Desulfurization Plants Research Articles

Energy-Saving Analysis for Power System Reactive Power Compensation

The alternator output power in the power system can be divided into active and reactive power. The active power (in kW) is that part of the electrical energy for doing work and heat loss, such as the conversion of mechanical energy, heat, light. The reactive power (in kVar) is that part of the electrical energy for the exchange of electric and magnetic fields in the circuit, such as transformers, motors, through the magnetic field can be passed to convert electrical energy; transmission lines in cable systems and a variety of load reactance (inductance and capacitance), and consumption of reactive power. With the rapid development of power system to study how to reduce energy loss in the power system is a very meaningful. In this paper, The Shizuishan plant desulfurization project as an example, illustrates the shunt capacitor reactive power compensation of the power system energy saving.

Robust optimization-based multi-loop PID controller tuning: A new tool and its industrial application

Modern process plants are highly integrated and as a result, decentralized PID control loops are often strongly interactive. The iterative SISO tuning approach currently used in industry is not only time consuming, but does also not achieve optimal performance of the inherently multivariable control system. This paper describes a method and a software tool that allows control engineers/technicians to calculate optimal PID controller settings for multi-loop process systems. It requires the identification of a full dynamic model of the multivariable system, and uses constrained nonlinear optimization techniques to find the controller parameters. The solution is tailored to the specific control system and PID algorithm to be used. The methodology has been successfully applied in many industrial advanced control projects. The tuning results that have been achieved for interacting PID control loops in the stabilizing section of an industrial Gasoline Treatment Unit as well as a Diesel Desulfurization plant are presented.

Formation and decomposition of tetrafluoroborate ions in the presence of aluminum

The formation and decomposition of tetrafluoroborate ions (BF 4 − ) in H3BO3-Al3+-F− solutions were investigated via experiments and thermodynamic calculations. The concentration of the formed BF 4 − increased with decreasing pH, raising the total fluoride concentration and lowering the total aluminum ion concentration. Once formed, BF 4 − was stable under neutral and alkaline conditions. Fluoride in the form of BF 4 − was converted to fluoroaluminate ions by adding an aluminum compound under acidic conditions. A method for removing fluoride in the form of BF 4 − is proposed whereby fluoroaluminate ions formed by the reaction of BF 4 − with aluminum are decomposed with calcium ions. This process was applied to the treatment of wastewater from flue gas desulfurization plants, and resulted in a satisfying level of reduction in the range of the fluoride emission limit of 8 mg/l.

Using Neural Networks to Address Nonlinear pH Control in Wet Limestone Flue Gas Desulfurization Plants

In previous articles,(1-3) we evaluated the performance of different linear control strategies (decentralized feedback control and multivariable predictive control) in wet limestone flue gas desulfurization (WLFGD) plants based on a pilot plant study. Although these control strategies show good performance, they may not be suitable if the oxidation tank pH is significantly nonlinear, which depends on many plant operating factors. Control of oxidation tank pH is important since it is related to the quality of gypsum, a byproduct of the WLFGD process. In this work, we propose and assess a combined control strategy for dealing with nonlinear pH control in WLFGD plants, based on a decentralized strategy composed of a neural predictive controller and a feedback controller, which control the oxidation tank pH and SO2 concentration of the desulfurized gas, respectively.

Controllability Analysis and Decentralized Control of a Wet Limestone Flue Gas Desulfurization Plant

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 SO2 regulations have come into force recently.(3) 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 SO2 control 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 SO2 control.

Dynamic Analysis and Identification of a Wet Limestone Flue Gas Desulfurization Pilot Plant

In order to meet more stringent SO2 regulations that have come into force recently, the operating conditions of wet limestone flue gas desulfurization (WLFGD) plants must be changed from design conditions to others where a higher SO2 removal is obtained; this results in higher operating costs. Furthermore, because of process disturbances, the SO2 removal target is usually set somewhat higher than necessary to provide a safety margin for meeting SO2 emission limits. Thus, the larger the safety margin, the higher the operating costs. How much larger the safety margin needs to be depends on the proper tuning of the control strategy and dynamic properties of the WLFGD plant to be controlled. Both aspects can only be studied if a dynamic model of the plant is available. However, dynamic modeling of WLFGD plants for control purposes has not been addressed in the literature so far. To deal with with this issue, in this paper we propose an identification methodology for control purposes applicable to full-scale plants. The identification methodology is put into practice in a WLFGD pilot plant, and the empirical dynamic model obtained is suitable for predicting the dynamic behavior of the pilot plant in a wide range of operating conditions. The dynamic behavior of the pilot plant is further analyzed from the perspective of the physical−chemical phenomena of the WLFGD process.

Foaming in Wet Flue Gas Desulfurization Plants: The Influence of Particles, Electrolytes, and Buffers

The objective of this work is to study the influence of particles, electrolytes, and buffers on the foaming ability of wet flue gas desulfurization (FGD) slurries. Foaming within this industrial process has been associated with a range of operational problems, as well as an increased degree of absorption. The foaminess of selected process parameters has been assessed, systematically, using laboratory-scale Bikerman experiments. Adipic acid alone, as well as a combination of small particles and an electrolyte, have been demonstrated to generate weak transient foams (with a Bikerman coefficient (Σ) of ≤7 s), that potentially can interfere with process monitoring equipment. Additional experiments with a wet FGD pilot plant showed an increased absorption efficiency of sulfur dioxide (SO2) by a tap water solution with small quartz particles and calcium chloride (CaCl2), compared to a solution of pure tap water.

Application of artificial neural networks to predict chemical desulfurization of Tabas coal

This paper presents a neural network model to predict the effects of operational parameters on the organic and inorganic sulfur removal from coal by sodium butoxide. The coal particle size, leaching temperature and time, sodium butoxide concentration and pre oxidation time by peroxyacetic acid (PAA) were used as inputs to the network. The outputs of the models were organic and inorganic sulfur reduction. Feed-forward artificial neural network with 5-7-10-1 arrangement, were capable to estimate organic and inorganic sulfur reduction, respectively. Simulated values obtained with neural network correspond closely to the experimental results. It was achieved quite satisfactory correlations of R 2 = 1 and 0.96 in training and testing stages for pyritic sulfur and R 2 = 1 and 0.97 in training and testing stages, respectively, for organic sulfur reduction prediction. The proposed neural network model accurately reproduces all the effects of operational variables and can be used in the simulation of Tabas coal desulfurization plant.

Conversion of a Wet-Process Flue-Gas Desulfurization Plant from Quicklime (CaO) to Chalk (CaCO3)

Conversion of a desulfurization plant from quicklime to chalk requires high reactivity of the chalk products. In contrast to other CaCO3 products, chalk, as a result of its origin, with a mean particle size of 2 to 3 μm is a sorbent offering high reactivity and the possibility for replacing the conventional lime additive. Further advantages of chalk over high-calcium lime are economic efficiency and easy handling.

Optimum Values of Process Parameters of the “Wet Limestone Flue Gas Desulfurization System”

In this article the method of cost optimization of the “Wet Limestone Flue Gas Desulfurization System” is presented. The optimization calculations include process and cost models. The process model describes the most important stage of SO2 removal that runs in the absorber and in the holding tank. It includes absorption of sulfur dioxide, oxidation of SO2–3, dissolution of limestone, and crystallization of gypsum. The model was applied to calculate indispensable parameters for estimating costs and then to minimize capital and operating costs. Costs of all important equipment were estimated, such as SO2 removal systems with the absorber and the holding tank, reagent feed system with the ball mill and dewatering gypsum slurry system. Optimum values of the process parameters for different conditions of running flue gas desulfurization system were found. The process and cost model can be useful when designing the wet limestone FGD systems and carrying out economic analysis of the flue gas desulfurization plants.

Optimum Values of Process Parameters of the “Wet Limestone Flue Gas Desulfurization System”

In this article the method of cost optimization of the “Wet Limestone Flue Gas Desulfurization System” is presented. The optimization calculations include process and cost models. The process model describes the most important stage of SO2 removal that runs in the absorber and in the holding tank. It includes absorption of sulfur dioxide, oxidation of SO2–3, dissolution of limestone, and crystallization of gypsum. The model was applied to calculate indispensable parameters for estimating costs and then to minimize capital and operating costs. Costs of all important equipment were estimated, such as SO2 removal systems with the absorber and the holding tank, reagent feed system with the ball mill and dewatering gypsum slurry system. Optimum values of the process parameters for different conditions of running flue gas desulfurization system were found. The process and cost model can be useful when designing the wet limestone FGD systems and carrying out economic analysis of the flue gas desulfurization plants.

Improvement of the efficiency of flue gas desulfurization plants — use of adipic acid in the Frimmersdorf Brown Coal Power Plant of RWE Energie AG

Improvement of the efficiency of flue gas desulfurization plants — use of adipic acid in the Frimmersdorf Brown Coal Power Plant of RWE Energie AG

Effect of Limestone Concentration and Particle Size on SO2 Absorption in Wet FGD Process.

To investigate the mechanism of SO2 absorption with the chemical reaction in the limestone-gypsum process, the effect of limestone concentration and particle size on the SO2 absorption rate in limestone slurry was studied by using a stirred tank reactor at a constant pH and high temperature (50°C). An absorption model with a reaction plane based on the film model was also proposed for an actual flue gas desulfurization (FGD) plant. For the SO2 absorption rate depending on the concentration and particle size of limestone powder, the experimental values agreed quite well with the results calculated with the absorption model, regarding the limestone dissolution rate within the liquid.

Modernizing the Desulfurization Plant Using Contact Nits of the Vniius-14 Type

The positive industrial experience in the use of contact devices of the VNIIUS-14 type in mono- and diethanolamine scrubbing of hydrogen sulfide from gases at oil refineries is described. The expediency of replacing bubble trays, whose operation is associated with extreme foaming with negative effects, by VNIIUS-14 contact devices operating in the jet-dispersion mode, which excludes foaming and consequently its negative consequences, is confirmed.

Weather-induced changes in the tradeoff between SO 2 and NO x at large power plants

Mae Moh Power Plant generates 30% of Thailand's electricity by burning high sulfur content coal which comes from adjacent mines. The resulting sulfur dioxide emissions have been blamed for acid rains in the Mae Moh valley in 1991 and 1992. Mae Moh is now adding desulfurization plants to 60% of its 1994 generating capacity — the four largest units of an 11-unit facility. In 1995–1996, Mae Moh added two additional large units with desulfurization plants attached. The desulfurization plants should eliminate 95% of the sulfur dioxide produced by the generating units to which they are attached. In the past, abatement efforts have focused on sulfur dioxide. However, with the addition of the desulfurization plants and the expansion of Mae Moh's capacity, nitrogen oxides produced by Mae Moh's generation of electricity will become an increasingly important problem. This paper examines the tradeoff, and how climate affects it, between concentrations of sulfur dioxide and nitrogen oxides just prior to the addition of the desulfurization plants. Mae Moh can use knowledge of this tradeoff in its efforts to minimize the environmental damage from generating electricity.

Full-scale co-firing of straw and coal

Co-firing of biofuels and coal in power plants is considered by the Danish utilities as a potential tool in reducing CO 2 emissions. To test this, full-scale measurements were carried out for 1 week on a 250 MW e pulverized coal fired unit using 10–20% straw (thermal basis). With an increased fraction of straw in the fuel, a net decrease in NO x and SO 2 emissions was measured. The SO 2 emission decreased partly due to the lower sulfur content of the fuel per MJ, but also due to higher sulfur retention in the ash. The NO emission decreased solely due to lower conversion of fuel-N. An increased fraction of straw in the fuel blend resulted in a higher potassium content, but no significant increase in slagging or fouling was observed. Only small amounts of deposit at the lower part of the radiant superheater and little slagging at the furnace walls were observed as a result of co-firing straw and coal. No significant effects on the performance of the desulfurization plant were detected, which may be due to the short test period, probably not allowing the desulfurization process to reach steady-state operation.

96/03288 - Operation results of the first commercial dry desulfurization plant in Hokkaido Electric Power Co.

96/03288 - Operation results of the first commercial dry desulfurization plant in Hokkaido Electric Power Co.

Mechanism for the Formation of Elemental Sulfur from Aqueous Sulfide in Chemical and Microbiological Desulfurization Processes

A detailed reaction mechanism is proposed for the formation of crystalline elemental sulfur from aqueous sulfide by oxidation with transition-metal ions like VV, FeIII, CuII, etc. The first step is the formation of HS• radicals by one-electron oxidation of HS- ions. These radicals exist at pH values near 7 mainly as S•-. Their spontaneous decay results in the formation of the disulfide ion S22-. The further oxidation of disulfide either by S•- radicals or by the transition-metal ions yields higher polysulfide ions from which the homocyclic sulfur molecules S6, S7, and S8 are formed. In water these hydrophobic molecules form clusters which grow to droplets of liquid sulfur (sulfur sol). Depending on the composition of the aqueous phase, crystallization of the liquid sulfur as either α- or β-S8 is rapid or delayed. Surfactants delay this solidification, while certain cations promote it. All these reactions are proposed to take place in desulfurization plants working by the Stretford, Sulfolin, Lo-Cat, SulFe...

96/01034 Simulation model of wet flue gas desulfurization plant

The homogeneous catalytic removal of NO and SO2 with the hexamminecoblt(II) (Co(NH3)62+) solution is a novel alternative to comply with the environmental emission standards. The mass transfer and kinetics of the absorption of NO and SO2 into the aqueous Co(NH3)62+ solutions have been investigated in a double-stirred reactor. The experimental results indicate that the gas–liquid reaction between NO and Co(NH3)62+ with 5.2% oxygen coexisting in the gas phase becomes gas film controlling as Co(NH3)62+ concentration exceeds 0.03 mol l−1 when there is 1600 ppm SO2 in the gas phase. NO absorption rate is proportional to its inlet concentration. Higher SO2 concentration in the gas phase reduces the NO absorption rate into the Co(NH3)62+ solution. The NO absorption rate decreases with temperature as it is above 34 °C and the disadvantage of temperature is smaller in the presence of SO2 than in the absence of SO2. Oxygen in the gas phase is of benefit to the NO absorption. A high oxygen partial pressure is more beneficial to the combined removal of NO and SO2 with the Co(NH3)62+ solution. The NO absorption rate increases with pH of the Co(NH3)62+ solution. A high pH is especially favorable to the combined removal of NO and SO2. A kinetic equation for NO absorption under gas film controlling at 50 °C has been obtained as

ALLEGHENY LUDLUM AL276

Abstract Allegheny Ludlum AL276 is widely used in the most severe environments found in chemical plants and in power plant desulfurization systems. The high molybdenum level with tungsten gives excellent pitting and crevice corrosion resistance. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on low and high temperature performance, and corrosion resistance as well as forming, heat treating, joining, and surface treatment. Filing Code: Ni-497. Producer or source: Allegheny Ludlum Corporation.