Continuous Steam Research Articles

Absorber Layer Addition and Thermal Storage Media Comparison for Concentrated Solar Power Plant Optimization

Electricity generation from concentrated solar power plant can be optimized on its storage system or its receiver system. This paper conducts a review of how to optimize the concentrated solar power plant by increasing the stored energy capacity or by stabilizing the absorptance and emittance in the solar absorber. The additional stages in the CSP may increase thermal efficiency. The stages consist of two oriented solar absorber to create superheated steam fed to the steam turbine and one regenerator to optimally regenerate heat for working fluid before pumped to solar absorber. A suitable treatment for superheated steam from solar absorber can optimally supply the turbine with a continually stable steam. The continuous stable steam can be controlled using steam accumulator right before the superheated steam fed into turbine. The thermal energy storage in the cycle can be optimally selected based on the stored energy capacity per kg of compared material used. The final modification was made using recently developed absorber material of hafnium molybdenum nitride to create four layer tandem absorber of HfMoN(H)/HfMoN(L)/HfON/Al2O3. The tandem absorber indicates a stable absorptance and emittance up until 600°C (in vacuum) and 525°C (in air). The final configuration believed to enhance the thermal stability for high temperature concentrated solar power plant application.

Experimental and Analytical Study of a Simulated Collapsed PHWR Reactor Channel Under Accident Condition

Heat transfer study has been carried out to characterize the effect of submergence on the heatup behavior of a collapsed PHWR reactor channel. The situation is simulated with a heat generating body enclosed in a both side open ended tube, undergoing a pool boiling condition. Under this study, the heat generating cylindrical body is rested inside the tube thus making the flow path no-uniform over the heat generating body. Experimentations are carried out at 6 and 8 kW power levels with variation of submergence level of the heater body, which ranges from 100%-12%. It is observed that for fully submerged level (100%) to a partially submerged level of 24%, a counter current stratified flow of steam and water is set up in the annulus fow path. Steam leaves from the upper section of the annulus and the pool water enter from the bottom section, thus a continuous steam generation and circulation is maintained. The convective heat removal by the steam is found to be sufficiently high to avoid dryout in the largely steam voided upper section of the heated body. However, at very low submergence level (12%) steam generation is found to be insufficeint, thus leading to a temperature excursion. The estimated generated steam mass flow rate has been found to vary between 3.55 –0.26 gm/s depending on the submergence level and power. The convective heat transfer coefficients for the exposed and submerged section of the heater body are estimated and found to vary between 0.7 kW/m2 K to 15.5 kW/m2 K. Heat transfer coefficients

Improvements in Technology for Parboiling Rice

Parboiled rice is the form predominantly used in South Asia and to lesser extents elsewhere. Technologies for parboiling, which are somewhat primitive in South Asia and highly sophisticated in the United States and Europe, are well established. Three important gaps in existing technologies are addressed in this article. First, a simple system for continuous steaming of soaked paddy (rough rice) has been developed that can be adopted not only by simple, traditional rice mills, but by modern ones as well. Second, a pretreatment for paddy has been developed as part of the process to minimize the influence of differences in the age of raw paddy material on product quality. Third, a technique has been incorporated into the soaking system to reduce microbial fermentation, even with soaking at relatively low temperatures.

Pilot-scale study on the acid-catalyzed steam explosion of rice straw using a continuous pretreatment system

A continuous acid-catalyzed steam explosion pretreatment process and system to produce cellulosic ethanol was developed at the pilot-scale. The effects of the following parameters on the pretreatment efficiency of rice straw feedstocks were investigated: the acid concentration, the reaction temperature, the residence time, the feedstock size, the explosion pressure and the screw speed. The optimal presteaming horizontal reactor conditions for the pretreatment process are as follows: 1.7rpm and 100–110°C with an acid concentration of 1.3% (w/w). An acid-catalyzed steam explosion is then performed in the vertical reactor at 185°C for 2min. Approximately 73% of the total saccharification yield was obtained after the rice straw was pretreated under optimal conditions and subsequent enzymatic hydrolysis at a combined severity factor of 0.4–0.7. Moreover, good long-term stability and durability of the pretreatment system under continuous operation was observed.

Evolution of Seismic Velocities in Heavy Oil Sand Reservoirs during Thermal Recovery Process

In thermally enhanced recovery processes like cyclic steam stimulation (CSS) or steam assisted gravity drainage (SAGD), continuous steam injection entails changes in pore fluid, pore pressure and temperature in the rock reservoir, that are most often unconsolidated or weakly consolidated sandstones. This in turn increases or decreases the effective stresses and changes the elastic properties of the rocks. Thermally enhanced recovery processes give rise to complex couplings. Numerical simulations have been carried out on a case study so as to provide an estimation of the evolution of pressure, temperature, pore fluid saturation, stress and strain in any zone located around the injector and producer wells. The approach of Ciz and Shapiro (2007) - an extension of the poroelastic theory of Biot-Gassmann applied to rock filled elastic material - has been used to model the velocity dispersion in the oil sand mass under different conditions of temperature and stress. A good agreement has been found between these predictions and some laboratory velocity measurements carried out on samples of Canadian oil sand. Results appear to be useful to better interpret 4D seismic data in order to locate the steam chamber.

First Al2O3 based catalytic filter candles operating in the fluidized bed gasifier freeboard

Al2O3 based grain-sintered filter element support was first impregnated with a fine, wet-milled suspension of a MgO–Al2O3 and successively with nickel nitrate hexahydrate. The catalytic filter candle was inserted in the freeboard of a 0.1m I.D. fluidized bed biomass gasifier, in order to obtain a very compact gasification and hot gas cleaning unit. Continuous catalytic steam gasification runs of almond shells have been performed in a temperature range of 808–813°C (maintained by means of an electric furnace), and the volume composition of the product gas has been analyzed by means of IR, UV and TCD facilities for online detection of CO, CO2, CH4, H2, NH3 and H2S. A 20h test has been performed with intermediate char burning steps. The measured gas yield was 2.09Nm3/kgdaf, meanwhile the gas composition in % by volume was H2=56, CO=22, CO2=20, and CH4=2. NH3 and H2S in the dry gas were 60–80ppmv and 10–15ppmv, respectively.

Mechanical Properties of Poly(Butylene Succinate) Reinforced with Continuously Steam-Exploded Cotton Stalk Bast

Poly(butylene succinate) (PBS) was reinforced by cotton stalk bast fibers (CSBF), which had been pretreated by the continuous steam explosion method. The influence of water content in CSBF during the explosion and fiber content on the mechanical properties of CSBF/PBS biocomposites was investigated. The results showed that the incorporation of CSBF decreased the tensile and impact strength, while significantly enhanced the flexural strength, flexural modulus and tensile modulus. The mechanical properties of biocomposites reinforced by exploded fibers were much better than that of the biocomposites reinforced by non-exploded fibers. Biocomposites reinforced by fibers with 40 and 50 wt% water contents during the explosion had the best mechanical properties. The morphology of CSBF and biocomposites was evaluated by SEM, which demonstrated that fibers with 40 and 50 wt% water contents had better separation and rougher microsurfaces, indicating a better adhesion between PBS matrix and fibers.

Continuous seam explosion of wheat straw by high pressure mechanical refining system to produce sugars for bioconversion

This study demonstrated the use of a pressurized mechanical refining system for the continuous steam explosion pretreatment of wheat straw. Wheat straw was first impregnated with either dilute acid (0.5% sulfuric acid) or water and then steam exploded in an Andritz pressurized refiner. The effect of a range of pretreatment conditions, including refining retention time and steam pressure/temperature on the resulting substrate composition and hydrolysability as well as overall sugars yield was investigated. For autohydrolysis, the optimum conditions, 198 oC/6 min gave an enzymatic hydrolysis yield of 93.3% and an overall glucose yield of 85.8%, while 198 oC/4 min gave an enzymatic hydrolysis yield of 88.7% and overall glucose yield of 88.4%. Longer retention time increased the enzymatic hydrolysability but reduced the overall glucose yield owing to the degradation reaction during pretreatment. For acid pretreatment, the most favourable condition for enzymatic hydrolysis and overall glucose yield coincided at 178 oC /6 min.

Syngas suitability for solid oxide fuel cells applications produced via biomass steam gasification process: Experimental and modeling analysis

The technologies and the processes for the use of biomass as an energy source are not always environmental friendly. It is worth to develop approaches aimed at a more sustainable exploitation of biomass, avoiding whenever possible direct combustion and rather pursuing fuel upgrade paths, also considering direct conversion to electricity through fuel cells. In this context, it is of particular interest the development of the biomass gasification technology for synthesis gas (i.e., syngas) production, and the utilization of the obtained gas in fuel cells systems, in order to generate energy from renewable resources. Among the different kind of fuel cells, SOFCs (solid oxide fuel cells), which can be fed with different type of fuels, seem to be also suitable for this type of gaseous fuel. In this work, the syngas composition produced by means of a continuous biomass steam gasifier (fixed bed) has been characterized. The hydrogen concentration in the syngas is around 60%. The system is equipped with a catalytic filter for syngas purification and some preliminary tests coupling the system with a SOFCs stack are shown. The data on the syngas composition and temperature profile measured during the experimental activity have been used to calibrate a 2-dimensional thermodynamic equilibrium model.

Non-isothermal crystallization kinetics and dynamic mechanical thermal properties of poly(butylene succinate) composites reinforced with cotton stalk bast fibers

Degradable poly(butylene succinate) (PBS) was reinforced with cotton stalk bast fibers (CSBF) which had been pre-treated by the continuous steam explosion method. The non-isothermal crystallization kinetics, crystalline structure and spherulitic morphology of neat PBS and CSBF/PBS composites were investigated by differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD) and polarizing optical microscopy (POM). Moreover, the dynamic mechanical thermal properties of neat PBS and CSBF/PBS composites were studied by dynamic mechanical thermal analysis (DMA). The results showed that CSBF played a dual role for acting as both nucleating agents to promote nucleation and physical hindrances to retard the transport of chain segments during the non-isothermal crystallization. In non-isothermal crystallization kinetics, the Ozawa model failed to describe the crystallization behavior of these systems, while Avrami model and Liu model (modified Avrami–Ozawa model) were found applicable. Though the spherulites drastically decreased in size when CSBF were added into PBS matrix, the crystalline structure did not change. In addition, the presence of CSBF largely enhanced the storage modulus of PBS matrix.

Quality Comparison of Continuous Steam Sterilization Segmented‐Flow Aseptic Processing versus Conventional Canning of Whole and Sliced Mushrooms

This study was carried out to investigate segmented-flow aseptic processing of particle foods. A pilot-scale continuous steam sterilization unit capable of producing shelf stable aseptically processed whole and sliced mushrooms was developed. The system utilized pressurized steam as the heating medium to achieve high temperature-short time processing conditions with high and uniform heat transfer that will enable static temperature penetration studies for process development. Segmented-flow technology produced a narrower residence time distribution than pipe-flow aseptic processing; thus, whole and sliced mushrooms were processed only as long as needed to achieve the target F₀ = 7.0 min and were not overcooked. Continuous steam sterilization segmented-flow aseptic processing produced shelf stable aseptically processed mushrooms of superior quality to conventionally canned mushrooms. When compared to conventionally canned mushrooms, aseptically processed yield (weight basis) increased 6.1% (SD = 2.9%) and 6.6% (SD = 2.2%), whiteness (L) improved 3.1% (SD = 1.9%) and 4.7% (SD = 0.7%), color difference (ΔE) improved 6.0% (SD = 1.3%) and 8.5% (SD = 1.5%), and texture improved 3.9% (SD = 1.7%) and 4.6% (SD = 4.2%), for whole and sliced mushrooms, respectively. Segmented-flow aseptic processing eliminated a separate blanching step, eliminated the unnecessary packaging of water and promoted the use of bag-in-box and other versatile aseptic packaging methods. Segmented-flow aseptic processing is capable of producing shelf stable aseptically processed particle foods of superior quality to a conventionally canned product. This unique continuous steam sterilization process eliminates the need for a separate blanching step, reduces or eliminates the need for a liquid carrier, and promotes the use of bag-in-box and other versatile aseptic packaging methods.

Fe/olivine catalyst for biomass steam gasification: Preparation, characterization and testing at real process conditions

Continuous steam gasification of biomass is carried out in a fluidized bed reactor with the utilization of 10 wt%Fe/olivine catalyst. The volume composition of the product gas is analyzed by means of IR, UV and TCD for online detection of CO, CO 2, CH 4, H 2, NH 3 and H 2S. The results obtained have been evaluated with reference to a blank test (olivine bed inventory) performed with the same experimental rig: when 10 wt%Fe/olivine is utilized in the gasifier, the gas yield increases on average by 40% and the hydrogen yield by 88%. Correspondingly, the methane content in the syngas is reduced by 16% and tar production per kg of dry ash free (daf) biomass by 46%. 10 wt%Fe/olivine characterization after test shows that the catalyst is fairly stable.

Steam condensation dynamics in annular gap and multi-hole steam injectors

In direct UHT (Ultra high temperature) treatment, milk is pumped through a closed system where it is preheated, high temperature heated, cooled, homogenised and packed aseptically [1].Continuous direct steam injection is used to quickly raise the temperature of a product, either for pure heating or for a sterilization process. The injector can be of either annular gap type (also called ring nozzle steam injector), or multi hole type. In this study we have analyzed the details of the condensation process by visualizations and by mapping the temperature fields. It was found that steam condensation in steam injectors is an intense process with heat transfer rates in the order of 1 MW/(m2 K). The steam is always condensed at the equilibrium temperature and the turbulence created in the condensation zone mixes the hot condensate and heated product with the cold product. The efficiency of this turbulent transport determines the sufficient heat transfer area and thus the size of the steam/product interface. If the condensation rate is faster than the steam addition rate the condensation process is unstable which results in detachments, fluctuations, noise and vibrations.

Research and Development of Technologies for Continuous Steam Heating for Food

Research and Development of Technologies for Continuous Steam Heating for Food

Rheological analysis of corn straw pretreated by screw extrusion and continuous steam explosion

Rheological analysis of corn straw pretreated by screw extrusion and continuous steam explosion

Impact of post combustion capture of CO2 on existing and new Australian coal-fired power plants

Currently, Australia emits approximately 600 MT equivalent of CO2 annually, of which approximately 30% is directly linked to the electricity generation using both brown and black coals. To restrain the CO2 emissions, coal based power generators are looking to retrofit the existing power plants with commercially available technology for the post combustion capture (PCC) of CO2 as well as invest in the new power plants with high efficiency steam cycles. Since Australian coals are low in sulphur and the coal-fired power plants are well away from densely populated regions, the flue gas desulphurisation (FGD) and de- NOX regulations are currently not there for the coal based electricity generation in Australia. This is not an advantageous situation for straightforward retrofitting of the existing power plants with 30 wt% aqueous MEA based commercially available PCC technology that has very limited tolerance for SOX and NOX (less than 10 ppmv). In addition, Australia is a dry continent with very limited cooling water availability for the power plants. Hence, the Australian power generators are considering both the power and the post combustion CO2 capture plants to be air cooled. This paper, therefore, assesses the impact of introducing post combustion capture of CO2 on the existing and new Australian coal-fired power plants, both brown and black coal-fired, in terms of the cost of electricity generation, the cost of CO2 avoidance, the cooling water demand and the overall plant efficiency. The existing power plants are considered to be conventional subcritical and supercritical single reheat steam cycle based whereas the new power plant designs have allowed for ultracritical steam conditions (35 MPa, 922 K) with double reheat. The CO2 capture plants are considered to be either in service full time or in service on demand with 90% capture efficiency and the product CO2 ready for sequestration at 10 MPa and 313 K. The process and cost models for integrated power and capture plants have been obtained using ASPEN Rate-Sep, Steam-Pro, Steam-Master and PEACE software packages for process modelling and cost estimation. The results clearly show that an air cooled integrated power and capture plant has lower overall plant efficiency and slightly higher cost of electricity generation in comparison with a water cooled equivalent plant. An ultracritical single reheat power plant when integrated with capture plant that is in service full time has potential for lowest cost of electricity generation with minimum cost for CO2 avoidance. These results further show that replacing an existing turbine with a new LP turbine optimised for continuous steam extraction for CO2 plant duty minimises the adverse impact of PCC integration but the power generator looses the flexibility for electricity generation. The results also provide important insights into the major contributions to the increased cost of power generation. For both the existing and the new power plants, the amortised capital charge component dominates the cost of PCC integrated electricity generation. In spite of the large reduction in efficiency for Australian power plants when PCC is applied, it appears that reducing the capital costs of PCC will be at least equally important. This is an important outcome for the prioritization of research activities aimed at reducing the costs of capture. For example, the novel solvent development work for improved PCC technology should focus on increasing absorption rates at the same CO2 carrying capacity of the solvent to reduce the capital cost component.

Using noble gases measured in spring discharge to trace hydrothermal processes in the Norris Geyser Basin, Yellowstone National Park, U.S.A.

Dissolved noble gas concentrations in springs are used to investigate boiling of hydrothermal water and mixing of hydrothermal and shallow cool water in the Norris Geyser Basin area. Noble gas concentrations in water are modeled for single stage and continuous steam removal. Limitations on boiling using noble gas concentrations are then used to estimate the isotopic effect of boiling on hydrothermal water, allowing the isotopic composition of the parent hydrothermal water to be determined from that measured in spring. In neutral chloride springs of the Norris Geyser Basin, steam loss since the last addition of noble gas charged water is less than 30% of the total hydrothermal discharge, which results in an isotopic shift due to boiling of ≪ 2.5‰ δD. Noble gas concentrations in water rapidly and predictably change in dual phase systems, making them invaluable tracers of gas–liquid interaction in hydrothermal systems. By combining traditional tracers of hydrothermal flow such as deuterium with dissolved noble gas measurements, more complex hydrothermal processes can be interpreted.

Review of Thermal Recovery Technologies for the Clearwater and Lower Grand Rapids Formations in the Cold Lake Area in Alberta

Summary Cyclic Steam Stimulation (CSS) has been a commercial recovery process since the mid 1980s in the Cold Lake area in northeast Alberta. The current bitumen production is over 220,000 B/D using CSS from this area. To achieve desired injectivity in the bitumen saturated reservoir, steam is usually injected at a pressure above or close to the fracture pressure of the formation. A relatively high pressure drawdown is created between the wellbore and formation during the production phase, particularly in the early stage of the production cycle where formation compaction and solution gas drive are the two most important recovery mechanisms. The CSS process has limited application in reservoirs with thick bottom water or in reservoirs with fine grain sands. The Steam Assisted Gravity Drainage (SAGD) process has been field tested and commercially expanded in the Lower Grand Rapids and Clearwater Formations in the Cold Lake area. In contrast to CSS, SAGD is a continuous steam injection process that relies on gravity and requires a minimum pressure drawdown to drive the reservoir fluids to the wellbore. This provides a significant advantage for SAGD as an option for the reservoirs with bottom water, top gas or with formations with fine grain sands. Several SAGD projects are in operation in different types of reservoirs in the Cold Lake and Lloydminster areas; some with thick bottom water zones. A performance review is conducted based on the available data for various CSS and SAGD projects in the Cold Lake area. The selection criteria between CSS and SAGD technologies for Clearwater and Lower Grand Rapids are discussed. Reservoir modeling results are presented concerning the impact of well placement, reservoir heterogeneity and operating parameters on SAGD performance, based on Osum's Lower Grand Rapids and Clearwater geology in the Cold Lake area.

Dilute Acid Pretreatment of Black Spruce Using Continuous Steam Explosion System

The pretreatment of lignocellulosic materials prior to the enzymatic hydrolysis is essential to the sugar yield and bioethanol production. Dilute acid hydrolysis of black spruce softwood chip was performed in a continuous high temperature reactor followed with steam explosion and mechanical refining. The acid-soaked wood chips were pretreated under different feeding rates (60 and 92kg/h), cooking screw rotation speeds (7.2 and 14.4rpm), and steam pressures (12 and 15bar). The enzymatic hydrolysis was carried out on the acid-insoluble fraction of pretreated material. At lower feeding rate, the pretreatment at low steam pressure and short retention time favored the recovery of hemicellulose. The pretreatment at high steam pressure and longer retention time recovered less hemicellulose but improved the enzymatic accessibility. As a result, the overall sugar yields became similar no matter what levels of the retention time or steam pressure. Comparing with lower feeding rate, higher feeding rate resulted in consistently higher glucose yield in both liquid fraction after pretreatment and that released after enzymatic hydrolysis.

Case History: Steam-Injection Monitoring With Optical-Fiber Distributed-Temperature Sensing

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 127937, ’Case History - Steam-Injection Monitoring with Optical-Fiber Distributed Temperature Sensing,’ by Marcelo A.P. Batocchio, SPE, Halliburton, and Adriana L.C. Triques, Hardy L.C. Pereira Pinto, Luis A.S. de Lima, Carlos F.S. Souza, and Ronaldo G. Izetti, Petrobras, prepared for the 2010 SPE Intelligent Energy Conference and Exhibition, Utrecht, The Netherlands, 23-25 March. A project was initiated by Petrobras to map the steam-front progress in a steam-assisted-production heavy-oil field. A distributed-temperature-sensing (DTS) system was installed to monitor the temperature distribution in a wellbore of a pilot program having three producers and one continuous-steam-injection well. Introduction In heavy-oil fields produced by steam injection, companies seek information to improve the drive mechanism that moves the crude oil into the wellbore. Monitoring equipment and interpretive-software tools help to achieve production requirements, maintain economic feasibility, and promote safety. In this project, high-temperature conditions were factors also. Optical-fiber DTS is a downhole-monitoring technology that provides permanent and continuous well-temperature profiling. This method enables real-time data collection, whereas traditional downhole monitoring during production provides temperature data only at a fixed point for each reading. Alternatively, wireline temperature logs can be run, but this method does not offer continuous monitoring and it affects production. With the DTS technique, the optical fiber typically is attached to the tubing and provides a complete log of the well temperature for each reading, enabling permanent and continuous monitoring without production interruption. Steam-front progress, which can improve the understanding of the reservoir geological model, can be followed; steam-breakthrough can be identified; and improved injection-efficiency then can be achieved. Project Implementation Estreito is an onshore field in northeast Brazil, 180 km from the city of Natal. This field is part of the Potiguar basin. The main reservoirs are Açu 100 and Açu 50/60, which are part of the Açu formation. These shallow reservoirs (approximately 200 m deep) originated from a fluvial depositional system. They have strong heterogeneities, have a strong active bottom aquifer (Açu 100), and are controlled by an ensemble of faults known as Carnaubais. The 15°API oil has high viscosity (2,000 cp). Cyclic steam injection began in 1984 as an improved-recovery process. This method is no longer economically viable and is being replaced by continuous steam injection. The efficiency of continuous steam injection is related directly to knowledge of heat-flow paths, which is reflected in the steam/oil ratio and the recovery factor of the area. Therefore, the operator has monitored heat transfer throughout the field since the beginning of steam injection.