Variation of CO with oxygen-coal ratio

The reactions that occur are: C+O2->CO+Q, C+H2O->CO+H2-Q, CO+H2O->CO2+H2O+Q. 1. When the oxygen-to-coal ratio is very low, the proportion of CO produced by carbon combustion is high, while the proportion of CO2 generated as a side reaction is low； 2. When the oxygen-to-coal ratio is high, complete combustion occurs, and the CO content is definitely low ； 3. The oxygen-coal ratio is reduced and the temperature of the gasifier is low, which is not conducive to steam decomposition and leads to an increase in CO content ； 4. A lower oxygen-to-coal ratio and a lower temperature in the gasifier facilitate the equilibrium of the CO and steam shift reactions, resulting in a reduced CO content ； 5. An increased oxygen-to-coal ratio and higher temperature in the gasifier facilitate steam decomposition, resulting in a decrease in CO content ； 6. An increase in the oxygen-to-coal ratio and a lower temperature in the gasifier are not conducive to maintaining equilibrium in the CO and steam reforming reactions, resulting in an increased CO content ； 7. Since the CO2 content in syngas is usually very low, the effect of the shift reaction factors is minimal ； Except in special cases. 8. The actual result is the accumulation of the interactions among carbon combustion, steam decomposition, shift reaction kinetics, and thermodynamics. 9. While maintaining production in the gasifier, as the oxygen-to-coal ratio increases from low to high, the CO content generally decreases from high to low. The preliminary conclusion is that, with the gasifier load remaining constant, as the oxygen-to-coal ratio increases, the gasifier temperature rises gradually, the proportion of carbon combustion increases, and CO levels rise. When the oxygen-to-coal ratio is too high, complete combustion of carbon occurs, resulting in a decrease in CO content. It is basically consistent with Professor Xu Yue’s conclusion. But it cannot be said that Professor Wang Fuchen is wrong, as this involves factors such as the type of coal (gasification rate and conversion rate), control methods (furnace temperature control, steam usage, load control), design pressure, and residence time. It is not even ruled out that there is an overall parabolic trend, but local fluctuations do exist. It’s possible that there are multiple minimum and maximum values: lol

There are two scenarios when the oxygen-to-coal ratio increases: the first is that the amount of oxygen remains unchanged while the amount of coal is reduced； In such a situation, since the temperature remains essentially constant, more CO2 is required to maintain it. First, the level of CO decreases; then, as heat increases, in order to keep the temperature stable, the reaction of CO2 being reduced to CO increases, and the level of CO starts to rise ； Secondly, with the coal amount remaining constant and the oxygen level increased while the temperature is kept fixed, the amount of CO produced first increases and then gradually decreases to maintain thermal equilibrium. Therefore, in terms of this issue, temperature is key.

The change in the oxygen-to-coal ratio actually corresponds to a change in the reaction temperature of the gasifier. When the oxygen-to-coal ratio is increased, the temperature of the gasifier rises; first, steam decomposes. As a result, the CO content in the gas increases as the oxygen-to-coal ratio rises. However, when the temperature reaches a certain level, the reaction CO + H2O → CO2 + H2 + Q occurs more frequently, leading to a decrease in CO levels – this is easy to understand. So what the two professors said above is not contradictory.

An increase in the oxygen-to-coal ratio results in more coal undergoing combustion, leading to an increased amount of heat released. This raises the temperature of the gasifier, providing more heat for the endothermic gasification reaction, which is beneficial for such reactions. Therefore, the carbon conversion rate, cold gas efficiency, and gas production increase, while CO2 and specific oxygen consumption as well as specific coal consumption decrease. As the oxygen-to-coal ratio increases further, the carbon conversion rate increases only slightly. Meanwhile, the excess oxygen entering the gasifier leads to an increase in CO2, which reduces the efficiency of cold gas production and the gas yield, while increasing the specific oxygen consumption and specific coal consumption. Therefore, there should be an optimal value for the oxygen-to-coal ratio; it is generally considered that an atomic ratio of oxygen to carbon around 1.0 is suitable

Under normal conditions, our company keeps CO at around 6%

Is what was mentioned upstairs about the control of carbon dioxide?

Oh, is it really necessary to analyze it in this way? It will be clear if you take a look at Shell’s diagram showing the relationship between the oxygen-to-coal ratio and CO2 concentration. The C element needs to be balanced; ignoring the factor of carbon conversion rate, the trend of CO concentration should be opposite to that of CO2. If the C conversion rate is taken into account, the situation is slightly different, but the overall trend remains the same. Overall, the trend in the amount of CO generated as the oxygen-coal ratio changes is an increase at first, followed by a decrease, with a maximum value occurring in between. The gasification reaction of water-coal slurry is slightly different, as the shift reaction also has a significant impact on the gas composition; an increase in oxygen content leads to a higher proportion of carbon oxidation to CO2. However, an increase in temperature reduces the extent of the shift reaction. A detailed analysis is needed to determine the exact circumstances, but it seems that the overall trend remains the same.

The reactions that occur inside the furnace are quite complex; at least 6 reactions need to be taken into account simultaneously: C+O2->CO+Q, C+O2->CO2, C+H2O->CO+H2-Q, CO+H2O->CO2+H2+Q, H2+O2->H2O, and CO+O2->CO2. The variation range of the oxygen-to-coal ratio should not exceed ±10% – it is meaningless to consider larger ranges. We assume that the furnace operates under standard conditions; in such cases, reducing the oxygen-to-coal ratio results in a decrease in all reactions. Compared to complete combustion, partial oxidation occurs to a greater extent, with reaction 1 occurring more frequently than reaction 2, leading to an increase in CO levels. However, reaction 3 decreases, and CO decreases. It is also impossible to determine in which direction the uncatalyzed conversion reaction proceeds under such high temperature conditions ； Since it is also difficult to determine the weight of each reaction in the overall reaction, the flow field conditions inside the furnace have a significant impact on the outcome of the reactions. Therefore, the gasifier is still considered a black box to this day, so we are not yet able to draw any conclusions at a theoretical level.

I read in a book that, in theory, for a given type of coal, there should be an optimal oxygen-to-coal ratio. However, for CO, as the oxygen-to-coal ratio increases, its proportion in the total mixture rises, while the proportion of hydrogen decreases. It can be said that the calorific value increases; that’s what the book says, and that’s what \"Xu Shisen\" stated as well. This is for dry processing only – for reference only.:)

Therefore, the original poster should also pay attention to the premises on which conclusions are drawn, and not simply take things out of context:loveliness: :loveliness: :loveliness:

The effect of changes in the oxygen-to-coal ratio on the CO content depends on the specific operating conditions, such as temperature, pressure, and so on

This is looking at the issue from various different perspectives, leading to completely different conclusions!

As the oxygen-to-carbon ratio increases, the combustion reaction intensifies, the system temperature rises, and the gasification process accelerates. As the CO2 concentration increases, the CO concentration remains roughly constant (the carbon conversion rate increases), the H2 concentration decreases, and the CH4 concentration also decreases; therefore, there must be an optimal oxygen-to-carbon ratio. Moreover, the subsequent processing steps also need to be taken into consideration: whether a higher calorific value is required or if something else needs to be synthesized; the key is to consider the conversion of CH4 within it.

My simulated calculation results differ from those of the two professors; my conclusion is that as the temperature of the gas exiting the combustion chamber rises, so does the CO level. (I considered only the effect of temperature on the gas composition, without taking into account whether the change in furnace temperature is caused by a change in the oxygen-to-coal ratio or the steam-to-coal ratio.) This is because the gas composition exiting the combustion chamber is essentially determined entirely by the shift reaction. I tested the relationship between gas composition and temperature as described in the patents related to dry coal powder, and it matched perfectly. Friends who are interested in discussing this with me can leave a message

Isn’t adjusting the furnace temperature done by adjusting the ratio of oxygen to coal slurry? ? In other words, given a fixed amount of oxygen and coal slurry, the furnace temperature is determined. How can we still say that one of the two changes, and then analyze the changes in CO and CO2 when the furnace temperature remains constant? It’s just my personal opinion; I hope the experienced master can give some guidance! Personally, I think it should be analyzed based on changes in the oxygen-coal ratio (whether there are changes in the amount of oxygen or in the amount of coal slurry). At this point, some people say that when the oxygen-coal ratio increases, the CO content rises first; the reason for this is decomposition of water vapor. But as the oxygen-to-coal ratio increases, CO + 02 — that is, CO2 — which one becomes dominant when the oxygen-to-coal ratio rises? ? Exactly how does the CO content change as the oxygen-to-coal ratio increases? ? I’d appreciate some advice from experts! ! Hehe:handshake

We are Texaco’s furnaces; our CO level is generally kept between 36 and 40, while the CO2 level is usually maintained between 18 and 21! Normally, when the furnace temperature is high, CO2 levels rise while CO levels drop! Our company has also experienced the exact opposite situation! At this point, don’t rush to lower the temperature; make adjustments gradually, extend the time taken for these adjustments, and even adjust the furnace temperature in the opposite direction. Surprising results can occur at this stage!

Can the reaction CO+H2O->CO2+H2O+Q take place? That one came to balance things out