Method for estimating the heat of chemical reaction of hydrocarbon compounds and method for operating a blast furnace

Abstract

This invention provides a method for estimating the heat of chemical reactions of hydrocarbon compounds, such as coal, which can rationally estimate the heat of reaction, and a method for operating a blast furnace that can stabilize blast furnace operations. [Solution] A method for estimating the heat of chemical reaction of a hydrocarbon compound and its application, comprising: expressing the molecular formula of a hydrocarbon compound selected from the group consisting of coal, coke, and biomass coal in terms of per mole of carbon; stoichiometrically estimating the standard enthalpy of formation per mole of carbon using the value of the heat of complete combustion of the hydrocarbon compound; and estimating the amount of heat absorbed or released during the chemical reaction of the hydrocarbon compound based on the estimated value of the standard enthalpy of formation per mole of carbon.

Description

[Technical Field]

[0001] This disclosure relates to a method for estimating the heat of chemical reaction of hydrocarbon compounds and a method for operating a blast furnace. [Background technology]

[0002] In blast furnace operation, reducing agents such as pulverized coal are blown in through tuyeres, causing incomplete combustion in a carbon-rich environment, thereby supplying heat to the blast furnace. Coal is composed of various elements in addition to carbon and hydrogen, and the degree of carbonization (carbon content) varies depending on the source. Therefore, when the type of pulverized coal changes, the amount of heat from incomplete combustion changes, and the amount of heat supplied to the blast furnace also changes. In order to achieve stable operation of the blast furnace under conditions where the amount of carbon injected in pulverized coal is kept constant and only the type of coal is changed or substituted, it is important to minimize the change in the heat of incomplete combustion at the tuyeres.

[0003] For example, Patent Document 1 proposes a method for estimating the combustion rate of a blast furnace-injected reducing agent by measuring the emission peak intensity of radicals in the combustion field of a reducing agent such as pulverized coal through an observation hole provided in a tuyer or the like. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2018-204076 [Overview of the project] [Problems that the invention aims to solve]

[0005] This disclosure aims to provide a method for estimating the heat of chemical reactions of hydrocarbon compounds, such as coal, which can rationally estimate the heat of reaction, and a method for operating a blast furnace that can stabilize blast furnace operations. [Means for solving the problem]

[0006] The above problems will be solved by the following means. <1> To express the molecular formula of a hydrocarbon compound selected from the group consisting of coal, coke, and biomass coal, per mole of carbon. The standard enthalpy of formation per mole of carbon is estimated stoichiometrically using the value of the heat of complete combustion of the hydrocarbon compound, and Based on the estimated standard enthalpy of formation per mole of carbon, estimate the endothermic amount of the chemical reaction of the hydrocarbon compound. A method for estimating the heat of chemical reaction of hydrocarbon compounds containing hydrocarbons. <2> The value of the heat of complete combustion mentioned above is the measured value from the complete combustion test. <1> A method for estimating the heat of chemical reaction of hydrocarbon compounds described above. <3> The value of the heat of complete combustion mentioned above is an estimated value obtained using Dulong's formula. <1> A method for estimating the heat of chemical reaction of hydrocarbon compounds described above. <4> The aforementioned chemical reaction is an incomplete combustion reaction. <1> ~ <3> A method for estimating the heat of chemical reaction of hydrocarbon compounds described in any one of the following. <5> <4> To estimate the heat of chemical reaction of multiple types of pulverized coal using the method for estimating the heat of chemical reaction of hydrocarbon compounds described above, and Select the pulverized coal to be introduced into the tuyeres of the blast furnace, taking into consideration the estimated heat of each chemical reaction of the aforementioned multiple types of pulverized coal. A method of operating a blast furnace, including [specific details omitted]. <6> When changing the type of pulverized coal introduced into the tuyeres of the blast furnace, the thermal compensation conditions are further adjusted based on the difference between the estimated heat of chemical reaction of the pulverized coal before the change and the estimated heat of chemical reaction of the pulverized coal after the change. <5> The operating method of the blast furnace as described in [the relevant document]. [Effects of the Invention]

[0007] This disclosure provides a method for estimating the heat of chemical reactions of hydrocarbon compounds, such as coal, which can rationally estimate the heat of reaction, and a method for operating a blast furnace that can stabilize blast furnace operations. [Brief explanation of the drawing]

[0008] [Figure 1] It is a diagram showing an example of a method for calculating the standard formation enthalpy per mole of carbon in benzene. [Figure 2] It is a diagram showing an example of a method for calculating the standard formation enthalpy per mole of carbon in coal. [Figure 3] It is a diagram showing the reaction equations and enthalpy balances of incomplete combustion of coals A to C. [Figure 4] It is a diagram for explaining an example of estimating the reaction heat of the carbonization reaction (thermal decomposition under anaerobic conditions) of coal.

Embodiments for Carrying Out the Invention

[0009] A method for estimating the chemical reaction heat of a hydrocarbon compound according to the present disclosure (hereinafter, may be abbreviated as "the estimation method of the present disclosure") and an operation method of a blast furnace will be described.

[0010] When determining the heat absorption or release amount of a certain reaction, it is common to evaluate the increase or decrease in the standard formation enthalpy of the substances before and after the reaction. However, for coal, the concept of standard formation enthalpy does not exist, so even if a physical property value table is consulted, the value cannot be found. Also, usually, what is found from the literature about the heat absorption or release amount of a reaction is only the complete combustion heat (the measured value in a complete combustion test). On the other hand, for example, when introducing pulverized coal from the tuyere of a blast furnace to evaluate the incomplete combustion temperature, it is advantageous to use the standard formation enthalpy because it enables stoichiometric evaluation before and after the reaction.

[0011] Therefore, the inventors of the present disclosure studied a method for effectively utilizing physical property value information such as the complete combustion heat of coal, and as a result of attempting to devise a method for estimating a physical property value corresponding to the standard formation enthalpy for coal as well, a method for estimating the chemical reaction heat of a hydrocarbon compound according to the present disclosure was found. That is, the estimation method of the present disclosure is expressing the molecular formula of a hydrocarbon compound selected from the group consisting of coal, coke, and biomass charcoal per mole of carbon, To estimate the standard enthalpy of formation per mole of carbon stoichiometrically using the value of the heat of complete combustion of hydrocarbon compounds, and This includes estimating the endothermic and exothermic rates of chemical reactions of hydrocarbon compounds based on estimates of the standard enthalpy of formation per mole of carbon.

[0012] This method allows us to estimate the standard enthalpies of formation of each substance before and after a chemical reaction involving coal, thereby enabling us to appropriately evaluate the heat of reaction. As a result, even if, for example, the ratio of different types of pulverized coal injected into the blast furnace tuyeres has to be changed, creating a risk of changes in the combustion conditions of the pulverized coal, it is possible to stabilize blast furnace operation by setting conditions that suppress changes in the heat of combustion reaction.

[0013] The “hydrocarbon compounds” to which the estimation method described herein applies are solid carbonaceous materials of plant origin, composed of carbon, hydrogen, and other elements, and include coal, coke, and biomass coal. The following explanation will primarily focus on coal as a representative example.

[0014] Since coal is primarily composed of carbon, ultimately, if it can be converted to the "standard enthalpy of formation per mole of carbon," it will be possible to apply this to the evaluation of various reactions of different types of coal. For example, while it is not necessary to convert to the "standard enthalpy of formation per mole of carbon" for monomolecules, we will use benzene as an example to explain how to convert to the "standard enthalpy of formation per mole of carbon" from the heat of combustion of hydrocarbon compounds. Figure 1 shows an example of how to calculate the standard enthalpy of formation per mole of carbon, using benzene as an example. The molecular formula of benzene is originally C6H6, but when expressed per mole of carbon, it becomes CH, as shown in the "complete combustion stoichiometric formula" in Figure 1. Based on this stoichiometric formula, the standard enthalpy of formation of oxygen is "0", so the balance equation for the complete combustion reaction can be expressed by equation (1) in Figure 1. Then, by rearranging equation (1), we can obtain the "standard enthalpy of formation per mole of carbon" for benzene.

[0015]

number

[0016] This can be expressed by equation (2) in Figure 1. That is, the enthalpy of formation of benzene is [1] Higher heating of benzene per mole of carbon

[0017]

number

[0018] If it is known, [2] Standard enthalpy of carbon dioxide production

[0019]

number

[0020] [3] Standard enthalpy of water

[0021]

number

[0022] It can be uniquely determined using [this method].

[0023] Similarly, for coal, if we know the heat of complete combustion [1], then the values ​​of [2] and [3] are also known, and it becomes possible to determine the "standard enthalpy of formation per mole of carbon".

[0024] In the example of benzene (equation (2) in Figure 1), the coefficient of the enthalpy of water formation is "1 / 2," but in the case of coal, this coefficient changes depending on the type of coal. For example, the molecular formula per mole of carbon for a certain type of coal is CH m O l When expressed as such, the coefficient of the enthalpy of water formation is "m / 2".

[0025] The standard enthalpy of formation is defined as the energy required to decompose a substance into its basic constituent elements (C, H2, O2, N2, S, and Ash) under standard conditions (where the standard enthalpy of formation is zero). Therefore, the standard enthalpy of formation calculated by equation (2) can be considered as the "pure decomposition heat per mole of carbon (kJ / mol)" of coal. For reference, using this method, the "standard enthalpy of formation per mole of carbon" calculated from the combustion heat per mole of carbon of benzene (544.5 kJ / mol) is 8.03 kJ / mol. Therefore, converting this to units of the molecular formula C6H6 and multiplying by 6 gives 48.18 kJ / mol. This value is in close agreement with the literature value of 49.0 kJ / mol for the standard enthalpy of formation of benzene.

[0026] Next, we will illustrate the estimation method described in this disclosure by examining coals A, B, and C. Generally, coal is analyzed according to the analytical methods specified in JIS standards, and the results are compiled into industrial analysis values, elemental analysis values, and ash (ash content) component analysis values. Tables 1 and 2 show the component analysis results for coals A, B, and C.

[0027] [Table 1]

[0028] [Table 2]

[0029] Table 3 shows the ratio of each element per mole of carbon for coals A, B, and C, based on the analysis results in Tables 1 and 2.

[0030] [Table 3]

[0031] Taking coal A as an example, the molecular formula expressed per mole of carbon is:

[0032]

number

[0033] Therefore, the molecular weight of Ash is 76.17.

[0034]

number

[0035] Molecular weight (MW) coalA ) indicates that it is 14.19.

[0036] Also, the coal matrix portion excluding ash

[0037]

number

[0038] Molecular weight (MW) coalA,NoAsh ) also indicates that it will be 13.08.

[0039] Here, we will explain the assumptions made in deriving the results in Table 3 from the results in Tables 1 and 2. The analytical values ​​shown in Tables 1 and 2 often do not add up to 100 Wt%. In such cases, fine adjustments are made to bring the total to 100 Wt%. For example, the Ash + VM + FC (ash + volatile components + fixed carbon) in Table 1 was adjusted to 100 Wt%. Furthermore, the elemental components of the industrial analytical value VM + FC (volatile components + fixed carbon: the coal matrix portion excluding the ash of coal) were assumed to be C, H, N, O, and TS (total sulfur) in the elemental analytical value, and the total was adjusted to 100 Wt%. In addition, it is assumed that the oxygen oxide contained in the ash does not affect the oxygen in the coal matrix portion excluding the ash of coal, and that the TS (total sulfur) in Table 1 is treated as sulfur in the coal matrix portion.

[0040] Therefore, the equation for the complete combustion rate of coal A is given by the expression shown in Figure 2, and the heat balance equation for the complete combustion reaction can be expressed by equation (3). By rearranging equation (3) in the same way as shown in Figure 1, the "standard enthalpy of formation per mole of carbon" of coal A can be expressed by equation (4) in Figure 2. Here, Ash assumed that the constituent oxide components do not change during combustion. Note that the complete combustion formula in Figure 2 is considerably simplified. Specifically, it assumes that the combustion products are only CO2 and H2O, and that the other elemental components (N, S) are basic components with a standard enthalpy of formation of zero. This assumption is reasonable because the bonding amounts of N and S are small, and it also avoids the complexity that would arise if NO2 and SO2 were produced. Of course, it is also possible to formulate the reaction assuming that NO2 and SO2, which are formed by the complete oxidation of N and S, are the reaction products.

[0041] Looking at equation (4) in Figure 2, it is an equation that represents the "standard enthalpy of formation per mole of carbon" of coal, but the higher heating value per mole of carbon of coal

[0042]

number

[0043] These also need to be known conditions. The measurement method for the higher heating value of coal per unit mass (e.g., kg) is determined by JIS standards and is often indicated at the time of coal shipment. The far right of Table 1 shows examples of the higher heating value (HQ) measurements for coals A, B, and C. These values ​​are then corrected, for example, to the value of the coal substrate (excluding ash), and the molecular weight of the coal is calculated (excluding ash, as shown on the far right of Table 3: for coal X (MW)). coalX,NoAsh Taking the product of )) gives the higher heating value per mole of carbon in coal.

[0044]

number

[0045] It can be converted to

[0046] In addition, as an empirical formula for estimating the higher calorific value of coal, Dulong's formula (the following formula (5)) is known.

[0047]

Number

[0048] This formula is used to estimate the higher calorific value Q per unit kg of coal from the Wt% of C, H, O, and S in the matrix part of coal (Wt% C , Wt% H , Wt% O , Wt% S ). Since the formula (5) is for estimating the higher calorific value of the coal matrix part, when multiplying by the molecular weight of coal (excluding Ash at the right end of Table 3: in the case of coal X (MW high )), the higher calorific value per mole of carbon in coal coalX,NoAsh )) is obtained.

[0049]

Number

[0050] It can be converted to

[0051] Table 4 shows the calculation results of the standard formation enthalpy per mole of carbon calculated by these two methods.

[0052]

Table 4

[0053] When calculating the standard formation enthalpy per mole of carbon in coal, which conversion value to adopt can be determined by looking at the actual results. However, it is considered that Dulong's formula tends to be able to推算 more stable conversion values.

[0054] Using the "standard enthalpy of formation per mole of carbon in coal" calculated by the methods described above, we will now show an example of a method for evaluating the endothermic and heat-generating amounts of a reaction. First, the endothermic and heat-generating amounts in the reaction equation can be expressed in general notation as shown in equation (6).

[0055]

number

[0056] Here, the first term on the right-hand side is the sum of the enthalpies of formation of the products on the right-hand side of the stoichiometric equation, and the second term on the right-hand side is the sum of the enthalpies of formation of the reactants on the left-hand side of the stoichiometric equation. i and α i These are coefficients applied to substance i on the product side and reactant side, respectively, when expressed in stoichiometric formulas. (Third term on the right-hand side)

[0057]

number

[0058] This term considers the phase change heat effect when a product, which is solid or liquid under standard conditions, sublimes or evaporates. It is considered positive when a phase change occurs. The third term on the right-hand side is enclosed in double parentheses to indicate that it may or may not be considered. Heat of reaction

[0059]

number

[0060] If the value is positive, it indicates an endothermic reaction; if it is negative, it indicates an exothermic reaction. Furthermore, its absolute value represents the amount of heat [kJ / mol].

[0061] Figure 3 shows the results of evaluating the calorific value of coals A, B, and C, focusing on incomplete combustion reactions.

[0062] Since H2, N2, S, and Ash can be treated as having zero standard enthalpy of formation, the difference between the standard enthalpy of formation of CO and coal becomes the heat absorbed. The result of equation (6) is negative, so it can be seen that the heat of incomplete combustion of any coal is an exothermic reaction. The degree of heat is coal A > coal B > coal C, so it can be seen that the higher the enthalpy of formation, the higher the potential for heat release in incomplete combustion. However, it should be noted that this result is obtained by assuming that Dulong's equation ((5)) is correct. Here, since phase change is not involved in incomplete combustion, in equation (5)

[0063]

number

[0064] It is set to zero.

[0065] This disclosure provides a method for estimating the standard enthalpy of formation per mole of carbon in hydrocarbon compounds such as coal, enabling a more rational estimation of the heat of reaction in chemical reactions involving coal and other materials. As a result, it becomes possible to appropriately control conditions such as the combustion conditions of pulverized coal in a blast furnace tuyer. For example, by estimating the heat of chemical reaction of several types of pulverized coal using the estimation method of this disclosure, and selecting the pulverized coal to be introduced into the blast furnace tuyer considering the estimated heat of chemical reaction of each type of pulverized coal, it is possible to contribute to the stabilization of blast furnace operation. Furthermore, when changing the type of pulverized coal (coal brand) introduced into the tuyeres of a blast furnace (including changing the ratio when multiple types of pulverized coal are used in combination), it is possible to achieve more stable blast furnace operation by adjusting the heat compensation conditions (airflow moisture content, airflow temperature, etc.) based on the difference between the estimated heat of chemical reaction of the pulverized coal before the change and the estimated heat of chemical reaction of the pulverized coal after the change. [Examples]

[0066] The following describes examples of the method for estimating the heat of chemical reaction of hydrocarbon compounds according to this disclosure. However, the method for estimating the heat of chemical reaction of hydrocarbon compounds according to this disclosure is not limited in any way to the examples described below.

[0067] [Determining the amount of heat adjustment when changing the type of pulverized coal blown into the blast furnace tuyeres] In blast furnace operation, pulverized coal is injected through tuyeres, and heat is supplied to the furnace by causing incomplete combustion in a carbon-rich field. Therefore, as shown in Figure 3, if the type of coal changes, the amount of heat from incomplete combustion changes, and thus the amount of heat supplied to the blast furnace also changes. In order to achieve stable operation of the blast furnace under conditions where the amount of carbon injected in pulverized coal injection is kept constant and only the type of coal is changed or substituted, it is extremely important to keep the heat from incomplete combustion at the tuyeres as unchanged as possible. For this reason, we decided to try to control the heat using the method disclosed herein.

[0068] <Method> Blast furnace (inner volume 5000m 3 In this class, the airflow rate Vb = 5800 Nm 3 / min, oxygen enrichment flow rate O2 = 33000 Nm 3 / hr, air temperature Tb=1210℃, air humidity Mb=20g / Nm 3 Assuming a pulverized coal injection rate PC = 90 tons / hr, the coal mass ratio of this pulverized coal injection rate is the coal A ratio: r coalA =0.5, Coal B ratio: r coalB Operations continued at =0.5. Here, the coal B ratio r coalB =0.4, coal C ratio r coalC To make the ratio = 0.1, we decided to replace a portion of coal B with coal C. In other words, r from coal B to coal C PC,rplc The substitution is performed by a ratio of 0.1. In this case, from the results in Figure 3, the decrease in calorific value due to coal substitution is Q. PC,rplc [kW] can be expressed using the following formula:

[0069]

number

[0070] Substituting the corresponding numerical values ​​into equation (7), Q PC,rplc It is understood that the heat output will decrease by approximately -6800kW. Therefore, the policy was adopted to compensate for this decrease in heat by reducing the amount of moisture in the blown air. In other words, by lowering the amount of moisture in the blown air and reducing the amount of endothermic reaction by 2H2O⇒2H2+O2, the amount of heat of combustion at the tuyeres will be controlled so that it does not change. Assuming that the enthalpy of water formation is 13400 J / g, the amount of moisture to be reduced can be calculated to be approximately 508 g / s. If the blown air flow rate Vb and the oxygen enrichment flow rate O2 are kept constant, the amount of reduction in blown air moisture is 4.8 g / Nm 3 It can be estimated that it is of a certain degree.

[0071] <Result> In blast furnace operation, coal B is transferred to coal C. PC,rplc =0.1 Substitution is performed only by the ratio, and simultaneously, the amount of moisture in the airflow Mb = 20g / Nm 3 Therefore, Mb = 15g / Nm 3 Adjust the conditions (5g / Nm 3 A test was conducted to reduce the emissions. As a result, it was confirmed that there were no significant changes in the blast furnace operating parameters even after substituting or changing the coal type, and that stable operation could be continued.

[0072] Here, we have illustrated a case where the decrease in calorific value due to coal substitution is compensated for by reducing the moisture content of the blown air. However, similar thermal compensation can be achieved by increasing the blown air temperature (i.e., increasing the sensible heat of the blown air).

[0073] Furthermore, in blast furnace operation, it is common to model and evaluate the combustion phenomenon at the tuyere as the adiabatic flame temperature (so-called Tf: tuyere combustion temperature) (see, for example, Chapter 6, "Pigmaking Handbook" by Akitoshi Shigemi, Chijin Shokan, 1979). The results of this disclosure are also effectively applicable in this case. In this case, although it depends on the combustion modeling method, if Tf is formulated in the form of a stoichiometric equation for incomplete combustion, a more accurate adiabatic flame temperature evaluation becomes possible by replacing the standard enthalpy of formation of carbon (0 by definition) with the standard enthalpy of formation of coal determined by the method of this disclosure. In particular, when so-called low-calorie coal (relatively inexpensive coal) is evaluated by the method of this disclosure, a considerably low standard enthalpy of formation is estimated. By accurately estimating this reduction, temperature compensation and thermal compensation can be accurately performed with this disclosure, making it easier to find tuyere conditions that allow for stable operation even when a large amount of pulverized coal is replaced with low-calorie coal.

[0074] Although the descriptions of embodiments and examples in this disclosure primarily focus on incomplete combustion reactions, the estimation method described herein is applicable to any coal reaction in which the reactants and products are known.

[0075] Furthermore, although "coal" was used as an example of a hydrocarbon compound in the embodiments and examples of this disclosure, the estimation method of this disclosure can be applied without any problems to any hydrocarbon compound that can be defined by the industrial analysis values ​​and elemental analysis values ​​in Table 1 or the Ash analysis values ​​in Table 2, such as biomass coal and coke.

[0076] Furthermore, although the embodiments and examples of this disclosure describe the incomplete combustion of "coal" as a hydrocarbon compound, the estimation method of this disclosure can also be applied to chemical reactions other than incomplete combustion. Figure 4 shows an example of estimating the heat of reaction for a carbonization reaction (thermal decomposition under oxygen-free conditions) as another example of a reaction of coal. Here, it is assumed that an ideal carbonization reaction occurs. That is, the main product is "carbon C", and the other components are either gasified (hydrogen, oxygen, nitrogen) or remain as solid matter (S, ash). In this case, the enthalpy of formation of all products can be considered as "0", so it is possible to determine whether the reaction is exothermic or endothermic depending on whether the enthalpy of formation of coal is "positive" or "negative". For example, coal A and coal B have a "positive" enthalpy of formation, so they are exothermic reactions, while coal C has a "negative" enthalpy of formation, so it is an endothermic reaction. However, if hydrogen combustion (reaction of H and O) occurs during the carbonization reaction, potentially producing water, then H2O must be added to the product side to calculate the heat of reaction. Compared to the incomplete combustion reaction in Figure 3, the absolute value of the heat of reaction is considerably smaller, so the influence of the endothermic reaction is expected to be relatively small.

Claims

1. To express the molecular formula of a hydrocarbon compound selected from the group consisting of coal, coke, and biomass coal, per mole of carbon. The standard enthalpy of formation per mole of carbon is estimated stoichiometrically using the value of the heat of complete combustion of the hydrocarbon compound, and Based on the estimated standard enthalpy of formation per mole of carbon, estimate the endothermic and exothermic amount of the chemical reaction of the hydrocarbon compound. A method for estimating the heat of chemical reaction of hydrocarbon compounds containing hydrocarbons.

2. The method for estimating the heat of chemical reaction of a hydrocarbon compound according to claim 1, wherein the value of the heat of complete combustion is an actual measured value obtained from a complete combustion test.

3. The method for estimating the heat of chemical reaction of a hydrocarbon compound according to claim 1, wherein the value of the heat of complete combustion is an estimated value obtained by Dulong's formula.

4. A method for estimating the heat of chemical reaction of a hydrocarbon compound according to any one of claims 1 to 3, wherein the chemical reaction is an incomplete combustion reaction.

5. To estimate the heat of chemical reaction of multiple types of pulverized coal using the method for estimating the heat of chemical reaction of hydrocarbon compounds described in claim 4, and Select the pulverized coal to be introduced into the tuyeres of the blast furnace, taking into consideration the estimated heat of each chemical reaction of the aforementioned multiple types of pulverized coal. A method of operating a blast furnace, including [specific details omitted].

6. The method for operating a blast furnace according to claim 5, further comprising adjusting the conditions for heat compensation based on the difference between the estimated heat of chemical reaction of the pulverized coal before the change and the estimated heat of chemical reaction of the pulverized coal after the change, when changing the type of pulverized coal introduced into the tuyeres of the blast furnace.

Images