Batch Preheat for glass and related furnace processing operations

Energy & ; Environmental Resources, Inc

United States. Department of Energy. Golden Field Office.

关键词: Heat Flux;    Melting Points;    Heat Recovery;    Air Heaters;    Heat Transfer;   

DOI  :  10.2172/816025
RP-ID  :  FG36-01GO11014
RP-ID  :  /GO/11014
RP-ID  :  816025

美国|英语

来源: UNT Digital Library

【 摘 要 】

The objectives that our development work addressed are: (1) Establish through lab tests a salt eutectic with a melting point of about 250 F and a working range of 250 to 1800 F. (2) Establish the most economical material of construction for the screened salt eutectics identified in the first objective. (3) Establish the material of construction for the salt heater liner. Objectives 2 and 3 were determined through corrosion tests using selected metallurgical samples. Successful completion of the above-stated goals will be incorporated in a heat recovery design that can be used in high temperature processes and furnaces, typical of which is the glass melting process. The process design incorporates the following unit operations: a vertical batch heater (whereby the batch flows down through tubes in a shell and tube exchanger; a molten salt eutectic is circulated on the shell side); a molten salt heater utilizing furnace flue gas in a radiation type heater (molten salt is circulated in the annular space between the inner and outer shells of the vertical heater, and flue gas passes from the furnace exhaust through the inner shell of the heater); a cantilever type molten salt circulating pump; and a jacketed mixer/conveyor to drive off moisture from the batch prior to feeding the batch to the vertical batch heater. Historically, radiation heaters, when applied to glass or fiberglass furnace recuperation, have experienced failures due to uneven heat flux rates, which increases internal stresses and spot overheating conditions. Low heat transfer coefficients result in requirements for large heat transfer surface areas in gas to gas or gas to air exchangers. Fouling is another factor that results in lower unit availability and reduced performance. These factors are accommodated in this process by the incorporation of several design features. The salt heater will be a vertical double wall radiation design, similar to radiation air heaters used in high temperature heat recovery. The unit utilizes an inner shell that the furnace exhaust gas passes through: this provides essentially a self-cleaning surface. Utilization of radiation air heaters in fiberglass furnaces has demonstrated that the inner shell provides a surface from which molten ash can drain down. The molten salt eutectic will be pumped through the annulus between this inner wall and the outer wall of the unit. The annular space tempering via the molten salt will promote more uniform expansion for the unit, and thereby promote more uniform heat flux rates. Heat transfer would be via radiation mainly, with a minor convective contributor.