Specialised Topic: CISDI-AutoARC - creating greener and smarter mini-mimelting

CISDI has invented a green, energy-efficient and clean production technology system with the electric arc furnace.

The intelligence in the patented green EAF – CISDI-AutoARC^TM boosts energy conservation, consumption reduction, efficient production and facilitates the use of green, intelligent and reliable equipment.

A new-generation melting vessel for the mini-mill process, the green EAF charges scraps creatively in cascades and in a horizontal, continuous process and preheats scraps during the charging process.

It outpaces conventional EAFs, reducing the tap-to-tap cycle time to 35min/heat and power to 330kwh/t and electrode consumption to 1.0kg/t while boosting production efficiency and metal yield.

It is considered a major breakthrough for the sector and has already achieved a number of world-class performance indicators for its ultra-high-power smart power supply, efficient, deep clean melting, eco-friendly transport system and its preheating of the scrap and its integrated controls.

In 2019 a CISDI-led scientific study on The Development and Application of Green, Efficient EAF Melting Tech was awarded the silver medal for China’s S&T advancements.

This expertise has been granted patents in China, the EU and Japan.

 

✧         Creative, continuous scrap charging with cascade auto batching

Years of research and engineering experience in scrap charging and shaft furnace structure provided the tech roadmap for CISDI’s route to the future of green, intelligent electric furnace melting.

The sector needs to prioritise the phasing in of advanced technical indicators, refiguring furnace energy structure and making equipment more reliable. CISDI-AutoARC^TM with cascade automatic batching is now providing solutions.

Cascade auto batching during the closed, continuous charging process enables a faster charging speed and better scrap preheating.

Its stepped structure takes up less floor space in the furnace workshop and relieves the original busy batching operations.

A visual identity system is applied to cascade batching, which makes the process stabler and more accurate, and therefore can be performed unmanned.

Remarkable improvements have been seen at MCC-SFRE, where an EAF has been transformed into CISDI’s green EAF. It features closed, cascade and continuous charging and flat bath melting.     

This cast-steel EAF with a capacity of 70 tonnes is now producing with greater efficiency. Energy consumption and production costs have been slashed and the melting shop is now a clean, safe environment.

 

   

The rebuilt 70-tonne green EAF at MCC-SFRE

 

Latest news:

An association standard – The Electric Arc Furnace with Cascade, Continuous Charging – was approved for release in June by The Chinese Society for Metals. CISDI is the chief editor.

China’s top mini-mill melting demo project is to begin. CISDI and Du Gang Steel signed the contract for a CISDI-AutoARC^TM in July.

 

✧         Recycling excess heat for preheating scrap

Recycling excess heat from the fume - by as much as 120-140kwh/t - to preheat the scrap is one of the main methods of reducing furnace power consumption.

In addition, CISDI-AutoARC^TM’s innovative tech saves even more energy by providing a transportation process which is not only more stable than conventional methods, but also ensures thorough and evenly-distributed pre-heating of scrap occurs.

The cascade steps on the continuous charging channel have a large height difference, which enables the rolling scrap to turn over the steps. This solves the difficult preheating problem which arises in conventional processes where the bottom layer of scrap remains immobile.

CISDI-AutoARC^TM can be tailored to suit different requirements.

One option is to intensify the preheating effect by adding external chemical energy at the relatively cold area of the scrap transport belt conveyor. This further reduces melting power consumption and electrode consumption.

This option is designed with two dust-catching points. The first preheating section ranges from the furnace to the first dust-catching point. The scrap will mainly be preheated by the fume and the combustion of carbon monoxide in the fume.

The second preheating section resumes between both dust catching points. The height of this sectional stationary channel is reduced and high-velocity burners are installed to burn with natural gas or mixed gas. They can further enhance the fume temperature and flow rate inside the channel, achieving a stronger preheating effect. 

The chemical energy can also be fully utilised by a number of control and intelligent means – fume split control, fume measurement and smart control and dynamic sealing at scrap’s inlet.

 

A sketch of the CISDI-AutoARC^TM electric arc furnace with scrap preheating and cascade-wise, continuous charging tech

 

✧         Automatic, intelligent melting

CISDI-AutoARC^TM total solutions provide diversified methods of control for enhancing melting automation and intelligence levels.

Multiple sub-system controls for the electric arc furnace are integrated and optimised into the master control system. Field instruments enable interconnection via the gateway controller/protocol. All process information and data is collected, transmitted and controlled.

Mainstream industrial networks are allowed to switch in to the furnace’s master control system. Digital network tech closely co-ordinates all procedures - from furnace melting, scrap preheating and dioxin control to the dust-catching system.  

Various status points during melting can be real-time monitored: the judgment of scrap melt-down, foamed slag control, temperature measurement and sampling control, non-contact continuous temperature measurement and fume continuous analysis.

All the information is interconnected and shared in the control system.

 

✧         One-touch operation

Continual advancements are bringing a one-touch melting operation ever-closer.

The upgrading of equipment and online measuring is progressing. Scrap automatic continuous charging equipment has now been developed. The sector now relies on the robot for online temperature measurement and sampling. CISDI innovation has created furnace door automatic cleaning unit and the automatic tapping device.

Multiple intelligent models have been developed for scrap batching, electrode regulation, heating and critical parameters and image feature extractions.

An integrated management system has also been set for controls of the melting data, process quality and cost and peripheral conditions.

CISDI-AutoARC^TM is now refining mini-mill melting production to meet digital, intelligent, green and lean targets.