CGEN - ecologically advanced power generation

Hydrogen Power Plant - In a nutshell

7. Hydrogen Purification

Hydrogen has numerous applications in refineries and production of other chemicals like ammonia. Hydrogen is expected to play an increasingly important in our economy in sectors like transportation, decentralized electricity production, etc.

In order to become commercially useful, the hydrogen concentration must be raised above 99.9%. This is done using molecular sieves in the purification plant. The pure hydrogen is sent via pipelines to the consumers.

The residual gas from this purification operation is sent to the gas turbine.

1. Fuel Preparation

Gasifiers can process low-grade fuels that might not be suitable for use in conventional power plants.

The C.GEN projects will gasify solid fuels, mainly imported coal, which could be blended with petroleum coke and clean sustainable biomass, like wood waste, cereals and slurry.

6. Gas Purification

After the shift reactor, the gas consists mainly of carbon dioxide and hydrogen. Any sulphur which was present in the fuel by nature, will also lead to the formation of a small quantity of H2S gas.

The gas purification plant removes practically all the H2S as well as most of the carbon dioxide from the syngas through a process of washing with an organic solvent. The solvent itself is regenerated by pressure-relief and heating, thus releasing the carbon dioxide or the H2S gas for reuse.

Carbon dioxide is then compressed for further treatment and H2S gas is converted into pure sulphur and water vapour. The sulphur, in its basic form, can then be used as a raw material in the chemical industry (e.g. for production of sulphuric acid).


	Click on a step in the proces to learn more about it. Move the mouse over the materials to see more details in the left pane of the screen.

4. Syngas Purification

Fine dust particles (fly ash), present in the syngas from the gasifier are trapped by ceramic filters, whereas other constituents, such as ammonia, are washed out with water in a scrubber.

3. Gasification

Oxygen and fuel are blown into the gasifier. This is a tank with an internal pressure of 45 to 70 bar. The amount of oxygen blown in the gasifier is not sufficient for complete combustion of all the fuel. Instead, the conditions of pressure and temperature together with the incomplete combustion in the gasifier leads to production of a synthetic gas (syngas), consisting mainly of carbon monoxide (CO), carbon dioxide (CO2) and hydrogen (H2).

2. Oxygen Production

Oxygen and Nitrogen, the two main elements in ambient air, are separated from each other in an air separation plant. Only the oxygen is sent to the gasifier.


	Sulphur
	The sulphur leaves the residual gas installation in the form of powder or lumps and is stored in a closed silo before transport. In the chemical industry, sulphur has many uses as a raw material for various compounds. Large consumers of sulphur are found in the production of sulphuric acid and in the rubber industry, where it is used for vulcanization.


	Mains network The hydrogen power plant generates 400 – 450 MW electricity while emitting very low quantities of CO2 emissions compared to conventional power plants.


	Slag
	The solid fuels also contain incombustible constituents such as sand, clay and minerals. About half of these will melt and stick to the walls of the gasifier, where they will flow down slowly into a water bath, to form glassy flakes or slag when they cool down. The solidified slag locks up a number of impurities, present by nature in the solid fuel and protects from ever releasing them back into the environment. The slag is stored in closed silos and transported by ship. This product has many applications in the construction industry like concrete production and road-building.


	Fuel
	Type composition (in % by weight) of e.g. coal

	Moisture	6 to 14 %
	Ash	4 to 16 %
	C	56 to 72 %
	H	2 to 6 %
	O	2 to 12 %
	N	0 to 2 %


	Composition Hydrogen - CO2

	H2	52 to 54%vol
	CO	3 to 4%vol
	CO2	38 to 42%vol
	N2	1 to 6%vol
	H2S	0.2 to 0.6%vol
	H20	0 to 0,2%vol

	(%vol means percent by volume)

12. Pipeline

Hydrogen is a form of energy that enables an environmentally friendly energy production (e.g. from hydrogen electricity power stations), transport (e.g. via pipelines) and consumption (e.g. via fuel cells).

Hydrogen makes it possible to better integrate low- CO2 energy sources in the future energy system, which will be less dependent on natural sources, such as petroleum and natural gas.

5. Shift Reactor

This is a tank filled with a catalyst through which the syngas is passed. The carbon monoxide present in the syngas and the water vapor are converted into carbon dioxide and hydrogen. This reaction also produces a certain amount of heat.


	Fly Ash
	The other half of the incombustible constituents is converted into fine inert particles, the so-called fly ash. These are entrained out of the gasifier along with the gas flow and then captured downstream. The fly ash is stored in closed silos and taken away by ship. Dry fly ash has many useful applications in the construction industry. It can, for instance, be mixed with cement which improves the mechanical properties of the cement. Use of the fly ash reduces the need for conventional raw materials and thus allows the cement industry to realize substantial energy savings.


	Composition Air

	O2	21%vol
	N2	78%vol
	Ar, CO2 etc	1%vol

	(%vol means percent by volume)


	Composition Syngas

	H2	14 to 22%vol
	CO	16 to 52%vol
	CO2	2 to 8%vol
	N2	0 to 8%vol
	H2S	0,1 to 0,5%vol
	H2O	20 to 60%vol

	(%vol means percent by volume)


	Air emission

	N2		75%vol
	H20		11%vol
	O2		11%vol
	CO		1%vol

	(%vol means percent by volume)


	Composition Hydrogen - N2

	H2	56 to 60%vol
	CO	3 to 4%vol
	CO2	3 to 4%vol
	N2	28 to 32%vol
	H2S	traces
	H20	traces

	(% vol means percent by volume)


	Composition CO2

	CO2	98 to 99%vol
	CO, H2 etc	1 to 2%vol

	%vol means percent by volume