Best Way to Generate Hydrogen, CO and Syngas

Electrolysis produces hydrogen (H₂) by using electrical energy to split water into oxygen (O₂) and H₂. When renewable energy is used to split the water, the resulting H₂ is green. The two main technologies currently deployed at scale are alkaline and proton exchange membrane (PEM) electrolysis. Both electrolyzer technologies can deliver high-purity H₂ on demand and on site.

Alkaline Electrolysis

Alkaline electrolysis is a very well-established technology that uses two electrodes separated by a porous diaphragm and a liquid alkaline solution as the electrolyte. The electrolyte solution allows hydroxide ions to be transported between the electrodes to form H₂ and O₂. It is not, however, consumed during the reaction. This technology is extremely efficient, reliable and cost-effective. We have extensive experience in this area, having installed over 80 alkaline electrolyzers globally.

Proton Exchange Membrane (PEM)

PEM electrolysis uses pure water and a solid polymer electrolyte instead of a liquid solution. The electricity splits the water into H₂ and O₂. Hydrogen protons pass through the membrane, combining with electrons to form H₂ gas on the cathode side.

PEM electrolyzers are well suited to volatile renewable energy sources thanks to their fast ramp-up/down capabilities and their wide dynamic operating range. No corrosive electrolyte is involved, and they operate at high current density, which speeds up the breakdown of the water molecule, ultimately favorably impacting the production price. Finally, a small footprint and compact system design is a benefit for many on-site industrial applications.

Learn more about electrolysis here

Steam reforming is the most widespread process for the generation of H₂-rich synthesis gas (syngas) from light hydrocarbons. Steam reforming involves endothermically converting feedstocks such as natural gas, liquid gas or naphtha into syngas.

The desulfurized hydrocarbon feed is mixed with superheated process steam in accordance with the steam-to-carbon (S/C) ratio necessary for the reforming process. This gas mixture is then heated up and distributed on the catalyst-filled reformer tubes. The gas mixture flows from top to bottom through tubes arranged in vertical rows. While flowing through the tubes heated from the outside, the hydrocarbon/steam mixture reacts, forming H₂ and carbon monoxide (CO) in accordance with the following reactions:

1. C_nH_m + n H₂O => n CO + ((n+m)/2) H₂
2. CH₄ + H₂O <=> CO + 3 H₂
3. CO + H₂O <=> CO₂ + H₂

To minimize the methane (CH₄) content in the syngas while simultaneously maximizing the H₂ yield and preventing the formation of elemental carbon (which would otherwise be deposited on the catalyst), the reformer is operated with a higher S/C ratio than theoretically necessary.

As the heat balance for the main reactions (1 – 3) is endothermic, the required heat must be produced by external firing. The burners for the firing are arranged on the ceiling of the firing area between the tube rows and fire vertically downward. The residual gas from the pressure swing adsorption (PSA) unit as well as heating gas from battery limits is used as fuel gas. The flue gas is then cooled down in a convection zone, generating steam.

As a leading supplier of steam reformer plants, we have built more than 200 units supporting syngas capacities extending from 300 to over 200,000 Nm³/h.

Syngas generation based on the conventional steam reforming process requires considerable amounts of process steam. Many operators are therefore keen to reduce the S/C ratio of syngas generation. With conventional reforming catalysts, the reduction of steam can ultimately lead to or accelerate deactivation of the catalyst due to carbon accumulation and coke formation. The BASF SYNSPIRE™ catalyst overcomes this limitations.

Our DRYREF™ syngas generation plant complements the SYNSPIRE™ catalyst to offer a number of compelling benefits beyond the prospect of clean energy and a contribution to climate mitigation. These benefits make DRYREF™ technology an attractive and competitive alternative to partial oxidation plants with low H₂/CO ratios – effectively extending the H₂/CO reach of steam reforming.

Benefits of DRYREF™ plants include less surplus process steam flowing through the plant and the ability to adjust the syngas composition over a wider envelope. The better thermodynamic equilibrium results in less net CO₂ that needs to be removed. This shrinks the CO₂ removal equipment footprint with less regeneration and recompression energy required. The reduced S/C ratio required for the process allows the boiler and steam equipment to shrink in size or enables additional steam export. This translates into significant CAPEX and OPEX gains.

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ATR generates hydrogen-rich syngas from natural gas. Here, steam-methane reforming (SMR) and partial oxidation (POX) processes are combined in a single catalytic reactor using O₂ and water steam. The addition of O₂ to the process means that high temperatures can be achieved inside the reactor, facilitating a high syngas conversion at low S/C ratio. This allows for high H₂ production capacities in a single train.

As CO₂ is part of the pressurized syngas leaving the shift reactor, this process facilitates carbon capture. In fact, ATR supports carbon capture rates in excess of 95 %, making this technology essential for low-carbon (blue) H₂ production.

POX is an autothermal process that generates syngas from heavy hydrocarbon feedstocks and O₂. Unlike SMR and ATR, it does not require a catalytic conversion step, which makes it suitable for all kinds of feedstocks. A typical process scheme is shown down here. Our POX process concept supports all type of hydrocarbon feedstocks – from natural gas to coal, and delivers a broad variety of products.

As one of the leading contractors for POX plants worldwide, we have more than 40 years of experience. In addition, we are the only company worldwide that engineers, builds and operates POX plants.

POX with Linde – Huge Selection of Feedstocks and Output Products