In adiabatic prereforming

Catalyst Deactivation in Adiabatic Prereforming Experimental Methods and Models for Prediction of Performance... 

T.S. Christensen, Adiabatic Prereforming of Hydrocarbons - an Important Step in Syngas Production , Appl. Catal. A, 138 285-309 (1996). 

Figure 1. Temperature profiles in an industrial, adiabatic prereformer operating on naphtha feed in a H2-plant. H2O/C = 3.5 P = 26 bar Topsoe RKNGR Catalyst.

Rostrup-Nielsen found that the intrinsic reaction rate, rj, for methane steam reforming is correlated with the sulphur coverage by equation 6 (2). In the adiabatic prereformer, the sulphur acts as a pore mouth poison and as the reactions are restricted by pore diffusion 2,8), the effective activity of the sulphur poisoned catalyst pellet can be described by an empirical relation, equation 7, between the effective pellet reaction rate, rp, and the average sulphur coverage, 0av (7/... 

The individual catalyst sample typically shows the presence of 2-4 peaks and Figure 5 shows a TPR diagram for a catalyst that has been in operation for 6 months in an adiabatic prereformer with a naphtha feedstock at relative low temperature. Three peaks have been identified for this catalyst and they are ascribed to chemisorbed carbon (a-type) at 300°C, gum (P-type) at 480°C and the platelet/pyrolytic carbon (e-type) at 650°C. In addition some graphitized carbon is also observed as a weak peak at high temperature around 950°C. 

The major advantages of incorporating an adiabatic prereforming step in reforming of high hydrocarbons include the following ... 

As has been discussed in Section 2.3.6, the use of an adiabatic prereformer also helps in alleviating the risk of carbon formation in the steam reforming of higher... 

Christensen, T.S. Adiabatic prereforming of hydrocarbons—An important step in syngas production. Applied Catalysis. A, General, 1996, 138 (2), 285. 

The activity of the catalyst is roughly proportional to the surface area of nickel used. In an adiabatic prereformer, a high activity is desired to maximize the space velocity. In a tubular reformer the activity may be of less significance because the reactor volume is settled by mechanical criteria. Most industrial tubular reformers operate at space velocities of 2000-4000 hr However, equilibrium conversion can be... 

A typical process diagram for producing syngas with ATR is shown in Fig. 11. Adiabatic prereforming... 

Steam reforming of naphtha is well established in industry. Characteristics of the reactions are summarized including a discussion of possibilities to control carbon formation by catalyst formulation. The progress in tubular reforming of natural gas related mainly to use of higher temperatures can be implemented for liquid feedstocks by installation of an adiabatic prereformer. This is illustrated by industrial examples. 

Fig. 9. Temperature Profiles of Adiabatic Prereformer in Hydrogen Plant...

These constraints are removed when using an adiabatic prereformer [394] [415] as illustrated in Figitre 1.14. The prereforming catalyst is typically a highly active nickel catalyst. This catalyst also works as an effective sulphur guard for the tubrrlar reformer and downstream catalysts, by removing any traces of strlphur still left after the desulphurisation section. 

The feedstocks are hydrocarbons, steam, and either oxygen or air (or a mixture thereof). Optionally, carbon dioxide may be added to the hydrocarbon stream (refer to Section 2.4.2). The mixture of hydrocarbon and steam is preheated and mixed with oxygen in the burner. An adiabatic prereformer may be advantageous to eliminate thermal cracking of higher hydrocarbons in the preheater. 

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