Hydrogen capital

Figure 8.3 highlights that for PEC with a 1 Sun photocurrent of 8 mA/cm and a bias of 0.8 V, capital costs of hydrogen per kg less than 3/kg, with a 10-year payback, cannot be achieved (solid line). Equally, PEC at similar photocurrents with 1.2 V bias cannot achieve sub- 3/kg hydrogen costs even with a 15-year payback (large dashed line). To achieve sub- 3/kg hydrogen capital costs for PEC with photocurrents of 8 mA/cm, the bias must be at least as low as 0.8 V with a 15-year payback and PEC costs below 100/m (small dashed line). If the bias can be reduced further to 0.4 V then with a 15-year payback PEC costs as high as 150/m can be sustained, which is arotmd half the current cost of PV. 

Natural gas is by far the preferred source of hydrogen. It has been cheap, and its use is more energy efficient than that of other hydrocarbons. The reforming process that is used to produce hydrogen from natural gas is highly developed, environmental controls are simple, and the capital investment is lower than that for any other method. Comparisons of the total energy consumption (fuel and synthesis gas), based on advanced technologies, have been discussed elsewhere (102). 

The upper limit of efficiency of the biophotolysis of water has been projected to be 3% for weU-controUed systems. This limits the capital cost of useful systems to low cost materials and designs. But the concept of water biophotolysis to afford a continuous, renewable source of hydrogen is quite attractive and may one day lead to practical hydrogen-generating systems. 

Coal gasification technology dates to the early nineteenth century but has been largely replaced by natural gas and oil. A more hydrogen-rich synthesis gas is produced at a lower capital investment. Steam reforming of natural gas is appHed widely on an iadustrial scale (9,10) and ia particular for the production of hydrogen (qv). 

Some processes use only one reactor (57) or a combination of liquid- and vapor-phase reactors (58). The goal of these schemes is to reduce energy consumption and capital cost. Hydrogenation normally is carried out at 2—3 MPa (20—30 atm). Temperature is maintained at 300—350°C to meet a typical specification of less than 500 ppm benzene in the product at higher temperatures, thermodynamic equiUbrium shifts to favor benzene and the benzene specification is impossible to attain. Also, at higher temperatures, isomerization of cyclohexane to methylcyclopentane occurs typically there is a 200 ppm specification limit on methylcyclopentane content. 

Radicals from partially hydrogenated heterocycles may be named in two ways in the usual manner, using the appropriate hydro prefix for the parent compound, or by use of the indicated hydrogen convention (italic capital H and locant, enclosed in parentheses). The symbol for the indicated hydrogen must be written immediately following the locant for the radical site, e.g. (163). 

The odor control market is the largest and much of this market is in sewage treatment plants. Use of ozone for odor control is comparatively simple and efficient. The application is for preservation of environmental quality in addition, alternative treatment schemes requiring either liquid chemical oxidants (like permanganate or hydrogen perioxide) or incineration can significantly increase capital and costs. 

Determination of the actual cost of a hydrogenation process is difficult. Among the factors entering into the determination are catalyst cost, catalyst life, cost of materials, capital investment, actual yield, space-time yield, and purification costs, Considerable data are needed to make an accurate evaluation. 

See also Biofuels Capital Investment Decisions Hydrogen Kinetic Energy, Historical Evolution of the Use of Methanol Natural Gas, Processing and Conversion of. 

Even in a simple hydrogen fuel cell system, capital cost reduction requires improvements in many diverse areas, such as catalyst loadings, air pressuriza-... 

A simple cell design is required to reduce capital costs. The cost of the raw materials, HF and electricity, are not negligible, but they are minor. The pilot plant cell design shown in Fig. 16 is derived from the callandria cell developed for the Phillips ECF process.14 The cell body and internals are of mild steel pipe selected to be resistant to hydrogen embrittlement. Figure 17 is a horizontal section through the working part of the cell. 

Catalytica (ref. 7) have reported a recovery process based on air and catalyst. Whilst the reagent is cheap, the process requires high capital investment. It is a clean process but only treats hydrogen bromide streams and cannot treat inorganic bromide streams directly. 

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