Lime Pellets Research Articles

Coal fly ash-bound limestone-derived sorbent pellets for high-temperature CO2 capture

Poor CO2 capture stability and serious elutriation are the issues commonly occur when limestone circulating in the fluidized bed-based Calcium Looping (CaL) system. Hence, three types of coal fly ash-bound (CFA-bound) limestone-derived sorbents were synthesized via mixing the limestone, calcined lime and hydrated lime with coal fly ash, respectively. The generated ternary Ca-Al-O and Ca-Si-O phases offer structural stability for CFA-bound limestone-derived sorbents and improve their cyclic CO2 capture performance. Moreover, extrusion-spheronization method was adopted to produce CFA-bound limestone and hydrated lime sorbent pellets to synergistically enhance cyclic CO2 capture capability and mechanical properties. It is found that hydrated lime is superior to limestone as the calcium precursor to prepare CaO-based sorbent pellets due to its desirable pore structure and high binding force. Therefore, the CFA-bound hydrated lime pellets containing 15 wt % of fly ash (HL/CFA15-P) exhibits a high carbonation conversion of 40 % after 17 cycles, which is nearly 1.4 times that of limestone pellets. The discrepancy on carbonation conversion between the two sorbent pellets is enlarged to ∼1.6 times after 100 cycles, which is calculated using a semi-empirical equation. Moreover, HL/CFA15-P exhibits outstanding mechanical property, whose compressive strength reaches 6±1.7 MPa, which is comparable to the cement-bound CaO-based sorbent pellets.

Isothermal Hydrogen Reduction of a Lime-Added Bauxite Residue Agglomerate at Elevated Temperatures for Iron and Alumina Recovery.

The hydrogen reduction of bauxite residue lime pellets at elevated temperatures was carried out to recover iron and alumina from the bauxite residue in a new process route. Prior to the H2 reduction, oxide pellets were initially prepared via the mixing of an industrial bauxite residue with fine calcite powder followed by calcination and high-temperature sintering. The chemical, compositional, and microstructural properties of both oxide and reduced pellets were studied by advanced characterization techniques. It was found that iron in the oxide pellets is mainly in the form of brownmillerite, and calcium–iron–titanate phases, while upon reduction they are converted to wüstite and shulamitite intermediate phases and further to metallic iron. Moreover, it was found that the reduction at lower temperature of 1000 °C is faster than that at higher temperatures of 1100 °C and 1200 °C. The slower rate and extent of reduction at the higher temperatures is attributed to the porosity loss and reduction mechanism change to a diffusion-controlled process step. In addition, it was found that Al-containing phases in the raw materials are converted mainly to gehlenite in sintered pellets and further to the leachable mayenite phase. The alkaline leaching of selected reduced pellets by a sodium carbonate solution yielded up to 87% Al recovery into the solution, while the metallic iron was not affected.

Rancang Bangun Alat Purifikasi Biogas Water Scrubber Berbasis Mikrokontroler

Biogas is one of the potential renewable energies to be developed in Indonesia. Biogas contains CH 4 as the primary element, besides containing impurities such as H 2 S and CO 2 . The presence of these gases can reduce the quality of biogas and can cause corrosion in equipment. Therefore, it is necessary to purify the gas content, one of them by using a water scrubber. Purification of CO 2 and H 2 S gas levels by using a water scrubber is a physical purification. Purification can also be done chemically, one of them by using CaO. In this research, the media used to make biogas were water hyacinth, cow dung and vegetables, while the media for purification used wood sawdust pellets, quicklime pellets (CaO) and mixed lime and wood lime pellets. The purification process was divided into 3 experiments, the best result was the third experiment with the percentage of biogas production by 15 kg of vegetables with 7.5 kg of cow dung and 15 liters of water, and adding EM-4 by 5%. The results showed the greatest reduction in CO 2 gas with a water scrubber media of 54% while the largest H 2 S gas value with a water scrubber media with CaO and sawdust by 66%.

The effect of sodium alginate, lignosulfonate and bentonite binders on agglomeration performance and mechanical strength of micro-fine agricultural lime pellets

Agricultural lime (crushed limestone) is often applied to acidic soils as the release of carbonate ions neutralize acid forming compounds, such as those added during fertilizer addition. Agglomerated micro-fine limestone is an attractive alternative to powdered limestone, mitigating product losses as a result of windy conditions during application. This article examines the production of agglomerates using sodium alginate, lignosulfonate and bentonite binders for micro-fine CaCO3 powder. Central composite design was used to determine the optimal (i) amount of liquid, (ii) concentration of binder added to maximize the yield of agglomerates of 2–5.6 mm in diameter. Thereafter, four mechanical strength tests were carried out on the agglomerates, where strength was compared dependent on the binder and concentration thereof. The results show that lignosulfonate agglomerates performed the worst of the three binders, whereas agglomerates of >3 g/kg sodium alginate and 70 g/kg bentonite were acceptable in strength. While sodium alginate is a more expensive binder per gram, its high strength at relatively low levels may recommend its use industrially, contingent on economic modeling. This article successfully demonstrated the varying mechanical strengths of various limestone binders, which may assist with the development of novel soil amendment products.

A simple method to determine mineralization of 14C‐labeled compounds in soil

Degradation of organic compounds in soil is often determined by measuring the decrease of the parent compound and analyzing the occurrence of its metabolites. However, determining carbon species as end products of parent compound dissipation requires using labeled materials that allow more accurate determination of the environmental fate of the compound of interest. The current conventional closed system widely used to monitor degradation of (14) C-labeled compounds in soil is complex and expensive and requires a specialized apparatus and facility. In the present study, the authors describe a simple system that facilitates measurement of mineralization of (14) C-labeled compounds applied to soil samples. In the system, soda lime pellets to trap mineralized (14) C-carbon species, including carbon dioxide, were placed in a cup, which was then inserted above the treated soil sample in a tube. Mineralization of [(14) C]2,4-D applied to soil samples in the simple system was compared with that in the conventional system. The simple system provided an equivalent detection of (14) C-carbon species mineralized from the parent compound. The results demonstrate that this cost- and space-effective simple system is suitable for examining degradation and mineralization of (14) C-labeled compounds in soil and could potentially be used to investigate their mineralization in other biological matrices.

Correcting for [formula omitted] interference in soil radon flux measurements

In the present paper the interference of high CO 2 concentration in soil radon flux measurement using a solid state silicon detector is discussed. A possible correction, making use of a chemical trap consisting of soda lime pellets, is successfully experimented at Cava dei Selci site (Roma, Italy). The interference is likely due to neutralization processes of Po 218 ions in the CO 2 dominant atmosphere occurring in the chamber of radon monitor and resulting in a reduced efficiency in electrostatic collection on the surface of the solid state detector.

Hot Defluorination of Reducing Gases with Lime Pellets

In IGCC and MCFC power generation systems the coal gas has to be purified from dust and deleterious gaseous species. Hot gas cleaning processes have advantages compared to conventional wet cleaning technologies. Losses of energy occurring during cooling and reheating of the gas can be avoided, and there is no formation of a wet slurry. In the present study the defluorination of reducing gases with dry absorbers such as calcium carbonate (CaCO3) and calcium oxide (CaO) has been investigated in the temperature range 300−700 °C. Two types of experiments were carried out to clarify the reaction kinetics: thermogravimetric experiments on single (or a few) pellets in which the weight change of the absorber due to its conversion to calcium fluoride was determined, and gas cleaning experiments using a laboratory scale fixed bed reactor in which the off-gas was analyzed. The results indicate that H2−H2O−HF and CO−H2−CO2−H2O−HF gas mixtures can be defluorinated both with CaO and with CaCO3. The calcium fluoride (CaF2) forms as a shell around the unreacted core of calcium carbonate of the pellet, and the reaction rate is mainly controlled by gaseous pore diffusion. This is so also with respect to calcium oxide at high temperatures (500 °C). But at low temperatures (300 °C) the reaction occurs within the bulk of the pellet.

Coal desulfurization by mild pyrolysis in a dual-auger coal feeder

A dual-screw coal feeder reactor was constructed and tested for desulfurization of coal. The reactor consists of two concentric screw tubes, the inner tube acting as a coal pyrolyzer and the outer tube acting as a desulfurizer with hot calcined lime (CaO) pellets or other renewable sorbent pellets. The experimental results showed that under mild pyrolysis conditions, the devolatilization and the desulfurization processes of Ohio #8 coal could be represented by a pseudo first-order reaction model. Up to 33.2% of the total sulfur, which includes almost all the organic sulfur, was removed at a temperature of 475°C and a residence time of 6 min using a coal particle size of 4–35 mesh. The activation energies for the devolatilization and the desulfurization processes were estimated to be 170,021 kJ/kg mol and 78,732 kJ/kg mol, respectively. The H 2S concentration in the pyrolyzed gas was reduced from 4% to an undetectable level in the outer tube desulfurizer indicating a high sulfur removal efficiency of CaO pellets in the dual-screw feeder reactor.

Hydration Kinetics of Recarbonized Lime.

The hydration rate of partially recarbonized lime pellets has been studied by employing a single pellet into a stream of air/vapor water mixtures using a computer aided thermo-gravimetric technique. The hydration reaction takes place on a sharp, well defined interface between the product layer and the unreacted core. It has been found that the hydration mechanism consists in two steps. The first observes very slow hydration rates and the second higher ones. During the first step the water molecules diffuse through a close porous carbonate structure and the second one begins when these molecules reach the calcium oxide-calcium carbonate interface to continue through the lime core. A theoretical model was derived to explain the results of this study. The experimental results were acceptably well predicted with calculations performed using this model. On the other hand, it was found also that the higher is the lime calcination temperature the thinner is the recarbonized layer formed even under high CO 2 partial pressures. However, these thin layers are more effective to increase the hydration resistance of lime pellets than thicker ones. This is an important experimental finding since it indicates that low recarbonization extents are good enough to increase the hydration resistance of steelmaking lime without impairing its quality.

96/01215 Desulfurization of coal in hydrocarbons

A dual-screw coal feeder reactor was constructed and tested for desulfurization of coal. The reactor consists of two concentric screw tubes, the inner tube acting as a coal pyrolyzer and the outer tube acting as a desulfurizer with hot calcined lime (CaO) pellets or other renewable sorbent pellets. The experimental results showed that under mild pyrolysis conditions, the devolatilization and the desulfurization processes of Ohio #8 coal could be represented by a pseudo first-order reaction model. Up to 33.2% of the total sulfur, which includes almost all the organic sulfur, was removed at a temperature of 475°C and a residence time of 6 min using a coal particle size of 4–35 mesh. The activation energies for the devolatilization and the desulfurization processes were estimated to be 170,021 kJ/kg mol and 78,732 kJ/kg mol, respectively. The H2S concentration in the pyrolyzed gas was reduced from 4% to an undetectable level in the outer tube desulfurizer indicating a high sulfur removal efficiency of CaO pellets in the dual-screw feeder reactor.

KINETICS OF CALCIUM OXIDE CHLORINATION AND PORE CLOSURE MODELS

The chlorination of cylindrical lime pellets was studied using thermogravimetric analysis by varying the chlorine concentration, pellet size and temperature. It was determined that the reaction is first order with respect to Cl2. The intrinsic activation energy, E1, is estimated to be 8.09 kcal/gmol in the temperature range of 333°C to 472°C. A two-dimensional expanding grain model that accounts for bulk flow was developed and successfully applied to the lime chlorination system. The effect of varying the chlorine concentration, pellet size, and temperature can be explained in terms of the model. In addition, the modeling results seem to imply that even for a system with solid product expansion, the surface porosity remains finite after the maximum conversion is obtained. Operated for the US. Department of Energy by Iowa State University under Contract No. W-7405-Eng-82. This research was supported by the Assistant Secretary for Chemical Sciences. Office of Basic Energy Sciences. WPAS-KC-03-02.

University Block 31 Field Study: Part 1 - Middle Devonian Reservoir History Match

University Block 31 Field Study: Part 1 - Middle Devonian Reservoir Part 1 - Middle Devonian Reservoir History Match This paper describes the use of a compositional reservoir simulator to match a suite of PVT experiments and laboratory tube displacements for the high-pressure, gas-drive process. A history match of 30 years' performance of more than 100 wells, including both lean- and flue-gas injection, is presented. presented. Introduction Performance of the Block 31 Middle Devonian reservoir Performance of the Block 31 Middle Devonian reservoir was analyzed. This study provided the field engineers with a working tool for evaluating future reservoir performance. This study also provided gas-plant performance. This study also provided gas-plant personnel a method for predicting future gas-plant production personnel a method for predicting future gas-plant production and fuel availability.A compositional simulator' was used in this study. With this type of simulator, compositional effects were accounted for and the gas-plant performance was simulated. Previous studies of this reservoir using black-oil simulators gave poor history matches. Black-oil models cannot calculate the gas-plant performance needed to make long-term projections. By modeling the entire Middle Devonian reservoir, the possibility of incorrect no-flow boundaries that plagued previous pattern area analysis of this field was eliminated. pattern area analysis of this field was eliminated. The steps required to develop the history match of the reservoir performance are described here. This includes initialization of the model, testing of the compositional simulator's ability to mimic the high-pressure, gas-drive displacement process, and the philosophy used to obtain an acceptable history match. Part 2 describes the model modifications required to expedite the projection computations and three projections of future field performance and gas-plant operations. performance and gas-plant operations. Reservoir Description The Block 31 (Devonian) Unit is located 9 miles (14.5 km) northwest of Crane, TX. The structure on top of the Devonian is a northeast-southwest trending anticline (Fig. 1) bounded on the south and southeast by normal faults. Productive area is 7,840 acres (31 × 10 M). The Devonian interval has three reservoirs: Upper, Middle, and Lower (Fig. 2). The major reservoir is the Middle at 8,500 ft (2590 m) [- 6,000 ft (- 1828 m) subsea] and its net pay averages 170 ft (51.8 m). The Devonian pay consists of 65% tripolitic chert and 20% fine crystalline, sucrosic limestone. The remainder is variable amounts of lime mud, skeletal material, pellets, and quartz silt. The porosity is intercrystalline and averages 15%. The permeability averages 1 md, but is 8' to 10 times this amount in the hairline fractures present in the reservoir. Table 1 lists pertinent reservoir parameters. parameters. History ARCO Oil and Gas Co. discovered the Block 31 Field in 1945. Partial pressure maintenance was begun in 1949 by reinjecting produced gas. In 1952, the field was unitized for full pressure maintenance. Other companies in the unit are Phillips Petroleum Co., Champlin Petroleum Co., and Continental Oil Co. Petroleum Co., and Continental Oil Co. Beginning in 1955, the high-pressure, gas-drive process was used in the Block 31 Middle Devonian process was used in the Block 31 Middle Devonian reservoir. P. 962