Operation Management and Daily Maintenance of Marine Incinerators

Operation Management and Daily Maintenance of Marine Incinerators

The incinerators manufactured by Deyuan Marine feature an operator interface designed with both user-friendliness and simplicity in mind. Compared to some incinerators of similar types, they are equipped with a practical sludge settling tank. This configuration enables continuous combustion without stopping the unit, significantly improving sludge treatment efficiency. Additionally, these incinerators are equipped with intelligent adjustment functions that automatically optimize the fuel supply rate and air pressure parameters based on fuel quality and furnace temperature. This not only accelerates the combustion rate but also effectively reduces the occurrence of sudden flameouts when burning sludge.

In terms of the "ash removal" program design, these incinerators also highlight their user-friendly advantages. During the ash cleaning process, dust does not disperse into the engine room but is directly discharged outside the ship via the flue gas fan, preventing pollution of the engine room environment. Moreover, activating this function when loading waste helps reduce the accumulation of harmful gases inside the furnace, further ensuring equipment operational safety and the health of operating personnel.

Basic Principles of Solid Waste Incineration Mode

Solid waste incineration is a systematic process, primarily divided into three core stages: waste processing, waste combustion, and ash removal. Each stage has specific operational requirements and precautions that must be strictly followed.

1. Waste Processing
The solid waste incinerated on this vessel mainly consists of oil-absorbent cotton yarn and paper-based waste. The incineration of plastics, metals, glass, and other unsuitable materials is strictly prohibited. During the waste processing stage, the following seven precautions must be emphasized to ensure safe and efficient incineration:

1.1 Hazardous liquids with a flash point below 60°C and other dangerous materials must not be fed into the furnace to prevent fire, explosion, or other safety incidents.
1.2 High-calorific materials, such as oil-absorbent cotton yarn, must not be piled up in large quantities. Materials weighing over 1 kg should be mixed with low-calorific substances to avoid excessively fierce flames during the initial combustion phase, which could cause a sudden increase in air pressure (negative pressure), leading to fan surge. Additionally, this helps prevent high-temperature alarms in the furnace during later combustion stages.
1.3 Oil-absorbent cotton yarn must not come into direct contact with high-temperature refractory bricks to prevent localized overheating and cracking of the bricks. When loading oil-absorbent cotton yarn, the "ash removal" procedure should be activated to promptly discharge any flammable gases generated, ensuring the safety of operating personnel.
1.4 Materials with high moisture content or low combustibility should be placed on the surface of the waste layer. This allows them to utilize heat from other waste during combustion, reducing fuel consumption for auxiliary burning.
1.5 Lightweight materials must not be scattered on the surface. They should be placed in waste bags or positioned beneath other waste to prevent them from being sucked into the flue during the initial air sweep, which could block the flue gas damper or flue gas fan.
1.6 The total volume of solid waste fed into the furnace must not exceed two-thirds of the furnace capacity. This ensures sufficient space and oxygen supply for effective waste combustion.
1.7 Materials such as glass, which can melt inside the furnace, are strictly prohibited. Once melted, such materials can adhere to the furnace surface, forming hard deposits that are difficult to remove and may impair normal furnace operation.

2. Garbage Combustion

After the incinerator is started, it will operate sequentially according to a fixed procedure: pre-sweeping, ignition, waste incineration, post-sweeping, and cooling. The key operational points for each stage are as follows:

2.1 Pre-sweeping: The core purpose of this stage is to expel any residual flammable gases from the furnace before ignition, reducing the risk of explosion upon ignition. After the pre-sweeping program is initiated, the control panel display will show "Pre-sweeping," and the program execution time must not be less than 15 seconds (set to 15 seconds on this vessel).

2.2 Ignition Program: The system automatically performs a flame check before ignition. If a flame signal is detected, a prompt box will appear on the display, and the operator must respond within 5 seconds. If no response ("Yes" or "No") is made within 5 seconds, the system will trigger a flame failure alarm. If "Yes" is selected to confirm the presence of residual flame in the furnace, the system will proceed normally with subsequent programs. This design is superior compared to some similar equipment, especially when restarting after an intermediate flameout during sludge combustion. It prevents the ignition program from being affected by high furnace temperature or red-hot furnace walls, effectively saving time and fuel consumption for secondary startup.
When the furnace vacuum level reaches the ignition setpoint (-16mm on this vessel), the ignition transformer begins operation, energizing for 10 seconds, with the diesel nozzle opening at the 6th second. After the ignition transformer de-energizes, the system again checks for flame presence in the furnace. If no flame is detected, a flame failure alarm is triggered. If flame is detected, the incineration program proceeds.

2.3 Solid Waste Incineration: After successful ignition, as the furnace temperature gradually increases, the damper regulator on the exhaust flue will progressively open to increase the furnace vacuum level, maintaining a dynamic balance between vacuum and the furnace heating rate. Since the solid waste incinerated on board, such as oil-absorbent cotton yarn and rags, mostly consists of high calorific value materials, the heating rate during incineration is relatively fast. To prevent the furnace temperature from exceeding the maximum limit of 1180°C, it is recommended to manually stop the incineration program when the furnace temperature reaches 300°C, allowing the solid waste to continue burning using its own heat. It should be noted that the preset combustion time is typically 90 minutes, which is generally sufficient for complete waste combustion. If the preset time is set to 0, the operator must manually stop the furnace.

2.4 Post-sweeping and Cooling: During the post-sweeping stage, the furnace vacuum level is automatically adjusted to the set value (-18mm on this vessel). The cooling phase of post-sweeping lasts for a relatively long time. When the furnace temperature drops below 220°C (the furnace door opening temperature), the operator may choose to manually stop the cooling fan. If not stopped manually, the fan will continue operating to cool down until the furnace temperature falls below 100°C, at which point it automatically shuts down, entering standby mode. A special reminder: if stopping the furnace and opening the door at 220°C with plans to continue loading flammable solid waste, the furnace temperature must be further reduced to prevent spontaneous combustion of the waste during the loading process.

3. Ash Removal Procedure

The ash removal operation must be strictly performed according to the following steps: First, press the "Door Open" button. After the furnace door is fully opened, press the "Ash Removal" button. (During ash removal, the system will automatically execute the action of closing the flue gas damper to prevent ash from dispersing within the engine room.) After a 30-second delay, the flue gas fan starts. The dispersed ash will be extracted outside the ship by the fan, at which point the operator can proceed with cleaning the slag and ash.

It is important to note that after pressing the "Ash Removal" button, a confirmation page will pop up on the system. The operator can press "Confirm" to initiate the ash removal procedure or press "Cancel" to return to the original operation page.

Basic Principles of Sludge Oil Incineration Mode

The sludge oil incineration process is similarly divided into three key stages: sludge oil processing, sludge oil combustion, and slag handling. The operational quality at each stage directly affects the efficiency and effectiveness of the sludge oil incineration.

1. Sludge Oil Processing

The core objective of sludge oil processing is to remove water and large-particle impurities, as these two factors play a decisive role in the combustion effectiveness.

1.1 Large-Particle Impurity Processing: Large-particle impurities are filtered by the sludge pump filter during the sludge transfer process. To ensure effective filtration, it is recommended that operators regularly clean the filter and check for any damage. Additionally, installing an extra fine-mesh screen has proven effective in practice. This measure significantly reduces the formation of hard slag on the inner walls and bottom of the furnace, thereby protecting the furnace lining and reducing subsequent cleaning workload. Some earlier models of similar equipment did not have filters installed on the sludge combustion pipeline. However, the incinerator used on this vessel has been improved with the addition of a filter at the nozzle inlet, further minimizing slag generation within the furnace.

1.2 Water Content Processing: Water treatment is a critical aspect of sludge oil processing and can even be decisive for the overall incineration rate. According to the equipment manual and daily operational experience, the incineration rate of sludge oil is closely related to its water content. When the sludge oil contains a certain amount of evenly mixed water, it does not hinder the incineration rate. Instead, the steam can carry away more heat, potentially increasing the incineration rate to some extent. However, excessive or uneven water content can easily lead to flame failure. In such cases, the system automatically initiates the diesel-assisted combustion mode, which increases diesel fuel consumption. Figure 4-16 (the curve showing the influence of sludge oil water content on the incineration rate) uses a "standard sludge value" referring to sludge with 20% water content. This curve comprehensively reflects the impact of sludge water content on the incineration rate, equivalent standard sludge combustion effectiveness, and diesel consumption. (Note: The maximum sludge incineration rate is limited by factors such as metering pump capacity and pipeline diameter and cannot be increased indefinitely.)

1.3 Practical Operation: Precisely controlling the water content of sludge oil is challenging in practice. Operators can estimate oil quality by considering the evaporation temperature of the settling tank, the state of sludge samples, and the condensate flow rate in the vent pipe. The specific assessment method is as follows: When the settling tank temperature rises to near 100°C (considering potential variations in thermometers across vessels, the actual reference temperature on this vessel is 97°C), the discharged sludge is non-viscous, and condensate in the vent pipe return tray intermittently drains as a fine stream every 5 seconds, the quality of the evaporated sludge oil is optimal. If the sludge is too viscous, the combustion speed will be slower, but the calorific value produced is higher. In this case, a small amount of sludge can be transferred from the sludge tank for dilution and adjustment.

1.4 Differences in Waste Oils: Additionally, attention must be paid to the differences in waste oils from various tanks in the engine room. For example, waste oils from the lube oil drain tank, fuel oil drain tank, and sludge tank have different properties and require different handling methods. Waste oil from the lube oil and fuel oil drain tanks can be incinerated directly after thorough draining in the settling tank until no water remains. The combustion temperature for these oils should be controlled between 60-70°C. These waste oils can also be used to adjust the quality of oil in the sludge tank.

1.5 Precipitation Issues: During sludge processing, continuous evaporation occurs in the incinerator's settling tank or sludge tank (on some similar models), raising the temperature above 100°C. This can easily cause sludge blocks to settle at the bottom of the tank. Long-term accumulation can clog the level gauge, affecting level readings, and also impair the suction efficiency of the transfer pump and combustion efficiency (manifesting as increasing difficulty in the later stages of combustion, reduced rate, and susceptibility to flameout).

1.6 Post-Processing and Optimal Temperature: After processing, the sludge oil can be transferred to the sludge service tank via the transfer pump. According to the equipment manual, sludge oil can be incinerated once it reaches 75°C. However, based on this vessel's operational experience, the optimal combustion temperature varies for different fuel types: 80°C-85°C for 380CST sludge, and 75°C for the currently used low-sulfur 180CST sludge. Regardless of the type, the maximum combustion temperature must not exceed 92°C, as excessively high temperatures accelerate the aging and damage of shaft seals and metering pump stators.

1.7 Temperature Control Post-Ignition: Once normal sludge oil combustion is achieved, promptly close the heating valve of the incinerator service tank to prevent the sludge temperature from continuously rising, which could trigger a high-temperature alarm and shutdown. Some similar models use a heating solenoid valve to control the sludge tank temperature. This vessel is not equipped with such a device (the related function keys on the display are inactive). Instead, the oil tank heating system has been modified to use a thermal balance-type heating valve installed on the hot oil inlet pipe, enabling automatic temperature regulation. The main reason for closing the hot oil valve on this vessel is that the entire circulation pipeline of the sludge service tank is equipped with tracing pipes. Given the engine room's hot oil temperature is maintained at 160°C-170°C, the tracing effect is sufficient to meet temperature demands despite dynamic changes in tank oil volume. If the temperature remains uncontrollable when the sludge is nearly consumed, it can be addressed by adjusting the tracing valve or adding a small amount of sludge.

1.8 Critical Safety Note on Fuel Return Line: Special attention must be paid to ensure that there are no closed valves or blanks on the return fuel line from the burner to the diesel oil tank. Operating the burner with a blocked return line can severely damage the burner oil pump (this issue has occurred on some similar equipment). The incinerator on this vessel is designed with a safety valve on the light oil return line, where the overflow pipe returns directly to the inlet pipe. This design effectively protects the oil pump. However, since the designed highest point for light oil in the incinerator is lower than the oil pump inlet, and neither the tank outlet valve nor the return valve is a one-way check valve, fuel backflow occurs after shutdown. When restarting after an automatic shutdown exceeding 5-6 hours, the diesel oil pump often struggles to build pressure. In such cases, operators can briefly activate the KM2 relay of the high-pressure oil pump to run it independently, quickly venting air via the outlet pressure gauge. To avoid this issue, responsible personnel must close the light oil inlet and outlet valves leading to the incinerator burner during prolonged shutdowns.

1.9 Handling Water in Sludge Oil: If the sludge transferred to the sludge tank contains significant water and has stratified, the lower layer of wastewater can be drained to the bilge water tank after settling. It is recommended to perform draining when the tank temperature is above 60°C, avoiding low temperatures to prevent incomplete drainage of residual water. Current drain designs on all vessels have certain flaws, making precise manual control difficult. This can easily lead to small amounts of oily wastewater being discharged, accumulating over time and polluting the sewage tank, which is detrimental to the normal operation of the oil-water separator. Therefore, this vessel does not recommend direct draining. Instead, heating and evaporation are used, allowing vapor to pass through vent pipe openings to recover condensate before introducing it into the drain hole leading to the sewage tank. For similar equipment with only one tank, to shorten processing time, a transparent hose can be connected below the drain pipe into a small oil bucket. Draining should be stopped immediately when oil is observed flowing through the hose. Furthermore, for small amounts of water in the sludge that cannot be separated by gravity, it can be incinerated directly after heating and evaporation to a certain temperature. This method has been successfully applied on this vessel with good results.

2. Combustion of Sludge Oil

The sludge oil incineration process is primarily divided into five stages: sludge oil heating, pre-sweeping, ignition, sludge oil incineration, and post-sweeping and cooling. The specific operational requirements are as follows:

2.1 Sludge Oil Heating: If the sludge oil temperature is below the setpoint of the sludge oil tank temperature switch, the system will pause the pre-sweeping program. It will only proceed with pre-sweeping after the sludge oil temperature rises to the setpoint (set to 60°C on this vessel).

2.2 Pre-sweeping: The pre-sweeping program for sludge oil incineration mode is identical to that of the solid waste incineration mode. Its purpose is to expel flammable gases from the furnace to ensure ignition safety.

2.3 Ignition: The ignition program for sludge oil incineration is the same as for solid waste incineration. Operators must strictly follow the prompts to avoid fault alarms caused by improper operation.

2.4 Sludge Oil Incineration: After the ignition program is executed, the photoresistor detects the flame signal, and the diesel nozzle activates to heat the furnace. At this stage, the damper opening is relatively reduced to ensure rapid furnace temperature rise. When the furnace temperature reaches the setpoint for the sludge oil start-of-combustion temperature (typically set to 650°C), the sludge oil metering pump starts. Its initial frequency is set to 20 Hz (which can be adjusted appropriately based on the actual combustion conditions of the sludge oil). The diesel nozzle continues to burn until the furnace temperature rises to the setpoint for the sludge oil independent combustion temperature (typically set to 850°C and can be flexibly adjusted based on combustion effectiveness). At this point, the diesel nozzle stops, and the sludge oil enters the independent combustion stage. The system automatically controls the metering pump frequency to stabilize the furnace temperature within the range of 985°C to 1035°C.

2.5 Post-sweeping and Cooling: The post-sweeping and cooling program for sludge oil mode is identical to that of the solid waste mode. Operators can refer to the relevant operational requirements for solid waste incineration.

During the combustion process, the following parameters require focused attention and adjustment: maintain the sludge oil circulation pressure at 0.04 MPa, the atomizing air pressure at 0.2 MPa, and the oil temperature at approximately 85°C (adjust based on the sludge oil type). The atomizing air pressure can be flexibly adjusted according to the sludge oil combustion conditions: if the sludge oil has high water content and is difficult to burn, the atomizing air pressure can be appropriately reduced; if the sludge oil has low water content and high calorific value, the atomizing air pressure can be appropriately increased. Specific parameters should be determined based on the on-site combustion effectiveness.

3. Slag Handling

Slag handling should be performed after the incinerator automatically shuts down and enters standby mode, following the ash removal procedure described earlier. During the operation, appropriate protective measures must be taken to avoid ash contamination or burns from high temperatures.

Basic Principles of Solid Waste + Sludge Oil Mixed Incineration Mode

The operational logic of this mode is as follows: It first operates according to the solid waste incineration mode. When the calorific value of the solid waste decreases to a certain level, the system automatically switches to the sludge oil incineration mode. The mode switch requires the simultaneous fulfillment of the following two conditions for a duration of 3 seconds: first, the diesel oil must be in the high-fire combustion state; second, the furnace negative pressure must be less than -25 mm. Only when both conditions are met and maintained for 3 seconds will the system automatically switch to sludge oil mode.

Daily Maintenance Key Points

Performing daily maintenance on the incinerator is crucial for ensuring stable equipment operation and reducing the failure rate. Daily maintenance primarily covers the following five areas:

1. Diesel Oil Line Maintenance
When restarting the incinerator after it has been stopped for a period of time, or after cleaning the diesel filter, the diesel pump may fail to build pressure. In such cases, it is necessary to promptly bleed the line to ensure the diesel oil line is unobstructed, guaranteeing normal equipment startup.

2. Sludge Oil Line Maintenance
The function of the incinerator's sludge oil gun is equivalent to the fuel injectors of the main and auxiliary engines. Its cleanliness directly affects the atomization effectiveness of the sludge oil. If the sludge oil combustion condition deteriorates and adjusting the atomizing air pressure and sludge oil pressure does not improve combustion, this typically indicates that the oil gun is dirty, clogged, or has carbon deposits. The oil gun needs to be disassembled from the burner, taken apart, and have internal carbon deposits thoroughly removed. Simultaneously, filters in the sludge oil line should be regularly disassembled and cleaned to prevent impurity buildup from causing line blockages.

3. Air Line Maintenance
The incinerator's air supply comes from the engine room's daily air system, with a normal working pressure of 7-8 BAR. The unobstructed flow of the air line directly affects the sludge oil atomization effectiveness and, consequently, the combustion efficiency. During daily maintenance, regularly clean the filters on the air lines and check all air line connections for leaks. Ensure the air path to the oil gun is clear to guarantee sufficient combustion of the sludge oil.

4. Operating Condition Adjustment Maintenance
During incinerator operation, closely monitor the combustion condition and promptly adjust relevant parameters based on the actual situation:

If phenomena such as a dim, red, unstable flame, black smoke from the exhaust pipe, or large areas of incomplete combustion carbon deposits (in "hillock" shapes) forming on the refractory brick in the furnace occur, the combustion state can be improved by appropriately adjusting the supply air pressure and atomizing pressure.

The frequency of the sludge oil metering pump needs to be flexibly adjusted based on the sludge oil quality. Setting the frequency too high can easily cause black smoke, while setting it too low may trigger a flame alarm. Operators need to precisely control this based on the combustion effectiveness.

5. Furnace Cleaning Maintenance
Each time the furnace is cleaned, operators should focus on inspecting key areas such as the temperature probe, the area around the oil nozzle, and the furnace connection point of the air pressure pipe for carbon deposits or sludge clogging, and clean them promptly if found. Regular furnace cleaning prevents dirt and clogs from affecting the detection of equipment operating parameters and combustion effectiveness, thereby extending the equipment's service life.