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This project consists of two sets of waste liquid treatment system, which are used for the oxidization treatment of a portion of the waste liquid and off-gas generated during the production process of 750,000 tons/year of propylene and downstream processing projects. The project’s engineer design is undertaken by Ruiding Environmental Engineering Co., Ltd.

Ruiding employs the direct-fire thermal oxidizer (TO) process. When the waste liquid treatment facility is operating normally, high calorific value waste liquid is pressurized and conveyed to the waste liquid atomizer configured at the furnace head by the owner through a pump. After atomization with 0.5 MPaG saturated steam, the waste liquid is combusted in the incinerator at high temperature oxidation. Low calorific value waste liquid is pressurized and conveyed to the waste liquid atomizer configured at the membrane wall shoulder by the owner through a pump. After atomization with compressed air at 0.7 MPaG, the wastewater is combusted in the incinerator at high temperature oxidation. At the same time, the waste liquid treatment facility is equipped with a waste gas burner to meet the system's need for combusting organic waste gas. The oxidizer system is designed to ensure that the flue gas generated by the combustion of waste liquid and off-gas remains in the incinerator for a sufficient residence time (not less than 2 seconds), while the outlet flue gas temperature is not less than 1100°C.

After undergoing thorough thermal oxidation and reduction, the flue gas is cooled to around 170°C by recovering heat in the waste heat boiler, making it convenient to enter the subsequent dust removal system. The waste heat boiler recovers heat, producing superheated steam at 4.0 MPaG and 450°C. This superheated steam can be used to preheat the incoming waste gas, thereby conserving resources.

With smoke containing relatively fine dust entering the bag filter, as the smoke passes through the filter bag, the dust in the smoke is trapped on the outer surface of the filter bag, thereby achieving purification, ensuring that the dust emission in the smoke meets national environmental standards. During operation, the dust accumulated on the outer surface of the filter bag continuously increases, resulting in an increase in the resistance of the dust collector. To maintain the equipment's resistance within the specified range, it is necessary to regularly remove the dust adhering to the surface of the filter bag. The control instrument triggers various control valves to open the pulse valves in a predetermined sequence, allowing compressed air from the air chamber to be sprayed out through the nozzle holes (referred to as primary air). Through the venturi tube, surrounding air (referred to as secondary air) several times the primary air is induced to enter the filter bag, causing the filter bag to expand sharply in an instant and, accompanied by the reverse action of the airflow, shake off the dust.

Due to the high-temperature incineration of wastewater and waste gas, a small amount of thermal and fast NOx is generated. Therefore, SNCR atomizers are designed at specific locations in the temperature range of 850 to 1050°C in the combustion furnace to achieve denitrification of the flue gas inside the furnace using the SNCR process.

The system design includes an induced draft fan, positioned at the rear of the bag filter. The flue gas generated from the final incineration process is drawn by the induced draft fan and discharged through the chimney to meet environmental air quality standards.

The project was officially commissioned and put into operation on March 26, 2023, after successful acceptance testing.