SAFETY IN THE GREEN HYDROGEN INDUSTRY

SAFETY IN THE GREEN HYDROGEN INDUSTRY

The role of green hydrogen within the framework of the European Commission’s strategy for the reduction of greenhouse gas (GHG) emissions and the economy decarbonization process will be decisive.

This article focuses on the green hydrogen facilities. We will briefly analyze, given the characteristics and properties of hydrogen, how the applicable concept of safety must go beyond merely complying with the legal requirements, industrial regulations, technical norms or design standards. Doing that will require the experienced use of advanced tools to identify, assess and manage risks, which will serve as support for administration and decision-making.

The goal of all stakeholders involved in the industry associated with green hydrogen (operators, users, administration, insurance companies) is to attain the highest levels of safety: both in design and engineering, and in operation and maintenance, ensuring the minimization of accidents at the facilities and, as a result, operational and business continuity.

The production of hydrogen and the strategy of the European Commission

Today, 95% of the hydrogen produced in the EU is obtained primarily from steam-methane reforming with associated CO2 emissions (approximately 330 g CO2eq/kWhH2)2. It is known as gray hydrogen or “fossil-derived” in the strategy of the European Commission3.

This process can be complemented with CO2 capture, use and storage to obtain blue hydrogen, which has a 70% – 90% smaller carbon footprint. Most of the remaining 5% of the current production is obtained as a byproduct of the chlorine-caustic soda industry, which uses alkaline electrolyzers.

The electrolytic method has experienced very quick growth as a result of community and national policies. But to classify hydrogen as renewable (green), the electricity must have that characteristic, reaching carbon footprints of less than 30 g CO2eq/kWhH2. With a certain dose of reality, the Commission identifies “low-carbon hydrogen” as having a significantly small carbon footprint, whether produced by methane reforming with capture or by partially renewable electricity.

Today, hydrogen is used primarily at refineries to eliminate contaminants and produce quality products to meet demand (33%), manufacture ammonia (27%) and methanol (11%), and produce steel through direct reduction of iron minerals (3%). A total of 64% of the hydrogen production is onsite, captive, used in processes at the same factory.

The objective of the European Green Deal is to reduce greenhouse gases (GHG) emissions by 50% in 2030, which requires a rapid decarbonization process in the economy. To do that, among other lines of action, the European Commission the European Hydrogen Strategy (COM (2020) 301 final) published in July of this year, under which green hydrogen production with water electrolysis using renewable electricity is the key technology that will enable the penetration in the energy system of growing quantities of it in different forms known as Power-to-X.

This strategy aims to make hydrogen an intrinsic part of an integrated energy system that would have, in 2030, at least 40 GW of electrolyzers producing 10 million tons/year, and in which hydrogen would be the primary pillar of a decarbonized energy system and the raw material for industrial processes such as synthetic fuel manufacturing.

Figure 1 shows this concept, in which the resources for obtaining hydrogen are diverse, from natural gas and biomethane to renewable electricity. The priority is, of course, that most of the hydrogen should be renewable (green), obtained through electrolysis with wind-generated and solar electricity, as that is the option most compatible with the objective of climate neutrality by 2050.

What are the most relevant properties of hydrogen regarding safety and other fuels?

Hydrogen is a nontoxic, colorless, and odorless gas, classified as an extremely flammable gas according to the applicable regulations. In fact, to trigger the ignition of hydrogen, it takes 15 times less energy than for natural gas. And the range of concentrations in the air in which hydrogen is flammable, with a flame visible to the human eye, is 10 times greater than for gasoline.

It has a very low density. It is 14 times lighter than air and 22 times lighter than propane (Figure 2), and it dissipates very quickly. In case of leaks, it rises and dissipates quickly (at over 20m/s), unlike, for example, with propane leaks or other fuels, which tend to gather near the ground as they are denser than air. In any case, explosion risk assessments including the appropriate measures (equipment suited for use in classified atmospheres, ventilation, etc.) must be conducted to guarantee proper prevention of the risks of explosion.

Hydrogen combustion has some relevant unique characteristics.

The self-ignition temperature, the lowest temperature at which a substance ignites spontaneously without the need for a spark or flame, is very similar to that of natural gas and much higher than gasoline vapor (Figure 3), which is a benefit in terms of safety.

Additionally, hydrogen has a wide range of concentrations in the air in which ignition can occur (flammability range, between 4% and 75% by volume), much greater than that of other gaseous fuels (Figure 4). However, the concentration of hydrogen from which the mixture is flammable (the lower limit of flammability) is greater than the concentration of propane and gasoline vapors, which is also a point in its favor in terms of safety.

The required energy, in optimal combustion conditions, to start combustion is much lower than for other fuels. So just a small spark could initiate combustion (Figure 5), which must be taken into account when putting together equipment that can act as potential sources of ignition, despite the fact that the high rate of dissemination plays in our favor, when necessary.

Finally, hydrogen combustion produces a flame that is invisible to the human eye, so gas and flame detectors are used, along with heat vision cameras to detect it. The need for this equipment is significant because the thermal radiation produced does not produce a feeling of heat, as it is mostly in the UV range.

These analyzed properties give the industrial facilities that generate, process, and store hydrogen a certain level of risk associated with vulnerable elements (people, environment, and industrial facilities or assets), caused by undesired events, meaning it is necessary to provide sufficient safety barriers, as well as adequate risk management to avoid them or minimize their potential consequences.

Safety management in the green hydrogen industry

The main goal of all stakeholders involved in the industry associated with green hydrogen is to attain the highest levels of safety: both in design and engineering, and in operation and maintenance, ensuring the minimization of accidents at the facilities and, as a result, operational and business continuity.

Given the characteristics of hydrogen mentioned above, the applicable concept of safety must go beyond merely complying with the legal requirements, industrial regulations, technical norms or design standards. It also requires the experienced use of advanced tools to identify, assess, and manage risks as support for administration and decision-making.

This criterion is applied currently by the operators of facilities that produce hydrogen by other means (particularly the ‘gray hydrogen’ produced with methane vapor) in refining and the chemicals and petrochemicals industry. The arrival of new players in hydrogen production in different sectors undoubtedly requires replicating the high standards of safety put in practice by these activities.

To reach these high standards of safety, a brief discussion follows on the primary tools available and applicable in managing risks in the industry in the different stages of the life cycle at the facilities (Figure 6).

Many of them are not only common practices in the industry, rather they are requirements of the insurance industry designed to minimize the risks of an undesired event or inability or stoppage in the process causing damage or losses of production.