Method for producing cement clinker, and apparatus for producing cement clinker

Abstract

To prevent an increase in the concentration of carbon monoxide in the exhaust gas.SOLUTION: A method for producing cement clinker includes: a first feeding step of feeding a heat energy source including solids by a first feeding member to the inside of a heating furnace for heating cement raw materials; a second feeding step of feeding ammonia gas to the inside of the heating furnace by a second feeding member formed separately from the first feeding member; and a heating step of heating cement raw materials in the heating furnace while combusting ammonia gas, wherein in the second feeding step, the second feeding member feeds ammonia gas to the inside of the heating furnace from a different position from the position where the first feeding member feeds the heat energy source.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing cement clinker and an apparatus for manufacturing cement clinker.

Background Art

[0002] A cement clinker manufacturing apparatus generates cement clinker by firing cement raw materials in a firing furnace having a rotary kiln. In order to reduce the amount of carbon dioxide generated, attempts have been made to supply ammonia, which is a carbon-free energy source, to the firing furnace in addition to waste such as waste plastics and waste tires and biomass. For example, in Patent Document 1, in order to reduce the carbon dioxide emission amount, a technique has been proposed in which an ammonia-containing gas containing ammonia and air is injected from a burner section and burned in a rotary kiln together with fossil fuels and combustible wastes such as waste plastics.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present disclosure provides a method for manufacturing cement clinker and an apparatus for manufacturing cement clinker that are useful for suppressing an increase in the concentration of carbon monoxide in exhaust gas.

Means for Solving the Problems

[0005] [1] A method for producing cement clinker, comprising: a first supply step of supplying a thermal energy source containing solids to the inside of a heating furnace for heating cement raw materials using a first supply member; a second supply step of supplying ammonia gas to the inside of the heating furnace using a second supply member formed separately from the first supply member; and a heating step of heating cement raw materials in the heating furnace while burning the ammonia gas, wherein in the second supply step, the ammonia gas is supplied to the inside of the heating furnace by the second supply member from a position different from the position where the first supply member supplies the thermal energy source.

[0006] [2] The manufacturing method according to [1] above, wherein the solid content comprises at least one of pulverized coal and waste.

[0007] [3] The manufacturing method according to [1] or [2] above, wherein the heating furnace is a calcination furnace into which exhaust gas from a rotary kiln is introduced to calcine cement raw materials, and in the circumferential direction around the central axis of the calcination furnace, the first position in which the first supply member supplies the thermal energy source and the second position in which the second supply member supplies the ammonia gas are different from each other.

[0008] [4] The manufacturing method according to [3], wherein the oxygen concentration in the region containing the second position, among the plurality of regions obtained by partitioning the inside of the calcination furnace along the circumferential direction, is higher than the average value of the oxygen concentrations in the plurality of regions.

[0009] [5] The manufacturing method according to [4] above, wherein the oxygen concentration in the region including the second position is greater than 5% for 90% or more of the period during which the calcination furnace is in operation.

[0010] [6] A cement clinker manufacturing apparatus comprising: a heating furnace for heating cement raw materials; a first supply member for supplying a thermal energy source containing solids to the inside of the heating furnace; and a second supply member formed separately from the first supply member for supplying ammonia gas to the inside of the heating furnace, wherein the second supply member supplies the ammonia gas to the inside of the heating furnace from a position different from the position where the first supply member supplies the thermal energy source, and the ammonia gas is burned in the heating furnace. [Effects of the Invention]

[0011] This disclosure provides a method for producing cement clinker and an apparatus for producing cement clinker, which are useful for suppressing an increase in carbon monoxide concentration in exhaust gas. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a schematic diagram showing an example of a cement clinker manufacturing apparatus. [Figure 2] Figure 2 is a schematic side view showing an example of a calcination furnace and its surrounding components. [Figure 3] Figure 3 is a schematic cross-sectional view showing an example of the arrangement of supply components and the distribution of oxygen concentration. [Figure 4] Figure 4 is a schematic cross-sectional view showing an example of the arrangement of supply components and the distribution of carbon dioxide concentration. [Figure 5] Figure 5 is a graph showing an example of the change in carbon monoxide concentration over time at the outlet of a calcination furnace when solid matter and ammonia gas are introduced from the same location. [Figure 6] Figure 6 is a schematic side view showing an example of a rotary kiln and its surrounding components. [Modes for carrying out the invention]

[0013] An embodiment will be described below with reference to the drawings. In this description, the same elements or elements having the same function will be denoted by the same reference numeral, and redundant descriptions will be omitted. The following embodiment is illustrative for illustrating the present disclosure and is not intended to limit the present disclosure to the following content. Furthermore, the dimensional ratios of each element are not limited to those shown in the drawings.

[0014] [Cement clinker manufacturing equipment] Figure 1 schematically shows a cement clinker manufacturing apparatus according to one embodiment. The manufacturing apparatus 100 (cement clinker manufacturing apparatus) shown in Figure 1 is an apparatus that manufactures cement clinker, an intermediate cement product, by firing cement raw materials. The manufacturing apparatus 100 is equipped with an NSP (New Suspension Preheater) type preheating device. The manufacturing apparatus 100 is also called an NSP kiln. The manufacturing apparatus 100 includes, for example, cyclones C1, C2, C3, C4, a calcination furnace 30, a rotary kiln 40, and a clinker cooler 50.

[0015] Cyclones C1, C2, C3, C4 and the calcination furnace 30 function as preheaters for preheating and calcining the cement raw materials. The cement raw materials may include two or more selected from the group consisting of, for example, incinerated ash, coal ash, limestone, iron source, and slag. The cement raw materials are introduced from the connection between cyclone C1 and cyclone C2, heated as they flow through cyclone C1, cyclone C2, cyclone C3, calcination furnace 30, and cyclone C4, and introduced to the kiln end 42 of the rotary kiln 40. When introduced to the kiln end 42 of the rotary kiln 40, the cement raw materials are heated to, for example, 850°C to 1000°C, preferably 850°C to 900°C.

[0016] The pre - calciner 30 and the kiln end 42 of the rotary kiln 40 are connected by a rising duct 34. Through the rising duct 34, the exhaust gas from the rotary kiln 40 is introduced into the pre - calciner 30. The exhaust gas generated in the rotary kiln 40 contains combustion exhaust gas. The exhaust gas from the rotary kiln 40 flows through the pre - calciner 30, cyclone C4, cyclone C3, cyclone C2, and cyclone C1, and heat exchange occurs between the exhaust gas and the cement raw material.

[0017] The pre - calciner 30 calcines the cement raw material by the exhaust gas from the rotary kiln 40 and the heat - energy source supplied to the pre - calciner 30. That is, the pre - calciner 30 is a heating furnace that heats the cement raw material. At least a part of the pre - calciner 30 is formed in a cylindrical shape (see also Figure 2). In at least a part of the pre - calciner 30, the side wall of the pre - calciner 30 may extend along the central axis Ax of the pre - calciner 30. The central axis Ax is a virtual line, for example, a line extending along the vertical direction.

[0018] A probe 36 for extracting the exhaust gas in the rising duct 34 is connected to the rising duct 34. Downstream of the probe 36, chlorine bypass equipment having a cooler and a bag filter, etc. is installed, and the dust contained in the extracted gas (exhaust gas) extracted by the probe 36 is recovered. By installing the chlorine bypass equipment, volatile components such as chlorine - based compounds and alkalis can be reduced from within the manufacturing apparatus 100. Note that the probe 36 may be connected to the kiln end 42 instead of the rising duct 34, or may be connected to the boundary portion between the rising duct 34 and the kiln end 42.

[0019] The rotary kiln 40 fires cement raw materials to produce cement clinker (hereinafter sometimes simply referred to as "clinker"). That is, the rotary kiln 40 is a heating furnace that heats cement raw materials. The rotary kiln 40 includes a burner 44 that burns fuel. The burner 44 is disposed at the downstream end in the rotary kiln 40 (the end close to the clinker cooler 50). By combustion in the burner 44, the cement raw materials are heated to, for example, 1300°C to 1450°C in the rotary kiln 40. In the rotary kiln 40, the preheated and calcined cement raw materials are heated by the combustion of the burner 44 to become clinker.

[0020] The clinker produced in the rotary kiln 40 is discharged to the clinker cooler 50. In the clinker cooler 50, the clinker is cooled by cooling air such as outside air. The clinker after being cooled in the clinker cooler 50 is discharged from the manufacturing apparatus 100. A part of the gas after being used for cooling the clinker in the clinker cooler 50 may be introduced into the calciner 30 as cooler extraction air. Hereinafter, the introduction of the heat energy source into the rotary kiln 40 and the calciner 30 will be described.

[0021] <Introduction of Heat Energy Source> In the rotary kiln 40, since the cement raw materials are heated under high temperature conditions compared to the calciner 30, it is preferable that the cement raw materials are heated by radiative heat transfer rather than convective heat transfer. The contribution rate of radiative heat transfer to the total heat transfer to the cement raw materials in the rotary kiln 40 may be 60% or more, or may be 70% or more. By operating the manufacturing apparatus 100 under operating conditions such that the contribution rate of radiative heat transfer in the rotary kiln 40 is increased, the energy efficiency can be improved.

[0022] From the viewpoint of increasing the contribution rate of radiant heat transfer, the heat energy source burned in burner 44 may include fossil fuels containing carbon. Examples of fossil fuels include heavy oil, petroleum coke, and coal (pulverized coal). By using fossil fuels, the concentration of carbon dioxide in the combustion exhaust gas increases, and the contribution rate of radiant heat transfer can be sufficiently increased. In burner 44, ammonia may also be burned as the heat energy source. However, if the amount of ammonia gas introduced into rotary kiln 40 increases, the concentration of carbon dioxide in the combustion exhaust gas decreases, which lowers the contribution rate of radiant heat transfer and may reduce energy efficiency.

[0023] From the perspective of ensuring sufficiently high energy efficiency in the rotary kiln 40, the amount of ammonia introduced into the rotary kiln 40 may be small. For example, the amount of ammonia introduced into the rotary kiln 40 is less than the amount of ammonia introduced into the calcination furnace 30. Furthermore, ammonia does not necessarily have to be introduced into the rotary kiln 40. When starting operation of the rotary kiln 40 after a shutdown, ammonia gas may be introduced as a thermal energy source. During such a startup, it is necessary to raise the temperature, which tends to increase fossil fuel consumption and NOx (nitrogen oxides) compared to steady-state operation. Therefore, by introducing ammonia gas from, for example, the burner 44, the NOx concentration can be reduced.

[0024] The manufacturing apparatus 100 includes a supply member 60 (first supply member). The supply member 60 is a member (burner) that supplies a heat energy source containing solid matter (solid heat energy source) to the inside of the calcination furnace 30. The supply member 60 may also supply solid matter and combustion air to the inside of the calcination furnace 30. An inlet 62 is provided at the end of the supply member 60 for discharging (blowing in) solid matter and combustion air into the inside of the calcination furnace 30.

[0025] The end of the supply member 60 that includes the inlet 62 functions as a nozzle. The end of the supply member 60 that functions as a nozzle may be installed horizontally. The end of the supply member 60 that functions as a nozzle may be installed so that the inlet 62 faces the central axis Ax. The above end of the supply member 60 may be connected to the side wall of the calcination furnace 30. The position where the supply member 60 supplies solids to the calcination furnace 30 corresponds to the position of the inlet 62.

[0026] The supply member 60 transports the solid material and combustion air to, for example, the inlet 62 (nozzle portion). The supply member 60 may also supply the solid material and combustion air separately to the inside of the calcination furnace 30. In this case, the inlet 62 includes one or more openings for introducing the solid material and one or more openings for introducing the combustion air. Furthermore, the solid material is not mixed with the combustion air while being transported by the supply member 60.

[0027] The solids include, for example, at least one of pulverized coal and waste. The waste supplied to the inside of the calcination furnace 30 may include one or more types of waste such as waste plastic, RDF (Refuse Derived Fuel), or meat and bone meal. The supply member 60 may supply pulverized coal and combustion air, waste and combustion air, or pulverized coal, waste and combustion air. As described above, the supply member 60 may supply the solids and combustion air to the inside of the calcination furnace 30 from the same location.

[0028] The manufacturing apparatus 100 includes a supply member 70 (second supply member). The supply member 70 is a member (burner) that supplies ammonia-containing gas, including ammonia, as a thermal energy source to the inside of the calcination furnace 30. The ammonia-containing gas may contain only ammonia gas, or it may be a mixture of ammonia gas and other gases such as air or methane. In one example, exhaust gas from a chlorine bypass facility is mixed with the ammonia gas as combustion air in the supply member 70. The supply member 70 may continuously supply the ammonia-containing gas during the period in which the calcination furnace 30 is operating, or it may supply the ammonia-containing gas only for a part of the period in which the calcination furnace 30 is operating.

[0029] A portion of the ammonia-containing gas supplied from the supply member 70 may be used as a thermal energy source, and another portion may be used for denitrification. That is, the reaction may occur not only as shown in formula (1) below, but also as shown in formula (2). NH3 + 1 / 4O2 → 1 / 2N2 + 3 / 2H2O (1) NH3 + NO + 1 / 4O2 → N2 + 3 / 2H2O (2)

[0030] Since the calcination furnace 30 is in a temperature range where both combustion and denitrification reactions can proceed, it can carry out both the combustion and denitrification reactions of ammonia. This makes it possible to reduce emissions of both carbon dioxide and nitrogen oxides.

[0031] The ammonia contained in the ammonia-containing gas supplied from the supply member 70 may undergo both combustion and denitrification in the calcination furnace 30, or all or most of the ammonia from the supply member 70 may be used for the combustion reaction, and the ammonia used for the denitrification reaction may be supplied from an inlet 20 located at a different location from the supply member 70. The ammonia-containing gas supplied from the inlet 20 may contain only ammonia, or it may be a mixture of ammonia gas and other gases. The inlet 20 is provided, for example, in a connection section 38 that connects the upper part (outlet) of the calcination furnace 30 to the cyclone C4, and through which exhaust gas from the calcination furnace 30 flows.

[0032] The supply member 70 is formed separately from the supply member 60. That is, the supply member 70 is physically separated from the supply member 60. An inlet 72 is provided at the end of the supply member 70 for discharging (blowing in) ammonia-containing gas into the calcination furnace 30. The end of the supply member 70 including the inlet 72 functions as a nozzle. The inlet 72 may be provided with one or more openings for introducing ammonia-containing gas.

[0033] The nozzle end of the supply member 70 may be installed horizontally. The nozzle end of the supply member 70 may be installed so that the inlet 72 faces the central axis Ax. The supply member 70 may discharge ammonia-containing gas toward the central axis Ax. The above-mentioned end of the supply member 70 may be connected to the side wall of the calcination furnace 30. In addition, the end of the supply member 70 may be connected to a location in the side wall of the calcination furnace 30 where an opening is provided, so that the opening functions as the inlet 72. The position where the supply member 70 supplies ammonia-containing gas to the calcination furnace 30 corresponds to the position of the inlet 72. In the direction along the central axis Ax of the calcination furnace 30 (for example, the vertical direction), the height position of at least a portion of the inlet 72 may be the same as the height position of at least a portion of the inlet 62 of the supply member 60.

[0034] The supply member 70 discharges ammonia gas from a different position than the supply member 60 that supplies the thermal energy source. In other words, the position from which the supply member 60 supplies solid matter to the inside of the calcination furnace 30 and the position from which the supply member 70 supplies ammonia gas to the inside of the calcination furnace 30 are different from each other. In this disclosure, supplying (discharging) thermal energy sources from different positions (locations) means that two supply members, which are configured as separate entities, each supply (discharge) a thermal energy source.

[0035] Figure 3 schematically shows a cross-section of the calcination furnace 30 when it is horizontally cut at the height where the inlets 62 and 72 are provided, and viewed from above. In the example shown in Figure 3, cooler bleed air from the clinker cooler 50 is introduced into the calcination furnace 30 through two inlets. The two inlets for introducing the cooler bleed air are located below inlets 62 and 72.

[0036] In the circumferential direction around the central axis Ax of the calcination furnace 30 (hereinafter simply referred to as the "circumferential direction"), the position where the supply member 60 supplies solid matter (first position) and the position where the supply member 70 supplies ammonia-containing gas (second position) are different from each other. In the circumferential direction (viewed from the direction along the central axis Ax), the inlet 72 of the supply member 70 does not overlap with the inlet 62 of the supply member 60. For example, in the circumferential direction, the position of the inlet 72 differs from the inlet 62 by 10° or more, 15° or more, 20° or more, 25° or more, or 30° or more.

[0037] The temperature inside the calcination furnace 30 is, for example, 850° to 1000°C, preferably 850° to 900°C, which is lower than the temperature inside the rotary kiln 40. Therefore, the proportion of heat transfer by radiant heat transfer when heating cement raw materials in the calcination furnace 30 is lower than in the rotary kiln 40, and the proportion of heat transfer by convection is higher in the calcination furnace 30. As a result, even if at least a portion of the carbon-containing fossil fuels in the calcination furnace 30 is replaced with ammonia, a high level of energy efficiency can be sufficiently maintained. In addition, carbon dioxide emissions can be sufficiently reduced.

[0038] Inside the calcination furnace 30, regions with relatively low oxygen concentrations and regions with relatively high oxygen concentrations are formed. Figure 3 also shows the distribution of oxygen concentration (%) measured at a certain time. In Figure 3, the differences in the range of oxygen concentration (%) are shown by four levels of color intensity. Specifically, the four regions—a region with an oxygen concentration of over 10%, a region of 8% to 10%, a region of 5% to 8%, and a region of 5% or less—are represented by different levels of intensity. It is thought that the uneven distribution of oxygen concentration inside the calcination furnace 30 occurs due to the location where a thermal energy source other than ammonia (e.g., waste) is supplied, and / or the location and direction of air introduction into the calcination furnace 30, such as cooler extraction air.

[0039] Furthermore, Figure 4 shows the distribution of carbon dioxide concentration (%) measured at the same time as the distribution of oxygen concentration (%) shown in Figure 3. In Figure 4, as in Figure 3, the differences in the range of carbon dioxide concentration (%) are shown by four levels of color intensity. Specifically, the four regions of carbon dioxide concentration—above 25%, between 20% and 25%, between 15% and 20%, and below 15%—are represented by different levels of intensity. Comparing the concentration distributions shown in Figures 3 and 4, it can be seen that in regions with relatively low oxygen concentration, carbon dioxide concentration is relatively high, and in regions with relatively high oxygen concentration, carbon dioxide concentration is relatively low. Note that when the concentration distributions shown in Figures 3 and 4 were measured, the thermal energy source for the solid matter was supplied by a supply member 60A, which is separate from supply member 60. Supply member 60A is positioned in a different location from supply members 60 and 70 in the circumferential direction.

[0040] The oxygen and carbon dioxide concentrations inside the calcination furnace 30 can be measured, for example, as follows: At multiple measurement points located at different positions in at least one of the circumferential and radial directions, the oxygen concentration is measured using an electrochemical gas analyzer conforming to JIS B7983, and the carbon dioxide concentration is measured using an infrared absorption gas analyzer conforming to JIS B7986. Then, around each of the multiple measurement points from which measurements were obtained, an estimated value is calculated at an arbitrary point, assuming a linear relationship between adjacent measurement points. The multiple measurement points may include four or more measurement points located at different positions in the circumferential direction.

[0041] Inside the calcination furnace 30, the oxygen and carbon dioxide concentrations may fluctuate over time. However, in a concentration distribution inside the calcination furnace 30 that includes regions with relatively low oxygen concentrations and regions with relatively high oxygen concentrations, a similar trend will appear even at different times. That is, by observing the average value over time, it is possible to evaluate the relative magnitude of the oxygen concentration even if the absolute values ​​at each time point are different. Furthermore, during the operation of the calcination furnace 30, the oxygen and carbon dioxide concentrations may be measured at each of the above measurement points with a measurement cycle of 1 to 30 minutes (every 1 to 30 minutes). In addition, the oxygen and carbon dioxide concentrations may be measured including the period during which ammonia-containing gas is supplied.

[0042] The supply member 70 is configured to discharge (blow in) ammonia-containing gas towards areas within the calcination furnace 30 where the oxygen concentration is relatively high. Specifically, the oxygen concentration in the area containing the location where the supply member 70 supplies ammonia-containing gas (the location of the inlet 72), among the multiple areas obtained by partitioning the inside of the calcination furnace 30 along the circumferential direction, is higher than the average value of the oxygen concentrations in the above multiple areas. This point will be explained below using the example of partitioning the inside of the calcination furnace 30 into four fan-shaped areas arranged in the circumferential direction.

[0043] In one example, the interior of the calcination furnace 30 is divided into four regions at 90° intervals in the circumferential direction. In this case, the central angle of one sector-shaped region is 90°. Furthermore, in the region where the inlet 72 will be located, the four regions are divided such that the center of the inlet 72 is located in the center of that region in the circumferential direction. In Figures 3 and 4, the region where the inlet 72 is located is shown as "R1", and the other three regions are shown as "R2", "R3", and "R4", respectively. Regions R1 to R4 are arranged in this order in the circumferential direction. Regions R1 to R4 are two-dimensional regions in the cross-section of the interior of the calcination furnace 30 at the height position where the inlet 72 is provided.

[0044] In each of the regions R1 to R4, the oxygen concentration is measured at at least one measurement point. The oxygen concentration in a single region is obtained by calculating the arithmetic mean of the measured oxygen concentrations at one or more measurement points within that region for each measurement period, and then calculating the time average of these arithmetic mean values ​​per hour. The oxygen concentration in region R1 is greater than the average oxygen concentration in regions R1 to R4. The average oxygen concentration in regions R1 to R4 is obtained by adding the oxygen concentrations in regions R1, R2, R3, and R4, and then dividing by 4. As described above, the supply member 70 is positioned such that the oxygen concentration in the region where the inlet 72 is located, among the multiple regions partitioned circumferentially based on the position of the inlet 72, is higher than the average oxygen concentration in all regions including that region.

[0045] As will be described later, the carbon monoxide concentration may increase due to the reaction between ammonia and carbon dioxide. From the viewpoint of reducing the reaction between ammonia and carbon dioxide from the supply member 70, the oxygen concentration in region R1 may be greater than 5% for more than 90% of the period during which the calcination furnace 30 is in operation. For more than 90% of the period during which the calcination furnace 30 is in operation, the oxygen concentration in region R1 may be greater than 6%, greater than 7%, or greater than 8%.

[0046] In each of the regions R1 to R4, carbon dioxide concentration is measured at at least one measurement point. The carbon dioxide concentration in a single region is obtained by calculating the arithmetic mean of the measured carbon dioxide concentrations at one or more measurement points within that region for each measurement period, and then calculating the time average of these arithmetic mean values ​​per hour. The carbon dioxide concentration in region R1 is smaller than the average carbon dioxide concentration in regions R1 to R4. The average carbon dioxide concentration in regions R1 to R4 is obtained by adding the carbon dioxide concentrations in regions R1, R2, R3, and R4, and then dividing by 4. As described above, the supply member 70 is positioned such that the carbon dioxide concentration in the region where the inlet 72 is located, among the multiple regions partitioned in the circumferential direction based on the position of the inlet 72, is lower than the average carbon dioxide concentration in all regions including that region.

[0047] From the viewpoint of reducing the reaction between ammonia and carbon dioxide from the supply member 70, the carbon dioxide concentration in region R1 may be less than 20% for more than 90% of the operating period of the calcination furnace 30. The carbon dioxide concentration in region R1 may be less than 19% or less than 18% for more than 90% of the operating period of the calcination furnace 30.

[0048] [Method for producing cement clinker] Next, as an example of a method for manufacturing cement clinker, the clinker manufacturing process performed in the manufacturing apparatus 100 will be described. The manufacturing process performed in the manufacturing apparatus 100 includes, for example, a preheating step, a calcination step, a firing step, and a cooling step. These steps are performed for at least partially overlapping periods. The preheating step is a process in which the cement raw materials are preheated in cyclones C1 to C4 with high-temperature gas, including exhaust gas from the rotary kiln 40.

[0049] The calcination process is a process in which the cement raw materials are calcined in the calcination furnace 30 using exhaust gas from the rotary kiln 40 and various heat energy sources supplied to the inside of the calcination furnace 30. The firing process is a process in which the cement raw materials are fired in the rotary kiln 40 using combustion gas from the burner 44. The cooling process is a process in which the clinker produced in the rotary kiln 40 is cooled in the clinker cooler 50.

[0050] An example of the above calcination process will now be described in detail. The calcination process includes, for example, a first supply process, a second supply process, and a heating process. The first supply process, the second supply process, and the heating process are each performed for at least partially overlapping periods. The first supply process is a process of supplying a thermal energy source containing solid matter to the inside of the calcination furnace 30 by a supply member 60. The solid matter supplied from the supply member 60 in the first supply process may be pulverized coal, waste, or both pulverized coal and waste.

[0051] The second supply step is a step in which ammonia gas is supplied to the inside of the calcination furnace 30 by a supply member 70 which is formed separately from the supply member 60. In the second supply step, ammonia gas is supplied by the supply member 70 from a position different from the position where the supply member 60 supplies the heat energy source. For example, in the second supply step, ammonia-containing gas is supplied from an inlet 72 which is located at a different position (at a different angle) than the inlet 62 of the supply member 60 in the circumferential direction around the central axis Ax of the calcination furnace 30.

[0052] The heating process involves heating the cement raw materials in the calcination furnace 30 while burning ammonia gas. The calcination process may also include a denitrification process. For example, in the denitrification process, ammonia-containing gas is supplied into the connection part 38 from an inlet 20 provided in the connection part 38 that connects the upper part (outlet) of the calcination furnace 30 to the cyclone C4. This allows for denitrification treatment of the exhaust gas used for calcination in the calcination furnace 30.

[0053] <Regarding the increase in carbon monoxide concentration> Figure 5 shows the results of measuring the change in carbon monoxide concentration at the outlet of the calcination furnace 30 over time when solids and ammonia gas are introduced from the same location, unlike the example described above. In the graph shown in Figure 5, period T1 represents the period during which ammonia gas is supplied from a component (burner) that supplies solids and ammonia gas from the same location. During periods other than period T1, ammonia gas is not supplied, but solids are supplied. Pulverized coal is supplied as solids from the above component. The inlet of the above component is provided with multiple openings (inlets) for supplying solids and multiple openings (inlets) for supplying ammonia gas. In addition, waste is supplied into the calcination furnace 30 by a component different from the component that supplies solids and ammonia gas.

[0054] The measurement results shown in Figure 5 indicate that the carbon monoxide concentration in the gas discharged from the outlet of the calcination furnace 30 increases significantly due to the supply of ammonia gas. In other words, it was found that supplying ammonia gas to the inside of the calcination furnace 30 causes a rapid increase in carbon monoxide concentration. Two possible factors contribute to the increase in carbon monoxide concentration. (A) Inhibition of combustion of solids such as pulverized coal due to combustion of ammonia gas (B) Reaction of ammonia with carbon dioxide

[0055] To elaborate on factor (A), gas is thought to burn faster than solids. Therefore, if ammonia gas and solids such as pulverized coal are supplied from the same location, the ammonia gas will burn first, causing incomplete combustion of the solids and an increase in carbon monoxide concentration. For this reason, as in the example above, supplying ammonia gas into the calcination furnace 30 from a location different from where the solids are supplied by the supply member 70 can suppress the increase in carbon monoxide concentration.

[0056] To elaborate on factor (B), the reaction between ammonia and carbon dioxide is shown by equation (3) below. Since carbon monoxide is produced by the reaction shown by equation (3) below, it is thought that the carbon monoxide concentration will rise if the carbon dioxide concentration is high in the region where ammonia is supplied, or in other words, if the oxygen concentration in that region is low. Therefore, as in the example above, the rise in carbon monoxide concentration can be suppressed by arranging the supply member 70 so that the oxygen concentration is high in the region including the position where the supply member 70 supplies ammonia gas. NH3 + 3CO2 → N2 + 3H2O + 3CO (3)

[0057] [Differentiation] Although one embodiment has been described above, this disclosure is not limited in any way to the above embodiment. If factor (A) contributes more significantly to the increase in carbon monoxide concentration than factor (B), the supply member 70 does not need to supply ammonia-containing gas to a region with a relatively high oxygen concentration. That is, the oxygen concentration in region R1, which includes the position where the supply member 70 supplies ammonia gas, does not need to be higher than the average value of the oxygen concentrations in regions R1 to R4.

[0058] The height position of the inlet 72 of the supply member 70 may differ from the height position of the inlet 62 of the supply member 60. In this case, the region R1 to R4 in which the relative magnitudes of oxygen concentrations are evaluated is set at the height position of the inlet 72. When pulverized coal is supplied as solid matter from the supply member 60, waste may be supplied to the inside of the calcination furnace 30 from a supply member other than the supply member 60 and the supply member 70. Pulverized coal may be supplied from both the supply member 60 and one or more other supply members (for example, the supply member 60A shown in Figure 3, etc.).

[0059] The method for producing cement clinker may be carried out in a manufacturing apparatus different from the manufacturing apparatus 100. In the cement clinker manufacturing apparatus, the number of cyclones for preheating the cement raw materials is not particularly limited and may be three or fewer, or five or more.

[0060] In place of, or in addition to, the calcination furnace 30, solids and ammonia gas may be supplied separately from different locations to the rotary kiln 40. Figure 6 schematically shows the connection between the downstream end of the rotary kiln 40 and the clinker cooler 50. In Figure 6, clinker is indicated by "Cl". The clinker Cl produced in the rotary kiln 40 is discharged to the clinker cooler 50, where the clinker Cl is cooled by cold air.

[0061] In one example, the burner 44 supplies pulverized coal (solids), waste (solids), and combustion air to the interior of the rotary kiln 40 through corresponding openings formed in the burner 44. At the downstream end of the rotary kiln 40, in addition to the burner 44 (first supply member), a separate supply member 80 (second supply member) is provided. The supply member 80 is a burner that supplies ammonia-containing gas to the interior of the rotary kiln 40.

[0062] In the example shown in Figure 6, when viewed from upstream to downstream inside the rotary kiln 40, the opening for supplying solids and the opening for supplying ammonia gas are not located within the region enclosed by the outer edge of one of the members that supplies the thermal energy source. In other words, the inlet of the burner 44 and the inlet of the supply member 80 are physically separated. This suppresses the inhibition of solid combustion caused by the combustion of ammonia gas and can suppress the increase in carbon monoxide concentration in the exhaust gas from the rotary kiln 40.

[0063] In one of the various examples described above, at least some of the matters described in the other examples may be combined.

[0064] [Summary of this disclosure] The method for producing cement clinker described above includes: a first supply step of supplying a thermal energy source containing solids to the inside of a heating furnace (30, 40) for heating cement raw materials using a first supply member (60, 44); a second supply step of supplying ammonia gas to the inside of the heating furnace (30, 40) using a second supply member (70, 80) formed separately from the first supply member (60, 44); and a heating step of heating the cement raw materials in the heating furnace (30, 40) while burning the ammonia gas. In the second supply step, the second supply member (70, 80) supplies ammonia gas to the inside of the heating furnace (30, 40) from a position different from the position where the first supply member (60, 44) supplies the thermal energy source. In this production method, the position where the ammonia gas is supplied is different from the position where the solids are supplied, making it less likely for combustion inhibition of the solids to occur due to the combustion of ammonia. Therefore, this production method is useful for suppressing the rise in carbon monoxide concentration in the exhaust gas from the heating furnace. Furthermore, concerns arising from the increase in carbon monoxide concentration include the fact that carbon monoxide is toxic and its concentration can affect the human body, as well as the generation and combustion of carbon monoxide in unexpected locations, and the inhibition of pulverized coal combustion due to the formation of a reducing atmosphere.

[0065] In the manufacturing method described above, the solid content may include at least one of pulverized coal and waste. If pulverized coal or waste is supplied from the same component (same location) as ammonia gas, the combustion of ammonia gas may cause incomplete combustion of the pulverized coal, etc. In contrast, in the above method, ammonia gas is supplied from a location different from that of the pulverized coal, etc., thus reducing the possibility of incomplete combustion of the pulverized coal, etc.

[0066] In the manufacturing method described above, the heating furnace may be a calcination furnace (30) into which exhaust gas from a rotary kiln (40) is introduced to calcine the cement raw materials. In the circumferential direction around the central axis (Ax) of the calcination furnace (30), the first position where the first supply member (60) supplies the thermal energy source and the second position where the second supply member (70) supplies ammonia gas may be different from each other. In this case, combustion inhibition of solids due to the combustion of ammonia is less likely to occur in the calcination furnace (30). Therefore, the increase in carbon monoxide concentration in the exhaust gas from the calcination furnace (30) caused by the supply of ammonia gas can be suppressed.

[0067] In the manufacturing method described above, the oxygen concentration in the region (R1) containing the second position among the multiple regions (R1 to R4) obtained by partitioning the inside of the calcination furnace (30) along the circumferential direction may be higher than the average value of the oxygen concentrations in the multiple regions (R1 to R4). When the oxygen concentration is high, the carbon dioxide concentration tends to be low. Therefore, in the above method, the amount of ammonia that reacts with carbon dioxide inside the calcination furnace 30 is reduced. Consequently, the increase in carbon monoxide concentration in the exhaust gas from the calcination furnace (30) caused by the supply of ammonia gas can be suppressed.

[0068] In the manufacturing method described above, the oxygen concentration in the region (R1) containing the second position may be greater than 5% for more than 90% of the operating period of the calcination furnace (30). In this case, the amount of ammonia that reacts with carbon dioxide inside the calcination furnace (30) is further reduced. Therefore, the increase in carbon monoxide concentration in the exhaust gas from the calcination furnace (30) caused by the supply of ammonia gas can be further suppressed.

[0069] The cement clinker manufacturing apparatus (100) described above comprises a heating furnace (30, 40) for heating cement raw materials, a first supply member (60, 44) for supplying a thermal energy source containing solids to the inside of the heating furnace (30, 40), and a second supply member (70, 80) formed separately from the first supply member (60, 44) for supplying ammonia gas to the inside of the heating furnace (30, 40). The second supply member (70, 80) supplies ammonia gas to the inside of the heating furnace (30, 40) from a position different from the position where the first supply member (60, 44) supplies the thermal energy source. The manufacturing apparatus (100) burns the ammonia gas in the heating furnace (30, 40). This manufacturing apparatus (100), like the manufacturing method described above, is useful in suppressing the rise in carbon monoxide concentration in the exhaust gas. [Explanation of symbols]

[0070] 100...Cement clinker manufacturing equipment, C1, C2, C3, C4...Cyclone, 30...Calibration furnace, 40...Rotary kiln, 44...Burner, 50...Clinker cooler, 60, 70, 80...Supply components.

Claims

1. A first supply step in which exhaust gas from a rotary kiln is introduced and a first supply member supplies a thermal energy source containing solids to the inside of a calcination furnace in which cement raw materials are calcined, A second supply step involves supplying ammonia gas to the inside of the calcination furnace using a second supply member formed separately from the first supply member, In the aforementioned calcination furnace, a heating step is performed in which the cement raw materials are heated while the ammonia gas is burned, The process includes supplying gas extracted from a clinker cooler that cools the cement clinker produced in the rotary kiln to the inside of the calcination furnace, In the second supply step, the ammonia gas is supplied to the inside of the calcination furnace by the second supply member from a position different from the position where the first supply member supplies the heat energy source. A method for manufacturing cement clinker, wherein in the second supply step, the position at which the ammonia gas is supplied into the calcination furnace by the second supply member is different from the position at which the gas extracted from the clinker cooler is supplied into the calcination furnace.

2. The manufacturing method according to claim 1, wherein the solid content includes at least one of pulverized coal and waste.

3. The manufacturing method according to claim 1 or 2, wherein, in the circumferential direction around the central axis of the calcination furnace, the first position where the first supply member supplies the thermal energy source and the second position where the second supply member supplies the ammonia gas are different from each other.

4. The central axis of the calcination furnace extends in the vertical direction, The manufacturing method according to claim 1 or 2, wherein at least a portion of the inlet of the thermal energy source in the first supply member and at least a portion of the inlet of the ammonia gas in the second supply member are located at the same height as each other.

5. The central axis of the calcination furnace extends in the vertical direction, The manufacturing method according to claim 1 or 2, wherein the inlet for introducing gas extracted from the clinker cooler into the interior of the calcination furnace is located below the inlet for the thermal energy source in the first supply member and the inlet for the ammonia gas in the second supply member.

6. A rotary kiln and Exhaust gas from the rotary kiln is introduced into a calcination furnace for calcining cement raw materials, A clinker cooler for cooling the cement clinker produced in the rotary kiln, A first supply member supplies a thermal energy source containing solid matter to the inside of the calcination furnace, The system includes a second supply member, which is formed separately from the first supply member and supplies ammonia gas to the inside of the calcination furnace, The second supply member supplies the ammonia gas into the calcination furnace from a position different from the position where the first supply member supplies the heat energy source. In the aforementioned calcination furnace, the ammonia gas is burned, The gas extracted from the clinker cooler is supplied to the inside of the calcination furnace. A cement clinker manufacturing apparatus, wherein the position in which the ammonia gas is supplied to the inside of the calcination furnace by the second supply member is different from the position in which the gas extracted from the clinker cooler is supplied to the inside of the calcination furnace.

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