Bypass ventilation system

Abstract

The bypass ventilation system comprises an air taking opening formed in a smoke chamber, a quench cooler, a cyclone dust collector, a bag dust collector, an ash bin and a pneumatic conveying device. The quench cooler adopts a volute structure, and an air inlet port of the quench cooler is connected with a quench fan; high-temperature flue gas passing through the quench cooler enters the cyclone dust collector, coarse particles in the flue gas are returned to the decomposing furnace by the cyclone dust collector, and relatively coarse particles are returned to the kiln tail, so that partial material consumption and heat consumption are reduced; fine particle dust separated by the cyclone dust collector enters a cloth bag dust collector to be collected, and clean air is directly discharged into a kiln tail chimney through an exhaust fan; ash collected in the cloth bag dust collector is firstly conveyed into the ash bin, and then the ash is conveyed to the steel bin at the clinker conveying belt or conveyed to the ash temporary storage bin of the water washing workshop and then is subjected to water washing. According to the bypass ventilation system, the skinning problem can be effectively relieved, and stable operation of a production line is guaranteed; and the quality of the cement is ensured.

Description

Technical Field

[0001] The invention relates to the technical field of cement production, and in particular to a bypass ventilation system. Background Art

[0002] The so-called bypass ventilation refers to the discharge of part of the high-temperature flue gas in the kiln tail smoke chamber to the outside of the system for separate treatment; the bypass ventilation ratio refers to the proportion of the high-temperature flue gas discharged to the outside to the total amount of flue gas in the kiln tail smoke chamber.

[0003] At present, whether the bypass ventilation of cement needs to be set up and the determination of the bypass ventilation volume mainly depends on the content of harmful elements in raw materials and fuels (including alternative raw materials and alternative fuels) and their volatility, as well as the amount allowed to remain in the target clinker product. The influence of harmful elements is mainly reflected in two aspects. One is that it affects the stable operation and control of the system, and the other is that it remains in the cement clinker and affects the quality of cement products. Since the compound 6 formed by K2O, Na2O, C1, and SO3 in the raw fuel has a gas-solid state conversion process between 780℃ and 1000℃, within this temperature range, a certain amount of ventilation treatment can break the cyclic enrichment problem of the corresponding interfering elements and discharge part of C1, K2O, and Na2O out of the system.

[0004] After the Cl ion of the hot raw material in the C5 discharge pipe increases (for example, reaching 1.33%), the volatilization rate of chloride ions in the firing system will further increase (for example, the volatilization rate is 97.14%); the sulfur and alkali content of the clinker is high, and there is a risk of crusting of potassium sodium sulfate and anhydrous gypsum in the preheater. When a large amount of chlorine is introduced into the system, the eutectic temperature window of these sulfate complexes will decrease from 800°C to 700°C, which will easily cause crusting in the upper preheater; subsequently, if the amount of alternative fuel is continued to increase, the crusting frequency of the firing system will definitely increase without a significant reduction in clinker production. Therefore, it is necessary to have a bypass ventilation system to reduce the Cl ion concentration of the clinker. Summary of the invention

[0005] To this end, the present invention provides a bypass ventilation system to solve the problem of how to reduce the chloride ion concentration of clinker in the prior art.

[0006] In order to achieve the above object, the present invention provides the following technical solutions: A bypass venting system comprises an air intake opening in a smoke chamber, a quencher connected to the air intake opening, a cyclone dust collector, a bag dust collector, an ash bin and a pneumatic conveying device; the quencher adopts a volute structure, and the air inlet port of the quencher is connected to a rapid cooling fan; the high-temperature flue gas after passing through the quencher enters the cyclone dust collector, and the cyclone dust collector returns the coarse particles in the flue gas to the decomposition furnace, and the coarser particles return to the tail of the kiln, thereby reducing part of the material consumption and heat consumption; the fine particle dust separated by the cyclone dust collector enters the bag dust collector to be collected, and the clean air is directly discharged into the chimney at the tail of the kiln through the exhaust fan; the ash collected in the bag dust collector is first transported to the ash bin, and then the ash is transported to the steel bin at the clinker conveying belt or to the ash buffer bin in the washing workshop by dense phase conveying for water washing.

[0007] Furthermore: a secondary cooling system is provided in front of the inlet of the bag dust collector, and the secondary cooling system can further cool the hot flue gas passing through the quench cooler and the cyclone dust collector to a temperature range that the bag dust collector can withstand; the secondary cooling system adopts a waste heat recovery system or directly sets a cold air valve on the pipeline.

[0008] Furthermore: the air intake is arranged on one side of the upper part of the smoke chamber at the tail of the kiln close to the rotary kiln, and the position of the air intake has the least effect on the wind speed of the smoke chamber shrinkage.

[0009] Furthermore: the bypass ventilation ratio is 5%-10%.

[0010] Further: the waste heat recovery system includes an evaporator. After entering the evaporator, the high-temperature flue gas is heat-exchanged and then the temperature is reduced again. The flue gas with reduced temperature passes through the economizer and then enters the bag filter.

[0011] Furthermore: the water washing workshop is provided with a water washing and dehydration system, which dissolves the soluble ions in the bypass ash in water as much as possible, and the insoluble filter cake is centrifugally dehydrated and then washed several times, and finally the chloride ion concentration in the filter cake is reduced to below 1%.

[0012] Furthermore: the ash in the ash bin is discharged into the buffer ash bin and enters the dissolution stirring tank with clean water. The dissolved ash-containing slurry is discharged into the centrifugal buffer tank for subsequent centrifugal separation. The filter cake obtained by centrifugation is washed with clean water, and the mother liquor obtained by centrifugation enters the mother liquor buffer tank and then enters the mother liquor purification system. The elution is repeated to ensure that the chlorine content in the filter cake meets the standard.

[0013] Furthermore: a double air duct is arranged inside the quencher, and the cold air cut into the volute mixing chamber by the quencher enters the mixing chamber in two directions and wraps the high-temperature flue gas, and the wind speed at the outlet of the two-way air duct is the same.

[0014] Furthermore: the diameter of the pipe at the upper end of the quencher smoke outlet is greater than the diameter of the pipe at the lower end of the smoke inlet.

[0015] The bypass venting system of the present invention can effectively alleviate the crusting problem caused by high levels of raw materials, fuel alkali, chlorine and sulfur, ensure the smooth operation of the production line, and ensure the quality of cement. The volute-type quencher is used, and the cold air is mixed with the high-temperature flue gas in a cut-in manner, which can quickly wrap the high-temperature flue gas, eliminate the possibility of high-temperature flue gas adhering to the wall in the mixing chamber, and reduce the possibility of blockage of the quencher.

[0016] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practicing the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more intuitively illustrate the prior art and the present application, exemplary drawings are given below. It should be understood that the specific shapes and structures shown in the drawings should not generally be regarded as limiting conditions for implementing the present application; for example, those skilled in the art are capable of easily making conventional adjustments or further optimizations to the addition / reduction / attribution division, specific shapes, positional relationships, connection methods, dimensional ratios, etc. of certain units (components) based on the technical concepts and exemplary drawings disclosed in the present application.

[0018] Figure 1 A flow chart of a bypass venting system provided for one embodiment of the present application.

[0019] Figure 2 It is a temperature distribution cloud diagram of the main section of the quencher in the embodiment of the present invention.

[0020] Figure 3 It is a temperature distribution cloud diagram of the cross section of the quencher volute in the embodiment of the present invention.

[0021] Figure 4 This is a structural schematic diagram of the effects of different bypass ventilation ratios on various parameters when the chlorine content in the alternative fuel is 1.6% in an embodiment of the present invention.

[0022] Figure 5 This is a structural schematic diagram of the effects of different bypass ventilation ratios on various parameters when the chlorine content in the alternative fuel is 2.5% in an embodiment of the present invention.

[0023] Figure 6 Schematic diagram of calculation results of cold air mixing amount of quench cooler in an embodiment of the present invention.

[0024] Figure 7 4 is a system block diagram of a waste heat recovery system in an embodiment of the present invention.

[0025] Figure 8A schematic diagram of the internal structure of a quencher volute provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0026] The following is an explanation of the implementation of the present invention by specific specific examples. People familiar with this technology can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Obviously, the described embodiments are part of the embodiments of the present invention, not all of them. It should be understood that these embodiments are only to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Technical engineers in this field can make some non-essential improvements and adjustments to the present invention based on the contents of the above invention; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] See also Figure 1 , a bypass ventilation system, including an air intake opened in the smoke chamber, a quench cooler connected to the air intake, a cyclone dust collector, a bag dust collector, an ash bin and a pneumatic conveying device. The quench cooler adopts a volute structure, and its air inlet port is connected to a quench fan. The quench fan blows cold air into the quench cooler to mix with the high-temperature flue gas, so that the cold air wraps the high-temperature flue gas; the high-temperature flue gas after passing through the quench cooler enters the cyclone dust collector, and the cyclone dust collector returns the coarse particles in the flue gas to the decomposition furnace, and the coarser particles return to the kiln tail, thereby reducing part of the material consumption and heat consumption; the fine particle dust separated by the cyclone dust collector enters the bag dust collector to be collected, and the clean air is directly discharged into the chimney at the kiln tail through the exhaust fan.

[0028] The ash collected in the bag dust collector is first transported to the ash bin, and then the dense phase conveying method is adopted, that is, the existing pneumatic conveying device is used to transport the ash to the steel bin at the clinker conveying belt or to the ash buffer bin for water washing.

[0029] Before the hot flue gas downstream of the cyclone dust collector enters the inlet of the bag dust collector, a secondary cooling system is provided. The secondary cooling system can further cool the hot flue gas that has passed through the quench cooler and the cyclone dust collector to a temperature range that the bag dust collector can withstand; the secondary cooling system directly uses an air cooler (waste heat recovery device or system) or directly sets a cold air valve on the pipeline.

[0030] The ash collected by the bypass ventilation system needs to be washed with water to extract salt, and the salt-containing wastewater after washing needs to be evaporated and crystallized. During the evaporation process, both the MVR process and the MED (triple effect evaporation) process require high energy consumption. Therefore, a waste heat recovery system can be set up to utilize the moist heat in the exhaust gas of the cyclone dust collector, and generate steam after part of the energy is exchanged for heat to supply the subsequent evaporation of the salt-containing wastewater.

[0031] In this embodiment, the exhaust port (air intake port) of the bypass venting system should avoid or be far away from the area with high dust concentration as much as possible to avoid bringing out a large amount of dust particles (the dust particles inside the smoke chamber will not adsorb chloride ions). In this embodiment, in order to achieve the best use effect, the air intake port is set on the upper side of the smoke chamber close to the rotary kiln, and the wind speed of the smoke chamber shrinkage should not be affected as much as possible.

[0032] The bypass ventilation ratio is 5%-10%. Figure 2-3 , 300t / d alternative fuel, when the chlorine content in the alternative fuel is 1.6% and 2.5% respectively, the influence of different bypass ventilation system ratios on various parameters is shown in the structural diagram. Bypass ventilation has a significant effect on reducing clinker chloride ions. However, bypass ventilation is not significant in reducing C5 hot raw material chloride ions. This is related to the high total amount of chlorine brought into the system and the high volatility of chlorine in the system. After adding alternative fuel from the kiln tail, the extremely strong high-temperature volatility of chlorine can easily form a cycle enrichment between the bottom of the decomposition furnace and the C5 cyclone dust collector and its material pipe, and it is easy to form a crust and agglomeration at the final cyclone dust collector. At present, most of the new dry process cement plants in China usually control the hot raw material chloride ions of C5 feed pipe below 0.8% to 1.0%.

[0033] When the received basic chloride ion of the alternative fuel is 1.6% (average value), the bypass air venting ratio of 6% can meet the clinker chlorine control requirements (required to be less than 0.04%), but cannot take into account the chlorine content of C5 hot raw meal; when the bypass air venting ratio is 10%, the chlorine content of C5 hot raw meal can be controlled at about 1%; When the basic chloride ion content of the alternative fuel is 2.5% (maximum value), the bypass air venting ratio of 9% can meet the clinker chlorine control requirements, but cannot take into account the chlorine content of C5 hot raw meal; when the bypass air venting ratio is 14%, the chlorine content of C5 hot raw meal can be controlled at about 1%; Taking into account the bypass ash discharge, system heat loss, increased nitrogen oxide concentration in the chimney at the kiln tail (without SCR), investment cost and other factors, and referring to the recommended data of FLSmith, the optimal ratio of bypass venting in this embodiment can be set at 10%.

[0034] See also Figure 4-5 The temperature distribution cloud diagram of the main section of the quencher and the volute interface is shown. The quencher adopts a volute structure. The blown cold air enters the volute mixing chamber in a tangential manner, quickly wrapping the high-temperature flue gas from the air intake in the center without letting it stick to the wall, fundamentally avoiding the condensation of volatile substances such as chlorine and alkali in the hot air flow on the wall to form a crust.

[0035] See also Figure 8The quencher is provided with a double air duct inside. The cold air cut into the mixing chamber of the volute by the quencher is cut into the high-temperature flue gas in two directions. In order to improve the use effect, the outlet wind speed of the two-way air duct is designed to be the same. In addition, the pipe diameter of the flue gas outlet at the upper end of the quencher is larger than the pipe diameter of the flue gas inlet at the lower end.

[0036] In this embodiment, when the bypass air ratio is 10%, the calculation result of the amount of cold air that needs to be added to the quench cooler is as follows: Figure 6 As shown, the theoretical amount of cold air is 25000Nm 3 / h, the outlet temperature of the quencher dropped to 390℃.

[0037] See also Figure 7 As shown in the structural diagram of the waste heat recovery system, the high-temperature flue gas is heat-exchanged after entering the evaporator, thereby reducing the temperature of the flue gas, so that the flue gas can enter the bag filter at a lower temperature.

[0038] The washing workshop is equipped with a washing and dehydration system, the main function of which is to dissolve the soluble ions in the bypass vent ash, especially chlorine, potassium and sodium ions, in water as much as possible. The insoluble filter cake is centrifugally dehydrated and then washed several times, and the chloride ion concentration in the filter cake is finally reduced to below 1%. Because potassium chloride and sodium chloride have high solubility in water, the saturated solubility of potassium chloride at room temperature can reach 34 grams, and the saturated solubility of sodium chloride at room temperature is 36 grams, both of which are very soluble in water, so potassium chloride and sodium chloride in the bypass vent ash are easily eluted.

[0039] In this embodiment, the bypass vent ash is discharged from the ash bin into the buffer ash bin, and after being measured, it is mixed with clean water (supplemented by steam condensate or tap water in the plant area) in a certain proportion and enters the dissolution stirring tank. The dissolved ash-containing slurry is discharged into the centrifugal buffer tank for subsequent centrifugal separation. The filter cake obtained by centrifugation is then washed with clean water, and the mother liquor obtained by centrifugation enters the mother liquor buffer tank and then enters the mother liquor purification system. The elution is repeated to ensure that the chlorine content in the filter cake reaches the designed value.

[0040] The bypass venting system of the present invention can effectively alleviate the crusting problem caused by high levels of raw materials, fuel alkali, chlorine and sulfur, ensure the smooth operation of the production line, and ensure the quality of cement. The volute-type quencher is used, and the cold air is mixed with the high-temperature flue gas in a cut-in manner, which can quickly wrap the high-temperature flue gas, eliminate the possibility of high-temperature flue gas adhering to the wall in the mixing chamber, and reduce the possibility of blockage of the quencher.

[0041] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A bypass venting system, characterized in that: It includes an air intake port opened in the smoke chamber, a quencher connected to the air intake port, a cyclone dust collector, a bag dust collector, an ash bin and a pneumatic conveying device; the quencher adopts a volute structure, and the air inlet port of the quencher is connected to a rapid cooling fan; the high-temperature flue gas after the quencher enters the cyclone dust collector, and the cyclone dust collector returns the coarse particles in the flue gas to the decomposition furnace, and the coarser particles return to the kiln tail, thereby reducing part of the material consumption and heat consumption; The fine dust particles separated by the cyclone dust collector enter the bag dust collector and are collected, and the clean air is discharged directly into the chimney at the end of the kiln through the exhaust fan; the ash collected in the bag dust collector is first transported to the ash silo, and then the dense phase conveying method is used to transport the ash to the steel silo at the clinker conveyor belt or to the ash buffer bin in the washing workshop for water washing.

2. A bypass venting system according to claim 1, characterized in that: A secondary cooling system is provided in front of the inlet of the bag dust collector, and the secondary cooling system can further cool the hot flue gas passing through the quencher and the cyclone dust collector to a temperature range that the bag dust collector can withstand; the secondary cooling system adopts a waste heat recovery system or directly sets a cold air valve on the pipeline.

3. A bypass venting system according to claim 1, characterized in that: The air intake is arranged on one side of the upper part of the kiln tail smoke chamber close to the rotary kiln, and the position of the air intake has the smallest influence on the wind speed of the smoke chamber shrinkage.

4. A bypass venting system according to claim 1, characterized in that: The bypass ventilation ratio is 5%-10%.

5. A bypass venting system according to claim 2, characterized in that: The waste heat recovery system includes an evaporator. After entering the evaporator, the high-temperature flue gas is heat-exchanged and then the temperature is reduced again. The flue gas with reduced temperature passes through the economizer and then enters the bag filter.

6. A bypass venting system according to claim 1, characterized in that: The water washing workshop is equipped with a water washing and dehydration system, which dissolves the soluble ions in the bypass ash in water as much as possible, and the insoluble filter cake is centrifugally dehydrated and then washed several times, and finally the chloride ion concentration in the filter cake is reduced to below 1%.

7. A bypass venting system according to claim 6, characterized in that: The ash in the ash bin is discharged into the buffer ash bin and enters the dissolution stirring tank with clean water. The dissolved ash-containing slurry is discharged into the centrifugal buffer tank for subsequent centrifugal separation. The filter cake obtained by centrifugation is washed with clean water, and the mother liquor obtained by centrifugation enters the mother liquor buffer tank and then enters the mother liquor purification system. The elution is repeated to ensure that the chlorine content in the filter cake meets the standard.

8. A bypass venting system according to any one of claims 1 to 7, characterized in that: The interior of the quencher is provided with double air ducts. The cold air cut into the volute mixing chamber by the quencher enters the mixing chamber in two directions and wraps the high-temperature flue gas. The wind speed at the outlet of the two-way air duct is the same.

9. A bypass venting system according to claim 8, characterized in that: The pipe diameter of the smoke outlet at the upper end of the quench cooler is larger than the pipe diameter of the smoke inlet at the lower end.

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