Feed requirement, steam-reforming

Because hydrocarbon feeds for steam reforming should be free of sulfur, feed desulfurization is required ahead of the steam reformer (see Sulfur REMOVAL AND RECOVERY). As seen in Figure 1, the first desulfurization step usually consists of passing the sulfur-containing hydrocarbon feed at about 300—400°C over a Co—Mo catalyst in the presence of 2—5% H2 to convert organic sulfur compounds to H2S. As much as 25% H2 may be used if olefins... 

The electricity requirement for large-scale hydrogen liquefaction amounts to about 0.3 MJei per MJ of LH2 today (suction pressure typically 2 to 3 MPa, which corresponds to the outlet pressure of the PSA of a typical steam reforming plant), but can be reduced to about 0.16 MJel per MJ of LH2, if the feed pressure can be increased (Quack, 2001). 

M REC, as the TREC, does not depend on the reaction path. In addition, there is no dependence on the membrane-permeation properties (related to the time required for species permeation).1 In any case, the final value reached depends on the extractive capacity of the system, for example, the pressure and composition on the permeate side. The composition on the permeate side, similarly to the feed molar ratio, can be expressed by considering the ratio (named sweep factor) between the initial molar number of nonpermeating species (present on the permeate side) and the initial molar number of the reference reactant, for example, methane for methane steam reforming, or carbon monoxide for water gas shift). The sweep factor was defined for a closed M Ras ... 

In some cases a plant may have a pre-reformer. A pre-former is an adiabatic, fixed-bed reactor upstream of the primary reformer. It provides an operation with increased flexibility in the choice of feed stock it increases the life of the steam reforming catalyst and tubes it provides the option to increase the overall plant capacity and it allows the reformer to operate at lower steam-to-carbon ratios166. The hot flue gas from the reformer convection section provides the heat required for this endothermic reaction. 

The nickel-based reforming catalysts which are commonly used in steam reforming are quite sensitive to sulphur, halogen and heavy metal poisons. Since these elements may all be found in natural gas, a feed gas purification section is normally required. Of the mentioned catalyst poisons, sulphur is by far the most important [6],... 

This paper analyzes the sources of hydrogen for ammonia production, presents the feed and fuel requirements of the natural gas steam reforming process, estimates the relative economics of alternate feedstocks and briefly discusses the outlook for the ammonia industry. 

Assuming the feedstock is methane, which is the major component of natural gas, the theoretical feed requirement would be equivalent to one-fourth of the potential hydrogen production or 16,713 SCF CH /ST NH3(15.2 MM BTU/ST). However, the actual process consumes on the order of 22,420 SCF CHi+/ST NH3 or about 20.4 MM BTU/ST NH3 (LHV). The required quantity of feed depends on the process design criteria chosen for the methane conversion in the reforming section, the efficiency of CO conversion, degree of CO2 removal and the inerts (CHi+ + Ar) level maintained in the ammonia synthesis loop. Thus, the potential hydrogen conversion efficiency of the feedstock in the steam reforming process is about 75%. Table 3 shows where the balance of the feed is consumed or lost from the process. 

Coal Feed. As in the case of steam reforming versus partial oxidation, a plant based on use of coal as feedstock is expected to cost more than one based on partial oxidation because of additional equipment requirements, particularly with regard to coal handling operations, gasification and raw gas treatment. Despite these cost differences, coal based plants can be justified if the cost of coal is sufficiently low, that is, relative to light or heavy hydrocarbons. The approximate investment for a coal-based plant appears to be about 2.0 times that for a natural gas plant.The investment is about 33% more for a fuel oil... 

Steam reforming using natural gas and other light hydrocarbon feed stocks will continue to be the most attractive method of manufacturing willfully-produced refinery hydrogen. Feed stocks required for reforming in U. S. refineries will increase from about 150,000 B/D crude oil equivalent in 1980 to 330,000 B/D in the year 2000. 

Table 7 also shows these hydrogen requirements as 0.21 Quad/year in 1980 and 0.46 Quad/year in the year 2000 (coking option) or 1.41 Quad/year (hydroprocessing option). Assuming these quantities of hydrogen are produced by steam reforming, the reformer feed stock requirements would increase from 149 thousand B/D crude oil equivalent in 1980 to 326 thousand B/D in the year 2000 option) or 1001 thousand B/D for the year... 

Description Syngas preparation section. The feedstock is first preheated and sulfur compounds are removed in a desulfurizer (1). Steam is added, and the feedstock-steam mixture is preheated again. A part of the feed is reformed adiabatically in pre-reformer (2). The half of feedstock-steam mixture is distributed into catalyst tubes of the steam reformer (3) and the rest is sent to TEC s proprietary heat exchanger reformer, "TAF-X" (4), installed in parallel with (3) as the primary reforming. The heat required for TAF-X is supplied by the effluent stream of secondary reformer (5). Depending on plant capacity, the TAF-X (4) and/or the secondary reformer (5) can be eliminated. 

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