Gasification - Science topic

It great Dr jose. Means we are not on wrong track.

Thank you so much for your valuable insights over the concern.

I also wanted to extant the discussion,

As I have to know about quality of biochar through pyrolysis ?

As of now I don't have experimental experience into biochar production. However I heard about that pyrolysis may a feasibly way to produce biochar to use as biofertilizer.

Work out the air consumption required to completely oxidise the C, H, N, S, on a molar basis etc to their oxides, exactly. Knowing the number of moles of O2 will give you the necessary no. of moles of air. That is ER=1, then from the required air consumption for ER=1, multiply by 0.2 to get the air flow. You can reference it from moles to 1 kg of feedstock.

You can't have only a biomass tream in and no gasification agent. You're missing multiple parameters if "PYRO1" is your gasification unit. Plus there are a range of conditions that need to be stated and reactions to solve to equilibrium. You do not have a valid model.

You've taken a standard approach to a gas-solid reaction. Gasification is much more complex involving equilibrium reactions, the CHONS composition of the material to be gasified, taking account of tar formation, char formation and the gasification temperature. You need to look at papers on gasification to understand the overall process. Countless papers and reports on this topic and if you look even some free Gibbs free energy models for the basic reactions. I developed a Gibbs Free Energy model taking into account the gasification agent (O2, CO2, H2O, N2), its composition and temperature, tar formation and composition of the tars and char formation in the elemental balance and several reactions to model the final equilibrium gas composition. It takes time to set this sort of model up, but its more accurate.

For the classification of the various biochar production methods, I consider that the concepts of the combustion, pyrolysis and gasification operations involved must be taken into consideration, which in one way or another lead to the quantity and quality of the product obtained. In this, the stoichiometric equations until reaching the Boudouar equation 2CO → CO2 + C, is the main aspect. This is achieved by controlling the reactions that take place during the decomposition of biomass into liquid and gaseous compounds, the reactions that take place between the solid, liquid and gaseous phases, the control of the temperature and the configuration of the fluid displacement zone. . In general; Pyrolysis is the thermal degradation of biomass in the absence of an oxidizing agent, it is a thermal transformation process in which it is possible to obtain solid, liquid or gaseous products and, on the other hand, it is the first step in the processes of gasification and combustion. With the configuration of the fluid displacement zone, the time factor necessary for the stoichiometry of the reactions is regulated.

The error message you're encountering in Aspen Plus indicates that the specified equipment exceeds the allowable temperature limit for the materials used in the shell and jacket. To resolve this error and properly size the gasifier and decomposer for your sludge gasification simulation, you can take the following steps:

Remember that accurate material properties, proper modeling, and a good understanding of the process are crucial for successful equipment sizing and simulation in Aspen Plus. Additionally, always ensure that your chosen materials and equipment are suitable for the high-temperature conditions you are working with in your sludge gasification process. Delaram Bayat

It appears to be an ill-posed question, Syngas is synthesis gas composed of CO + H2 gas that gets converted to liquid hydrocarbons in Fischer-Tropsch process. If one has already a plastic, depending on the nature of plastic, one can get in thermal process, liquid fuel I am unable to understand why fluidization and then why nirogen. These are my thoughts. I cannot say more.

Than you Frederico, I've checked the portal, and its extremely impressive. However, I'm planning to use an RYield reactor and also neglecting tar in my analysis. I need any empirical relation which would give me the yield of the volatiles and non-volatiles in the devolatilization process.

A fluidized bed reactor would be the best choice for the decomposition of plastics like polyethylene before gasification. It offers efficient heat transfer, controllable residence time, enhanced mixing, and the ability to handle various feedstocks, making it ideal for effective decomposition of polyethylene before further processing into valuable products like syngas.

It is mandatory to maintain the equivalence ratio for the gassification system in the range of 0.2-0.4, if this value goes below 0.2 the process turns towards pyrolysis and in contrast if this value goes above 0.4, the process will shift towards combustion due to presence of excess air in the surrounding because equivalence ratio is the ratio of mass of air to the mass of fuel.

To obtain the yield of hydrogen gas from biomass gasification, you can follow these steps:

Yield of Hydrogen Gas (%) = (Mass Flow Rate of Hydrogen Gas / Mass of Biomass Feedstock) x 100

It is important to ensure the accuracy and reliability of the measurements, calculations, and assumptions made during the process. Additionally, consider any variations or uncertainties in the gasification process and take them into account while interpreting the results.

In Aspen Plus, you can set the percentage of oxygen as desired by specifying the composition of the gasifying agent in the input streams. This allows you to simulate different scenarios and investigate the effect of varying oxygen concentrations on the gasification process.

In real life, the percentage of oxygen in the gasifying agent can be controlled to some extent depending on the specific gasification system being used. In some gasification processes, pure oxygen or oxygen-enriched air is used as the gasifying agent to enhance the reaction kinetics and increase the overall efficiency of the process. This approach allows for better control over the oxygen concentration.

There are various oxygen production methods available, such as cryogenic air separation, pressure swing adsorption, or membrane separation, which can provide high-purity oxygen. These methods can be employed to achieve the desired oxygen concentration for gasification purposes.

However, it's important to note that the practicality and cost-effectiveness of using high-purity oxygen may vary depending on the specific application and scale of the gasification plant. Factors such as the availability and cost of oxygen, process requirements, and overall plant economics need to be considered when determining the oxygen concentration in real-life gasification systems.

Your are modelling on ASPEN PLUS?

Modeling the effects of Na2CO3 as a catalyst for hydrogen production through the gasification of peanut shells in supercritical water conditions involves considering several factors. Here's a step-by-step guide on how you can approach this:

Remember that modeling chemical reactions is a complex task, and the effectiveness of the model heavily relies on the quality and comprehensiveness of the experimental data. It is recommended to consult with experts in the field and refer to existing literature on gasification and catalyst effects to enhance your understanding and improve the accuracy of the model.

Hello Reza Karimi Ahmadi .. I am trying to solve a similar problem as yours in ANSYS FLUENT. Did you find the solution to this problem. It would be a great help if you could share it with me.

Regards

To vary the equivalence ratio (ER) in Aspen Plus, you need to change the amount of oxygen fed into the gasification reactor, which can be controlled by adjusting the process specifications in the simulation. You can specify the amount of oxygen fed into the reactor as a function of the biomass feed rate, and then vary the biomass feed rate to achieve the desired ER.

To do this in Aspen Plus, you can create a simulation of the gasification process and set up a reactor block with the appropriate reaction scheme. Then, you can specify the mass flow rate of oxygen into the reactor block as a function of the biomass feed rate, and set up a parametric table to vary the biomass feed rate and thus the ER.

There are several tutorials and articles available online that can help you get started with using Aspen Plus for gasification simulations. Here are a few resources you may find helpful:

These resources should provide you with the basic knowledge and skills needed to model and simulate gasification processes in Aspen Plus and vary the equivalence ratio by adjusting the oxygen feed rate.

Dr Ali,

Check out the EES modelling of biogas gasification by Felecia Fock and other researchers:

I understand your question as that you're wondering why the H2 concentration is low at very high S/B ratios. You're not taking about H2 yield, are you.

I'm not an expert for gasification, but I think, you find the answer when considering the steam reforming reaction.

CH4 + H2O = CO + 3H2

Biomass is not exactly CH4, but it reacts in a similar fashion. C is oxidized by water which releases H2. High S/B ratio means, you have only few C. As soon as all C is oxidized, you cannot get more H2, regardless of how much more steam, i. e. water you add.

However, I expect that the H2 yield is better at high S/B ratios.

Hi Jorge jadid Tamayo Pacheco I am also going through the same problem. Have you found any solution yet?

Yes, it is necessary to have inert bed material in bubbling fluidized bed reactors. The inert bed material helps to ensure that the fuel particles are evenly distributed throughout the reactor and that they do not settle and accumulate in one area. Additionally, the inert bed material helps to reduce the risk of the fuel particles burning too quickly and creating hot spots within the reactor, which can lead to explosions. The inert bed material also acts as a heat sink, helping to dissipate heat generated by the fuel particles and maintaining a more even temperature throughout the reactor. Finally, the inert bed material helps to reduce the risk of the fuel particles sticking to the reactor walls.

I do not see the problem. It is endothermic. You need to provide heat. To maintain the endothermic reaction at higher temperature, if thermodynamics says you need larger heat to maintain the temperature, it is so. The specific heats of various species will increase with temperature and H20 has higher specific heat and that is why you are getting what you have got.

Dear Mo Gamal

i have attached the file related to your question i recommended you to review it. you can better understand your query.

Regards

You must appreciate that Chemkin is a gas phase analysis tool - equilibrium, kinetics, flame propagation. If coal is intended object, it is a solid. Depending on the heat flux back to the solid and the environment - whether it is oxidative or otherwise, the gas phase has various chemical compounds - in fact very large number of them measured in experiments. From these, you can extract the initial composition which can be used for further analysis. It is important to define what you are looking for from coal related work. More cannot be said because you have not defined your problem in completeness.

Hi Katerine,

It depends on the definition of energy efficiency. You can assume a boundary for the process and determine inlet and outlet energy streams.

Inlet energy streams could be biomass (m [kg/h] * LHV [kH/kg]), heats added to the system through steam or other sources, pumps power, etc.

The outlet energy streams are the produced energy in the form of syngas or hydrogen and work produced through a turbine.

Another indicator of the process performance is the Levelized costs of hydrogen (LCOH), which indicates the costs of 1 kg of hydrogen production.

Please see this paper for more information:

Regards,

Abdollah

Dear

Thanks for your help!

For the stoichiometric air/fuel ratio for the combustion I calculate it according to the methodology of Lora & Happ (2002), in which it is expressed as a function of elemental analysis.

VO = 0.0889(C+0.375*S)+0.265*H-0.0333*O

Vo = theoretical air volume

C = % of carbon present in the sample

S = % of sulfur present in the sample

H = % hydrogen present in the sample

O = % oxygen present in the sample

The composition is dependent on a number on number of parameters, just to mention a few: Biomass type, gasification temperature, gasification atmosphere, reactor type and size, moisture content, oxygen content aso... .

Up to me it is impossible to give a numerical solution for this but You can search the litterature and make some estimations. Another way is to collect the gas and analyze it on a GC or GC-MS.

Generally, gas bags are used for measuring concentration, and are not suitable for volume measurement. You should use a flowmeter before the bag inlet. You might of course weight the bag (you calculate density from the chemical composition).

To answer to the other question: yes, generally gas bags can work with slight over-pressurisation.

Shekinah Harry Simulation of pyrolysis is shown in these videos how you can perform on aspen software and there are many online on youtube as well

The Benfield/Catacarb process (same process with 2 different names) is a proven way to remove all/most CO2 from a gas mixture

Change the operating conditions

Hi ,

Thank you for your response. I solved this error by increasing iterations but I am not sure what effect does it have on a process.

Find this paper

The numbers are the LHV of each gas component expressed as MJ/Nm3. That is, H2 has a LHV of 10.78 MJ/Nm3, CO has a LHV of 12.63 MJ/Nm3 and so on.

H2(%), CO(%)... are the content of gaseous products in the producer gas (vol.%).

The difference between the LHV and the HHV is the heat of vaporization of the water. In systems where you can't take advantage of the heat of vaporization of the water, it makes sense to use the LHV.

For such organic residues insoluble in organic solvents, the only solution to remove them is aggressive oxidation. You can try a mixture of potassium dichromate and sulfuric acid or a mixture of nitric acid and hydrochloric acid (aqua regia).

Perhaps you are partially oxidizing the coal creating a char phase which is heavier than the original coal because it has been oxidized but not yet vaporized

Technically you do not need steam to gasify straw. :)

However, it depends on what product you want to optimize gasification for. Then the selection of the steam-to-biomass ratio will be one variable, along with temperature, pressure, type of gasifier, air, etc. Can you provide more information? Then maybe more specific answers you will receive.

I am a little bit puzzled why you want to add a steam turbine in a small scale system? The smaller size, the lower efficiency and higher specific cost.

The heat losses and the by-pass losses over the turbine blades are proportionally higher, the smaller the turbine is. Since small turbines have more material (the weight of the material the turbine is made of) per capacity, the material is often of lower quality (lower temperature and pressure) and hence the turbine has lower efficiency.

Why not go for a gas engine with upto 40 % electric efficiency in scales down to 100 kW? Or a recuperative microturbine where some of the heat is used to pre-heat the combustion air.

Subasgar Kumareswaran i do agree with the comments of Moayyad Shawaqfah and perfect answer thanks

In the process of biomass gasification, tar is an inevitable byproduct. Tar exists in gaseous state in high temperature, uniformly mixed with the gas products. ... (2012) carried out a two-stage air gasification experiment using sawdust particles, and analysed the composition and contents of tar.

https://www.sciencedirect.com › pii

Experimental study of biomass gasification with oxygen-enriched ...

I think pyrolysis is a suitable method to handle this kind of waste. It has several advantages over other thermochemical conversion processes. It requires small size equipment volume, investment scale cost is meager, and takes less space than other thermochemical conversion processes.

Il faut déshydraté les feuilles

I expected relevant data to be available in the literature. However, I am thinking about the equilibrium model. The lack of equilibrium constants is not a problem when using Aspen. But treating the oxidation of carbon and carbon monoxide as reversible is unacceptable to me. It is also not understood to analyze a linearly dependent system of chemical reactions. I also have doubts about the second publication, where only the reaction rate constants are given. Were all the reactions mentioned in the publication first-order?

You can follow the following paper, maybe can get ideas

Dear Tan Phat Nguyen

ok. In my opinnion you have to take a look in the literatur:

(for example)

i would do a cfd simulation phase by phase (reduction, oxidation zone etc.) and input and output zone by zone.

so you can make a model based on equations zone by zone. than your input in first should ok for your fuel, but you also need your gasfier spezification (Water, Air, mixure etc.)... also interesting from your fuel ist particle size zone by zone for your packaging.

i hope it helps for a start.

beste reagards

torsten

Dear Hafiz Hamza Faheem

2 questions.

1. which software ?

2. do you only checked the numbers or also every single unit ? some times there ist the problem.?

Can you made some photos of your calculation and data ?

best regards

The mole fraction X1, X2.... was your gas compositions.

Following

Eulerian framework is used for fluid motion computation viz Lagrarian method. During coal carbonization volatile coal gas is formed in closed ovens. The objective of the research should be crystallized to arrive at.specific solution or results.

Some inorganic compound in biomass will be vaporized into aerosol form including KCl, K2SO4 and NaCl as most dominant fine particle compounds. When leaving cross section reaction area those temperature will gradually decrease and stick on wall column leading slagging formation. So, increasing high of column might be a consideration to make faster condensation of these aerosols. Thanks

Yes I have gone through it online

Very interesting question.

Thank you very much for your answer. The continuum between 320 and 440nm could well be due to a superposition of the CO2* and formaldehyde chemiluminescence, but I haven't yet been able to find a molecule that is referenced to emit the highest peak in this figure (the one at 422.5nm). I've looked through the entire work by Huber and Herzberg "Molecular Spectra and Molecular Structure - Constants of Diatomic molecules". and the only transition that comes close is the BO A-->X transition depicted in the screenshot below.

Considering that we're gasifying biomass and that this peak is present with a high intensity in all our measurements, I highly doubt, that this BO transition is the one is the one we're looking for.

Do you have any ideas, or any hints on where I should be looking?

I haven't found anything in the NIST or the RIOS databases that corresponds and frankly I'm not sure on how to proceed to solve this puzzle.

Please Ref to

Biomass Gasification and Pyrolysis- Practical design and Theory by Prabir Basu - Elsevier ISBN 978-0-12-374988-8

No . To read my article on biomass modeling : Modeling of a Microwave Plasma Driven Biomass Pyrolitic Conversion for Energy Production // Plasma Processes and Polymers DOI: 10.1002/ppap.201600161

Most probably degenerate parametric amplification circuits are what you are looking for.

Unfortunally for you, USA and Soviet applications are secreted, and control of energy produced by these as well.

The devolatilization process (referring to the release of gaseous fuel components as the solid fuel is heated) is a key characteristic of the combustion of solid fuels. The volatile gases burn much more rapidly than the remaining char particles and therefore are important for flame ignition and stability and play an important role in the formation of oxides of nitrogen (NOx), a regulated class of pollutants. Moreover, the devolatilization process determines how much char remains to be burned as well as the physical characteristics of the resulting char, with subsequent impacts on the char combustion properties.

Greetings

DWSIM usually works with fluids as such elemental carbon is an interesting request keep this in mind as you continue using the software.

Regardless DWSIM has a compound creator where you can add custom compounds. You will need to know the parameters of the custom compound for the equation of state you are using and the interaction model you are using.

See:

I hope this helps

Kind Regards

See the following link ;

Regards

L.Shafea

Dear Hafiz Shakeeb Arslan ,

RYIELD is utilized when the product mass distribution for a certain reaction is known. Product yields might be just directly introduced under the "basis yield column", as you show in your attached picture, or most likely calculated by means of a calculator block, as mentioned in previous answers.

As I assume your purpose in this case might be decomposing the biomass into its constituent components, you should import to the calculator the ULTANAL and PROXANAL data and include proper calculations to determine the mass yields, which you would export then to the RYIELD unit.

Hope this helps.

Best regards

Hi Hidam,

You cannot do things altogether at once. Start small then expand. You may join this community (https://www.solarcities.eu/blog) to look at their model of networking and working together through an open source. This community is consist of scientist and layman, they call themselves as practitioners. I have joined to learn then apply what I learnt so that at least I contribute to save the environment though in small scale but very meaningful.

From a more generalized viewpoint, the promising kinds of feedstock for renewable fuels should:

I believe you have an error in your simulation since the temperature profile that you are getting does not seem to be right. Did you check that your temperature and speciation profiles make sense first?

Once you ensure that your simulation is reasonable, and if the problem persists, I would check the species that you have marked in the "Species List". You should select the ones that you want to be displayed and that lead to the consumption/formation of H2O2 (which is the specie that you marked as your "end" of the reaction pathway).

You should work on reducing the 'Tar Concentration' from the gas line.

Hi:

Many universities have published online aspen manuals.

There are plenty of examples on how a bubbling fluidized bed gasifiers are designed. Two of them are attached here.

Anaerobic digestion

A challenge and an opportunity is to take advantage of the synergies between anaerobic digestion, gasification and Power-to-gas. Heat integration seems to be a first step especially if you need to heat the digester, dry the digestate and/or regenerate the scrubber liquid in case of amine based biogas upgrading. Separated CO2 from AD/upgrading and gasification/methanation as input for Power-to-gas. Use the microbial consortia in the digester to convert nitrogen free syngas from gasification to methane. Lower the specific investment cost in upgrading and downstream processes by combining AD, gasification and Power-to-gas.

Hi Hasan,

I strongly believe that indeed anaerobic digestion should be combined with gasification in some circumstances to achieve a sustainable living. In fact, to most cases, this is the pathway I highly recommend, especially where there are some non-degradable organic fraction in the feedstock. For example, when we use lignocellulosic biomass (e.g. livestock manures, crop residues, kitchen wastes) there are always some non-degradable organic fractions in the effluent (usually those wastes which contains complex aromatic rings structure such as lignin). These wastes should then be put into gasification plants to process further. Therefore, whenever solid or slurry organic matter containing high non-degradable organic fractions exist, please do a combination process.

The question would then be "when is this solution become economically feasible?". Frankly speaking, whenever we talk about economic feasibility, we are talking about competition with fossil fuels (oil, natural gas, coal), nuclear, and other REs (solar, wind, hydro). The proposed combination would only be feasible when competitor prices are high. Next, we also must include policy in this context. When the government shift their focus into RE development and biomass to bioenergy projects, then provides subsidy or special retail price for consumers, it would also become feasible. Lastly, when people realized that sustainability is an important factor and willing to pay more for a sustainable living, this scheme would allow a sustainable and economically viable.

I guess the main issue of your simulation is that the equation of state in use does not have thermophysical properties of atoms such as H, O, etc. It is advised that you re-calculate the decomposition and set the coefficients in a way that hydrogen and oxygen molecules will be generated. Perhaps this issue will be solved but I recommend to start from the converged coal gasification example of Aspen Plus and develop it with your own adjustment.

Dear Nicolas Esseiva:

I would recommend you to read the report "The Future of Hydrogen" by the International Energy Agency, which I identified earlier in my previous comments to this post.

(https://webstore.iea.org/download/summary/2803?fileName=English-Future-Hydrogen-ES.pdf)

Best Regards.

Dear Reza,

These reactions can be directly incorporated by switching on the species transport equation. Once to select the volumetric reaction rate option, you can define these reactions in reaction mechanism dialog box.

Simulation of fluidised bed with the CFD tools is not an easy task.

It has to be unsteady simulation, based on URANS or better on LES method and it should include at least the main chemical reactions that take place in the reactor: heterogeneous and homogeneous reactions.

Currently there is only one comersial software that partially can do that. This is the BARRACUDA software from CPFD Software Company, U.S.

There are other, Uni-made softwares, but it is hard to judge how good are they...

Applying it to biomass fluid bed gasifier, you can obrain detailed information about the fluidisation behaviour, temperature and species distribution among the gasifier.

Good luck,