In this study, the commercial chemical process simulator, PRO/II W V8.1.1, is implemented to perform the simulation of a coal gasification-based co-production system, of which the feedstock is kaltim prima coal from Indonesia, and the products are electricity and dimethyl ether (DME). There are five major blocks in the multi-product plant, i.e. air separation unit (ASU), gasification unit, gas clean-up unit, combined-cycle, and DME synthetic unit. ASU utilizes cryogenic air separation process, which provides oxygen with 95 mol% purity to the gasification unit and nitrogen to the combinedcycle. General Electric technologies are employed in the study, i.e. quench-type slurry-fed gasifier for the former and 7FB-series turboset for the latter. The clean-up unit includes dry solids removal, syngas scrubbing, sulfur compounds removal, and sulfur recovery processes, which are implemented to deliver clean syngas to further processes and elemental sulfur from H 2 S. The clean syngas is divided into two equal streams to generate electricity and produce DME, simultaneously. The results show that the gross and net electrical power outputs are 371.6 and 275.1 MW, respectively; furthermore, the yield of DME is 51.78 mt/h. In summary, the net efficiency of the coal gasification-based multi-product plant is 46.1% (HHV), which is higher than the counterpart of typical integrated gasification combined-cycle plants by over four percentage points.

No abstract

The chloridization rates of sodium hydrogen carbonate calcines were determined using both a differential fixed-bed reactor and an integral fixed-bed, flow-through reactor at ambient pressure and a temperature of 500 °C. In the course of the reaction with hydrogen chloride gas, monoclinic or hexagonal Na2CO3 was transformed into cubic NaCl. The expansion of the volume of the solid phase, because of the reaction, was described by means of a simple structural model. The reacted solids remained quite porous (∼29%), having decreased from an initial porosity of 45%. Up to advanced stages of the reaction, the rate-decaying behavior of the chloridization reaction can be approximated by first-order kinetics as a function of either the solids conversion or the elapsed time of reaction. The reaction between hydrogen chloride gas and the Na2CO3-based sorbents is rapid, and a high degree of sorbent utilization can be attained. The unsteady-state sorption of hydrogen chloride gas in a column packed with reactant solids can be described by a pair of partial differential equations, and their analytical, closed-form solution is presented in terms of three dimensionless variables. Unsteady-state experimental runs were carried out in a small integral fixed-bed reactor (14-mm i.d.) with spherical alumina particles having an average diameter of 1.5 mm, impregnated with NaHCO3 and packed to a depth of 6.5 cm. The effective reaction rate constants inferred from the experimental breakthrough curves in accordance with the model were found to be in reasonable agreement with those determined from the experiments executed in the differential mode of reaction. The presented, tractable expressions can readily serve as a rational basis for the conceptual design and effective operation of packed-bed reactors for the deep removal of hydrogen chloride gas from hot producer gas.

Various means for enhancing hydrogen content in the syngas from gasification of solid biomass in fluidized-bed reactors were investigated in this study. Steam or oxygen-rich gas can be supplied as gasification medium, to improve the syngas characteristics. Alternatively, a so-called “indirect gasification technology” realizes the thermo-chemical conversion processes in dual reactors, respectively, for combustion and gasification, where gaseous streams in between are separated while solid materials are circulated through. Hence, with air as oxidant for combustion this system features the advantage of producing nearly nitrogen-free syngas. Baseline experiments were firstly carried out to identify performance features; then, parametric studies were conducted and positive trends for enhancing hydrogen generation via biomass gasification were revealed. Moreover, hydrodynamic characteristics in dual reactors were comprehensively envisaged in the cold-flow models to facilitate subsequent investigation into thermo-chemical processes. The experimental results indicated that the circulation mass of the bed material driven by the operating air exceeded the design value, which gave a comfortable safety factor of the engineering design. In addition, the average pressure distribution measured by the cyclic operation of the system was similar to that of the published literature. Based on the experimental results of the cold model, the suggestions of the operating tests in the hot model were addressed. Further efforts will be pursued to establish databases for clean energy and carbon abatement technologies.

In this study, solid biomass is gasified in fluidized-bed reactors, to investigate the effect of various means on syngas composition, especially for enhancing hydrogen content in the production gas. Conventionally, air is supplied to the reactor as gasification medium, which inevitably results in a high nitrogen content in the syngas. Alternatively, steam or oxygen-rich gas can be supplied to improve the syngas characteristics. On the other hand, a so-called “indirect gasification technology” realizes the whole conversion processes in dual reactors, for combustion and gasification, respectively; moreover, solid materials are circulated through two reactors, while gaseous streams in between are separated from each other. Hence, this system features the advantage of producing near nitrogen-free syngas in the gasifier, with air as oxidant in the combustor. Baseline experiments with various operating parameters, including air equivalence ratio (ER) and temperature, were firstly performed in a 30 kWth bubbling fluidized-bed gasifier; then, trial tests were conducted with the aforementioned operational and constructional factors. The preliminary test data show positive trends for the enhancement of hydrogen generation via biomass gasification. Further efforts will be pursued to establish a data base, which would be beneficial to extensive researches on clean energy and carbon abatement technologies.