Reformer radiant section

Steam-methane reformers generate the majority of the world s on-purpose hydrogen. A steam-methane reformer (SMR) is a fired heater with catalyst-filled tubes. Hydrocarbon feedstock and steam react over the catalyst to produce hydrogen. The reacted process gas typically exits the reformer at about 1600°F The flue gas leaving the reformer radiant section is typically about1900°F. 

The primary reformer is essentially a process furnace in which fuel is burned with air to indirectiy provide the heat of reaction to the catalyst contained within tubes. This area of the furnace is usually referred to as the radiant section, so named because this is the primary mechanism for heat transfer at the high (750—850°C) temperatures required by the process. Reforming pressures in the range 3 —4 MPa (30,000—40,000 atm) represent a reasonable compromise between cost and downstream compression requirements. 

Fig. 13. Radiant section of a Kellogg box-type steam reforming furnace.

One of the most effective reformer modifications is to use heat from the convection section to preheat radiant section feed. This will reduce radiant section duty and firing rate. The effectiveness of this option is limited only by the risk of coking in the preheat coil, the metallurgy of the preheat coil and the metallurgy of the radiant inlet system. This option has been used to increase capacity by 10% without increasing the arch temperature in the radiant section86. 

Montedison Low-Pressure Process. The Montedison low-pressure process [940], [1036], [1128], [1129] involves a split flow to two primary reformers. About 65% of the feed-steam mixture flows conventionally through the radiant tubes of a fired primary reformer followed by a secondary reformer. The balance of the feed-steam mixture passes through the tubes of a vertical exchanger reformer. This exchanger reformer has a tube sheet for the catalyst tubes at the mixed feed inlet. There is no tube sheet at the bottom of the tubes, where the reformed gas mixes directly with the secondary reformer effluent. The combined streams flow on the shell side to heat the reformer tubes in a manner similar to that described for the M. W. Kellogg KRES reformer, see Sections 4.1.1.8 and 5.1.4.3). The process air flow is stoichiometric. Synthesis is performed at 60 bar in a proprietary three-bed indirectly cooled converter with am-... 

The process specifications on raw material speed through furnaces coils imposed the use of two or four parallel passes, e.g. the fumaees from the atmospherie distillation unit, vacuum distillation unit, catalytic reforming unit, coker unit, catalytic cracking unit. The conventional control structure of radiant section for a typical tubular furnace from the atmospheric distillation unit (output capacity 3.5 Mt/year) is presented in figure 1 [1]. Because the conventional temperature control system only controls one outlet temperature or in the best case the temperature of the mixing point, in current operations there are several situations [1, 2, 3] ... 

In the top-fired reformer, the burners are located only on the roof between the rows of reformer tubes. The heating is direct from the combustion products to the tube walls. In this configuration firing occurs only at one level, heating the natural gas as it enters the reformer. The burner to tube ratio is low and the combustion air product distribution is simplified. The unit is compact, using less steel, and has large tube capacities (600—1000) per radiant section. However, the operating environment above the box is uncomfortable and the control of heat input into the reformer is limited. 

The bottom-fired reformer is classified into two types, one with the reforming gas flowing down the tube (as in top-fired and side-fired) and the other where the process gas flows up the reformer tubes. The burners are located on the floor on either side of two rows of reformer tubes. The flames are long and pencil thin. The system has a simplified air combustion distribution and single operating level. The system cannot handle more than 200-300 reformer tubes per radiant section and the tube metal temperatures at the process gas outlet are higher than the inlet. 

The reactor tubes are fired by burners, which may be located at the bottom, at the side, or at the top of the furnace. Combustion of the fiiel takes place in the radiant section of the furnace. After the flue gas has been supplied all the reactor duty, it passes into the convection section where it is further cooled by heating other streams such as process feed, combustion air and boiler feed water, as well as producing steam. The product gas, leaving the reformer at a temperature of 850-950°C, is cooled in a process gas waste heat boiler (PGWHB), which produces process steam for the reformer. 

The HTCR reactor consists of a number of bayonet reformer tubes and combines basically the radiant section and the convection section of a conventional HSR in a single piece of equipment. The reaction heat is provided by the flue gas fiowing on the outside of the reformer tubes and by reformed gas fiowing in an upward direction in the bayonet tubes. This results that is about 80% of the fired duty is utilized in the process, and steam export is minimized. 

Reformer In a reformer furnace, shown in Exhibit 7-5, preheated process fluid flows through catalyst-filled tubes, which are usually located in the center of the radiant section. This type of furnace may have single or multiple compartments burners may be mounted in the roof, wall, or floor. Heat recovery systems may also be employed through the use of waste heat boilers or the convection section s steam generation coils. 

The Haldor Topsoe Convection Reformer (HTCR) is a relatively small piece of equipment that combines the radiant and waste heat sections of the conventional reformer. It uses PSA (pressure swing absorption) to make 99.9 percent hydrogen purity. It is best for small and medium-sized hydrogen plants (500 to 10,000 Nm3/hr).75... 

For temperatures >500°C, put tubes in furnace. Same area of application, guidelines, and good practice as empty tube. Section 16.11.6.3. Radiant heat flux in furnaces 30 to 80 kW/m. Reformers ... 

The right-hand side of this figure shows the radiant reformer box, and the left-hand side show the convection section and the flue gas stack. 

The radiant box of the reformer is typically about 50% efficient. Thus, to ensure a thermodynamically efficient operation, the heat liberated but not absorbed in the reforming reaction must be recovered in the convection section of the reforming furnace. Typically the reformer flue gases are redueed to about 150°C, resulting in an overall furnace efficiency of 9293%. 

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