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Hydrogen has been an important basic material in the most diverse applications for over 100 years. Approximately 19 billion Nm³ of hydrogen are consumed annually in Germany (DWV 2015 (German Hydrogen and Fuel-Cell Association)). Refineries and the chemical industry are responsible for the greatest share of this usage with approx. 85% (DENA 2016 (German Energy Agency)). Of this approx. 30-40% are refinery processes, 25% is used solely for ammoniac manufacture (the worldwide share here is actually approx. 50%) and a further 20% is used in the manufacture of methanol.Due to changing energy politics towards a decarbonisation of the energy economy, hydrogen, which is being manufactured with low CO2 production processes where possible, is moving ever more into focus as an energy carrier. Apart from industrial use in the chemical, petrochemical and refinery sector, the primary approaches for future usage in this regard are the steel industry, the deployment of H2 through fuel cells for mobility, stationary applications and diverse portable applications.Even direct reconversion is conceivable but will not foreseeably play any significant role in the energy system in the next ten years. Other representative sectors such as the glass industry, semiconductor industry, plastics production, metal processing and the pharmaceutical industry contribute to less than 1% of hydrogen use (DBI 2020 (German Fuel Institute)).
Ammoniac production (Haber-Bosch process) for the manufacture of fertiliserAmmoniac is used worldwide as the basis for the production of fertilisers, urea and even explosives. Annual world production is approx. 160 million tons. Ammoniac is manufactured by means of the Haber-Bosch process. Ammoniac synthesis is thereby achieved from atmospheric nitrogen and hydrogen at a ferrous catalyser at pressures of some 150 to 350 bar and temperatures of some 400°C to 530°C, the consumption of hydrogen in the process is between 80,000 m³/h and 160,000 m³/h.
Methanol manufactureMethanol is the basic material for a multitude of chemical products but in addition its use as a substance is today deployed as an energy carrier. Fuel is produced from methanol with the “methanol-to-gasoline” technology. Methanol is also required in the synthesis of biodiesel and the anti-knocking agent MTBE. By means of fuel cells, electrical energy can be supplied. World annual production is approx. 50 million tons.Methanol is manufactured in catalytic processes from synthesis gas, a mixture of carbon monoxide and hydrogen in the ration of about 1:2. Depending on the process, operating pressures of 50 to 350 bar and temperatures of 200°C to 380°C are used.
Food chemistryIn the food industry, hydrogen is used in the hardening of vegetable oils. In this process liquid oils are transformed into solid fats (e.g. margarine). Hydrogen is moreover used for the preservation of foodstuffs. In this case the hydrogen, as a packaging gas, inhibits microbial degradation.
Fischer-Tropsch synthesis (manufacture of gasoline, diesel, olefin)Fischer-Tropsch synthesis is used for the manufacture of liquid hydrocarbons such as gasoline, diesel and olefins. In this industrial scale process for coal liquefaction through the indirect hydrogenation of coal, synthesis gas is initially generated from CO and H2 followed by the transformation into gaseous and liquid hydrocarbons. The process was used in Germany on an industrial scale until 1945 and current plants are to be found in coal rich countries such as South Africa, Malaysia, USA, China, India and Qatar.
Hydro treating processes1) Hydrodesulphurisation (HDS) / hydro finingWith hydrodesulphurisation (also known as hydro fining / hydro treating), middle distillates (kerosene / gasoil) are desulphurised by hydrogenation of the sulphur compounds. The sulphur is thereby transformed into hydrogen sulphide. The process runs at temperatures between 320°C and 360°C and pressures of 20 to 80 bar. This leads to a considerable reduction in SOx emissions.
2) Hydro metallization (HDM)In hydro metallization, heavy metals (such as Ni or vanadium) are removed from crude oil using hydrogen. 3) Hydro denitrification (HDN)With hydro denitrification, organic nitrogen compounds are hydrogenated and transformed into ammoniac. This leads to a considerable reduction in NOx emissions.
4) Hydro deoxygenation (HDO)With hydro deoxygenation, oxygen is removed from reactants such as light and heavy gasoline, diesel fuel, heating oil and vacuum gasoil through reaction with hydrogen.
The hydrogen requirement in the above stated hydro treatment is 20 to 100 m³/t per ton of input material.
HydrocrackingIn hydrocracking, long chain hydrocarbons are separated out to retain low boiling fractions for diesel and gasoline. The process introduces hydrogen to prevent the formation of solid carbonaceous deposits and increase the yield of saturated hydrocarbon. For process implementation, quantities of up to 500 m³ of hydrogen per ton of input material are necessary.
Hydro formylationsHydro formylation (also known as oxo synthesis, Roelen reaction) is a technically significant homogenous catalysed reaction in which hydrogen and carbon monoxide are adsorbed on alkenes and other suitable substrates. Products of hydro formylation are aldehydes. The aldehydes are as a rule hydrogenated to alcohols, which are used in a variety of ways as solvents or as intermediate products for manufacturing washing and cleaning agents, lubricants or softeners for plastics.
USE IN THE STEEL INDUSTRY
The manufacture of steel is today one of the most CO2 intensive industry sectors in Germany. Approx. 45 million tons of steel per year are currently produced. To date, steel production for the most part has been based on coal and coke processes for reducing the iron ore in blast furnaces. Huge quantities of CO2 are thereby released into the environment.There are various approaches to the climate-neutral shaping of steel production through the use of hydrogen. Hitherto, hydrogen has mainly been used in the manufacture of steel as a shield gas / inert gas in the blast furnace.Substitution of hydrogen for coal /coke as reducing agent in blast furnacesOne approach to decreasing CO2 emissions is the replacement of coal and coke by hydrogen as the reducing agent in the traditional blast furnace process. The first blast furnaces in Germany have been converted in terms of process and others are already being planned. With the conversion of the reducing agent to hydrogen completed, the operators are hoping for a decrease in CO2 of approx. 20% with this process (Thyssenkrupp 2020).
Direct reduction plantsA common alternative to the traditional blast furnace process is offered by the direct reduction of iron ore. Direct reduction plants based on natural gas have been established for many decades and are in use. Here, the iron ore is reduced to sponge iron at temperatures of 1000°C using natural gas instead of coal and coke whereby CO2 emissions are directly diminished. The hydrogen fraction as an admixture to natural gas can thereby be arbitrarily increased and according to a feasibility study, operation is also possible with 100% hydrogen.As a rule, the hydrogen used has thus far been extracted by means of natural gas steam reforming. In principle the hydrogen requirement in the steel industry can in the future also be covered by green hydrogen. By utilising direct reduction plants with green hydrogen a saving on CO2 emissions of up to 95% is possible in contrast to the traditional blast furnace process (DENA 2018 (German Energy Agency)). Through a complete substitution of the coal /coke requirement an additional hydrogen requirement will accrue in Germany of 2.4 million tons per year (LBST 2017 (Ludwig-Bölkow-Systemtechnik)).
The feature of hydrogen to store renewable energy very efficiently and to be environmentally friendly in deployment far away from electricity generators is one of the most important future applications in the area of mobility. In general there are three possibilities of using hydrogen as propulsion for transport. The direct combustion in normal engines as a substitute for gasoline and diesel, the use of fuel cells and the transformation of green hydrogen into synthetic fuel for use in internal combustion engines. In the area of transport, hydrogen is mostly deployed by way of fuel cell applications. Fuel cells use the reaction energy resulting from the reaction of hydrogen with atmospheric oxygen in a galvanic cell and convert it into electrical and heat energy.Because in so doing only water vapour is formed they can be used with versatility as highly efficient and clean electrochemical energy converters. The advantage of H2 fuel cell vehicles is in the high level efficiency of the electrical drive in comparison to combustion engines as well as in the shorter refuelling times and greater range compared to the battery. In just three minutes hydrogen cars can be refuelled with the emission-free fuel at these filling stations for a range of over 500 kilometres – a considerable advantage over pure electric cars. This applies in particular to larger cars, vans and urban local buses and HGVs. The technology in contrast to competing diesel power units is still comparatively expensive as the gas for achieving the equivalent ranges of diesel power units either have to be stored at very high pressures of up to 700 bar or as a liquid at -253°C which is bound with corresponding challenges on the technology. It is, however, already being successfully deployed in all areas of mobility – from cars, HGVs, buses, non-electrified rail traffic, aircraft and rockets to ships and submarines.In international aviation and shipping, from today’s perspective, due to the high level of demand on the energy density only renewable liquid fuels come into consideration as the alternative to fossil fuels. Hydrogen is thereby a central intermediate product.
STATIONARY APPLICATIONS / HEATING
Fuels cells work as small thermal power plants. They convert the stored chemical energy not only into electricity but also into heat. The combination also offers itself to decentralised deployment in residential buildings being heated by means of fuel cells which can simultaneously produce electricity. There are two fundamental approaches here for implementation in the area of buildings. One possibility is to furnish households with their own decentralised hydrogen supply from renewable energies.The second approach is a hydrogen admixture in the existing natural gas grid. The advantage of the hydrogen admixture is that in contrast to the first option the existing infrastructure can be used. An augmented variant in this respect is also the later replacement of natural gas with synthetic methane, manufactured by means of the power-to-X process. The admixture of hydrogen to a maximum tolerance threshold of 20% in the existing natural gas grid is technically, and if needs be, possible and has been researched for some time now (DVGW 2013). H2 admixtures of up to 10% have proven to be unproblematic. In Japan there are already many fuel cells based on natural gas in use and in Germany many prominent heating manufacturers are also already working on such systems.
One highly versatile area for the use of hydrogen in fuel cells is power supply as an alternative both to battery based power supply in the low power range (up to 50W) and engine powered electricity generation in the kW range. The smaller systems are characterised by the high energy content, the larger systems by their environmental friendliness. Thus with this technology not only can small devices like mobile telephones, portable computers, MP3 players and video cameras be operated efficiently but it also has an application for example in grid-independent power supply such as remote locations. With these larger systems the fuel cells as a rule constructed as a cell stack.
RECONVERSION OF GREEN HYDROGEN / ELECTRICITY PRODUCTION FROM HYDROGEN
Reconversion of green hydrogen can technically take place using the normal natural gas process for power generation, i.e. in gas turbines, combined cycle power plants or with combustion engines. This could have future application in particular during periods of increased power demand and lower renewable energy production.Gas turbines for use with pure hydrogen below 100MW are already available (Siemens 2019). However, there exists a need for further research to reduce the costs and make the availability of green hydrogen affordable.A hydrogen admixture in existing gas turbines or natural gas combustion engines is a possibility here to enable the economic operation of such plants in the short term even at lower capacity.A big challenge so far has been the supply with hydrogen for such plants. In this regard, supply and storage concepts are still to be developed in order to guarantee the delivery and storage of hydrogen in the direct proximity of the power generation plants.For this reason, the reconversion of hydrogen will not foreseeably be playing any significant role in the energy system for the next 10 years. Due to the huge technical advances of fuel cell engineering in recent years but also through the increased technical requirements on the operation of thermal engines, the energy-orientated use of hydrogen is predominantly seen to be in fuel cell technology.
Sources: DVGW 2013, DWV 2015, DENA 2016, DBI 2019, TÜV SÜD 2020