Coal gangue ceramsite roasting smoke and air circulation system for cooling high-temperature ceramsite through hot air circulation

Abstract

The embodiment of the invention provides a coal gangue ceramsite roasting smoke and air circulation system for cooling high-temperature ceramsite through hot air circulation, and relates to the technical field of roasting hot air circulation utilization. According to the invention, the low-temperature flue gas with the temperature of 200-400 DEG C and the oxygen content of 15-19%, which is discharged from the preheating section of the coal gangue ceramsite with the raw material calorific value of 300-1000kcal / kg, is introduced into the high-temperature cooling section for cooling the high-temperature ceramsite with the temperature of 1120-1200 DEG C in the high-temperature cooling section; the low-temperature flue gas absorbs sensible heat under the condition that the flue gas flow is 400-1000 Nm < 3 > / t and then is heated to form 850-1000 DEG C high-temperature flue gas which is reused in a roasting section, a soaking section or a waste heat boiler, and a complete hot air closed-loop circulation system of'cooling ceramsite by the low-temperature flue gas, heating into high-temperature combustion-supporting air and recycling 'is constructed. Energy waste caused by direct emission of low-temperature flue gas is avoided, and the overall heat efficiency of the system is remarkably improved; and meanwhile, the flue gas flows through the material layer, so that flue gas dust is reduced, and the stability of subsequent waste heat utilization and other processes is improved.

Description

Technical Field

[0001] This invention relates to the field of roasting hot air circulation technology, and in particular to a coal gangue ceramsite roasting flue gas circulation system for circulating hot air to cool high-temperature ceramsite. Background Technology

[0002] Coal gangue ceramsite is a lightweight aggregate produced from coal gangue as the main raw material through processes such as pelletizing and roasting. It is widely used in construction, environmental protection, and chemical industries. In current industrial practice, coal gangue ceramsite is typically produced continuously using equipment such as belt roasters, tunnel kilns, or sintering machines.

[0003] During the roasting of high-calorific-value coal gangue, the preheating section emits a large amount of low-temperature, low-quality flue gas due to the internal combustion decarbonization reaction. However, traditional roasting systems generally lack an effective way to utilize this low-temperature, low-quality flue gas. Because of its low temperature, it is difficult to use it for power generation or efficient waste heat recovery, and most existing systems directly discharge it into the atmosphere, resulting in a significant waste of low-grade heat energy.

[0004] Meanwhile, the temperature of the ceramsite discharged from the heat exchange section is usually above 1100℃, and it must be cooled before subsequent conveying, screening, and storage. Currently, the mainstream cooling method is to use ambient air for forced convection cooling of the high-temperature ceramsite. However, due to the low initial temperature and limited heat capacity of the air, the obtained hot air energy level is not high, and the uneven distribution of cooling intensity often leads to differences in the internal structure of the ceramsite, affecting the consistency of product performance.

[0005] Furthermore, in existing calcination systems, flue gas emission and ceramsite cooling are typically operated as two independent units, lacking energy synergy between them. Low-temperature flue gas is not effectively utilized, and the cooling process requires the introduction of additional cold air, which not only increases fan energy consumption but also makes it difficult to further improve the overall thermal efficiency of the system. Summary of the Invention

[0006] To address the technical problems in existing technologies where the low-temperature flue gas generated during the calcination of ceramsite is not effectively utilized and is directly emitted, resulting in wasted thermal energy, and where the need to introduce additional ambient cold air for ceramsite cooling leads to low overall system thermal efficiency, this invention provides a hot air circulation system for cooling high-temperature ceramsite in coal gangue ceramsite calcination. The technical solution is as follows:

[0007] This invention provides a coal gangue ceramsite roasting flue gas circulation system for hot air circulation cooling of high-temperature ceramsite, comprising: a roasting device and / or a waste heat utilization boiler; the roasting device comprises: a preheating section, a roasting section, a homogenizing section and a high-temperature cooling section connected in sequence;

[0008] The preheating section and the high-temperature cooling section are connected by a flue gas duct;

[0009] The high-temperature cooling section is connected to the roasting section and / or the homogenization section via a flue gas duct; and / or, the high-temperature cooling section is connected to the waste heat utilization boiler via a flue gas duct.

[0010] The calorific value of the raw coal gangue ceramsite pellets used is 300-1000 kcal / kg;

[0011] The raw coal gangue ceramsite pellets undergo internal combustion and decarbonization reaction in the preheating section, emitting low-temperature flue gas with a temperature of 200-400℃ and an oxygen content of 15-19%.

[0012] The low-temperature flue gas is introduced into the high-temperature cooling section to cool the high-temperature ceramsite in the high-temperature cooling section at a temperature of 1120-1200℃.

[0013] The volumetric flow rate of the low-temperature flue gas entering the high-temperature cooling section is controlled to be 400-1000 Nm³ per ton of high-temperature ceramsite. 3 The low-temperature flue gas absorbs heat and rises in temperature after exchanging heat with the high-temperature ceramic particles, forming high-temperature flue gas with a temperature of 850-1000℃.

[0014] The high-temperature flue gas is circulated to the roasting section and / or the homogenization section for reuse as combustion air; and / or, the high-temperature flue gas is transported to a waste heat boiler for heat exchange.

[0015] During the calcination of coal gangue ceramsite, the calcination and soaking stages need to maintain a stable high-temperature environment of 1120-1200℃ for an extended period to ensure that the ceramsite fully expands, sinters, and forms a stable porous lightweight structure. This high-temperature environment mainly relies on the combustion of external fuels such as natural gas for heating. As a key component of the combustion reaction, the temperature, oxygen content, and cleanliness of the combustion air directly determine the combustion efficiency, flame stability, pollutant generation level, and overall system energy consumption.

[0016] Engineering practice and thermal simulation analysis show that when the combustion air temperature is below 850℃, its sensible heat is limited, resulting in a weak effect on raising the flame temperature in the main combustion zone and failing to effectively promote complete fuel combustion. However, when the combustion air temperature reaches above 850℃, it can significantly increase the theoretical combustion temperature, enhance radiative heat transfer intensity, shorten the combustion reaction time, and reduce the generation of incomplete combustion products (such as CO and soot). Furthermore, high-temperature combustion air can directly replace part of the natural gas input, achieving an energy substitution effect of "heat instead of gas," saving operating costs in large-scale production. However, if the combustion air temperature exceeds 1000℃, it will significantly exacerbate the risks of thermal shock spalling of pipeline refractory materials, and may even cause local overheating or secondary combustion accidents. More importantly, the high-temperature cooling section cannot achieve sufficient cooling of the ceramsite, resulting in the inability of the subsequent medium- and low-temperature cooling section to cool the ceramsite to below 120℃ in time, which will threaten the safe and stable operation of subsequent unloading, belt conveyor, and screening systems. Therefore, 850-1000℃ has been determined as the ideal temperature window for high-oxygen combustion air in the coal gangue ceramsite roasting process.

[0017] Based on the aforementioned thermal requirements, this invention innovatively proposes an energy cascade utilization path: low-temperature, low-grade flue gas (200-400℃, oxygen content 15%-19%) emitted from the preheating section, which is normally difficult to utilize efficiently, is introduced into the high-temperature cooling section. This gas undergoes efficient gas-solid heat exchange with the 1120-1200℃ high-temperature ceramsite discharged from the soaking section. By precisely controlling the flue gas flow rate, the low-temperature flue gas fully absorbs the sensible heat of the ceramsite, and its temperature is precisely raised to 850-1000℃. This energy cascade utilization path not only achieves a leap from low-grade heat energy to high-grade heat energy but also endows the flue gas with advantages of high temperature, rich oxygen, and low dust. It can be directly used as high-quality combustion air for energy recovery in the roasting section, soaking section, or waste heat recovery boiler, thus forming a complete closed-loop hot air circulation system of "low-temperature flue gas cooling ceramsite—heating to high-temperature combustion air—recycling," significantly improving energy utilization efficiency and effectively solving the energy waste problem caused by direct discharge of low-temperature flue gas.

[0018] The stable and efficient operation of this technology relies on the coordinated matching of key parameters. Limiting the calorific value of raw coal gangue ceramsite pellets to 300-1000 kcal / kg is a crucial prerequisite for the system's self-sustaining operation. If the calorific value is below 300 kcal / kg, the heat release from internal combustion is insufficient, the preheating section needs to rely on an external heat source, and the resulting flue gas temperature is often below 200℃, the total amount is small, and the heat grade is low. Even if all of it is used for cooling, it is difficult to heat the flue gas to above 850℃, making it impossible to form an effective combustion airflow. If the calorific value exceeds 1000 kcal / kg, the internal combustion reaction in the preheating section is too violent, oxygen is consumed in large quantities, the oxygen content of the flue gas is often below 13%, and it may even contain reducing gases such as CO, making it impossible to directly reuse. Furthermore, it is prone to local overburning, ceramsite melting and agglomeration, damaging the material layer structure, and affecting heat exchange and transportation. Only within the range of 300-1000 kcal / kg can raw coal gangue pellets undergo moderate internal combustion and decarbonization in the preheating section, stably generating oxygen-rich flue gas at 200-400℃ with an oxygen content of 15%-19%, while ensuring that the ceramsite reaches the ideal furnace exit temperature of 1120-1200℃ after roasting.

[0019] Choosing high-temperature ceramsite at 1120-1200℃ as the heat exchange medium is advantageous for two reasons. Firstly, this temperature range is the critical firing window for coal gangue ceramsite to form a lightweight, high-strength, low-water-absorption porous structure. Below 1120℃, expansion is insufficient, resulting in low porosity and failing to meet the performance requirements of lightweight aggregates. Above 1200℃, over-sintering can easily occur, causing cell collapse or closure, making the ceramsite heavier and more brittle, and even leading to melting and adhesion, affecting product quality and potentially clogging equipment. Secondly, ceramsite at 1120-1200℃ has a complete structure, high strength, and good permeability immediately after leaving the soaking zone, forming a uniform and stable material layer. This provides an efficient and uniform heat exchange channel for the flue gas, and the sensible heat it carries is just sufficient to control the airflow at 400-1000 Nm³. 3 Under the condition of / t, the flue gas at 200-400℃ is precisely heated to the target range of 850-1000℃, which not only meets the thermal requirements of the roasting and homogenization sections for high-grade combustion air, but also avoids the safety risks of equipment aging caused by flue gas overheating and the inability of the medium and low temperature cooling section to cool the ceramsite to a sufficiently low temperature required for unloading.

[0020] Optionally, the roasting apparatus further includes a hot air drying section; the hot air drying section is connected to the preheating section via a pipeline, and is used to dry the raw coal gangue ceramsite pellets and then transport them to the preheating section.

[0021] Optionally, the calcination apparatus further includes: a medium-low temperature cooling section; the medium-low temperature cooling section is connected to the high temperature cooling section through a pipeline, and is used to transport the cooled high temperature ceramsite in the high temperature cooling section to the medium-low temperature cooling section for secondary cooling.

[0022] Optionally, the outlet temperature of the cooled high-temperature ceramsite in the high-temperature cooling section is 600-800℃.

[0023] Optionally, the waste heat utilization boiler is also connected to the preheating section via a flue gas pipeline, for returning the high-temperature flue gas after heat exchange in the waste heat utilization boiler to the preheating section for recycling.

[0024] Optionally, the flue gas duct between the preheating section and the high-temperature cooling section is also connected to an air duct to input ambient air so that the oxygen content of the low-temperature flue gas is controlled within the range of 15-19%.

[0025] Optionally, the raw material for the ceramsite includes coal gangue, gasification slag, coal slime, or oil shale.

[0026] The beneficial effects of the technical solutions provided in the embodiments of the present invention include at least the following:

[0027] The hot air circulation cooling system for high-temperature ceramsite in coal gangue calcination provided by this invention precisely couples key parameters such as raw material calorific value, low-temperature flue gas characteristics, ceramsite outlet temperature, and flue gas flow rate to construct a complete closed-loop hot air circulation system: "low-temperature flue gas cooling ceramsite—heating to high-temperature combustion air—recycling and reuse." This system not only solves the energy waste problem caused by direct discharge of low-temperature flue gas in traditional processes, but also eliminates the dependence on ambient cold air in conventional cooling methods, avoiding the reduction in system thermal efficiency caused by the introduction of large amounts of ambient air. Furthermore, by replacing cold air with oxygen-enriched low-temperature flue gas as the cooling medium, it achieves efficient and controllable cooling of ceramsite while simultaneously heating it to 850-1000℃ and reusing it as high-grade combustion air in the combustion section, realizing the high-value utilization of waste flue gas and significantly improving the overall energy utilization efficiency of the system. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is an embodiment of the hot air circulation cooling system for coal gangue ceramsite roasting flue gas circulation provided by the present invention;

[0030] Figure 2 This is another embodiment of the hot air circulation cooling system for coal gangue ceramsite roasting flue gas circulation provided by the present invention;

[0031] Figure 3This is another embodiment of the hot air circulation cooling system for coal gangue ceramsite roasting flue gas circulation provided by the present invention;

[0032] Figure 4 This is another embodiment of the hot air circulation cooling system for coal gangue ceramsite roasting flue gas circulation provided by the present invention;

[0033] Figure 5 This is another embodiment of the present invention, a coal gangue ceramsite roasting flue gas circulation system for hot air circulation cooling high-temperature ceramsite.

[0034] Figure label:

[0035] A1 - Hot air drying section outlet; A2 - Low-temperature flue gas outlet; A3 - Air inlet; C1 - High-temperature cooling section inlet; C2 - Medium-low temperature cooling section inlet; C H1 -High-temperature flue gas inlet; C H2 - Waste heat gas outlet; C H3 - Waste heat gas inlet. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0037] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms “first,” “second,” and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, the terms “an,” “a,” or “the,” and similar terms do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms “comprising,” “including,” or “including,” and similar terms mean that the element or object preceding the word encompasses the element or object listed following the word and its equivalents, without excluding other elements or objects. The terms “connected,” “linked,” or “connected,” and similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect.

[0038] It should be noted that the terms "up", "down", "left", "right", "front" and "back" used in this invention are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0039] Example 1

[0040] like Figure 1 As shown, the coal gangue ceramsite roasting flue gas circulation system of this embodiment includes: a hot air drying section, a preheating section, a roasting section, a homogenizing section, a high-temperature cooling section, and a medium-low temperature cooling section connected in sequence. The calorific value of the raw coal gangue ceramsite pellets used is 420 kcal / kg. During the roasting process of the coal gangue ceramsite pellets, the preheating section will discharge a large amount of excess low-temperature flue gas at 380°C with an oxygen content of 14.6% from the low-temperature flue gas outlet A2; in order to optimize the oxygen content of the combustion air, the above-mentioned low-temperature flue gas is mixed with the ambient air supplied by the air inlet A3 in a certain proportion, so that the oxygen content of the mixed gas is increased to 15.5%.

[0041] A mixed gas, acting as a cooling medium, is introduced into the high-temperature cooling section through inlet C1 to cool the 1180°C high-temperature ceramsite discharged from the homogenization section. The high-temperature ceramsite is cooled to an outlet temperature of 680°C within the high-temperature cooling section. The low-temperature flue gas absorbs sensible heat as it passes through the high-temperature ceramsite layer, raising its temperature to 900°C, thus forming high-temperature flue gas. This high-temperature flue gas exits through high-temperature flue gas inlet C1. H1 The flue gas enters the calcination and soaking sections and is used as combustion air, completing a full hot air closed-loop circulation system. In this embodiment, the volumetric flow rate of the low-temperature flue gas introduced into the high-temperature cooling section is 400 Nm³ per ton of high-temperature ceramsite. 3 .

[0042] The ceramsite exiting the high-temperature cooling section enters the medium-low temperature cooling section. Ambient air enters the medium-low temperature cooling section through inlet C2 to perform secondary cooling on the ceramsite, further reducing its temperature to meet the requirements of subsequent conveying and screening.

[0043] Example 2

[0044] like Figure 2 As shown, the coal gangue ceramsite roasting flue gas circulation system of this embodiment includes: a hot air drying section, a preheating section, a roasting section, a homogenizing section, a high-temperature cooling section, and a medium-low temperature cooling section connected in sequence. This embodiment uses raw coal gangue pellets with a calorific value of 600 kcal / kg. The preheating section generates low-temperature flue gas at a temperature of 360℃ and an oxygen content of 17.1%. This low-temperature flue gas is discharged from the low-temperature flue gas outlet A2 of the preheating section and sent to the high-temperature cooling section inlet C1 to cool the high-temperature ceramsite at 1170℃. The high-temperature ceramsite has an outlet temperature of 750℃ in the high-temperature cooling section. After absorbing heat, the low-temperature flue gas temperature rises to 1000℃, forming high-temperature flue gas. This high-temperature flue gas enters a waste heat utilization boiler (shown as "waste heat utilization") for heat exchange to prepare medium-pressure steam. After heat exchange in the waste heat utilization boiler, the high-temperature flue gas temperature drops to 360℃. A portion of the heat-exchanged high-temperature flue gas passes through the waste heat gas inlet C1. H3 The heat is returned to the preheating section, and another portion passes through the waste heat gas outlet C. H2The gas enters the flue gas emission system and is discharged after environmental treatment. In this embodiment, the volumetric flow rate of the low-temperature flue gas is 700 Nm³ per ton of high-temperature ceramsite. 3 .

[0045] The ceramsite exiting the high-temperature cooling section enters the medium-low temperature cooling section. Ambient air enters the medium-low temperature cooling section through inlet C2 to perform secondary cooling on the ceramsite, further reducing its temperature to meet the requirements of subsequent conveying and screening.

[0046] Example 3

[0047] like Figure 3 As shown, the coal gangue ceramsite roasting flue gas circulation system of this embodiment includes: a hot air drying section, a preheating section, a roasting section, a homogenizing section, a high-temperature cooling section, and a medium-low temperature cooling section connected in sequence. This embodiment uses raw coal gangue pellets with a calorific value of 300 kcal / kg. The preheating section discharges low-temperature flue gas at a temperature of 200℃ and an oxygen content of 18.8%. This low-temperature flue gas exits from the low-temperature flue gas outlet A2 of the preheating section and is sent to the high-temperature cooling section inlet C1 to cool the 1120℃ high-temperature ceramsite discharged from the homogenizing section. The high-temperature ceramsite is cooled to an outlet temperature of 800℃ within the high-temperature cooling section. The low-temperature flue gas absorbs sensible heat as it passes through the high-temperature ceramsite layer, raising its temperature to 850℃, thus forming high-temperature flue gas. This high-temperature flue gas has a low temperature and is only discharged from the high-temperature flue gas inlet C1. H1 The gas then enters the heat exchange section, completing the full hot air closed-loop circulation system. In this embodiment, the volumetric flow rate of the low-temperature flue gas introduced into the high-temperature cooling section is 600 Nm³ per ton of high-temperature ceramsite. 3 .

[0048] The ceramsite exiting the high-temperature cooling section enters the medium-low temperature cooling section. Ambient air enters the medium-low temperature cooling section through inlet C2 to perform secondary cooling on the ceramsite, further reducing its temperature to meet the requirements of subsequent conveying and screening.

[0049] Example 4

[0050] like Figure 4As shown, the coal gangue ceramsite roasting flue gas circulation system of this embodiment includes: a hot air drying section, a preheating section, a roasting section, a homogenizing section, a high-temperature cooling section, and a medium-low temperature cooling section connected in sequence. This embodiment uses raw coal gangue pellets with a calorific value of 1000 kcal / kg. The preheating section discharges low-temperature flue gas at a temperature of 400℃ and an oxygen content of 19%. This low-temperature flue gas is discharged from the low-temperature flue gas outlet A2 of the preheating section and sent to the high-temperature cooling section inlet C1 to cool the 1200℃ high-temperature ceramsite discharged from the homogenizing section. The high-temperature ceramsite is cooled to an outlet temperature of 700℃ within the high-temperature cooling section. The low-temperature flue gas absorbs sensible heat as it passes through the high-temperature ceramsite layer, raising its temperature to 920℃, thus forming high-temperature flue gas. A portion of this high-temperature flue gas is discharged from the high-temperature flue gas inlet C1. H1 One portion is fed into the roasting and soaking sections as combustion air; the other portion enters the waste heat recovery boiler for heat exchange to prepare medium-pressure steam. After heat exchange in the waste heat recovery boiler, the high-temperature flue gas temperature drops to 180℃, and the exhaust gas after heat exchange passes through the waste heat gas outlet C. H2 The gas enters the flue gas emission system and is discharged after environmental treatment. In this embodiment, the volumetric flow rate of the low-temperature flue gas introduced into the high-temperature cooling section is 1000 Nm³ per ton of high-temperature ceramsite. 3 .

[0051] The ceramsite exiting the high-temperature cooling section enters the medium-low temperature cooling section. Ambient air enters the medium-low temperature cooling section through inlet C2 to perform secondary cooling on the ceramsite, further reducing its temperature to meet the requirements of subsequent conveying and screening.

[0052] Example 5

[0053] like Figure 5 As shown, the coal gangue ceramsite roasting flue gas circulation system of this embodiment includes: a hot air drying section, a preheating section, a roasting section, a homogenizing section, a high-temperature cooling section, and a medium-low temperature cooling section connected in sequence. This embodiment uses raw coal gangue pellets with a calorific value of 660 kcal / kg. The preheating section generates low-temperature flue gas at a temperature of 330℃ and an oxygen content of 17.8%. This low-temperature flue gas is discharged from the low-temperature flue gas outlet A2 of the preheating section and sent to the high-temperature cooling section inlet C1 to cool the high-temperature ceramsite at 1120℃. The high-temperature ceramsite reaches a temperature of 710℃ at the outlet of the high-temperature cooling section. After absorbing heat, the low-temperature flue gas rises to 935℃, forming high-temperature flue gas. A portion of this high-temperature flue gas is sent to the high-temperature flue gas inlet C1. H1 One portion is fed into the roasting and soaking sections as combustion air; the other portion enters the waste heat recovery boiler for heat exchange to prepare medium-pressure steam. After heat exchange in the waste heat recovery boiler, the high-temperature flue gas temperature drops to 380℃. The high-temperature flue gas after heat exchange passes through the waste heat gas inlet C. H3 Returning to the preheating section. In this embodiment, the volumetric flow rate of the low-temperature flue gas is 780 Nm³ per ton of high-temperature ceramsite. 3 .

[0054] The ceramsite exiting the high-temperature cooling section enters the medium-low temperature cooling section. Ambient air enters the medium-low temperature cooling section through inlet C2 to further cool the ceramsite, reducing its temperature to meet the requirements of subsequent conveying and screening. The hot air drying section utilizes some of the hot air from the medium-low temperature cooling section to pre-dry the green pellets. The dried, hot, humid exhaust gas is discharged from the hot air drying section outlet A1 or discharged into the preheating section to participate in the internal combustion reaction.

[0055] Example 6

[0056] The coal gangue ceramsite roasting system in this embodiment is the same as in Embodiment 1, except that: this embodiment uses raw coal gangue pellets with a calorific value of 750 kcal / kg, and low-temperature flue gas with an exhaust temperature of 390℃ and an oxygen content of 14.6% in the preheating section. Simultaneously, ambient air is introduced from air inlet A3 to increase the oxygen content to 15.6%. The mixed gas is then discharged into the high-temperature cooling section to cool the 1150℃ high-temperature ceramsite discharged from the homogenization section. The high-temperature ceramsite is cooled to an outlet temperature of 690℃ in the high-temperature cooling section. The low-temperature flue gas absorbs sensible heat as it passes through the high-temperature ceramsite layer, raising its temperature to 960℃, thus forming high-temperature flue gas. This high-temperature flue gas enters the roasting section and homogenization section as combustion air, completing the hot air circulation cooling system. In this embodiment, the volumetric flow rate of the low-temperature flue gas introduced into the high-temperature cooling section is 600 Nm³ per ton of high-temperature ceramsite. 3 .

[0057] Comparative Example 1-1

[0058] The coal gangue ceramsite roasting flue gas circulation system in this comparative example includes: a hot air drying section, a preheating section, a roasting section, a homogenizing section, a high-temperature cooling section, and a medium-low temperature cooling section connected in sequence. This comparative example uses raw coal gangue pellets with a calorific value of 300 kcal / kg. Room temperature air (25°C) is introduced into the high-temperature cooling section to cool the 1125°C high-temperature ceramsite discharged from the homogenizing section to the high-temperature cooling section. The high-temperature ceramsite is cooled to an outlet temperature of 580°C within the high-temperature cooling section. The room temperature air absorbs sensible heat as it passes through the high-temperature ceramsite layer, raising its temperature to 690°C, forming high-temperature flue gas. This high-temperature flue gas has a relatively low temperature and only a portion circulates into the preheating section, resulting in poor overall heat utilization. In this embodiment, the volumetric flow rate of the low-temperature flue gas introduced into the high-temperature cooling section is 600 Nm³ per ton of high-temperature ceramsite. 3 .

[0059] Comparative Examples 1-2

[0060] The coal gangue ceramsite roasting flue gas circulation system in this comparative example includes: a hot air drying section, a preheating section, a roasting section, a homogenizing section, a high-temperature cooling section, and a medium-low temperature cooling section connected in sequence. This comparative example uses raw coal gangue pellets with a calorific value of 1000 kcal / kg. Room temperature air (25°C) is introduced into the high-temperature cooling section to cool the 1125°C high-temperature ceramsite discharged from the homogenizing section to the high-temperature cooling section. The high-temperature ceramsite is cooled to an outlet temperature of 650°C within the high-temperature cooling section. The room temperature air absorbs sensible heat as it passes through the high-temperature ceramsite layer, raising its temperature to 780°C, forming high-temperature flue gas. This high-temperature flue gas has a relatively low temperature and only a portion circulates into the preheating section, resulting in poor overall heat utilization. In this embodiment, the volumetric flow rate of the low-temperature flue gas introduced into the high-temperature cooling section is 600 Nm³ per ton of high-temperature ceramsite. 3 .

[0061] Comparative Example 2-1

[0062] The flue gas circulation system for the coal gangue ceramsite roasting in this comparative example is the same as in Example 3, except that: this comparative example uses raw coal gangue pellets with a calorific value of 280 kcal / kg, and low-temperature flue gas with an exhaust temperature of 180℃ and an oxygen content of 19.2% in the preheating section. This low-temperature flue gas is introduced into the high-temperature cooling section to cool the 1123℃ high-temperature ceramsite discharged from the homogenization section to the high-temperature cooling section. The high-temperature ceramsite is cooled to an outlet temperature of 610℃ in the high-temperature cooling section. The low-temperature flue gas absorbs sensible heat as it passes through the high-temperature ceramsite layer, raising its temperature to 730℃, thus forming high-temperature flue gas. This high-temperature flue gas has a relatively low temperature and only a portion circulates into the preheating section, resulting in poor overall heat utilization. In this example, the volumetric flow rate of the low-temperature flue gas introduced into the high-temperature cooling section is 600 Nm³ per ton of high-temperature ceramsite. 3 .

[0063] Comparative Example 2-2

[0064] The flue gas circulation system for the coal gangue ceramsite roasting in this comparative example is the same as in Example 3, except that: this comparative example uses raw coal gangue pellets with a calorific value of 1050 kcal / kg, and low-temperature flue gas with an exhaust temperature of 490℃ and an oxygen content of 15.3% in the preheating section. This low-temperature flue gas is introduced into the high-temperature cooling section to cool the 1160℃ high-temperature ceramsite discharged from the homogenization section to the high-temperature cooling section. The high-temperature ceramsite is cooled to an outlet temperature of 870℃ in the high-temperature cooling section, but caking and red lumps appear in the high-temperature ceramsite, resulting in unqualified products. The low-temperature flue gas absorbs heat as it passes through the high-temperature ceramsite layer, resulting in poor heat exchange and a temperature rise of only 950℃. This high-temperature flue gas has a low oxygen content and temperature and enters the homogenization section. In this example, the volumetric flow rate of the low-temperature flue gas introduced into the high-temperature cooling section is 800 Nm³ per ton of high-temperature ceramsite. 3 .

[0065] Comparative Example 3-1

[0066] The flue gas circulation system for coal gangue ceramsite roasting in this comparative example is the same as in Example 3, except that: this comparative example uses raw coal gangue pellets with a calorific value of 295 kcal / kg, and low-temperature flue gas with an exhaust temperature of 155℃ and an oxygen content of 20.4% in the preheating section. This low-temperature flue gas is introduced into the high-temperature cooling section to cool the 1125℃ high-temperature ceramsite discharged from the homogenization section to the high-temperature cooling section. The high-temperature ceramsite is cooled to an outlet temperature of 603℃ in the high-temperature cooling section. The low-temperature flue gas absorbs sensible heat as it passes through the high-temperature ceramsite layer, raising its temperature to 746℃, thus forming high-temperature flue gas. This high-temperature flue gas has a relatively low temperature and only a portion circulates into the preheating section, resulting in poor overall heat utilization. In this example, the volumetric flow rate of the low-temperature flue gas introduced into the cooling section is 700 Nm³ per ton of high-temperature ceramsite. 3 .

[0067] Comparative Example 3-2

[0068] The flue gas circulation system for the coal gangue ceramsite roasting in this comparative example is the same as in Example 3, except that: this comparative example uses raw coal gangue pellets with a calorific value of 500 kcal / kg, and low-temperature flue gas with an exhaust temperature of 420℃ and an oxygen content of 15.1% in the preheating section. This low-temperature flue gas is introduced into the high-temperature cooling section to cool the 1125℃ high-temperature ceramsite discharged from the homogenization section to the high-temperature cooling section. The high-temperature ceramsite is cooled to an outlet temperature of 920℃ in the high-temperature cooling section. The low-temperature flue gas absorbs sensible heat as it passes through the high-temperature ceramsite layer, raising its temperature to 1035℃, thus forming high-temperature flue gas. This high-temperature flue gas has a low oxygen content and a low temperature, and only enters the homogenization section. In this example, the volumetric flow rate of the low-temperature flue gas introduced into the cooling section is 500 Nm³ per ton of high-temperature ceramsite. 3 .

[0069] The ceramsite exiting the high-temperature cooling section enters the medium-low temperature cooling section. Ambient air enters the medium-low temperature cooling section through inlet C2 to perform secondary cooling on the ceramsite. After secondary cooling, the temperature of the ceramsite is reduced to only 270℃, which cannot meet the requirements for subsequent unloading, belt conveying and screening.

[0070] Comparative Example 4-1

[0071] The flue gas circulation system for the coal gangue ceramsite roasting in this comparative example is the same as in Example 3, except that: this comparative example uses raw coal gangue pellets with a calorific value of 340 kcal / kg, and low-temperature flue gas with an exhaust temperature of 380℃ and an oxygen content of 13% in the preheating section. This low-temperature flue gas is introduced into the high-temperature cooling section to cool the 1125℃ high-temperature ceramsite discharged from the homogenization section to the high-temperature cooling section. The high-temperature ceramsite is cooled to an outlet temperature of 720℃ in the high-temperature cooling section C1. The low-temperature flue gas absorbs sensible heat as it passes through the high-temperature ceramsite layer, raising its temperature to 951℃, thus forming high-temperature flue gas. This high-temperature flue gas has a low oxygen content and cannot support the combustion of fuel gas in the roasting section, resulting in low thermal efficiency; it only enters the waste heat utilization boiler and is discharged from the waste heat gas outlet CH2 after waste heat utilization. In this example, the volumetric flow rate of the low-temperature flue gas introduced into the high-temperature cooling section is 600 Nm³ per ton of high-temperature ceramsite. 3 .

[0072] Comparative Example 4-2

[0073] The flue gas circulation system for the coal gangue ceramsite roasting in this comparative example is the same as in Example 3, except that: this comparative example uses raw coal gangue pellets with a calorific value of 650 kcal / kg, and low-temperature flue gas with an exhaust temperature of 150℃ and an oxygen content of 20.5% in the preheating section. This low-temperature flue gas is introduced into the high-temperature cooling section to cool the 1150℃ high-temperature ceramsite discharged from the homogenization section to the high-temperature cooling section. The high-temperature ceramsite is cooled to an outlet temperature of 605℃ in the high-temperature cooling section C1. The low-temperature flue gas absorbs sensible heat as it passes through the high-temperature ceramsite layer, raising its temperature to 815℃. This high-temperature flue gas has a low temperature and low heat utilization efficiency, only entering the waste heat recovery boiler. After waste heat recovery, it is discharged from the waste heat gas outlet CH2, resulting in a low heat recycling rate. In this example, the volumetric flow rate of the low-temperature flue gas introduced into the high-temperature cooling section is 600 Nm³ per ton of high-temperature ceramsite. 3 .

[0074] Comparative Example 5-1

[0075] The flue gas circulation system for the coal gangue ceramsite roasting in this comparative example is the same as in Example 3, except that: this comparative example uses raw coal gangue pellets with a calorific value of 350 kcal / kg, and low-temperature flue gas with an exhaust temperature of 205℃ and an oxygen content of 17.5% in the preheating section. This low-temperature flue gas is introduced into the high-temperature cooling section to cool the 1080℃ high-temperature ceramsite discharged from the homogenization section to the high-temperature cooling section. The high-temperature ceramsite is cooled to an outlet temperature of 652℃ in the high-temperature cooling section C1. The low-temperature flue gas absorbs sensible heat as it passes through the high-temperature ceramsite layer, raising its temperature to 738℃, thus forming high-temperature flue gas. This high-temperature flue gas has a relatively low temperature and only enters the waste heat utilization boiler, where it is discharged from the waste heat gas outlet CH2 after waste heat utilization. In this example, the volumetric flow rate of the low-temperature flue gas introduced into the high-temperature cooling section is 600 Nm³ per ton of high-temperature ceramsite. 3 .

[0076] Comparative Example 6-1

[0077] The flue gas circulation system for the coal gangue ceramsite roasting in this comparative example is the same as in Example 3, except that: this comparative example uses raw coal gangue pellets with a calorific value of 300 kcal / kg, and low-temperature flue gas with an exhaust temperature of 202℃ and an oxygen content of 15.1% in the preheating section. This low-temperature flue gas is introduced into the high-temperature cooling section to cool the 1122℃ high-temperature ceramsite discharged from the homogenization section to the high-temperature cooling section. The high-temperature ceramsite is cooled to an outlet temperature of 890℃ in the high-temperature cooling section C1. The low-temperature flue gas absorbs sensible heat as it passes through the high-temperature ceramsite layer, raising its temperature to 980℃, thus forming high-temperature flue gas. This high-temperature flue gas has a low oxygen content and a low temperature, and only enters the waste heat utilization boiler. After waste heat utilization, it is discharged from the waste heat gas outlet CH2. In this example, the volumetric flow rate of the low-temperature flue gas introduced into the high-temperature cooling section is 350 Nm³ per ton of high-temperature ceramsite. 3 .

[0078] The ceramsite exiting the high-temperature cooling section enters the medium-low temperature cooling section. Ambient air enters the medium-low temperature cooling section through inlet C2 to perform secondary cooling on the ceramsite. After secondary cooling, the temperature of the ceramsite is reduced to only 260℃, which cannot meet the requirements for subsequent unloading, belt conveying and screening.

[0079] Comparative Example 6-2

[0080] The flue gas circulation system for the coal gangue ceramsite roasting in this comparative example is the same as in Example 3, except that: this comparative example uses raw coal gangue pellets with a calorific value of 350 kcal / kg, and low-temperature flue gas with an exhaust temperature of 201℃ and an oxygen content of 15.3% in the preheating section. This low-temperature flue gas is introduced into the high-temperature cooling section to cool the 1120℃ high-temperature ceramsite discharged from the homogenization section to the high-temperature cooling section. The high-temperature ceramsite is cooled to an outlet temperature of 660℃ in the high-temperature cooling section C1. The low-temperature flue gas absorbs sensible heat as it passes through the high-temperature ceramsite layer, raising its temperature to 725℃, thus forming high-temperature flue gas. This high-temperature flue gas has a low oxygen content and a low temperature, and only enters the waste heat utilization boiler. After waste heat utilization, it is discharged from the waste heat gas outlet CH2. In this example, the volumetric flow rate of the low-temperature flue gas introduced into the high-temperature cooling section is 1100 Nm³ per ton of high-temperature ceramsite. 3 .

[0081] The comparative analysis of the above comparative examples and Embodiment 3 of the present invention shows that whether the final high-temperature flue gas can reach the ideal temperature window of 850-1000℃ highly depends on the coordinated matching of multiple key parameters. Specifically:

[0082] When ambient air is used instead of low-temperature flue gas to cool high-temperature ceramsite, the flue gas has limited heat absorption capacity due to the low inlet medium temperature and the lack of internal combustion heat source support, resulting in the final high-temperature flue gas temperature being less than 850℃ (Comparative Examples 1-1 and 1-2). At the same time, the large amount of low-temperature flue gas of 200-400℃ emitted by ceramsite with a calorific value greater than 300kcal / kg raw material is only used as a low-quality waste heat resource, with low utilization value or directly discharged after cooling air.

[0083] When the calorific value of the raw material is below 300 kcal / kg, the heat released by internal combustion is insufficient, and the preheating section is unable to produce sufficient low-temperature flue gas, or the temperature and total amount of flue gas produced are both too low, making it difficult to effectively heat to the target range; while when the calorific value exceeds 1000 kcal / kg, the combustion in the preheating section is too intense, and although the flue gas temperature may rise, it is often accompanied by oxygen depletion or system overheating, which ultimately easily leads to the caking and red lumps of high-temperature ceramsite, resulting in unqualified products and making it difficult for production to proceed smoothly (Comparative Examples 2-1, 2-2).

[0084] When the initial temperature of the low-temperature flue gas is below 200℃, the heat grade is insufficient, and even with sufficient heat exchange, it is difficult to reach 850℃. When the temperature exceeds 400℃, it often reflects process imbalance. At the same time, the superimposed sensible heat of the ceramsite can easily lead to the final high-temperature flue gas exceeding 1000℃. Meanwhile, the cooling effect of the ceramsite in the high-temperature section is poor, making it difficult to cool the ceramsite to the unloading temperature (less than 120℃) within the required time in the medium and low temperature sections (Comparative Examples 3-1 and 3-2).

[0085] When the oxygen content of the low-temperature flue gas is below 15%, it usually means that it cannot directly support the combustion of the gas in the roasting section, resulting in low heat cycle utilization. When the oxygen content exceeds 19%, the combustion effect in the preheating section is poor, the flue gas temperature is difficult to exceed 200℃, the flue gas temperature rises at a low temperature, and the heat cycle utilization effect is poor (Comparative Examples 4-1 and 4-2).

[0086] When the temperature of the high-temperature ceramsite is below 1120℃, its sensible heat is insufficient to support the flue gas temperature to 850℃. When it exceeds 1200℃, the equipment investment and operating costs of the roasting and soaking sections will increase significantly, resulting in poor economic efficiency. At the same time, the energy substitution rate of the high-temperature flue gas at 850-1000℃ after circulation is low and the effect is not obvious (Comparative Example 5-1).

[0087] When the flue gas volume flow rate is less than 400 Nm 3 At a flow rate of / t, the unit flue gas absorbs excessive heat, which may lead to overheating. However, the cooling effect in the high-temperature section of the ceramsite is poor, making it difficult to cool the ceramsite to the unloading temperature (less than 120℃) within the required time in the medium and low-temperature sections. Simultaneously, the low high-temperature air volume results in a low energy substitution rate in the post-circulation support roasting and homogenization sections, making the effect insignificant. Furthermore, when the air volume exceeds 1000 Nm³, the situation becomes more complex. 3When the temperature reaches 850℃, the flue gas is excessively diluted, resulting in insufficient heat absorption and temperature rise. Consequently, the temperature of the high-temperature flue gas is also less than 850℃ (Comparative Examples 6-1 and 6-2).

[0088] Therefore, only when the calorific value of the raw material is controlled at 300-1000 kcal / kg, the temperature of the low-temperature flue gas is maintained at 200-400℃, the oxygen content is kept at 15%-19%, the temperature of the high-temperature ceramsite in the high-temperature cooling section is stabilized at 1120-1200℃, and the flue gas flow rate is precisely controlled at 400-1000 Nm³, can the desired effect be achieved. 3 Only when the temperature reaches / t can the various parameters form an efficient and coordinated thermal matching, so that the final high-temperature flue gas temperature accurately falls into the ideal temperature window of 850-1000℃.

[0089] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A hot air circulation system for cooling high-temperature ceramsite in coal gangue calcination flue gas, characterized in that, include: calcination equipment and / or waste heat utilization boilers; The calcination apparatus includes: a preheating section, a calcination section, a homogenization section, and a high-temperature cooling section connected in sequence; The preheating section and the high-temperature cooling section are connected by a flue gas duct; The high-temperature cooling section is connected to the roasting section and / or the homogenization section via a flue gas duct; and / or, the high-temperature cooling section is connected to the waste heat utilization boiler via a flue gas duct. The calorific value of the raw coal gangue ceramsite pellets used is 300-1000 kcal / kg; The raw coal gangue ceramsite pellets undergo internal combustion and decarbonization reaction in the preheating section, emitting low-temperature flue gas with a temperature of 200-400℃ and an oxygen content of 15-19%. The low-temperature flue gas is introduced into the high-temperature cooling section to cool the high-temperature ceramsite in the high-temperature cooling section at a temperature of 1120-1200℃. The volumetric flow rate of the low-temperature flue gas entering the high-temperature cooling section is controlled to be 400-1000 Nm³ per ton of high-temperature ceramsite. 3 The low-temperature flue gas absorbs heat and rises in temperature after exchanging heat with the high-temperature ceramic particles, forming high-temperature flue gas with a temperature of 850-1000℃. The high-temperature flue gas is circulated to the roasting section and / or the homogenization section for reuse as combustion air; and / or, the high-temperature flue gas is circulated to a waste heat utilization boiler for heat exchange.

2. The hot air circulation cooling system for coal gangue ceramsite roasting flue gas circulation according to claim 1, characterized in that, The roasting apparatus further includes a hot air drying section; the hot air drying section is connected to the preheating section via a pipeline and is used to dry the raw coal gangue ceramsite pellets and then transport them to the preheating section.

3. The hot air circulation cooling system for coal gangue ceramsite roasting flue gas circulation according to claim 1, characterized in that, The calcination apparatus further includes a medium-low temperature cooling section; the medium-low temperature cooling section is connected to the high temperature cooling section through a pipeline, and is used to transport the high-temperature ceramsite cooled in the high temperature cooling section to the medium-low temperature cooling section for secondary cooling.

4. The hot air circulation cooling system for coal gangue ceramsite roasting flue gas circulation according to claim 1, characterized in that, The outlet temperature of the cooled high-temperature ceramsite in the high-temperature cooling section is 600-800℃.

5. The hot air circulation cooling system for coal gangue ceramsite roasting flue gas circulation according to claim 1, characterized in that, The waste heat utilization boiler is also connected to the preheating section via a flue gas pipeline, which is used to return the high-temperature flue gas after heat exchange in the waste heat utilization boiler to the preheating section for recycling.

6. The hot air circulation cooling system for coal gangue ceramsite roasting flue gas circulation according to claim 1, characterized in that, The flue gas duct between the preheating section and the high-temperature cooling section is also connected to an air duct to input ambient air so that the oxygen content of the low-temperature flue gas is controlled within the range of 15-19%.

7. The hot air circulation cooling system for coal gangue ceramsite roasting flue gas circulation according to claim 1, characterized in that, The raw material for coal gangue ceramsite includes coal gangue, gasification slag, coal slime, or oil shale.

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