Metso Insights Blog Mining and metals blog Industrie 4.0 in Sulfuric Acid Production
Metals refining
Feb 7, 2019

Industrie 4.0 – complementing or leading the way in sulfuric acid production

Metso Outotec has been in the forefront of process and product development as well as project execution in the sulfuric acid industry for nearly a century and it is perhaps an opportune moment for us to look towards our second century and what this may bring for the industry as a whole.
Sulfuric acid plant

Digitization, less commonly digitalization, is the process of converting information into a digital (i.e. computer-readable) format. Digitizing simply means the conversion of analog source material into a numerical format; the decimal or any other number system that can be used instead.

Industry 4.0 is a name for the current trend of automation and data exchange in manufacturing technologies. It includes cyber-physical systems, the Internet of things, cloud computing and cognitive computing. Industry 4.0 creates what has been called a "smart factory". Within the modular structured smart factories, cyber-physical systems monitor physical processes, create a virtual copy of the physical world and make decentralized decisions. Over the Internet of Things, cyber-physical systems communicate and cooperate with each other and with humans in real time, and via the Internet of Services, both internal and cross-organizational services are offered and used by participants of the value chain.

The term "Industrie 4.0" originates from a project in the high-tech strategy of the German government, which promotes the computerization of manufacturing. The term "Industrie 4.0" was revived in 2011 at the Hannover Fair. In October 2012 the Working Group on Industry 4.0 presented a set of Industry 4.0 implementation recommendations to the German federal government. The Industry 4.0 workgroup members are recognized as the founding fathers and driving force behind Industry 4.0.

The object of this paper is to consider the implications of Industry 4.0 on the future design/operation and maintenance of an autonomous acid plant.

Industry 4.0
Source: Faster, Better, Cheaper" in the History of Manufacturing: From the Stone Age to Lean Manufacturing and Beyond by Christoph Roser

What has shaped the acid industry in the last decades?

Significant advancements have been made in the last decades in the design and operation of acid plants and these achievements have mirrored the needs of the industry, namely:

  • Process design and development
    Many of these developments are taken for granted today, however double catalysis, internal heat exchangers, heat recovery (to name just a few of the big ticket items), have been complemented by a myriad of process design optimization that ensures that every ounce of efficiency is extracted from a modern facility.
  • Ever larger production facilities
    Twenty years ago most process engineers would dropped their slide rules if you had indicated that a 5,000 tpd acid plant would be available in one process stream. Today, Metso Outotec has not only successfully designed and built such plants (which has been successfully operated for over five years), but has developed plans for even larger capacities.
  • Materials of Construction
    Acid resistant stainless steels, such as Outotec’s SX® product and the industries’ equivalent competitive offerings, are now a cornerstone of the industry. The application of materials designed for industries with deeper pockets ultimately cascade down to the acid industry in time and lead to design optimization based on these material properties. Outotec’s heat recovery system (HEROS) and quench tower (OutoVent) designs make use of these advanced properties.
  • Design tools and construction techniques
    Clearly the availability of reasonably priced, advanced computing power and the associated software programs has revolutionized all global industries. Today the engineer has a toolkit of integrated software allowing ‘instantaneous’ 3-D design configurations to be visualized and reviewed for all mechanical properties in real time on the computer screen. This computing power has also allowed for significant advancements in constructability and modular design, based on the ability to visualize and prove draft concepts. 
  • Demographic changes in the industry
    Many of the recent developments in the acid plant industry have been as a response to customer needs to complement to scarcity of skilled resources entering (and retained in) the industry with advanced process control. New offerings have been developed (such as Outotec’s intelligent acid cooler, incorporating PORS). It should however be noted that complex process control and analytics is also a dichotomy – a requirement for skilled maintenance resources…. 

Future acid plant challenges

Future acid plant challenges can be quantified under the following broad issues:

  • Feedstock/product quality aspects
    In the mining industry, metal content in the ore body has been decreasing since the 1900s and although there are still first rate undeveloped ore bodies in remote, politically unstable regions of the World, the majority of the industry has to deal with lower metal levels, which in many instances have been replaced by increased levels of impurities. In Chile for instance there are significant untapped resources high in arsenic, for which Metso Outotec has developed a novel partial roasting solution.
Industry 4.0 environmental regulations
Source: “Peak Silver and Mining by a Falling EROI”, Commodities / Gold & Silver, Steve St Angelo, Nov 04, 2009,

In the case of the fertilizer value chain, the challenge of phosphate rock impurities (cadmium and other minor elements, including radioactive elements) entering the agricultural/consumer food chain has the attention of national regulators and ultimately action will be taken.

  • Environmental regulations
    Not surprisingly what enters the plant as feedstock exits the plant in the product or as a bi-product or effluent of some kind. At the same time there is a significant pressure on operators to curb all types of plant emissions In the case of Chile for example the current future emissions are clear to see:
  • Operational realities
    Safety has rightly become an overarching operational factor and together with the greater production demands and ever tighter plant operating windows, acid plant operations now have conflicting KPIs to fulfil.

    Good operation and maintenance practice is fundamental to any business, however there is today a lack of skilled resources and, as we all know, plant equipment failure can and will happen (Murphy’s Law).

    As process plant increases in complexity to support customer needs for inherently safe systems, plant trending and analytics, there is a need for better a process plant overview. Clearly no system can make up for good operating and maintenance practices, however there is a need for:
    • “simple” methods of interpreting operating process data and trends
    • Methods of drawing attention to the consequences of potential equipment failure is critical to production/operating decisions.

  • Operational costs
    There is a trend towards more demanding product acid specifications driven by legislation that will affect the producer of acid for his downstream fertilizer value chain or the smelter wishing to sell his bi-product on the open market.
  • The implications for out of specification acid are a well-documented matter, however the ability of the acid plant of the future to react to variations in feedstock will be paramount.

Can the concepts of Industry 4.0 assist the acid industry of the future?

We are all well aware of the fundamental inroads that technology/Artificial Intelligence is making in our world with driverless mining cars, mining trucks and tractors. This trend is set to continue and will impact the acid industry in one form or another.

A recent quote from Rick Howes, CEO of Dundee Precious Metals and president of Terrative Digital Solutions, an outspoken captain of the mining industry, recently summed up the matter 

Digit[al]isation without vision is little more than blind ambition

There is a significant amount of truth in this statement and it is perhaps reasonable to dwell on how development is likely to take place from Metso Outotec’s point of view.

  • Plant configuration will require significant re-design to allow the concept to be realized
    • Cost per ton of installed production may not be cheaper
    • However ton of produced acid may be reduced via increased availability?
  • Significant increase in process control complexity will be required
    • relative price of intelligent sensors and complex process control has drastically reduced in the last decade
    • Outotec’s PORS managed heat exchanger requires significantly more I/O and associated instrumentation to fulfil its function – mitigation of hydrogen explosions
    • Further focus/pressure for advanced maintenance skills for the industry will be required as plant complexity increases
  • Plant automatization will take place in a step-wise approach
    • Focus on module based solutions for plant areas
    • key advisory (rather than operational) actions being carried out automatically
  • Focus on (and adaptation of) equipment monitoring will be required to meet the needs for predictive maintenance specific to the acid industry

Initiatives within Metso Outotec

No supplier in the industry is starting from scratch and Metso Outotec is no different. We have, together with a number of customers, have made significant inroads into developing a safety orientated advisory packages based around our PORS (Plant Operability Reliability Safety) system. This aid to the operator runs parallel to the DCS and compares plant theoretical versus actual plant KPIs (key performance indicators) and the algorithm identifies potential cause(s) of the operational upset and interpretation /follow-up of the operational trend/KPI. This information is transmitted to operator in the form of a simple screen drawing his attention to the operational trend/upset condition and warns him of the ongoing implications to the overall process if the trend continues.

Plant Operability Reliability Safety

Other business lines within the Metso Outotec organization have also made significant inroads into remote control, guidance and trending of metallurgical plants.

In roasting, Metso Outotec has a growing reference list of customers that have installed our Outotec Pretium Roaster Optimizer which trends key KPIs including energy efficiency, feed rate and metal recovery as production status in real time. Various outputs from the parallel system advise operators of changes to operational control of the plant, whilst management is informed of plant availability, ‘hot spots’ and fault detection, as well as operational team performance.

In smelting similar advisory tools are being used to for multiple aspects of the smelting process, including feed control, cooling water system monitoring and control, optimization of the concentrate burner to complete smelter information management systems.
It must be pointed out that all the systems described above ‘merely’ advisory systems at this stage, with the operator making final adjustment/action based on his final judgement. As operator trust is built in the ability of these modules to operate and interact with one one another, increasingly autonomous process plants will prevail.



Historically, concepts in the petro-chemical industry have cascaded down to the acid industry over time and this trend will continue in the future. At the same time Intelligent sensors and real time dynamic modelling have filtered down into the ‘real’ world at sensible prices, which are now showing benefit to the industry at large.

Metso Outotec is proactively developing modular analytical/autonomous solutions with our customer base and has a number of proven offerings in the marketplace.

The area of limited focus today is the adaptation of equipment monitoring to the acid plant to increase availability and meet the specific needs for predictive maintenance

Autonomous plant

We cannot discount the future possibility of an autonomous acid plant, however there are still many technological hurdles to overcome (without considering the regulatory issues). The proven success of the implementation of modular digital solutions in the acid plant will be a significant milestone in the long road towards an autonomous plant.

The inherent mechanical design and maintenance skillset required for such plants will be significantly different to that employed today and this is likely to be also be a incremental development, rather than a step change within the industry.

Ultimately our customers decide on the future of our industry and they must be also able and willing to take the leap of faith in such an ‘autonomous adventure.
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