Process innovation pays

The petrochemicals sector needs to cut capital and operating costs in the face of rising feedstock prices and increasing regulatory and commercial requirements to be more energy efficient.

In the developed world, in particular, the petrochemicals industry is under growing competitive pressure to be more versatile in its responses to changing customer demands.
The major means of satisfying these needs could be greater process intensification. This would in the longer term mean that there would be much less reliance on larger, costly energy-intensive plants. Instead there would be a preference for smaller, less expensive and more energy efficient units, which have a lower environmental impact, greater safety and would be easier to operate.

For Europe and Japan, where there is a necessity for greater international competitiveness, lower  feedstock and energy costs and quicker reactions to market changes, process intensification could offer an opportunity to take a global lead in the introduction of new more economical petrochemical production technologies.

Yet process intensification innovations have been available to producers since the early days of the petrochemicals sectors in the 1950s. The industry has been taking a long time to adopt them on a wide scale.

Instead, the general trend has been for petrochemical plants to become bigger and bigger. A few decades ago, ethylene crackers were being built with capacities of around 100,000-150,000 t/year. Now the annual capacities of new crackers are over 1m t and rising.

When plants are growing in size in order to exploit economies of scale, the argument in favour of smaller facilities has been dismissed as irrelevant or too risky.

Large plants have proved themselves to be highly profitable within a business cycle. By contrast, process intensification technologies have been handicapped by a lack of performance data.

Furthermore even if they could show commercial potential,  the necessary alterations to infrastructure, like storage facilities, and to supply chain structures have still been regarded as making them uneconomical.

In recent years, particularly in mature petrochemical sectors like the European industry, the fact that many older plants have paid off their capital costs has made process intensification initiatives even less attractive.

‘There is undoubtedly considerable scope in the petrochemicals sector for redesigning processes to make them more economical and cost effective,’ says Paul Hodges, chairman of International eChem (IeC), a London-based consultancy.  ‘But in areas like Europe there is less opportunities for process intensification in petrochemicals than in other chemical sectors because of a well-established infrastructure and the age of plants.’

At a time of global overcapacity in many major petrochemical products, there is strong reluctance among senior executives in petrochemical businesses to commit funds to new projects unless there are clear competitive advantages.

‘Process intensification would sharply increase yields in terms of inputs as a result of a big reduction in the size of plants,’ says one European chemical engineering academic.  ‘But in addition to the innate conservatism of the sector, companies fear being the first in the market with a new technology.  They would like someone else to try the technology first.’

here are knowledge gaps in process intensification in bulk chemicals.  Much of the expertise in the area is being concentrated on achieving production improvements in fine and speciality chemicals and pharmaceuticals. Yet if process intensification is to advance in petrochemicals, technological standards need to be drawn up based on experience in the operation of plants.

‘Bulk commodity polymers will only be efficiently produced, when standardised process-intensified and modular concepts are available,’ says Helmut Mothes, chairman of the strategic advisory board of the European Process Intensification Centre (Europic) and a member of the management committee of Bayer Technology Services (BTS).

For a few decades, development work on process intensification tended to focus on specific production phases like reactive or catalytic distillation, dividing wall column distillation (DWC) and reverse flow reactors (RFR).

Reverse distillation, which combines reaction and distillation through catalysis in a single piece of equipment, was first applied in chemical production in the early 1950s. Its development speeded up in the 1980s because of the need for ways to cut capital costs and to make energy savings.

Eastman Chemical started commercial scale production of methyl acetate through reactive distillation in the US in 1980 after a period of extensive development work in a pilot plant.  The process combines five functions in a single column.

Catalytic Distillation Technologies (CDTech), Houston, Texas, now a global leader in the development and commercialisation of catalytic distillation based processes for the chemical, petrochemical and refining industries, implemented its first reactive distillation technology in a methyl-tertiary-butyl ether (MTBE) plant in Houston in 1981.

In recent years, process intensification technologies like reactive distillation, which have been developed and improved over a lengthy period, have started to make much bigger inroads into the petrochemicals and refining sectors. 

In a study of process intensification in the petrochemicals industry published two years ago, Shell Global Solutions, the Amsterdam-based technology arm of Shell, estimated that there were over 150 commercial distillation units operating around the world. These were achieving capital cost and energy reductions of 20–80%.

With DWC, in which two distillation columns are merged into a single column with a dividing wall between the two but with a common top and bottom section, the first patent was granted in 1949.

But the requirements for cheaper capital costs and energy savings have led to a fast increase in its adoption, with over 100 units worldwide according to Shell. DWC’s capital cost and energy cuts range between 10% and 30%.

Similarly, over 100 reverse flow reactors were estimated to be in operation because of their lower capital costs and emissions. They combine the heating of the feed flow and the cooling of the product flow within a single fixed-bed reactor.

The increased adoption of these first process intensification systems has lowered the cost of their components and helped raise knowledge about them so that they can also be applied elsewhere. 

Membrane technologies, which have been used in reactive distillation as well as areas like upstream gas seperation, are now being implemented in a variety of process intensification initiatives. These include CO₂ capture in smaller separation units, the recovery of organic solvents from gas streams and the recovery of olefins and other hydrocarbon feedstocks in the production of polyolefins, in which losses of monomers in single plants can cost $1-3m/year.

Process intensification technologies are now also starting to have an impact on the design of major projects. Though still having large capacities, they are taking up less space, using less feedstock per unit of output and produce no or less by-products, which is one of the main benefits of process-intensified systems.

BASF and Dow Chemical opened the world’s largest commercial-scale propylene oxide (PO) plant in Antwerp two years ago with a capacity of 300,000t/year using a new jointly developed hydrogen peroxide to propylene oxide (HPPO) technology.

Due to process intensification elements within it, the plant required significantly less capital to build than a conventional PO unit. Since it produces only PO and water, it does not require additional infrastructure for handling co-products. Furthermore it has simplified input needs with hydrogen peroxide and propylene being its only raw materials.

Sean Milmo is a freelance writer based in Braintree, Essex, UK