Full-Scale Investigation of Dry Sorbent Injection for NOx Emission Control and Mercury Retention

An innovative dry SNCR method realized by a sorbent injection applied to a stoker furnace is presented. The process is based on urea powder admixed with halloysite, an aluminosilicate clay mineral. Field tests were performed at an industrial stoker hot water boiler of 30 MWth capacity. A unique nozzle design for injecting powdery sorbents into the combustion zone was implemented. The base NOx emission without SNCR was determined to be 365 mg/Nm3. During the reference test, the emission was reduced to avg. 175 mg/Nm3, which produces a NOx reduction of 52%. NH3 slip in the flue gas was stable and did not exceed 2 ppm. Combining urea and halloysite powders leads to a number of positive effects; not only is NOx emission reduced to values typical for wet SNCR, but also a significant, over ten-fold increase in the concentration of adsorbed mercury in fly ash was observed. When confronted with wet SNCR, dry SNCR has no adverse effect on boiler efficiency because it does not increase the stack heat loss. The presented method can be used in any small- or medium-scale furnace, including waste-to-energy units or medical and hazardous waste incineration units.

Optimization and Security of Hazardous Waste Incineration Plants with the Use of a Heuristic Algorithm

The amount of generated waste, which increases every year, is a serious problem of the modern world. In particular, attention should be paid to hazardous waste and methods of its disposal. One of the most used in this context is thermal treatment in dedicated incinerators equipped with a rotary kiln. Conducting the process requires, inter alia, supplying the furnace with a batch of batch material with appropriate parameters. Improper operation in this regard may cause negative environmental effects and operational problems. The key here is to select different types of hazardous waste and compose batch portions. The paper presents an application that optimizes the work of waste incineration plant operators. At the same time, this tool can be described as ensuring security at this stage of the process. The application implements an ant colony algorithm that selects the optimal solution to the problem, which has been formulated here as the types and masses of the batch mixture components with given parameters. The application has been tested in the laboratory and real conditions with satisfactory results.

Mechanical Behaviour of Cement-Bound Gravels by Experiment-Based 3D Multi-Scale Modelling: Application to Non-Hazardous Waste Incineration Bottom Ashes Aggregates for Use in Road Engineering

This paper presents a hierarchical multi-scale modelling approach devoted to investigating the mechanical behaviour of cement-bound gravels. Material studied is based on Non-Hazardous Waste Incineration (NHWI) bottom ashes. The elastic moduli of NHWI particles have been previously determined by an original indentation campaign never conducted so far on these types of aggregates. The results of the experimental campaign serve as input data to the developed numerical strategy. The modelling is based on the definition of Representative Elementary Volumes (REV) considering all the heterogeneities of the material. The "virtual laboratory" set up made it possible to determine the mechanical parameters characterizing the gravel treated with 3% of cement. The high value obtained of the internal friction angle (76 °) gives the material a good bearing capacity. The classification in mechanical classes 3 and 4 when the Young's modulus of the NHWI particles varies from 20 to 80 GPa proves the feasibility of the reuse of this type of industrial by-products in this sector of activity. The present modelling approach is validated by means of comparisons with experimental results of the literature.

Original Experimental Campaign of Indentation Instrumented on Aggregates of Non-Hazardous Waste Incineration Bottom Ash to Study the Heterogeneity of their Rigidity

An extensive experimental work of instrumented indentation on isolated particles of Non-Hazardous Waste Incineration bottom ash (NHWI) is presented in this paper. The aggregates studied come from the Garenne quarries at Vignoc (Brittany, France). Two spherical tungsten carbide indenters of respective 0.5 and 140 mm radius “R” were used for test series “A” and “B”. The particles studied have diameters ranging between 20 and 25 mm. With a 0.5 mm radius indenter, average reduced elastic moduli ranging from 15 to 68 GPa were found. An average reduced elastic modulus of 15 GPa was found with the 140 mm radius indenter. The experiments made it possible to highlight the particular heterogeneity that characterizes the rigidity of the types of aggregates studied.