Utility Steam Research Articles

Advanced Exergy, Exergoeconomic, and Exergoenvironmental Analyses of Integrated Solar-Assisted Gasification Cycle for Producing Power and Steam from Heavy Refinery Fuels

Integrated solar-assisted gasification cycles (ISGC) have emerged as a more flexible and environmentally friendly solution for producing power, steam, and other high-valued by-products from low-cost opportunity fuels. In this light, this paper investigates a new ISGC system for converting heavy refineries fuels into power and steam utilities while enhancing energy efficiency and economic and environmental performance indicators. In this approach, a solar energy field and a two-pressure heat recovery steam generator were integrated into the ISGC system to improve overall economic and environmental plant viability. The ISGC system was modelled in MATLAB software, and the results were validated using Thermoflex software. Conventional and advanced energy, exergy, exergoeconomic, and exergoenvironmental (4E) analyses were implemented to assess the main performance parameters and identify potential system improvements. The ISGC system produced 319.92 MW of power by feeding on 15.5 kg/s of heavy refinery fuel, with a thermal efficiency of 50% and exergy efficiency of 54%. The results also revealed an investment cost of $466 million, evaluated at a system cost rate of 446 $/min and an environmental impact rate of 72,796 pts/min. The conventional and advanced 4E analyses unveiled the process economic and environmental feasibilities, particularly for oil-rich countries with high availability of solar resources.

Rational Energy Recovery from the Condensed Steam as a Component of HEN Retrofit

The paper is concerned with retrofitting a heat exchanger network (HEN) using a Pinch-based method (PT) and simultaneously minimizing energy losses caused by the expansion of steam condensate. The disadvantages of conventional multi-stage condensate expansion are identified, and the application of condensate subcooling is proposed. The case study considers a Methyl-Tert-Butyl Ether (MTBE) process plant where the consumption of hot utility (steam) in the existing HEN is 4,386 kW. Using the PT method to determine the maximum possible heat recovery, it is found that heat recovery from hot process streams can be increased, leading to an increase by 510 kW in the combined heat recovery from hot process streams and condensate. Additionally, electricity production in the CHP plant (coupled with the MTBE plant by steam and condensate streams) can increase by 120 kW. HEN reconfiguration is proposed considering local constraints like the existing heat transfer areas and locations of heat-transfer equipment units. The proposal leads to a new HEN structure and a new arrangement of the equipment units in the steam and condensate system.

The Effects of Using Steam to Preheat the Beds of an Adsorption Chiller with Desalination Function

Adsorption chillers are a promising alternative to traditional compressor-based devices. Adsorption chillers can be supplied with low- or medium-temperature waste heat or heat from renewable energy sources. In addition, they can be used for water desalination purposes. Thus, the adsorption chillers are unique devices that meet essential problems of the modern world: a need to limit the negative impact of humankind on the natural environment and growing problems with access to drinking water. However, adsorption chillers also have disadvantages, including ineffective operation and large size. Therefore, in this paper, the influence of steam utilization on the operation of an adsorption chiller with water desalination function was investigated experimentally, which has not been done before. The research was carried out on the adsorption chiller, working on a silica gel–water pair, installed in the AGH UST Center of Energy. The chiller was modified to preheat the sorbent with the use of steam. The results show that the use of steam instead of water for preheating the bed leads to higher temperatures in the heat exchanger and the bed. As a result, heat transfer from the heating medium to the bed is more intense, and a significant shortening of the desorption process is observed. In the case of using steam for preheating, the desorption time was about 30 s, while for water, it was 300 s. Thanks to this solution, it is possible to reduce the size of the device and increase its efficiency. The proposed solution opens a new course of research on adsorption chillers and broadens the horizon of their applications, as steam is a by-product of many industrial processes.

Assessment of process modifications for amine-based post-combustion carbon capture processes

This study aims to provide a comprehensive comparison of different configurations of amine-based Post-combustion carbon capture (PCC) using Mono-Ethanol Amine and activated Methyl Di-Ethanol Amine (MEA and a-MDEA) solvents. A base case simulation model of a process with MEA is developed and validated at two capture rates, of 20 and 2000 tonnes per day, with the data reported in a study prepared by Nexant. The model was then used for a 1900 tonnes-per-day capture facility, and several combinations of substantial process modifications, including absorber intercooling (AIC), lean vapor recompression (LVR), and parallel exchanger arrangement (PEA) are investigated. Various scenarios for the two amine-based solvents are simulated in Aspen HYSYS®, and the results are compared with a base case conventional process for the same solvent. Results from the studied scenarios showed that a-MDEA with AIC-LVR modifications is a more attractive option due to an 8% reduction in stripper reboiler energy and its associated steam costs. The analysis of the studied cases showed that the effect of solvent on energy saving is more important than that of process modification, with the combined effect of both modification and solvent bringing higher benefits. It is also concluded that a complex process such as PCC with AIC-LVR-PEA modifications has the highest energy savings although it is less cost-effective. While OPEX (Operating Expenditure) values (mainly associated with utility steam and cooling water consumption) are still considerable, we ended up with CAPEX-intensive (Capital Expenditure) capture plants. For typical PCC equipped with combined AIC and LVR modifications (total capital investments of $136 million and $147 million were estimated for MEA and a-MDEA, respectively, translating to capture costs of US$58.80 and US$53.80 per tonne of CO2 captured. Potential savings of approximately 4–15% (for MEA) and 3–12% (for a-MDEA) were calculated depending on the scenario of combined process modifications among a shortlist of attractive options. These energy reductions portray promising reductions in the energy consumption imposed by an amine absorption-based PCC technology.

Life cycle assessment of biobased chemicals from different agricultural feedstocks

The production of biobased fuels and chemicals using renewable feedstocks is a promising alternative to achieve sustainability. Research has been focused on evaluating the economic, environmental and social performance of different products along their life cycle. Most of the published research on the evaluation of the environmental performance focuses on single products while examining mostly the global warming potential and/or the energy demand. In this work a “cradle to gate” life cycle assessment is performed for the commercial-scale production of nine different biobased chemicals. To have a comprehensive view about their total sustainability, the impact categories examined are the global warming potential, the acidification potential and the eutrophication potential. Detailed description of the processes and their simulation, design and inventories are presented to facilitate future research efforts. The analysis of the results shows that the main drivers are the production of feedstock and the use of utility steam and electricity across each impact category. Significant advantages over the fossil-based production technologies are demonstrated in all cases where reliable data are available in the open literature.

Fast Pyrolysis of Hydrolysis Lignin in Fluidized Bed Reactors

Fast pyrolysis of hydrolysis lignin was studied in fluidized bed units. Hydrolysis lignin, a bioproduct from the lignocellulosic ethanol production process (St1 Cellunolix), was processed in bench scale bubbling fluidized bed (BFB) and pilot scale circulating fluidized bed (CFB) units. Utilization of steam and ethanol as hydrogen sources was tested in a BFB unit. Major technical challenges identified were related to slow reaction rates of lignin degradation and the rapid secondary reactions in the vapor phase resulting in deposit formation and pressure buildup in product gas lines. The carbohydrate content of hydrolysis lignin had a clear correlation to its processability. More challenges with clogging and bed agglomeration were observed with lignin feedstock having lower carbohydrate content. The challenges with the bed agglomeration in the BFB unit were overcome by adding a rapidly rotating mixer in the reactor to break the agglomerates. With the CFB unit, bed agglomeration was not a problem, due to high gas velocities and forces applied to sand and lignin particles. In the BFB unit, the screw feeder was cooled and no significant melting problems were observed. In the CFB unit, melting problems were avoided by feeding the raw material in the cold section of reactor. However, severe increases in the pressure buildup and deposit formation rates were observed in both units. Steam and ethanol was tested, separately, in the BFB unit, to provide excess hydrogen in the system. Based on the product analyses both added hydrogen into the system, but hydrogen ended up mostly in the gas phase. To enhance the hydrogen transfer to the organic liquid, a catalyst active in hydrogen transfer is probably needed.

Developing an integrated hybrid polygeneration system combined with utility steam network

ABSTRACT In this study, an integrated hybrid polygeneration system based on solar and biogas energy is developed for simultaneous heat and power generation and hydrogen production. A heat recovery system is employed, which can recover the waste heat from the flue gas for effective utilisation in the steam network. The devised system, comprising solar, biogas, chemical, steam, and power islands, is investigated and comparatively evaluated through energy and exergy approaches. Additionally, an optimisation study is carried out to find the optimal exergy efficiency. The findings suggest that integrating the steam island and hybrid system improved the overall system performance significantly. The optimisation results demonstrate the value of 58.06% for exergy efficiency, while energy efficiency is also increased from 60.55% to 65.94%.

Load Cycling Tests of Reversible Solid Oxide Cells – Effects of Current Density, Steam Content, and Utilization

This work aims at developing an innovative renewable energy storage solution, based on reversible Solid Oxide Cell (rSOC) technology. That is to say, one system optimized to operate either in electrolysis mode (SOEC) for steam electrolysis to store excess electricity and to produce H2, or in fuel cell mode (SOFC) when energy needs exceed local production, to produce electricity and heat again from H2. In this work rSOC tests were conducted at single cell, in order respectively to finely understand performance and degradation mechanisms and to perform tests in representative conditions; and single cell rSOC test are finally compared to stack test results.Single cell rSOC tests were conducted to investigate the effect of current density, inlet steam content and degree of steam utilization both upon galvanostatic SOFC and SOEC testing, and upon load cycling operation. Cells having high initial electrochemical performance from Elcogen were used for these studies (1). Via four different long-term tests, we have investigated degradation at 700°C during constant galvanostatic SOFC (250 h) and SOEC (250 h) conditions followed by load cycling operation (up to 1000 h) in cycles of 16 h SOFC and 8 h SOEC. The applied current densities were either severe (0.6 A/cm2 in SOFC and -1.2 A/cm2 in SOEC) or moderate (0.4 A/cm2 and -0.6 A/cm2); applying different inlet gas composition ie. p(H2O)/p(H2) of 90/10 in SOEC and dry H2 in SOFC, or applying p(H2O)/p(H2) of 50/50 for both modes. Furthermore, two different steam and H2 utilization degrees of 80% and 40% were used. Figure 1 depicts examples of recorded cell voltage curves over time for two examples of the long-term rSOC testing where the inlet gas compositions were varied between p(H2O)/p(H2) of 50/50 for one test and p(H2O)/p(H2) of 90/10 and dry H2 for the other test.The electrochemical durability was assessed recording voltage over time and via electrochemical impedance spectroscopy (EIS). The characterization of the cells was supplemented by post-mortem scanning electron microscopy studies.Key findings include: 1) The cells degraded to a significantly larger degree in SOEC mode than in SOFC mode during the initial galvanostatic testing sequences. 2) At the given conditions and applying a current density of -1.2 A/cm2, the cells operate at a cell voltage above thermoneutral potential during the constant SOEC operation while this is not the case for the low-current density tests applying an electrolysis current of -0.6 A/cm2. 3) Load cycling does not increase the rate of degradation; rather the cell voltage stabilized for parts of the load cycling test sequences. 4) The major contribution to the resistance increase during long-term operation can be attributed to the fuel electrode and for the test, having the highest fuel electrode resistance increase (high current density test) a ~60% increase of the ohmic resistance was also observed during SOEC testing. 5) For the harshest tested (high current density) cells, Ni migration have been observed in parts of the fuel electrodes. 6) Nano-scaled detachment between Ni and YSZ particles were observed in several locations in several cells together with non-percolating Ni particles ie. where Ni-Ni connection has been lost; and a general trend was that the higher the fuel electrode overpotential during testing, the more pronounced was the effect of Ni-network changes upon microscopy post-mortem analysis in line with previous studies (2). 7) Inclusions of silica-containing impurities were found in the Ni/YSZ fuel electrodes as also observed in previous work (3, 4).Based on the single cell tests the recommendation for stack and system operation will, at 700 °C be, to operate in the current density regime of 0.4 A/cm2 and -0.6 A/cm2 rather than 0.6 A/cm2 and -1.2 A/cm2 to ensure long-term durability. Single cell test results were supplemented and trends confirmed by long-term rSOC test on 5-cell stacks at similar conditions. Figure 1: Cell voltage curves over time for two long-term rSOC test at 700°C. Inlet gas compositions of p(H2O)/p(H2):50/50 (blue curve) for one test and p(H2O)/p(H2):90/10 and dry H2 for the other test (red curve). Current densities of 0.4 A/cm2 and -0.6 A/cm2, respectively and a H2O (SOEC) and H2 (SOFC), utilization of 40%. References A. Ploner, A. Hauch, S. Pylypko, S. D. Iorio, G. Cubizolles, J. Mougin, in ECS Transactions (2019), vol. 91, pp. 2517–2526.A. Hauch, K. Brodersen, M. Chen, M. B. Mogensen, Solid State Ionics. 293, 27–36 (2016).A. Hauch, S. H. Jensen, J. B. Bilde-Sørensen, M. Mogensen, J. Electrochem. Soc. 154 (2007), doi:10.1149/1.2733861.M. Riedel, M. P. Heddrich, K. A. Friedrich, Fuel Cells. 20, 592–607 (2020). Figure 1

Solid Oxide Electrolysis System Optimization for Lunar Production of H2 and O2

Remote sensing spacecraft have located extensive surface ice in lunar permanently shadowed regions (PSRs) associated with craters near the poles. Producing H2 and O2 propellants from icy regolith in these regions requires development of integrated, robust electrolysis systems capable of operating in cryogenic environments. This team is demonstrating the feasibility of propellant production from lunar ice using high-temperature solid-oxide electrolysis (SOXE) and an optimized integrated balance-of-plant (BOP). High-temperature steam electrolysis has an efficiency advantage over PEM and alkaline electrolyzers, requiring less than 45 kWhelec kgH2 -1 [1], much less than liquid-phase electrolysis. SOXE systems require efficient steam generation and compression, heat recuperation, and subsequent drying of the H2 product stream. In this study, optimization of a demonstration system using less than 4.0 kWelec is based on OxEon’s SOXE stack that can deliver exceptionally high steam-utilization, (U H2O > 95%) and direct electrochemical O2 compression to facilitate O2 liquification with passive cooling at lunar PSR temperatures. This optimization forms the basis for the implementation of a lab-scale system for testing in a cryo-vac chamber, in order to demonstrate the viability of the optimized system for potential further, flight-scale development.The SOXE stack utilizes rare-earth stabilized zirconia electrolyte similar to technology in the MOXIE (Mars Oxygen In-Situ Resource Utilization Experiment) system [2]. The stack operates at 800ºC to balance trade-offs between area-specific resistance (ASR) and degradation. The 800ºC operating temperature requires efficient thermal integration of BOP to minimize specific energy and mass for reliable operation in the PSRs’ ‘cryo-vac’ conditions, where temperatures can reach as low as 40 K. This study shows how high U H2O enables optimization of the BOP components for system designs that can operate in the cryo-vacuum conditions with specific power w sp < 45 kWhelec kgH2 -1.Figure 1a illustrates principal BOP components including a steam generator, a compressor, cathode and anode heat recuperators, and a H2cooler/dryer. Passive radiative coolers for lunar operation prepare exhaust O2 and H2 product streams for liquification. The team developed a MATLAB-based process model to optimize the system configuration and operation. Performance of the stack, heat exchangers, and compressor are parameterized with both design parameters and system operating conditions that served as optimization variables. The system model is called by the MATLAB function ‘fmincon’ to minimize w sp under constraints that maintain reasonable system mass.The optimization study fixes H2 production rate at 0.075 kg H2 h-1 for the demonstration system in the lab-scale cryo-vac chamber. Optimization variables n this study for this lab-scale prototype system include 1) SOXE stack steam utilization U H2O ; 2) SOXE stack anode electrochemical compression DP a, for the O2 exhaust pressure; 3) steam generator vapor outlet temperature T vap; 4) compressor (scroll) pressure ratio P rat; and 5) inlet steam mass-flow split between recuperators. The SOXE electrolysis stack has a fixed cell area (110.8 cm2) and an experimentally measured area specific resistance (ASR). An electric preheater for the flow out of the cathode recuperator set the inlet steam flow to the 800 ℃ operating temperature, and this preheater added to the power (and thus specific work) required for the system. The SOXE cell operates at the thermoneutral voltage (V tn ≈ 1.28 V/cell @ 800℃) and stack current I tot is proportional to (V tn – V OCV)/ASR, where V OCV, open-circuit voltage, increases with U H2O. Primary BOP power demands include the compressor motor, SOXE stack steam preheater, thermal enclosure heater, and supplemental electric heating for the steam generator, but overall, the stack represented more than 80% of total power demand.Optimization of the system operating at 0.075 kg H2 h-1 shows that w sp had the highest sensitivity to U H2O with values above 0.85 required to achieve w sp < 45 kWhelec kgH2 -1 as shown in the contour plots of Figures 1b and 1c. Minimizing w sp encourages lower compressor pressure ratiosP rat which is limited to a minimum of 2.0. Increasing the steam generator temperature reduces compressor power demand but increases supplemental electrical heating for the steam generation, Thus, steam generator outlet temperature has minimal impact on w sp as shown in Figure 1c. Electrochemical compression of the O2 anode product does not benefit w sp, but it will greatly reduce the O2 passive cooler size which reduces mass/costs for a lunar deployed system. Additional studies are ongoing to look at trade-offs between system mass and system power with an eye toward optimizing both cost and reliability in a full-scale lunar deployed system. References Poszdeich, K. Schwarze, and J. Brabandt, Intl. J. Hydrogen Energy, 44(35), 19089-19101, 2019.Hartvigsen, S. Elangovan, J. Elwell, and D. Larsen, ECS Trans., 78(1), 2953-2963, 2017. Figure 1

Experimental Investigation of Efficiency Maximization in Solid Oxide Electrolysis Systems by Internal Steam and Heat Recovery

Solid oxide electrolysis cells (SOEC) recently experienced increasing attraction in the context of producing hydrogen from renewable energy. SOEC systems provide one of the highest efficiencies for hydrogen production from water and electrical power. With current cell-technology they can be operated at thermal neutral condition, which means that the cell itself generates no waste heat at all. Therefore the efficiency of the solid oxide electrolysis system is determined by the systems capability to recover heat and steam from the off-gas. The key component for heat recovery in an SOEC system is the steam generator because it is by far the largest consumer of energy beside the solid oxide electrolysis cell stack itself.In this contribution, the development of a scalable steam generator (Figure 1) and results with a prototype for a reversible solid oxide cell (rSOC) system with 40 kW of power in electrolysis mode will be presented. The steam recovery in this design is accomplished indirectly by reusing the heat of vaporization from condensation of the remaining steam in the off-gas to preheat the feed water (in HX1). The design is based on our long term experience with different types of steam generators for SOEC and a multiphase, multi-component pinch analysis. The pinch analysis shows clearly that a high degree of energy recovery requires focusing on the water preheating and steam superheating. Besides evaluating the optimal heat and steam integration, the prototype allows to investigate other design goals as stability, low steam contamination and high dynamic responsiveness.Furthermore this contribution discusses the benefits and drawbacks comparted to other approaches and the combination with off-gas recirculation. In the studied configuration a reduction in electrical energy for supplying superheated steam of about 20% is expected. That means at 70% steam utilization a reduction of about 5% of the specific energy demand of the SOEC system.Besides the cost reduction for cells and stacks, the development of a simple but highly efficient system designs is the key requirement to match the forthcoming demand for viable hydrogen production solutions based on SOEC. The steam supply is a major building block in that respect. Figure 1. Steam generator with heat and (indirect) steam recovery Figure 1

Advancement of steam generation process in water tube boiler using Taguchi design of experiments

Steam generation and utilization are needed in many industries and home appliances with, specific requirements. Though there are numerous categories of boilers available for steam generation, this analysis concentrated on the water tube boiler since it produces more steam and offers better safety measures. Taguchi techniques are considered in this entire research work completed through design of experiments (DOE). Orthogonal array L16 is selected to examine the steam generation with four process parameters and four levels. Selected process parameters are namely temperature of feed water (°C), the pressure of feed water (bar), cold water supply (liters), and boiler drum pressure (bar). The response of this study is the as steam generation to since increasing the steam is a target of this investigation. The experimental value of the steam generation is compared with the desired range; most of the response values are within the predicted value. Further, the superheated steam temperature and pressure analysis were also carried out. The maximum steam generation is achieved as 84.31 L; registered in the 15th run of the experiment.

Experimental Study of Concentrated Solar Power on Heat Feed Water Heaters in Steam Power Plants in Iraq

For generating power, solar energy is counted a good exporter. Iraq is located in a hot zonewith latitude from 32 degree N to 36 degree N. In Iraq, the average solar radiation is about 7kilowatt hours / day.In this work, central receiving tower was used to obtain steam using the available solar energyin summer and winter. To heat the feed water heater of South Baghdad Electrical Steam PowerPlant, steam utilization for this purpose. In the project, manufacturing the central receivertower, which is consisting of 150 mirrors fixed upon 75 manual tracking heliostats arranged forutilization the solar radiation concentrated on the central receiving tank (CRT). Pipes systemswere used for hot water or steam exits from receiver. In this study, the central receiver tank(0.5m*1m) was filled with 157 liter of water. The experimental work was run for one yearfrom June 2015 – May 2016. The outlet temperature of water from central tower receiver wassteam for (July and August 2015) and hot water with high temperature for other months of theyear. The results obtained from our system, solar shares for heating the feed water heater ofSouth Baghdad Electrical Steam Power Plant up to 1.86 % and an annual average of 1.03%.Temperature, power concentration factor and system efficient are greatly influenced by thenumber of heliostats used. A sample of calculations is used to evaluate the mathematical dataof hot water and steam temperatures obtained from this study. These values are approximatewith experimental data when compared together.

The effect of combined carbonation and steam curing on the microstructural evolution and mechanical properties of Portland cement concrete

The present study investigated the effect of the combined carbonation and steam curing on the physicochemical properties and CO2 uptake of the Portland cement concrete. Four different curing regimes were adopted during the initial 10 h of curing to evaluate the potential of carbonation curing as an alternative to conventional steam curing in the precast concrete industry from environmental and practical viewpoints. Four combinations of carbonation and steam curing conditions were applied as curing regimes to the samples at an early age. The test results indicated that the samples treated with the combined carbonation and steam curing exhibited higher early strength development compared to the other samples, signifying that carbonation curing can reduce the production time of precast concrete. Furthermore, the CO2 uptake capacity of the samples was calculated and found to be as high as 18% with respect to the mass of the paste samples. Hence, the simultaneous utilization of steam and CO2 for the fabrication of precast concrete members has the potential to make precast concrete greener and more costeffective.

Total Site Heat Integration benefiting from geothermal energy for heating and cooling implementations

Geothermal energy is a promising renewable energy source that has been developed by many countries in recent years. It can be utilised to meet various energy demand. This paper studies the performance of integrating geothermal energy in the Locally Integrated Energy Sector (LIES). The heating and cooling demand of various processes should be satisfied, and heat among processes should be recovered. This is done by using Grand Composite Curves and Total Site Profiles to visually illustrate how much load is required for utility systems. The geothermal utility system and steam utility system are compared. The integration plan for geothermal energy under different temperatures are studied. An illustrative case shows that by using this type of renewable energy under a specific and favourable condition, above 70% of steam utility load can be saved. The working cycle of using a geothermal utility system is studied by using the Time Slice model. The heat recovery plan for normal operation, mineral scaling, and cleaning periods are optimised. The minimum temperature for heat storage can also be identified.

A study on accumulator analysis for the valve performance evaluation system of nuclear power plants

Abstract To evaluate the valves used in the nuclear power plants are working properly under the required conditions, the performance and capacity test should be performed. In the test system, the accumulator was employed to control the large amount of high pressure and high temperature steam generated in the boiler precisely. In the accumulating process, the steam is often condensed. In order to prevent condensation, it is needed to install heaters and preheat the accumulator. However, if the size of the accumulator becomes large, the installation of the heater may not be easy. Therefore, when the test is conducted, the system was preheated by the latent heat generated from the phase change. Insufficient thermal insulation may cause temperature differences and it can cause mechanical problems in the accumulator structure. If insulation is sufficient, the temperature difference is indicated by the height. As the cooled condensate moves downwards, the condensate is discharged by the drain valve control and the temperature difference of the structure can be disappeared. The results of this paper can be applied to the conceptualization of equipment that uses latent heat and for the design of high-precision steam experimental devices or the design of high-capacity steam utilization systems.

Adsorption Assisted Cryogenic Carbon Capture: an Alternate Path to Steam Driven Technologies to Decrease Cost and Carbon Footprint

Carbon capture has gained momentum in addressing CO2 emissions where substitution of carbon feedstock by renewables is very challenging, such as in steel, refining, chemical, and cement industries. Gas streams containing 15% to 50% CO2 are low-hanging fruits for applying CO2 capture due to their prevalence in industry and lower capture cost linked to their high concentrations. Amine-based processes are historally considered as reference solutions for these applications, but they are no longer the only commercially viable solution today. Air Liquide has been working on a smart combination of its proprietary Adsorption and Cryogenic technologies, where Pressure Swing Adsorption (PSA) is used as a CO2 preconcentration and Cryogenic as CO2 purifiers: the Cryocap™ FG. This paper studies the influence of utilities (steam and electricity) on the carbon footprint and total cost of ownership of both amine and Cryocap™ FG technologies. The paper also studies Scope 1, 2, and 3 emissions and the TCO per ton of reduced CO2 for various footprint scenarios and typical utility costs. As it is a high efficiency power-driven technology, Cryocap™ FG resulted in a 90% reduction of Scope 1 emissions compared to 69-74% reduction with amine, depending on steam footprint, where limited waste heat is available for steam production. Cryocap™ FG was also found to be the most economical choice for electricity prices below 60€/MWh at any steam price, and the breakeven is at 120 €/MWh for a steam cost at around 10 €/t.

Long-Term Experience with a 5/15kW-Class Reversible Solid Oxide Cell System

A 5/15 kW-class reversible Solid Oxide Cell (rSOC) system was developed and experimentally investigated at the Forschungszentrum Jülich GmbH. The main component of this system is the well-established Jülich Integrated Module, which consists of four 10-layer SOC sub-stacks with an active cell area per layer of 320 cm2. The other necessary system components, such as the evaporator, condenser and blowers are compactly arranged in the vicinity of the Integrated Module. The system’s total operation time was more than 9000 h, in detail 2607 h in fuel cells, 6043 h in electrolysis and 448 h in hot standby mode. In fuel cell mode, a power of 5374 WDC at 0.5 A cm−2 at a fuel utilization of 97.3% was delivered, which resulted in a DC electrical system’s efficiency of 62.7% (LHV). Furthermore, in electrolysis mode, a power of −14347 WDC was consumed at 0.89 A cm−2. At this operating point, the system’s DC efficiency reached 70% at a steam utilization of 85%.

Assessing the value of a diversified by-product portfolio to allow for increased production flexibility in pulp mills

Abstract This paper presents a model for design optimization of pulp mill steam utility systems subject to variations in energy prices and steam demands. A Scandinavian Kraft pulp mill is used as case study to investigate investment opportunities in lignin extraction and new turbines. The model enables solutions to be identified that are more flexible than the solutions that would have been identified with a corresponding model using, for example, annual average values for key input data. The results from the case study show that lignin extraction has a potential to contribute to flexibility in pulp mill electric power production under certain conditions provided that the mill invests in both lignin extraction and condensing turbine capacity. However, the potential electric power production flexibility will vary over time. In the studied mill, with a capacity increased to around 1.3 million tonnes/a of pulp, it is estimated to vary between 15 and 30 MW. Furthermore, investment in new condensing turbine capacity only seems to be attractive if electricity prices that are considerably higher than the spot prices of recent years are assumed. Such prices may occur if there is a clear value of tradable electricity certificates or if future electricity prices rise significantly.

The energy Extended Resource Task Network, a general formalism for the modeling of production systems:Application to waste heat valorization

While real-time control of process plays an important role, it is now increasingly necessary to forecast and plan production systems in order to be energy efficient and to ensure a balance between energy demand and production. In this context, a short-term planning approach of energy supply chain is presented in this paper. Because of the presence of enthalpy balance in the optimization model, the core of this system is based on the formulation and the resolution of a Mixed-Integer Non Linear Programming (MINLP) model. To facilitate the instantiation of this optimization model and its adaptation to different kinds of value chain, a specific graphical formalism named Energy Extended Resource Task Network (EERTN) is exploited. This generic framework makes it possible to model in an unambiguous way the material and energy flows passing through any type of production system. In addition, it takes into account the influence of temperature on the physicochemical phenomena involved in the process.To illustrate the potentiality of this modeling framework, it is applied to a case study aimed at carrying out the operational planning and performance evaluation of a waste heat recovery chain. This system consists, on the one hand of an industrial unit whose heat requirements are provided by a steam utility plant, and on the other hand, of a district heating network (DHN). In this study, the problem consists to optimally plan the energy use of the district heating network by recovering the flus gas (the waste heat) from the industrial site’s power plant. The planning system leads to a significant reduction in the primary fuel consumption of the overall system and an efficient exploitation of the waste heat generated by the industrial site.

Particle Image Velocimetry (PIV) experiment of the buoyant flow field of a thermal chimney model designed for geothermal power plants

ABSTRACT To enhance the air-cooling process in geothermal power plants for economical utilization of the exhaust steam from expansion, a natural-draft thermal chimney design was proposed and studied here in this paper. In view of the necessity of accurate velocity field measurements which would provide further insight into the physics behind the evolving plumes above heated horizontal cylinders, Particle Image Velocimetry (PIV) was employed to experimentally investigate the buoyant flow in the thermal chimney system. Two configurations have been tested to understand the flow induced by the horizontally heated cylinders inside the thermal chimney. Firstly, flow field above a single row of cylinders was tested while they were isothermally heated to simulate of an air-cooled condenser. After that, a second row of cylindrical heaters (air-heater) was added above the first row to enhance the buoyant flow, aiming at enhancing the air side flow of the air-cooled condenser. Flow characteristics and velocity enhancement were studied for both configurations. The results show that significant flow unsteadiness occur near the cylindrical heaters because of the non-steady crossing flows between adjacent cylinders, and the unsteadiness attenuates in the downstream. The effects of cylinder row distance, surface temperature as well as downstream distance on the flow field were then analyzed. Flow velocity is increased by the air-heater as the buoyancy force is enhanced, proving the idea of flow enhancement of the thermal chimney configuration. It is also observed that the velocity fluctuation, turbulent kinetic energy and vorticity change significantly after adding the second row of heaters. The present study provides further insight into natural convection flow theory of heated cylinders for a Rayleigh number range of 1.3E4 to 2.2E4, which is fundamental for the flow enhancement designing of the proposed natural-convection-driven cooling system.