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Title: Pilot-plant technical assessment of wet flue gas desulfurization using limestone

Abstract

An experimental study was performed on a countercurrent pilot-scale packed scrubber for wet flue gas desulfurization (FGD). The flow rate of the treated flue gas was around 300 Nm{sup 3}/h, so the pilot-plant capacity is one of the largest with respect to other published studies on a pilot-plant wet FGD. The tests were carried out at an SO{sub 2} inlet concentration of 2000 ppm by changing the recycle slurry pH to around 4.8 and the L/G ratio to between 7.5 and 15. Three types of limestone were tested, obtaining desulfurization efficiencies from 59 to 99%. We show the importance of choosing an appropriate limestone in order to get a better performance from the FGD plant. Thus, it is important to know the reactivity (on a laboratory scale) and the sorbent utilization (on a pilot-plant scale) in order to identify if a limestone is reactive enough and to compare it with another type. In addition, by using the transfer-unit concept, a function has been obtained for the desulfurization efficiency, using the L/G ratio and the recycle slurry pH as independent variables. The Ca/S molar ratio is related to these and to the SO{sub 2} removal efficiency. This function, together with amore » simplified function of the operation variable cost, allows us to determine the pair (L/G ratio and pH) to achieve the desired SO{sub 2} removal with the minimum operation cost. Finally, the variable operation costs between packed towers and spray scrubbers have been compared, using as a basis the pilot packed tower and the industrial spray column at the Compostilla Power Station's FGD plant (in Leon, Spain).« less

Authors:
; ; ; ; ;  [1]
  1. University of Seville, Seville (Spain)
Publication Date:
OSTI Identifier:
20727617
Resource Type:
Journal Article
Resource Relation:
Journal Name: Industrial and Engineering Chemistry Research; Journal Volume: 45; Journal Issue: 4
Country of Publication:
United States
Language:
English
Subject:
01 COAL, LIGNITE, AND PEAT; PILOT PLANTS; SCRUBBERS; DESULFURIZATION; FLUE GAS; LIMESTONE; LIME-LIMESTONE WET SCRUBBING PROCESSES; REACTIVITY; COMPARATIVE EVALUATIONS

Citation Formats

Ortiz, F.J.G., Vidal, F., Ollero, P., Salvador, L., Cortes, V., and Gimenez, A. Pilot-plant technical assessment of wet flue gas desulfurization using limestone. United States: N. p., 2006. Web. doi:10.1021/ie051316o.
Ortiz, F.J.G., Vidal, F., Ollero, P., Salvador, L., Cortes, V., & Gimenez, A. Pilot-plant technical assessment of wet flue gas desulfurization using limestone. United States. doi:10.1021/ie051316o.
Ortiz, F.J.G., Vidal, F., Ollero, P., Salvador, L., Cortes, V., and Gimenez, A. Wed . "Pilot-plant technical assessment of wet flue gas desulfurization using limestone". United States. doi:10.1021/ie051316o.
@article{osti_20727617,
title = {Pilot-plant technical assessment of wet flue gas desulfurization using limestone},
author = {Ortiz, F.J.G. and Vidal, F. and Ollero, P. and Salvador, L. and Cortes, V. and Gimenez, A.},
abstractNote = {An experimental study was performed on a countercurrent pilot-scale packed scrubber for wet flue gas desulfurization (FGD). The flow rate of the treated flue gas was around 300 Nm{sup 3}/h, so the pilot-plant capacity is one of the largest with respect to other published studies on a pilot-plant wet FGD. The tests were carried out at an SO{sub 2} inlet concentration of 2000 ppm by changing the recycle slurry pH to around 4.8 and the L/G ratio to between 7.5 and 15. Three types of limestone were tested, obtaining desulfurization efficiencies from 59 to 99%. We show the importance of choosing an appropriate limestone in order to get a better performance from the FGD plant. Thus, it is important to know the reactivity (on a laboratory scale) and the sorbent utilization (on a pilot-plant scale) in order to identify if a limestone is reactive enough and to compare it with another type. In addition, by using the transfer-unit concept, a function has been obtained for the desulfurization efficiency, using the L/G ratio and the recycle slurry pH as independent variables. The Ca/S molar ratio is related to these and to the SO{sub 2} removal efficiency. This function, together with a simplified function of the operation variable cost, allows us to determine the pair (L/G ratio and pH) to achieve the desired SO{sub 2} removal with the minimum operation cost. Finally, the variable operation costs between packed towers and spray scrubbers have been compared, using as a basis the pilot packed tower and the industrial spray column at the Compostilla Power Station's FGD plant (in Leon, Spain).},
doi = {10.1021/ie051316o},
journal = {Industrial and Engineering Chemistry Research},
number = 4,
volume = 45,
place = {United States},
year = {Wed Feb 15 00:00:00 EST 2006},
month = {Wed Feb 15 00:00:00 EST 2006}
}
  • A model predictive control (MPC) strategy based on a dynamic matrix (DMC) is designed and applied to a wet limestone flue gas desulfurization (WLFGD) pilot plant to evaluate what enhancement in control performance can be achieved with respect to a conventional decentralized feedback control strategy. The results reveal that MPC can significantly improve both reference tracking and disturbance rejection. For disturbance rejection, the main control objective in WLFGD plants, selection of tuning parameters and sample time, is of paramount importance due to the fast effect of the main disturbance (inlet SO{sub 2} load to the absorber) on the most importantmore » controlled variable (outlet flue gas SO{sub 2} concentration). The proposed MPC strategy can be easily applied to full-scale WLFGD plants.« less
  • Presently, decentralized feedback control is the only control strategy used in wet limestone flue gas desulfurization (WLFGD) plants. Proper tuning of this control strategy is becoming an important issue in WLFGD plants because more stringent SO{sub 2} regulations have come into force recently. Controllability analysis is a highly valuable tool for proper design of control systems, but it has not been applied to WLFGD plants so far. In this paper a decentralized control strategy is designed and applied to a WLFGD pilot plant taking into account the conclusions of a controllability analysis. The results reveal that good SO{sub 2} controlmore » in WLFGD plants can be achieved mainly because the main disturbance of the process is well-aligned with the plant and interactions between control loops are beneficial to SO{sub 2} control.« less
  • A detailed model for a wet flue gas desulfurization (FGD) pilot plant, based on the packed tower concept, has been developed. All important rate-determining steps, absorption of SO{sub 2}, oxidation of HSO{sub 3}{sup {minus}}, dissolution of limestone, and crystallization of gypsum were included. Population balance equations, governing the description of particle size distributions of limestone in the plant, were derived. Model predictions were compared to experimental data such as gas-phase concentration profiles of SO{sub 2}, slurry pH profiles, solids content of the slurry, liquid-phase concentrations, and residual limestone in the gypsum. Simulations were found to match experimental data for themore » two limestone types investigated. A parameter study of the model was conducted with the purpose of validating assumptions and extracting information on wet FGD systems. The modeling tools developed may be applicable to other wet FGD plants.« less
  • The aim of this work is to study the influence of nucleation, growth and breakage on the particle size distribution (PSD) of gypsum crystals produced by the wet flue gas desulfurization (FGD) process. The steady state PSD, obtained in a falling film wet FGD pilot plant during desulfurization of a 1000 ppm(V) SO{sub 2} gas stream, displayed a strong nonlinear behaviour (in a ln(n(l)) vs. I plot) at the lower end of the particle size range, compared to the well-known linear mixed suspension mixed product removal model. A transient population balance breakage model, fitted to experimental data, was able tomore » model an increase in the fraction of small particles, but not to the extent observed experimentally. A three-parameter, size-dependent growth model, previously used for sodium sulphate decahydrate and potash alum, was able to describe the experimental data, indicating either size-dependent integration kinetics or growth rate dispersion.« less
  • The objectives of this report are to present: the facility description, plant layouts and additional information which define the conceptual engineering design, performance and cost estimates for the pulverized coal-fired (PCF) power plant which utilizes high-sulfur coal as fuel, and a wet-limestone flue gas desulfurization (FGD) system; an assessment of the impact of using low-sulfur coal on the results of the base case conceptual engineering studies, plant layouts and cost estimates. Following the introductory comments, the results of the study of the PCF power plant with a wet-limestone FGD system are summarized in Section 2. In Section 3, the high-sulfurmore » coal case steam cycle heat balance, a performance and operating data summary and an availability assessment are provided. Sections 4 and 5 present the high-sulfur coal case power plant and FGD system descriptive information and costs, respectively. In Section 6, an assessment of the impacts of using low-sulfur coal as fuel is presented. Appendix A is the power plant and FGD system major equipment list. The design and cost estimate classification chart referenced in Section 5 is included as Appendix B. 5 references, 18 figures, 29 tables.« less