by Roger Sowell 
This article delves into the world of one of the most practical of all engineering disciplines: the chemical process engineer. I hope to explain how we process engineers do at least some of the things we do, and why. The examples shown here may have applicability to those who read and write on subjects such as climate change, nuclear power, renewable energy, water shortages, and many others. All of the just-mentioned subjects are found on SLB. (see notes and references below)
First, what is a chemical process engineer? As I am one (as well as being an attorney at law), I can say that it is a person with a degree in chemical engineering who practices his or her engineering skills in process plants. Process plants encompass quite a variety of industrial plants, such as petroleum refineries, natural gas plants, petrochemical plants, basic chemical plants, air separation plants, synthetic fiber plants, agricultural chemical plants, agricultural or crops processing plants (i.e. corn refineries that produce ethanol), synthetic fertilizer plants, soaps and detergents plants, adhesives plants, and many more. My own career to date has given me first-hand experience in many of those categories, including petroleum refineries (of four types), natural gas plants, petrochemical plants (of many types), basic chemical plants, and air separation plants.
The process engineer (leaving off the word 'chemical') typically addresses a problem or considers a new idea via a seven-step process. These are, in order,
1) is it physically possible,
2) can it be made safe,
3) can it operate reliably over time,
4) can environmental impacts be mitigated, including post-operating life cleanup,
5) can it make a profit,
6) can it compete for scarce capital resources, and
7) is it the best among the available alternatives.
Each of these steps is discussed below. It is important, to a process engineer, to take the steps in order and not skip any steps.
This step may appear unnecessary, even ridiculous, but it is amazing (to me) how many people (typically non-engineers) who believe in and then advocate for processes or an article (meaning a thing) that violates one or more of the laws of physics. Consistency with the laws of physics is the meaning in this context of "physically possible." One sometimes hears, for example, that "everything is possible." That is just not true. There are many, many laws of physics, chemistry, and thermodynamics, that are immutable. As I mention in my speeches, no one has ever found a violation of the Second Law of Thermodynamics. I encourage the students and practicing engineers at my lectures to notify me at once if and when they encounter a Second Law violation, because I want to congratulate them, and be the one that notifies the Nobel Prize committee on their behalf. Once a potential idea, or problem solution, is examined and found not to violate any physical laws, and only then, does the process engineer move on to the next step.
Can It Be Made Safe
Safety in a process plant is not only required by law, it is critical to success. Success may be defined in many ways, but in this context it is sufficient to have success mean long-term profitability. This ties in somewhat to the next step, reliable operation. An unsafe plant typically has unexpected production disruptions, perhaps explosions and fires, process areas that will not function, injured or killed employees, and a host of other undesirable outcomes.
The process engineer examines the potential idea and evaluates the safety aspects. There may be, for example, high temperatures, high pressures, corrosive or abrasive materials, toxic gases or vapors, and unstable chemicals that could violently expand, explode, or spontaneously ignite. Other dangers could include very low temperatures, a tendency to solidify and block the flow, or emissions of dangerous radiation. This is only a partial listing of the many and varied dangers that exist in a process plant. There may be design or operating decisions that can eliminate the safety concerns, or mitigate them sufficiently to move on to the next step. If the safety concerns cannot be overcome, the process engineer stops the evaluation.
Reliable Operation Over Time
A process plant must operate reliably over time to be useful and profitable. The question is how to define "reliable." Process engineers usually define reliability by a percentage of time that a plant operates. Operating ninety percent of the time is a typically acceptable reliability. A process plant typically must be shut down at intervals to allow equipment to be repaired, cleaned, or have other services performed. Plants that operate with frequent but unplanned shutdowns have a low reliability and will suffer a reduced profitability. Profits are decreased as production decreases, from increased cost of repairs, and sometimes from re-processing unsuitable production. A process can have multiple negative impacts where unreliable operations combine with unsafe conditions, as above. Only where an idea can be designed and operated with sufficient reliability does the process engineer move to the next step.
Environmental Impacts Mitigated
A modern process plant must meet certain environmental requirements as defined in a multitude of laws. An idea for a new process must be evaluated for environmental impacts. There are at least three ways to eliminate or mitigate environmental impacts, including capturing and properly disposing the pollutants, dispersing the pollutants so that any toxicity is reduced or eliminated, and designing the process so that the pollutants are not produced at all. This last means is sometimes known as "green chemistry."
The process engineer examines the various regulated pollutants and evaluates the available means to meet the emissions requirements. The concept of Best Available Control Technology, or BACT, is common in the environmental world. As examples of "capture and dispose", toxic dusts may be captured in a filtering system, gaseous pollutants may be physically absorbed or chemically converted to benign chemicals, and liquids that have objectionable acidity or alkalinity (low or high pH) can be neutralized.
Dispersing pollutants is generally a last resort, but such systems are occasionally allowed. Examples include saline brine from desalination plants where the saline brine is introduced gradually and at multiple points into the ocean, treated water from a waste-treatment plant is also introduced slowly and over a wide area into a body of water (the Pacific Ocean receives treated water from a large waste treatment plant on the coast near Los Angeles, California), and tall smokestacks are required to allow the wind to disperse emissions.
Environmental impacts must include mitigating any impacts when a process plant is shutdown after its viable life expires. The US history is replete with hundreds of petroleum refineries and various chemical plants that have shut down permanently. Many of those sites required extensive and costly mitigation to clean the soil. Other process plants may have toxic areas that require special remediation.
Only where the process engineer can determine acceptable ways to design and operate a plant that meets all the environmental requirements does the next step occur.
The goal of (almost) every process plant is to make a profit, and a process engineer evaluates each idea with that in mind. Where the idea is physically possible, can be made adequately safe and reliable, and meets environmental requirements, the process engineer examines the potential profitability. This almost always includes an evaluation of capital costs, operating costs, and expected revenues. Importantly, an idea that requires a lengthy construction period will also incur substantial financing costs.
Many economic aspects of a new idea will be evaluated, including considering various sizes to take advantage of economy of scale, possibly modularized construction, competing technologies (if any exist), fees or royalties, plant location with respect to feedstocks and markets, plus many more. It may be possible to improve profit for plants that have high electrical power requirements when they can be located near sources of low-cost electricity, such as hydroelectric dams.
A key aspect is the cost to achieve improved reliability, especially long-term reliability due to corrosion. Process engineers understand that corrosion is a function of the material chosen for the various pipes and equipment (note, there are also many other aspects that impact corrosion). It may be possible to build a plant that does not corrode, if one had unlimited money and constructed the plant with titanium. At the other extreme, one could build a plant of carbon steel and replace the various equipment and pipes just before the corrosion renders them unsafe and unreliable.
The process engineer evaluates all the above, and many others, to determine the likely profitability of the new idea. Several measures of profitability are usually calculated, with one of the most commonly used being the simple payout time. A process engineer simply divides the capital cost by the annual net income (revenues minus operating costs) to obtain the number of years that would be required to pay off the capital cost. For example, a new idea that would cost $10 million to install, and has $2 million per year net income would have a 5 year payout.
Only where the simple payout time is sufficiently small, perhaps 2 or 3 years, does the process engineer move on to more sophisticated calculations of profitability.
Compete for Scarce Capital Resources
Next, a new idea is evaluated against other potential ideas or projects. It is common that only a finite capital budget exists, but the combined cost of the numerous ideas greatly exceeds the capital available. The process engineer then must evaluate the various new ideas and select those for implementation. The selection criteria and process may be complicated and require careful evaluation from many people in the organization.
One criterion that a process engineer uses is the simple payout time from above. Projects with shorter payout times almost always win over those with longer payout times.
Best Among the Available Alternatives
The final step taken by the process engineer may appear to be identical, or similar, to the Compete for Scarce Capital Resources step just above. However, in this context, the process engineer considers the overall wisdom of proceeding with the new idea. Even if the new idea could be built according to all the above criteria (physically possible, safe, reliable, environmentally adequate, profitable, and more profitable than competing ideas), the process engineer considers whether the new idea should be built.
There may be compelling reasons one might not want to build the new idea. Perhaps the new idea consumes resources that could be used in a different way or for a different purpose. Natural gas, for example, has been decried as a heating fuel and as a power generation fuel because it has great value as a building block for pharmaceuticals, agricultural chemicals, and synthetic fertilizer. Coal as a resource is also limited to approximately 50 years at this time, with its primary use as power generation fuel. It might be wise to reduce coal use as a power plant fuel and use it instead as a petrochemical precursor.
Another aspect is anticipated government regulation that would cut short the operating life of a new process plant or idea, such as occurred with mercury-based chlorine plants, plants that produced certain refrigerants, plants that produce lead-containing products, and plants that produce asbestos-containing products.
Application to Other Areas
The above discussion shows seven steps employed by process engineers. These steps are proven over many decades. But, are they applicable to non-process plants? The list at the beginning included climate change, nuclear power, renewable energy, and water shortages. Each is discussed below.
-- Climate Change
In climate change, the science is so shaky, so uncertain that it scarcely deserves consideration.   (see link and this link). When one considers how the climate data was and still is tortured, how definitive statements of man-made climate change are made - and then revised - and then revised again and again, how modern instruments with global reach show zero warming for almost two decades, how the best "climate models" disagree with modern temperatures, it is a wonder that climate change is considered a problem in the first place. Yet, solutions to any actual global warming, and more importantly, global cooling, can be addressed via the above seven steps. One must, first, reliably identify whatever is a substantial factor in causing global warming - or cooling. To date, global warming advocates believe that increased carbon dioxide in the atmosphere is causing unstoppable global warming. There is no evidence to support that belief, however.
If, and this is a big IF, it becomes necessary to reduce carbon dioxide inputs into the atmosphere, or remove some from the atmosphere, chemical engineers already know that it is physically possible to do so. Safety is a major concern, especially for the processes that capture carbon dioxide and store it in liquid form deep in the earth. A leak of liquid carbon dioxide into the atmosphere could and likely would suffocate thousands, if not millions of people. Process plants that remove carbon dioxide from furnace exhaust stacks have existed for many years, and a modern plant is now running near San Antonio, Texas. Reliability is not a major issue for these plants. Environmental compliance is also not an issue, other than the massive leak from storage described above. However, the cost to build and operate is a problem at this time. The major issue, though, is whether the great cost to build enough plants to make a difference is justified, considering the questionable science surrounding the entire climate change and human contribution to any historical warming.
-- Nuclear Power
Nuclear power is a frequent topic on SLB, and creates great disagreement and acrimony between proponents and opponents. As readers of SLB already know, my position is a nuclear opponent. The 30-article series on the Truth About Nuclear Power shows many excellent reasons why nuclear power plants should never be built.  (see link)
Yet, nuclear proponents continue with their beliefs that nuclear power is safe, affordable, and desirable. Nuclear power can be considered as two categories: proven and unproven technologies. As proven technologies, there are boiling water reactors and pressurized water reactors (BWR and PWR, respectively). Unproven technologies include thorium, fusion, high temperature gas reactors, and small modular reactors.
The arguments made by proponents for expansion of PWRs is that newer models are less costly and safer. Some even argue for relaxed regulations, and abolition of lawsuits during construction. Applying the seven steps, it is seen that the reactors are physically possible, but clearly not safe and not very reliable - especially as the plants age. Environmental risks and damage are very great, with highly toxic nuclear waste emitting dangerous radioactivity for hundreds and thousands of years. Costs to build have not been reduced but instead keep increasing, even though huge plants are built to achieve economy of scale. Finally, competing technologies for producing electrical power make nuclear plants not the best choice, including natural gas and renewable energy.
Unproven technologies barely pass the physically possible test, with fusion as yet only a theoretical but not demonstrated concept. Thorium plants also are physically possible but have major safety, reliability, cost and environmental concerns. The same is true for high temperature gas reactors  and small modular reactors. A major concern for thorium-based nuclear plants is the corrosion and cracking in the metallurgy that contacts the molten salt. Every heat exchanger with tubes will eventually leak, with material at higher pressure leaking into the material with lower pressure. The consequences of such leaks must be understood. It is astonishing to me that a great number of nuclear proponents simply ignore this basic fact of process engineering.
The final verdict on nuclear power is that proven technologies are vastly uneconomic, require massive government subsidies, and leave behind highly toxic wastes that endure for generations. Unproven technologies are even worse.
-- Renewable Energy
The renewable energy subject includes many technologies, solar in its various forms (photo-voltaic, concentrated solar, and solar ponds), wind both on-land and off-shore, ocean including waves, tides, sea-surface vs deep ocean temperature difference, and currents, river flow systems, pressure retarded osmosis at river mouths,  and bio-mass systems including land-fill methane capture, municipal solid waste burning, and water distribution pressure recapture. Many of the above technologies require some form of energy storage and release to provide increased value to the untimely or intermittent nature of the energy source. 
Physical possibility exists for all of the above renewable technologies. Safety is adequate or can be made acceptable. Reliability can also be made acceptable with sufficient design and investment. Costs are rapidly declining in most technologies as experience is gained and economies of scale are captured. Economy of scale exists for both larger individual units, and for mass production, and for single-events such as building transmission lines. The lack of environmental impact, or very low impact, makes renewables especially attractive. The eternal nature of the motive force, the sun, the wind, ocean waves, tides, and currents, and the essentially eternal production of municipal solid waste also make renewables especially attractive. As installed costs continue to fall but costs of other forms of electric power increase, renewable energy plants become ever-more attractive.
-- Water Shortages
Fresh water in adequate amounts is a greater and greater concern, even though some areas experience heavy rains and floods. Providing adequate fresh water essentially reduces to three technologies: building dams and storage reservoirs to hold and retain water during abundant years; desalinating ocean waters; and collecting then transferring excess water from areas of abundance to areas of scarcity. Those in the water industry also promote conservation, however that has a very limited benefit. Pumping groundwater from aquifers to the surface is also common in many areas, however the aquifers are generally not replenished as rapidly as the water is pumped out. Yet another (unpopular) technology is simply recycling treated water from waste treatment plants. This last has the great risk of transmitting disease via unclean water.
Technologies exist and are therefore physically possible for each of the three technologies (dams, desalination, and water transfer). (for water transfer,  see link) The technologies are safe and reliable when properly designed, built, and operated. Certain dams have failed with harmful or even catastrophic results, but those can be minimized or eliminated with proper attention. Environmental impacts are hotly debated, with some claiming great harm results from building dams and desalination plants.
The major issue with fresh water is cost, and in some cases, ownership of the plants. Water is such a vital part of life that many consider it too precious to be privatized except in very limited and controlled ways. However, some technologies are simply very costly at this time, especially desalination via reverse osmosis, RO, the most attractive process. A few thermal desalination technologies also exist, but are generally less economic than electrically-powered RO.
The seven steps of process engineers, physically possible, safety, reliability, environmental impact, profitability, most economic choice, and wisest choice, are used to evaluate a new idea or process plant. These steps should be used to evaluate other areas to provide a systematic and grounded conclusion. Having a blind and irrational faith in future innovations is not a good basis for allocating resources of time, talent, and money. Yet, a blind and irrational faith is what many people exhibit in their writings on many topics (especially climate change, and nuclear power).
At the same time, many people have far too little understanding of the technical and economic advances in renewable energy systems, and the associated energy storage and release systems.
Roger E. Sowell, Esq.
Marina del Rey, California
copyright (c) 2015 by Roger Sowell
Notes and references: (notes and references added 4-16-2016)
 Roger E. Sowell, B.S. 1977 in chemical engineering from The University of Texas at Austin, has worked as a Principal Process Engineer and consultant for 40-plus years in and with more than 75 oil refineries and petrochemical plants in a dozen countries on five continents. Clients include major and independent oil and gas companies, world-scale petrochemical companies, and basic chemical companies. Process plant assets ranged from the $100 million range, to $10 billion and higher. He has performed hundreds of process studies in process design, operations, optimization, and economics. Implemented projects have a cumulative value of the low hundreds of million dollars, and cumulative benefits exceeding $1.3 billion. He is published in Hydrocarbon Processing and CryoGas International. He has also taught engineering students at University of California at Los Angeles, University of California at Irvine, and made dozens of public speeches. He is also a Council Member with Gerson Lehrman Group, providing expert advice to member clients. He is also a California attorney-at-law, in Science and Technology Law, and publishes SowellsLawBlog. He was recently (2016) requested to defend climate skeptics in United States RICO actions. He is a founding member of Chemical Engineers for Climate Realism, a Southern California think-tank comprised of experienced chemical engineers.