Efficiency reforming

The plasma reformer efficiency reached 12.3% and 26% in gasoline auto thermal and steam reforming regimes, respectively. The typical composition of the effluent gas from the reformer operating in steam reforming mode was (vol%) H2—28.7, CO—15, C02—3, and CH4—40. 

When combustion air preheat is used, the air preheat unit may replace the boiler feed water coil. Flue gas exits this unit at about 300 degrees F. This provides a typical heat loss of 3% of the overall reformer efficiency. Steam is also made in a process steam generator which extracts heat from the reformer outlet process gas. The heat recovery unit and process steam generator normally have a common steam drum. 

Contrary to widely-held opinion, POX and ATR are capable of higher reforming efficiencies than are steam reformers (15). 

A structured ruthenium catalyst (metal monolith supported) was investigated by Rabe et al. [70] in the ATR of methane using pure oxygen as oxidant. The catalytic activity tests were carried out at low temperature (<800 ° C) and high steam-to-carbon ratios (between 1.3 and 4). It was found that the lower operating temperature reduced the overall methane conversion and thus the reforming efficiency. However, the catalyst was stable during time on-stream tests without apparent carbon formation. 

Small reformers R D areas include compact and low cost reformers (1-5 kW) to convert fossil fuels (natural gas, gasoline) or biomass fuels (ethanol) to hydrogen via different processes (steam reforming, partial oxidation, auto-thermal, non catalytic hybrid steam reforming). Improvements in reformer efficiency, capacities and response times, and integration of purification unit are also being studied. Examples of projects include ... 

Keywords hydrogen production, reformer, efficiency, process simulation, reactor... 

In the case of recirculation-type membrane reformer, efficiency of reactor heat utilisation = 60%, yield of hydrogen from methane = 95%... 

The reforming reactions require the input of water and heat. Overall, the reformer thermal efficiency is calculated as the latent heat of vaporization (LHV) of the product hydrogen divided by the LHV of the total input fuel. This thermal efficiency depends on the efficiencies of the individual processes, the effectiveness to which heat can be transferred from one process to another, and the amount of energy that can be recovered through means such as turbochargers. In the end, high-temperature reformer efficiencies are approximately 65% and low-temperature methanol reformers can achieve 70%-75%. 

Fig. 14.7 Model based prediction of FPS and reformer efficiency is shown along with hydrogen recovery from the fixed volume membrane reactor...

The catalytic partial oxidation is an exothermic process with an easy thermal management. But the natural gas and air supply to the CPOX reactor is ambitious. On the one hand hydrogen yield and the reforming efficiency are lower in opposite to the steam reforming. On the other hand is the required amount of equipment involved is lower in comparison to the steam reforming. 

Figure 3.17 Reforming efficiency profiles of the systems studied as a function of the reactor...

Figure 14.8 Effect of feed inlet temperature and O/C ratio (here shown as O2/C ratio) on reforming efficiency (O/C = 2.5, GffSy=9 900-10 800h" ) [44], (Source Karatzas et al. [44]. Reproduced with permission of Elsevier.)...

Hartmann et al. performed a comparison of the reformer efficiency for diesel fuel [69] under conditions of steam reforming and partial oxidation with and without steam addition at a reaction temperature of 800 °C. The efficiency shown in Figure 3.13 was calculated according to the definition provided in Eq. (2.2), Section 2.2. For partial oxidation in the absence of steam in the feed, the optimum air ratio was calculated to be 0.35 [69], which corresponds to an O/C ratio of 1.07, when pentadecane was assumed to be the feedstock. The efficiency was calculated to be 75% under these conditions. In the presence of steam, the optimum conditions were determined to an O/C ratio of 1.07 and an S/C ratio 0.4, which corresponded to an efficiency of 82%. A much higher efficiency of greater than 95% was found when the S/C ratio was increased beyond 1.0 and the O/C ratio decreased below 0.6 (air ratio 0.2), which proves once more that excessive air addition at an O/C ratio of around 1.0 impairs the efficiency of the reforming process. 

The efficiency of the steam reformer fuel processor of 96.6% was much higher than the autothermal reformer efficiency (88.8%), which in turn also increased the system efficiency (38.7% compared with 35.5% for the autothermal reformer) [443]. The heat removal required for the two air coolers was much lower for the steam reformer (about 2.1 kWcompared with 3.4 kW for the autothermal reformer). This in turn reduced the size of these components, which was a substantial benefit because the air coolers contributed significantly to the overall system size. The volume required is a stringent factor, especially in mobile systems. All the benefits of steam reforming clearly have the drawback of a more complex reactor design, which needs to be addressed by suitable manufacturing techniques in order to become competitive in price and not just in performance (see Section 10.2). 

Table 5.14 Comparison of product mass flow rates, reformer efficiency T f., fuel processor efficiency T fp and auxiliary power unit efficiency T)apu of autothermal reforming dry hydrogen molar fraction of the reformate yjj values are determined for various fuels, feed inlet...

Table 5.15 Comparison of product mass flow rates, reformer efficiency T r, fuel processor efRciency T fp and auxiliary power unit efRciency T apu of steam reforming values are determined for various, feed inlet temperatures Tjn and S/C (SCR) and O/C ratios (expressed as O2/C ratio OCR) as calculated by Specchia etal. [371]. is the fraction of the fuel which is fed to the steam reformer 1- Pr is fed to the burner yp is the dry hydrogen molar fraction of the reformate Wq shows the water balance of the systems, which is positive when the Wq exceeds unity. 

With a thermodynamic analysis, Medrano et al. compared the efficiency of this novel concept with other concepts reported in the literature for hydrogen production with CO2 capture. A comprehensive comparison of the reforming efficiency obtained with the different technologies is depicted in Figure 33.11. At... 

FIGURE 9-29. Relationship between reformer efficiency and equivalence ratio. 

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