Flue Gas Treatment System For Gasification Incinerator

Incineration is currently the main technical method for treating urban domestic waste and medical waste. The flue gas after incineration contains dioxins, CO, NO_x, SO₂, particulate matter and other harmful components. If not handled properly, it will pollute the environment and endanger human health. Countries have formulated relevant emission standards for flue gas after waste incineration, and have set limits on the concentration of various harmful gases. This article will discuss common flue gas treatment processes and energy recovery during waste incineration.

1. Common flue gas treatment processes

(1) Dioxin control technology

Dioxins are easily produced during the burning process of garbage. They are highly toxic and insoluble in water. They generally exist in gas and solid forms. There are three main ways to generate dioxin: ① The garbage itself contains trace amounts of dioxin; ② During the combustion process, it is generated from chlorine-containing precursors; ③ When combustion is incomplete, the decomposed dioxins are regenerated at 300~500℃ in the presence of heavy metals.

Based on the characteristics of dioxin, the following process is usually used to reduce the dioxin concentration in flue gas:

① Ensure full combustion in the incinerator and the flue gas stays above 850°C for at least 2 seconds. This will reduce the possibility of dioxin production from the source and complete the pyrolysis of already produced dioxin.

②In order to avoid the regeneration of dioxin, use heat exchangers and quench towers to quickly reduce the temperature of the flue gas to below 300°C.

③ Set up an activated carbon adsorption tower or dry powder injection to adsorb trace amounts of dioxins and heavy metals remaining in the flue gas.

(2) Dust removal process

After incineration, a large amount of fine fly ash and dust are generated, which enter the flue gas treatment system with the airflow. Fly ash may contain heavy metals and other pollutants, which are highly toxic and cannot be discharged after being inhaled into the lungs, which is extremely harmful to the human body. Usually, a settling chamber is set up after the incinerator to intercept large particles in the flue gas. Electrostatic dust removal and bag dust removal processes are used at the end to remove small particles in the flue gas. Fly ash is a hazardous waste. You can choose to contact a local hazardous waste disposal company for safe disposal, or equip it with a chelator for treatment and landfill.

(3) Acid waste gas treatment

The acidic gases in flue gas mainly include HCl, HF, SO2, NOx, etc. The concentration of acid gas produced after the incineration of different garbage raw materials is slightly different. Based on the principle of acid-base neutralization, the alkali liquid is atomized by a high-pressure nozzle to reversely flush the flue gas. The alkali liquid mist and the acidic substances fully contact and react, and finally achieve removal.

(4) Others

Due to the great differences in living habits of people in different countries/regions, the composition of domestic waste and the exhaust gas produced after incineration are also slightly different. There are also corresponding process options for other pollutants, such as activated carbon adsorption for heavy metals, SCR and SNCR processes for desulfurization and denitrification, etc. In the end, white smoke mainly composed of water vapor and CO₂ is discharged to achieve harmless emission standards.

2. Energy recovery

Garbage-to-energy is a mature process that uses the high heat generated by combustion to convert water into steam, which in turn drives the turbine to generate electricity. However, not all incineration scales are suitable for power generation. Generally speaking, for incineration plants with a daily incineration volume of less than 200 tons, it is not recommended to use the power generation model to recover energy. The reason is that the cost of power generation from incineration within 200t/d is high and the power output is low. Such small and medium-sized incineration systems generally use heat exchangers to allow high-temperature flue gas to pass through the tube side of the heat exchanger to heat the circulating cooling water in the shell side. The hot water can be used for heating in winter, and the circulating water can be cooled and reused through the cooling water tower above the circulating water pool in summer. The temperature of the recovered hot water is around 70°C.

Summary

Incineration of solid waste is not just about burning garbage. In order to reduce the pollution to the environment during the incineration process, a flue gas treatment system is essential, although this will increase the cost. HYHH will customize the design of a complete set of garbage gasification incineration system for you based on the specific site conditions, garbage composition, local flue gas emission standards and other actual information. Welcome to leave a message for consultation!