Purification hydrogen gas

Figure 2.36. Schematic layout of photobiological hydrogen production plant with auxiliary plants for production of modified bacterial strains and for hydrogen gas purification (Serensen, 2004c).

Figure 2.38. Schematic layout of substrate fermentation plant for hydrogen production, with infrastructure for residue collection/recycling and hydrogen gas purification. The blanket hydrogen reactor is similar to those used in biogas plants (Sorensen, 2004c).

Table VII presents the estimated investments. The methanol case investment reflects the same gasifier type as used for the IBG and SNG cases. A conceptual Chem Systems methanol synthesis step is used. EPRI is sponsoring the development of the Chem Systems technology (5 ). The ammonia case investment reflects the same wood gasification concepts, employs pressure swing adsorption for hydrogen gas purification (based on information provided by the Linde Division, Union Carbide Corporation), and uses a conventional high-pressure ammonia synthesis loop.

The various equations presented in the preceding sections have been used to compute the gas phase composition in the CH4-H2 system over the ranges 1-240 atm and 60°-122°K. This system was chosen for study because of its molecular simplicity and its technical importance in hydrogen gas purification. 

Santangelo, J.G., and Chen, G.T., Metal hydrides for hydrogen gas purification, Chemtech, October, 621-623... 

Gas purification processes fall into three categories the removal of gaseous impurities, the removal of particulate impurities, and ultrafine cleaning. The extra expense of the last process is only justified by the nature of the subsequent operations or the need to produce a pure gas stream. Because there are many variables in gas treating, several factors must be considered (/) the types and concentrations of contaminants in the gas (2) the degree of contaminant removal desired (J) the selectivity of acid gas removal required (4) the temperature, pressure, volume, and composition of the gas to be processed (5) the carbon dioxide-to-hydrogen sulfide ratio in the gas and (6) the desirabiUty of sulfur recovery on account of process economics or environmental issues. 

An integrated process for producing chlorine dioxide that can consume chlorine (46) involves the use of hydrochloric acid as the reductant. The spent chlorine dioxide generator Hquor is used as feed for chlorate production, and hydrogen gas from chlorate production is burned with chlorine to produce hydrochloric acid. The principal disadvantage in the integrated hydrochloric acid-based processes is that the chlorine dioxide gas contains Y2 mole of chlorine for each mole of chlorine dioxide produced. A partial purification is achieved by absorption in chilled water in which the solubiHty of chlorine is less than chlorine dioxide however, this product stiU contains 10—15% chlorine on the basis of total chlorine and chlorine dioxide. 

Gas purification or the removal of relatively small amounts of impurities such as CO2, CO, COS, SO2, H2S, NO, and others from air, natural gas, hydrogen for ammonia synthesis, and others... 

A solution of 13.5 g (21 mmol) of diisopinocamphenylborane in 250 mL of hexane is treated at 0 C with 7.1 g (47 mmol) of trifluoromethanesulfonic acid in a dropwise fashion which results in the evolution of hydrogen gas. The mixture is stirred for 3 h at 0 "C and then at r.t. overnight. At OX the reaction proceeds with slow, but steady, hydrogen evolution without problem (an induction period which results in a rapid exotherm in the Mukaiyama procedure has been reported30). After stirring overnight, a small amount of solid material appears. The solvent is evaporated and the residue is used without further purification 99.8% ee. 

HS A family of gas purification processes developed by Union Carbide Corporation, based on the use of proprietary solvents known as UCARSOLs. UCARSOL HS-101, is based on methyl diethanolamine and is used for removing hydrogen sulfide and carbon dioxide from other gases. Ucarsol LH-101 is used in its Cansolv system for flue-gas desulfurization. 

In Japan, there is a project aimed at capturing the considerable volume of hydrogen gas which can be obtained as a by-product steel production. R D will focus on the purification process of fuel from coke oven gas to an acceptable level for fuel cell utilisation. METI, the Japan Research and Development Centre for Metals and Nippon Steel are working on the project with a 2003 budget allocation of 549 million. Japan also operates the 4C/.f project which aimsto develop an optimum coal gasifier for fuel cells and the establishment of gas clean-up system for purification of coal gas to the acceptable level for utilisation for MCFC and SOFC. The budget allocations for 2000-2003 total 4.6 billion. 

The stock solution, ca. 0.3 mol dm-3, of hydrobromic acid was prepared from a twice-distilled sample of the hydrobromic acid. Its bromide content was determined gravimetrically as silver bromide. Triplicate runs agreed to within 0.02%. The silver + silver bromide electrode was of the thermal type, prepared by heating twice recrystallized silver bromate (10 mass percent) and silver oxide (90 mass percent) at a temperature of 820° K. The preparation of the silver oxide, the preparation of the hydrogen electrodes, the design of the cell, the purification of the hydrogen gas, and other experimental techniques, have been described earlier (13,14,15). The water bath in which the cells were immersed was controlled to within 0.02°K. 

Reactive absorption is probably the most widely applied type of a reactive separation process. It is used for production purposes in a number of classical bulk-chemical technologies, such as nitric or sulfuric acid. It is also often employed in gas purification processes, e.g., to remove carbon dioxide or hydrogen sulfide. Other interesting areas of application include olefin/paraffin separations, where reactive absorption with reversible chemical complexation appears to be a promising alternative to the cryogenic distillation (62). 

Today s coke plant gas purification processes are mostly carried out under atmospheric pressure, employing a circulated ammonia-based absorbent. The consumption of the external solvent is reduced via the use of ammonia available in the coke gas (138). An example of innovative purification processes is the ammonia hydrogen sulfide circulation scrubbing (ASCS) (Figure 17), in which the ammonia contained in the raw gas dissolves in the NH3 absorber and then the absorbent saturated with the ammonia passes through the H2S absorber to selectively absorb the H2S and HCN components from the coke gas. The next step is the thermal regeneration of the absorbent with the steam in a two-step desorption plant, whereas a part of the deaciditied water is fed back into the H2S absorber (25). 

Figure 17 Ammonia hydrogen sulfide circulation scrubbing process for the coke oven gas purification (right) and H2S absorber (left).

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