| With the progress of human civilization and the growth of population, the amount of municipal solid waste has become increasing and environment pollution more seriously; it has become a major obstacle for social economy sustainable development and ecological civilization construction. For the reaseas that smaller land acquisition, higher level of reduction, stability, harmless, energy utilization efficiency, and the waste incineration technology has become rapidly development. Although municipal solid waste incineration with a late starts, our country has completed the localization and large-scale of the mechanical grate incinerator based on introduction, digestion and absorption of foreign advanced technology. Meanwhile, relevant policies and pollution control standards in our contury will also put forward higher requirements for second pollution control. Nitrogen oxides are one of the major air pollutants of municipal solid waste incineration, and have become a research hotspot of secondary pollution. Therefore, based on characteristics of municipal solid waste in our country, it has become an important task for researchers working on municipal solid waste incineration to study NOX removal method with science and practeical based on Chinese national conditions.From foreign and domestic development experience, the SNCR de-NOX technology is suitable for municipal solid waste, for the reaseas that lower investment and operation cost than other de-NOX technology, easy to reconstruct, more suitable for the sombustion equipment with lower NOX content and reduction rate. For the characteristics of multi-conponent, multi-form, high moisture, high volatile, low heating value and fixed carbon of municipal solid waste in our contury, this paper studied SNCR NOX removal technology of municipal solid waste by theoretical analysis, experimental, numerical simulation, life cycle and economical assessment.Regarding drying oven as fixed bed, during 100200℃, this paper made drying experiment for different units and mixed waste. The results showed that the thicker of waste sample resulted in the lower drying rate and the longer drying time. Different dying models for different waste samples: Two term exponential and Page models for mixed waste; Page model for cabbage stem and orange peel. Effective diffusivity of waste samples is in the range of 1.62×10-9m2/s4.53×10-6m2/s and activation energy is 12.66kJ/mol17.25kJ/mol. Different moisture content affects the nitrogen oxides. With the increasing of moisture content, volatile maximum mass percentage increased, the NOX concentration reduced, and the NO and volatile almost simultaneously reached maximum. Taking ammonia as the reducing agent, this paper studied the effect factors and additives of SNCR technology in electric heating reactor. The results showed that the right temperature window was in the range of 8751000℃; the normalized stoichiometric ratio was 1.5; the initial NO concentration and O2 concentration had little effect on SNCR in the actural operation; the CO, CH4 and H2 reduced the best reaction temperation; CO and CH4 had little effect on reducing maximum de-NOX efficiency, but H2 was the opposite. CO and H2 made the temperature window narrower, but CH4 widener; CO, CH4 and H2 reduced the amount of NH3 slip. Considering the various factors, CH4 was the best appropriate additives.Using the solide phase mathematic modeling–FLIC and gas phase modeling–FLUENT, this paper numerical simulated the characteristics of bed combustion and over-bed combustion. The results of numerical simulated were compared with actual operation data, and verified the reliability of the mathematical model. Furthermore, this paper calculated the effect of grate speed, rich- oxygen atmosphere and moisture content on combustion. The results showed that with the increasing of grate speed, the position of volatile starting emission was farther away from the fuel inlet, the gas temperature reduced, the amount of NO formation and CO formation were increased; with the increasing the moisture in waste, the gas temperature increased, the CO concentration and NOX concentration increased but O2 concenctration reduced.This paper studied nozzle arrangement and optimization of SNCR technology, including nozzle arrangement, number of jet, location and speed. The results showed that the suitable area of SNCR reaction located under the furnace arch where the gas flows gradient is larger and velocity more uniform; under the furnace arch, 4 jet were arranged in front and back furnace wall, 2 jet in left and right funace wall, jet speed was 80 m/s, the reducing agent and gas mixed well and got higher de-NOX efficiency.To study the whole life cycle environment assessment of the SNCR technology in a waste combustion plant, this paper used the LCA method. The assessment included energy comsumption and environment assessment. The results showed that the emission in SNCR operation process was maximal; for energy comsumption, the material product process was the main contributer. The environment load of SNCR technology was 4686 PET2000, acidification and nutrient enrichment reduced 470PET2000 and 874PET2000 respectively.To assess of technical and economic of SNCR technology, this paper dynamic calculated annual cost of de-NOX equipment in a waste combustion plant and main effect factors on technical and economic indicator. For investment, the results showed that the purchase cost was the main contributor in all kinds of investments, and reached 82.91%; for annual cost, the cost of reducing agent was the main contributor, and reached 31.8%; the annual cost of SNCR technology was 1.3393millon yuan, NOX removal cost per ton was 8542.95yuan. With the increasing of number of utilize hours, the annual cost increased linearly, while the cost of removal unit NOX reduced; with the increasing of reducing agent cost, annual cost and removal unit NOX cost increased linearly; with the increasing of fine fee, both annual cost and removal unit NOX cost reduced. |
PDF Full Text Request