Plants with conventional steam reforming

Application To produce ammonia from natural gas, LNG, LPG or naphtha. Other hydrocarbons—coal, oil, residues or methanol purge gas— are possible feedstocks with an adapted front-end. The process uses conventional steam reforming synthesis gas generation (front-end) and a medium-pressure (MP) ammonia synthesis loop. It is optimized with respect to low energy consumption and maximum reliability. The largest single-train plant built by Uhde with a conventional synthesis has a nameplate capacity of 2,000 metric tons per day (mtpd). For higher capacities refer to Uhde Dual Pressure Process. 

Application Production of ammonia from natural gas, LNG, LPG or naphtha. The process uses conventional steam reforming synthesis gas generation in the front-end, while the synthesis section comprises a once-through section followed by a synthesis loop. It is thus optimized with respect to enable ammonia plants to produce very large capacities with proven equipment. The first plant based on this process will be the SAFCO IV ammonia plant in Al-Jubail, Saudi Arabia, which is currently under construction. This concept provides the basis for even larger plants (4,000-5,000 mtpd). 

Most new large methanol plants are built in areas where low cost natural gas is available. If the synthesis gas is produced by the conventional one-step process, with a steam reformer only, the module will always be around 3 with natural gas as feed. Process studies (Soegaard-Andersen, 1989) have shown that for capacities above 1000-1500 t/d it is economical to adjust the module to the optimum value by adding an oxygen-fired autothermal reformer downstream the steam reformer as shown in Figure 12. This two-step reforming process (Dybkjaer et al., 1985) is similar to the well-known process lay-out with a primary and secondary reformer used in ammonia plants. 

Today, different processes (steam reforming, autothermal reforming, partial oxidation, gasification) are available and commercially mature for hydrogen production from natural gas or coal. These processes would have to be combined with technologies for C02 capture and storage (CCS), to keep the emissions profile low. A power plant that combines electricity and hydrogen production can be more efficient than retrofitted C02 separation systems for conventional power plants. 

The present treatment of the conventional process will be based on the process diagram presented in Figure 1, which represents a steam reformer coupled with an ammonia synthesis plant [6], This is one of the two cases, which were considered in the project. The other was the use of the produced hydrogen as fuel in combined cycle gas turbines. In this chapter, the steam reforming part will be treated only, but some comments on the ammonia plant will be made, in view of the composition of the product stream leaving the steam reformer. 

H-Oil unit are processed for sulfur recovery and then sent for separation through the gas recovery facilities associated with the steam cracker. Remaining unconverted residue from the H-Oil operation is used as a fuel oil component for plant fuel. Ethylene is manufactured by steam cracking of ethane, propane, naphtha, and distillate, and products from these operations are separated in conventional gas recovery facilities. Hydrogen for H-Oil is partially supplied by by-product recovery from steam cracker and H-Oil off-gases supplemented by steam reforming of methane. The heavy oils produced in steam cracking of naphtha and distillate are blended with the H-Oil residue to yield plant fuel. 

Conventional processes for the production of syngas involve partial oxidation or steam reforming. In the process with oxygen, an expensive air-separation plant is required, whereas in the case of steam reforming high-temperature heat additions are necessary. 

The conventional plant with a gas fired reformer is considered to be running at near optimum operating conditions. However, for the gas burner air is used instead of pure oxygen. Mains water is also used in the steam production plant. 

In the development of the steam-reforming route to ammonia, for many years there has been a desire to eliminate the steam-reforming furnace for reasons of capital cost, efficiency, and reliability. This technology has now been demonstrated on a commercial scale by ICI with the LCA process. With this process the plant is simplified by the use of a Gas Heated Reformer (GHR) in which the primary reformer receives heat directly from the process gas leaving the secondary reformer. This compact pressurized reformer eliminates the massive furnace structure and the high-pressure steam system of a conventional plant. A pressure swing adsorption... 

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