Superheated Steam Research Articles

Detection of Superheated Steam during Sterilization Using Biological Indicators.

Saturated steam (SS) is used for sterilizing many medical devices. Exposure to SS for appropriate temperature/time combinations creates a microbicidal environment that renders product sterile. Superheated steam (SHS) has been heated beyond its saturation point and is less microbicidal, compromising process efficacy. Sterilization monitoring systems should detect SHS. One method is to use biological indicators (BIs; e.g., rapid-readout self-contained BIs [RRSCBIs]). The purpose of this study was to determine if RRSCBIs can detect SHS. Pressurizing the boiler to 4,700 mB, manifold to 4,000 mB, and chamber jacket to 3,600 mB and heating the viewing window to 150°C in a 10-L BI evaluation resistometer vessel allowed approximately 12°C and 4.5°C of superheat in a nominal 121.75 ± 0.25°C and 132.5 ± 0.25°C cycle, respectively, to be reproducibly achieved. Replicate tests using multiple RRSCBIs from different batches were exposed vertically (cap up), inverted (cap down), and horizontally to SS and SHS. RRSCBI viability was determined using a fluorescent readout method. RRSCBIs exposed to SS at 121.75 ± 0.25°C for 7 or 14 minutes were negative. A total of 135 type A RRSCBIs were exposed to SHS (12°C) at 121.75 ± 0.25°C for 14 minutes. Zero of 45 RRSCBIs mounted vertically showed a positive fluorescent result, 26 of 45 mounted inverted were positive, and 45 of 45 mounted horizontally were positive. A total of 135 type B RRSCBIs were exposed to SHS (12°C) at 121.75 ± 0.25°C for 7 minutes. Twenty-four of 45 mounted vertically were positive, 41 of 45 mounted inverted were positive, and 45 of 45 mounted horizontally were positive. RRSCBIs detected SHS, but this was orientation dependent. Further work is required to establish the application of these findings in healthcare facility settings.

Predicting Silica Deposition from Superheated, Pressurized Steam Using Numerical Modeling of Nucleation, Agglomeration and Deposition

A model that can be used to quantify silica deposition from superheated depressurized steam is developed. Classical nucleation theory, agglomeration and deposition onto a wall are combined in a numerical model that calculates the concentration profile, the particle size distribution and the deposition in a flow through a pipeline after a sudden increase in supersaturation. The work presented here is an important step in understanding the mechanisms governing precipitation from supercritical and superheated steam as produced by deep geothermal wells drilled in magmatic areas. The power potential in such systems can be significantly higher than for conventional systems if utilized efficiently. The presented results can be applied to improve industrial designs and decrease energy costs. The model predicts the amount of precipitation along a pipe at various supersaturations, and the resulting deposition velocity in a straight pipe correlates fairly well with recent experimental results. There is a high number of nanocolloids formed close to the pressure reduction position, where deposition is at its maximum. Downstream, larger agglomerates develop, and deposition decreases as the number of particles and the overall concentration decreases. The local maximum deposition rate increases with increasing supersaturation. The calculations show that deposition mechanisms are as important as the chemical process of solidification when estimating where and how most material will be deposited. The rapid formation and deposition of solids predicted indicate that depressurization along with solid capture could be used to rid fluid of silica.

Superheated steam production from a large-scale latent heat storage system within a cogeneration plant

During phase change, phase change materials absorb or release latent heat at a nearly constant temperature. Latent heat thus can be stored and integrated with evaporation/condensation systems such as steam generators within a relatively narrow range of operating temperature. Storage units and systems have been proven at pilot scale but none to-date have been integrated in industrial processes. This remains a challenge, due to the size of the systems and to hurdles in design, permission and build. Here we integrate a megawatt-scale latent heat storage into a cogeneration power plant in Wellesweiler-Neunkirchen, Saarland, Germany. The storage produced superheated steam for at least 15 min at more than 300 °C at a mass flow rate of 8 tonnes per hour. This provided thermal power at 5.46 MW and results in 1.9 MWh thermal capacity. Our study demonstrates the feasibility of using latent heat storage in the industrial production of superheated steam.

Degradation by brown rot fungi increases the hygroscopicity of heat-treated wood

Heat treatment increases the decay resistance of wood by decreasing its hygroscopicity, but the wood material remains degradable by fungi. This study investigated the degradation of heat-treated wood by brown rot fungi, with the aim of identifying fungal-induced hygroscopicity changes that facilitate degradation. Scots pine sapwood samples were modified under superheated steam at 200 and 230 °C and then exposed to Coniophora puteana and Rhodonia placenta in a stacked-sample decay test to produce samples in different stages of decay. Sorption isotherms were measured starting in desorption from the undried, decaying state to investigate their hygroscopic properties. Although there were substantial differences in degradative ability between the two fungi, the results revealed that decay by both species increased the hygroscopicity of wood in the decaying state, particularly at high relative humidity. The effect was stronger in the heat-treated samples, which showed a steep increase in moisture content at low decay mass losses. The reference samples showed decreased hygroscopicity in absorption from the dry state, while the heat-treated samples still showed an increase at low mass losses. Near infrared spectroscopy showed that the early stages of decay were characterised by the degradation of hemicellulose and chemical changes to cellulose and lignin, which may explain the increase in hygroscopicity. The results provide a new perspective on brown rot decay and offer insight into the degradation of heat-treated wood.

The physical, mechanical and fire performance of bamboo scrimber processed with thermal-treated bamboo bundles

Thermal treatment is gaining increasing attention for bamboo modification in practical production due to its advantages of simplicity, effectiveness and environmental friendliness, particularly in the production of bamboo scrimber. The objective of this study is to investigate the effects of two typical thermal modification methods on the physical, mechanical and fire performance of bamboo scrimber, as well as the related physicochemical properties of bamboo bundles for production purpose. The results indicated that the two types of bamboo scrimber processed distinct advantages in terms of physical and mechanical performances. Specifically, the one processed with bamboo bundles treated by superheated steam at a temperature of 200 ℃ (referred to as the “HL group”), exhibited exceptional dimensional stability and fire resistance, while exhibiting slightly lower mechanical properties. Notably, the HL group exhibited a significantly more pronounced hue compared to the LS group, which was treated with saturated vapor at a temperature of 140 ℃. Both demonstrated exceptional water resistance, with the HL group surpassing that of the LS group in either 24-hour room temperature or a combination of boiling-drying cycling treatments. The MORs of the LS group were determined to be 152.3 MPa and 108.5 MPa under dry and wet conditions, respectively, exhibiting significantly higher values than those observed in the HL group. Conversely, the variation of MOEs was found to be opposite. Both MORs and MOEs of the two groups exhibited a significant decrease in wet condition compared to those in dry condition, with reductions linearly correlated to water absorption of the samples. The failure mode of the LS group demonstrated elastoplastic failure characterized by a “Z-shaped”, while the HL group exhibited with a relatively flat cross-section. Furthermore, the HL group demonstrated superior fire performance in comparison to the LS group, and as evidenced by a significantly denser char residue surface with fewer and wider cracks than that of the LS group. The variations of chemical components and microstructures in bamboo can be attributed to variances in the extent of degradation of hemicellulose, lignin, and even cellulose during the thermal modification processes. The water resistance, dimensional stability and fire performance of bamboo scrimber can be significantly improved through thermal treatment, while resulting in a decrease in MOR, particularly for the HL group. The HL and LS groups of bamboo scrimber both exhibited excellent performances, making them suitable for application as structural engineering materials. The work we conducted offers experimental and theoretical support for improve the pre-treatment procedures of bamboo in the manufacturing of bamboo scrimber for structural utilizations.

The Effect of Fermented Grains (koji) on Physicochemical and Sensory Characteristics of Chicken Breasts.

This study investigated the tenderizing and flavor-enhancing effects of koji, a fermented grain cultured with a single microorganism, on chicken breasts during curing. Chicken breasts were cured with different ingredients, including 4% (w/w) curing agent (GC), 5% (w/w) Aspergillus oryzae with rice (FR), A. oryzae with soybean (FS), and Bacillus subtilis with soybean (BS) for 4 h at 4 °C prior to cooking. After the superheated steam procedure, all samples were cooked in a convection oven, and their physicochemical properties were analyzed. Koji-treated samples exhibited significantly higher expressible moisture due to the degradation of the protein matrix (p < 0.05). Texture profile analysis showed that the tenderness of koji-treated samples was significantly higher than that of GC (p < 0.05). Furthermore, koji-treated samples were regarded as tenderer, and they were preferred over GC (p < 0.05) in the sensory evaluation. Principal attributes analysis revealed that the overall preference for koji-treated samples was highly correlated with umami, juiciness, and tenderness (p < 0.05). Overall, this study provides insights into applying koji as a potential curing treatment to improve the eating quality of chicken breasts. Koji can be used as a novel technology in the food industry to improve taste and tenderness simultaneously.

Effects of sodium chloride substitutes on physicochemical properties of salted beef

In this study, beef was marinated with different low-sodium salt substitutes and heated and aged by employing superheated steam roasting and traditional roasting to investigate the effects of the various substitutes on the physicochemical properties, texture profile, sensory properties, volatile compounds, microstructural characteristics, and safety of cured and aged beef. Twenty kilograms of beef were arbitrarily divided into five treatments and pickled with different low-sodium salt substitutes. The results revealed no significant differences in saltiness, physicochemical characteristics, texture profile, or volatile compounds between the T2 and T3 and T1 (100% NaCl, T1; 75% KCl + 25% NaCl, T2; 50% KCl + 50% NaCl, T3) samples. Furthermore, the T4 and T5 (50% NaCl + 25% KCl + 20% MgCl2 + 5% CaCl2, T4; 100% yeast extract, T5) samples had lower saltiness than the T1 sample. The plasmolysis percentage and osmotic pressure of the T2 and T3 samples were lower than those of the T1 sample. Therefore, reducing sodium by substituting NaCl with 50% KCl or 75% KCl maintained an acceptable sensory and safety profile for beef consumption.

Effects of different high-temperature conduction modes on the ovalbumin-glucose model: AGEs production and regulation of glycated ovalbumin on gut microbiota

Food high-temperature processing frequently induces the production of advanced glycation end products (AGEs) in the food industry. In this study, the effects of three high-temperature conduction modes on the AGEs production derived from ovalbumin (OVA)-glucose model and the regulation of glycated OVA on gut microbiota were investigated. The peak time of OVA shifted maximally from 13.72 to 13.57 due to the rise in molecular weight, confirming successful coupling between OVA and glucose. The inhibition of superheated steam (SS) on AGEs was observed, with the sample treated by SS showing the lowest content among glycated OVA groups. The analysis revealed an increase in AGEs during digestion and a decrease in fermentation, suggesting the release during digestion and the availability by intestinal flora. Furthermore, an expansion of Bifidobacterium and Lactobacillus, and the inhibition of Desulfovibrio and Escherichia-Shigella were observed, indicating the prebiotic activity of glycated OVA and its potential to improve intestinal health. These results provide valuable information for controlling high-temperature processing to inhibit AGEs formation and highlight the positive effects of glycated proteins on intestinal health.

The Potential of Vapor Compression Heat Pumps Supplying Process Heat between 100 and 200 °C in the Chemical Industry

The supply of process heat in the chemical industry is dominated by fossil fuel combustion. Heat with temperatures up to 200 °C could, however, be supplied by vapor compression heat pumps (VCHPs), allowing for efficient electrification. However, there are still several barriers that need to be overcome before they can be widely implemented. In this work VCHPs are thermodynamically compared to heat-driven heat pumps and heat transformers, exploiting the potential of VCHPs. Moreover, steam production, distillation and drying are found to be of primary interest within the chemical industry, and potential integration points are presented and discussed for these applications. Finally, a financial analysis is performed based on a steam production and a superheated steam drying case study. The analysis calculates the levelized cost of heat (LCOH) of a VCHP, heat transformer, natural gas boiler and electric boiler. Furthermore, a sensitivity analysis of the LCOH to the annual operating hours, carbon pricing and waste heat availability is presented. Generally, when no emissions trading scheme (ETS) is applied, both the VCHP and a combination of a heat transformer with auxiliary natural gas boiler appeared as the most optimal solutions, depending on the energy prices. Due to the limited utilization of waste heat by the heat transformer, an auxiliary natural gas or electric boiler is essential to fully meet the required heating load. When an ETS is being applied the VCHP generally appeared to be most financially attractive technology for both the case studies.

The effects of superheated steam roasting on proximate analysis, antioxidant activity, and oil quality of black seed (Nigella sativa).

Nigella sativa, commonly known as the black seed, is a culinary spice therapeutic against many ailments. Common preparation practice of roasting or heating the seeds often deteriorates bioactive compounds, which can be remedied with superheated steam (SHS). With roasting temperatures of 150, 200, and 250°C and roasting times of 10, 15, and 20 min, convection and SHS roasting media were tested, and their effects on proximate analysis, antioxidant assays, and oil quality were evaluated. For proximate content, moisture significantly decreased from 9.08% in unroasted seeds to 4.18%-1.04% in roasted seeds, while fat increased to as high as 44.76% from 32.87% in unroasted seeds. Roasting only slightly increased ash content and had no significant impact on protein and carbohydrate content. SHS roasted black seeds had better DPPH (2,2-Diphenyl-1-picrylhydrazyl) radical scavenging capacity (RSC) than convection roasted seeds. DPPH RSC decreased with elevated roasting time and temperature, conversely related to total phenolic content, which increased with increased roasting time and temperature. Oil of roasted seeds developed an increasingly intense brown color from an initial light, yellow, unroasted oil with better extraction efficiency in SHS roasting. For oil quality analysis, free fatty acid values were significantly lower in both roasted samples. Peroxide value was initially recorded at 84 in convection and 48 (meq O2/kg of oil) in SHS roasted samples. In contrast, p-anisidine values were initially recorded at 28.36 in convection roasted samples compared to 23.73 in SHS roasted samples. Based on all quality analyses, SHS showed better potential in black seed quality preservation.

Impact of Treatment with Superheated Steam on the Structural, Thermal, and Functional Characteristics of Quinoa Starch

AbstractThe objective of the study is to evaluate the impact of treatment with superheated steam on the structural, thermal, and functional characteristics of quinoa starch. The superheated steam treatment is applied to the starch at 130 and 170 °C for 1 and 4 min, then dried at 50 °C and stored. Moisture adsorption isotherms are performed at 25 °C, and data are fitted to the Oswin, GAB, and Peleg models. Structural characterization is done using XRD and FTIR, thermal analysis using DSC, and functional characterization include water absorption capacity (WAC), oil absorption capacity (OAC), and syneresis. The QS170/4 treatment shows a reduction in crystallinity index of up to 48.24%, with the appearance of the amylose‐lipid complex, an increase in initial and final gelatinization temperatures, and a decrease in enthalpy of up to 39.53%. For modified starches, WAC and OAC increase by 9% and 7%, respectively, and syneresis decreases significantly by 17.4%. The results demonstrate the feasibility of modifying quinoa starch with superheated steam treatment, which, unlike other methods, has the advantage of altering the amylose and amylopectin chains in just a few minutes. Thus, the results show a new perspective for the use of superheated steam in starch modification.

Inactivation of E. coli O157:H7, Salmonella enterica, and L. monocytogenes through semi-continuous superheated steam treatment with additional effects of enhancing initial germination rate and salinity tolerance

Superheated steam (SHS) is a powerful technology used to reduce bacteria on food surfaces while causing less damage to the underlying sublayer of food compared to conventional heating treatments. In this study, a semi-continuous SHS system was developed to inactivate foodborne pathogens within 1 s (Escherichia coli O157:H7, Salmonella enterica, and Listeria monocytogenes) on radish seed surfaces and to enhance the seeds’ salinity tolerance, which is vital for adapting to arid and semi-arid regions. The temperature of the SHS was set to 200 °C and 300 °C, with flow rates of 5 m/s and 7 m/s, and treatments were cycled either once or three times. As a result, increased temperature (200 °C–300 °C) and number of treatments (1 time to 3 times) led to a significantly larger microbial reduction on the surface of radish seeds. E. coli O157:H7, S. enterica, and L. monocytogenes were reduced by 4.42, 4.73, and 3.95 log CFU/g (P < 0.05), respectively, after three SHS treatments at 300 °C and 7 m/s. However, due to the ongoing potential for recovery of residual microorganisms, further research involving combinations is essential to enhance the microbicidal effect. Water imbibition showed significantly higher values in the SHS-treated group up to 30 min, indicating faster germination rates in the SHS-treated group (71.3–81.3%) compared to the control group (52.7%) on the second day, indicating a significant enhancement in germination rate. In addition, the salinity resistance of the radish seeds increased after SHS treatment. When moisturized with 0.5% NaCl solution, more radish seeds germinated after treatment with SHS (40%) than controls (22.7%) (P < 0.05). The results of this study, the first to apply semi-continuous SHS to seeds, are expected to serve as a cornerstone for future pilot-scale investigations aiming to implement the system within the seed industry.

Techno-economic optimization and Nox emission reduction through steam injection in gas turbine combustion chamber for waste heat recovery and water production

Considering the persistent human need for electricity and fresh water, cogeneration systems based on the production of these two products have attracted the attention of researchers. This study investigates a cogeneration system of electricity and fresh water based on gas turbine (GT) as the prime mover. The wasted energy of the GT exhaust gases is absorbed by a heat recovery steam generator (HRSG) and supplies the superheat steam required by the steam turbine (ST). In order to produce fresh water, a multi-effect desalination (MED) system is applied. The motive steam required is provided by extracting steam from the ST. In order to reduce the environmental pollution of this cogeneration system, the steam injection method is proposed in the GT's combustion chamber (CC). This system is optimized by a multi-objective optimization tool based on the Genetic Algorithm (GA). The design variables include pressure ratio of compressor (CPR), inlet temperature of gas turbine (TIT), steam injection mass flow rate in the CC, HRSG operating pressure, HRSG evaporator pinch point temperature difference (PPTD), steam pressure of the MED ejector, ejector motive steam flow rate, number of MED effects, and return effect. The goals are to minimize the total cost rate (TCR), which includes the cost of initial investment and maintenance of the system, the cost of consumed fuel, and the cost of disposing of CO and NO pollutants, as well as maximizing the exergy efficiency. In the end, it is observed that the steam injection in the CC leads to the reduction of the mentioned pollutant index, and it is proposed as a suitable solution to reduce the pollution of the proposed cogeneration system.

Scientific Foundations for the Aerohydrodynamic Grinding of Lignocellulosic Raw Material under Steam Explosion

The results of studies aimed at improving the methods and equipment for the preliminary treatment of lignocellulosic raw materials by means of steam explosion are presented. The scientific basis for the outflow of superheated steam from a reactor in the course of detonation boiling of a liquid is described. Based on theoretical and experimental studies, it is shown that, in order to provide an increase in the efficiency of the steam explosion energy, it is appropriate to mount an aerohydrodynamic grinder (AHG) containing a Laval nozzle at the reactor outlet.

Sustainable Superheated Steam Drying of Unripe Banana (Musa acuminata cv. Hom Thong): Effects on Resistant Starch and Physicochemical–Functional Properties

AbstractUtilizing unripe banana flour (UBF) has gained considerable interest recently due to its functional components, particularly its resistant starch (RS), which could control obesity and diabetes. This study explores the novel approach of superheated steam drying (SSD) to produce UBF. Banana slices with 1, 2, or 3 mm thicknesses are dried using SSD at 75, 85, 95, or 105 °C. The resulting UBFs are analyzed for starch content and physicochemical–functional properties and compared with conventional hot‐air drying (HAD) at 55 or 75 °C. Replacing HAD with SSD saves 75% of the drying time and increases the whiteness index. SSD‐produced UBF has a high RS content, excellent resistance to enzyme digestion, and potential beneficial health effects. At the same time, scanning electron microscopy shows that the SSD‐ and HAD‐dried samples have similar morphological characteristics. The swelling power, water solubility index, and water holding capacity of the UBF increases rapidly above 70 °C. The peak viscosity, breakdown, and setback of SSD‐dried UBF are greater than those of HAD at the same temperature. Technological properties (high hydration value and peak viscosity) and reduced processing time make SSD‐dried UBF a potential natural thickening ingredient for the food industry.

Preparation of Teakwood Bending Components with Excellent Softening Properties by Vacuum Impregnation with Triethanolamine Compounding Solution

To study the softening bending properties and mechanism of teakwood, it was extractively pretreated by using superheated steam, the triethanolamine compound was used as a softening solution, which was infiltrated into the wood by vacuum impregnation and synergistically softened through saturated steam to improve the bending properties of teakwood. Analysis by Fourier transform infrared spectroscopy (FTIR), Carbon 13 nuclear magnetic resonance (13C NMR), and X-ray photoelectron spectroscopy (XPS) showed that the synergistic softening treatment elevated the content of O and N elements in the softening solution and together with the C elements in the wood, formed C-NH2 and C-N bonds, which increased the molecular activity and improved the softening properties of teakwood. Scanning electron microscope (SEM) observations revealed that the outer conduits, cell walls, and fibrous tissue structures of the teakwood were stretched after softening and bending, and even microcracks of different degrees were formed between the cell walls. According to the load–deformation relationship of teakwood softening bending, the stress–strain relationship was theoretically derived and the bifold constitutive model of teakwood bending was constructed after fitting the constitutive relationship data, the integrated correlation coefficient R2 was 96.25%, which proved that the present model can better simulate the constitutive relationship of teakwood in bending.

Modeling of multiple thermal fluid circulation in horizontal section of wellbores

The development of heavy oil reservoirs has broad prospects. Because heavy oil reservoirs have the characteristics of high viscosity and poor fluidity, they often need to be heated. For heavy oil reservoirs, the effect of simple steam injection development is limited. By mixing superheated steam or steam with non-condensable gas, the development effect of heavy oil can be improved. Due to the high viscosity of heavy oil reservoirs, the initial injection capacity of the heat carrier is poor, and cyclic preheating is often required. In this paper, through theoretical research, the process of multi-element thermal fluid injection in heavy oil reservoirs is studied. The circulation preheating characteristics of the multi-element thermal fluid inside the wellbore are analyzed. Results show that for different ratios of nitrogen to carbon dioxide: when the multi-element thermal fluid flows from the finger end (1000 m) to the heel end (0 m) of the annular space, the oil layer heat absorption rate first drops and then rises.

A hybrid receding horizon optimization and active disturbance rejection control of boiler superheated steam temperature

Efficient control of superheated steam temperature is critical for maintaining the safety and efficiency of a power plant boiler. Exceeding the safe temperature range can cause irreversible damage. However, unknown disturbances and uncertainties, as well as large delay dynamics, often make superheated steam temperature safety control challenging. To this end, this paper proposes a hybrid bi-level safety control for superheated steam temperature control in a power plant boiler. The bottom level uses active disturbance rejection control, while upper level uses receding horizon optimization. The proposed method combines the advantages of active disturbance rejection control in solving unknown disturbances and the dynamic optimization of receding horizon optimization to effectively and safely control superheated steam temperature and optimize the control system performance. The main novelty of the scheme lies in making receding horizon optimization independent of the model of the plant, in terms of making full use of the closed-loop desired dynamics under active disturbance rejection control. Practical synthesis design methods are also presented to illustrate the tuning and optimization of this control strategy. On-site testing results show that the proposed method improves both disturbance rejection and tracking performance, with improvements of at least 20 % over comparison methods. In conclusion, the proposed bi-level control strategy is a promising approach for improving the safety and efficiency of power plants.

Thermodynamic analysis of integrated ammonia fuel cells system for maritime application

This paper presents a novel multigeneration system that utilizes ammonia as the primary fuel for marine vessel applications. The system integrates and thermodynamically investigates various components, including solid oxide fuel cells (SOFC), gas turbines (GT), proton exchange membrane fuel cells (PEMFC), organic Rankine cycle (ORC), steam Rankine cycle (SRC), Kalina cycle (KC), and waste heat boiler (WHB). The primary objective of the integration strategy is to recover waste heat from the SOFC and harness the power generated by the PEMFC, resulting in improved thermal efficiency, reduced vessel startup time, and enhanced environmental sustainability. Mathematical models have been developed to facilitate the examination of the system’s thermodynamic performance. Comprehensive thermodynamic modeling employing energy and exergy analysis methods is employed to evaluate the effectiveness of both the proposed system and its subsystem. Moreover, the exergy destruction of all system components and integrated subsystems is quantified to provide a comprehensive understanding of their impact. The projected system exhibits an energy efficiency of 60.69% and an exergy efficiency of 57.50%. The waste heat recovery combined systems generate 1634.46 kW, accounting for 30.07% of the total power output of the integrated SOFC system. The performance of the system was analyzed through parametric studies, where different values of current density, distribution ratio (β) (from 0.1–0.4), and δ parameter (from 0–0.5) were examined. The findings revealed that increasing the current density led to a decrease in energy and exergy efficiency, despite an overall rise in the power output of the cogeneration system. Moreover, the waste heat boiler is capable of providing 1081 kg/h of superheated steam at 162 °C and 405 kPa to fulfill the heating requirements of marine lubricating oil, devices, and accommodation for seafarers on board the ship.

Modelling and regulation of steam temperatures of a 1000‐MW double‐reheat boiler with long short‐term memory

AbstractWith the increase in the proportion of new energy power generation in grids, there is an urgent need for the flexible operation of coal‐fired power plants. However, as the most efficient commercial coal‐fired power generation technology, the flexibility of double‐reheat ultra‐supercritical units is limited due to the steam temperature fluctuation in transient processes. To inhibit the steam temperature fluctuations, a data‐driven method, called long short‐term memory (LSTM) was introduced to model the dynamics of the steam temperatures of a 1000‐MW double‐reheat coal‐fired boiler. Moreover, an advanced controller was proposed by combining the LSTM‐based dynamic model and the model predictive control architecture. The results demonstrate that the LSTM model can be used to capture the time delay, multivariable coupling and non‐linear dynamics of the steam temperatures and the proposed controller exhibits excellent performance in steam temperature regulation. The superheated steam temperature fluctuation decreases from 15.4 to 9.8°C, the primary reheat temperature fluctuation decreases from 34.6 to 8.3°C, and the secondary reheat temperature fluctuation decreases from 41.4 to 8.8°C. The proposed method has good potential to stabilize steam temperatures during transient processes of wide‐range load cycling, and finally improves the flexibility of the double‐reheat ultra‐supercritical unit.