Seghers Boiler Prism: A Proven Primary Measure Against High Temperature Boiler Corrosion

Abstract

This paper constitutes a follow-up on a presentation at NAWTEC 10 (2001) [1]. It contains novel insights regarding the operation of the Seghers Boiler Prism and its effectiveness as a primary measure against high temperature boiler corrosion in WtE plants. Starting from the currently available fundamental understanding on high temperature corrosion and the main features of the Boiler Prism, the operation as a primary measure is explained. Since the previous presentation, three additional Boiler Prisms were successfully commissioned as a retrofit at a large WtE facility (3 × 705tons/day at 4,700BTU/lb; 110tons/hour steam at 1,450psi, 750°F) in the Netherlands. Together with the previously installed prisms, this brings the combined operational experience from all trains to more than 15 years. The main data and experience of the retrofit project in the Netherlands are discussed and results regarding the performance of the prism are presented in detail. The latter are based both on existing process monitors as well as dedicated measurement campaigns and include: • temperature and oxygen distribution in the 1st radiation pass, • feedback on corrosion rates, • influence on the combustion quality, and • impact on the effectiveness of the mechanical cleaning equipment. The results confirm the effectiveness of the prism as a primary measure against high temperature boiler corrosion and highlight the additional operational benefits.

Energy Recovery from Municipal Waste based on Moving Grate Technology

“…Modern corrosion reducing methods areas follows (according to Grillo, 2013;Lee, 2009;Van Berlo, 2012;Adams et al, 2004):  The selection of appropriate metals for construction of the boiler -i.e. the use of steel alloys with nickel, chromium and molybdenum.…”

Factors affecting energy efficiency of waste to energy plants

“…For secondary air injection there are various designs for maximising penetration of the air jets to all parts of the flue gas stream, for instance a special prism assembly is used in some very large boilers. 10 There are two commercial incineration plants in the world, one in Arnoldstein (Austria) and the other in Sendai (Japan), which use oxygen enrichment of the primary air to increase combustion efficiency and to produce a high quality bottom ash that can be sold for use in the construction industry. The oxygen enrichment process, called SYNCOM, has so far been proved to work with the two large scale plants in Austria and Japan, with the bottom ash meeting the stringent Japanese standard.…”

Combating Corrosion in WTE Facilities: Theory and Experience

“…This reaction can transform chlorine salts into sulfate salts and the released chlorine then reacts with water vapor to form hydrochloric gas. Sulfate salts are less aggressive since sulfate corrosion occurs at higher temperature [12]. In WTE facilities, the character of deposits is mostly affected by feed composition and gas/metal temperature.…”

“…The advantage of the prism is that it can be implemented in new designs as well as in existing plants as a retrofit. For an existing plant, the retrofit project of installing prism was stated to require a rather long plant shutdown [12]. The installation cost of the prism was not provided in the paper.…”

“…Schematic view of vertical and horizontal designs of boilers [3] 3. The Seghers Prism: The Seghers Prism [12] is a prism-shaped tube equipped with several tuyeres through which secondary air is injected into the combustion gases as they rise above the combustion grate. It is inserted horizontally through the center of the combustion chamber at the lower end of the first radiant boiler pass ( Figure 8).…”