[Delivered Products & Systems] Report on Delivery and Operational Condition of Grate-type (Stoker-type) Incinerator with Advanced Flue Gas Treatment System in China -Nanjing City, Jiangsu Province- Kazushige KUROSAWA*, Zhibao ZHANG**, and Zhengbing WANG** Abstract Ebara s grate-type incinerators with a treatment capacity of 2 t/d (5 t/24 h 4 lines) were delivered to Nanjing City, Jiangsu China, and their performance test was completed in March 216. Ebara Environmental Plant Co., Ltd. and Ebara Qingdao Co., Ltd, have already delivered incinerators to seven facilities in China: fluidized-bed incinerators to two facilities and grate-type incinerators to five. Three of them have been reported in past issues of the Ebara Engineering Review. This paper reports on the delivery of incinerators to the eighth facility in China, the plant capacity of which is the largest among the eight facilities. In China, there is a need for ever-more-sophisticated waste incineration technology; in 214, the relevant national standard of China was revised, and more stringent emission regulation of waste incineration plants were imposed. This paper reports the operating conditions, performance test results, etc., of the sophisticated flue gas treatment facility to meet the more stringent emission regulation. Keywords: China, Nanjing, Municipal solid waste, Grate-type incinerator, EGR, SCR, Sodium bicarbonate injection 1. Introduction On March, 216, The Ebara group delivered grate-type incinerators to a Waste-to-Energy (WTE) Plant in Nanjing City, Jiangsu Province, China, where we conducted a performance test and turned them over. (Figure 1). This is the second WTE plant in Nanjing. The plant was constructed by Nanjing Waste to Energy Co., Ltd., a special purpose company (SPC) established by Shanghai Environmental group Co., Ltd., which undertook the project from the Nanjing government. The scope of Ebara s contribution to the project included the basic design of the incineration system (from the waste bunker to the stack) and the supply of the main equipment of the incineration plants. Our past experience allowed us to take into proper consideration China-specific waste characteristics - high moisture and ash content. Thus, we adopted refinements and improvements for the scale-up design of the incinerator. 2. Overview of Nanjing Fig. 1 Nanjing Waste-to-Energy Plant * Ebara Environmental Plant Co., Ltd. ** Ebara Qingdao Co., Ltd. Nanjing City, the capital of Jiangsu Province, China, is the center of politics, the economy and culture, as well as a strate gic point in the traffic patterns for Jiangsu. The city has an area of 6 597 km 2 with a population of approximately 8.18 million. Nanjing, the ancient capital of the Six Dynasties, well known as a historical and 1
Table 2 Equipment specification cultural city built about 26 years ago, has been a major city in the region of the Yangtze River basin in South China. Nanjing, with its warm and humid climate, is very hot and humid in summer. Nanjing, Chongqing and Wuhan are famous for being the hottest cities in China and are colloquially referred to as The Three Furnaces. Hohhot Beijing Taiyuan Qingdao Nanchang Zhangzhou Figure 2 shows the location of Nanjing in China. 3. Overview and characteristics of the plant Table 1 shows the lower calorific values and composition of the waste in Nanjing; Table 2 shows the specifications of the equipment; Figure 3 shows the process flow in the plant; Table 3 shows the emission criteria of the stack outlet flue gas. O211% equivalent is the value according to Chinese standard, O212% equivalent is the value converted to the standard oxygen concentration used in Japan. 4. Scope of supply, performance warranty and construction schedule Weihai Shanghai Xiamen Harbin Nanjing City, Jiangsu Delivered grate-type incinerators Delivered fluidized-bed type incineration plants Fig. 2 Location of Nanjing, Jiangsu, in China Table 1 Lower calorific value of waste and waste composition Item Lower calorific value Low-calorific Value waste Design waste High-calorific Value waste 4187 kj/kg 6699 kj/kg 8374 kj/kg Moisture content 56.1% 48.4% 43.2% Combustible content 25.2% 33.4% 38.9% Ash content 18.5% 18.1% 17.8% In China, differently from Japan, construction of WTE plants is often undertaken by the SPC itself which conducts the project. Consequently, we are responsible Item Incinerator Boiler 3 Steam turbine generator 4 Flue-gas treatment facility 3 Stack 3 Table 3 The emission value of the stack outlet flue gas Item O211% equiv. O212% equiv. Dust 8. mg/m 3 (NTP) 7.2 mg/m 3 (NTP) Sulfur oxides (SOx) Nitrogen oxide (NOx) Hydrogen chloride (HCl) Carbon monoxide (CO) Hydrogen fluoride (HF) for the basic design (from the waste bunker to the stack, including part of the detailed design) of the incineration system, the delivery of main equipment (grates, hydraulic drive units, burners, the ACC system, and waste hopper level sensors), and dispatching supervisors. Guaranteed values are shown in Table 4. Table 5 shows the Construction schedule. It took 3 years and 2 months from the signing of the contract to hand-over. 5 mg/m 3 (NTP) 8 mg/m 3 (NTP) 1 mg/m 3 (NTP) 5 mg/m 3 (NTP) 1 mg/m 3 (NTP) Specification Model HPCC from Ebara 1 Grate-type Incinerator Capacity: 2 t/d (5 t/24 h 4 lines) Type: Natural-circulation water tube boiler with superheaters Steam capacity: 47. t/h (Max. 51.7 t/h) 4 units Steam condition: 4 4. MPaG (at the outlet of the superheater) Steam turbine (condensing type) + generator Steam turbine: 18 MW 2 units Generator: 2 MW 2 units Dust collector type: Bag filter Removal method of HCl SOx: Semi-dry type system (slaked-lime slurry rotary atomizing injection) + dry type system (sodium bicarbonate injection) De-NOx method: SNCR 2 + SCR 2 Removal method of dioxins Hg compounds: activated carbon injection External wall: Reinforced concrete structure Internal stack: Carbon steel Height: 8 m 1: HPCC: High Pressure Combustion Control 2: SNCR: Selective Non Catalytic Reduction SCR: Selective Catalytic Reduction 3: Ebara s scope of work: Basic design SPC s scope of work: Detail design, Purchase and Construction 4: SPC scope: Design, Purchase and Construction 15.8 ppm 35.1 ppm 5.5 ppm 36. ppm 1. ppm Dioxins.1 ng-teq/m 3 (NTP).9 ng-teq/m 3 (NTP) 2
SNCR Steam Air preheater Forced draft fan Flue gas recirculation heater Slaked lime slurry Flue gas recirculation fan Steam turbine-generator Sodium bicarbonate Ammonia water Waste crane Boiler Activated carbon Ammonia water vaporizer Waste truck Platform Waste pit Waste hopper Incineration furnace Semi-dry reactor Bag filter Flue gas heater SCR tower Induced draft fan Stack Bottom ash discharger Bottom ash Fly ash Fig. 3 Flow sheet of plant Item Annual total operation time Operating load range (incineration load) The temperature of furnace outlet Ash ignition loss Boiler efficiency Grate replacement ratio 5. Characteristics of the plant 5.1 Adoption of dry type sodium bicarbonate injection Table 4 Guaranteed values Guaranteed value 8 hours or longer 6% to 11% 11% within 2 h/d 85 C or higher at 2 seconds or longer 3% or less 8% or higher Operation time 8 hours less than 4% 16 hours less than 11% 24 hours less than 15% 32 hours less than 18% Nanjing city is near the border of Anhui Province; to restrain hazardous gas diffusion to other provinces, very strict emission standards are in place. To meet the hydrogen chloride emission criterion of less than 1 mg/m 3 (NTP), a wet scrubber system is most effective, but, because of its large water supply requirement, the discharge of drainage, and decreases in power generation, it was not adopted by the SPC. To ensure meeting the strict emission criteria, based on the semi-dry reactor chosen by the SPC, we suggested at the basic design stage using sodium bicarbonate as dry injection to fulfill the emission Table 5 Construction schedule Mile stone Schedule Contract January 213 Equipment installation July 213 to September 214 Commissioning (Waste incineration) January 215 to March 216 Hand-over March 216 criteria; this suggestion was ultimately adopted. For the concentration of HCl at the inlet of the flue gas treatment facility and the outlet of the stack, see Figure 4; for the SOx concentration, see Figure 5. The guaranteed value of HCl is 1 mg/m 3 (NTP) and the real average emission value is about 5 mg/m 3 (NTP); the removal rate is as high as 98.5%. In addition, the guaranteed value of SOx is 5 mg/m 3 (NTP) and the real average emission value is about 3 mg/m 3 (NTP); the removal rate is as high as 91%. 5.2 Exhaust gas recirculation (EGR) as NOx Inhibition system and SCR as NOx removal system GB18485-214 (municipal waste incineration pollution control standards) was revised in 214, and the new NOx emission criteria for municipal solid waste incineration plants was 25 mg/m 3 (NTP) at O211% equivalent (about 11 ppm at O212% equivalent). However, because of the customer requirements and site conditions of the plant, sometimes the plant emission criteria are more strict than national standards, so it is necessary to adopt appropriate 3
5 5 Flue gas treatment facility inlet Flue gas treatment facility inlet HCl Conc. mg/m 3 (NTP) (O211% equiv.) 4 3 2 1 HCl Conc., average=325.6 mg/m 3 (NTP) Stack outlet HCl Conc., average=4.9 mg/m 3 (NTP) 4 3 2 1 Stack outlet HCl Conc. mg/m 3 (NTP) (O 2 11% equiv.) 8: 9: 1: 11: 12: 13: 14: 15: 16: Time h Fig. 4 Trend of HCl for the inlet of flue gas treatment facility and the outlet of stack SOx Conc. mg/m 3 (NTP) (O211% equiv.) 5 4 3 2 1 Flue gas treatment facility inlet SOx Conc., average=29. mg/m 3 (NTP) Stack outlet SOx Conc., average=2.7 mg/m 3 (NTP) 8: 9: 1: 11: 12: 13: 14: 15: 16: Time h Fig. 5 Trend of SOx for the inlet of flue gas treatment facility and the outlet of stack technology to meet such requirements. The NOx emission criteria for the plant is below 8 mg/m 3 (NTP) at O211% equivalent (about 35 ppm at O212% equivalent), which is more strict than the NOx emission criteria in Japan in most cases. So in the basic design stage, EGR with low air ratio operation was suggested by Ebara to reduce NOx generation. In addition to SNCR, SCR were also suggested to meet the strict emission value. As a result, the customer decided to adopt SCR only for Line 3 incinerator. The principle of SCR is that ammonia and NOx are under chemical reaction by catalysts to convert NOx into N 2 and H2O. SCR is common in Japan waste incineration plants but was newly introduced in China, with this plant. 6. Performance test results Except for some untested items because of some specifications from the SPC, all the items met the guaranteed values in the performance test. For the results of the performance test, see Table 6. The detailed effects of EGR have been reported in the latest journal 2) ; here, the operation data with SCR are shown in Figure 6. SCR was installed only in Line 3; therefore, the figure 6 refers to the data of Line 3. Because it was not able to perform the designed effect of EGR in Line 3 because of some specifications from the SPC, the 4
NO. Test item Unit 1 Steam temperature at the outlet of Boiler Table 6 Results of performance test (1% Load) Guaranteed value 4 ( + 5, 1) Line 1 Line 2 Line 3 Line 4 Conclusion 398.6 398.1 41.4 4. Qualified 2 Boiler efficiency % 8 82.56 81.58 82.88 81.29 Qualified 3 Retention time of flue gas of 85 or higher s 2 3. 3.2 3.3 3.2 Qualified 4 NOx (NTP, dry, O211%) NOx at boiler outlet with SNCR mg/m 3 (NTP) 8 78.2 72.5 1 1 1 NOx at SCR outlet mg/m 3 (NTP) 8 46.7 2 1 5 Flue gas at stack outlet (NTP, dry, O211%) Dust mg/m 3 (NTP) 8 4. 3.3 4.1 4.1 Qualified HCl mg/m 3 (NTP) 1 7.2 3.6 7.4 6.5 Qualified HF mg/m 3 (NTP) 1.7.6.8.7 Qualified SOx mg/m 3 (NTP) 5 8.9 1.7 1.6.1 Qualified CO mg/m 3 (NTP) 5 6.6 24.2 4.4 15.3 Qualified TOC mg/m 3 (NTP) 1 2. 1.7 4.4 1.4 Qualified Hg and compounds mg/m 3 (NTP).5 <.3 <.3 <.3 <.3 Qualified Cd and compounds mg/m 3 (NTP).5 <.8 <.8 <.8 <.8 Qualified Pb+Cr and other heavy metals mg/m 3 (NTP).5.31.1.29.18 Qualified Black degree of flue gas Ringelman 1 <1 <1 <1 <1 Qualified Dioxins ng-teq/m 3 (NTP).1.88.75.75.63 Qualified 6 Incineration capacity t/d 5 535.56 561.44 536.19 55.78 Qualified 7 Ash ignition loss. (wet ash) % (weight) 3 2.6 2.78 2.88 2.64 Qualified 1: Because of some specifications from the SPC, the EGR (exhaust gas recirculation) of Line 3 and Line 4 has not achieved the design result and the result was treated as inapplicable. 2: The SCR was installed only in Line 3 before the performance test. 12 18 SCR inlet/boiler outlet NOx Conc., average=1.8 mg/m 3 (NTP) NOx, CO Conc. mg/m 3 (NTP) (O 2 11% equiv.) 1 8 6 4 2 SCR outlet/stack outlet NOx Conc., average=47.6 mg/m 3 (NTP) Boiler outlet O2 Conc., average=4.2% SCR outlet/stack outlet CO Conc., average=4.3 mg/m 3 (NTP) 15 12 9 6 3 Boiler outlet O2 Conc. vol% 9: 1: 11: 12: 13: 14: 15: Time h Fig. 6 Trend of NOx of SCR inlet and outlet measurement was about 1 mg/m 3 (NTP) of NOx concentration at the inlet of the SCR (at the outlet of boiler), which was a little higher than the original design. On the other hand, the NOx concentration at the outlet of the SCR was decreased to less than 5 mg/m 3 (NTP), so the removal ratio of the SCR was more than 5%. This result demonstrates the capacity of the SCR system, when the NOx regulation level becomes more severe in future. 5
7. Conclusion In the large cities in China, many large-scale waste incineration plants have been constructed and the emission regulations have become equivalent to or stricter than those in developed countries in recent years. We are looking forward to contributing to the demand of waste incineration plants in China and the environmental protection causes based on our technological improvements and experience. Finally, we would like to express our grateful thanks to all the people who cooperated to this project. References 1) Kazushige Kurosawa, Wang ZhengBing, et al, Report on the Establishment of the Thermal Disposal Technology for Large-scale Grate-type Incinerators in China and on Stable Operation of Them (second report), Collected Papers Associated with the 37th waste Management Research Symposium, (January 216). 2) Koji KOBAYASHI, Kazushige KUROSAWA, Motoshi ARIHARA, Wenjie YANG, Zhibao ZHANG, and Binglai ZHAO Report on Delivery and Operational Condition of Large-scale Grate-type (Stoker-type) Incinerator in Nanchang City, Jiangxi, China, Ebara Engineering Review No.251 (April 216), pp.32-38. 6