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A novel sensor network design (SND) algorithm is developed for maximizing process efficiency while minimizing sensor network cost for a nonlinear dynamic process with an estimator-based control system. The multiobjective optimization problem is solved following a lexicographic approach where the process efficiency is maximized first followed by minimization of the sensor network cost. The partial net present value, which combines the capital cost due to the sensor network and the operating cost due to deviation from the optimal efficiency, is proposed as an alternative objective. The unscented Kalman filter is considered as the nonlinear estimator. The large-scale combinatorial optimization problem is solved using a genetic algorithm. The developed SND algorithm is applied to an acid gas removal (AGR) unit as part of an integrated gasification combined cycle (IGCC) power plant with CO2 capture. Due to the computational expense, a reduced order nonlinear model of the AGR process is identified and parallel computation is performed during implementation. [ABSTRACT FROM AUTHOR]

The indirect coal to liquids (CTL) plant based on gasification and Fischer-Tropsch (FT) technology is technically feasible, but it is plagued with high CO2 emission in comparison to the petroleum-based fuel production processes. Addition of a moderate amount of biomass to the feed and inclusion of CO2 capture and storage (CCS) technology to the indirect CTL process can reduce its environmental footprint, but at the cost of higher capital investment as well as larger operational penalty. In this study, a techno-economic analysis of a novel indirect coal-biomass to liquids (CBTL) plant with CCS is performed using Aspen Process Economic Analyzer based on a process model developed in Aspen Plus. This paper has evaluated the impact of key investment parameters, such as raw material cost, project contingency, and process capacity, on the economic measures, including net present value, internal rate of return, payback period, and break-even oil price. In addition, the impacts of technology choices for product upgrading and carbon capture and the effects of key design parameters, such as coal/biomass ratio, type of biomass, extent of CO2 capture, and H2/CO ratio in the FT inlet stream, are evaluated. Impact of current crude oil prices on the feasibility of CBTL plants is also evaluated. [ABSTRACT FROM AUTHOR]

Molten slag flows along the wall of slagging entrained-flow gasifiers. A lower operating temperature of these gasifiers can result in slag buildup that may eventually lead to shut down. Thus, the thickness of the slag layer is an important operating variable. However, it is difficult to monitor the thickness of the slag layer due to the extremely harsh environment inside these gasifiers. To investigate the impact of various operating conditions on the slag layer thickness, a dynamic model has been developed by including models of slag deposition, transport, and a flowing slag layer in a previously developed hybrid shrinking-core, shrinking-particle model of a gasifier. The enhanced model is used to study the effect of particle size distribution, switch in coal type, change in ash composition, and various operating conditions on the slag layer thickness. The model is used to identify important variables that significantly affect the slag layer thickness. The study shows that optimal operating conditions should be decided by evaluating the risk of slag solidification at lower temperature and accelerated degradation of the refractory at higher temperature while maintaining the desired extent of carbon conversion for the given type of coal. [ABSTRACT FROM AUTHOR]

The modified Claus process is one of the most common technologies for sulfur recovery from acid gas streams. Important design criteria for the Claus unit, when part of an Integrated Gasification Combined Cycle (IGCC) power plant, are the ability to destroy ammonia completely and the ability to recover sulfur thoroughly from a relatively low purity acid gas stream without sacrificing flame stability. Because of these criteria, modifications to the conventional process are often required, resulting in a modified Claus process. For the studies discussed here, these modifications include the use of a 95% pure oxygen stream as the oxidant, a split flow configuration, and the preheating of the feeds with the intermediate pressure steam generated in the waste heat boiler (WHB). In the future, for IGCC plants with CO2 capture, the Claus unit must satisfy emission standards without sacrificing the plant efficiency in the face of typical disturbances of an IGCC plant, such as rapid change in the feed flow rates due to load-following and wide changes in the feed composition because of changes in the coal feed to the gasifier. The Claus unit should be adequately designed and efficiently operated to satisfy these objectives. Even though the Claus process has been commercialized for decades, most papers concerned with the modeling of the Claus process treat the key reactions as equilibrium reactions. Such models are validated by manipulating the temperature approach to equilibrium for a set of steady-state operating data, but they are of limited use for dynamic studies. One of the objectives of this study is to develop a model that can be used for dynamic studies. In a Claus process, especially in the furnace and the WHB, many reactions may take place. In this work, a set of linearly independent reactions has been identified, and kinetic models of the furnace flame and anoxic zones, WHB, and catalytic reactors have been developed. To facilitate the modeling of the Claus furnace, a four-stage method was devised so as to determine which set of linearly independent reactions would best describe the product distributions from available plant data. Various approaches are taken to derive the kinetic rate expressions, which are either missing in the open literature or found to be inconsistent. A set of plant data is used for optimal estimation of the kinetic parameters. The final model agrees well with the published plant data. Using the developed kinetics models of the Claus reaction furnace, WHB, and catalytic stages, two optimization studies are carried out. The first study shows that there exists an optimal steam pressure generated in the WHB that balances hydrogen yield, oxygen demand, and power generation. In the second study, it is shown that an optimal H2S/SO2 ratio exists that balances single-pass conversion, hydrogen yield, oxygen demand, and power generation. In addition, an operability study has been carried out to examine the operating envelope in which both the H2S/SO2 ratio and the adiabatic flame temperature can be controlled in the face of disturbances typical for the operation of an IGCC power plant with CO2 capture. Impact of CO2 capture on the Claus process has also been discussed. [ABSTRACT FROM AUTHOR]

Pulverized coal power plants are increasingly participating in aggressive load-following markets, therefore necessitating the design and optimization of primary superheaters for flexible operations. These superheaters play a critical role in maintaining the final steam temperature of the steam turbine, but their high operating temperatures and pressures make them prone to failure. This study focuses on the optimal design of future-generation primary superheaters for a fast load-following operation. To achieve this, a detailed first-principles model of a primary superheater is developed along with submodels for stress and fatigue damage. Two single-objective optimization problems are solved: one for minimizing metal mass as a measure of capital cost and another for minimizing pressure drop on the steam side as a measure of operating cost. Since these objective functions conflict, a multiobjective optimization problem is executed using a weighted metric methodology. Results from these optimization studies show that the base case design can violate stress constraints during the aggressive load-following operation. However, by optimizing the design variables, it is possible to not only satisfy tight stress constraints but also achieve the desired number of allowable cycles and adhere to the steam outlet temperature constraint. In addition, the optimized design reduces either the metal mass or the steam-side pressure drop compared to that of the base case design. Importantly, this approach is not limited to primary superheaters alone but can also be applied to similar high-temperature heat exchangers in other applications., Competing Interests: The authors declare no competing financial interest., (© 2023 American Chemical Society.)