Budget Quotation for an Automatic Aluminium Reduction Cell Thermal Bake System
Our Ref. EA????
 
Further to your recent enquiry and our subsequent e-mail communications, we are now pleased to submit our budget proposal for the design, manufacture, shop testing, packing, supply FCA Dewsbury UK and site commissioning of an LPG fired HCT aluminium reduction cell thermal bake system.
 
Our technology provides the following advantages:
 

• By insulating the pot to form a combustion chamber and by using high velocity burners, heat is transferred to the cathode more uniformly, avoiding hot spots and cracks from thermal shock when liquid bath is being poured into the cell.
• Cell start-up is smoother and pull-up voltages are lower (typically below 10V).
• Cell life can be prolonged through improved preheating.
• Pitch fumes released during the preheating process are largely incinerated inside the combustion chamber.
• Automatic system start-up, operation and shutdown ensure safe and repeatable preheating, requiring minimal operator input and supervision.
• Our system is mobile, user-friendly, lightweight, easy to set up and tear down, and requires very little maintenance.

 
The system essentially consists of two trailers, one which stores the 2 burners (+ 1 spare burner), the gas and compressed air hoses and the thermocouples, and one which contains the control panel and combustion control components (filters, regulators, control valves, orifice plates, flow gauges, etc.). Each burner has a rating of 586 kW and has been sized up to enable you to preheat your pots from ambient temperature to 850 ^oC in 48-60 hours.
 

Hotwork Combustion Technology Ltd Bretton Street, Savile Town, Dewsbury, West Yorkshire WF12 9DB, UK Tel: +44 (0) 1924 506506, Fax: +44 (0) 1924 506311 E-mail: [email protected], Web: www.hotworkct.com

 
The system is controlled by a PLC linked to an operator display screen from where the preheat cycle can be programmed to suit your particular heat-up cycle up to 850^oC. The control system is also programmed to follow automatically a predetermined safe-start cycle and shutdown procedure in accordance with EN746-2 which is a stringent European gas-safety standard applicable to this type of combustion system.
 
As required, the system will be designed for operation with LPG. Please note that we have excluded from our proposal the supply of a vaporiser which ISAL would have to provide, if required.
 
With over 70 thermal bake systems supplied to smelters world-wide, Hotwork CT have gained considerable experience in helping primary aluminium producers preheat their cells successfully. As part of our scope, we would train your engineers and operators during site commissioning on how to set up the system and insulate the cells in order to achieve optimum baking results, leading to smoother cell start-up, lower pull-up voltages, earlier cell stabilization and prolonged cell life.
 
We trust our proposal meets with you approval and please do not hesitate to contact us should you have any queries.
 
Yours faithfully,
 
 
 
 
Denis Hunzinger
Sales & Marketing Director

 

 
 
 
 
SPECIFICATION & BUDGET QUOTATION
 
EA30875 – 21^st JUNE 2012
 
 
FOR 
 
 
 
 
FOR
 
 
1-OFF LPG-FIRED ALUMINIUM REDUCTION CELL
THERMAL BAKE SYSTEM
 

 

Hotwork Combustion Technology Ltd Bretton Street, Savile Town, Dewsbury, West Yorkshire WF12 9DB, UK Tel: +44 (0) 1924 506506, Fax: +44 (0) 1924 506311 E-mail: [email protected], Web: www.hotworkct.com

SHELL DIMENSIONS:                                                     7780 mm x 3500 mm x 1326 mm
                                                                                              The cells having 300 mm minimum clearance between cathode and anodes
 
TYPE OF CELLS:                                                                Alusuisse Prebake
 
CATHODE SURFACE AREA:                                         Approx. 6960 mm x 2850 mm = 19.84 m²
 
BURNER SIZE:                                                                  586 kW per burner when burning stoichiometrically
 
NO. OF BURNERS / SYSTEM:                                      Two (2)
 
FUELS:                                                                                LPG in gaseous form (vaporiser to be supplied by ISAL, if required)
                                                                                              Net Calorific Value: 25 kWh/Nm³ (to be confirmed)
                                                                                              Min. flow of 50 Nm³/h to be available at a pressure of 1.5 - 3 bar.
 
COMPRESSED AIR REQUIREMENT:                         Max. 4.5 Nm³/min at 6 bar, dry and clean, from plant compressed air network.
                                                                                             
ELECTRICAL REQUIREMENT:                                      380V, three phase, 50 Hz
                                                                                              220V for control equipment
                                                                                             
 

 
2. SCOPE OF SUPPLY
 
Our proposal includes for the following:
 

• Design, manufacture, shop assembly, painting, shop testing and packing of an LPG-fired two-burner Cell Preheating System complete with control cart (incl. Siemens PLC and HMI, filter, regulators, valves, pressure switches, gas and compressed air trains) and utility cart (incl. burners, inspirators, hoses, thermocouples).
• Supply FCA Dewsbury UK Incoterms 2010
• Commissioning of the above system on site in Straumsvik.
• Training on how to operate and maintain the system.
• Documentation including detailed schematic and electrical diagrams, parts lists, operating and maintenance manuals in English.

 
 
3. GENERAL DESCRIPTION
 
The portable burners will be used for baking aluminium reduction cells thoroughly and uniformly, and driving off coal tar pitch volatiles prior to placing the cells in service. Each baking system contains two portable burners, which are inserted into the pot cell cavity between the cathode lining and the anodes. The burners can be installed either at the centre of the duct end and tap end or at two diagonally opposed corners of the cell depending on cell construction and space availability. The system is designed to achieve a total rated heat input of 1172 kW.
 
The baking process is expected to range from 48 to 60 hours and heat the cathode lining to a finish temperature up to 850^oC, and the burners have been rated accordingly. The cell area can be operated to a maximum of 900 °C with the over-temperature controller set 100^oC higher.
 
The design of the system and the equipment included in it will be in accordance with good engineering practices, bearing in mind that it has to perform in the arduous conditions of the Aluminium Reduction Industry and must be capable of Heavy Duty Operation. Maximum reliability of operation, combustion and electrical safety, low maintenance, ease of access, rapid set-up and tear-down, have all been taken into account. The system will be designed to comply with EN746-2 Standard, Industrial Thermoprocessing Equipment, Part 2 Safety Requirements for Combustion and Fuel Handling Systems. We are aware that no equipment can be earthed within the pot lines.
 
The system requires dry clean compressed air available at a continuous supply pressure of 6 bar and at a maximum flow of 4.5 Nm³/min. This should be available from the plant’s compressed air network. The minimum clearance between the top of the cathode and the bottom of the anode must be at least 300 mm.
 
Specially designed hoses are provided on this system. The fuel hoses are manufactured by Goodyear and are rated for flame resistance and have a pressure rating of 20 bar. The incoming gas supply would be at 1.5 bar min - 3 bar max and control at approx. 0.1 bar.

We would take our power supply from 380 V sockets located inside the potroom and feed it to our control panel through an isolation transformer for the control equipment.
 
A PLC-based control system will be provided for the purpose of initiating and monitoring the safe start-up and operation of the Cell Preheating System. The system is supplied with a Siemens S7-300 PLC and a MP270 operator interface (HMI). The control panel and the valve trains would be enclosed in a box fitted with heaters to maintain the temperature inside the enclosure positive. Temperature programming through the PLC will provide the possibility of storing several heat-up cycles depending on the types and sizes of cells which need to be preheated.
 
The fuel burner safety controls are hard wired through micro relays independent of the PLC. The PLC program contains the purge timer, and an external watchdog timer monitors CPU scan time. A loss of PLC power interlock is also included on the system. Compressed air including atmosphere air via the inspirator is used for generating combustion air and for purging. Prior to the trial for ignition, all fuel combustion safety control interlocks must be satisfied incl. gas high-low pressure, air high-low pressure, excess temperature, etc. The PLC monitors all outputs whilst the HMI will enunciate the last fault as well as display prompt messages to the operator.
 
Trial for ignition is limited to 5 seconds. Three relights are permitted but failure for any burner to light after four attempts will cause the unit to re-purge. Providing one burner lights, relight attempts of the second burner is unlimited. Once a burner is lit, its flame is continuously monitored by a UV flame scanner.
 
The arrangement of the fuel piping and fuel combustion safety controls is in accordance with EN746-2. All fuel combustion safety controls, where applicable, are CE approved.
 
The pot superstructure should be protected from radiation by positioning heat shields and fibre insulation between the side walls and the anodes. The supply of these heat shields and fibre insulation materials is excluded.
 
The products of combustion must be discharged from the cell to atmosphere via the cell fume extraction system, and must not be allowed into the potroom as they will contain carbon monoxide. ISAL will need to work out a method of modulating the suction of the cell fume extraction system to cope with the changing volumes of products of combustion as the temperature inside the cell rises.
 
Oxidation of the cathode and anodes will be minimised during baking by sealing the pot and by over-pressurising the combustion chamber slightly, preventing ingress of cold air. This is also achieved by running the combustion system slightly ‘fuel rich’, reducing the presence of oxygen inside the cell. Two-off re-usable stainless steel cathode protection plates are also supplied and are to be installed under the burners so as to avoid flame impingement on the cathode, dimensions 1200mm x 800mm x 4mm each plate.
 
The combustion control trailer will be mounted on foam-filled pneumatic tyres and will stay in the potroom for the duration of a bake. It contains the control panel with PLC, HMI and flame programmers, and all necessary filters, regulators, valves, pressure switches for safe and automatic operation of the Cell Preheating System. The control panel also includes six point temperature recording through the PLC and HMI to give a permanent record of the cell preheat cycle. The six control thermocouples will be installed so as to touch the surface of the cathode.
 

 
The utility trailer is also mounted on foam filled pneumatic tyres and contains the portable burners, air and gas hoses, and thermocouples. Once the system has been set up for operation, this trailer can be moved ‘out of the way’. As with the control unit, the entire construction (excluding the wheels and axles) will be made of fibre glass with timber floor.
 
Square port valves are used for controlling fuel and compressed air. For the fuel, double blocking safety shut-off valves are used. The flexible hoses for the supply of fuel and compressed air will give complete electrical insulation at a voltage of 1000 DC. The fuel hoses will be fitted with double self-sealing quick-release couplings. The couplings for both the air and the gas will be Hansen. Please note that gas hoses, compressed air hoses, and cables should be protected by portable bridges if they cross access routes.
 
Sound levels for all the equipment supplied shall meet the requirement of less than 85 dBA at 1 m when the equipment is functioning in the pot under normal operating conditions.
 
Approximate overall dimensions of the system are as follows:
 
         Control Cart:  2445 mm long x 1050 mm wide x 2100 mm high
         Utility Cart:     3200 mm long x 1700 mm wide x 2100 mm high
 
 
4. PERFORMANCE REQUIREMENTS
 
The preheating system has been designed to heat the cathode lining of the cell from ambient to 850°C in a total time of 48-60 hours. The instrumentation supplied will allow a temperature soak to occur at any single temperature. The maximum temperature difference between any two points on the surface of the cathode lining will not exceed 100^oC other than the area directly beneath each of the burners. For the purpose of performance requirements, we have assumed the area under the burners to represent 10% of the cathode area. The system will operate in a slightly reducing atmosphere and the combustion chamber will be slightly over-pressurised so as to minimize the amount of oxygen available inside the cell and thus prevent, as far as possible, cathode and anode oxidation.
 
 
5. BURNERS
 
Each burner will have a capacity of 586 kW when burning under stoichiometric combustion, and will have a turndown sufficient to control the atmospheric temperature inside the cell from about 150^oC. Ignition of the burners will be automatic and the burners will have full flame stability with flame failure protection. Protection against fuel, compressed air and electrical supply failure is included in our proposal. The burners will be designed so as to be unaffected by the reducing furnace atmosphere. Each burner will be fitted with a support bracket which will enable the burner position in the cell to be adjusted. Diverter flares will also be installed on the burner inspirators so as to minimise the amount of pitch fumes drawn into the inspirators.
 
 

6. THERMOCOUPLES
 
All thermocouples will be Type K and will be installed so as to touch the surface of the cathode. Six thermocouple points are used for temperature control with two at each end of the cell, away from the burner, one in the centre, two along the central axis of the cell and another one at a location to be chosen. An additional thermocouple located at the centre of the cell is used for over-temperature. The average of the six control thermocouples is used for controlling the temperature inside the combustion chamber.
 
 
7. CONTROL CABINET
 
A PLC-based control system will be provided for the purpose of initiating and monitoring the safe start-up and operation of the Cell Preheating System. The system is supplied with a Siemens S7-300 PLC and a Siemens MP270 (Human Machine Interface). Operator screens and Siemens system screens will be in English.
 
Temperature recording will be provided through the PLC and download at regular intervals the temperature records to a memory stick via the HMI unit USB port. The temperature would also be controlled via the PLC by taking an average of the six control thermocouples. This will provide the possibility of storing several heat-up cycles depending on the types and sizes of cells which need to be preheated. Also included are an over-temperature controller and all the necessary lights, safety limits and alarms.
 
The control panel will also incorporate heaters, 220V duplex sockets and a light which will come on automatically when the panel door is opened. The actual control panel will be a fibre glass enclosure, which will be mounted on a non-conductive structure. The power cable from the control cart to your power supply will be a three phase, 30m long cable.
 
 

8. EQUIPMENT TO BE SUPPLIED FOR AN LPG-FIRED SYSTEM
 
ITEM        QTY     DESCRIPTION
 
1                   3              Gas fired aluminium cell preheat burner complete with compressed air inspirator, low air pressure switch, gas safety shut-off valve, gas shutoff cock, spark igniter, spark transformer and UV flame detector
2                   2              Compressed air automatic shutoff valve
3                   1              Compressed air regulator
4                   2              Air pressure switch, one for high pressure, one for low pressure
5                   3              Gauge cock and gauge
6                   2              Air orifice plate with differential pressure gauge for air flow indication and integral pressure switch for purge proving
7                   2              Air square port valve
8                   2              Air trim valve
9                   1              Inlet air flexible pipe – 13.5 m long
10                3              Air manual shutoff valve
11                2              Burner air flexible - 1 x 10.5 m long, 1 x 16.5 m long
12                2              Control motor for air and gas control valves, one per burner
13                4              Gas orifice plate with differential pressure gauge for gas flow indication
14                1              Gas pressure regulator
15                5              Gas manual shutoff valve
16                2              Gas pressure switch, one for low pressure, one for high pressure
17                2              Gas inlet flexible pipe hose complete with double quick release self-seal couplings and a male coupling to be fitted on your gas supply – 13.5 m long
18                2              Gas control square port valve
19                2              Double block gas safety shutoff valves with integral limiting orifice valves
20                2              Burner gas flexible pipe complete with double self-seal couplings – 1 x 10.5 m long, 1 x 16.5 m long
21                4              Pressure gauge with cock
22                1              Stepdown transformer 380 V to 220 V
23                7              Single thermocouples in metal sheaths with insulated thermocouple pigtails
24                1              10.5 m thermocouple loom
25                2              Spark transformer lead inside flexible hose - 1 x 10.5 m long, 1 x 16.5 m long
26                2              U.V. detector lead inside flexible hose - 1 x 10.5 m long, 1 x 16.5 m long
27                1              Control cabinet including a Siemens PLC, a Siemens HMI, heaters, temperature recording function, temperature programming function, an over-temperature controller, thermocouple connectors mounted on outside of panel, or equivalent instruments, together with two flame programmers for fully automatic start-up and flame supervision
28                1              Tool box for the commissioning of the system
29                3              Operating and Maintenance Manuals in English
 
 

9. Commissioning and Operator Training
 
We have included for the provision of three engineers for a period of ten (10) consecutive days (10 hour days) on site at ISAL in Straumsvik, one to show how to seal the pots, two to commission the combustion equipment and control system and undertake operator training for the control and combustion equipment.
 
By careful planning, this ten day period should be sufficient for two 60-hour bakes to be carried out. For the first bake, we would train ISAL’s personnel to set up the system and seal the pot and for the second bake, ISAL’s personnel would carry out these tasks under our supervision. We would also train operators on how to maintain the equipment.
 
Please note that our proposal includes all travel time, hotel accommodation, meal allowances, travel costs and out of pocket expenses. Any additional time that may be required for reasons beyond Hotwork CT’s control would be charged at £600.00 per day per engineer plus all additional expenses at cost.
 
Local transport of Hotwork CT personnel between the airport, hotel and the place of work is to be arranged by ISAL.
 
Much of the training will be 'hands on' starting with the setting up of the thermal bake system i.e. burner positioning, thermocouple positioning, connection to gas, compressed air and electrical supplies. The system will be described in detail with identification of the various components (P+I diagram) and how they operate, and the control system will be presented (system start, system shutdown, navigation between screens, temperature control, temperature recording, emergency stop, etc.). Fault finding and maintenance will also be covered.
 
This is what we propose to cover in terms of training for the various teams:
 
Pot relining teams:
They will be responsible for carrying out the bakes and therefore need to know how to seal the pots, set up the thermal bake system, operate the system, find and clear faults, maintain the system and carry out checks during the bakes.
 
Maintenance teams:
They need to know how to set up the thermal bake system, operate the system, find and clear faults, and maintain the system.
 
Potroom shift teams:
They need to know how to carry out the checks during the bakes, and find and clear basic faults.
 
Provisional programme (allowing for 3 days per bake):
 
Days 1 & 2
Establish site. Testing of the system by our commissioning engineer and electrical engineer. Sealing of Cell 1 by our pot sealing specialist, all pot relining teams should be present. Setting-up of the system on Cell 1, all pot relining teams and maintenance teams should be present.
 
Day 3
Start of the first bake. The pot relining teams need to know how to carry out checks during the bake.
Training of shifts as required.
 

Day 4
Training of all pot relining teams and maintenance teams.
Training of shifts as required.
 
Day 5
Sealing of Cell 2. All pot relining teams need to be present as they will seal the pot under Hotwork supervision.
 
Day 6
Training of shifts as required.
End of the first bake. All pot relining teams need to be present.
 
Day 7
Pot relining teams to set up the system on Cell 2 under Hotwork supervision.
Start of the second bake. All pot relining teams need to be present.
Training to suit ISAL’s requirements.
 
Days 8 & 9
Training to suit ISAL’s requirements
 
Day 10
End of the second bake. All 3 pot relining teams need to be present. Final discussions.
 
As regards equipment required:
 
Testing:
On Day 1, our commissioning engineer and electrical engineer will need to have an area available outside the magnetic field with gas, compressed air and electrical supplies where they can fire the burners in the open air. They will bring their own tools and testing equipment.
 
Pot Sealing Materials:
ISAL to supply suitable pot sealing materials and personnel.
 
Baking:
Gas, dry and clean compressed air and electrical supplies.
 
Training:
A meeting room, white boards, paper flip charts, pens. If a data projector is available, we could use it. As explained, most of the training will be 'hands on' but we would use the O&M Manual with P+I diagrams for the more theoretical training.
 
 

10. EXCLUSIONS
 
The following items are excluded from our proposal:
 
·         Delivery to Straumsvik
·         Any spares (other than 1-off complete spare burner)
·         Insulation materials to seal the pots
·         Compressor/drier assembly
·         LPG vaporiser
·         Fume extraction systems
·         Portable bridges/ramps to protect hoses from traffic
·         Shift working
·         PLC & HMI software licences
·         Connections to gas and compressed air more than 13.5 m away from the preheating system.
·         Connection of the system to electrical power supply.
·         Any thermocouples other than the six control thermocouples and the over-temperature thermocouple
·         Internal travel arrangements
·         Any acceptance, approval or permit by third party
·         Any interpreting/translating
·         Taxes or duties
·         Any major items or services other than specified.
 

COMMERCIAL
 
 
1. PRICES
 
For the design, manufacture, shop testing, packing, supply and site commissioning of 1-off LPG-fired aluminium reduction cell preheating system using Siemens PLC and HMI, generally as described herein, our budget price is:
 
£????? FCA Dewsbury UK Incoterms 2010
(?????Pounds Sterling)
 
The above price includes the services of three engineers for a period of ten (10) consecutive days on site (10 hour days) to commission the control and combustion equipment. Also included are hotel accommodation, meal allowances, travel time, travel costs and out of pocket expenses. Any additional time would be charged at £600.00 per day per engineer plus all additional expenses at cost.
 
2. DELIVERY
 
Fourteen to sixteen (14-16) weeks FCA Dewsbury UK from receipt of downpayment.
 
Please note that the cost of shop testing in Dewsbury has been included in our price. We will give you a 7 day notice of the test date should you wish to witness test the operation of the equipment prior to shipping.
 
3. TERMS OF PAYMENT
 
To be agreed but we suggest:
 

• 30% downpayment with order.
• 40% progress payment.
• 30% on readiness to deliver.

 
4. VALIDITY
 
This is a budget proposal and, as such, is not open for acceptance.
 
5. TAXES AND DUTIES
 
The above prices are exclusive of all taxes and duties.
 
6. DEFECTS LIABILITY PERIOD
 
Our proposal includes for a 12-month defects liability period from commissioning or 15-months from delivery, whichever is the shortest.  However, our liability will be limited to defects due only to fair wear and tear of items of our supply and to HCT workmanship and design. The equipment should also be correctly maintained during the warranty period.

Our liability shall not extend to the failure of the following items which, by their nature, should be considered as consumables:
 
·         Ultra violet cells
·         Instrument fuses
·         Solenoids
·         Pressure governor, springs and diaphragms.
 
7. CONFIDENTIALITY
 
The contents of this quotation are strictly confidential and should not be discussed with or communicated to a third party.
 
8. CUSTOMER CARE
 
In order to improve continuously the service that we offer our customers, HCT Limited operate a customer care policy. Through a centralised point within the company, your concerns and queries regarding the service you receive will be dealt with objectively and independently. Please contact the office of Mr David Robinson, Managing Director, if a situation arises that you feel requires attention.
 
9. TERMS AND CONDITIONS
 
Hotwork CT standard terms and conditions of business apply.
 
 
For Hotwork Combustion Technology Ltd

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