cpmPlus Energy Manager for by-product gas optimization

Improving the energy efficiency in iron and steel making

Energy constitutes about 20% of the

total production cost in an integrated

steel mill, and therefore energy

efciency is crucial for protability.

Energy is distributed over the mill

through complex networks of electricity,

steam, byproduct gasses, and imported

fuels. Understanding this system and

controlling it in optimal way is the key

to unlocking many of the opportunities

to improve energy efciency and

competitiveness while reducing

environmental impact.

A challenge of balance

Iron and steel making requires complex gas networks which

can reliably supply a wide variety of grades and blends to a

large number of process consumers. Due to the critical nature

of production scheduling, these gases must always be avail-

able when needed. This necessitates the use of gas storage

holders to compensate for temporary shortages or surpluses.

When gas demand exceeds supply, supplementary fuel must

be bought at volatile - and often higher - market prices. When

supply exceeds demand, excess holder gasses must be flared.

This wastes energy and increases the plant’s carbon footprint.

In addition to process needs, many mills have power plants

whose boilers are fired with a combination of fuels, including

by-products gasses from blast, coke and basic oxygen furnac-

es. This energy is balanced with electricity purchased from the

grid to meet the total plant demand. And if the steel maker is

able to predict this electrical power demand accurately, it can

be purchased at a lower price.

The challenge therefore is to optimize the entire energy system

throughout the plant to supply the needs of all consumers with

minimum costs. This results in reduced flaring, reduced pur-

chase of electricity and supplementary fuels, and reduced

price of purchased electricity.

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Systematic solution

Since the different forms of energy generated and consumed

at a steel mill are tightly interdependent, it makes sense to

optimize them together. This can have the greatest benefit to a

steel maker’s competitiveness in terms of energy costs and

carbon emissions, as well as minimizing the penalties for

under- or over-estimating the demand.

ABB’s cpmPlus Energy Manager (cpmPlus EM) is a software

solution that models and visualizes the entire plant’s energy

flows. cpmPlus EM calculates optimum by-product gas distri-

bution schedules to process consumers and power plant

boilers. This optimization ensures 100% by-product gas avail-

ability while minimizing wasteful flaring.

cpmPlus EMS accommodates plant processes such as gas

network and mixing station configuration as well as financial

considerations, including boiler start-up costs. It can help

maintain optimal energy efficiency despite unplanned produc-

tion changes or energy price volatility. And, the system can

even help optimize export of electricity or byproduct gases

when feasible and economical.

Efficient modelling tools

ABB’s Economic Flow Network (EFN) provides tools to graphi-

cally configure the entire energy system model as an intercon-

nected flow network, where each flow is represented with an

allowed range of values and a unit price. The tool allows the

specification of logical constraints upon the various process

conditions. Based on the configured model the optimization

problems are automatically created and solved by a Mixed

Integer Linear Programming (MILP) solver.

Dashboard for energy efficiency

cpmPlus EM provides dashboards for energy performance,

from the production process level to the entire plant. This

allows the monitoring and targeting of energy performance

indicators, as well as analysis and reporting to verify the perfor-

mance improvements resulting from implemented activities

and projects.

Dedicated dashboards for each production station allow opera-

tors to act on deviations from optimum that are often hidden

behind various energy and material flows. Operators will be

able to validate the forecasted schedules of gas, electricity and

steam demand, as well as by-product gas generation com-

pared to the day’s production schedule.

At the same time, site power plant operators can use the

optimization to select the best combination of own power

generation and external supply. This allows energy efficiency to

be managed as a key performance indicator, alongside pro-

duction quality and throughput.

The power plant and process schedules calculated by cpmP-

lus EM can also be implemented automatically by sending

scheduled set points to advanced process control, which then

coordinates the power plant control systems to run processes

in an optimal way.

Financial benefits

ABB conducted a pilot study with cpmPlus EM for an integrat-

ed steel mill to help create an optimized gas supply schedule

that would meet the demands of various processes, and auto-

mate manual control systems. This resulted in a potential 50

percent reduction in wasteful flaring, which could save the mill

between $2-5 million a year in energy costs.

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