Hydrogen manufacture

Industrially hydrogen is mainly produced by two fundamentally different processes  

Hydrogen is also formed in large quantities as a byproduct in petrochemical processes, refineries, coking plants (coke oven gas) and in chemical and electrochemical processes e.g. chloralkali-electrolysis. Other processes such as the photochemical production of hydrogen or thermal dissociation of water are only used in special applications and are currently industrially unimportant. 

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Reactions of Synthesis Gas. The main hydrogen manufacturing processes produce synthesis gas, a mixture of H2 and CO. Synthesis gas can have a variety of H2-to-CO ratios, and the water gas shift reaction is used to reduce the CO level and produce additional hydrogen, or to adjust the H2 to-CO ratio to one more beneficial to subsequent processing (69) ... 

Two major sources of H2S emissions from the process are the acid gas stream evolving from hydrogen manufacture, Ri, and the gaseous waste emitted from the separation... 

Apparatus for carrying out hydrogenation at several atmospheres can be constructed readily (1,78,93), but there seems little point in this exercise since good commercial equipment is available. The most commonly used commercial low-pressure equipment is the Parr hydrogenator (manufactured by Parr Instrument Co., Moline, Illinois). This equipment (Fig. 1) has withstood the test of time it was first described in 1922 and offered commercially in 1926. It comes in two sizes one for 500-ml reactor bottles and one for 1000-and 2000-ml reactor bottles. Specially made smaller bottles, down to 50 ml, can be used also but require special holders to compensate for differences in bottle heights. Shaker bottles should not be more than half full to ensure good mixing, a consideration in selection of bottle size. 

Conversion levels should be limited so as to be compatible with the required hydrogen manufacture from unconverted coal. 

To illustrate this latter point, Figure 5 shows the calculated amount of coal required for hydrogen manufacture as a function of the rank of the starting coal and the composition of the desired products (10). In these calculations a 12.5% methane byproduct was assumed and the thermal efficiency of the hydrogen generation was assumed to be 70%. 

The data on Figure 6 indicate that some coals are difficult to convert to soluble form at short times. In fact, the degree of conversion at 425°C with the solvent chosen would not be high enough to balance the hydrogen manufacture/conversion stoichiometry, shown in Figure 5. Several alternatives are available to increase this conversion. Among these are to increase the temperature and/or pressure of the reaction. 

Very high conversion is not necessary because of hydrogen manufacture requirements. 

DaimlerChrysler is delivering fuel cell vehicles to customers in California. Shell Oil has established a Hydrogen Economy team dedicated to investigate opportunities in hydrogen manufacturing and fuel cell technology in collaboration with others, including DaimlerChrysler. 

Fig. 15.2 Cost of hydrogen fuel for five different modes of production, distribution and retail. All options other than electrolysis are NC-based for on-site reforming and electrolysis the cost for hydrogen manufacture is included in the retail-site costs.

The hydrogen manufacture process is relatively clean. In the steam reforming subprocess a potential waste source is the desulfurization unit, which is required for feedstock that has not already been desulfurized. This waste stream contains oil, sulfur compounds, and phenol. In the partial oxidation subprocess, free carbon is removed by a water wash. Carbon dioxide is discharged to the atmosphere at several points in the subprocess. 

Casper MS (1978) Hydrogen manufacture by electrolysis, thermal decomposition and unusual techniques. Noyes Data Corporation, New Jersey, USA... 

About a third of the hydrogen manufactured is used in mining for the hydrometallurgical extraction of copper and other metals, the extraction of the metals from their ores by reduction in aqueous solution ... 

Hydrocarbon-reforming catalysts, in Catalyst Handbook-with Special Reference to Unit Processes in Ammonia and Hydrogen Manufacture, Springer -Verlag, New York, Ch 5, pp. 63-96. 

The Hypro process is a continuous catalytic method (Figure 10-3) for hydrogen manufacture from natural gas or from refinery effluent gases. The process is designed to convert natural gas ... 

Hypro process a continuous catalytic method for hydrogen manufacture from natural gas or from refinery effluent gases. 

Feeds and Products, Barrels per Calendar Day Refinery Input High Severity Hydrotreating Catalytic Reforming Hydrogen Manufacture Recovery and Sulfur Plant Refinery Fuel Motor Gasoline Kerosene Jet Fuel By- Products... 

Hydrogen Manufacture 2 x 88 Million of Standard Cubic Feet per Operating Day 161 2 1 1 6 ... 

In all cases, the cost of hydrogen manufacture is at least 40% of the total. 

Selection of a process for hydrogen manufacture from hydrocarbons and coal therefore depends on the raw material and its cost, the scale of operation, the purity of the synthesis gas to be produced, the pressure level of the natural gas feed, and the number and type of processes that will consume the carbon monoxide and hydrogen. 

Figure 5.2. Hydrogen manufacturing process steps. (Reproduced by permission of Wiley-VCH )...

Steam reforming of natural gas is currently the most economic process for hydrogen manufacturing. However, the rising cost and diminishing supplies of natural gas have directed more and more attention toward the use of alternate feedstocks in recent years. 

As is explained in Reference 1, investment and operating cost data for various hydrogen manufacturing processes were provided for this study by Chem Systems, Inc., New York, New York. These economics data were developed using identical methods and assumptions, thereby permitting side-by-side comparisons of the several processes. 

Figure 7. Hydrogen manufacturing costs—midcontinent location (dollars per MBtu-100 Mscf/D plants—1980 dollars)...

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