learning from history october 2011

MCST Third Foundry colloquium 26/27th OCTOBER 2011

Learning from US history

The aluminium foundry industry energy conservation imperatives.

Dr A E Paterson – Aluminium Federation of South Africa


Outline:

IntroductionThe foundry industryThe aluminium industry 1976 energy conservation workshopFurnace efficienciesWhat is the local foundry industry doing at present How does the foundry industry pay for itConclusion


Introduction

• Energy using fossil fuels leads to global warming

• The available energy crisis is real and it is here. Energy costs have doubled over he past four years and are likely to continue this pace.

• We are faced with environmental consequences, energy rationing, and increasing cost of energy

• We are faced with carbon taxes and clean air and water environmental legislation

• Equipment exists that is more energy and environmentally efficient

• Examples exist of foundry rearrangement to meet similar challenges

• Renewal cost of amortised equipment is likely to be impacted on by the current trading and borrowing conditions.

• What short to medium term approaches make sense?


Energy sources used are not restricted to electricity

They also include natural gas, lpg, heavy and light oils and coke.

Measured against reliability of supply, where possible, multi source energy could be attractive.

RSA foundries measured in three independent pilot studies showed low efficiency relative to world leaders - as may be expected for a high capital cost, low energy cost country.

The change to a high capital/cost high energy cost base brings challenges; local pilot studies have indicated capacity of improvement.

Measured against increasing cost of energy, energy can be saved. The cost benefit ratio increases with greater savings. Embedded capital equipment requires consideration.


The electrical energy problem – not enough, incorrectly priced


The graphs assume a 4% annual supply growth to underpin a planned 6% annual growth in GDP. This implies a strategic move from supporting primary industry to supporting down stream value adding industry.

To maintain surety of supply Eskom require a minimum of a 10% buffer to allow for foreseen and unforeseen maintenance requirements.

Savings are essential if the country is to avoid a crisis in the next few years until new supply comes on stream – Madupi has been delayed.

Also - Existing power stations come to end of life in the mid 2020’s

Pricing – the electricity price, previously kept artificially low and not reflecting the replacement value of the capital equipment, escalated dramatically doubling every four years as Eskom seeks to significantly finance expansion costs from current cash flows.


Demand reduction options

Supply constraints

Country image

Climate change

Financial sustainability

S A Economy

Probability of desired outcome

Load Shedding

Rolling Blackouts

Prioritisation of new load

With pcp

Intensified “energy efficiency” DSM

good but slow

Severe NMD penalties

Suspend new applications

Short term

Power conservation programme Positive

impactNeutral Negative

impact


Four main option types to effect behaviour change were considered:

Load shedding - unfair and unsustainable. Substantial price increases - useful in conjunction with rationing Demand supply management programme – useful alongside . rationing Power conservation programme - Rationing the right to purchase . (of supply) seen as best option

PCP is the core underpinning principle linked to pricing penalties


The (electrical) energy conservation scheme targets a 10% energy saving phased in over three to four years with a 50% saving in the first year.

Failure to meet the 10% savings targets was planned to result in punitive energy tariffs in the form of a steeply inclining power curve block tariff approaching and exceeding the replacement value cost of electricity. This approach is in the background. The decline in growth has given breathing space.

A phase in period of about two years was anticipated.


Outline:

Introduction The foundry industryThe aluminium industry 1976 energy conservation workshopFurnace efficienciesWhat is the local foundry industry doing at present How does the foundry industry pay for itConclusion


The foundry industry is a base industry.

Castings form the basis of many products in many markets

The value chain involves casting, machining, manufacture and packaging giving added value of the order of 50x at industry level.

Energy is required to melt and cast metals

Pilot foundry studies show RSA to be a relatively inefficient energy user in both the iron and aluminium sectors. This is to be expected bearing in mind the existing capital equipment decision circumstances. There appears to be considerable opportunity for up to 50% saving

Energy rationing and sharply increasing price forms a challenge

The 1970’s USA crisis that followed energy rationing and price increases will be explored to gain insights.


Associate Industries

Inputs /process

Value chain

Bought in cost R/kg

Inputs/ product

Value R/kg Man-hours/kg

Replace after market

Finished component

Pirate

OEM

OEM Value

R313

R1000

R350

Packaging/ tpt/ inventory

Packaging Packaging 3 Plastic / card /

Board

R30 OEM

R155 aftermarket

560

Bought in

hang on parts

Cap equipt Manufacturing 1

65

Fitted parts to complete

R200 470

Final shape Cap equip/ maint/tools/lube

Machining

Consumables

8

1

R130

Casting operation

Cap equipt / tools / maint

Casting 3

6

Equipt / maint

inserts.

R90

Secondary smelter

Capital equipt / tools / lubes

Specification ingot

21 R21

Metal merchant Sorted scrap R11

Scrap collector Raw scrap R6

Scrap to final product represents a 60 times value addition to the collected unsorted scrap metal The casting is a carrier that supports other industries and provides job opportunities

Value streamfrom scrap throughvarious inputs –

More jobs/ton


Pilot studies show RSA to be a relatively inefficient energy user:

The pilot study was a screening assessment based on a three year input of records of two purchases:

Energy of all forms purchased – recorded in volume units of purchase and reduced to calorific value in terms of joules. (1J= 1ws)

Net purchase of metal (net of scrap sold – excluding dross)

The tacit assumption was that the quantity of metal on the shop floor and in storage remains more or less constant.

This gives the energy required to produce one unit of sold product 60% was taken to represent furnace demand.

This is an approach that can be used by any foundry to assess own energy costs and compare these to the 700kWh/ton for melting suggested.


Outline:



Foundries are capital and energy intensive

The major energy-using equipment, furnaces, last a long time.

Capital choices reflect specific foreseen circumstances made at the time of choice. The three issues affecting choice are the interplay between the costs of capital and energy and whether to choose for batch or continuous processes

In a cheap energy, expensive capital country, the natural bias has been towards less energy efficiency (as was the case in the USA before the 1973 oil crisis).

In expensive energy, cheap capital countries energy saving equipment is used. The technologies exist.


Crucible furnace – batch process


Crucible furnace - note lid

Molten metal energy loss reducedStill energy loss through flue


Crucible furnace - note lid

Eastern foundries have adopted crucible furnaces by trapping flue gas to pre.heat the charge

Fresh air added to to reduce flue gas temperatures to around 400oC

Closed system design3 Stage Furnace

Charge preheat shaftMelting on ramp adjacent to holding chamberHolding in separate chamber with separate controls

Continuous processDoors are the width of each chamber => easy cleaning


Modern Striko furnace


Striko furnace


Note that energy is not only used for melting

It is also used for holding and for casting

Holding – the structure may lose heat through the foundations, . the walls of the flue. - holding practice may hold molten metal for too long.

Casting – too large a runner and riser system requires extra . metal melted and remelted - poor practice which results in a high defect ratio . requires extra energy in remelting. - impact of poor metal quality or temperature

These are the controllable aspects.


The question is both what to do and in what order.

The majority of energy (about 60%) is used of melting and holding

The majority of energy use depends on the type, insulation and installation of the furnace. Some aspects are uncontrollable, some may be modified.

Energy in the form of heat is lost through inefficient conversion, through furnace walls and through the flue.

Looking to similar energy challenge circumstances the USA response after the 1973 oil crisis will be considered

Energy availability declined rapidly and prices accelerated rapidly.

The aluminium foundry industry energy conservation

imperatives.

How much energy do we theoretically require to melt aluminium and steel starting at day temperatures?

Consider physics laboratory - Heat from day temperature (specific heat) - melt – change from solid to liquid (latent heat)

Material Melting temperature

Specific heat MJ/kg oK

Energy to heat from 20oC to melt T MJ/kg

Latent heat MJ/kg

Total energyMJ/kg

Aluminium 630oC 0,900 549 396 945

Iron/steel 1460oC 0,448 645 267 912

Aluminium Laboratory 945 MJ/kg This implies 261 x 10-3 MWh/ton

about 1,8% of 14,2 MWh/ton for primary smelting)Note that preheating aluminium to 400oC takes about half the energy


This is not realistic. How much energy do we actually require to melt aluminium and steel starting at day temperatures?

In practice:• We need to heat and to retain heat in furnaces • We lose heat from furnaces• Batch production is less efficient because furnaces are not used continuously• We lose a variable percentage of metal for various reasons (effectively a higher energy use per unit recovery) • The conversion of energy to heat is not 100% efficient• charge appropriateness, scale and cleanliness energy to melt will influence energy needs• Recycled castings, feeders and risers reflect metal previously melted that requires remelting affecting the energy required per ton of sold product


This is not realistic. How much energy do we actually require to melt aluminium and steel starting at day temperatures?

If we want the liquid metal to be 100oC > melt temperature (adds 10% to Al requirement to 0,286Mwh/ton, 5% to steel to 0,264MWh/ton) The best known practical energy use is around 0,45 – 0,55 MWh/ton

In practice consider 5% of primary smelting i.e. 0,7MWh/ton as a target

for aluminium (World”s best practice 0,5MWh/ton)For same efficiency for steel also consider 0,7MWh/ton (Wbp 0,54)


• Where does the (60% of) energy go?

All energy sources - net energy inat factory gate

Energy conversion eg harmonic correction of power factor ,Burn efficiency

Energy into furnace

Energy conversion,Energy loss

Energy lossInto foundations

Energy loss metallurgyMetal qualityToo hotProcess returnsMelt loss

Energy loss can be divided into: required possible improvement unavoidable loss

Energy loss – management Transmission loss, leaksEnergy loss – flue (recovery)Energy loss - housekeepingEnergy loss- Furnace wallsEnergy loss - holding time

Energy needed to heat and melt metal.

Ignores coal energy conversion and electrical transmission loss 83% loss

Energy needed to heat furnace

Charge effects


Outline:



The early 1970’s USA industry had generally chosen equipment that assumed cheap plentiful energy in the form of cheap oil.

The energy crisis that faced the USA at that stage is not dissimilar to that faced locally today.

The crisis reflected a shortage combined with rapidly rising prices.

A 1976 aluminium foundry industry workshop was called to concentrate on metal melting as both the most energy intensive and the one that offered most potential for returns.

The focus was on retrofitted solutions.


US oil production peaked in 1973

In October 1973, as a result of Yom Kippur War tensions, OPEC members stopped exports to the USA

Oil prices rose from $3/barrel in 1972 to $12 in 1974

By the second oil crisis in 1979 prices had risen to $35/barrel an over ten times escalation over seven years!


Response

It was realised that the era of cheap oil had passed.

The Energy Department, later to became a cabinet office, was created.

(The drive for light weighting of cars grew from the energy crisis as transport in most western world countries uses more than half the energy USA 56% in mid 70’s.)

The aluminium industry energy conservation workshop was held in 1976 to share lessons learned.

The conference focussed on two aspects;

• Increased energy conversion efficiencies – improved burner . efficiency - furnace preheating (In South Africa we could add improved power factor conversion for Electricity)

• Avoiding heat loss through appropriate housekeeping

• Heat recouperation Energy regained is energy saved This can be used to preheat the charge, . to preheat the furnace air, etc

The focus of this talk is on heat recouperation


A major factor that needed to be taken into account was the reality of embedded capital equipment.

Within this reality the concern was on retrofitted solutions to recover heat.

Two systems were discussed: Recouperation through radiation Recouperation through Heat wheels.

Typically the heat captured was cooled to about 400oC by dilution with ambient air before use and used to preheat (aluminium) charge metal or to preheat furnaces or burner air.


In the recuperator the heat is transferred by different modes:

• Conduction within metals or other bodies,• Convection between gas or air and solid bodies. The higher the temperature differential, the better the rate of heat transfer. The faster the gas or air moves across or along the tubes or other solid bodies, the higher the heat transfer rates. • Radiation between solid surfaces – transfer rates increases by the fourth power of the temperature differential between the two surfaces. • Gas radiation between certain gases and solid surfaces – transfer rates increase by about the fourth power of the absolute temperature difference between the gas and surface. Heat transfer also increases with higher amounts of C02 and H20 and with large gas volumes.

However, radiation is not very effective at low temperatures of either the surfaces or the gases.


(Gas) Radiation Recouperators (1). • Consists of two concentric large diameter cylindrical metal shells welded together at each end by way of air inlet and outlet headers. • Exhaust flue gases from the furnace at some 1 100oC passes through the inner shell while combustion air passes through the narrow gap between the shells. • Heat from the exhaust flue gas is transmitted to the inner shell (heating surface) mainly by gas radiation which transfer may be as high as 75% to 95% of the total heat transferred.


(Gas) Radiation Recouperators (2). • Additional heat is transferred by convection due to the slow flow of exhaust flue gas through the recuperator as well as by radiation from the hot inner shell into the recuperator. • On the outlet side of the heating surface of the recuperator the combustion air passes with high velocity to dilute the air and absorbing heat from the inner shell to achieve an about 400oC output flow. • This is used to preheat the charge.


Heat Wheels (1)

• Hot exhaust gases are directed through one side of the slowly rotating heat wheel, absorbing the beat. Cold air flows through the other side in the opposite direction, stripping the heat put into the wheel with efficiencies up to 75%. • The manufacture of the heat wheels is a challenge – consider metal and ceramic solutions• Metal wheels have expansion and contraction (causing distortion) drawbacks for high temperature applications. The seals are difficult to maintain.


Heat Wheels (2)

• The geometric stability of the ceramic wheel at high temperatures provides an answer to critical high temperature sealing. This very low expansion at temperature allows the use of “close gap” ceramic seals. The seals are also low expansion material. • Ceramics are generally more resistant to corrosion from chemical attack than most metals. They have a high efficiency heat exchange because the low thermal conductivity and high specific heat provide a greater heat capacity and smaller energy loss between the hot and cold face than similar metal heat recovery units.



Outline:



Most 800oC to 1500oC high temperature furnaces are inefficient

Thermal efficiencies can be high but can be as low as 10% because as the heating or melting of metals requires high waste gas temperatures leaving the furnace makes it difficult to design.

Typically over 50% of the heat input may be lost through the flue

If this could be recaptured, it could be used to preheat combustion air for burners (fossil fuel fired) or to preheat charge metal.

The focus on this presentation is on heat trapping in the flue and recouperation.

Within the overall energy flow we need to understand what is needed, where improvement is possible and where loss is unavoidable


• A foundry requires energy for melting

• Most energy is required for melting – how much do we need.

(Theoretical calculation without melt loss, without furnace heating: Specific heat aluminium solid 900J/kgC Specific heat aluminium liquid 944J/kgC Latent heat of fusion 3,96 E5J/kg Heat solid from day temperature to melting /kg 900 x (660oC-20oC) = 5,76E5J/kg (54%) (30% to 400oC) Melt/kg = 3,96E5J/kg (37%) Heat liquid to casting temperature of 760oC 944x(750oC -660oC) = 0.85E5J/kg (8%) Total = 10,57E5J/kg = 10,57E5Ws/kg = 10,57E5/1000x3600 = 0,3kWh/kg electrical consumption)

Best world practice 0,45 – 0,55 MWh/ton


• Where does the (60% of) energy go?

All energy sources - net energy inat factory gate

Energy conversion eg harmonic correction of power factor ,Burn efficiency

Energy into furnace

Energy conversion,Energy loss

Energy lossInto foundations

Energy loss metallurgyMetal qualityToo hotProcess returnsMelt loss

Energy loss can be divided into: required possible improvement unavoidable loss

Energy loss – management Transmission loss, leaksEnergy loss – flue (recovery)Energy loss - housekeepingEnergy loss- Furnace wallsEnergy loss - holding time

Energy needed to heat and melt metal.

Ignores coal energy conversion and electrical transmission loss 83% loss

Energy needed to heat furnace

Charge effects


Outline:



A DST grant led to a forty (twenty four in practice) foundry by foundry five part fact base energy study was undertaken to :

1)Ascertain the quantum of energy input to the factory (in joules)

2)Survey the use of that energy in the foundry process up to fettling

3)Analyse the top 80% of energy usage for each foundry to determine efficiency of use

4)Propose possible solutions on a cost benefit scale. (Many housekeeping type solutions are very low cost.)

5)Use the data to develop and publicise a country recommendation


The twenty four foundries were offered consultation assistance to reduce energy demand.

The overall results were positive in terms of reduced costs and reduced energy demand.

Partnering has been developed

An energy committee has been formed

A waste sand committee has been formed

The current EffSAFound project is underway


The new reality of energy rationing and increasing cost of energy prices warrants serious attention.

New more energy efficient equipment exists.

Retrofit solutions are well understood and available

The difficulty at present is cash flow.

The combination of the world economic crisis and tight lending conditions by the banks begs the affordability questions.

On the other hand if foundries do not invest into energy efficiency for the future, increased prices (and penalties) come into play.

The dti is offering financial and other support to the foundry sector


Looking to overseas practice and a medium to long term solution one is struck by the way in which foundries have been rearranged to route and bundle energy intensive equipment and needs together to gain best benefit.

Similarly considering other environmental legislation, clean air and water legislation, the realisation that cleaning processes are volume related has led to concentration (bundling) of environmentally sensitive activities.

The overall point is the need to develop a longer term strategy to manage energy and environmental matters which looks beyond replacing one piece of equipment with another towards a more integrated approach to energy saving and environmental responsibility.

CDM is a process through which developed countries can fund developing countries to implement emission reduction strategies that promote sustainable development, are measurable and additional, and do not divert funds from government development programmers. Current value ϵ23x0,9/MWh. (0,9MwH/CO2e) Minimum criteria 10 000 tons CO2e per annum.

As individual foundries probably do not meet the minimum volume criteria a foundry group approach may be required.


The foundry sources of energy are all fossil fuels.

The contribute to global warming. (1 kWh = 1 ton CO2e)

The RSA government is proposing a carbon tax on producers and users of fossil fuels – this will further affect the foundry cost base

The 1997 Kyoto protocol Clean Development Mechanism (CDM)


Outline:



Conclusion

• The energy crisis is real and it is here.

• We are faced with energy rationing and increasing prices.

• Short term change focusing on favourable cost/return solutions can save about 50% of energy use – avoid, mitigate, manage, monitor.

• Equipment exists that is more energy efficient

• Whilst renewal cost of amortised equipment is likely to be impacted on by the current trading and borrowing conditions the dti is offering assistance. The IDC is offering assistance.

• The CDM mechanism may assist but will need to be bundled.

• The parallel clean air and water environmental concerns suggest the need for a complete rethink of foundry layouts towards bundling.


Conclusion - thoughts

• The mantra measure, measure, measure has limitations

• There is no doubt about the need to manage

• To manage one needs relevant, sufficiently accurate information

• To glean the information, one needs relevant, sufficiently accurate, available and timely data.

• To gather the data one needs to measure that which is measurable and relevant

• To gain reliable data, one needs to know how to interpret and use measurements.

• The opportunity for energy saving is well worth pursuing.

MCST Third Foundry colloquium 26/27th OCTOBER 2011

Learning from US history


Dr A E Paterson – Aluminium Federation of South Africa

learning from history october 2011

Business

aluminium industry

local foundry industry

foundry rearrangementto

introduction energy

energy rationing

energy costs

energy sources

increasing cost of energy