Old power plants - new life with #pyrolysis pre-plant (Part2)

As already mentioned in the article (part1) from 2020, there is the interesting possibility of doing one thing and also doing the other ... Are you wondering what this means?

You operate a coal-fired power plant #CFPP that has been in operation for more than 30 years and are now considering whether to shut it down and replace it completely because ...

• the flue gas cleaning system is no longer state of the art
• burning fossil coal is no longer in vogue
• the economic viability is no longer given with increasing CO2 taxes

Status of the/your system technology

• Your fuel coal is finely ground in coal mills and then burned in solid fuel burners...
• The flue gas cleaning system is relatively simple and consists of perhaps 1 scrubber and filter system...
• The boiler system still works quite well, but is not a modern high-pressure system...

What could your thoughts be?

You would like to use biomass and would then at least have the problem with CO2 taxes under control. However, the existing biomass, e.g. rice straw, would have to be pre-treated to give it a uniform piece size that makes sense for handling. Pelleting is usually recommended...

Or do you have access to large quantities of hazelnut shells, coconut shells or olive stones? These are easier to use by simply grinding them, but they are actually an ideal raw material for the production of industrial activated carbon or #carbonblack for agriculture. Is incineration really the most economical solution?

But in the future, everyone will actually only want #hydrogen. "Can't I just hold out for a few more years and then close the plant?" you think...

A new-old solution?

A large-scale industrial upstream plant was built 20 years ago and operated at an old coal-fired power station. So the possible solution is not really new...

Materials with different grain sizes can be processed relatively well in an indirectly heated rotary kiln. This produces a good combustionable gas and a carbonate.

The hot process gas can be fed into the existing boiler of a #CFPP at 500°C and ignites immediately on contact with combustion air.

The carbonisate can now be either a high-quality biochar (from biomass) or a carbonaceous mixture (from unsorted waste). If the ash content is relatively low, this pyrolysis coke can also be fed into the existing coal bunkers and thus replace (part of) the fossil coal.

This means that I would only have to install a relatively small connection for the process gas line on the existing boiler and could continue to operate the rest of the power plant unchanged for the time being.

Why should I do it this way?

Depending on the process temperature of the pyrolysis rotary kiln, the permanent gas composition shifts from CO2+CH4 to CO+H2. This means that the same technology can later be used to switch to hydrogen production or syngas production!

Possible realization stages (Case 1)

1. Installation of a first rotary kiln module with connection to the existing boiler to demonstrate the proof of concept "fossil substitution".
2. Installation of further modules until the entire fossil fuel has been substituted.
3. Installation of a hydrogen separation system, which reduces the amount of energy in the process gas and thus enables the installation of further modules.

Possible realization stages (Case 2)

1. Installation of a first rotary kiln module with connection to the existing boiler to demonstrate the proof of concept "#syngas + #biochar".
2. Optimization of the process to produce high-quality biochar or activated carbon from biomass. This steam activation produces large quantities of syngas ( CO+H2 ), which is then burned in the existing power plant.
3. Expansion with additional modules until the maximum permissible combustion heat output is reached by the syngas. Fossil solid fuel is then no longer required.

Possible realization stages (Case 3)

1. Installation of a first rotary kiln module with connection to the existing boiler to demonstrate the proof of concept "#waste disposal + #hydrogen".
2. Optimization of the process for increasing the amount of treated #waste2hydrogen. The carbon contained in the carbonisate is inert and therefore a carbon sink...
3. Installation of a hydrogen separation system, which reduces the amount of energy in the process gas and thus enables the installation of further modules.

Advantages of this combination

• No complete demolition and expensive new construction.
• Continuous operation of the plant enables income during the changeover.
• The proven staff will be retained and only need to be trained further.
• Only after the proof of concept has been completed must a decision be made on the way forward.
• Depending on the market situation, it may be possible to switch to the more economically viable option.

By the way...

Biomass contains relatively much oxygen and comparatively little hydrogen. This is why hydrogen production always ends up producing CO2.

Significantly less CO2 is produced when using plastic waste, with the exception of PET.

If you are interested to discuss your case mail to [email protected] or send me an in-mail.