JP7539329B2 - Chlorine bypass system and method of operating same - Google Patents

Description

The present invention relates to a chlorine bypass system and its operating method.

Chlorine bypass systems are introduced to prevent coating problems inside the kiln or preheater caused by chlorine and ensure stable kiln operation. In line with the promotion of using waste as a raw fuel, efforts are being made to increase the processing capacity of chlorine bypass systems. In particular, in recent years, the amount of chlorine brought into the kiln has been increasing due to an increase in the amount of waste plastic and other waste being processed, so there are considerations being given to increasing the amount of chlorine bypassed.

For example, Patent Document 1 discloses that in a chlorine bypass facility (chlorine bypass system), the bleed probe and cyclone are arranged in parallel in two systems. When the bypass rate (bleed air volume) is higher than 50% of the maximum bypass rate, air is bled from both bleed probes in the two systems and classified by the cyclones in the two systems. When the bypass rate is 50% or less of the maximum bypass rate, air is bled from only one bleed probe and classified by only one cyclone.

Patent Document 2 also discloses that in a clinker calcining device, an air extraction pipe is connected to two different points of the kiln, and the bleed gas extracted by each air extraction pipe is cooled by a cooler and then introduced into a single mixer. The amount of bleed gas extracted is adjustable by a damper.

Patent No. 3115545 Patent No. 6631293

However, the technology described in Patent Document 1 has the problem that the amount of dust increases and the chlorine bypass efficiency decreases due to an increase in the amount of bleed gas in each system. Also, the technology described in Patent Document 2 has the problem that the amount of dust increases and the chlorine bypass efficiency decreases, as in the conventional technology, because the chlorine bypass system itself is a single system.

The object of the present invention is to provide a chlorine bypass system and an operating method thereof that can improve chlorine bypass efficiency.

The chlorine bypass system of the present invention comprises a first bleed probe and a second bleed probe each for bleeding a portion of combustion gas from the bottom of a single cement kiln, a first bleed gas suction means for sucking the bleed gas with the first bleed probe, a first classification means for separating coarse dust particles in the bleed gas bled with the first bleed probe, a first dust concentration measurement means for measuring the dust concentration in the bleed gas introduced into the first classification means, a first dust collection means for collecting fine dust particles in the bleed gas after the coarse particles have been separated by the first classification means, a second bleed gas suction means for sucking the bleed gas with the second bleed probe, and The bleed gas extracting system comprises: a second classification means for separating coarse dust particles in the bleed gas bled by a second bleed probe; a second dust concentration measuring means for measuring a dust concentration in the bleed gas to be introduced into the second classification means; a second dust collecting means for collecting fine dust particles in the bleed gas after the coarse particles have been separated by the second classification means; and a control means for controlling the suction flow rate of the bleed gas of at least one of the first bleed gas suction means and the second bleed gas suction means so that a ratio of a first dust concentration measured by the first dust concentration measuring means to a second dust concentration measured by the second dust concentration measuring means is in a range of 0.6 to 1.8.

The method for operating a chlorine bypass system of the present invention includes a first bleed probe and a second bleed probe each for bleeding a portion of combustion gas from the bottom of a single cement kiln, a first bleed gas suction means for sucking the bleed gas with the first bleed probe, a first classification means for separating coarse particles of dust in the bleed gas bled with the first bleed probe, a first dust concentration measurement means for measuring the dust concentration in the bleed gas introduced into the first classification means, a first dust collection means for collecting fine particles of dust in the bleed gas after the coarse particles have been separated by the first classification means, a second bleed gas suction means for sucking the bleed gas with the second bleed probe, and A method for operating a chlorine bypass system comprising a second classification means for separating coarse dust particles in the bleed gas bled through a sump, a second dust concentration measurement means for measuring a dust concentration in the bleed gas introduced into the second classification means, and a second dust collection means for collecting fine dust particles in the bleed gas after the coarse particles have been separated by the second classification means, characterized in that the method comprises operating the system so as to adjust the suction flow rates of the bleed gas of at least one of the first bleed gas suction means and the second bleed gas suction means so that a ratio of a first dust concentration measured by the first dust concentration measurement means to a second dust concentration measured by the second dust concentration measurement means is in a range of 0.6 to 1.8.

As can be seen from the simulation results of the present invention described below, in the chlorine bypass system and its operating method of the present invention, by controlling or adjusting the suction flow rate of at least one of the bleed gases of the first bleed gas suction means and the second bleed gas suction means so that the ratio of the first dust concentration to the second dust concentration is in the range of 0.6 to 1.8, the amount of fines collected by the first and second dust collection means can be reduced, and the chlorine bypass efficiency can be improved.

FIG. 1 is a schematic diagram showing a chlorine bypass system according to an embodiment of the present invention. This is a perspective view of a geometric model of the area around the end of a cement kiln created for use in the simulation.

The chlorine bypass system 100 according to the embodiment of the present invention will be described. With reference to FIG. 1, the chlorine bypass system 100 is equipped with two chlorine bypass systems 20 and 30 that extract a portion of the combustion gas from the bottom 11 of the cement kiln 10 in the cement kiln facility and bypass (remove) chlorine from the extracted gas. Each of the chlorine bypass systems 20 and 30 has the same configuration as the conventional system.

Here, the first chlorine bypass system 20 is equipped with a first bleed probe 21, a first bleed gas suction means 22, a first cooling means 23, a first classification means 24, a first dust concentration measurement means 25, a first dust collection means 26, a first exhaust means 27, etc. on the first kiln bleed gas flow path 28.

Here, in the first chlorine bypass system 20, the first bleed probe 21 is provided at the kiln end 11 of the cement kiln 10, and passes through the bleed gas, which is a part of the combustion gas bled from the cement kiln 10, and is formed, for example, in a cylindrical shape. The first bleed gas suction means 22 is provided to suck the bleed gas through the first bleed probe 21, and is, for example, a suction fan. The bleed gas sent to the first bleed probe 21 is rapidly cooled, for example, to 550°C or less by the first cooling means 23 such as a cooling fan. This produces microcrystals of chlorine compounds.

The first classification means 24 separates the coarse dust particles P1 (raw dust) from the bleed gas bled by the first bleed probe 21, and is, for example, a cyclone classifier. The first classification means 24 separates, for example, particles with a particle size of more than 12 μm as coarse dust P1.

The first dust concentration measuring means 25 measures the dust concentration W1 in the bleed gas introduced into the first classification means 24. The first dust concentration measuring means 25 is, for example, a commercially available concentration meter that measures dust concentration using a light scattering method. Alternatively, the dust concentration W1 may be measured directly by an operator sampling the bleed gas.

The first dust collecting means 26 collects fine powder (chlorine bypass dust) P2 from the dust in the bleed gas that has been separated from the coarse powder P1 by the first classification means 24 and further cooled by the first cooler 29, and is, for example, a solids collector such as various electrostatic precipitators or a bag filter. The bleed gas (exhaust gas) discharged from the first dust collecting means 26 is drawn by the first exhaust means 27 such as an exhaust fan and returned to the exhaust gas system of the cement kiln, i.e., the outlet side of the fan that draws the exhaust gas from the cement kiln or to a preheater attached to the cement kiln, although not shown.

Here, the second chlorine bypass system 30, like the first chlorine bypass system 20, is equipped with a second bleed probe 31, a second bleed gas suction means 32, a second cooling means 33, a second classification means 34, a second dust concentration measurement means 35, a second dust collection means 36, a second exhaust means 37, and the like, on the second kiln bleed gas flow path 38. The components 31 to 38 of the second chlorine bypass system 30 are equivalent to the components 21 to 28 of the first chlorine bypass system 20, so their description will be omitted.

The chlorine bypass system 100 further includes a control means 40 that controls the suction flow rate (suction force) of the first and second bleed gas suction means 22, 32 based on the dust concentration ratio W1/W2 measured by the first and second dust concentration measuring means 25, 35. The control means 40 is composed of a computer having a CPU, a storage device, etc.

The coarse powder P1 separated by the first and second classification means 24, 34 has a relatively low chlorine content and can be returned to the cement kiln system. Therefore, the coarse powder P1 is returned as a cement raw material to a preheater (not shown) attached to the cement kiln. On the other hand, the fine powder P2 collected by the first and second dust collection means 26, 36 contains microcrystals of the chlorine compounds and has a relatively high chlorine content. Therefore, by recovering the fine powder P2, it is possible to bypass chlorine from the extracted gas.

The first and second bleed probes 21, 31 are preferably arranged rotationally symmetrically about the central axis of the end of the kiln 11 at the end of the cement kiln 10. This makes it possible to further prevent the dust present at the end of the kiln 11 from becoming unevenly distributed.

As described above, the chlorine bypass system 100 is equipped with two chlorine bypass systems 20 and 30. Therefore, compared to a system equipped with only one chlorine bypass system, it is possible to suppress the occurrence of uneven distribution of dust in the kiln butt 11 and to reduce the amount of dust extracted by the single chlorine bypass system, thereby reducing the dust concentration of the extracted gas and improving the chlorine bypass efficiency.

However, if the bleed gas flow rate or dust amount in the chlorine bypass systems 20, 30 fluctuates due to the bias of the cement clinker raw material or gas flow in the kiln butt 11, the chlorine bypass efficiency may decrease due to an increase in the amount of bleed dust. For example, if there is only one chlorine bypass system as in the past, the higher the bleed speed, the more the fine powder P2 along with the bleed gas will shift toward the bleed probe, and the dust concentration near the bleed probe will increase, and as a result, the dust concentration in the bleed gas will also increase.

The inventors have therefore newly discovered from the simulation results described below that in order to improve the chlorine bypass efficiency, the ratio W1/W2 of the first dust concentration W1 to the second dust concentration W2 must be within the range of 0.6 (≒1/1.8) ≦ W1/W2 ≦ 1.8.

Therefore, the control means 40 controls the suction flow rate of the first or second bleed gas suction means 22, 32, or the first and second bleed gas suction means 22, 32, so that the dust concentration ratio W1/W2 is within the range of 0.6≦W1/W2≦1.8.

Specifically, for example, if the dust concentration ratio W1/W2 exceeds 1.8, it is determined that dust is concentrated on the chlorine bypass system 20 side, and the suction flow rate of the exhaust fan 33 on the chlorine bypass system 30 side is increased, or the suction flow rate of the exhaust fan 23 on the chlorine bypass system 20 side is decreased, or the suction flow rates of both of these exhaust fans 23, 33 are changed, thereby drawing the dust in the kiln butt 11 toward the chlorine bypass system 30 side, and controlling the dust concentration ratio W1/W2 to be 0.6≦W1/W2≦1.8.

In order to improve the chlorine bypass efficiency, it is most preferable that the dust concentration ratio W1/W2 is 1.0, so it is also preferable that the control means 40 controls the dust concentration ratio W1/W2 to approach 1.0 or to be within an even narrower range, such as 0.7 (≒1/1.4)≦W1/W2≦1.4.

Furthermore, the chlorine bypass efficiency in each chlorine bypass system 20, 30 may be calculated not only from the dust concentration ratio W1/W2 but also from the amount of fine powder P2 recovered and the chlorine concentration, and the suction power of the first and second extraction gas suction means 22, 32 may be controlled by the control means 40 accordingly.

For example, it is preferable to control the suction power of the first and second bleed gas suction means 22, 32 so that the ratios M1/X1 and M2/X2 of the dust amounts X1 and X2 in the chlorine bypass systems 20, 30 calculated from the dust concentrations W1 and W2 and the bleed gas flow rates of the first and second bleed gas suction means 22, 32 to the measured amounts M1 and M2 of the coarse powder P1 recovered by the first and second classification means 24, 34, respectively, are both within the range of 0.8 to 0.95. This makes it possible to maintain good classification performance of the first and second classification means 24, 34 and maintain high chlorine bypass efficiency.

If the raw materials in the kiln end 11 are not unevenly distributed and are evenly extracted from the first and second chlorine bypass systems 20, 30, the gas flow in the kiln end 11 will be uniform. In such a case, the dust concentration ratio W1/W2 will be 1.0, the total amount X (X1+X2) of dust (fine powder P2) will be minimized, and the chlorine bypass efficiency will be maximized. However, in an actual cement kiln, the gas flow in the kiln end 11 is constantly fluctuating due to fluctuations in the amount and type of raw materials input and the solidification state inside the kiln, and it is rare for the flow to be uniform.

Even in such a case, the present invention aims to reduce the dust amount X and improve the chlorine bypass efficiency by controlling the dust concentration ratio W1/W2 to be within the range of 0.6 to 1.8.

The present invention is not limited to the chlorine bypass system 100 specifically described in the above embodiment, and can be modified as appropriate within the scope of the claims.

For example, in the above-described embodiment, a control means 40 is provided that controls the suction power of the first and second bleed gas suction means 22, 32 based on the dust concentration W1/W2 measured by the first and second dust concentration measuring means 25, 35. However, this is not limited to the above, and the suction power of the first and second bleed gas suction means 22, 32 may be adjusted manually by an operator without providing such a control means 40 based on the dust concentration W1/W2 measured by the first and second dust concentration measuring means 25, 35.

In the above embodiment, the case where two chlorine bypass systems 20, 30 are provided has been described. However, this is not limited, and three or more chlorine bypass systems may be provided. In this case, it is preferable, but not limited to, that the bleed probes of each chlorine bypass system are provided at the end 11 of the cement kiln 10 in rotational symmetry with respect to the central axis of the end 11. Then, the dust concentration may be controlled so that the relationship 0.6≦W1/W2≦1.8 is established in all systems.

To confirm the effect of reducing fine particles (extracted dust) P2 in the above-mentioned chlorine bypass system 100, a simulation analysis was performed using Fluent Ver. 19.0 manufactured by ANSYS JAPAN.

The geometric model of the vicinity of the end 11 of the cement kiln 10 created for use in the simulation has first and second bleed probes 21, 31 provided symmetrically at the end 11, as shown in Figure 2. In addition, a first raw material inlet 12 is provided at the end 11 on the side of the first bleed probe 21, and a second raw material inlet 13 is provided at the end 11 on the side of the 21st bleed probe 31.

The feed rates G1, G2 [kg/s] of the cement clinker raw materials fed from the first and second raw material inlets 12, 13, respectively, the extraction rates C1, C2 [%], which are the ratios of the extracted gas to the combustion gas in the kiln end 11 extracted by the first and second chlorine bypass systems 20, 30, respectively, and the speeds S1, S2 [m/s] of the extracted gas extracted to the first and second chlorine bypass systems 20, 30, respectively, are as shown in Table 1.

The total supply amount of the cement clinker raw material from the first and second raw material inlets 12, 13 is assumed to be 330 t/hour. The amount of combustion gas flowing through the kiln end 11 is assumed to be 160,000 ^Nm3 /hour, its temperature is assumed to be 1,050°C, and the total amount of extracted gas from the first and second chlorine bypass systems 20, 30 is assumed to be 160,000 ^Nm3 /hour (extraction rate is 10%).

Comparative example 1 shows a case where the second chlorine bypass system 30 does not exist and there is only one conventional chlorine bypass system. In addition, by making the raw material input amounts G1, G2 from the first and second raw material input ports 12, 13 different, the raw materials in the kiln bottom 11 are biased. Furthermore, the extraction rates C1, C2 and the extracted gas velocities S1, S2 are determined according to the suction flow rates by the first and second gas suction means 26, 36.

Table 2 shows the dust concentrations W1, W2 [%] and their ratio W1/W2 measured by the first and second dust concentration measuring means 25, 35, respectively, and the amounts X1, X2 [kg/s] of fine powder (dust) P2 collected by the first and second dust collecting means 26, 36, and the total amount X (=X1+X2) [kg/s].

As can be seen from Table 2, in Examples 1 to 4 and Comparative Example 2, which have two chlorine bypass systems, the dust amount X is reduced and the chlorine bypass efficiency is improved compared to Comparative Example 1, which has one chlorine bypass system. Note that when the amount of cement clinker raw material is the same, an increase in dust amount X means that the dust contains a large amount of components other than chlorine components, such as cement components, and the removal efficiency is deteriorated.

Furthermore, Example 1, in which the dust concentration ratio W1/W2 is 1.0, had the smallest dust amount X of 2.9 [kg/s], Examples 2 and 4, in which the dust concentration ratio W1/W2 is 1.4, had the next smallest dust amounts X of 3.3 and 3.4 [kg/s], respectively, Example 3, in which the dust concentration ratio W1/W2 is 1.8, had the next smallest dust amount X of 3.5 [kg/s], and Comparative Example 2, in which the dust concentration ratio W1/W2 is 2.4, had a dust amount X of 3.8 [kg/s].

As can be seen, the closer the dust concentration ratio W1/W2 is to 1.0, the smaller the dust amount X and the better the chlorine bypass efficiency. In Comparative Example 2, where the dust concentration ratio W1/W2 is 2.4, the dust amount X is 3.8 [kg/s], and although the dust amount X is reduced compared to Comparative Example 1, where there is one chlorine bypass system, the reduction amount is only 0.2 [kg/s], which is not a reduction rate of more than 10%, and there is not much improvement in the chlorine bypass efficiency.

On the other hand, in Examples 1 to 4, where the dust concentration ratio W1/W2 is 1.8 or less, the dust amount X is a maximum of 3.5 [kg/s], and compared to Comparative Example 1, which has one chlorine bypass system, the dust amount X is 0.5 [kg/s] or more, a reduction of more than 10%, and a significant improvement in the chlorine bypass efficiency was observed.

In Example 1, the raw material input amounts G1, G2 from the first and second raw material inlets 12, 13 are the same, there is no uneven distribution of raw materials in the kiln bottom 11, and the extraction rates C1, C2 and extraction gas velocities S1, S2 from the first and second chlorine bypass systems 20, 30 are the same, and gas is extracted evenly. Thus, Example 1 is an ideal condition, and in reality, such a state is rarely observed.

10... cement kiln, 11... kiln end, 12... first raw material inlet, 13... second raw material inlet, 20... first chlorine bypass system, 21... first bleed probe, 22... first bleed gas suction means, 23... first cooling means, 24... first classification means, 25... first dust concentration measurement means, 26... first dust collection means, 27... first exhaust means, 28... first kiln bleed gas flow path, 29... first cooler, 30... second chlorine bypass system, 31... second bleed probe, 32... second bleed gas suction means, 33... second cooling means, 34... second classification means, 35... second dust concentration measurement means, 36... second dust collection means, 37... second exhaust means, 38: second kiln extraction gas flow path, 39: second cooler, 100: chlorine bypass system, P1: coarse powder, P2: fine powder.

Claims (2)

a first bleed probe and a second bleed probe provided at the bottom of a single cement kiln, through which bleed gas resulting from bleed of a portion of combustion gas from within the cement kiln passes;
a first bleed gas suction means for suctioning bleed gas with the first bleed probe;
a first classification means for separating coarse particles of dust in the bleed gas bled by the first bleed probe;
a first dust concentration measuring means for measuring a dust concentration in the bleed gas introduced into the first classification means;
a first dust collecting means for collecting fine dust particles in the bleed gas after the coarse particles have been separated by the first classifying means;
a second bleed gas suction means for suctioning bleed gas with the second bleed probe;
a second classification means for separating coarse particles of dust in the bleed gas bled by the second bleed probe;
a second dust concentration measuring means for measuring a dust concentration in the bleed gas introduced into the second classification means;
a second dust collecting means for collecting fine dust particles in the bleed gas after the coarse particles have been separated by the second classifying means;
and a control means for controlling the suction flow rate of the bleed gas of at least one of the first bleed gas suction means and the second bleed gas suction means so that a ratio of a first dust concentration measured by the first dust concentration measuring means to a second dust concentration measured by the second dust concentration measuring means is in a range of 0.6 to 1.8. a first bleed probe and a second bleed probe provided at the bottom of a single cement kiln, through which bleed gas resulting from bleed of a portion of combustion gas from within the cement kiln passes;
a first bleed gas suction means for suctioning bleed gas with the first bleed probe;
a first classification means for separating coarse particles of dust in the bleed gas bled by the first bleed probe;
a first dust concentration measuring means for measuring a dust concentration in the bleed gas introduced into the first classification means;
a first dust collecting means for collecting fine dust particles in the bleed gas after the coarse particles have been separated by the first classifying means;
a second bleed gas suction means for suctioning bleed gas with the second bleed probe;
a second classification means for separating coarse particles of dust in the bleed gas bled by the second bleed probe;
a second dust concentration measuring means for measuring a dust concentration in the bleed gas introduced into the second classification means;
and a second dust collecting means for collecting fine dust particles in the bleed gas after the coarse particles are separated by the second classification means,
A method for operating a chlorine bypass system, comprising operating the system so as to adjust the suction flow rate of the bleed gas of at least one of the first bleed gas suction means and the second bleed gas suction means so that a ratio of a first dust concentration measured by the first dust concentration measuring means to a second dust concentration measured by the second dust concentration measuring means is in a range of 0.6 to 1.8.

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