High-temperature steam reforming reactor design

Based on the type of thermal destruction process selected, there are several different commercial designs and configurations of the reactor that have been utilized for a particular application. Some of the most commonly used technologies include rotary kilns, starved air incinerators, fluidized beds, mass-bum incinerators, electrically heated reactors, microwave reactors, plasma, and other high-temperature thermal destruction systems. Recent advances include gasification and very high temperature steam reforming. 

The most common industrial method to make ultra-pure hydrogen is by steam-methane reforming (SMR) using a catalyst at the temperature 890-950° C. The reformed gas is then subjected to a high temperature water gas shift (WGS) reaction at 300-400°C. The WGS reactor effluent typically contains 70-80% H2, 15-25% CO2, 1-3% CO, 3-6% CH4, and trace N2 (dry basis), which is fed to a PSA system at a pressure of 8-28 atm and a temperature of 20 0°C for production of an ultrapure (99.99+ mol%) hydrogen gas at the feed pressure. Various PSA systems have been designed for this purpose to produce 1-120 million cubic feet of H2 per day. 

Residual methane is present at the exit of the combustion zone. In the catalytic bed, the methane steam-reforming and the water shift reactions take place. The gas leaving the ATR reactor is in chemical equilibrium. Normally, the exit temperature is above 900-1100°C. The catalyst must withstand very severe conditions when exposed to very high temperatures and steam partial pressures. One example of an ATR catalyst is nickel supported by magnesium aluminum spinel. For compact design, the catalyst size and shape is optimized for a low pressure drop and high activity. 

Nuclear reformer tube heating with a high-temperature reactor is performed with helium, typically at 950 °C, as the heat source. A counterflow scheme allows the use of internal return pipes for the product gas. Experience in construction and operation was gained with the EVA-I and EVA-II facilities at the Research Center Jiilich. The perceived disadvantages of a nuclear steam reformer with its comparatively low heat transfer and its high system pressure can be overcome by design optimization to increase heat input into the process gas and its conversion rate. 

A possible approach Natural gas can be converted at a high temperature into hydrogen, CO, C02 (syngas) in a steam reformer or partial-oxidation reactor, or autothermal reformer which is a combination of the first two. Most of the CO in the syngas is typically converted into carbon dioxide at a lower temperature in a water-gas shift reactor. The remaining small amount of CO must be removed to below 10 ppm level. This can be done using adsorption, or membrane separation, or catalytic preferential oxidation (at about 90°C with an air stream), or other practical means. Also, there are designs with membrane reformers in the literature. 

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