TECHNICAL ARTICLES BY THERMIX
The following is a collection of abstracts of various articles and lectures presented
by Thermix staff on the topics of combustion and heat treatment. To obtain a
complete copy of any of these articles please
e-mail
us your name, e-mail address, and the article title.
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4.
PAPER GIVEN AT THE WIRE SHOW IN ATLANTA
(Combustion Systems In The Wire Industry)
(How To Make Money, And Comply With Clean Air Regulations)
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The kiln is often the central piece of equipment in any operational plant making
industrial ceramics, whether these be house bricks, high temperature refractories, or
industrial ceramics. The kiln will often be the critical component dictating the final
quality of your product, notwithstanding upstream or downstream processing. It has an
impact on your operating costs as measured by rates of scrap and specific fuel consumption
measured as a function of each component produced. However, for all its importance it is
often the piece of equipment that is least understood. When kiln related problems surface,
they are often perceived as mechanical problems occurring at high temperatures. The
purpose of this talk today is to introduce you to some of the problems which we commonly
see and to attempt to give you some of the tools which may be useful when you are
discussing kiln related problems with consultants, suppliers and your often overstressed
operators.
This talk will introduce some of the ideas related to gas flows and temperature
uniformity, and will then stray into areas concerned with practical equipment choices and
some of the trade offs which have to be made when choosing the design for high temperature
kilns.
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Operational furnace equipment in the field of non-ferrous metal recycling is
discussed with particular emphasis placed on furnace design, modes of heat transfer and
methods of control. Processing costs, melt temperature uniformity, melt segregation,
homogeneity, operating considerations, mechanical agitation and metal losses are also
briefly covered.
Thermal desorption and fume incineration are also briefly covered together with
discussion of ways in which waste heat can be returned back to the process.
Some novel technologies including ceramic immersion burners RCB's and plc control
systems are also introduced and discussed in the context of achieving low specific energy
consumption and enhanced melt property control.
Finally there are some general comments about furnace refractories, burner selection
and placement in some real applications.
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The opening remarks concern the environmental effects of changing atmosphere
composition and introduces the idea that companies should be fiscally encouraged to heat
industrial processes as cleanly and efficiently as possible.
Strategies including control system improvements; plc ratio control; pulse control are
evaluated by example using a galvanizing bath, an Aluminum melting furnace and a large
forge furnace as examples. Possible safety code problems are highlighted with particular
emphasis on the use of PC and Plc based control systems. The pre-heated air burner is
discussed and simple control systems evaluated and recommendations for ways that the
standard control system can be improved for use with a recuperative system. Examples
including a small ceramic tube recuperative burner, a concentric tube self recuperative
burner and a regenerative burner are introduced and discussed.
The chemistry of NOx formation is briefly illustrated and ideas for reducing NOx in
industrial equipment is explained with the help of some laboratory and field experience
gained by Hauck Pa. The economics of NOx control and the effects of flame shape control
flue gas recirculation and air dopants are considered.
Finally the impact of possible legislation on the economic performance of some high
temperature furnace equipment is reviewed and the way uncertainty has resulted in a
dilemma for burner supply companies.
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4.
PAPER GIVEN AT THE WIRE SHOW IN ATLANTA
(Combustion Systems In The Wire Industry)
(How To Make Money, And Comply With Clean Air Regulations)
The paper reviews combustion technology in the wire industry and discusses methods of
NOx control that have become available over the last two years together with some of our
plans for the future. Immersion burners and Low NOx radiant tube burners are reviewed.
NOx reduction starts with good control and careful tuning of the combustion system,
using accurate gas analyzing equipment. There are some opportunities offered in the
amended clean air act that offers some financial incentive to Opt In to the Clean Air
Regulations.
Four different types of Low NOx burners have been described and their performance in
applications as different as drying to heat treatment have been discussed. Using different
technology, NOx emission levels less than 40 ppm can be generated, which compares to 120
ppm for most conventional systems and applications.
Single digit NOx emissions are possible but only by using the most sophisticated
designs, using multiple methods of NOx control. Three applications specific to most wire
producers have been reviewed. Pulse firing a galvanizing bath fitted with high velocity
burners will promote temperature uniformity and will reduce NOx.
Radiant tubes may be modified to produce better than 50% NOx reduction plus the extra
advantage of better temperature uniformity and lower turndown. Low NOx Ceramic Immersion
Tube Burners are under test and produce tube lives similar to the Burns Burner.
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The purpose of this paper is to provoke some thoughts and ideas, in regard to the way
systems are heated in galvanizing plants. I was asked specifically to discuss some
technologies that have been developed and are in use on the other side of the Atlantic. I
will therefore be borrowing some ideas from Europe and attempting to present these in the
North American context.
The major difference between Europe and North America is the cost of the fuels used to
heat galvanizing equipment. In Europe it is not uncommon to see gas costs as high as 2
times the price we pay here. Some countries are still able to remain competitive as labour
costs are significantly lower. However because of the high cost of fuel, Europeans tend to
look to innovative solutions to ensure that every last joule and BTU is applied to the
best possible effect.
I intend to address my remarks primarily to baths of zinc which are contained by a
steel tank to which heat is being applied to the exterior of the tank by some kind of
heating system. It is easier to deal with the zinc tanks first as it is from these pieces
of equipment that the highest grade of recoverable heat is emitted.
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This paper is intended to introduce a number of ideas which will help you to understand
the some of the options that are available when choosing or specifying a combustion
control system.
The first section will deal with issues related to air quality or emissions control.
The next section will deal with the use of computerized control systems and some of the
statutory limitations that are imposed on the use of this technology. Finally there will
be a short discussion of some of the changes we have been making over the last few years
to make efficient and clean technologies available to the market.
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