Petroleum coke calcination waste heat stepped recovery rotary kiln system

Abstract

The invention discloses a petroleum coke calcination waste heat stepped recovery rotary kiln system, which belongs to the technical field of rotary kilns, and comprises a kiln body, the kiln body is sequentially provided with a preheating zone and a calcination zone, and the kiln body between the calcination zone and a kiln head is provided with a cooling zone. The cooling zone comprises a first-stage cooling heat exchange section and a second-stage cooling heat exchange section which are sequentially arranged towards the kiln head, the first-stage cooling heat exchange section is used for preheating secondary air, the second-stage cooling heat exchange section is used for cooling calcined coke and recycling heat energy, an annular fin-shaped cooler is arranged on the inner wall of the kiln body of the second-stage cooling heat exchange section, and the annular fin-shaped cooler is used for cooling the calcined coke. A kiln head cover of the kiln body is provided with a rotary joint, and the annular fin-shaped cooler is connected with the outside-kiln heat exchange station through the rotary joint. The cooling zone is arranged in the cylinder of the rotary furnace, secondary air is preheated through the first-stage cooling heat exchange section, heat is recycled in the second-stage cooling heat exchange section through double media of heat conduction oil and demineralized water in a stepped mode, the overall heat recovery rate is obviously increased, and sensible heat waste and comprehensive energy consumption are obviously reduced.

Description

Technical Field

[0001] This invention belongs to the field of rotary kiln technology, and specifically relates to a rotary kiln system for the stepped recovery of waste heat from petroleum coke calcination. Background Technology

[0002] Calcination of petroleum coke is a key process in carbon production. Traditional rotary kilns use a "large kiln-small kiln" separation structure. After calcination, the coke enters the small kiln via a receiving chute and is then cooled by water spray before exiting the kiln.

[0003] Traditional rotary kiln systems have the following problems: The rapid cooling process increases the crack rate of calcined coke particles, affecting particle size stability. High energy consumption; insufficient preheating of secondary and tertiary air during calcination; only the kiln tail flue gas is used to preheat the primary air; secondary air is directly taken from ambient temperature air, resulting in a lower theoretical combustion temperature in the combustion section and increased fuel consumption. The waste heat recovery rate is low. The outlet temperature of calcined coke is generally 800-850℃. The original system only preheats the primary air through radiation heat exchange, resulting in insufficient heat recovery rate. A large amount of sensible heat is lost with the heat dissipation of the kiln body. The evaporation of cooling water causes heat loss. Each ton of calcined coke carries away about 350MJ of sensible heat, resulting in serious heat waste.

[0004] Existing technologies address the modification of traditional rotary kilns. For example, Chinese utility model patent (CN207280180U) discloses a cooling device for a carbon rotary kiln shell. This patent includes an outer jacket over the rotary kiln shell, with a spiral guide plate between the jacket and the kiln shell. One end of the jacket is equipped with a cooling fan, and the other end with an air outlet pipe. After cooling air is supplied to the kiln shell, the cold air temperature increases, forming hot air. This hot air enters the rotary kiln through a secondary air inlet, increasing the combustion temperature inside the kiln.

[0005] While the aforementioned existing technologies have improved the secondary air temperature to some extent, this structure is an external heat exchange mode with limited heat exchange efficiency, and still requires separate cooling equipment to process the calcined coke, failing to achieve integration of cooling and waste heat recovery. Based on these reasons, we propose a rotary kiln system for the stepped recovery of waste heat from petroleum coke calcination. Summary of the Invention

[0006] One object of the present invention is to provide a rotary kiln system for the stepped recovery of waste heat from petroleum coke calcination, comprising a kiln body, wherein the kiln body is provided with a preheating zone and a calcination zone in sequence, and a cooling zone is provided between the calcination zone and the kiln head. The cooling zone includes a primary cooling heat exchange section and a secondary cooling heat exchange section arranged in sequence toward the kiln head. The primary cooling heat exchange section is used to preheat the secondary air, and the secondary cooling heat exchange section is used to cool the calcined coke and recover heat energy.

[0007] Furthermore, the kiln body refractory layer of the primary cooling and heat exchange section is provided with heat exchange tubes. The heat exchange tubes extend spirally along the kiln body axis. One end of the heat exchange tube is connected to a blower, and the other end passes through the kiln body lining and is connected to a secondary air nozzle.

[0008] Furthermore, the inner cylinder of the kiln in the secondary cooling heat exchange section tapers in a cone shape towards the kiln head, forming a gradually narrowing flow channel.

[0009] Furthermore, the inner wall of the kiln body in the secondary cooling heat exchange section is provided with an annular finned cooler, and the kiln head cover of the kiln body is provided with a rotary joint. The annular finned cooler is connected to the external heat exchange station through the rotary joint.

[0010] Furthermore, it also includes a PLC controller. The kiln head of the kiln body is connected to a feeding chute. An infrared thermometer and a water mist nozzle are installed above the feeding chute. The water mist nozzle is equipped with a solenoid valve. The PLC controller is electrically connected to the infrared thermometer and the solenoid valve respectively.

[0011] Furthermore, the annular finned cooler includes a first annular finned cooler and a second annular finned cooler arranged sequentially toward the kiln head. The rotary joint is a dual-medium rotary joint. The coolant in the first annular finned cooler is heat transfer oil, and the coolant in the second annular finned cooler is demineralized water.

[0012] The present invention has the following beneficial effects: 1. This invention provides a rotary kiln system for the stepped recovery of waste heat from petroleum coke calcination. A cooling zone is set inside the rotary kiln cylinder. The secondary air is preheated to ≥350℃ by utilizing the sensible heat of the calcined coke in the primary cooling heat exchange section. The secondary cooling heat exchange section recovers heat in a stepped manner through a dual medium of heat transfer oil and demineralized water. The heat absorbed by the heat transfer oil can be directly connected to the carbon plant's molding heat transfer oil system, and the heat absorbed by the demineralized water can be used for heating in the plant's production and living areas. The overall heat recovery rate is significantly improved, and the waste of sensible heat and the overall energy consumption are significantly reduced.

[0013] 2. This invention integrates the cooling belt into the rotary kiln body, eliminating the traditional "large kiln-small kiln" separation structure and separate cooling equipment, thus reducing the equipment footprint and investment costs. Through the coordinated operation of the PLC controller, dual-band infrared thermometer and water mist nozzle, the temperature of the calcined coke outlet is monitored in real time. When the temperature is ≥120℃, the spray is automatically activated to fine-tune the cooling, ensuring that the discharge temperature is stable and meets the standard, further improving the reliability and adaptability of the system operation. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the rotary kiln system for the stepped recovery of waste heat from petroleum coke calcination in this invention.

[0015] Figure 2This is a schematic diagram of the internal structure of the cooling zone of the rotary kiln cylinder in this invention.

[0016] Figure 3 yes Figure 1 A magnified schematic diagram of the structure at point A in the middle.

[0017] Figure 4 yes Figure 2 A magnified schematic diagram of the structure at point B in the middle.

[0018] In the diagram: 100, kiln body; 101, kiln head hood; 102, secondary air nozzle; 110, preheating zone; 120, calcination zone; 130, cooling zone; 131, primary cooling heat exchange section; 132, secondary cooling heat exchange section; 140, blower; 141, heat exchange tube; 150, first annular finned cooler; 151, second annular finned cooler; 160, rotary joint; 170, material chute; 171, thermometer; 172, water mist nozzle. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0020] Reference Figure 1 and Figure 2 This invention discloses a rotary kiln system for stepped recovery of waste heat from petroleum coke calcination, comprising a rotary kiln body (hereinafter referred to as kiln body 100), which is divided along its axial direction from the kiln tail to the kiln head into a preheating zone 110, a calcination zone 120, and a cooling zone 130. The preheating zone 110 is 8-15m long and is used for petroleum coke dehydration and volatile matter extraction. The calcination zone 120 is 10-15m long and is used for coke calcination. The cooling zone 130 is 10-15m long and is used for cooling the calcined coke and recovering waste heat.

[0021] The cooling zone 130 is provided with a primary cooling heat exchange section 131 and a secondary cooling heat exchange section 132 in sequence along the axial direction towards the kiln head. The primary cooling heat exchange section 131 is used to preheat the secondary air, and the secondary cooling heat exchange section 132 is used to cool the calcined coke and recover heat energy.

[0022] The primary cooling heat exchange section 131 has heat exchange tubes 141 embedded in the refractory material layer of the kiln body 100. The heat exchange tubes 141 extend spirally along the axial direction of the kiln body 100, and are made of 310S stainless steel. A single kiln is equipped with 12-16 sets, each set with a tube length of 8-10m and a tube diameter of Φ130×3.5mm. One end of the heat exchange tube 141 is connected to the variable frequency blower 140 via a flange of the kiln body 100 (see reference). Figure 3The other end passes through the lining of the kiln body 100 and connects to the secondary air nozzle 102. Two rows of secondary air nozzles 102 are installed on the kiln body 100, one for use and one for backup. They are switched when blocked or burned out. The temperature of the kiln body 100 is used to raise the temperature of the secondary air, so that the preheating temperature of the secondary air is ≥350℃.

[0023] Commercially available models can be selected for the blower, such as the SR150 Roots blower, which is suitable for the operating conditions of a 250,000-ton petroleum coke calcination system. This model has a rated air volume of 60m³ / h. 3 With a rated pressure of 230 kPa and a speed of [unspecified unit] / min, the equipment is equipped with a 110 kW high-efficiency energy-saving motor. The motor has an IP55 protection rating and an F-class insulation rating, and can withstand the high-temperature dust environment at the kiln head. The equipment supports 0-100% frequency conversion speed regulation, which can adjust the air volume in real time according to the secondary air demand. It forms a stable fit with the 310S stainless steel heat exchange tube 141 and the secondary air nozzle 102, ensuring that the secondary air preheating temperature can stably reach ≥350℃.

[0024] The inner cylinder of the kiln body 100 in the secondary cooling heat exchange section 132 tapers in a conical shape along the axial direction towards the kiln head, forming a gradually narrowing flow channel. The end 1-2m near the kiln head is a straight section. Circumferentially arranged annular finned coolers are installed on the inner wall of the kiln body 100. The annular finned coolers are made of high-temperature resistant alloy steel. The annular finned coolers are connected to the external heat exchange station through a rotary joint 160. The rotary joint 160 is fixed to the kiln head cover 101. The cooling medium is introduced into the annular finned cooler through the rotary joint 160 located at the kiln head, flows through the secondary cooling heat exchange section 132, and then returns to the rotary joint 160 for outlet. The flow direction of the cooling medium is opposite to the flow direction of the material.

[0025] In a preferred embodiment, the annular finned cooler includes a first annular finned cooler 150 and a second annular finned cooler 151 arranged sequentially toward the kiln head. The rotary joint 160 is a dual-medium rotary joint. The coolant in the first annular finned cooler 150 is heat transfer oil, and the first annular finned cooler 150 forms an oil circuit circulation with the carbon plant molding heat transfer oil system through the rotary joint 160. The coolant in the second annular finned cooler 151 is demineralized water, and the second annular finned cooler 151 is connected to the external water supply pipeline and return water pipeline through the rotary joint 160.

[0026] In a preferred embodiment, refer to Figure 4The kiln head is equipped with a temperature control mechanism, including a PLC controller, a dual-band infrared thermometer 171, and a water mist nozzle 172. The water mist nozzle is equipped with a solenoid valve. The kiln head of the kiln body 100 is connected to a feeding chute 170. The thermometer 171 and the water mist nozzle 172 are installed 500mm above the feeding chute 170. The thermometer 171 and the solenoid valve are electrically connected to the PLC controller. The dual-band infrared thermometer 171 is used to monitor the temperature of the calcined coke in real time. The water mist nozzle 172 is connected to an external water supply pipeline through a pipeline. When the temperature of the calcined coke is ≥120℃, the PLC controller automatically opens the solenoid valve and connects the water mist nozzle 172 to spray and cool the calcined coke.

[0027] The commercially available S7-1500 series PLC controller can be selected, suitable for the temperature closed-loop control and equipment linkage requirements of the petroleum coke calcination waste heat recovery system. This series of PLC controllers can stably connect to the analog signals of the dual-band infrared thermometer 171 and solenoid valves, meeting the needs of multi-device collaborative control. It has an IP20 protection rating, and with the control cabinet's IP54 protection, its electromagnetic interference resistance meets the EN 61131-2 standard, fully adapting to the continuous operation requirements of a 250,000-ton rotary kiln system.

[0028] When this petroleum coke calcination waste heat recovery rotary kiln system is in use: After the raw materials enter the 8-15m long preheating zone 110, they are evenly distributed by rotating the kiln body 100°. Inside the kiln, the raw materials undergo dehydration and volatile matter release during preheating, laying the foundation for subsequent calcination processes. The treated raw materials then continuously move towards the kiln head.

[0029] The pretreated raw material enters the 10-15m long calcination belt 120. After being preheated by the primary cooling heat exchange section 131, the secondary air temperature is ≥350℃. It is then sent into the calcination belt 120 through the secondary air nozzle 102 to fully mix and burn with the fuel, maintaining the high-temperature environment required for calcination and ensuring that the petroleum coke is fully calcined.

[0030] After calcination, the high-temperature coke enters the primary cooling heat exchange section 131 of the cooling zone 130. The spiral heat exchange tube 141 inside the kiln body 100 uses the high temperature of the coke to heat the ambient temperature air supplied by the blower 140. The heated air is then directly introduced into the calcination zone 120 as secondary air, realizing the recycling of heat.

[0031] The calcined coke continues to move towards the kiln head and enters the gradually narrowing flow channel of the secondary cooling heat exchange section 132, where the flow velocity is optimized to improve heat exchange efficiency. The heat transfer oil in the first annular finned cooler 150 exchanges heat with the calcined coke, and after absorbing heat, it is introduced into the carbon plant's molding heat transfer oil system for recycling. Subsequently, the calcined coke exchanges heat with the demineralized water in the second annular finned cooler 151 for further cooling, and the heat absorbed by the demineralized water can be used in other production processes.

[0032] After undergoing secondary cooling, the calcined coke enters the feeding chute 170, where a dual-band infrared thermometer 171 monitors its temperature in real time. When the temperature reaches ≥120℃, the PLC controller responds quickly and automatically activates the water mist nozzles 172 to spray and cool the coke, ensuring that it is discharged from the kiln body 100 after reaching the required temperature.

[0033] Example 1: Retrofitting a 250,000-ton-class petroleum coke rotary kiln system The original petroleum coke rotary kiln system of a certain carbon plant was a conventional "large kiln-small kiln" separation structure. The kiln body was 100mm in diameter and 2.8m in length. Before the renovation, the secondary air temperature was 20℃, the actual coke yield after calcination was 68%, and the cooling water consumption was 5m³ / h. 3 / h.

[0034] The following modifications are made to the kiln body 100: the small kiln system is eliminated, and the cooling function is integrated into the rotary kiln body. A 12m preheating zone 110, a 12m calcination zone 120, and a 12m cooling zone 130 are sequentially installed along the axial direction. The primary cooling heat exchange section 131 of the cooling zone 130 contains 14 sets of 310S stainless steel heat exchange tubes 141, each set being 9m long and Φ130×3.5mm in diameter, connected to a variable frequency blower 140 and secondary air nozzles 102. Two rows, one in use and one on standby; the annular finned cooler of the secondary cooling heat exchange section 132 has a total heat exchange area of ​​85㎡, the inner cylinder of the kiln body 100 is tapered and narrowed, and the end 1.5m is a straight section. The cooling medium includes front-end heat transfer oil and rear-end demineralized water, which exchange heat with the material in countercurrent flow; a dual-band infrared thermometer 171 and a water mist nozzle 172 are installed 500mm above the kiln head discharge chute 170, and a PLC controller is provided; an automated control system is added, including detection instruments and safety interlock devices.

[0035] Post-modification operational results: Secondary air temperature reached 415℃, fuel consumption decreased by 15.7%; the temperature of the heat transfer oil after heat exchange reached 310℃, capable of replacing 60% of the boiler load; the actual yield of calcined coke increased to 72%, resulting in an annual increase in benefits of 4.2 million yuan; cooling water consumption decreased to 0.5m³. 3 / h, saving more than 90% of water, and producing no dust or sludge.

[0036] 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 within the protection scope of the present invention.

Claims

1. A rotary kiln system for stepped recovery of waste heat from petroleum coke calcination, comprising a kiln body (100), wherein the kiln body (100) is sequentially provided with a preheating zone (110) and a calcination zone (120), characterized in that, The kiln body (100) between the calcination zone (120) and the kiln head is provided with a cooling zone (130). The cooling zone (130) includes a primary cooling heat exchange section (131) and a secondary cooling heat exchange section (132) arranged sequentially toward the kiln head. The primary cooling heat exchange section (131) is used to preheat the secondary air. The secondary cooling heat exchange section (132) is used to cool the calcined coke and recover heat energy. The inner wall of the kiln body (100) of the secondary cooling heat exchange section (132) is provided with an annular finned cooler. The kiln head cover (101) of the kiln body (100) is provided with a rotary joint (160). The annular finned cooler is connected to the external heat exchange station through the rotary joint (160).

2. The rotary kiln system for stepped recovery of waste heat from petroleum coke calcination as described in claim 1, characterized in that, The kiln body (100) refractory layer of the primary cooling heat exchange section (131) is provided with heat exchange tubes (141). The heat exchange tubes (141) extend spirally along the kiln body (100) axis. One end of the heat exchange tubes (141) is connected to a blower (140), and the other end passes through the kiln body (100) lining and is connected to a secondary air nozzle (102).

3. The rotary kiln system for stepped recovery of waste heat from petroleum coke calcination as described in claim 1, characterized in that, The inner cylinder of the kiln body (100) in the secondary cooling heat exchange section (132) tapers towards the kiln head in a conical shape, forming a gradually narrowing flow channel.

4. The rotary kiln system for stepped recovery of waste heat from petroleum coke calcination as described in claim 1, characterized in that, It also includes a PLC controller. The kiln head of the kiln body (100) is connected to a feeding chute (170). An infrared thermometer (171) and a water mist nozzle (172) are provided above the feeding chute (170). The water mist nozzle (172) is equipped with a solenoid valve. The PLC controller is electrically connected to the infrared thermometer (171) and the solenoid valve respectively.

5. The rotary kiln system for stepped recovery of waste heat from petroleum coke calcination as described in claim 1, characterized in that, The annular finned cooler includes a first annular finned cooler (150) and a second annular finned cooler (151) arranged sequentially toward the kiln head. The rotary joint (160) is a dual-medium rotary joint. The coolant in the first annular finned cooler (150) is heat transfer oil, and the coolant in the second annular finned cooler (151) is demineralized water.

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