CN114904381A - A kind of cement production system and its gas treatment method - Google Patents

Abstract

The present invention provides a cement production system and a gas treatment method thereof. The cement production system includes sequential gas connected cement decomposition and high temperature denitration unit, raw meal mill, dust removal unit, low temperature denitration unit and wet processing unit. The gas treatment method includes: in each production cycle, according to the operating state of the raw meal mill, the exhaust gas from the cement decomposition and high temperature denitration unit passes through or does not pass through the raw meal mill for heat exchange, passes through the dust removal unit for dedusting, and passes through the low temperature denitrification unit. After the selective catalytic reduction and denitration treatment in the denitration unit, the treated exhaust gas is subjected to wet absorption by the wet treatment unit according to preset rules to obtain recovered slurry; the recovered slurry is reused as a denitration reducing agent to the cement decomposition and high temperature denitration unit or low temperature denitration unit. Extend the life of the low-temperature catalytic catalyst, ensure the denitration efficiency, reduce the escape of ammonia, and effectively reduce the consumption of denitration reducing agents, thereby reducing the cost of denitration.

Description

A kind of cement production system and its gas treatment method

technical field

The invention relates to the technical field of gas treatment, in particular to a cement production system and a gas treatment method thereof.

Background technique

Large amounts of nitrogen oxides (NOx) are produced during high-temperature calcination in cement production, fuel coal combustion, and raw meal decomposition. With increasingly stringent environmental protection requirements, the emission limits for nitrogen oxides (NOx) are getting lower and lower. In order to meet the requirements of emission limits, when denitrifying exhaust gas containing nitrogen oxides, the injection of denitration reducing agents (such as ammonia, urea, melamine and other nitrogen-containing substances) is increasing, which not only causes costs to rise, but also And the problem of ammonia escape is getting more and more serious. Ammonia escape not only pollutes the atmosphere and affects human health, but also increases the consumption of denitration reducing agents and increases costs. Moreover, when the traditional cement kiln conducts exhaust gas denitrification, the denitration catalyst is arranged in the high temperature and high dust section before the raw meal mill, resulting in a very short lifespan of the catalyst, and at the same time, it is easy to be blocked by dust and lead to production stoppage.

SUMMARY OF THE INVENTION

In view of the above problems, the present invention provides a cement production system and a gas treatment method thereof that overcome the above problems or at least partially solve the above problems.

An object of the present invention is to provide a gas treatment method for a cement production system that can effectively reduce the consumption of denitration reducing agent and thereby reduce the cost of denitration.

A further object of the present invention is to reduce the operating cost of the entire system under the premise of ensuring the denitrification effect by reasonably setting the start-up time of the raw meal mill and the wet processing unit in each production cycle.

Yet another further object of the present invention is to improve the stability of the recovered slurry.

Yet another further object of the present invention is to improve the service life of the denitration catalyst.

Yet a further object of the present invention is to reduce the risk of catalyst plugging.

Yet another further object of the present invention is to desulfurize flue gas.

Another object of the present invention is to provide a cement production system capable of realizing the above-mentioned gas treatment method.

In particular, according to an aspect of the embodiments of the present invention, there is provided a gas treatment method for a cement production system, the cement production system comprising a cement decomposition and high temperature denitration unit, a raw meal mill, a dust removal unit, and a low temperature denitration unit connected by sequential gas unit and wet processing unit, the gas processing method comprises:

In each production cycle, according to the operating state of the raw meal mill, the exhaust gas from the cement decomposition and high-temperature denitration unit is made to pass through or not pass through the raw meal mill for heat exchange, and pass through the dust removal unit for dedusting. and after the selective catalytic reduction and denitration treatment is performed by the low-temperature denitration unit, the treated exhaust gas is subjected to wet absorption through the wet treatment unit according to preset rules to obtain a recovered slurry;

The recovered slurry is reused as a denitration reducing agent to the cement decomposition and high temperature denitration unit or the low temperature denitration unit.

Optionally, the operating state of the raw meal mill includes an open state and a closed state; and

In each production cycle, when the operating state of the raw meal mill is the open state, the exhaust gas of the cement decomposition and high temperature denitration unit is passed through the raw meal mill for heat exchange. When the running state of the mill is the closed state, the exhaust gas of the cement decomposition and high temperature denitration unit is not subjected to heat exchange through the raw meal mill.

Optionally, the preset rule includes turning on the wet processing unit regardless of whether the operating state of the raw meal mill is the on state; and

The step of making the treated exhaust gas pass through the wet processing unit for wet absorption to obtain recovered slurry according to a preset rule includes:

Regardless of whether the operating state of the raw meal mill is the open state, the treated exhaust gas is subjected to wet absorption through the wet process unit to obtain the recovered slurry.

Optionally, the preset rule includes closing the wet processing unit when the operation state of the raw meal mill is the open state, and when the operation state of the raw meal mill is the closed state, turning on the wet processing unit; and

The step of making the treated exhaust gas pass through the wet processing unit for wet absorption to obtain recovered slurry according to a preset rule includes:

When the running state of the raw meal mill is the open state, closing the wet processing unit, so that the treated exhaust gas does not pass through the wet processing unit;

When the operating state of the raw meal mill is the closed state, the wet processing unit is turned on, and the treated exhaust gas is subjected to wet absorption through the wet processing unit to obtain the recovered slurry.

Optionally, the low temperature denitrification unit is configured such that when the operating state of the raw meal mill is the open state, the denitration catalyst in the low temperature denitration unit is adsorbed and adsorbed in the selective catalytic reduction denitration treatment. storing ammonia entrained in the exhaust gas and then allowing the ammonia stored in the denitration catalyst to react with nitrogen oxides when the operating state of the green mill is the off state;

Preferably, the destocking catalyst of the low temperature denitration unit is an anti-sulfur catalyst.

Optionally, in each production cycle, the proportion of time when the raw meal mill is in the open state is greater than or equal to 70% and less than 100%;

Preferably, in each production cycle, the proportion of time that the raw meal mill is in the open state is 80%.

Optionally, the substances contained in the recovered slurry include at least ammonium salts, and in terms of the amount of amino groups, the molar amount of the ammonium salts accounts for more than 50% of the total molar amount of all ammonia substances contained in the recovered slurry. .

Optionally, the absorbing liquid used in the wet processing unit includes at least one of the following: water, dilute sulfuric acid and dilute sulfurous acid; and

The ammonium salt includes at least one of the following: ammonium sulfate, ammonium bisulfite, ammonium sulfite, and ammonium bisulfite.

According to another aspect of the embodiments of the present invention, there is also provided a cement production system, comprising a cement decomposition and high temperature denitration unit, a raw meal mill, a dedusting unit, a low temperature denitration unit and a wet process unit connected in sequence gas, wherein the During each production cycle,

The cement decomposition and high temperature denitration unit is configured to decompose the pretreated cement raw meal, and to perform selective non-catalytic reduction and denitration treatment on nitrogen oxides in the gas stream;

The raw meal mill is configured to perform or not to perform heat exchange with the exhaust gas of the cement decomposition and high temperature denitration unit according to its own operating state;

The dedusting unit is configured to dedust the exhaust gas that has undergone the heat exchange or has not undergone the heat exchange;

The low-temperature denitration unit is configured to perform selective catalytic reduction and denitration treatment on the dedusted exhaust gas;

The wet processing unit is configured to perform wet absorption on the exhaust gas after the selective catalytic reduction and denitration treatment according to preset rules to obtain a recovered slurry, and return the recovered slurry as a denitration reducing agent to the Cement decomposition and high temperature denitration unit or said low temperature denitration unit.

Optionally, the operating state of the raw meal mill includes an open state and a closed state; and

The raw meal mill is also configured as:

When the operating state of the raw meal mill is the open state, heat exchange is performed with the exhaust gas, and when the operation state of the raw meal mill is the closed state, heat exchange is not performed with the exhaust gas .

Optionally, the preset rule includes that the wet processing unit is turned on regardless of whether the operating state of the raw meal mill is the on state; and

The wet processing unit is further configured to:

Regardless of whether the operating state of the raw meal mill is the open state, it remains open and wet absorption is performed on the exhaust gas after the selective catalytic reduction and denitration treatment to obtain the recovered slurry.

Optionally, the preset rule includes that when the running state of the raw meal mill is the open state, the wet processing unit is closed, and when the running state of the raw meal mill is the closed state, the wet processing unit is turned on; and

The wet processing unit is further configured to:

When the operating state of the raw meal mill is the open state, the wet processing unit is turned off so as not to wet absorb the exhaust gas;

When the operating state of the raw meal mill is the closed state, the wet processing unit is turned on, and wet absorption is performed on the exhaust gas to obtain the recovered slurry.

Optionally, the low temperature denitration unit is further configured to: when the operating state of the raw meal mill is the open state, the denitration catalyst in the low temperature denitration unit is adsorbed in the selective catalytic reduction denitration treatment And the ammonia carried in the exhaust gas is stored, and then the ammonia stored in the denitration catalyst is allowed to react with nitrogen oxides when the operating state of the raw mill is the closed state.

Optionally, in each production cycle, the proportion of time when the raw meal mill is in the open state is greater than or equal to 70% and less than 100%;

Preferably, in each production cycle, the proportion of time that the raw meal mill is in the open state is 80%.

Optionally, the substances contained in the recovered slurry include at least ammonium salts, and in terms of the amount of amino groups, the molar amount of the ammonium salts accounts for more than 50% of the total molar amount of all ammonia substances contained in the recovered slurry. ;

The absorption liquid used in the wet processing unit is at least one of the following: water, dilute sulfuric acid and dilute sulfurous acid; and

The ammonium salt includes at least one of the following: ammonium sulfate, ammonium bisulfite, ammonium sulfite, and ammonium bisulfite.

In the cement production system and the gas treatment method thereof of the present invention, the low-temperature catalytic denitrification process is arranged after the raw meal mill and the dust removal unit, and the wet process unit is arranged after the low-temperature catalytic denitration process, which is turned on according to preset rules for use in Absorb the escaped sulfur dioxide, sulfur trioxide, sulfate, ammonia and ammonium salts carried in the exhaust gas, and reuse the absorbed waste liquid as a reducing agent for high-temperature SNCR denitration or low-temperature SCR denitration. This prolongs the life of the catalyst in the low-temperature catalytic denitration process, ensures the denitration efficiency, reduces the escape of ammonia, effectively reduces the consumption of the denitration reducing agent, and thus reduces the denitration cost.

Further, in the cement production system and the gas treatment method thereof of the present invention, in each production cycle, the operation state of the raw meal mill includes an open state and a closed state. When the raw meal mill is in the open state, the raw meal in it exchanges heat with the exhaust gas from the cement decomposition and high temperature denitration unit, and the wet processing unit is closed, and the ammonia escape is adsorbed by the low temperature denitration unit. When the raw meal mill is in a closed state, the raw meal in it does not exchange heat with the exhaust gas, the low-temperature denitration unit can fully react with nitrogen oxides at a higher temperature, and the wet processing unit is turned on to The exhaust gas after the low-temperature catalytic denitration process is subjected to wet absorption to obtain a recovered slurry. In this way, by reasonably setting the start-up time of the raw meal mill and the wet processing unit in each production cycle, the operating cost of the entire system can be reduced on the premise of ensuring the denitration effect.

Further, in the cement production system and the gas treatment method thereof of the present invention, the substances contained in the recovered slurry are mainly ammonium salts, and the slurry is more stable, and it is not easy to form secondary ammonia escape.

The above description is only an overview of the technical solutions of the present invention, in order to be able to understand the technical means of the present invention more clearly, it can be implemented according to the content of the description, and in order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand , the following specific embodiments of the present invention are given.

The above and other objects, advantages and features of the present invention will be more apparent to those skilled in the art from the following detailed description of the specific embodiments of the present invention in conjunction with the accompanying drawings.

Description of drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are for the purpose of illustrating preferred embodiments only and are not to be considered limiting of the invention. Also, the same components are denoted by the same reference numerals throughout the drawings. In the attached image:

Fig. 1 shows a schematic structural block diagram of a cement production system according to an embodiment of the present invention;

FIG. 2 shows a schematic flowchart of a gas treatment method for a cement production system according to an embodiment of the present invention;

FIG. 3 shows a schematic flowchart of a gas treatment method of a cement production system according to another embodiment of the present invention.

Detailed ways

Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided so that the present disclosure will be more thoroughly understood, and will fully convey the scope of the present disclosure to those skilled in the art.

In order to solve the above technical problems, the present invention provides a cement production system.

FIG. 1 shows a schematic structural block diagram of a cement production system 100 according to an embodiment of the present invention. Referring to FIG. 1 , the cement production system 100 may include at least a cement decomposition and high temperature denitration unit 110 , a raw meal mill 120 , a dust removal unit 130 , a low temperature denitration unit 140 and a wet processing unit 150 which are sequentially gas-connected. The sequential gas connection mentioned here can be understood as the connection of the gas outlet of each preceding unit to the gas inlet of the adjacent succeeding unit. It should be noted that the solid line with arrows in FIG. 1 represents the gas passage, and the dashed line with arrows represents the return of the substance as the denitration reducing agent from the wet processing unit 150 to the cement decomposition and high temperature denitration unit 110 or the low temperature denitration unit 140. With the transport channel, the dashed-dotted line with arrows represents the raw meal transport channel from the raw meal mill 120 to the cement decomposition and high temperature denitration unit 110 .

In each production cycle, the cement decomposition and high temperature denitration unit 110 is configured to decompose the pretreated cement raw meal, and to perform Selective Non-Catalytic Reduction (SNCR for short) on nitrogen oxides in the gas stream ) denitrification treatment. Specifically, reducing agents such as ammonia, urea, melamine and other nitrogen-containing substances are sprayed in the SNCR denitration treatment. The specific operations of the decomposition of the cement raw meal and the corresponding SNCR denitration treatment should be known to those skilled in the art, and will not be described in detail herein.

The raw meal mill 120 is configured to perform or not to perform heat exchange with the exhaust gas of the cement decomposition and high temperature denitration unit 110 according to its own operating state. Specifically, in the raw meal mill 120, the exhaust gas may be passed through a preheater to preheat the raw meal. Of course, heat exchange between the exhaust gas and the raw meal can also be performed in other ways, which is not limited in the present invention. The raw meal processed in the raw meal mill 120 is transported to the cement decomposition and high temperature denitration unit 110 through the raw meal transmission channel.

The dedusting unit 130 is configured to dedust the exhaust gas that has undergone heat exchange or has not undergone heat exchange. Specifically, the dust removal unit 130 may use a bag filter or the like.

The low temperature denitration unit 140 is configured to perform selective catalytic reduction (Selective Catalytic Reduction, SCR for short) denitration treatment on the dedusted exhaust gas. Specifically, a low-temperature denitration catalyst can be set in the low-temperature denitration unit 140, and by spraying a reducing agent, at a temperature of 120°C to 200°C, preferably a temperature of 120°C to 180°C, such as 130°C, 140°C, 150°C, 160°C , 170 ℃ temperature, the selective catalytic reduction reaction. The low-temperature denitration catalyst can be a low-temperature denitration catalyst currently available on the market, and of course other low-temperature denitration catalysts can also be used, preferably a catalyst with sulfur resistance, which is not limited in the present invention.

The wet processing unit 150 is configured to wet-absorb the exhaust gas after selective catalytic reduction and denitrification to obtain recovered slurry according to preset rules, and return the recovered slurry to the cement decomposition and high temperature denitration unit 110 as a denitration reducing agent. Specifically, in the wet processing unit 150, the exhaust gas is contacted with the absorption liquid for wet absorption, so that the escaped sulfur dioxide, sulfur trioxide, sulfate, ammonia and ammonium salts, etc. carried in the exhaust gas are absorbed by the absorption liquid. The absorption liquid can include water, or an acidic solution (such as dilute sulfuric acid, dilute sulfurous acid, etc.) can be used to improve the absorption effect of ammonia and ammonium salts and other ammonia substances. The obtained recovered slurry is transported to the cement decomposition and high temperature denitration unit 110 or the low temperature denitration unit 140 through the reuse transmission channel.

Since the recovered slurry is rich in ammonia-based reducing substances, in some embodiments, the recovered slurry can be directly sprayed into the cement decomposition and high-temperature denitration unit 110 (eg, a decomposition furnace and its adjacent sections) to achieve SNCR denitration. In other alternative embodiments, alkaline substances (such as sodium bicarbonate, etc.) can also be added to the recovered slurry to react with ammonium salts to generate ammonia gas, and then the ammonia gas is sprayed into the cement for decomposition and high-temperature denitration. Unit 110, realizes SNCR denitration. When the recovered slurry is reused to the low temperature denitration unit 140, the method is similar to that of the cement decomposition and high temperature denitration unit 110, and will not be repeated here.

In the cement production system 100 of the embodiment of the present invention, the low-temperature denitrification unit 140 is arranged after the raw meal mill 120 and the dust removal unit 130, and the wet processing unit 150 is arranged after the low-temperature denitration unit 140. The wet processing unit 150 is preset according to the The rules are turned on to absorb the escaped sulfur dioxide, sulfur trioxide, sulfate, ammonia and ammonium salts carried in the exhaust gas, which prolongs the life of the catalyst in the low-temperature catalytic denitrification process, ensures the denitration efficiency, and reduces the escape of ammonia. . In addition, the wet processing unit 150 also reuses the recovered slurry obtained by absorption as a denitration reducing agent to the high temperature denitration or low temperature denitration process of cement production, which effectively reduces the consumption of the denitration reducing agent and reduces the denitration cost.

In some embodiments, the substance contained in the recovered slurry includes at least ammonium salt, and the molar amount of the ammonium salt accounts for more than 50% of the total molar amount of all ammonia substances contained in the recovered slurry based on the amount of amino groups. In other words, the substances contained in the obtained recovered slurry are mainly ammonium salts, the slurry is more stable, and it is not easy to form secondary ammonia escape. In contrast, in the solution of directly absorbing ammonia gas in the prior art, the formed ammonia water is relatively unstable, and it is easy to form secondary ammonia escape.

In some further embodiments, in order to convert ammonia into ammonium salts as much as possible, the absorption liquid used in the wet processing unit 150 may include dilute sulfuric acid, dilute sulfurous acid, and the like. The ammonium salt may specifically include at least one of ammonium sulfate, ammonium hydrogen sulfate, ammonium sulfite, and ammonium hydrogen sulfite, depending on the components of the absorption liquid used.

In some embodiments, in each production cycle, the operating state of the green mill 120 includes an on state and an off state. When the operation state of the raw meal mill 120 is in the open state, heat exchange is performed with the exhaust gas, and when the operation state of the raw meal mill 120 is in the closed state, heat exchange with the exhaust gas is not performed.

In general, when the raw meal mill 120 is in the open state, due to the heat exchange between the exhaust gas and the raw meal, the temperature when it reaches the low-temperature denitration unit 140 is relatively low, and the denitration efficiency of the low-temperature denitration catalyst will be relatively low. When the material mill 120 is in a closed state, since the exhaust gas does not need to exchange heat with the raw meal, and its temperature is high, the denitration efficiency of the low-temperature denitration catalyst will be higher, which will affect the denitration of the entire system.

Considering the above situation, preset rules for the wet processing unit 150 may be set accordingly to achieve desired effects.

In some embodiments, the preset rule includes that the wet processing unit 150 is turned on regardless of whether the operating state of the raw meal mill 120 is the ON state, that is, whether the raw meal mill 120 is in the ON state or the OFF state, the wet process unit 150 is turned ON. Cells 150 remain on. Correspondingly, the wet processing unit 150 is further configured to remain on regardless of whether the raw mill 120 is in an on state or not, and perform wet absorption on the exhaust gas after selective catalytic reduction and denitrification to obtain recovered slurry. In this way, the absorption of fugitive ammonia can be ensured to the greatest extent on the basis of appropriately increasing the operating cost of the system.

In other embodiments, the preset rules include that when the operating state of the raw meal mill 120 is in the on state, the wet processing unit 150 is turned off, and when the operating state of the raw meal mill 120 is in the off state, the wet processing unit 150 is turned on. . Correspondingly, the wet processing unit 150 is further configured to: when the operating state of the raw meal mill 120 is on, the wet processing unit 150 is turned off so as not to perform wet absorption of the exhaust gas; when the operating state of the raw meal mill 120 is off In the state, the wet processing unit 150 is turned on, and the exhaust gas is subjected to wet absorption to obtain a recovered slurry. In this way, the wet processing unit 150 can be selectively turned on. By reasonably setting the turn-on time of the raw meal mill 120 and the wet processing unit 150 in each production cycle, the operation of the entire system can be reduced on the premise of ensuring the denitration effect. cost.

Further, the low temperature denitration unit 140 is also configured to adsorb and store the ammonia carried in the exhaust gas by the denitration catalyst in the low temperature denitration unit 140 in the selective catalytic reduction denitrification process when the operating state of the raw meal mill 120 is in the open state, And then when the operating state of the raw meal mill is the off state, the ammonia stored in the denitration catalyst is allowed to react with nitrogen oxides.

In other words, when the raw meal mill 120 is in the open state, the temperature of the exhaust gas is relatively low, and the denitration efficiency of the low-temperature denitration catalyst is relatively low. At this time, denitration is completed by the cement decomposition and high temperature denitration unit 110, and after the remaining ammonia escapes, it is adsorbed/absorbed by the low temperature denitration catalyst in the low temperature denitration unit 140, and can be stored in a large amount. In this way, the wet processing unit 150 does not have to be activated, but the ammonia slip can be controlled through low temperature denitration catalyst adsorption/absorption.

When the raw meal mill 120 is in a closed state (ie, the mill is stopped), the temperature of the exhaust gas is relatively high, and the denitration effect of the low-temperature denitration catalyst is relatively high. internal reaction. Specifically, on the one hand, the catalyst provides an oxidative environment to oxidize sulfur dioxide to sulfite or sulfate, and on the other hand provides a reaction platform, so that part of the sulfur dioxide reacts with ammonia to form ammonium salts. The rear wet processing unit 150 is turned on, and the escaped ammonium salt, ammonia, sulfur dioxide, etc. can be absorbed and reused to the cement decomposition and high temperature denitration unit 110 .

In this way, the ammonia absorbed when the raw mill 120 is started is stored in the low-temperature denitration catalyst, and the denitration reaction is performed when the mill is stopped, so it will not be wasted. In addition, when the grinding is stopped, the sulfur (such as sulfur dioxide, sulfur trioxide, etc.) in the exhaust gas of the cement kiln system (such as the calciner) will exceed the standard. It is necessary to increase the amount of ammonia injection to achieve desulfurization, resulting in high ammonia consumption. big. By adding the low-temperature denitration unit 140, the low-temperature denitration catalyst can effectively cause ammonia and sulfur to react to form ammonium salt, which is carried out by the exhaust gas, thereby reducing the amount of ammonia injection. Moreover, since the ammonium salt is generated, it can also be formed into a relatively stable recovered slurry after the latter wet processing unit 150 captures it.

In some embodiments, in each production cycle, the proportion of time that the green mill 120 is in the on state may be greater than or equal to 70% and less than 100%, for example, may be 75%, 80%, 85%, 90% , 95%, etc. Preferably, in each production cycle, the proportion of time that the raw meal mill 120 is in an on state may be 80%. By reasonably setting the proportion of time that the raw meal mill 120 is in an open state in each production cycle, it is possible to ensure a better overall operating efficiency of the cement production system 100, including waste heat utilization efficiency, denitrification efficiency, and reducing agent reuse efficiency, etc. .

Based on the same technical concept, the present invention also provides a gas treatment method for the cement production system 100 . The structure of the cement production system 100 can be shown in FIG. 1 . FIG. 2 shows a schematic flowchart of a gas treatment method of the cement production system 100 according to an embodiment of the present invention. Referring to Fig. 2, the gas treatment method of the cement production system 100 may at least include the following steps S202 to S204.

Step S202, in each production cycle, according to the operating state of the raw meal mill 120, the exhaust gas of the cement decomposition and high temperature denitration unit 110 is sequentially passed through or not passed through the raw meal mill 120 for heat exchange, through the dust removal unit 130 for dedusting and denitrification. After the selective catalytic reduction and denitration treatment by the low-temperature denitration unit 140, the treated exhaust gas is subjected to wet absorption through the wet treatment unit 150 according to preset rules to obtain a recovered slurry.

Step S204, the recovered slurry is reused as a denitration reducing agent to the cement decomposition and high temperature denitration unit 110 or the low temperature denitration unit 140.

Since the recovered slurry is rich in ammonia-based reducing substances, in some embodiments, the recovered slurry can be directly sprayed into the cement decomposition and high-temperature denitration unit 110 (eg, a decomposition furnace and its adjacent sections) to achieve SNCR denitration. In other alternative embodiments, alkaline substances (such as sodium bicarbonate, etc.) can also be added to the recovered slurry to react with ammonium salts to generate ammonia gas, and then the ammonia gas is sprayed into the cement for decomposition and high-temperature denitration. Unit 110, realizes SNCR denitration. When the recovered slurry is reused to the low temperature denitration unit 140, the method is similar to that of the cement decomposition and high temperature denitration unit 110, and will not be repeated here.

In some embodiments, the operating state of the raw meal mill 120 includes an on state and an off state; and, in each production cycle, when the operating state of the raw meal mill 120 is an on state, the cement decomposition and high temperature denitration unit 110 is made The exhaust gas of the raw material mill 120 conducts heat exchange through the raw meal mill 120. When the operating state of the raw meal mill 120 is in the off state, the exhaust gas of the cement decomposition and high temperature denitration unit 110 does not pass through the raw meal mill 120 for heat exchange.

In some embodiments, the preset rule includes turning on the wet processing unit 150 regardless of whether the operating state of the green mill 120 is on. Correspondingly, the step of making the treated exhaust gas pass through the wet processing unit 150 for wet absorption to obtain the recovered slurry according to a preset rule includes: no matter whether the operation state of the raw meal mill 120 is in the open state, the treated exhaust gas is allowed to pass through the wet process unit 150. The wet processing unit 150 performs wet absorption to obtain recovered slurry.

In other embodiments, the preset rules include that when the operating state of the raw meal mill 120 is in the open state, the wet processing unit 150 is turned off, and when the operating state of the raw meal mill 120 is in the off state, the wet processing unit 150 is turned on. . Correspondingly, the step of making the treated exhaust gas pass through the wet processing unit 150 for wet absorption to obtain the recovered slurry according to the preset rules includes: when the operating state of the raw mill 120 is in the open state, closing the wet processing unit 150, The treated exhaust gas does not pass through the wet processing unit 150; when the operating state of the raw meal mill 120 is off, the wet processing unit 150 is turned on, and the treated exhaust gas passes through the wet processing unit 150 for wet processing. Absorption to obtain recovered slurry.

In some further embodiments, the low temperature denitration unit 140 is also configured such that when the operating state of the raw meal mill 120 is an on state, the denitration catalyst in the low temperature denitration unit 140 is adsorbed and stored for discharge in the selective catalytic reduction denitration process The ammonia entrained in the gas, and then when the operating state of the raw mill is off, allows the ammonia stored in the denitration catalyst to react with nitrogen oxides.

In some embodiments, the green mill 120 is in the on state for greater than or equal to 70% and less than 100% of the time in each production cycle.

Preferably, in each production cycle, the raw meal mill 120 is in an open state for 80% of the time.

In some embodiments, the substance contained in the recovered slurry includes at least ammonium salt, and the molar amount of the ammonium salt accounts for more than 50% of the total molar amount of all ammonia substances contained in the recovered slurry based on the amount of amino groups. In other words, the substances contained in the obtained recovered slurry were mainly ammonium salts.

In some further embodiments, in order to convert ammonia into ammonium salts as much as possible, the absorption liquid used in the wet processing unit 150 may include dilute sulfurous acid, etc. The ammonium salt may specifically include at least one of ammonium sulfate, ammonium hydrogen sulfate, ammonium sulfite, and ammonium hydrogen sulfite, depending on the components of the absorption liquid used.

Various embodiments of each link of the gas treatment method of the cement production system 100 of the present invention have been introduced above, and the specific implementation of the gas treatment method of the cement production system 100 of the present invention will be described in more detail below through a specific example. Way.

FIG. 3 shows a schematic flowchart of a gas treatment method of the cement production system 100 according to another embodiment of the present invention. In this embodiment, in each production cycle, the time when the raw meal mill 120 is in an on state accounts for 80%. Referring to FIG. 3 , the gas treatment method of the cement production system 100 includes the following steps S302 to S316.

In step S302, it is determined whether the running state of the raw meal mill 120 is an open state or a closed state.

Step S304 , if the running state of the raw meal mill 120 is in the ON state, the exhaust gas of the cement decomposition and high temperature denitration unit 110 is allowed to pass through the raw meal mill 120 for heat exchange. After that, steps S308 to S310 are performed.

Step S306 , if the running state of the raw meal mill 120 is in the off state, the exhaust gas of the cement decomposition and high temperature denitration unit 110 is not subjected to heat exchange through the raw meal mill 120 . After that, steps S312 to S316 are performed.

In step S308, the exhaust gas is dedusted through the dedusting unit 130.

In step S310, the exhaust gas after dedusting is passed through the low-temperature denitration unit 140 for selective catalytic reduction and denitration treatment.

Specifically, when the operating state of the raw meal mill 120 is the ON state, the denitration catalyst in the low temperature denitration unit 140 adsorbs/absorbs the ammonia carried in the exhaust gas in the selective catalytic reduction denitration process, so as to store the ammonia in the low temperature denitration catalyst Inside.

In addition, at this time, the wet processing unit 150 is turned off, and the exhaust gas after the selective catalytic reduction and denitration treatment does not pass through the wet processing unit 150 .

In step S312, the exhaust gas is dedusted through the dedusting unit 130.

In step S314, the exhaust gas after dedusting is passed through the low-temperature denitration unit 140 for selective catalytic reduction and denitration treatment.

Specifically, when the raw meal mill 120 is in a closed state, the ammonia previously stored in the low-temperature denitration catalyst in the low-temperature state can react in the catalyst. On the one hand, the catalyst provides an oxidizing environment to oxidize sulfur dioxide to sulfite or sulfate, and on the other hand provides a reaction platform, so that part of the sulfur dioxide reacts with ammonia to form ammonium salts.

In step S316, the wet processing unit 150 is turned on, and the treated exhaust gas is subjected to wet absorption through the wet processing unit 150 to obtain recovered slurry.

Specifically, the absorbing liquid used in the wet processing unit 150 includes dilute sulfuric acid. In terms of the amount of amino groups, the molar quantity of the ammonium salt in the recovered slurry accounts for more than 50% of the total molar quantity of all ammonia substances contained in the recovered slurry. Ammonium salts include ammonium sulfate and/or ammonium hydrogen sulfate.

In this embodiment, during the operation of the cement production system 100, the recovered slurry obtained in step S316 is returned to the cement decomposition and high temperature denitration unit 110 as a reducing agent for SNCR denitration.

In the description provided herein, numerous specific details are set forth. It will be understood, however, that embodiments of the invention may be practiced without these specific details. In some instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.

By now, those skilled in the art will recognize that, although various exemplary embodiments of the present invention have been illustrated and described in detail herein, the present invention may still be implemented in accordance with the present disclosure without departing from the spirit and scope of the present invention. The content directly determines or derives many other variations or modifications consistent with the principles of the invention. Accordingly, the scope of the present invention should be understood and deemed to cover all such other variations or modifications.

Claims (15)

1. A gas treatment method of a cement production system, characterized in that the cement production system comprises a cement decomposition and high temperature denitration unit, a raw meal mill, a dust removal unit, a low temperature denitration unit and a wet treatment unit which are sequentially connected by gas, the gas treatment method comprises:

in each production period, according to the running state of the raw meal mill, enabling the exhaust gas of the cement decomposition and high-temperature denitration unit to sequentially pass through or not pass through the raw meal mill for heat exchange, pass through the dust removal unit for dust removal and pass through the low-temperature denitration unit for selective catalytic reduction denitration treatment, and then enabling the treated exhaust gas to pass through the wet treatment unit for wet absorption according to preset rules to obtain recovered slurry;

and recycling the recovered slurry as a denitration reducing agent to the cement decomposition and high-temperature denitration unit or the low-temperature denitration unit.

2. The gas treatment method according to claim 1,

the running state of the raw material mill comprises an opening state and a closing state; and is

In each production cycle, when the operation state of the raw mill is the open state, the exhaust gas of the cement decomposition and high-temperature denitration unit is subjected to heat exchange through the raw mill, and when the operation state of the raw mill is the closed state, the exhaust gas of the cement decomposition and high-temperature denitration unit is not subjected to heat exchange through the raw mill.

3. The gas treatment method according to claim 2,

the preset rule comprises that the wet processing unit is started no matter whether the running state of the raw material mill is the starting state or not; and is

The step of performing wet absorption on the treated exhaust gas through the wet treatment unit according to a preset rule to obtain recovered slurry comprises the following steps:

and performing wet absorption on the treated exhaust gas through the wet treatment unit to obtain the recovered slurry no matter whether the running state of the raw material mill is the starting state or not.

4. The gas treatment method according to claim 2,

the preset rule comprises turning off the wet processing unit when the operation state of the raw material mill is the on state, and turning on the wet processing unit when the operation state of the raw material mill is the off state; and is

The step of performing wet absorption on the treated exhaust gas through the wet treatment unit according to a preset rule to obtain recovered slurry comprises the following steps:

when the running state of the raw material mill is the starting state, closing the wet processing unit to ensure that the treated exhaust gas does not pass through the wet processing unit;

and when the running state of the raw material mill is the closing state, starting the wet processing unit, and enabling the treated exhaust gas to be subjected to wet absorption by the wet processing unit to obtain the recovered slurry.

5. The gas treatment method according to claim 4,

configuring the low-temperature denitration unit such that a denitration catalyst in the low-temperature denitration unit adsorbs and stores ammonia carried in the exhaust gas in the selective catalytic reduction denitration treatment when the operation state of the raw mill is the on-state, and then allows the ammonia stored in the denitration catalyst to react with nitrogen oxides when the operation state of the raw mill is the off-state;

preferably, the denitration catalyst of the low-temperature denitration unit is a sulfur-resistant catalyst.

6. The gas treatment method according to any one of claims 2 to 5,

in each production cycle, the time of the raw material mill in the starting state accounts for more than or equal to 70% and less than 100%;

preferably, the raw meal mill is in the on state for 80% of the time in each production cycle.

7. The gas treatment method according to claim 1,

the substance contained in the recovery slurry includes at least an ammonium salt, and the molar amount of the ammonium salt is more than 50% of the total molar amount of all the ammonia-type substances contained in the recovery slurry based on the amount of the amino groups.

8. The gas treatment method according to claim 7, wherein the absorption liquid used in the wet treatment unit comprises at least one of: water, dilute sulfuric acid and dilute sulfurous acid; and is provided with

The ammonium salt comprises at least one of: ammonium sulfate, ammonium bisulfate, ammonium sulfite, and ammonium bisulfite.

9. A cement production system is characterized by comprising a cement decomposition and high-temperature denitration unit, a raw meal mill, a dust removal unit, a low-temperature denitration unit and a wet treatment unit which are sequentially in gas connection, wherein in each production period,

the cement decomposition and high-temperature denitration unit is configured to decompose the pretreated cement raw material and perform selective non-catalytic reduction denitration treatment on nitrogen oxides in airflow;

the raw mill is configured to perform or not perform heat exchange with the exhaust gas of the cement decomposition and high-temperature denitration unit according to the running state of the raw mill;

the dust removal unit is configured to remove dust from the exhaust gas that has undergone the heat exchange or has not undergone the heat exchange;

the low-temperature denitration unit is configured to perform selective catalytic reduction denitration treatment on the exhaust gas after dust removal;

the wet processing unit is configured to perform wet absorption on the exhaust gas subjected to the selective catalytic reduction denitration treatment according to a preset rule to obtain recovered slurry, and return the recovered slurry as a denitration reducing agent to the cement decomposition and high-temperature denitration unit or the low-temperature denitration unit.

10. The cement production system according to claim 9,

the running state of the raw material mill comprises an opening state and a closing state; and is

The raw mill is further configured to:

and when the operation state of the raw meal mill is the opening state, the heat exchange is carried out with the exhaust gas, and when the operation state of the raw meal mill is the closing state, the heat exchange is not carried out with the exhaust gas.

11. The cement production system according to claim 10,

the preset rule comprises that the wet processing unit is started whether the running state of the raw material mill is the starting state or not; and is

The wet processing unit is further configured to:

and (3) keeping the raw material mill started no matter whether the running state of the raw material mill is the starting state or not, and performing wet absorption on the exhaust gas subjected to the selective catalytic reduction denitration treatment to obtain the recovered slurry.

12. The cement production system according to claim 10,

the preset rule comprises that when the running state of the raw material mill is the starting state, the wet processing unit is closed, and when the running state of the raw material mill is the closing state, the wet processing unit is opened; and is

The wet processing unit is further configured to:

when the operation state of the raw mill is the on state, the wet processing unit is turned off so as not to perform wet absorption on the exhaust gas;

and when the running state of the raw material mill is the closing state, the wet processing unit is started, and the discharged gas is subjected to wet absorption to obtain the recovered slurry.

13. Cement production system according to claim 12,

the low temperature denitration unit is further configured to: the denitration catalyst in the low-temperature denitration unit adsorbs and stores ammonia carried in the exhaust gas in the selective catalytic reduction denitration treatment when the operation state of the raw mill is the on state, and then allows the ammonia stored in the denitration catalyst to react with nitrogen oxides when the operation state of the raw mill is the off state.

14. Cement production system according to any one of claims 10 to 13,

in each production cycle, the time of the raw material mill in the starting state accounts for more than or equal to 70% and less than 100%;

preferably, the raw meal mill is in the on state for 80% of the time in each production cycle.

15. The cement production system according to claim 9,

the substances contained in the recovery slurry at least comprise ammonium salt, and the molar quantity of the ammonium salt accounts for more than 50% of the total molar quantity of all the ammonia substances contained in the recovery slurry based on the amount of the amino groups;

the absorption liquid used in the wet treatment unit comprises at least one of: water, dilute sulfuric acid and dilute sulfurous acid; and is

The ammonium salt comprises at least one of: ammonium sulfate, ammonium bisulfate, ammonium sulfite, and ammonium bisulfite.

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