An Analysis of the Influence of Protective Films on the Inner Surfaces of CCPP Headers and Steam Pipelines on Their Thermal Stress State

At present, the main attention of researchers is paid to the deterioration of heat transfer when heating the outer surface of the pipe with the liquid or steam, flowing inside it, in the presence of films or deposits on its inner surface. However, when pipe is heating by heat carrier medium, flowing inside it, film on the inner pipe surface serve a dual protective function, protecting the pipe from corrosion and reducing its thermal stress. The article represents the results of the computational analysis of protective films influence on the thermal stressed state of headers and steam pipelines of combined-cycle power plants (CCPP) heat-recovery steam generators at different transient operating conditions particularly at startups from different initial temperature states and thermal shock. It is shown that protective films have a significant influence on the stresses magnitude and damage accumulation mainly for great temperature disturbances (for thermal shock). Calculations were carried out at various thicknesses of films and assuming that their thermal conductivity less than thermal conductivity of the steam pipelines metal.

Energy recovery of solid waste disposal in Russia,State of the Art and operation experience

For Russia,there is no alternative way of a civilized solution to the problem of municipal solid wastes(MSW):through combustion(energy utilization)to complex processing.The government of the Russian Federation in 2017 adopted some decisions aimed at thermal processing of MSW.The order defines the construction of renewable energy facilities on the basis of MSW with a total electric capacity of 280 MW in Moscow region and one object with an electric capacity of 55 MW in the Republic of Tatarstan.In Russia,only three plants where the energy potential of MSW is converted into electricity were built.The results of the operation experience of fluidized bed furnaces for MSW incineration at Rudnevo plant in Russia are done.The main problems were connected with ash properties,deposit formation,and corrosion of superheater tubes.Also,the data of mathematical modeling of dynamic behavior near gas burners,chemical composition and material balance of solids,and the influence of secondary air injection on NOx formation are given.A special test rig was designed for the investigation of the corrosion mechanism.Also,the main corrosion factors(temperature of the tube surface,rates of O_(2),HCl,SO_(2),and H_(2)O in flue gas,contains chloride and alkali metals in deposits)were found during the tests.Experience of energy recovery from waste incineration of pulp and paper mill plants is presented.Considerable attention is paid to improv-ing the efficiency of waste incineration and bed particle agglomeration.Special experiments were carried out to optimize the bed drain flow rate.The influence of secondary air supply improvement on mixing with the main flow and boiler efficiency is given.Semi-empirical three-zone method of engineering heat calculations for fluidized bed furnaces of biomass boilers was proposed to predict both the value of outlet furnace temperature and the value of fluidized bed temperature.The method based on empirical values and relationships of the share of heat release in fluidized bed zone.