[Gasification] raising H2 concentration indowndraft gasification

Rex Zietsman rex at whitfieldfarm.co.za
Mon Dec 23 00:12:18 CST 2013

Hi All,

Firstly, I would like to reiterate my thanks to Tom Miles for hosting this list. The members have historically been good contributors and I hope that this will continue.

I think somewhere my original question of raising H2 output from standard gasification has taken a somewhat devious route back to here. So let me sum up so that we can all benefit from what has been said.
a. I am working on a demonstration plant that liquefies and catalytically cracks biomass molecules to produce an oil. 
  i. Biomass has the average composition of C6H10O5. When all of the oxygen is removed as CO2 we are left with CH2 chains of various lengths and a slight excess of H.
  ii. As hydrogen is released at the catalyst face, we also benefit from hydrogenation of the catalytically cut biomass chains to make deoxygenated oil. 
  iii. Longer chained oil is recycled for further cracking while shorter chains boil and leave as vapour.
  iv. The oil is a cross section of lengths, branches, rings, etc. and it contains some sulphur and nitrogen. To get it to Euro V standard requires hydrotreating using hydrogen

b. Besides this oil, we also have vegetable oil. Rather than going for FAME biodiesel, one can also hydrotreat triglycerides to form chemically similar diesel to that from crude oil. As there is a significant amount of oxygen in the triglyceride structure, it requires a lot more (up to 10x more) hydrogen than standard hydrotreating of transport fuels.

c. For hydrotreating we need hydrogen. We can buy hydrogen in cylinders or we can make it ourselves. Our plant typically requires about 30kg/hour of hydrogen to meet the hydrogenation requirements. 30kg/hour is not particularly big but big enough to consider onsite production. As we are processing biomass, the thought was to harvest hydrogen out of gasifier syngas. If we do this, what size gasifier do we need? 

d. Gasifier size will depend on how much hydrogen we can produce. The typical method is to produce a syngas with say 30% H2 and about 30% CO (good quality gasifier). After washing and cleaning the syngas, we can compress and reheat it before passing it over a water gas shift reactor to convert most of the CO to CO2 and H2. This is on a mole for mole basis meaning that we would almost double our hydrogen concentration in the post WGS gas. At this point, the gas is cooled and run through a PSA. Note: there are hot H2 membranes coming out on the market which could allow hot H2 removal and allow the hot raffinate gas to go back to say a charcoal gasifier as suggested by P.V. 

e. An alternate view is not to go via WGS but just to harvest the H2 directly from the syngas. The raffinate gas can then be fed to the onsite diesel generator through the air intake. CO plus any residual H2 from the PSA will then be combusted and help provide power to the facility. This route saves the cost of gas heat exchange and the WGS reactor. 

This all brings me to my question: how can we tweak a conventional gasifier to produce a higher concentration of H2 in the syngas? To my mind, Kevin has basically hit all the high points:
1: Dry the wood.
2: Preheat the wood.
3: Preheat the air.
4: Add superheated steam to the air

To this I speculated on using slightly enriched air by raising the O2 concentration to 28%. This effectively removes 25% of the starting N2 in the air thereby reducing the dilution factor. Tom Reid then made the suggestion to gasify only the cellulose and allow the lignin to leave as biochar. Another practical and easily implemented suggestion when running a standard gasifier.

I thank you all for your contributions. I wish everyone a wonderful holiday season and hope that 2014 will be the best year ever!
Kind regards

From: Mark Ludlow [mailto:mark at ludlow.com] 
Sent: 22 December 2013 02:16 PM
To: 'Discussion of biomass pyrolysis and gasification'
Subject: Re: [Gasification] raising H2 concentration indowndraft gasification

Thank you P.V., for condensing (as it were) the various issues and pathways. Rex is shooting for the œuf d'or (golden egg) of gasification: FUEL. Well, I think he has been quite forthcoming and we should not expect open disclosure of every detail. The economic importance of such a system is substantial, as we all must realize. Somehow, I believe that Rex may make it to the finish line, largely because his enterprise is not larded-down with public or sugar daddy funding; and also because he is very smart and clever. Go for it, Rex!

Lists of all kinds are viable because of the generosity of their members (The inevitable holiday tie-in!) There is room for everyone at the table but it’s a potluck. We bring, share with all, then leave with a full belly.

Thanks to Tom Miles, especially. This is his list. However, his generosity, knowledge, experience and even-handedness makes all of us empowered.

Happy Holidays to All,

From: Gasification [mailto:gasification-bounces at lists.bioenergylists.org] On Behalf Of Pannirselvam P.V
Sent: Sunday, December 22, 2013 2:25 AM
To: Discussion of biomass pyrolysis and gasification
Subject: Re: [Gasification] raising H2 concentration indowndraft gasification

Greetings to Rex and all list members 

Happy holiday  Xmas, New year  to  All the list members 

We have  very   good  open  technical information exchange here    and a special happy holiday greetings  to   the  very  well organized technical  team members of the list , well managed  by our  Word wide  list Coordinator     Tom Mile , make possible all about  biomass  gasification in one place , the image ,videos, all the list members  many  text comments  in  an organised , easy to acess from anywheer from any time .

Very Important  unsolved  Gasification  design problems 
   Coming to the very good topics REX has brought here , we need  to realy break this silence  of many list members as the topic is  very , very importante one , need  active atention of all list members , not silence one can expects .

The h2 rich  syngas 
     The  hydrogen rich    syngas  can be obtianed using pyrogas , charcoal  with recycled  syngas  at  high tempertaures  above 800, as C02  will be reduced , some methane may be there,

The carcoal can help to reduce  c02 , as well  provide energy needed , as already pointed out by REX 

This  hydrogen  rich gas   can be used for bio oil enrichmento  to  make  valuable  biocrude   using mixed  catalyst as one  with Ficher tropics Fe  as outline to make  oil from c02 , as well as bio oil  leaving  ,syngas   without the h2 ,  as this can be  recycled   back   to   make h2 rich syngas from pyrogas  as described aboove 

Thus there is syngas loop , and there is no  need to worry about PSA  C02  problemas .

Thus pyrolysis can play key  role   along  with  charcoal  gasification routes for syngas .Use of steam to increase the h2 is also need to be done as very well  outilned by Kelvin  and Tomm need .The heat needed  all can be obtained using  syngas  and steam production too depending on the local demand 

Syngas loop proven technology 

Syngas  recycle to  biomass  gasification  to make  methanol  via hygenol  is already proven  to be viable to make methanol , howvever  syngas use to biomass   gasification  can be more complex one.As pyrogas is  is the route , as you prove the h2 requirement is less, this  new  h2 enriched  gas without any need using only pyrogas and recycled gas  with charcoal  can make possible  the h2 needed to make decentralised  biomassrefinery production to make  biooil crude oil, biochar ,syngas  in a integratedway 

Small  biorefinery from biomass  need not be very big  and complex
     As this innovative  process design   is very complex, Rex , one cannot expect  more idea,  thus more silence from  list members is taking place.Even list coordinatior usual comment from Tom ,what all  list members can expects. One of  our list  the best   Technical  expertTom  Reed   , his very long year of practical  experience  need to becombined with  your projects..

Small Biomass refinery need To  energy products  need  to practical proven one 

Already one  company from Europe sell comercialy via linkedin group , a system to make  biocrude oil  wirth mechanical contact direct catalytic hydrogenation  of biomass. The required h2 is obtained from fractionationation  of biooilcrude oil ,as outlined by  REX. More information  about this comercial process  is available via linked in social Netwok .

Innovation with  ideas via Brain storming of all  is an urgent need,  not the silence 

We need   more ideas, sugestion from young list members , not silence as unexpeted from REX, as even  very bad idea, sugestion can help to find the correct best innovative path .The brain storming by severl list members , not silence,  can be  made possible. We ,the list members  all are very  well  conected by list Many , all  all know the basics of biomass, gasification . Even the  new one   can learn very fast  ,as chemistry  behind the technology  is well  explained her  our expert Tom Reed  make  more clear  the required chemical pathway in order to  make the technology  outlined well  too as the design  requirementos .Thus  sure new 2014  we  can solve the   pyrolysis combined gasification  as small birefinery   for energy the required design  problems ,clearly well defined by REX. The solution related to enegy problems  given by  Kelvins. The science  required by  Tom Reed, as  we small chemical engineering research group , the recycle process needed for process synthesis.

thus innovative proces  need both process design problems, process synthesis, process analysis.All can innovate ,give ideas as silence  make one pasive , let us all be ative as the per coreect wish from REX and list coordinator 

King regards

Pannirselvam  P.V

Research Group ,GPEC, Coordinator Computer aided  Cost engineering
DEQ – Departamento de Engenharia Química
CT – Centro de Tecnologia / UFRN, Lagoa Nova – Natal/RN
Campus Universitário. CEP: 59.072-970;North East,Brazil
pannirbr at gmail.com

On Sun, Dec 22, 2013 at 4:26 AM, Rex Zietsman <rex at whitfieldfarm.co.za> wrote:
  This message is eligible for Automatic Cleanup! (rex at whitfieldfarm.co.za) Add cleanup rule | More info

Dear Tom and the List,

Happy holidays to all and merry Christmas for the 25th.

Believe it or not, but we are going via liquefaction and catalytic cracking
aided by in situ hydrotreating and deoxygenation of long chain hydrocarbon
molecules all in one reactor. We produce a decent deoxygenated oil, not
pyrolysis oil. Low yield - only about 250 litres/ton of 15% MC biomass. When
tested via the ASTM tests for diesel, it has a longer tail at both high and
low boilers - easily fixed with fractionation. But, if the starting
feedstock contains sulphur, the residual sulphur is about 10% of the
incoming. This can be as high as 500ppm in the oil which is fine for
"standard" diesel. To make ultralow sulphur diesel we have to hydrotreat.
Hence the hydrogen requirement.

In one of our projects, we have waste vegetable oil at a good price. The
idea is to deoxygenate this oil to produce a diesel similar to that from
crude oil. Here the hydrogen requirement is high in the range of 30kg/ton.
As it is still relatively small ie 1200 litres/hour, we need 30kg/hour of
H2. Hence the post.

All the best

-----Original Message-----
From: Thomas Reed [mailto:tombreed2010 at gmail.com]
Sent: 21 December 2013 12:07 AM
To: Discussion of biomass pyrolysis and gasification
Cc: <gasification at lists.bioenergylists.org>; John M. Bradley; Chuck
Subject: Re: [Gasification] raising H2 concentration in downdraft

Dear Rex and All;

Merry Xmas and happy synthesizing.

Rex must be a chemical engineer because he has outlined the problem nicely

A partial solution is reaction of only the 80% cellulose in the wood to make
a synthesis gas:

C6H10O5 + 1/2 O2 ===> 6 CO + 5 H2

And leaving the 20% lignin behind as charcoal (Biochar) for soil enrichment
and atmospheric CO2 reduction.

Reaction of part of the CO with water reduces the unbalance to an excellent
synthesis gas:

 6 CO + 5 H2 + 3 H2O ===> 3 CO + 8 H2. ||   ==> 3CH2 (oil)  + 3 H2

Leaving enough excess H2 to drive the reaction forward.  Toplit Updraft
gasification consumes the cellulose , leaving the lignin as Biochar.


I am an expert in molecular sieves, and have made a quantity of a Fischer
Tropsch catalyst with one isolated Fe atom per unit cell.  Should make a low
MW diesel.


If anyone has the means, and would like to pursue this, contact me privately
with an offer.

Tom Reed

Dr. Thomas B Reed
280 Hardwick Rd
Barre, Ma 01005

> On Dec 16, 2013, at 2:56 AM, "Rex Zietsman" <rex at whitfieldfarm.co.za>
> Hi All,
> We are looking at a system that will hydrotreat bio oils from
> pyrolysis, catalytic cracking and vegetable oil. For this we need in
> the region of 30kg hydrogen/ton oil. At small scale ie 1 ton oil/hour,
> this works out at, you guessed it, 30kg of hydrogen/hour. As this is a
> small amount in the overall scheme of things, we are looking at
> gasifying wood chips and to recover the hydrogen using pressure swing
> absorption. What I would like to know is whether we can increase the
> H2 concentration in syngas by tweaking the gasifier. Clearly we can
> look at the water gas shift reaction but, as the syngas has to be
> cooled, washed, pressurised and reheated, it is quite an additional
> investment for the scale we are looking at. If we could simply up the
> H2 content, we would go straight from washing to PSA. Residual gas
> would be piped to a diesel generator where CO and the like will be
combusted prior to exhaust to atmosphere.
> For easy mental arithmetic, let us assume a 33% H2 concentration in
> dry syngas. 30kg/hour of H2 is 15kmol/hour or 15/0.33 = 45kmol/hour of
> syngas. A kmol of gas has a volume of 22.4 Nm3. So, to get 30kg/hour
> requires 22.4 x
> 45 = 1000 Nm3 syngas/hour (mental arithmetic here, go with the flow).
> Assuming an 80% PSA recovery this means that we need 1250Nm3/hour of
> Not a bad sized downdraft gasifier! Assuming 6MJ/Nm3, this is around a
> 2MW thermal unit. If we can get the H2 concentration up to say 40%,
> then the syngas requirement would be 37.5kmol/hour or 37.5/45 x 1250 =
> roughly 80% of
> 1250 or roughly 1000 Nm3 syngas/hour. This reduces the size of
> gasifier to 1.6MW thermal and more sensible in size.
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