Gasification Technologies for Hydrogen Production

Coal gasification technology

Investors, major operators and energy companies around are intensifying their efforts to identify hydrogen investment opportunities, knowing that hydrogen is set to play a pivotal role in securing the world’s long-term energy future.

Hydrogen is the perfect energy carrier – it is non-polluting and can be extracted from water to and its role in low carbon economies can be a major one.

There are several ways of producing hydrogen gas. Popular commercial-scale production methods include thermal processes, using electrolysers, and photolytic processes. The most commonly used technologies involve gasification and electrolysis.

While the focal point of researchers is towards the generation of hydrogen from renewable energy, the three most mature technologies currently in use are:

  • Biomass gasification
  • Coal gasification
  • Electrolysis

Biomass Gasification

Biomass gasification uses a controlled process involving oxygen gas and steam to convert biomass to hydrogen, without combustion.

The gasification process converts organic materials at high temperatures (usually above 700 °C) without combustion, using a controlled amount of steam and/or oxygen into hydrogen, carbon dioxide, and carbon monoxide. The carbon monoxide proceeds to react with water to create carbon dioxide and more hydrogen through a water-gas shift reaction. To remove the hydrogen from the gas stream, special membranes or adsorbers are deployed.

A shift reaction step (involving steam) will convert the carbon monoxide to carbon dioxide. The resulting hydrogen gas is then separated and used in different applications. hydrogen produced is then separated and purified.

But first, what is biomass?

Biomass is an organic resource that includes agricultural residues, forest residues, and animal waste. It can be used to generate hydrogen, as well as other products, by gasification.

[Bot out close]

  • The main reason why this method is preferred over others is because the growth of biomass reduces carbon dioxide from the environment. This means that the net carbon emissions from this method are low, especially when you combine them with carbon capture and storage in the long term.
  • Many gasification facilities for biofuels are currently being built and operated in the US and can provide a reliable hydrogen production source.

Biomass, while being viewed as a replacement to coal, does not burn as efficiently as coal and often creates other hydrocarbon compounds. These byproducts will exit the gasifier and harm the environment. An additional process is required to reform these hydrocarbons with catalysts to yield an environmentally friendly syngas mixture of hydrogen, carbon dioxide, and carbon monoxide.

  • Despite the extra steps it takes to produce hydrogen from biomass, a number of projects are springing up around the world. This is because biomass is easily available and there is an abundant supply in the market. In fact, over 1 billion tons of biomass could be available for use in energy applications.

Coal Gasification

The main technology for the production of hydrogen continues to be coal gasification, for the simple reason that coal is so deeply embedded in energy systems and infrastructure worldwide. The challenge is to harness the power of coal into energy and useful byproducts such as hydrogen.

In the gasification process, coal is reacted with a gasification agent in an endothermic reaction that requires an input of heat to progress. Because the resulting gas is only partially oxidized, it can then be used as a fuel.

Producing hydrogen requires partial oxidation, which is done by introducing air to the coal. This generates carbon dioxide through traditional combustion. It should be noted that excess oxygen is not added otherwise it would completely burn the coal – only enough oxygen is used to generate the heat needed for gasification.

The partial oxidation results in the creation of gasification agent and carbon dioxide. Carbon dioxide then reacts with the rest of the carbon to form carbon monoxide. Carbon monoxide is now further reacted with steam, creating carbon dioxide and hydrogen. The hydrogen can then be siphoned off to generate electricity.

Electrolysis of Water

 At its core, an electrolyser consumes electricity to perform an electrolytic process using an anode and a cathode to split hydrogen gas and oxygen, with hydrogen as the target. This reaction usually takes place in a unit called an electrolyzer.

The effectiveness of electrolysis depends on the electrolyzer used. The most traditional technology is an alkaline electrolyte technology. A range of electrolysers are used to serve different purposes and achieve different goals, with common examples including polymer electrolyte membranes, alkaline electrolyzers, and solid oxide electrolyzes.

These technologies are increasingly popular because they can result in zero-emissions, depending on the source of energy used. Many experts believe that the electrolysis of water can be a truly viable solution over the coming decades  to produce hydrogen sustainably, in a cost-competitive manner and at levels that can meet demand cycles.

For example, in times of low electricity demand, excess energy is used to power electrolysis for the generation of hydrogen. The hydrogen is then siphoned off and sold to industrial clients for various applications, including, of course, the generation of electricity.

While the method sounds straightforward on paper, there are a few challenges that have to be overcome:

  • The first is to reduce the growing capital expenditure of electrolyers and improving the energy efficiency during the production of hydrogen from electicity
  • Secondly, the efficient splitting of water into hydrogen gas requires expensive metal catalysts such as iridium and platinum
  • Thirdly, hydrogen gas is highly combustible, and transporting it around presents several challenges

Many companies are committed to advancing the technologies and fuel cells to find a cheaper and more efficient means of producing and arguably more importantly, storing hydrogen. Countries around the world are funding further research, with the goal of increasing their clean energy capacity and integrating scalable models of hydrogen production from electrolysis. Countries across Europe such as Germany, The United Kingdom, as well as countries in the southern hemisphere such as Australia.

Wrapping Up

There is much ground left to cover ground to cover. The world’s majority of hydrogen production comes from fossil fuels, with only 0.7% coming from renewables. The production of hydrogen will become more economical in the years to come, so much so that it is expected to be competitively priced with natural gas by the year 2030.