Tenova Pyromet slag flow control valve outperforms design criteria

The slag valve was installed and commissioned in 2011/2012 on a 12 MW furnace as part of a new mineral wool plant built in the USA. Although the design intent was for occasional use during emergency shut conditions only, during the first six months of operation, the valve became the preferred method, over the mudgun, for closing the furnace. Only a few minor changes were required for the valve to cope with the increased heat load and much higher frequency of use. Continuous operation requires robust equipment design as it subjects all equipment in the taphole area, including the slag valve, to very high heat loads and does not allow for frequent maintenance.

In addition, space constraints in the taphole area of this relatively small furnace meant a compact design that is easy to maintain were a requirement upfront.

The slag valve position is actuated remotely by a set of push button controls, with control of the slag valve being a simple operator controlled task. A combination of live video feedback and basic feedback from the spinner, are used by the furnace operators to decide on what changes must be made to the position of the slag valve. If an emergency shut is required, the furnace operator lowers the slag valve completely. The slag valve can be setup to close automatically in the event of a furnace trip, should the specific operation warrant this action.

The Tenova Pyromet slag valve can be used in conjunction with standard tapping equipment such as drills, clay guns and lances. It may also be used to replace the mudgun, offering substantial savings in terms of equipment costs, noting that a valve assembly typically costs around 15 % of a mudgun machine. In addition, the space required for a slag valve is substantially less than a mudgun, and operating space is not required, since it is permanently attached to the shell. It is also simple to maintain, with a steel flange installed in order to facilitate taphole repair and replacement from the outside of the furnace.

Offering remote closing under normal conditions and emergency conditions, the valve makes use of a water cooled copper element that is hydraulically operated and attached directly to the slag taphole.

As a reliable and robust method for closing the furnace, application of the slag valve assembly is broad and it can be retrofitted to most existing slag tapholes, with minimal modifications.  It can easily be installed as an emergency back-up to most slag tap holes, as well as to add a level of control upstream of the slag granulation processes and to improve their consistency and safety.

During the development phase, finite element method (FEM) and computational fluid dynamics (CFD) software was extensively used to model predicted operating conditions and to optimise the design. By using CFD, it was possible to understand temperature distribution inside the copper and to optimise these to improve overall performance.

“Development of the improved slag flow control device is part of our commitment to ongoing R&D and technology development to enhance our range of furnace products, and so meet the evolving needs of our client base who are faced with an increasingly urgent need to improve efficiencies, recover more energy and reduce operating costs,”  says Andre Esterhuizen, Tenova Pyromet General Manager Sales and Marketing.

Tenova Pyromet presented a paper on the slag flow control valve at the recent South African Institute of Mining & Metallurgy Furnace Tapping Conference 2014, held in Johannesburg, South Africa. 

Tenova Pyromet is a leading company in design and supply of high capacity AC and DC furnaces and complete smelting plants for production of ferroalloys, base metals, slag cleaning and refining. Tenova Pyromet also designs and supplies equipment for material handling and pre-treatment, alloy conversion and refining, granulation of metal, matte and slag, furnace off-gas fume collection and treatment, and treatment of hazardous dusts and waste. Tenova Pyromet has several technologies to reduce operating costs and increase production power consumption.

Tenova Mining & Minerals is a total integrated solutions provider to the global mining, bulk materials handling and minerals beneficiation and processing sectors, offering innovative technological solutions and full process and commodity knowledge across the mining industry value chain.

Tenova is a worldwide supplier of advanced technologies, products, and engineering services for the metals and mining & minerals industries. More information is available at www.tenova.com.