Constant Steam Research Articles

Operation Scheme analysis of a multipurpose small modular reactor under cogeneration condition based on a once-through steam generator dynamic model

Highly flexible load requirements and cogeneration economy need to challenge the operation of a multipurpose small modular reactor cogeneration plant with once-through steam generators. Therefore, the present study develops a once-through steam generator dynamic model to analyze the multipurpose small modular reactor operation scheme under cogeneration conditions at different power levels. The once-through steam generator dynamic model is derived based on conversation equations using the moving boundary method. It is verified with RELAP5 results and open literature and the maximum relative error is 3.21 %. Three operation schemes are proposed for multipurpose small modular reactor cogeneration operation: Scheme 1 with constant steam pressure and average coolant temperature, Scheme 2 with constant steam temperature and pressure, and Scheme 3 with constant steam temperature and pure sliding steam pressure. Steady-state and dynamic characteristics with three operation schemes are simulated and investigated at three power levels: 100 %, 70 % and 30 %. The steady-state results show that Scheme 1 is more favorable for the primary loop, while Scheme 2 is beneficial to the secondary loop, and Scheme 3 can improve the thermal efficiency at low power level. The transient findings indicate that disturbances from the reactor side have a significant impact on the once-through steam generator and the minimum settling time is 3.3 s. Consequently, steam temperature control of once-through steam generator is achieved by regulating the control rods for Schemes 2 and 3, while steam pressure is suggested to be controlled by the feedwater valve for Scheme 1. For cogeneration conditions at 70 % power level, Scheme 2 can achieve the highest steam flow of turbine, the highest steam flow of steam extraction and the smallest steam specific volume, which are 87.88 kg·s−1, 28.96 kg·s−1, and 0.0503 m3·kg−1, respectively. Scheme 2 is recommended for high power levels under cogeneration operation. In contrast, Scheme 1 is more suitable for the condensing unit operation for low power levels.

Development of a new expression for predicting wet steam loss coefficient in steam turbines based on CFD and symbolic regression

A significant portion of the total losses in steam turbines is attributed to the thermodynamic losses of wet steam flow, which makes its prediction crucial in the design process. The Baumann rule has been used extensively in the literature, but its accuracy in some cases needs to be better due to the constant wet steam loss coefficient (α=1). To overcome the shortcomings of this rule, genetic symbolic regression is employed to derive a general expression for predicting wet steam loss for the first time. Therefore, based on Sobol sampling, 2080, two-dimensional CFD simulations for both reaction and impulse blades with different boundary conditions were performed. The data were employed to devise a new expression for wet steam loss prediction. The novel expression is verified using an in-house mean-line code on an industrial steam turbine. The new expression outperforms the Baumann rule by up to 2 % in efficiency prediction and 46 % in design pressure ratio prediction.

Operation and control of compact offshore combined cycles for power generation

Gas turbines are the main means for generating power in offshore installations. To increase energy efficiency, and thus reduce CO2 emissions, a steam bottoming cycle can be added to produce additional power by recovering surplus heat from the gas turbine exhaust. Due to space constraints, this solution is not widespread for offshore power generation. To enable deployment, the system must be compact and be able to provide varying power demands. In this paper, we analyze the operation and control problem for such compact combined cycles, consisting of two gas turbines and one steam bottoming cycle. We analyze the steady-state performance of the combined cycle with respect to efficiency and CO2 emissions for two control strategies for coordinating the power setpoint of the two gas turbines. Equal load allocation of the gas turbines showed a higher thermal efficiency and lower emissions compared to keeping one gas turbine close to nominal and letting the second one handle load variations. The main controlled variables for the steam bottoming cycle are the superheated steam pressure and temperature. We implement decentralized control strategies based on standard PID-controllers and nonlinear feedforward. Due to reduced throttle losses, sliding pressure shows higher efficiency and lower CO2 emissions compared to keeping a constant steam pressure, which conversely provides a better temperature dynamic response and may be necessary with highly varying power demand.

Numerical study on thermal hydraulics characteristics during steam submerged jet condensation from rectangular CD nozzle

The phenomenon of steam-water direct contact condensation (DCC) has significant importance in nuclear industry due to its rapid and efficient heat and mass transfer rates. In this numerical study, three dimensional simulations of steam submerged jet condensation from rectangular converging-diverging (CD) nozzle into subcooled water has been investigated. The steam condensation phenomenon has been captured from thermal phase change model as user defined function (UDF) in ANSYS Fluent software. The computational results were validated using experimental results as well as previously published numerical study. The effects of steam pressure and water temperature on distributions of various thermal hydraulics parameters including velocity, pressure, temperature, heat and mass transfer characteristics have been studied. The steam pressure and water temperature have been kept in the range of 200–500 kPa and 20–60 °C, respectively. The maximum value of jet velocity and heat transfer coefficient have been found as 803 m/s and 2.73 MW/m2K respectively. The peak velocity value increases with steam pressure. After maximum expansion point, the velocity profile curve is shifted downstream with steam pressure. The axial pressure distribution first decreases and then increases from expansion-compression waves. The axial temperature profile followed the similar trend as observed for axial steam pressure distribution. At constant steam pressure, the maximum rate of heat transfer coefficient decreases with the increase in water temperature. The maximum mass transfer rate under prescribed flow conditions has been found as 2789.8 kg/m3s. The peak mass transfer rate decreases with steam pressure and water temperature. The peak rates for heat and mass transfer have been observed in the nearby vicinity of nozzle exit location.

Numerical modelling of biomass gasification with steam injection for catalytic bed materials

Biomass gasification with steam injection in a fluidized bed reactor has emerged as a promising method to improve syngas quality by increasing hydrogen production. In this work, a simplified yet comprehensive three-dimensional multiphase model incorporating combustion chemistry and heat transfer was integrated into AVL FIRE CFD software through the implementation of user-defined subroutines. Biomass combustion and gasification for four different bed materials acting as catalysts to the biomass pyrolysis process with steam injection were investigated for this work. Beechwood was consistently used as the biofuel for all the experiments while varying the bed material. Four various types of bed materials (Silica sand, Olivine, Na–Y Zeolite, and ZSM-5 Zeolite) were used in the study and a constant steam injection was maintained. ZSM-5 Zeolite exhibited the highest hydrogen production under steady-state condition. The present model was validated against experimental results available in the literature for a lab-scale fluidized bed reactor. The model's results of species concentrations of the syngas were analyzed and compared with the experimental results and found reasonable similarity.

A coordinated control methodology for small pressurized water reactor with steam dump control system

Small pressurized water reactors (SPWRs) have complex and variable working environments with high external perturbations that challenge the operational balance and control of the primary and secondary circuits. To improve the control performance of SPWRs, a two-level hierarchy coordinated control system for SPWRs is designed in this paper. First, the equipment model of the primary and secondary circuit systems is developed. Then, based on ideal steady-state programming (ISP) with a constant coolant average temperature and a constant steam pressure, the reactor coolant average temperature, feedwater of once-through steam generator (OTSG), steam dump and steam turbine speed control systems are established by implementing PID controller. Finally, the SPWR coordinated control system is designed according to the logical relationships among the above sub-control systems, and the system is simulated and analyzed under load rejection conditions. The results show that the SPWR coordinated control system using ISP has good operational performance, and the overshoot of the coolant average temperature and steam pressure is minor under load rejection conditions, ensuring the safe operation of SPWRs.

Constant Steam Inlet Conditions and their Impact on the Thermal Efficiency of a Cogeneration Power Plant

Constant Steam Inlet Conditions and their Impact on the Thermal Efficiency of a Cogeneration Power Plant

Accelerated Stress Testing of Solid Oxide Electrolysis Cells in a Symmetric Steam-Rich Atmosphere

Temperature, current density, steam utilization variability, and local steam starvation or excess may cause diverse degradation processes to occur in solid oxide electrolysis cells. Typical degradation mechanisms for SOEC with nickel-based fuel electrode materials include nickel migration/evaporation and agglomeration, which may lead to reduced active sites at the triple-phase boundary. However, the phenomenological cause of such degradation mechanisms is still actively debated, making the selection of a durable fuel electrode material challenging. It is desirable to understand the process by which these phenomena occur not only to minimize it, but to intentionally induce it to develop accelerated stress test protocols for cell lifetime prognostics. The degradation of solid oxide electrolyzers has been reported to be accelerated by certain stressful operating conditions. Brisse and Mocotuguy conducted a review of the degradation mechanisms of solid oxide button cells; they reported that high steam partial pressures can lead to the formation of nickel hydroxide at the cathode, which then diffuse to the surface of YSZ1. Sun et al. hypothesize that this is the main mechanism for nickel migration, due to the positive oxidation state of nickel and the direction of the electric potential2. Changes in the surface morphology of the fuel electrode due to redox cycle-induced degradation has been reported, showing the dynamics of nickel migration and agglomeration under these conditions3 . Redox cycling was found to be a destructive test protocol; efforts are currently being made by the group of Daria Vladikova to prevent fracturing of the electrodes and electrolyte during such stressful testing4. Königshofer et al. have reported through multiple investigations that protocols inducing operation at high steam conversion rates (>90%) and large current densities (0.8 A/cm2) have been effective at reproducing long-term SOEC voltage degradation5,6.The objective of this research is to establish a protocol that will help determine the causes that trigger Ni migration or evaporation, and that will mimic the electrode degradation mechanism to standardize the procedure for comparing the long-term performance of solid oxide electrolysis cells. Symmetric button cells of various fuel electrode chemistries with a diameter of 20 mm (active area 1.23 cm2) are tested under symmetric atmospheres with steam/H2 blends. The following two accelerated stress tests (AST) protocols are employed: cycling of steam partial pressure and cycling of current density. In the former, the steam molar fraction is varied from 75% to 95% in a 20-minute cycle for at least 400 cycles (i.e., 1,176 h). In the latter protocol, current density is controlled using a galvanodynamic 10-minute long cyclic ramp profile between 0.8 A/cm2 and 1.5 A/cm2 at a constant steam molar fraction between 75-95% for at least 800 cycles (i.e., 1,176 h).For all tests, the cells are operated at a constant furnace temperature between 700°C and 850°C. The performance characteristics of the various cells are expressed in terms of electrochemical impedance spectroscopy (EIS) and polarization curves every 12 h during the AST. X-ray diffraction (XRD) and fluorescence (XRF) are used to analyze the cells at beginning of life and post-mortem to identify phase changes which occur during operation. Scanning Electron Microscopy - Energy Dispersion Spectroscopy (SEM-EDS) and Glow-discharge spectroscopy (GD) are used to identify and map the nickel concentration on the cathode surface and cross-section. Preliminary results suggest that the high frequency resistance may increase by nearly 500% under a constant high-steam condition (> 90%) in a Ni-YSZ|YSZ|Ni-YSZ cell during a 200 h operation. P. Moçoteguy and A. Brisse, Int J Hydrogen Energy, 38, 15887–15902 (2013).X. Sun, T. L. Skafte, and S. H. Jensen, Fuel Cells (2021).S. Yang et al., J Alloys Compd, 921, 166085 (2022).D. Vladikova et al., Energies (Basel), 15 (2022).B. Königshofer et al., J Power Sources, 523 (2022).B. Königshofer et al., J Power Sources, 497 (2021).

Optimization of inlet conditions of hot steam injection into the non-equilibrium condensing steam

Injecting hot steam into the cascade flow is one of the procedures for resisting losses and damages caused by condensation. In the current study, utilizing a 3D (three-dimensional) geometry for steam turbine blades, the hot steam has been injected into the steam cascade via the embedded channel. In the power plant industry, the hot steam injection process is done in two ways: constant pressure with a reservoir or constant mass flow rate utilizing a control valve. Therefore, considering these two methods and the TOPSIS (Technique for Order of Preference by Similarity to Ideal Solution) optimization method, the best temperature for injecting hot steam into non-equilibrium steam in a constant steam turbine blade has been gained. At the optimal temperature of 540 K at the constant pressure mode, Er (erosion rate ratio) and Lr (condensation loss ratio) were obtained as 66.6% and 30.7%, respectively, and Kr (kinetic energy ratio) showed a 0.6% growth in the hot steam injection mode, in comparison with the original mode. In addition, the economic cost of hot steam injection was calculated as 0.457 ($/hour). By the TOPSIS optimization method, the optimal temperature of hot steam injection, utilizing the constant mass flow rate method, has been obtained as 460 K, and the Er, Lr, and Kr values were 31.2%, 66.1%, and 88.48%, respectively at the optimal temperature. Moreover, the economic cost was 0.43 ($/hour). It is easier to control the steam injection by the constant mass flow rate method utilizing a control valve; therefore, the 460 K temperature and constant mass flow rate method are introduced as the optimal method.

Load Regulation Strategies of Solid Oxide Electrolysis System Coupled with External Heat Sources

Solid oxide electrolysis system requires electrical and thermal energy. Five scenarios are defined according to various cases of external heat sources coupling and electrical energy sources. Three methods are proposed to track variations in electrical or thermal load, including constant flow rate (F method), constant steam utilization (Us method) and constant cell operating voltage (V method). Through system process simulation, the applicability of three methods in different scenarios is explored to obtain load regulation strategies. In the scenario coupled with low-temperature heat and intermittent power and the scenario with no heat coupling, the F method is preferred at high loads and the V method is preferred at low loads, while it is the opposite in the scenario coupled with high-temperature heat and intermittent power. The V method is preferred at low loads in the scenario coupled with low-temperature heat and high loads in the scenario coupled with high-temperature heat.

Actor-critic reinforcement learning leads decision-making in energy systems optimization—steam injection optimization

Steam injection is a popular technique to enhance oil recovery in mature oil fields. However, the conventional approach of using a constant steam rate over an extended period can lead to sub-optimal performance due to the complex nature of the problem and reservoir heterogeneity. To address this issue, the Markov decision process can be employed to formulate the problem for reinforcement learning (RL) applications. The RL agent is trained to optimize the steam injection rate by interacting with a reservoir simulation model and receives rewards for each action. The agent’s policy and value functions are updated through continuous interaction with the environment until convergence is achieved, leading to a more efficient steam injection strategy for enhancing oil recovery. In this study, an actor-critic RL architecture was employed to train the agent to find the optimal strategy (i.e., policy). The environment was represented by a reservoir simulation model, and the agent’s actions were based on the observed state. The policy function gave a probability distribution of the actions that the agent could take, while the value function determined the expected yield for an agent starting from a given state. The agent interacted with the environment for several episodes until convergence was achieved. The improvement in net present value (NPV) achieved by the agent was a significant indication of the effectiveness of the RL-based approach. The NPV reflects the economic benefits of the optimized steam injection strategy. The agent was able to achieve this improvement by finding the optimal policies. One of the key advantages of the optimal policy was the decrease in total field heat losses. This is a critical factor in the efficiency of the steam injection process. Heat loss can reduce the efficiency of the process and lead to lower oil recovery rates. By minimizing heat loss, the agent was able to optimize the steam injection process and increase oil recovery rates. The optimal policy had four regions characterized by slight changes in a stable injection rate to increase the average reservoir pressure, increasing the injection rate to a maximum value, steeply decreasing the injection rate, and slightly changing the injection rate to maintain the average reservoir temperature. These regions reflect the different phases of the steam injection process and demonstrate the complexity of the problem. Overall, the results of this study demonstrate the effectiveness of RL in optimizing steam injection in mature oil fields. The use of RL can help address the complexity of the problem and improve the efficiency of the oil recovery process. This study provides a framework for future research in this area and highlights the potential of RL for addressing other complex problems in the energy industry.

Renewable integration and energy reduction in multiple stage evaporator

• Development of steady state energy model for a hybrid MSE. • Formulating the constrained optimization problem to maximize energy efficiency. • Implementation of a metaheuristic approach named Flow Direction Algorithm. • Incorporation of FTs and LFR to reuse waste heat and meet required thermal demand. Multiple Effect Evaporator (MEE) is an imperative part of the paper industry. It is used to process the waste byproduct named Black Liquor to enhance its solid concentration that may be further utilized to produce biomass-based energy. This process accounts very high energy consumption which leads to the energy intensiveness of this unit. A substantial amount of energy-saving may be accumulated by integrating various Energy Reduction Schemes (ERSs) with the MEE. Steam splitting, feed splitting, feed liquor preheating, thermo-vapor compressor, etc. are the well-known ERSs that may be incorporated with the MEE to reduce energy utilization. Hence, this study investigates the hybrid ERSs incorporated with MEE to observe their energy efficiency in an optimal manner. The prime focus of this investigation is to achieve enhanced energy efficiency in teams of maximum steam efficiency which is computed by formulating the nonlinear mathematical models of the MEE. To achieve the maximized energy efficiency, an optimization function has been developed under a constraint environment and solved by using metaheuristic-based approach named Flow Direction Algorithm. Another ERSs named flash tanks can also be integrated with this system to encourage waste heat re-utilization and ensures an increase in energy efficiency with constant steam consumption. This work also deals with the incorporation of the Linear Fresnel Reflector with ERSs integrated MEE which is capable of reducing the conventional energy load. The overall integrated MEE model achieves an energy-efficient and renewably operated MEE unit that may enhance the self-sustainability of the industry.

Numerical Modeling of Toe-to-Heel Air Injection and Its Catalytic Variant (CAPRI) under Varying Steam Conditions.

There are huge reserves of heavy oil (HO) throughout the world that can be energy-intensive to recover. Improving the energy efficiency of the recovery process and developing novel methods of cleaner recovery will be essential for the transition from traditional fossil fuel usage to net-zero. In situ combustion (ISC) is a less used technique, with toe-to-heel air injection (THAI) and catalytic processing in situ (CAPRI) being specialized novel versions of traditional ISC. They utilize a horizontal producing well and in the case of CAPRI, a catalyst. This paper aims to investigate the impact that injected steam has on both the THAI and CAPRI processes for the purpose of in situ HO upgrading and will help to bridge the gap between the extant laboratory research and the unknown commercial potential. This study also presents a novel method for modeling the THAI-CAPRI method using CMG STARS, proposing an in situ hydrogen production reaction scheme. THAI and CAPRI experimental-scale models were run under three conditions: dry, pre-steam, and constant steam. Starting from a reservoir American Petroleum Institute (API) of 10.5°, THAI reached an average API of ∼16 points, showing no increase in the API output with the use of steam injection. A decreased API output by ∼0.7 points during constant steam injection was achieved due to a high-temperature oxidation-dominant environment. This decreases the reactant availability for thermal cracking. The CAPRI dry run reached an API of 20.40 points and achieved an increased API output for both pre-steaming (∼21.17 points) and constant steaming (∼22.13 points). The mechanics for this increased upgrading were discussed, and catalytic upgrading, as opposed to thermal cracking, was shown to be the reason for the increased upgrading. Both processes produce similar cumulative oil (∼3150 cm3) during dry and pre-steamed runs, only increasing to ∼3300 cm3 with the constant steam injection during THAI and 3500 cm3 for CAPRI.

Investigation of condensation with non-condensable gas in natural circulation loop for passive safety system

The system-integrated modular advanced reactor 100 (SMART100), an integral-type pressurized water small modular reactor, is based on a novel design concept for containment cooling and radioactive material reduction; it is known as the containment pressure and radioactivity suppression system (CPRSS).There is a passive cooling system using a condensation with non-condensable gas in the SMART CPRSS. When a design basis accident such as a small break loss of coolant accident (SBLOCA) occurs, the pressurized low containment area (LCA) of the SMART CPRSS leads to steam condensation in an in-containment refuelling water storage tank (IRWST). Additionally, the steam and non-condensable gas mixture passes through the CPRSS heat exchanger (CHX) submerged in the emergency cooldown tank (ECT) that can partially remove the residual heat. When the steam and non-condensable gas mixture passes through the CHX, the non-condensable gas can interrupt the condensation heat transfer in the CHX and it degrades CHX performance.In this study, condensation heat transfer experiments of steam and non-condensable gas mixture in the natural circulation loop were conducted. The pressure, temperature, and effects of the non-condensable gas were investigated according to the constant inlet steam flow rate with non-condensable gas injections in the loop.

Optimisation of cogeneration system design with extended automated targeting model (ATM)

In this work, a mathematical optimisation technique known as automated targeting model (ATM) was extended for techno-economic evaluation of gas turbine (GT), steam turbine and combined cycle CHP systems. The objective is to introduce a systematic methodology for rigorous targeting of steam and power generation from complex CHP systems. In particular, the non-linear model of GT was linearised and incorporated for use in ATM. The extended ATM was applied to target minimum total annualised cost (TAC) for CHP systems in various scenarios. The extended technique was demonstrated with case studies of glycerine distillation and oleochemical plants. For the glycerine distillation plant, the result showed that combined cycle CHP system is the most cost-effective and environmental friendly scheme for the scenario, with minimum TAC of $ 5,668,000/y and carbon footprint of 69,008 t CO2e/y. In Scenario 1 of the oleochemical plant case study, with constant steam and power demand, the result showed that GT-CHP is the most cost-efficient scheme with minimum TAC and carbon footprint of $ 2,184,000/y and 24,363 t CO2e/y respectively. Meanwhile, for Scenario 2 with fluctuating steam and power demand according to plant production capacity, which is more realistic, its minimum TAC for GT-CHP only increases by 2 %. The new approach allows the identification of the optimum mode of operation at different demand conditions.

Dynamic simulation of multiple-effect evaporation

The main purpose of this work is to simulate multiple-effect evaporation and its variation as a result of the interconnection between batch and continuous unit operations. Therefore, the challenges posed by the hybrid continuous-discrete character of the model are addressed. The computer code is based on detailed fundamental material and energy balance equations, physical and thermodynamic properties, and well-proven correlations for the heat transfer coefficients. A sugarcane industry was used to demonstrate the effectiveness of the model; in this industry, there is an interconnection between a batch and a continuous process. The steam consumed in the batch process changes in each batch step. The results showed that changing the steam flow rate changes the pressure of the steam produced in a multiple-effect evaporation. Additionally, when a bypass valve and a relief valve are used to maintain constant steam pressure, it increases the overall steam consumption.

Investigation of two concrete thermal energy storage system configurations for continuous power production

Two Modelica concrete thermal energy storage (CTES) models are built to analyze potential CTES system designs. The first design is the single-pipe network design wherein a heat transfer fluid (HTF) flows in one direction during heat deposition and the opposite direction during heat removal. All pipes in the network are used for either deposition (charging) or removal (discharging). The second design is a dual-pipe network design in which a network of HTF pipes carries charging fluid and a separate piping network carries discharging HTF. This paper evaluates the operation of these two configurations to produce constant steam. Results indicate that the designs are likely appropriate for different applications: the single-pipe network appears appropriate for batch energy applications, and the dual-pipe network is appropriate for continuous energy applications.

MODERNIZATION OF THE MACHINE FOR HYDROTHERMAL TREATMENT OF GRAIN

The purpose of hydrothermal processing of grain is to change its initial technological properties in the direction ofstabilization and maintaining them at the optimal level for the further process of processing it into the final product - flour or cereals.The use of devices of continuous action allows the steaming process to become more efficient, while hydrothermal treatmentoccupies a special place in the technology of processing cereals, obtaining them high consumer properties. The analysis of designs ofdevices of continuous action, shows that the most widespread have devices of horizontal type where the main working body of thesteamer has functions of transportation and hashing. This design allows to achieve uniformity of steaming during processing of theproduct. To achieve a flexible change in the exposure of steaming, it is proposed to introduce a two-stage variator in the drive of theworking body, which will significantly change the steaming time and use the apparatus for steaming more different crops, and toensure a constant set steam pressure the design of which allows to carry out these operations without pressure losses. In the two-stageversion of the variator, the rotation from its drive shaft by means of a V-belt is transmitted to the intermediate shaft, and from it bymeans of an additional V-belt to the main working shaft. The gear ratio is adjusted by turning the glasses and their synchronous shiftin the axial direction.At the same time there is a simultaneous movement of movable conical disks, transfer of a V-belt and anadditional V-belt to other diameters. We use sluice gates with a flat sealing surface and a fluoroplastic gasket to supply grain to theworking chamber under pressure and unload it. This design allows the most effective sealing of the working chamber under pressureand to maintain the working pressure within the specified limits, with continuous loading and unloading of the device. Thecalculations show the feasibility and efficiency of modernization of the steamer by ensuring the tightness of the unloader and theuniformity of the speed of the product processed in the working chamber by using a two-stage gearbox or drive motor with afrequency converter.

Analysis of economy, energy efficiency, environment: A case study of the CHP system with both civil and industrial heat users

Integrated energy supply via the high-capacity combined heat and power (CHP) system is an effective way to achieve “win-win cooperation” for regional carbon reduction. A case study of the CHP system with both civil and industrial heat users is conducted to analysis the mixed impact of integrated energy supply on CHP systems. The steam-water equations and the off-design calculation model are developed to analyze the heat-power coupling mechanism of the CHP system. The linear-calculating diagram is obtained, which provides operational guidance for CHP system with simultaneous power, civil heat and industrial loads. Further, the analysis of economy, energy efficiency and environment within the operation region is performed. The results show that for a constant main steam flow rate, the industrial heat load is more profitable than the civil heat load. Moreover, the energy efficiency of the CHP unit can be further improved by undertaking the industrial heat load, despite at the expense of part capacity to supply civil heat. The average value of CO2 emissions per unit profit is reduced by approximately 7.69% overall after the stable industrial heat load of 100 MW, which means about 1.64 tons of CO2 can be reduced per 1000 USD profit.

Real-time steam allocation workflow using machine learning for digital heavy oil reservoirs

Traditionally, a predetermined amount of steam is allocated to various injector wells using reservoir model based open-loop optimization for thermal heavy oil reservoirs. Given that the steam supply cost is the main significant contributor to the overall production cost of heavy oil, intelligent allocation of steam to wells or pads in the oilfield deserves further attention. In this work, a proactive steam allocation workflow that accounts for steam prioritization by allocating steam from low performing wells to high performing wells is proposed. An adaptive data-driven predictive model for each individual well-pair is employed for the short-term forecast of the key performance indicators (KPIs) in real-time. The parameters of the model are continuously updated using a moving horizon approach to reflect the current state of the reservoir. Non-linear optimization is performed in each control horizon for optimal steam allocation to various injectors. The strength of the proposed method can be observed from the results as net present value (NPV) increased between 25% and 50% depending on the steam availability scenarios compared to the base case of a constant steam injection. Due to the efficient use of available steam, the steam-to-oil ratio was decreased between 5% and 15%. Steam prioritization outperforms no steam prioritization scenarios with an additional NPV increase between 14.7% and 25%.