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Tower of Total Thermal Integration

Page history last edited by jim mason 13 years, 4 months ago



See here for a full photo set of the GEK Hot TOTTI


The waste heat in output syngas and IC engine exhaust has tremendous potential for augmenting the thermally challenged processes in a gasifier.   By well recycling and reusing these "waste heats", we can remove the majority, if not the totality, of all the "thermal drags" on the combustion zone in the gasifier.  The result is higher combustion temperatures for improved tar cracking, increased tolerance for high moisture fuels, and increased gasifier efficiency.  (See here for the quantative numbers)  At the same time, we can eliminate the need for a radiator to dump otherwise useful heat at the end of the system.


The GEK Tower of Total Thermal Integration (TOTTI) demonstrates a powerful new method to achieve this full thermal integration of waste heats in a gasifier and IC engine system, and do so in a compact and easy-to-build form factor.  Full thermal integrations are common on large-scale gasification equipment   What is new here is a method and apparatus to achieve the same at the small and mid scale.  The usual attempt at this solution is to throw the entire kitchen sink at the problem-- building a long train of filters, exchangers and cooler components, all tied together with a mess of plumbing and condensate management.  And the result is always a complex expensive system only a government bureaucrat could love. 


ALL Power Labs now demonstrates the same can be achieved through an economical combination of counter-flow vessels, directly mounted to each other, without a large elaboration of redistribution plumbing or auxillary vessels.  All waste heat is reused and returned to approprate temp processes.   Cool things are made hot and hot things are made cool, in sync and in order-- thus there is no need for the usual radiator/cooler/condensor at the end to hide your "thermal sins".


The GEK Tower of Total Thermal Integration is the culmination of all our air preaheating, heated auger and PyroCoil work of late.  The picture and drawing at the top shows how various old and new GEK parts come together for the integration.   Here they are by number and function.


1.  Heat Exchanger #1, Auger Feed Drying Bucket:   Vaporize water out of incoming fuel with outgoing syngas.

2.  Heat Exchanger #2, PyroCoil:  Pyrolyze incoming fuel and heat resulting charcoal with IC engine exhaust heat.

3.  Heat Exchanger #3, Reactor/Gas Cowling:  Preheat incoming air with outgoing syngas.

4.  (Optional) Heat Exchanger #4, Cyclone with Steam Coil: 

Remove majority of particulates before drying exchanger to prevent soot clogging.  Raise filter water to steam for reinjection into reactor.   





Full Res version of TOTTI Thermal Relationships.pdf



The Auger Feed Drying Bucket is the newest component for the GEK gasifier system.  The Drying Bucket replaces the previous longer heated auger unit described here.  Unlike a typical heated auger design, the Drying Bucket mounts directly on top of the cyclone, and directs all outgoing gas heat to vaporize water from the incoming fuel.  Vaporized water rises up with a convection draft into the monorator hopper, and condenses out on the cool hopper walls.  In contast, water vapor liberated in a heated auger does not have anywhere to condense, and thus will still travel into and through the reactor, though with the vaporizing load helpfully removed.  Removing the water completely, then reintroducing it dynamically as temps and loads require should create a bit more flexibility.


A big concern when using gasifier output or IC exhaust to dry incoming fuel is to not get the fuel too hot and start torrefaction or pyrolysis in the drying vessel.  There is a fairly narrow band where temps are high enough to vaporize water (100C) and not too high where torrefaction and pyrolysis will begin (@200C).  Thus the TOTTI system is first tempering the output gas heat with air preheating and cyclone losses (potentially with steam coil), before the output gas enters the Drying Bucket double jacket. 


All this of course assumes you want to keep drying separate of pyrolysis.   We think this is important so shut down is not complicated by pyrolysis smoke, fuel to load matching is improved, and you can keep pyrolysis tars out of the drying condensate.  Continuous run units at constant load don't need to worry about this as much, though mixing of drying and pyrolysis in an auger can create a big sticky mess.  The DTU Viking unit, for instance, mixes pyrolysis and drying in the heated auger.  This is fine for research and modelling, but non-ideal for small scale start and stop type uses with real world operators.   Thus we've gone to a system where the auger stage is drying only, and pyrolysis is supported in a separate gravity fed downward stage.  The two are kept as separate as possible.  


There are many other subtle yet important details in which waste heats should be returned to where, as well as the orientation of physical components that will best realize the desired thermal relationships and flows.  The TOTTI is our best solution and likely final answer for establishing the correct total system thermal relationships, while also attending to the rest of the 3-D thermal-chemical-mechanical-gravimetric puzzle that is gasifier design.


See here for a full photo set of the GEK Hot TOTTI



Discussion for this article is in the GEKforum here.

Comments (2)

jay said

at 12:46 am on Aug 2, 2009

Jim, its a beautiful work of art and science. nice job. lets burn it.

Igor Pavesic said

at 2:27 pm on Aug 28, 2009

Jim, did you actually test this configuration with respect to tar elimination from the gas? The concept is similar to Viking (separated drying & pirolysis from oxydation and reduction) and they claim to have "tar free" gas.

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