1934-6344.2009.01.008-018 Citation: Deng Wei, He Xiongkui, Ding Weimin. Droplet size and spray pattern characteristics of PWM-based continuously variable spray. Int J Agric & Biol Eng, 2009; 2(1): 8

Applied digital signal processing systems for vortex flowmeter with digital signal processing

The spectral analysis is combined with digital filter to process the vortex sensor signal for reducing the effect of disturbance at low frequency from pipe vibrations and increasing the turndown ratio. Using digital signal processing chip, two kinds of digital signal processing systems are developed to implement these algorithms. One is an integrative system, and the other is a separated system. A limiting amplifier is designed in the input analog condition circuit to adapt large amplitude variation of sensor signal. Some technique measures are taken to improve the accuracy of the output pulse, speed up the response time of the meter, and reduce the fluctuation of the output signal. The experimental results demonstrate the validity of the digital signal processing systems.