A system for the injection and combustion of biochar particles in a marine boiler

Abstract

The present application discloses a kind of for ship boiler biochar particle injection combustion system, fuel preparation unit is made with biochar material biochar particle;Fuel storage unit is maintained by inert gas in bunker oxygen concentration is lower than 3% to ensure safety;Fuel feeding unit is used to form fuel and be transported into injection unit with biochar particle;Injection unit is injected into combustion and energy conversion unit with fuel injection, and is equipped with pressure monitoring and pressure relief loop to stabilize system safe operation;Combustion and energy conversion unit, including burner for receiving fuel, and is sent into boiler through burner nozzle and burns, the heat released by combustion is absorbed by boiler heating surface to generate steam for heating, and by adjusting secondary air volume or enabling pressure relief outlet, furnace pressure is maintained in safe range;Ash handling unit, fly ash in ash bin is centrally processed after electrostatic precipitation of boiler flue gas, purified flue gas is pumped by induced draft fan and meets the emission standard after tail gas treatment, realize efficient and environmentally friendly operation.

Description

Technical Field

[0001] This invention relates to the field of marine propulsion system technology, and more specifically, to a biochar pellet injection combustion system for marine boilers. Background Technology

[0002] Traditional oil-fired marine boilers are commonly found on bulk carriers, tankers, and container ships, typically serving as auxiliary boilers for tasks such as domestic heating, fuel line heat tracing, and driving auxiliary machinery. These boilers use heavy oil as their primary fuel, a residue from crude oil refining, characterized by high viscosity, high sulfur content, and numerous impurities. Before use, the heavy oil undergoes a series of treatments including preheating, purification, and atomization to ensure complete combustion. Pressure atomizing or rotary cup burners are employed, the core of which is to break the liquid fuel oil into extremely fine atomized droplets, which are then mixed with air for combustion. However, burning heavy oil produces large amounts of sulfur oxides (SO₄). x Heavy fuel oil combustion produces carbon deposits and soot, requiring regular cleaning. It is subject to strict regulations by the International Maritime Organization (IMO) regarding particulate matter (PM) and other pollutants.

[0003] Marine gas-fired boilers primarily refer to boilers used on LNG (liquefied natural gas) carriers. Their fuel source is mainly gaseous natural gas (BOG) formed through evaporation. Because LNG naturally evaporates in cryogenic storage tanks at -162°C due to external heat penetration, if not promptly discharged, the pressure inside the tank will rise. Therefore, a core design feature of LNG carriers is the collection of this evaporated BOG as the primary fuel for the boilers. However, natural gas is highly flammable and explosive, requiring extremely stringent safety systems for boiler compartment ventilation, gas detection, and pre-ignition purging.

[0004] Previous research in this invention has revealed that biochar, as a renewable resource, possesses low carbon emissions and environmentally friendly characteristics; however, there is currently no mature technical solution for its application in marine boilers. Furthermore, addressing the shortcomings of traditional oil-fired auxiliary boilers and LNG-fired marine boilers, this invention considers introducing pulverized coal injection technology, already maturely applied in thermal power plants, to explore whether it can replace traditional oil-fired auxiliary boilers and LNG-fired marine boilers.

[0005] While existing pulverized coal injection technology for power plants is mature, its design is geared towards land-based fixed equipment and does not take into account the turbulence, vibration, space constraints, and fuel storage stability requirements of ships. Direct application of this technology can lead to problems such as blockage of delivery pipelines and coking of burners. Furthermore, the traditional pulverized coal particle size (60-90μm) is difficult to achieve rapid combustion in the compact combustion chamber of ship boilers, resulting in low combustion efficiency. The sulfur and chlorine components in the flue gas can also corrode boiler tubes under high-temperature conditions. In addition, the differences in physicochemical properties between biochar particles and pulverized coal (such as density, flowability, and ignition point) further limit the applicability of existing technologies. Therefore, there is an urgent need to develop a high-efficiency biochar particle combustion technology suitable for marine environments. Summary of the Invention

[0006] The purpose of this invention is to overcome the above-mentioned defects in the prior art and provide a biochar pellet injection and combustion system for ship boilers.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows: A biochar pellet injection and combustion system for marine boilers includes a fuel preparation unit, a fuel storage unit, a fuel feeding unit, an injection unit, and a combustion and energy conversion unit. The fuel preparation unit is used to prepare biochar particles with a particle size of 15-25 μm; A fuel storage unit includes a biochar pellet storage bin and an inert gas device connected together; the biochar pellet storage bin is used to receive biochar pellets prepared by the fuel preparation unit; the inert gas device is used to introduce inert gas into the biochar pellet storage bin to control the oxygen concentration in the biochar pellet storage bin to <3% and maintain a constant temperature environment of 20-30℃. The fuel feeding unit includes a feeding bin, a conveying device, and a mixer; the outlet of the biochar pellet storage bin is connected to the inlet of the feeding bin, and the outlet of the feeding bin is connected to the inlet of the mixer, so that the biochar pellets in the biochar pellet storage bin are fed into the mixer through the feeding bin; the conveying device is connected to the mixer and is used to form fuel from the biochar pellets in the mixer and convey it to the injection unit; The injection unit includes an injection device; the input end of the injection device is connected to the output end of the mixer to receive fuel and inject the fuel into the combustion and energy conversion unit. The combustion and energy conversion unit includes a burner; the burner includes a first input terminal connected to an injection device for receiving the fuel and sending it into the boiler for combustion through the burner nozzle, wherein the heat released by combustion is absorbed by the boiler heating surface to generate steam for heating.

[0008] Optionally, in the fuel feeding unit, the conveying device is a primary air fan, and the mixer also has an air inlet connected to the primary air fan. The primary air provided by the primary air fan mixes with the biochar particles in the mixer to form a gas-solid two-phase flow as fuel and is conveyed to the injection unit. The pressure of the primary air is 0.15-0.35 MPa, and the wind speed is 18-28 m / s. The injection speed of the burner nozzle is 120-150 m / s.

[0009] Optionally, the injection device is provided with a third input terminal, a first output terminal, and a second output terminal. The third input terminal is connected to the output terminal of the mixer, the first output terminal is connected to the air preheater, and the second output terminal is connected to the first input terminal of the burner. The injection device is equipped with a pressure sensor for real-time monitoring of the gas pressure of the received gas-solid two-phase flow. When the detected pressure is ≤0.35MPa, the first output terminal is closed and the second output terminal is opened to inject the gas-solid two-phase flow in the injection device into the burner. When the detected pressure is >0.35MPa, the first output terminal is opened and the second output terminal is closed to transport part of the gas-solid two-phase flow to the storage chamber of the air preheater to achieve depressurization until the detected pressure is 0.12~0.2MPa. At this time, the first output terminal is closed and the second output terminal is opened to inject the remaining gas-solid two-phase flow in the injection device into the burner.

[0010] Optionally, in the combustion and energy conversion unit, the first input end of the burner is connected to the second output end of the injection device for receiving the gas-solid two-phase flow. The burner also includes a second input end, which is connected to a secondary air fan via an air preheater. The secondary air provided by the secondary air fan is preheated to 180-250°C by the air preheater and then mixed with the gas-solid two-phase flow through the second input end. The resulting mixed gas is then sent into the boiler through the burner nozzle for combustion. The heat released by combustion is absorbed by the boiler's heating surface to generate steam for heating.

[0011] Optionally, the burner is equipped with a pressure sensor to monitor the internal pressure of the burner in real time. When the internal pressure is less than the minimum reaction pressure, the mixed gas pressure relief outlet on the burner is closed, the burner nozzle is opened, and the air supply of the secondary air fan is increased until the detected pressure is -30Pa to +10Pa. When the internal pressure exceeds the set safety value, the mixed gas pressure relief outlet on the burner is opened, and the burner nozzle is closed to deliver part of the mixed gas to the gas storage tank until the detected pressure is 0.12MPa, at which point the mixed gas pressure relief outlet is closed. The burner nozzle is opened to allow the remaining mixed gas in the burner to be fed into the boiler for combustion. When the internal pressure is between the minimum reaction pressure and the set safety value, the mixed gas pressure relief outlet on the burner is closed, and the burner nozzle is opened to allow the resulting mixed gas to be fed into the boiler for combustion. The combustion temperature is 950-1150°C, and the heat released by combustion is absorbed by the boiler heating surface to generate steam for heating. The set safety value is 80 Pa, and the minimum reaction pressure is -80 Pa.

[0012] Optionally, in the fuel feeding unit, the conveying device is a heavy oil pump, and the mixer also has an oil inlet connected to the heavy oil pump. The heavy oil provided by the heavy oil pump is mixed with the biochar particles in the mixer to form a mixture as fuel and is conveyed to the injection unit. The heavy oil is selected from at least one of RF20, RF80, RF180, RF380 to RF500. The biochar particles in the mixture have a mass percentage content of 10%-50%.

[0013] Optionally, the fuel preparation unit includes a ball mill and a vibrating screen. The discharge port of the ball mill is connected to the feed port of the vibrating screen through a pipe. The ball mill is used to process the biochar material through ball milling and sieving to obtain biochar particles with a particle size of 15-25 μm.

[0014] Optionally, the preparation method of the biochar material includes the following steps: crushing the biomass material and then pyrolyzing it at a temperature of 400-600℃ for 2-4 hours, followed by freezing at -10℃ for 2-3 hours, resulting in a biochar material with a fixed carbon content ≥85%, an ash melting point ≥1350℃, and a moisture content ≤3%; wherein the biomass material is selected from one or more of straw, wood, and rice husk, and has a moisture content of 10%-20%.

[0015] Optionally, in the fuel storage unit, the biochar pellet storage bin is located below the vibrating screen and is used to receive the biochar pellets; the biochar pellet storage bin is elongated or horizontal; the inert gas device includes a high-pressure gas pipe, and an inert gas source is connected to the high-pressure gas pipe. The inert gas source is connected to the biochar pellet storage bin via a pipeline from the outlet of the high-pressure gas pipe, and is used to introduce inert gas at a pressure of 0.3-0.6 MPa and a flow rate of 10-25 L / min into the biochar pellet storage bin. The inert gas is at least one of CO2 and N2.

[0016] Optionally, the system further includes an ash treatment unit connected to the boiler's exhaust port. The high-temperature flue gas generated by the boiler combustion carries fly ash through a soot blowing device and enters an electrostatic precipitator for dust removal via a gas storage tank, resulting in dust-removed flue gas and fly ash. The collected fly ash is transported to an ash silo for temporary storage. The ash silo is designed with a dust-proof wet ash discharge port for centralized treatment at the port. The dust-removed flue gas is then drawn into the exhaust gas treatment unit by a corrosion-resistant induced draft fan with a total pressure of 2-6 kPa, and finally discharged through the ship's chimney in compliance with emission standards. The operation of the induced draft fan is linked to the boiler load, providing stable power for the entire flue gas system.

[0017] Optionally, the system also includes a safety monitoring and linkage control system, used to detect and coordinate the air distribution of the inert gas device, the primary air fan and the secondary air fan, and to link with the ship attitude sensor so that when the ship's tilt angle exceeds a set threshold, the operating parameters can be automatically adjusted.

[0018] Optionally, the spraying device has a dual-fluid atomizing nozzle, an atomization pressure of 0.8-1.2 MPa, and a spray volume adjustment range of 500-1000 kg / h.

[0019] Optionally, the ship boiler is selected from one or more of the following: ocean-going vessel boilers, inland waterway vessel boilers, and fishing vessel boilers.

[0020] Implementing the embodiments of the present invention will have the following beneficial effects: This invention addresses the compatibility issues of land-based pulverized coal injection technology in marine environments by designing a novel biochar pellet injection combustion system for marine boilers. It involves preparing 15-25μm biochar pellets through biomass pyrolysis, using these pellets to replace traditional fuel oil as the combustion feedstock for marine boilers. Compared to traditional pulverized coal, biochar pellets offer advantages such as smaller particle size, larger specific surface area, softer texture, and carbon neutrality. A fuel storage unit maintains an oxygen concentration below 3% within the storage silo using inert gas to ensure safety. The fuel feeding unit utilizes a primary air fan to dispense the biochar pellets into the mixer. The system forms a gas-solid two-phase flow. The injection unit injects the two-phase flow into the burner and is equipped with pressure monitoring and pressure relief circuits to ensure stable and safe system operation. In the combustion and energy conversion unit, the two-phase flow mixes with the secondary air from the air preheater in the burner for combustion. The heat released by combustion is absorbed by the boiler heating surface to generate steam for heating. The furnace pressure is maintained within a safe range by adjusting the secondary air volume or activating the pressure relief outlet. In the ash treatment unit, the boiler flue gas is treated by electrostatic precipitator, and the fly ash is collected in the ash bin for centralized treatment. The purified flue gas is drawn in by the induced draft fan and treated to meet emission standards, achieving efficient and environmentally friendly operation.

[0021] This invention achieves higher combustion efficiency and burnout rate by combining the injection unit with staged air distribution technology. The system integrates shock-absorbing brackets and a modular design to adapt to space constraints and turbulence on board. Marine boilers account for 5%-15% of a ship's total fuel consumption. This system uses biochar pellets to replace traditional fuel oil as the combustion fuel for marine boilers, significantly reducing carbon emissions and providing an economically feasible solution for the low-carbon transformation of the shipping industry. Attached Figure Description

[0022] Figure 1 This is a process flow diagram of the biochar pellet injection and combustion system for marine boilers according to the present invention. Detailed Implementation

[0023] The present invention will be further described below with reference to specific embodiments, but this does not limit the present invention in any way.

[0024] This invention reveals that the thermal power systems of onshore power plant boilers are typically designed to operate in a stable, spacious terrestrial environment with moderate loads, ample space, and no need for frequent start-ups and shutdowns or consideration of high-salt, high-humidity corrosion issues. In contrast, the marine operating environment is characterized by significant turbulence, high salt spray corrosion, compact space, frequent load changes, and strict compliance with International Maritime Organization (IMO) emission standards. Therefore, traditional thermal power boiler processes are ill-suited to the unique operating conditions of ships, exhibiting issues such as loose system layout, weak anti-sway capabilities, insufficient corrosion prevention measures, and slow start-up and shutdown response.

[0025] Therefore, this invention utilizes biochar pellets to replace traditional fuel oil as the combustion feedstock for marine boilers, and discloses a biochar pellet injection and combustion system for marine boilers, comprising a fuel preparation unit, a fuel storage unit, a fuel feeding unit, an injection unit, and a combustion and energy conversion unit: specifically including: The fuel preparation unit is used to prepare biochar particles with a particle size of 15-25μm to create powdered fuels with a high specific surface area, laying the physical basis for efficient suspension combustion.

[0026] The fuel storage unit includes a biochar pellet storage silo and an inert gas device connected to each other. The biochar pellet storage silo is used to receive biochar pellets prepared by the fuel preparation unit. The inert gas device is used to introduce inert gas into the biochar pellet storage silo to control the oxygen concentration in the biochar pellet storage silo to <3% and maintain a constant temperature environment of 20-30℃, which greatly reduces the risk of spontaneous combustion or explosion in special environments.

[0027] The fuel feeding unit includes a feeding bin, a conveying device, and a mixer; the outlet of the biochar pellet storage bin is connected to the inlet of the feeding bin, and the outlet of the feeding bin is connected to the inlet of the mixer, so that the biochar pellets in the biochar pellet storage bin are sent to the mixer through the feeding bin; the conveying device is connected to the mixer and is used to form the biochar pellets in the mixer into fuel and convey them to the injection unit.

[0028] The injection unit includes an injection device; the input end of the injection device is connected to the output end of the mixer to receive fuel and inject the fuel into the combustion and energy conversion unit.

[0029] The combustion and energy conversion unit includes a burner; the burner includes a first input end, which is connected to an injection device for receiving fuel and sending it into the boiler for combustion through the burner nozzle. The heat released by the combustion is absorbed by the boiler heating surface to generate steam for heating.

[0030] In one specific embodiment, in the fuel feeding unit, the conveying device is a primary air fan, and the mixer also has an air inlet connected to the primary air fan. The primary air provided by the primary air fan mixes with the biochar particles in the mixer to form a gas-solid two-phase flow as fuel and is conveyed to the injection unit. The pressure of the primary air is 0.15-0.35MPa, and the wind speed is 18-28m / s to ensure stable delivery when the ship is rocking. The injection speed of the burner nozzle is 120-150m / s.

[0031] In one specific embodiment, the injection device is provided with a third input terminal, a first output terminal, and a second output terminal. The third input terminal is connected to the output terminal of the mixer, the first output terminal is connected to the air preheater, and the second output terminal is connected to the first input terminal of the burner. The injection device is equipped with a pressure sensor for real-time monitoring of the gas pressure of the received gas-solid two-phase flow. When the detected pressure is ≤0.35MPa, the first output terminal is closed and the second output terminal is opened to inject the gas-solid two-phase flow in the injection device into the burner. When the detected pressure is >0.35MPa, the first output terminal is opened and the second output terminal is closed to transport part of the gas-solid two-phase flow to the storage chamber of the air preheater to achieve depressurization until the detected pressure is 0.12~0.2MPa. At this time, the first output terminal is closed and the second output terminal is opened to inject the remaining gas-solid two-phase flow in the injection device into the burner.

[0032] In one specific embodiment, in the combustion and energy conversion unit, the first input end of the burner is connected to the second output end of the injection device to receive the gas-solid two-phase flow. The burner also includes a second input end, which is connected to a secondary air fan via an air preheater. The secondary air provided by the secondary air fan is preheated to 180-250°C by the air preheater and then mixed with the gas-solid two-phase flow through the second input end. The resulting mixed gas is then sent into the boiler through the burner nozzle for combustion. The heat released by combustion is absorbed by the boiler's heating surface to generate steam for heating. This burner, by organizing a high-intensity swirling flow field, ensures that biochar particles can still achieve efficient and stable suspension combustion within the compact furnace of a ship's boiler, even under ship tilt conditions of ±15°.

[0033] In one specific embodiment, a pressure sensor is installed on the burner to monitor the internal pressure of the burner in real time. When the internal pressure is less than the minimum reaction pressure, the mixed gas pressure relief outlet on the burner is closed, the burner nozzle is opened, and the air supply of the secondary air fan is increased until the detected pressure is -30Pa to +10Pa. After the secondary air is introduced, the damper is precisely adjusted by servo control to maintain the excess air coefficient between 1.15 and 1.25. The typical secondary air volume accounts for 70-85%, and the furnace pressure is strictly stabilized at a slightly negative pressure state of -30Pa to +10Pa through the coordinated control of the induced draft fan and the forced draft fan. This is crucial for preventing flue gas leakage in a swaying environment. When the internal pressure exceeds the set safety value, the valve is opened. The mixed gas pressure relief outlet on the burner is closed, and the burner nozzle is closed to deliver part of the mixed gas to the gas storage tank until the detected pressure is 0.12 MPa. At this point, the mixed gas pressure relief outlet is closed, and the burner nozzle is opened to send the remaining mixed gas in the burner into the boiler for combustion. When the internal pressure is between the minimum reaction pressure and the set safety value, the mixed gas pressure relief outlet on the burner is closed, and the burner nozzle is opened to send the resulting mixed gas into the boiler for combustion. The combustion temperature is 950-1150°C, and the heat released by combustion is absorbed by the boiler heating surface to generate steam for heating. The set safety value is 80 Pa, and the minimum reaction pressure is -80 Pa.

[0034] In one specific embodiment, the fuel feeding unit includes a heavy oil pump as the conveying device, and the mixer also has an oil inlet connected to the heavy oil pump. The heavy oil supplied by the heavy oil pump is mixed with the biochar particles in the mixer to form a mixture as fuel and is then conveyed to the injection unit. The heavy oil is selected from at least one of RF20, RF80, RF180, RF380 to RF500. The biochar particles in the mixture have a mass percentage content of 10%-50%.

[0035] In one specific embodiment, the fuel preparation unit includes a ball mill and a vibrating screen. The discharge port of the ball mill is connected to the feed port of the vibrating screen through a pipe. The ball mill is used to process the biochar material through ball milling and sieving to obtain biochar particles with a particle size of 15-25 μm.

[0036] In one specific embodiment, the preparation method of biochar material includes the following steps: crushing biomass material and then pyrolyzing it at a temperature of 400-600℃ (preferably 550℃) for 2-4 hours (preferably 3 hours), followed by freezing at -10℃ for 2-3 hours, resulting in biochar material with fixed carbon ≥85%, ash melting point ≥1350℃, and moisture content ≤3%.

[0037] In one specific embodiment, the biomass material is selected from one or more of straw, wood, and rice husks, with a moisture content of 10%-20%.

[0038] In one specific embodiment, in the fuel storage unit, the biochar pellet storage bin is located below the vibrating screen and is used to receive biochar pellets; the biochar pellet storage bin is elongated or horizontally designed; the inert gas device includes a high-pressure gas pipe, and an inert gas source is connected to the high-pressure gas pipe. The inert gas source is connected to the biochar pellet storage bin via a pipeline through the outlet of the high-pressure gas pipe, and is used to introduce inert gas with a pressure of 0.3-0.6 MPa and a flow rate of 10-25 L / min into the biochar pellet storage bin. The inert gas is at least one of CO2 and N2.

[0039] In one specific embodiment, the system further includes an ash treatment unit connected to the boiler's exhaust port. The high-temperature flue gas generated by boiler combustion carries fly ash through a soot blowing device and enters an electrostatic precipitator for dust removal via a gas storage tank, resulting in dust-removed flue gas and fly ash. The collected fly ash is transported to an ash silo for temporary storage. The ash silo is designed with a dust-proof wet ash discharge port for centralized treatment at the port. The dust-removed flue gas is then drawn into the exhaust gas treatment unit by a corrosion-resistant induced draft fan with a total pressure of 2-6 kPa, and finally discharged to the ship's chimney in compliance with emission standards. The operation of the induced draft fan is linked to the boiler load, providing stable power for the entire flue gas system.

[0040] In one specific embodiment, the electrostatic precipitator is further provided with an air inlet connected to the storage chamber of the air preheater, so as to transport the remaining gas in the storage chamber of the air preheater to the electrostatic precipitator.

[0041] In one specific embodiment, the system also includes a safety monitoring and linkage control system, which is used to detect and coordinate the delivery of inert gas devices, primary air fans and secondary air fans, and is linked with the ship attitude sensor to automatically adjust operating parameters when the ship's tilt angle exceeds a set threshold.

[0042] In one specific embodiment, the spraying unit of the present invention adopts a modular integrated design, which reduces the floor space compared with traditional systems. The spraying device has a dual-fluid atomizing nozzle, an atomization pressure of 0.8-1.2MPa, and a spraying volume adjustment range of 500-1000kg / h.

[0043] In one specific embodiment, the present invention employs a staged air distribution technology, reducing the primary air ratio to 25-30%, thereby suppressing the combustion of NO in ultrafine powder. x generate.

[0044] In one specific embodiment, the injection velocity of the burner nozzle is 120-150 m / s.

[0045] In one specific embodiment, the ship boiler is selected from one or more of the following: ocean-going vessel boilers, inland waterway vessel boilers, and fishing vessel boilers.

[0046] In one specific embodiment, the pipeline involved in the system of the present invention may be equipped with shock-absorbing supports to adapt to the ship's roll condition of ±30°.

[0047] In one specific embodiment, the present invention replaces the traditional fuel tank with a biochar pellet storage tank equipped with an inert gas device, effectively preventing the risk of spontaneous combustion and explosion of biochar pellets.

[0048] In one specific embodiment, the present invention replaces the original fuel pressurization and preheating unit. The primary air fan is responsible for providing the delivery power, and its air pressure and air volume need to be precisely calculated to overcome pipeline resistance and ensure the burner outlet flow rate. In addition, a classification society-certified fast-response backfire prevention device and an airlock can be installed in the pipeline to eliminate the safety hazard of flame backlash.

[0049] In one specific embodiment, the present invention requires the complete replacement of the original oil burner with a burner specifically designed for biochar pellets, achieving a shift from "atomized injection" to "pneumatic delivery." Structurally, the design can draw inspiration from the swirl or direct-flow burners used in thermal power plants. By organizing a reasonable airflow field, the biochar pellets are promoted to fully mix with the secondary air, forming a stable recirculation zone to ensure timely ignition and complete combustion of the biochar pellets. Given the strong abrasive effect of biochar pellets on materials, the burner nozzle can be made of wear-resistant ceramics or special alloys. Simultaneously, a high-power ignition burner (using diesel or natural gas) and combustion-supporting devices are required to maintain furnace temperature under low-load conditions and ensure flame stability. Since its ignition performance is generally inferior to coal, stable combustion design is particularly crucial.

[0050] In one specific embodiment, the present invention replaces the original compact furnace (such as a fire-tube boiler) with a water-tube boiler furnace that has sufficient suspended combustion space, ensuring that the biochar particles have enough residence time to achieve complete combustion, and rationally organizing the temperature and flow fields to avoid slagging and corrosion. The heating surfaces (including water-cooled walls, superheaters, economizers, etc.) need to be redesigned and arranged according to the flue gas and ash characteristics of biochar particle combustion, taking into account material selection and spacing optimization to prevent ash accumulation, wear, and corrosion.

[0051] Specifically, this invention provides an economical and feasible solution for a marine boiler biochar pellet fuel system, achieving efficient, stable, and low-emission operation within a limited space. It can adapt to the harsh environment of ships, has higher reliability and environmental compliance, and can effectively cope with ship-specific operating conditions such as turbulence, salt corrosion, and load fluctuations, thereby meeting both energy efficiency and environmental protection requirements and achieving a burnout rate of >98%. This not only expands the application scope of biochar materials in the field of marine power, but also provides key technical support for the shipping industry to achieve a low-carbon transformation.

[0052] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A biochar pellet injection and combustion system for marine boilers, characterized in that, It includes a fuel preparation unit, a fuel storage unit, a fuel feeding unit, an injection unit, and a combustion and energy conversion unit: The fuel preparation unit is used to prepare biochar particles with a particle size of 15-25 μm; A fuel storage unit includes a biochar pellet storage bin and an inert gas device connected together; the biochar pellet storage bin is used to receive biochar pellets prepared by the fuel preparation unit; the inert gas device is used to introduce inert gas into the biochar pellet storage bin to control the oxygen concentration in the biochar pellet storage bin to <3% and maintain a constant temperature environment of 20-30℃. The fuel feeding unit includes a feeding bin, a conveying device, and a mixer; the outlet of the biochar pellet storage bin is connected to the inlet of the feeding bin, and the outlet of the feeding bin is connected to the inlet of the mixer, so that the biochar pellets in the biochar pellet storage bin are fed to the mixer through the feeding bin; The conveying device is connected to the mixer and is used to form biochar particles in the mixer into fuel and convey them to the injection unit; The injection unit includes an injection device; the input end of the injection device is connected to the output end of the mixer to receive fuel and inject the fuel into the combustion and energy conversion unit. A combustion and energy conversion unit includes a burner; the burner includes a first input terminal, which is connected to an injection device for receiving the fuel and sending it into the boiler for combustion through the burner nozzle; the heat released by combustion is absorbed by the boiler heating surface to generate steam for heating. In the fuel feeding unit, the conveying device is a primary air fan, and the mixer also has an air inlet connected to the primary air fan. The primary air provided by the primary air fan mixes with the biochar particles in the mixer to form a gas-solid two-phase flow as fuel and is conveyed to the injection unit. The pressure of the primary air is 0.15-0.35 MPa, and the wind speed is 18-28 m / s. The injection speed of the burner nozzle is 120-150 m / s. The injection device is provided with a third input terminal, a first output terminal and a second output terminal. The third input terminal is connected to the output terminal of the mixer, the first output terminal is connected to the air preheater, and the second output terminal is connected to the first input terminal of the burner. The injection device is equipped with a pressure sensor to monitor the gas pressure of the received gas-solid two-phase flow in real time. When the detected pressure is ≤0.35MPa, the first output end is closed and the second output end is opened to inject the gas-solid two-phase flow in the injection device into the burner. When the detection pressure is >0.35MPa, the first output terminal is opened and the second output terminal is closed to deliver part of the gas-solid two-phase flow to the storage chamber of the air preheater to achieve depressurization until the detection pressure is 0.12~0.2MPa. At this time, the first output terminal is closed and the second output terminal is opened to inject the remaining gas-solid two-phase flow in the injection device into the burner. In the combustion and energy conversion unit, the first input end of the burner is connected to the second output end of the injection device to receive the gas-solid two-phase flow. The burner also includes a second input end, which is connected to a secondary air fan through an air preheater. The secondary air provided by the secondary air fan is preheated to 180-250°C by the air preheater and then mixed with the gas-solid two-phase flow through the second input end. The resulting mixed gas is then sent into the boiler through the burner nozzle for combustion. The heat released by combustion is absorbed by the boiler heating surface to generate steam for heating. The burner is equipped with a pressure sensor to monitor the internal pressure of the burner in real time. When the internal pressure is less than the minimum reaction pressure, the mixed gas pressure relief outlet on the burner is closed, the burner nozzle is opened, and the air supply of the secondary air fan is increased until the detected pressure is -30Pa to +10Pa. When the internal pressure exceeds the set safety value, the mixed gas pressure relief outlet on the burner is opened and the burner nozzle is closed to deliver part of the mixed gas to the gas storage tank until the detected pressure is 0.12MPa. At this time, the mixed gas pressure relief outlet is closed and the burner nozzle is opened to send the remaining mixed gas in the burner into the boiler for combustion. When the internal pressure is between the minimum reaction pressure and the set safety value, the mixed gas pressure relief outlet on the burner is closed, the burner nozzle is opened, and the obtained mixed gas is sent into the boiler for combustion through the burner nozzle. The combustion temperature is 950-1150°C, and the heat released by combustion is absorbed by the boiler heating surface to generate steam for heating. The set safety value is 80 Pa, and the minimum reaction pressure is -80 Pa.

2. The biochar pellet injection and combustion system for ship boilers according to claim 1, characterized in that, In the fuel feeding unit, the conveying device is a heavy oil pump, and the mixer also has an oil inlet connected to the heavy oil pump. The heavy oil supplied by the heavy oil pump is mixed with the biochar particles in the mixer to form a mixture as fuel and is then transported to the injection unit. The heavy oil is selected from at least one of RF20, RF80, RF180, RF380 to RF500. The biochar particles in the mixture have a mass percentage content of 10%-50%.

3. The biochar pellet injection and combustion system for ship boilers according to claim 1, characterized in that, The fuel preparation unit includes a ball mill and a vibrating screen. The discharge port of the ball mill is connected to the feed port of the vibrating screen through a pipe. It is used to process biochar material by ball milling and sieving to obtain biochar particles with a particle size of 15-25μm. The preparation method of the biochar material includes the following steps: crushing the biomass material and then pyrolyzing it at a temperature of 400-600℃ for 2-4 hours, followed by freezing at -10℃ for 2-3 hours, resulting in a biochar material with a fixed carbon content ≥85%, an ash melting point ≥1350℃, and a moisture content ≤3%; wherein the biomass material is selected from one or more of straw, wood, and rice husk, and has a moisture content of 10%-20%.

4. The biochar pellet injection and combustion system for marine boilers according to claim 3, characterized in that, In the fuel storage unit, the biochar pellet storage bin is located below the vibrating screen and is used to receive the biochar pellets; the biochar pellet storage bin is elongated or horizontal; the inert gas device includes a high-pressure gas pipe, and an inert gas source is connected to the high-pressure gas pipe. The inert gas source is connected to the biochar pellet storage bin via a pipeline through the outlet of the high-pressure gas pipe, and is used to introduce inert gas with a pressure of 0.3-0.6 MPa and a flow rate of 10-25 L / min into the biochar pellet storage bin. The inert gas is at least one of CO2 and N2.

5. The biochar pellet injection and combustion system for ship boilers according to claim 1, characterized in that, The system also includes an ash treatment unit, which is connected to the exhaust port of the boiler. The high-temperature flue gas generated by the boiler combustion carries fly ash through a soot blowing device and enters an electrostatic precipitator through a gas storage tank for dust removal, resulting in dust-removed flue gas and fly ash. The collected fly ash is transported to an ash silo for temporary storage. The ash silo is designed with a dust-proof wet ash discharge port to facilitate centralized processing at the port. The flue gas after dust removal is drawn into the exhaust gas treatment unit by a corrosion-resistant induced draft fan with a total pressure of 2-6 kPa, and finally discharged into the ship's chimney in compliance with emission standards. The operation of the induced draft fan is linked to the boiler load, providing stable power for the entire flue gas system.

6. The biochar pellet injection and combustion system for marine boilers according to claim 1, characterized in that, The system also includes a safety monitoring and linkage control system, which is used to detect and coordinate the air distribution device of the inert gas device, the primary air fan and the secondary air fan, and to link with the ship attitude sensor so that when the ship tilt angle exceeds the set threshold, the operating parameters can be automatically adjusted. The spraying device has a dual-fluid atomizing nozzle, an atomization pressure of 0.8-1.2MPa, and a spray volume adjustment range of 500-1000kg / h; The ship boiler is selected from one or more of the following: ocean-going vessel boilers, inland waterway vessel boilers, and fishing vessel boilers.

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