Study On The High Temperature Corrosion Of Heating Surface During Biomass Combustion

Biomass is a clean, renewable energy, and its carbon dioxide emissions is zero because the emissions from the burning equal to the fixed carbon dioxide in photosynthesis. Biomass combustion technology for power generation is the most mature and widely used, but biomass contain large amounts of potassium, chloride and other alkali metals, burning biomass fuels often lead to high temperature corrosion problems, seriously affect the promotion of biomass boiler performance parameters and boilers long-running safety and stability. In order to study the process of temperature corrosion problems in biomass combustion, to choose the right high-temperature corrosion-resistant materials for biomass power plant boiler. This paper analysis the project and simulates the atmosphere on biomass boiler super-heater area to study the high temperature corrosion processes and mechanisms.First of all, the high temperature corrosion problem of a biomass power plant in Guangdong were analyzed. Simulating condensate on boiler pipe section surface in stop period, we conducted exploratory experimental study of the liquid chlorine ions corrosion and found that the boiler pipe material of biomass power plant has a strong liquid chlorine ions against corrosion. In view of the deposition and corrosion problems on the high temperature heating surface, through sampling, testing and other investigations we found that:the super-heater sedimentary has typical inner, middle and outer layer structure. The inner layer in direct contact with the metal thereby contain iron, nickel metal oxides; the middle layer is high levels of alkali metal salt; the outer layer contain alkali metal salt and a small amount of inert bed material particles. The deposition on heating surface is KC1salt layer with a certain thickness, high temperature corrosion of metals has begun to gradually erode into the matrix inside, and continue along the grain boundaries inward development.Secondly, a study on high temperature corrosion test of20G,12Cr1MoVG, Super304, SUS316, TP347H, HR3C steel had been carried out in a temperature range of550～700℃, simulating the atmosphere on biomass boiler super-heater area. By measuring the weight gain of the sample, the corrosion characteristic curves had been obtained. Corrosion morphology of the sample, element content and composition of corrosion products were analyzed by using the scanning electronic microscope, energy spectrometer and X-ray diffraction meter. To study a chemical mechanism, this article also probes into the corrosion reaction between Cr2O3, the main component of passive film and KC1under a high temperature environment; analyzes the material composition after reaction with the help of X-ray diffractometer; and studies the influence of the compactness degree of passive film to the corrosion property of KC1.Test demonstrates that at high temperature, the order of KC1corrosion resistant steel performance at high temperature is HR3C>TP347H> Super304> SUS316>12Cr1MoVG>20G. Temperature and the deposition amount of KC1have an important effect on the high temperature corrosion; KC1has a reaction with oxide passivation layer on alloy steel at high temperature, directly destroying the protection of passivation layer and thus accelerating oxidation corrosion. The Cr2O3, passive film subject of austenitic stainless formed under high temperature, can react with KC1to form potassium chromate and release chlorine, and damage the passive film as a result. The higher density of passive film, the greater the resistant to KC1high temperature corrosion will be.