Uncertainty and disturbance estimator-based model predictive control for wet flue gas desulphurization system

Wet flue gas desulphurization technology is widely used in the industrial process for its capability of efficient pollution removal.The desulphurization control system,however,is subjected to complex reaction mechanisms and severe disturbances,which make for it difficult to achieve certain practically relevant control goals including emission and economic performances as well as system robustness.To address these challenges,a new robust control scheme based on uncertainty and disturbance estimator(UDE)and model predictive control(MPC)is proposed in this paper.The UDE is used to estimate and dynamically compensate acting disturbances,whereas MPC is deployed for optimal feedback regulation of the resultant dynamics.By viewing the system nonlinearities and unknown dynamics as disturbances,the proposed control framework allows to locally treat the considered nonlinear plant as a linear one.The obtained simulation results confirm that the utilization of UDE makes the tracking error negligibly small,even in the presence of unmodeled dynamics.In the conducted comparison study,the introduced control scheme outperforms both the standard MPC and PID(proportional-integral-derivative)control strategies in terms of transient performance and robustness.Furthermore,the results reveal that a lowpass-filter time constant has a significant effect on the robustness and the convergence range of the tracking error.

Multiobjective economic model predictive control using utopia-tracking for the wet flue gas desulphurization system

Efficient control of the desulphurization system is challenging in maximizing the economic objective while reducing the SO_(2) emission concentration. The conventional optimization method is generally based on a hierarchical structure in which the upper optimization layer calculates the steady-state results and the lower control layer is responsible to drive the process to the target point. However, the conventional hierarchical structure does not take the economic performance of the dynamic tracking process into account. To this end, multi-objective economic model predictive control(MOEMPC) is introduced in this paper, which unifies the optimization and control layers in a single stage. The objective functions are formulated in terms of a dynamic horizon and to balance the stability and economic performance. In the MOEMPC scheme, economic performance and SO_(2) emission performance are guaranteed by tracking a set of utopia points during dynamic transitions. The terminal penalty function and stabilizing constraint conditions are designed to ensure the stability of the system. Finally, an optimized control method for the stable operation of the complex desulfurization system has been established. Simulation results demonstrate that MOEMPC is superior over another control strategy in terms of economic performance and emission reduction, especially when the desulphurization system suffers from frequent flue gas disturbances.

Desulfurizer desulphurization kinetics by the injection method

To obtain a better desulphurization effect in hot metal, suitable desulfurizers should be selected first according to thermodynamics. However, the effect of desulphurization is also strongly affected by kinetics. The conditions of different desulfurizers （Mg, CaC2, and lime） penetrating into hot metal, the rising up velocity in iron melt, residence time, and dissolving time are theoretically calculated and analyzed. The results are helpful to select the desulphurization process and equipment and to improve the desulphurization effect.

Lignite oxidative desulphurization Notice 1.Process condition selection

The process of lignite desulphurization via its treatment by an oxidant(air or air–steam mixture)has been studied.The research objective was useful determination of steam application in oxidative lignite desulphurization.It has been proved that the water steam should be included in the oxidant composition to increase the hydrogen sulphide and combustible constituent content in the gases obtained during the processes under research.The impact of factors which affect the reactions between solid(in our case–lignite)and gaseous reagent(oxidant,i.e.air and or air–steam mixture)upon the research process has been investigated,if these reactions occur in the kinetic area.Such factors are linear rate of oxidant movement and coal grain size.The values of oxidant movement linear rate and coal grain size,which the reaction transfer from pyrite sulphur and organic content of lignite from diffusion into kinetic area occurs by,have been determined.Under these‘‘transfer’’conditions,the values of coefficients of oxidant mass transfer(β,m/s)as well as Sherwood criteria and boiling layer differences have been calculated.

Study of oxidative desulphurization process of coal with different metamorphism degrees

The oxidative desulphurization process of coal with different metamorphism degrees treated by an air-steam mixture has been studied.It has been shown that the pyrite present in black coal and anthracite is oxidized with the sulphur dioxide formation,and the process chemical mechanism does not depend on the quality of organic matter.The medium-metamorphized coal,capable of turning into a plastic state and cake in the range of investigated temperatures(350～450 ℃),is desulphurized with the greatest difficulty.The chemical mechanism dealing with the transformations of pyritic sulphur present in brown coal differs from similar processes taking place in black coal and anthracite,because FeS2 is converted with hydrogen sulphide formation at desulphurization.

Desulphurization during VIM Refining Ni-base Superalloy using CaO Crucible

The variation of S content during VIM refining Ni-base superalloy using CaO crucible was studied. It was foundthat the desulphurization process could not be carried out by only using CaO crucible. The role of Al additionto desulphurization was also studied. Combining with the results of XRD and composition analysis of the CaOcrucible, the mechanism of desulphurization was proposed. Thermodynamical calculation about the reaction betweenthe interface of CaO crucible and liquid metal has been discussed. This work indicated that under proper refiningtechnology the S content in the liquid Ni-base alloy could be reduced from 3×10-5 to 2×10-6~4×10-6.

Resource utilization of slag from desulphurization and slag skimming:A comprehensive recycling process of all components

In order to make the slag from desulphurization and slag skimming(SDSS)to be comprehensively recycled and utilized,a combined process of beneficiation and building materials preparation was proposed to recover iron from SDSS,meanwhile to apply the remaining slag tailings as cement admixture.From this process,three iron-rich products were recovered in stages by clean gravity-magnetic separation,slag tailings were left.Slag powder was prepared by ultrafine grinding of slag tailings.The stability,setting time and cement mortar strength of the slag tailings cements(STC)which were mixed with Portland cement and slag powder were studied respectively.The results showed that a proper overall performance still could be obtained at the slag powder content of 30%.Chemical composition analysis,X-ray diffraction(XRD)analysis,metallographic microscope and scanning electron microscope(SEM)analysis were employed to assess the characteristics of the SDSS and the products obtained from the whole process.The results indicated that the three iron-rich products could be used as a raw material for steelmaking and ironmaking and the relatively large amount of calcium silicate(C_(2)S)and tricalcium silicate(C_(3)S)in the slag tailings make the addition of slag powder into the Portland cement feasible.

Research on the use of sintering flue gas desulphurization gypsum as a cement retarder

The characteristics of the desulphurized gypsum produced in the flue gas desulphurization （FGD） process of the Baosteel sintering plant are investigated in this study. According to the technical and quality requirements of gypsum in the cement industry ,the feasibility of using desulphurized gypsum as a cement retarder is also studied. The results show that desulphurized gypsum can be used as a cement retarder instead of natural gypsum.

Vacuum Treatment for Simultaneous Desulphurization and Dephosphorization of Hot Metal and Molten Steel

The vacuum treatment for simultaneous desulphurization and dephosphorization of hot metal and molten steel with pre-melted CaO-based slag was carried out.For pre-treatment of hot metal,both desulphurization and dephosphorization are improved with the increase of CaO in slag,but deteriorated with the increase of CaF2 in slag.The average desulphurization and dephosphorization rate is 68.83 % and 78.46 %,respectively.For molten steel,the substitution of BaO for CaO in slag has minor effect on simultaneous desulphurization and dephosphorization.The desulphurization and dephosphorization rate is higher than 90% and 50% respectively with the lowest final sulfur and phosphorus mass percent being 0.001 2% and 0.010%,respectively.The overall effect of simultaneous desulphurization and dephosphorization of molten steel is better than that of hot metal.

Activation of Rejected Fly Ash Using Flue Gas Desulphurization (FGD) Sludge

Low-grade fly ash (rejected fly ash,rFA),a significant portion of the pulverized fuel ash (PFA) produced from coal-fired power plants and rejected from the ash classifying process,remains unused due to its high carbon content and large particle size (>45μm).But it is thought that the rejected ash may have potential uses in chemical stabilization/solidification (S/S) processes which need relatively lower strengths and a lower chemical reactivity.Flue Gas Desulphurisation (FGD) sludge is a by-product of air pollution control equipment in coal fired power plants whose chemical composition is mainly gypsum.As there is no effective usage of both of these two materials,it is of interest to research on the possible activation of rFA using FGD.This paper presents experimental results of a study on the properties of rFA activated by the FGD in rFA-cement pastes.Different percentages of FGD were added into the mix to study the effects of the FGD on the reaction of the rFA blended cement pastes.The results show that FGD takes effect as an activator only at late curing ages.Adding Ca(OH) 2 enhances the effect of FGD on activating the hydration of rFA.Also,10% FGD by weight of rFA is the optimal addition in the rFA-cement pastes.The results of the compressive strength measurements correlate well with the porosity results.

Lignite oxidative desulphurization: notice 3-process technological aspects and application of products

The study reviews the process of oxidative desulphurization of high-sulphur Ukrainian lignite, which was performed by coal treatment using an air or air-steam mixture. In the process. sulphur-free fuel and tar from the decomposition of coal organic matter was obtained. Hence, the sulphur in the coal was converted inlo hydrogen sulphide. The coal desulphurization process is critical to power generatio n. power generation and technology, and tech no logy field of application. The coal desulphurization process ensures the maximum recovery of the highest content of sulphur and hydrogen sulphide (H2S) in desulphurized gases at minimal energy costs. The process also enhances the maximum decomposition of tar and sulphur recovery (> 50%) during coal power generation. Based on smnniarized field studies, a block schematic diagram coupled with heat and material balances of the process was developed for the calculations. The application of the tech no logy at the first stage of coal combustion in thermal power plants will en able the utilizatio n of over 50% of recovered coal sulphur in the form of concentrated H2S or commercial elemental sulphur. This will, nevertheless, allow for a reduction of sulphur oxide pollution in the environment by at least 53%-56%. It has been suggested that the product of thermal decomposition of coal organic matter (tar) can be used as a componenl of fumace fuel oil or as a plasticizer of petroleum-based road bitumen.

KINETICS OF DESULPHURIZATION IN PERMANENT CONTACT OF SLAG AND STEEL

The curve of % S vs reaction time is described quantitatively based on the electrochemical model directly deduced from the principle of electrochemistry as well as the given method for calculating the initial oxygen potential along slag/steel interface.The calculated data is in good agreement with the experimental results. During desulphurization,both L_s~* and L_s,the sulphur partition along the interface and that in the bulk,go up in association with the descending of oxygen potential along interface. The plot of L_s~* against reaction time follows a parabolic curve,while that of L_s is of hyperbola type.Correspondingly,on curves of driving force parameter vs reaction tone,either calculated or experimental,a hump occurs.

Deep Desulphurization and DeNO_X in Circulating Fluidized Bed Boiler

With the revision of emission standards, deep desulphurization and DeNO X is needed in circulating fluidized bed (CFB) boilers. The operation of the first set of 300-MW CFB boiler plus limestone/gypsum wet flue gas desulphurization (FGD) system in the world shows that deep desulphurization and DeNO X of CFB boilers has higher SO2 removal efficiency at a lower Ca/S ratio compared with traditional inner desulphurization mode. It can meet the increasingly rigid emission standards, and is suitable for more fuels. Deep desulphurization and DeNO X can also achieve a highly-efficient high-temperature CFB boiler that can not only achieve inner desulphurization and low NO X emission, but benefits low-grade, high sulfur content fuels as well. Research of deep desulphurization and DeNO X will be a developing direction for CFB boilers.

Adsorption of Pb^2+and Cu^2+with Unburned Desulphurization Slag Modified Nickel Slag

Desulphurization slag modified nickel slag adsorbent was prepared by unburned forming technology. The structure of the sample was characterized by BET,XRD,IR,SEM and EDAX. The adsorption performance of Pb^2＋ and Cu^2＋ onto the resultant adsorbent from aqueous solution was studied. Results indicated that the adsorbent possesses a network pore structure formed by the AFt and C–S–H through cross lapping; the adsorbent contains a large number of Si–OH and Al–OH functional groups. The presence of functional groups not only provides abundant adsorption sites for Pb^2＋ and Cu^2＋,but also improves the adsorption performance of Pb^2＋ and Cu^2＋ from waste water through the complexation of heavy metal ions. The result of specific surface area analysis showed that the adsorbent sample possesses mesoporous structure and the BET specific surface area is 27.15 m^2/g. The solution p H values for the adsorption of Pb^2＋ and Cu^2＋ were optimized to be 6 and 5.5,respectively. The adsorption capacities of Pb^2＋ and Cu^2＋ gradually increase,whereas the removal rates of the two metal ions decrease with increasing the initial concentration of simulated solution. The resultant adsorbent gives a higher adsorption capacity for Cu^2＋ than for Pb^2＋ in the single ion solution. However,it shows preferential adsorption of Pb^2＋ rather than that of Cu^2＋. Meanwhile,results of recyclability indicate the remarkable regeneration capacity,re-adsorption ability and reusability performance of the adsorbent sample.

Study on the Mechanism of Ultrasonically Enhanced Flotation Desulphurization

The mechanism of ultrasonic action and the influence of ultrasonic treatment on the changfs or particle size, dissolved oxygen, pH and the feasibility of flotation desul phurization with ultrasonic enhancement are studied. A new means of ultrasonic treatment for slurry is put forward. The test results indicate that by employing this means and an approprlate floatation technology and pyrite-depressed method, the optimum effect of rlotation desul phurization can be achieved.

The Ionization Theory of Desulphurization of the Panzhihua Blast Furnace Slag

With the proper choice of the ion species present in the Panzhihua blast furnace slag, the sulphur partition ratio was calculated based on the ionization theory of the slag. It can be concluded that TiO_2 reacts as an acidtc oxide and the Panzhihua ore or concentrate cannot be treated as a semi-self-fluxing ore.

Development and applications of Baosteel sintering flue gas desulphurization technology

The research background and technical features of Baosteel sintering flue gas desulphurization （ FGD）--swirl- jet-absorbing wet limestone-gypsum sintering FGD technology, process and equipment are introduced in this paper. Main contents and achievements of the pilot experiment and the engineering practice of Baosteel FGD are analyzed and discussed systematically. Past engineering practice experiences indicate that Baosteel FGD has the following merits： wide applicability to sintering flue gas features, such as frequently changing temperatures, unstable SO2 concentration, intensively fluctuating flow rates ,etc. ,high pollutants removal efficiency ,low investment and energy consumption; stable and reliable operation ,utilizable byproduct （gypsum）, etc. It indicates that Baosteel sintering FGD is of extensive application value for the FGD of large and medium-scaled sintering machines.

Desulphurization Characteristic of Industry Alkaline Wastes during Coal Combustion

The desulphurization characteristics of four sorts of industry alkaline wastes and one sort of limestone were studied by means of flue gas analyzer and the high temperature tube reactor. Pore structure and desulphurization product char-acteristic were investigated respectively by mercury porosimeter and XRD diffraction technology. The reasons why wastes and limestone hold the different desulphurization capability were deeply discussed. The result shows that white clay and carbide slag could capture the release of sulfur at 800-1100℃. Salt slurry and red mud could capture the re-lease of sulfur at first stage at 800-900℃. But when the experimental temperature rises to 1000℃, the sulfur capture abilities of them depress. Pore structures of waste are higher than that of limestone. This makes the sulfation reaction goes further. To sum up, wastes have better sulfur capture ability.

Desulphurization of Transportation Fuels by Per-Formic Acid Oxidant Using MoOx Loaded on ZSM-5 Catalyst

Desulphurization of model and real oil samples was investigated using performic acid as oxidant assisted by air as co-oxidant. The catalysts used were Mo-oxide supported on ZSM-5 zeolite, which was synthesized in the laboratory and characterized by FT-IR, XRD, SEM and SSA analysis. In case of model oil, the optimum condition determined for complete oxidation of all the model compounds including thiophene, DBT and 4,6-DMDBT were;60?C, 60 min, ambient pressure and air flow rate of 100 mL/min. The oxidation reactivity decreased from 4,6-DMDBT to DBT and thiophene, which was found to follow pseudo first order kinetics. The real oil sample used in the study included untreated naphtha (NP), light gas oil (LGO), heavy gas oil (HGO) and Athabasca bitumen (Bit.). In case of NP and LGO the sulfur removal of above 78% was attained whereas in case of HGO and Bit. samples about 60% of desulfurization was achieved.

The Analysis of Using MGGH in Flue Gas Desulphurization (FGD) System in Cement Plant

The paper first introduces the background and the mechanism of secondary pollution from desulfurization in cement plant. Then, take plant A as an example, using MGGH (media gas-gas heater) to control “white smoke”. MGGH uses heat medium water to heat transfer between the original flue gas and the clean flue gas, without additional heat source, and has obvious economic benefits, which is the inevitable development direction of desulfurization reform of cement kiln system in the future.