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The dryer problem (was RE: [Biochar] Biomass energy from industrial food processing plants) #dryer


Paul S Anderson
 

Ian and Tom and Tom and others,

 

In Ian’s message below he raises some questions that I would like to understand better and to have answered about drying biomass prior to pyrolysis.

 

Agree, I've worked in both these industries.......... 

[PSA>>] Sugar cane and palm oil industries, right?   What other industries are with  similar challenges about drying the residue of industrial processing?    Probably many.   But let’s name them if we can AND make comments about if that industry could need biochar for its soils, etc..

Many operate on soils that are now becoming marginal. They could usefully invest some of their crop carbon in the ground, but it is a difficult discussion to have with the factory people (who can't see the point) and the field people (who don't believe it). 

Most pyrolysers make very poor driers.

[PSA>>] This is referring  to DURING the pyrolysis, having to much moisture content (MC) in the incoming biomass, right?   So the issue is to dry prior to entry into the pyrolyzer.    I am learning, so please feel free to correct or clarify any of my statements.

 

Drying in a spreader stoker is much easier.

[PSA>>] I just got a quick lesson on this at   https://www.youtube.com/watch?v=YTWzu9t80Mg  It is essentially putting the “damp” biomass fuel into the “burner box” (full combustion, gasification or pyrolysis) in appropriate quantities to have drying before the fuel gets to the areas of pyrolysis/burning.   That clearly works for some cases, but I think our issue is how to do the drying prior to (and probably separate from) the then-dried fuel entering the pyrolyzer.  

 

That separate drying seems to be what is mentioned in this next paragraph.

The Australians did work on a flue gas flash drier that could provide some of the answers. Ideally, you dry bagasse/FFB etc off the conveyor and then split the volatiles and solids in a suitable pyro.

[PSA]  Should we look more at this, and/or at other alternatives?  

 

Extract a biochar fraction for the soils then pulverise the rest and blow though the stoker and burn the gas through the sides - just make sure the superheater tubes can take it ! If the drying problem can be cracked then a 'front end pyro' could be fitted at a lot of installations. 

[psa]  Yes, how to crack the drying problem?   So much depends on the nature of the biomass feed stock.   Small pieces vs. fibers vs. larger pieces and even big stuff.

 

Maybe the  topic of “dryers” is too generic, and too “simple” as if to be a college course.   The issue is to have FUNCTIONAL low cost drying systems.   Pyrolysis / biochar systems can give off the heat.   How can it be used.

 

Paul

 


Ian McChesney
 

Yes, the challenge is to move these industries towards a bioenergy/biochar solution. 


Combustion systems in many agro-processing factories have been highly optimised to burn all the (wet) carbon they receive. In many situations an energy balance could be achieved by only burning ~85%. If these systems could be adapted/converted to deliver the other ~15% of the plant carbon as a usable char then large scale soil application might be possible. 


Pyrolysis systems targeted at the energy market are too complex and expensive and will not replace combustion systems in these factories. 


However, simpler thermal pyrolysis systems could be introduced alongside existing combustion systems to provide the necessary char adaptation and produce char feedstock at ~$100/t. Drying is one of the technical challenges to overcome.There are several process options to consider, and the necessary integration into an existing boiler range has to be engineered.  


However, at this price level (amended) char incorporation becomes a useful soil regeneration strategy - particularly if you can lift yields by 42% ….. IanMcC

 


Tom Miles
 

The technical potential exists but we don’t have good business models yet for commercial implementation.

 

So far large agricultural processors we have seen, like sugar mills and grain processors, have not chosen to add biochar to their thermal systems, even after spending millions on detailed engineering studies. The yields are not clearly demonstrated and the economic returns do not compel them to invest the capital. The exception is in China where the primary benefit is public health: carbonization and conversion to biochar based fertilizers is part of a subsidized strategy to reduce pollution from open burning of crop straws and to reduce severe contamination of 20% of the cropland. In that case the feedstock is already dry.

 

An ongoing study on sugar in Australia has demonstrated the technical feasibility but so far no impact on soil productivity. Work in the US and China has reported benefits that have not yet been monetized or implemented on a commercia scale.  In one case increases of  “theoretical recoverable sucrose (TRS) content yield improvement of 22.3% and 31.6% from control. Benefits of applying biochar to cane fields include an increase in soil carbon content, improvement to soil drainage and aeration, and addition of nutrients for the sugarcane crop. Economic benefits are expected for both sugarcane growers and processors through the production of valued byproducts from pyrolysis of sugarcane leaf residues and bagasse as well as enhancing the sugarcane industry’s footprint in renewable energy markets.” Activated carbon from sugar cane via hydrothermal carbonization has been shown to be useable in sugar processing. Promising but not commercially demonstrated yet.

 

For more than 80 years a US processor made furfural from oat hulls. The carbonaceous byproduct (50%C, 7% ash) was burned in a boiler for district heating. Furfural markets changes and production moved overseas in the early 2000s and local production stopped. The hulls are now burned in a university boiler. The carbonaceous product should have made a good biochar.  

 

Tom

 

 

 

From: main@Biochar.groups.io <main@Biochar.groups.io> On Behalf Of Ian McChesney
Sent: Sunday, April 12, 2020 5:15 AM
To: main@Biochar.groups.io
Subject: Re: The dryer problem (was RE: [Biochar] Biomass energy from industrial food processing plants) #dryer

 

Yes, the challenge is to move these industries towards a bioenergy/biochar solution. 

 

Combustion systems in many agro-processing factories have been highly optimised to burn all the (wet) carbon they receive. In many situations an energy balance could be achieved by only burning ~85%. If these systems could be adapted/converted to deliver the other ~15% of the plant carbon as a usable char then large scale soil application might be possible. 

 

Pyrolysis systems targeted at the energy market are too complex and expensive and will not replace combustion systems in these factories. 

 

However, simpler thermal pyrolysis systems could be introduced alongside existing combustion systems to provide the necessary char adaptation and produce char feedstock at ~$100/t. Drying is one of the technical challenges to overcome.There are several process options to consider, and the necessary integration into an existing boiler range has to be engineered.  

 

However, at this price level (amended) char incorporation becomes a useful soil regeneration strategy - particularly if you can lift yields by 42% ….. IanMcC