Furnaces, industrial muffle furnace

In the ceramics industry, muffle furnaces are typically used for batch sintering [B.97]. 

Indirect-Fired Equipment (Fired Heaters) Indirect-fired combustion equipment (fired heaters) transfers heat across either a metallic or refractory wall separating the flame and products of combustion from the process stream. Examples are heat exchangers (discussed in Sec. 11), steam boilers, fired heaters, muffle furnaces, and melting pots. Steam boilers have been treated earlier in this section, and a subsequent subsection on industrial furnaces will include muffle furnaces. 

The determination of metal purity and the elemental composition of alloys is of utmost importance to the metallurgical industry. Microwave-assisted digestion is often well-suited to metals and metallurgical samples that pose no difficulty and dissolve readily and safely with the aid of microwaves [148,186-196]. For example, hydrofluoric acid can be used in closed vessels to digest silicate matrices and stop the hydrolysis of refractory elements without loss of volatile fluorides or passivation. After cooling, boric acid can be added to complex unreacted hydrofluoric acid [14]. The solid sample itself may absorb microwave radiation, thus creating a heated surface on which the acid or acids can react. Microwave muffle furnaces are commercially available [197] based on oven linings made... 

The two most important applications of batch sintering are in the ceramic and powder metal industries. Muffle, bell, elevator, or pit type furnaces are used. As shown in Tab. 9.1, the processes occurring during sintering are somewhat different for ceramic and powder metal parts. 

Despite its comparatively high price, silicon carbide is a significant refractory product due to its exceptional properties, such as its high thermal conductivity, high hardness and mechanical strength. It is used in zinc distillation kilns and in the manufacture of muffles, capsules and kiln furniture for the clay ceramic industry (see Section 5.5.4.7.2). In recent years silicon carbide has also been used in the refractory linings of blast furnaces and utilization in other sectors of the steel producing industry is in evaluation. 

In the manufacture of semiconductors, monolithic circuits and integrated circuits for the electronics industry, the use of fused quartz is widespread for plumbing and diffusion furnace muffles. The need to prevent product contamination makes this choice mandatory. 

Ceramic and electrothermics industry Furnaces muffles, supporfs for parts to be sintered Electric furnaces heating resistors... 

---