Incinerator in a Ship? Know More About Construction and Components of Incinerator
Incinerators are equipment used on ships to burn various types of waste, including sludge, paper, wood, soot, tarpaulin, and plastics (incinerators are specially designed to burn plastics and are certified by the International Maritime Organization). They are also used to burn sludge (liquid) and solid waste generated on board ships.
Under the MARPOL Convention, Annex V regulates the handling of shipborne waste and sets guidelines for different types of waste. To prevent marine pollution, the annex prohibits dumping many types of waste into the sea, including plastics, food waste, paper, etc.
However, burning garbage on board can help reduce the amount of garbage that must be stored on board and reduce the risk of marine pollution. Therefore, the use of incinerators is an important solution for managing ship garbage. Burning waste can reduce its volume, and the ash residue can be safely stored or disposed of. This helps prevent the discharge of harmful substances into the sea and protects the marine environment.
Note: If the incinerator is not operated properly and the emissions are not properly monitored and controlled, it can become a source of air pollution.
Sludge Incineration Process in Incinerator
Sludge generated from various sources on board, such as the lubricating oil sludge tank and clarifier sludge tank, is usually transferred to the incinerator’s waste lubricating oil tank.
Since the sludge contains water, it is difficult to burn effectively. To solve this problem, people use high-temperature steam to evaporate the water and then discharge it through the ventilation pipe.
A sensor filled with mercury is placed inside the waste lubricating oil tank to sense its temperature. The steam pipe thermostatic valve is installed on the steam pipe to regulate the steam flow rate according to the temperature detected by the sensor.
The waterless sludge generated is directly transported from the incinerator waste oil tank to the incinerator for further combustion.
Note: In some cases, fuel oil sludge and lubricating oil sludge are difficult to burn and need to be mixed to achieve proper combustion.
Incinerator Components and Parts:
Induced Draft Fan: An Induced draft fan is usually used to extract air from the furnace and create negative pressure inside, introducing fresh air from the atmosphere. Fresh air is used for combustion and furnace cooling. The basic components of the induced draft fan include the propeller, motor, transmission mechanism (belt), and casing.
2. Diesel Incinerator Tank: The diesel incinerator tank stores diesel for use in the incinerator combustion process. It is usually located near the incinerator and connected to its fuel supply system.
3. Pilot Ignition Assembly: The pilot ignition assembly is located near the main burner and consists of a nozzle, electrodes, and a solenoid valve. It provides the initial flame required to ignite the waste on board.
A potential of 10,000 volts is generated on these electrodes, producing sparks in the 3 mm to 5 mm gap between them. The diesel is injected through the nozzle. A solenoid valve is installed here to control the air flow. These three components help initiate the ignition process.
4. Main Burner Assembly: The main burner is the key component responsible for generating the high temperatures required for incineration of waste on board. The incinerator’s main burner is a rotary cup burner. It consists of several components, including an electric fan and drive mechanism, a gear diesel pump, and a solenoid valve (temperature control).
When the solenoid valve senses a temperature above 650°C, it lets the oil flow into the furnace to burn the sludge at high temperatures.
5. Furnace chamber: The furnace chamber is the main part of the incinerator, where the garbage is incinerated at a high temperature of about 800-1200°C. It is an enclosed space made of high refractory materials such as refractory bricks or castable refractory materials.
6. Baffle: The baffle’s function is to maintain a constant airflow in the incinerator. It is usually a movable plate or valve installed on the exhaust side and the atmosphere side, which controls the air flow and regulates the exhaust temperature by mixing the together.
Control & Automation:
Door Open Alarm:
The door open alarm is a safety feature that alerts operators that the furnace door is open and that they should not operate the incinerator. If a fire occurs inside the oven with the door open, hot gases or flames could escape and cause a fire in the machine room.
Oven High Temperature Alarm:
When the furnace temperature exceeds 1200°C, the refractory material is damaged, causing the burner to start and cut off the fuel supply.
Oven Low Temperature Alarm:
When the furnace temperature drops to 650°C, the furnace’s low temperature alarm is triggered and the burner starts, which causes incomplete combustion and damages the refractory material.
Gas High Temperature Alarm:
The maximum temperature of the exhaust gases coming out of the furnace is 350°C. If the temperature exceeds this limit, an alarm will sound, indicating a malfunction.
Misfire:
If the induced draft fan is not running or negative pressure is not created in the furnace, the induced draft fan fault alarm will be activated. This alarm indicates that there is no vacuum in the oven. If the induced draft fan cannot draw air out of the furnace, proper combustion will not occur, and fresh air will not be introduced. A vacuum gauge is installed to measure the vacuum pressure inside the furnace. If there is no vacuum inside the oven, an alarm is triggered.
Flame Eye:
The flame eye detects the flame inside the incinerator. The photoelectric cell installed in the flame eye checks the presence of the flame. If there is no flame, the waste oil will not be fed into the furnace, or the main burner will be started.
