Experts, do you think the results of gasification in Indonesia are reasonable?

The key to the simulation process is whether it is close to reality, while also adhering to mass balance and energy conservation. The high levels of H2O and CO2 are mainly due to an excessive amount of oxygen being supplied; under such conditions, the vaporization temperature cannot be 1470 degrees. Also, I’m not sure whether to choose N2 as the carrier gas.

What was said upstairs makes sense; it seems like the person is an expert. Given that the softening temperature of Indonesian coal is around 1400 degrees, the gasification temperature was set at 1470 degrees in this simulation; I’m not sure if this is reasonable There’s also the oxygen level; the ratio of oxygen to carbon is 0.8, which I guess isn’t very high either. After drying, it is desired to reduce the moisture content in coal to 1%, but even if it is reduced to 0%, why is there still so much moisture generated? I’m not sure if you understand what I mean I would like to ask this expert: could you explain other possible causes?

Based on your coal quality analysis, it seems to belong to the lignite category as well, with a relatively high oxygen content. I’m not sure whether the internal moisture has been converted into H and O and included in the analysis data The gasification temperature should be determined based on the flow temperature of the ash, with an additional 100~150 degrees added to that temperature. Powder coal gasification requires the transfer of heat outside; I’m not sure how this aspect was taken into consideration Lignite is difficult to dry; usually, it only needs to be dried to a moisture content of 6–8%. A certain amount of steam is usually added in pulverized coal gasification; how did the original poster consider this aspect? The methane content is significantly too low, usually at the level of a few parts per ten thousand ； There should be no oxygen left ； I’m not sure about the balance of sulfur; it seems that the total amount of sulfur in the gas is a bit low. I’m not sure how you carry out the simulation – do you use process simulation software or something else?

The oxygen-carbon ratio is not high, but the coal itself has a high oxygen content. The formation of moisture is not determined by the level of moisture present in the coal; rather, it is caused by an excess of oxygen supplied. With an excess of oxygen, two reactions occur: 2H2 + O2 = 2H2O and 2CO + O2 = 2CO2. I wonder what software you used for simulation?

In response to the two experts above, first is Bone, my good friend (unrequited love). 1) Based on your coal quality analysis, it seems to belong to the lignite category as well; the oxygen content is relatively high. I wonder if the internal water has been converted into H and O and included in the analysis data? I haven’t considered this yet; I just input the results of elemental analysis into the simulation software. The results of industrial analysis are as follows: Mo 20, FC 48.22, VM 50.1, ASH 1.68. As for the internal moisture content, I’m not sure 2) The gasification temperature should be determined based on the flow temperature of the ash, with an additional 100~150 degrees added to that temperature. FT+100-150, is there any basis for this? It’s best to list some references. 3) Powder coal gasification requires the transfer of heat outside; I’m not sure how this aspect was taken into consideration This was taken into account during simulation; is heat dissipation loss sufficient? 4) Lignite is difficult to dry; it usually only needs to be dried to a moisture content of 6~8%. Is this the usual case? Are there any exceptions, or can a 5% dryness level be achieved? 5) A certain amount of steam is usually added in powder coal gasification; how did the original poster address this issue? A lot of moisture has already been added; what’s the need for steam? This simulation model does not take water vapor into account. 6) The methane content is significantly too low, usually at the level of a few parts per ten thousand ； There should be no oxygen left ； I’m not sure about the balance of sulfur; it seems that the total amount of sulfur in the gas is a bit low. The value of CH4 is indeed a bit low, but the calculations converge. As for O2, it takes into account some inert gases; I’m not sure about S, as it has never caught my attention. 7) I’m not sure how you carry out the simulations – do you use process simulation software or something else? The basic process of the model is as follows: coal is ground into powder, then dried to remove water (5%), followed by decomposition to produce slag. Subsequent combustion and gasification result in the formation of synthetic gas. The simulation software used is Aspen+. The oxygen-to-carbon ratio of the volatiles in this case is not high; however, the coal itself contains a high amount of oxygen. The presence of water is not determined by the level of moisture in the coal, but rather by the excessive amount of oxygen supplied. With an excess of oxygen, two reactions occur: 2H2 + O2 = 2H2O and 2CO + O2 = 2CO2. I wonder what software you used for simulation? I’m not sure what your final conclusion is – whether my simulation results are correct or make any sense at all The software I use is Aspen Process Simulation

I simply converted the calculation results to a dry basis; no extensive calculations were done, so the conclusion should be correct. Furthermore, from your reply to bone’s post, it can be seen that the simulation is rather simplified; it is inaccurate not to take into account the addition of steam, element balance, and ash melting point T3 in the powder coal gasification process. FT+100 degrees is a result derived from practice, and it is accepted by the industry as a whole. This post was last edited by koolar on 2007-11-29 13:05]

The issue with water is as follows: lignite usually has a high content of internal water, which is difficult to remove. Looking at the analysis results, I wonder whether they are based on an air-dried basis, with the ash removed first. If that’s the case, then the internal water is completely distributed among H and O. In reality, some of this internal water is removed during the drying process of lignite; thus, the actual coal fed into the furnace contains less H and O. This is just a guess, and there’s no need to delve deeper into it. The degree of drying is determined based on the principles applied in the Shell project at Datang. The lower the level of internal moisture that needs to be controlled, the higher the drying temperature required, which in turn increases the difficulty and energy consumption. Shell’s gasification temperature is usually between 1500 and 1700 degrees. The softening temperature you mentioned is 1400 degrees, which means the flow temperature is even higher. In such cases, it’s necessary to add a certain proportion of limestone in order to reduce the flow temperature to around 1400 degrees (this is Shell’s standard practice). Then, a temperature about 150 degrees higher than that is chosen as the gasification temperature. This is done mainly to ensure a sufficient safety margin in terms of temperature, so that the slag retains its fluidity. Texaco uses a similar approach. I think there’s no need to cite sources anymore. The heat transferred outward is achieved through the by-product steam; generally, the amount of heat transferred is considered to be around 2% of the heat contained in the coal. I’m not sure whether this has been fully taken into account. In powder coal gasification, steam is usually added to adjust the heat balance of the entire gasification system; this also helps to reduce oxygen consumption and increase the H2 content in the syngas. Shell’s typical oxygen-to-carbon ratio ranges from 0 to 0.3 (on a weight basis), and it can be adjusted depending on the calorific value of the coal and its own water content; it seems that the original poster didn’t give much thought to this. There should be no problems with your simulation process; since Aspen+ is being used, the materials and energy balances must be correct. The client needs to adjust the equilibrium temperature range for the methane formation reaction. As for sulfur, I think I’m overthinking it. I suggest you calculate the heat loss to see if it is appropriate, and also check whether the calorific value of the coal is accurate. Another point: why is the ash content so low? If that’s indeed the case, some ash must be added to ensure the water wall can function properly. I’m willing to make more friends like you.

I have a question for the experts upstairs regarding the issue of introducing steam into the gasification furnace. When steam is introduced, oxygen can be saved – how does that work? The introduction of water vapor triggers a hydrolysis reaction: CO + H2O = CO2 + H2. This inadvertently reduces the concentration of CO while increasing the concentration of CO2. Does this mean that the quality of the syngas is compromised? I’m not quite sure; I hope for a detailed explanation

Before I knew it, so many replies appeared above. I just took another close look at your two sets of analysis data: A 1.68, C 63.04, H 5.11, N 0.24, S 0.52, O 29.41, Mo 20, FC 48.22, VM 50.1, ASH 1.68. I think my speculation regarding the composition is correct; the ash content in the industrial analysis matches that in the total analysis, which indicates that the water present in the industrial analysis has been accounted for in the H and O values in the total analysis. CO2 is used as a carrier gas; it is employed in the powder coal gasification units for methanol production. N2 is more suitable as a carrier gas for ammonia synthesis plants. I’d also like to remind that guy: the amount of limestone to be added depends on the composition of various components in the ash, and only through calculations can an accurate ratio be determined. It seems a bit unfounded to draw conclusions without knowing those compositions. :)

Converting internal water into H and O is not very reasonable. Additionally, I am not in favor of using nitrogen for transportation; there is no need to incur unnecessary compression work. Nitrogen should be supplied before ammonia synthesis. As for adding limestone, the ash composition has not been observed; it’s indeed too early to draw any conclusions. Thank you, Bone, for the reminder; I’ll learn from you*.

First of all, thank you to the engineer upstairs for taking such good care of me, this ‘foolish kid’. What you said makes sense – the values are indeed distributed within the HO (I don’t know how exactly they’re distributed). It’s just that the simulation software requires it this way; I’m not sure either, but I just need to remember a few principles for inputting the data. The data I have available is as follows: for element analysis, it’s A 1.68, C 63.04, H 5.11, N 0.24, S 0.52, O 29.41. What’s annoying is the result of the industrial analysis; the original data is as follows: Mo without FC is 48.23, VM is 50.1, and ASH is 1.67. In other words, the two values for ash content differ slightly. To make them consistent, I made some adjustments to the industrial analysis results and added in the moisture content (it’s said on the internet that Indonesian coal has a moisture content of 15-25%). So the values become Mo 20, FC 48.22, VM 50.1, ASH 1.68. As for those parts that weren’t handled properly, I’m not sure about them. It is stated that the simulation software requires that the ash content in industrial analysis and elemental analysis be identical. Out of necessity, this second volume is produced

Dude, take a look at my arguments in this post; it might give you some insights to help you understand better. http://bbs.hcbbs.com/thread-93841-2-2.html

I believed you and fed steam at a ratio of 0.3, at 200 degrees and 28 bar, into the vaporization furnace. Take a look at how the composition of the gas has changed this time: CO 0.44525956, O2 0.09343118, H2 0.19037916, CH4 2.2086e-09, O2 0.00064215, N2 0.02912326, Ar 2.8224e-06, H2S 0.00141131, COS 0.00025387, NH3 5.8252e-06, H2O 0.23949084

The gray values in these two analyses are very close, indicating that they correspond to the same set of data. Element analysis should generally be conducted on coal that is free of moisture and ash; however, based on the data you provided, the element analysis was carried out using the basis of industrial analysis (usually on a received-base basis), which can easily lead to discrepancies. When I run simulations on Aspen, I usually enter dry coal (anhydrous) as a separate component, and water as another component; I find this to be more realistic, as during gasification the water isn’t first broken down into H2 and O2 before any reactions take place. Of course, when coal is imported separately, it’s necessary to adjust its calorific value accordingly.

Did you set the gasification reaction temperature at 1470 degrees yourself? What is the reactor heat level shown at this time? It is assumed here that there was a problem to begin with. Furthermore, breaking down H2O into H and O is not accurate; if entered in this way, ASPEN will calculate the heat released from the reaction between H and O, when in fact that is not the case. The material in your simulation results may be balanced, meaning that the components of the gas may have balanced levels of each element. However, since you assumed a reaction temperature of 1470 degrees, the heat released at this temperature cannot be removed by the water-cooled walls; therefore, this assumption is incorrect. As for drying lignite to 8%, there are two considerations. It ensures stable transportation while also minimizing energy consumption for coal grinding and drying. As for whether steam needs to be added, adding steam can help lower the reaction temperature, so this should be considered. Also, through what medium is the coal powder transported, and what is the transportation ratio?

BONE said that when I conduct simulations in Aspen, I usually enter dry coal (anhydrous form) separately and water as another component, as it seems more realistic that way. This method is better; I’ve done it the same way as well.

Why are you in such a hurry? It’s not too late to analyze the problem first. Do you have the calorific value data available? Have you calculated the higher calorific value based on elemental analysis? Do the two match? If the calorific value data is correct, it is recommended that you check your model. Check whether the consideration of heat loss is reasonable. Using no steam or less steam might be more suitable for your current situation. I also suggest that you recalculate using the simulation suggestions I gave you in my previous post.

You only considered material balance and didn’t consider whether a reaction is possible.

It’s a bit chaotic; I’ll answer slowly. (1) Exit temperature: 1470 degrees. (2) Exit pressure: 28 bar. (3) Heat duty: 137010303 watts. (4) Net heat duty: 125909672 watts. (5) It’s all gas. Someone else asked me about the medium used for feeding coal powder – it’s N2 with a concentration of 0.077 coal

The outlet temperature of 1470 degrees was set by you, right? How was the heat capacity of 137MW determined? Do you know what the heat duty is in the gasification reaction zone of a 2000 t/d furnace?