Simultaneous reductive and oxidative decomposition of calcium sulfate in the same fluidized bed

Calcium sulfate is decomposed to CaO and SO2 by high temperature treatment in a fluidized bed wherein reductive and oxidative conditions are simultaneously maintained. A highly reducing gas is formed in the lower portion of the bed from partial combustion of the fuel in admixture with the primary fluidizing air. The quantity of the primary fluidizing air is limited so that the reducing conditions in the lower zone converts the CaSO4 to a mixture of CaO and CaS. Secondary air is introduced at a higher level in the bed to create an oxidizing zone in the upper portion of the bed above the reducing zone capable of converting CaS to CaO. The concurrent use of such reducing and oxidizing zones permits reducing conditions to be maintained which favor a high rate of decomposition even though these conditions favor the formation of CaS as well as CaO. The undesirable CaS, which would otherwise be discharged with the CaO product is eliminated by circulation of the fluidized particles through the oxidizing zone. Further, the heat of the exothermic reactions is conserved and utilized for promoting the endothermic reactions, both types of reactions occuring simultaneously while the rapid fluidized circulation of solids maintains a relatively uniform temperature throughout the bed

Process for producing low-ash, low-sulfur coal

Pyritic sulfur, organic sulfur, and ash-forming minerals are removed from coal by a 2-stage alkaline treatment, using sodium carbonate or bicarbonate as the reagent. The first stage is an alkaline oxidation at moderate temperatures (130°-150° C.), and the second stage is a non-oxidizing alkaline treatment at a much higher temperature (250°-330° C.). The alkaline treated coal is extracted with an aqueous mineral acid, preferably hot aqueous sulfuric acid (H2 SO4) followed by washing with hot water. The resulting low-ash, low-sulfur coal can be used as a fuel in oil-firing boilers, and for similar applications where minimal-ash content is a basic requirement

Gas distribution system for a two-zone fluidized bed reactor

The present invention provides an improved method for constructing a gas distribution system which creates two distinct reaction zones within the same fluidized bed. The invention provides for the distribution of one type of gas at the bottom of the fluidized bed and a second type of gas at a higher level in the fluidized bed. The system is constructed of a plurality of modular units constructed entirely of refractory materials. The modules are fitted and linked together to form a grid, the size of which can be varied to accommodate different reactor sizes

Process for high temperature gaseous reduction of calcium sulfate

Calcium sulfate is subjected to gaseous reduction at a high temperature to obtain an SO2 containing gas product and a CaO solid product. The reduction is carried out in a fluidized reaction bed by flowing proportioned air and natural gas into and through the bed to fluidize the finely divided calcium sulfate and to heat to reaction temperatures. The natural gas is only partially burned within the bed, thereby also producing reducing quantities of CO and H2. In a preferred embodiment, the calcium sulfate feed is preheated by direct contact with the gas product to recover part of the heat therefrom, and the gas product of reduced heat content is then subjected to indirect countercurrent heat exchange with the air being supplied to the reaction bed

Simplified Design Model for an Ion Exclusion Column

A simplified design model for a chromatographic ion exclusion column is developed in which the flxed bed of resin is dividl~d into a number of perfectly mixed equilibrium stages and the liquid Aow rate is constant. The model is represented by the following dimensionless differential equation which results from the combination of a material balance about the rth stage and a second-degree phase equilibrium relationship: ( 1 /h}(f, - 1/;,-1l + K (clf,/dT) + M\u3e/;, (df,/dT) = 0, where K and Mare dimensionless groups while 1 /his the number of equilibrium stages. 1/; and T are dimensionless concentration and time, respectively. The numerical solutions of this E~quation for single, square wave inputs are presented for different values of the dimension· less groups, feed volumes, and number of stages. The resulting calculated elution curves and experimentally determined curves are compared. Design applications are discussed

Production of Hydrogen from Coal Char in an Electrofluid Reactor

A potential industrial process for producing a hydrogen-rich synthesis gas by reacting coal char and steam in an electrofluid reactor is described. The characteristics of this type of reactor are reviewed, and a reaction model which appears to fit experimental results is proposed. Product gas compositions and energy requirements predicted by the model for the gasification process are presented for various possible operating conditions. The present state of development of the reaction system and foreseeable problems which must be worked out are reviewed. In addition, the adaptation of the process to the production of various products such as hydrogen, methane, and methanol is discussed

Gas Chromatography of C1 to C4 Nitroparaffins

simple, fast, and accurate method for gas-liquid partition chromatographic analysis for the products of a pilot plant designed for the vapor phase nitration of commercial butanes has been developed. Errors in reproducibility were less than +/-0.6% with errors in accuracy less than +/-0.5%. The substrates used for this separation were Apiezon T grease, Lubriseal stopcock grease, and Wemco C transformer oil

A Comparison of Coal Beneficiation Methods

Although iron pyrites and other minerals are removed from coal on an industrial scale almost exclusively by gravity separation methods at the present time, other beneficiation methods are coming into use. Among the developing methods, froth flotation (1,2,3) is the foremost, although the oil agglomeration method (4,5,6) is also promising. Both of these methods take advantage of the difference in surface properties of coal and inorganic mineral particles suspended in water to effect a separation. In the first method the hydrophobic coal particles are removed from the hydrophilic mineral particles by selective attachment to a mass of air bubbles, while in the second method the coal particles are selectively coated and agglomerated by fuel oil and then recovered by screening. While gravity separation methods are well suited for removing coarse mineral particles from coal, they are generally ineffective for removing microscopic particles. On the other hand, both the froth flotation

A Reusable Calcium-Based Sorbent for Desulfurizing Hot Coal Gas

There is a continuing need for an inexpensive, regenerable sorbent for desulfurizing hot coal gas. Such a material is needed especially for advanced power generating systems including integrated gasification combined-cycle (IGCC) systems and other systems which employ various topping cycles. Maximum power generation efficiency can be achieved by cleaning the gas at nearly gasifier outlet temperatures which can range up to 1200 K or more

Regeneration of Sulfided Calcium-Based Sorbents by a Cyclic Process

A unique process for regenerating calcium-based sorbents which are in the form of calcium sulfide was demonstrated by employing thermogravimetric analysis (TGA). The process converts calcium sulfide to calcium oxide by subjecting particles of the material to repeated cycles of oxidation and reduction at temperatures between 950 and 1100 °C. During each cycle a small portion of material is first converted to calcium sulfate by oxidation and then to calcium oxide by reduction. Air can be used for oxidation and any of the following gases can be used for reduction:  30 mol % CO, 5 mol % CH4, or 2 mol % C3H8. Repeated sulfidation and regeneration of typical calcium-based sorbents seems to enhance the reactivity of the materials. However, incorporation of iron oxide or flyash containing an appreciable concentration of iron oxide in the sorbent has a deleterious effect