An alternative method to dispose of the FWL was investigated by evaluating the potential for using an incineration treatment. Fig. 1 shows the schematics of the municipal solid waste incinerator plant that was considered in this study. The plant includes two furnaces and incinerates approximately 90 tons of MSW per day. This study considered an incinerator consisting of one furnace with SNCR flue-gas cleaning systems. All data regarding the incinerator and the flue-gas cleaning system were obtained from the MSW incinerator in Y city, South of Korea.

The input position and the quantity of the FWL were adjusted to determine the effect that FWL injection dosage had on NOx reduction in the incineration process. The FWL consisted of 87.1% moisture content, 11.8% combustible matter, 1.1% ash, 49.8% carbon content, 4% nitrogen content, and a high heating value (HHV) of 5,232 kcal/kg, 420 ppm of NH₃-N were present in the FWL, as shown in Table 1. This ammonia in the FWL will have effects in reducing NOx released in the MSW incinerator.

The relationship between the ammonia injection dosage, the ammonia slip and the NOx removal in the flue-gas cleaning system were investigated in a full-scale MSW furnace incinerator. The relationship between the ammonia injection dosage, the FWL injection dosage, and the NOx removal in the flue-gas cleaning system was determined. The furnace temperature was determined by using an automatic monitoring system. The NOx concentration of flue-gas was determined by using the Optima 7 handheld multigas analyzer.

Different combustion conditions in the incinerator, including the ammonia injection dosage, ammonia slip and ammonia injected with the FWL, will affect the amount of NOx concentration and the furnace temperature. First, the FWL injection disturbed the combustion reaction in the MSW incinerator. Table 2 shows a comparison of the effect that the injection conditions of the ammonia and FWL dosage had on the NOx emission and furnace temperature. Ammonia water is commonly used in an SNCR system to reduce NOx emissions [6, 7], as in this research. Instead of the ammonia water, the ammonia (NH₄) in the FWL reacted to reduce the NOx emission. Without ammonia (just an injection of water at 1.5 m³/h), approximately 131 ppm of NOx were observed. The addition of ammonia water could reduce the NOx emission down to approximately 30 ppm with an injection of 24 L/h of ammonia. When FWL was injected at 2 m³/h, the concentrations of NOx emissions were reduced to approximately 44 ppm, which was similar as that achieved when ammonia water was injected at a rate of 24 L/h. Furthermore, the FWL injection did not have an effect on the operating temperature of the MSW incinerator, which further provides guidance for an institutional framework.

Figs. 2 and 3 show the results of operating the MSW incinerator with and without FWL injection. The MSW incinerator usually processed 90 tons/day, and the ammonia water is injected in the SNCR system to decrease the NOx emission. Ammonia water had been injected at 14.3 L/h, which was the basis for the fundamental operation of the MSW incinerator. When the MSW incinerator operated with ammonia water, as shown Fig. 2, the NOx emission could not be reduced beyond 40 ppm of NOx, and the NOx emission was generally of approximately 76 ppm (between 62 and 78 ppm). When, 2 m³/h of FWL were injected in the MSW incinerator with 14.3 L/h of ammonia water, the NOx emission decreased to approximately 27 ppm (as shown Fig. 3). The ammonia components consiste of 420 ppm of NH₄-N in FWL, as shown in Table 1, which substitute the ammonia water agent in the incinerator [8, 13–15]. This FWL that is injected for removal can therefore reduce the generation of NOx. As a result, FWL can be useful to replace ammonia water, especially since the operating conditions of the incinerator, such as the temperature and the stream generation (Fig. 4), were as those of other conditions, e.g., the heat loss remained below 13%. However, increasing FWL injection dosage will affect decreasing furnace temperature including emitting dioxin.

The fundamental operation of an SNCR system for an MSW incinerator involves injecting 22.3 L/h of ammonia water to reduce NOx emission. The SNCR system could reduce NOx emission in flog-gas to less than 40 ppm. Injecting the FWL could help reduce ammonia water usage and could provide an option to remove FWL. The optimum condition to inject the FWL was of approximately 2m³/h. The modified operation of the MWS incinerator with a 2 m³/h injection of the FWL could reduce ammonia water usage from 22.3 L/h to 14.3 L/h (the savings efficiency for the ammonia water was of 35.9%) as shown in Fig. 5. NH₃-N injection dosage of FWL with ammonia water (NH₃-N concentration of FWL is 725 mg/L as shown in Table 1, NH₃-N content of 2 m³ FWL is 1,450 g) can help to reduce ammonia water injection dosage. Furthermore, modifying the conditions of operation for the MWS incinerator, such as injecting FWL, did not have an effect on the other conditions, such as the incinerator temperature that remained at approximately 920°C and the steam generation that were similar to those without FWL (Fig. 4).