Raw meal preheating system of cement clinker production line

Abstract

The present invention discloses a raw material preheating system for a cement clinker production line, which includes several stages of cyclones and their connecting pipes. Among them, the flue gas outlet of the C1 cyclone is connected to a C1 waste gas air duct, and the outlet of the C1 waste gas air duct is connected to an external cyclone for preheating the raw material. The external cyclone is located outside the kiln tail frame; the flue gas from the C1 cyclone enters the external cyclone through the C1 waste gas air duct, and performs gas-solid heat exchange with the raw material entering the external cyclone. The heated raw material after heat exchange is transported to the connecting pipe between the C2 and C1 of the kiln tail preheater, and the cooled flue gas enters the raw material grinding and kiln tail waste gas treatment system. The present invention increases the number of preheater stages through an external cyclone, improves the system thermal efficiency, and thus reduces the heat consumption of the firing system; the present invention is used for the transformation of the existing cement clinker firing system, with less investment, short construction period, and significant reduction in system heat consumption, and has good economic and social benefits.

Description

Technical Field

[0001] The present invention relates to a raw material preheating system in the cement production process, and particularly to a raw material preheating system for a cement clinker production line. Background Art

[0002] The preheating and precalcining system is the core of the new dry process cement clinker firing system, and its performance is crucial for the stable operation of the entire firing system, as well as technical indicators such as heat consumption and power consumption. Figure 1 It is a schematic diagram of a conventional preheating and precalcining system at home and abroad. The cyclones at all levels of the preheater are stacked in the height direction and placed in front of the kiln tail high-temperature fan and within the kiln tail frame. The more stages the preheater has, the higher the gas-solid heat exchange efficiency, the lower the exhaust gas temperature at the preheater outlet, and the lower the coal consumption of the corresponding system.

[0003] Currently, most kiln tails of cement production lines adopt a five-stage suspension preheater. The preheating of raw materials is completed by a heat exchange unit composed of multiple cyclones and connecting pipes of the cyclones, adopting a co-current heat exchange form. To meet the requirements of carbon emission reduction and improve energy efficiency, newly designed systems generally adopt a six-stage preheater, with a significant reduction in standard coal consumption. Changing from five stages to six stages can meet the demand for a large reduction in heat consumption of the existing five-stage preheater system. If the conventional scheme is adopted, adding a heat exchange unit at the top of the existing kiln tail frame requires adding a layer to the civil engineering kiln tail frame and increasing the load significantly. First, it is necessary to conduct safety inspection and appraisal on the existing civil engineering frame structure, and then carry out reinforcement design and calculation according to the current specifications. Since it is impossible to increase the buried depth of the existing civil engineering foundation of the kiln tail frame through technological transformation, increasing the storey height results in the aspect ratio of the civil engineering frame not meeting the specification requirements, and it is also difficult to meet the requirements of the zero stress zone of the foundation. Usually, the kiln tail frame is rebuilt by demolition, and the reinforcement method is rarely used. Therefore, the technological transformation of changing the preheater from five stages to six stages is difficult, with high investment and a long transformation period.

[0004] Therefore, it is urgent to find a simple, efficient, safe and reliable method for upgrading and reducing consumption of the suspension preheater of the existing cement clinker production line. Summary of the Invention

[0005] Object of the Invention: The object of the present invention is to provide a raw material preheating system for a cement clinker production line that can reduce the coal consumption of the system without affecting the original preheater frame.

[0006] Technical solution: The raw material preheating system of the cement clinker production line of the present invention includes several stages of cyclones and their connecting pipes. Among them, the flue gas outlet of the C1 cyclone is connected to a C1 waste gas air duct, and the outlet of the C1 waste gas air duct is connected to an external cyclone for preheating the raw material. The external cyclone is located outside the kiln tail frame; the flue gas from the C1 cyclone enters the external cyclone through the C1 waste gas air duct and exchanges gas-solid heat with the raw material entering the external cyclone. The heat-exchanged hot raw material is transported to the C2-C1 connecting pipe of the kiln tail preheater, and the cooled flue gas enters the raw material grinding and kiln tail waste gas treatment system.

[0007] Among them, the heat-exchanged hot raw material is transported to the C2-C1 connecting pipe of the kiln tail preheater through a temperature-resistant conveying and lifting device.

[0008] Among them, the outlet of the C1 waste gas air duct is sequentially connected to a waste heat boiler and a high-temperature fan. The external cyclone is arranged between the waste heat boiler and the C1 waste gas air duct, or at the outlet of the high-temperature fan.

[0009] Among them, the raw material is transported into the external cyclone through a material distribution valve.

[0010] Among them, the external cyclone is one stage or multiple stages.

[0011] Among them, the external cyclone is supported by a bracket.

[0012] Among them, 0-100% of the raw material is controlled to enter the external cyclone, and another 100%-0% of the raw material enters the C2-C1 connecting pipe of the kiln tail preheater to meet the temperature control requirements of the system.

[0013] Among them, when 100% of the raw material enters the external cyclone, the temperature of the raw material rises to 190-210°C after preheating, and the temperature of the cooled flue gas is 200-220°C; according to the temperature drop of the waste heat power generation boiler in the conventional six-stage preheater system, the flue gas temperature at the C1 outlet drops to 340-360°C after passing through the waste heat boiler, and the temperature at the outlet of the external cyclone is 200-220°C, which is consistent with the heat recovery efficiency of the conventional six-stage preheater system.

[0014] Beneficial effects: Compared with the prior art, the present invention has achieved the following remarkable effects: (1) By arranging an external cyclone after the exhaust air duct at the kiln tail and outside the civil engineering framework of the preheater to increase the number of preheater stages, the heat recovery efficiency of the system is improved, and the coal consumption is significantly reduced; (2) There is no need to reinforce the civil engineering framework of the preheater of the original cement clinker production line. The system can be transformed from a five-stage preheater system to a six-stage or seven-stage preheater system. The transformation workload is small, the construction period is short, it is easy to implement, and the investment is low. (3) For the system with SCR denitration of kiln tail flue gas and waste heat power generation, due to the increase in the temperature of the gas at the C1 outlet, it is beneficial to improve the SCR denitration efficiency and power generation efficiency. (4) The raw meal entering the preheating unit can be adjusted arbitrarily between 0 and 100%, and the exhaust gas temperature can be controlled to adapt to the change of raw material moisture and meet the demand for drying raw materials with exhaust gas; flexible adjustment can achieve the comprehensive optimum of SCR denitration, waste heat power generation, and system coal consumption. (5) For the cement clinker production line, due to the addition of the raw meal preheating unit, the number of times of mixing of materials and gas in the low-temperature area of the preheater increases. Due to the desulfurization effect of raw meal powder, the SO2 emission can be effectively reduced. Description of the Drawings

[0015] Figure 1 It is a schematic diagram of a five-stage preheating and decomposition system in the prior art;

[0016] Figure 2 It is a schematic diagram of the raw meal preheating system of the present invention. Detailed Embodiments

[0017] The present invention will be further described in detail below.

[0018] Figure 1 It is a schematic diagram of a five-stage preheating and decomposition system in the prior art. As Figure 2 shown, the raw meal preheating system of the cement clinker production line provided by the present invention includes the five-stage preheater at the kiln tail connected in sequence in the prior art, specifically including the C1 cyclone 2, C2 cyclone, C3 cyclone, C4 cyclone, C5 cyclone and decomposition furnace 1 arranged in sequence from top to bottom. There is a C2-C1 connecting pipe 3 between the C1 cyclone and the C2 cyclone. The five-stage preheater at the kiln tail of the present invention is the prior art. The connection relationship between the five-stage cyclones, the connection relationship between the five-stage cyclones and the decomposition furnace, and the operation mode of each component all belong to the prior art. The five-stage preheater at the kiln tail of the present invention is provided with a waste heat boiler 4, a high-temperature fan 5, and a C1 exhaust air duct 6 in sequence at the flue gas outlet of the C1 cyclone 2.

[0019] The outlet of the C1 exhaust gas duct 6 is connected to the external cyclone 7. The exhaust gas duct 6 and the external cyclone 7 are supported by a structural framework and are located outside the kiln tail framework where the C1 cyclone is located. Raw meal is conveyed to the exhaust gas duct 6 through the distributing valve 9 and then conveyed into the external cyclone 7. The flue gas outlet of the external cyclone 7 is connected to the raw meal grinding and exhaust gas treatment system 8; the raw meal grinding and exhaust gas treatment system 8 is a prior art. The material outlet of the external cyclone 7 is connected to the connecting pipe 3 between the C2 - C1 of the kiln tail preheater. A temperature-resistant conveying and lifting device (not shown) is provided at the material outlet of the external cyclone 7, and the heat-exchanged hot raw meal returns to the connecting pipe 3 between the C2 - C1 of the kiln tail preheater through the temperature-resistant conveying and lifting device.

[0020] Working process:

[0021] The flue gas from the C1 cyclone 2 enters the external cyclone 7 through the waste heat boiler 4, the high-temperature fan 5, and the C1 exhaust gas duct 6. The raw meal from the homogenizing silo enters the external cyclone 7 through the distributing valve 9. The input amount of the raw meal is controlled to be 0 - 100%. Gas-solid heat exchange is carried out in the external cyclone 7. The heat-exchanged hot raw meal separated is returned to the connecting pipe 3 between the C2 - C1 of the kiln tail preheater through the temperature-resistant conveying and lifting device, and another 100% - 0 raw meal enters the connecting pipe 3 between the C2 - C1 of the kiln tail preheater to meet the temperature control requirements of the system; the flue gas with reduced temperature enters the raw meal grinding and kiln tail exhaust gas treatment system 8.

[0022] For a cement clinker production line, the exhaust gas outlet temperature of the five-stage preheater system is ~320°C, and the exhaust gas outlet temperature of the six-stage preheater system is ~260°C. After waste heat power generation, the flue gas temperature drops to 220°C. For the system of the present invention, if 100% of the raw meal enters the external cyclone 7, the raw meal temperature rises from ~50°C to 190°C - 210°C, and the C1 outlet exhaust gas temperature is ~400°C. According to the temperature drop situation of the waste heat boiler of the conventional six-stage preheater system, the flue gas temperature after the C1 outlet exhaust gas passes through the waste heat boiler 4 is 340 - 360°C, and the temperature at the outlet of the external cyclone 7 is 200 - 220°C, which is consistent with the heat recovery efficiency of the conventional six-stage preheater system. When the external cyclone 7 is a two-stage cyclone, the heat recovery efficiency is better than that of the conventional six-stage preheater system.

Claims

1. A raw meal preheating system for a cement clinker production line, comprising several stages of cyclones and their connecting pipes, and a decomposition furnace (1), wherein, The flue gas outlet of the C1 cyclone (2) is connected to a C1 exhaust gas duct (6), characterized in that the outlet of the C1 exhaust gas duct (6) is connected to an external cyclone (7) for preheating raw meal, and the external cyclone (7) is located outside the kiln tail frame; the flue gas from the C1 cyclone (2) enters the external cyclone (7) through the C1 exhaust gas duct (6), and performs gas-solid heat exchange with the raw meal entering the external cyclone (7). The heat-exchanged hot raw meal is transported to the C2-C1 connecting pipe (3) of the kiln tail preheater, and the cooled flue gas enters the raw material grinding and kiln tail exhaust gas treatment system (8); the outlet of the C1 exhaust gas duct (6) is sequentially connected to a waste heat boiler (4) and a high-temperature fan (5), and the external cyclone (7) is arranged between the waste heat boiler (4) and the C1 exhaust gas duct (6), or at the outlet of the high-temperature fan (5); the raw meal is transported into the external cyclone (7) through a distributing valve.

2. The raw meal preheating system for a cement clinker production line according to claim 1, characterized in that, The heat-exchanged hot raw meal is transported to the C2-C1 connecting pipe (3) of the kiln tail preheater through a temperature-resistant conveying and lifting device.

3. The raw meal preheating system for a cement clinker production line according to claim 1, characterized in that, The external cyclone (7) is one-stage or multi-stage.

4. The raw meal preheating system for a cement clinker production line according to claim 1, characterized in that, The external cyclone (7) is supported by a bracket.

5. The raw meal preheating system for a cement clinker production line according to claim 1, characterized in that, Control 0-100% of the raw meal to enter the external cyclone (7), and another 100%-0 of the raw meal enters the C2-C1 connecting pipe (3) of the kiln tail preheater to meet the temperature control requirements of the system.

6. The raw meal preheating system for a cement clinker production line according to claim 1, characterized in that, When 100% of the raw meal enters the external cyclone (7), the temperature of the raw meal rises to 190°C - 210°C after preheating, and the temperature of the flue gas leaving the external cyclone is 200 - 220°C.

7. The raw meal preheating system for a cement clinker production line according to claim 1, characterized in that, When 100% of the raw meal enters the external cyclone (7), the temperature of the C1 outlet exhaust gas drops to 340 - 360°C after passing through the waste heat boiler (4).

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