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Malhotra, Girish, PE
Chemical process simplification : improving productivity and sustainability/Girish Malhotra.
p. cm.
Includes bibliographical references and index.
ISBN 978-0-470-48754-9 (cloth)
1. Chemical processes. I. Title.
TP155.7.M355 2011
660’.28—dc22

An opportunity to write about one’s experiences and methodology to review, develop, solve, and simplify processes can be a challenge. However, if one is taught and trained by excellent teachers, colleagues, and supervisors, the challenge can be fun.

I was presented with this opportunity in 2008 and I am thankful to the people associated with my career. My thanks are to many but a few people stand out. Among teachers are Mr. Shiv Narain Das Gandhi, Mr. J. P. Srivastava, Professor D. D. Arora, Mr. B. N. Tandon, Professors Dr. R. D. Tiwari, Mr. R. P. Singh, Dr. J. B. Lal, Mr. S. B. L. Sherry, Mr. Himmat Singh, and Dr. W. N. Gill. Among colleagues and supervisors are Dr. Chester Snell, Mr. Edward Cave, Mr. Keith J. Conklin, Dr. A. K. Nanda, Dr. F. W. Sullivan, Mr. F. E. Butler, Mr. R. D. Hardy, Mr. K. Haber, Mr. Juan Jarufe, Mr. C. G. Ivy, Dr. B. G. Bufkin, Dr. R. E. Medsker, Dr. Richard Thomas, Dr. Charles Kausch, and Mr. Steve Waisala. I am also thankful to all the operating colleagues who shared their insight and supported me. As a matter of fact, since the operating personnel are the ones who must live with any design flaws, they have the uncanny ability to simplify the operating methods; their insight gave an excellent perspective of processes and the challenges they faced. Their perspective and creativity was always valuable.

We humans are creative individuals, and due to the rigors of 24/7/365 operation, we want to have processes that are repeatable, require minimum attention, and deliver quality. In this effort, well-trained operating personnel also want to minimize pollution, effluent discharge, and maximize on-stream-time. Similar operational strategies apply for batch processes. In their effort an experienced operator is the best friend who can critique a process before it is commercialized.

There are other methods and ways to address other and similar challenges. Methods discussed here have helped me to rationalize, solve, and create solutions.

The book’s title is very much what I believe for any manufacturing operation. Our creativity, imagination, beliefs, persistence, and enthusiasm are the key to simplicity and sustainability of the process. These are not the easiest things to share and sell, but are the key to one’s success. Increasing “profitability through simplicity” has been my mission and it is an exhilarating experience. At one point in my working career, during a discussion I realized that we figuratively work for a corporation through its hierarchy, but we really work for ourselves, as we have to deliver our best. Results of our efforts might not always be to our expectations, but the experience provides a valuable lesson that no university or school can teach us that. No one can take these experiences from us.

The experiences I have had at each of my employers and with my clients have been unique and cannot be duplicated and/or repeated. After discussions with some of my colleagues, we agree that a “can do attitude,” camaraderie, and creativity rubbed off on each other and enabled us to do things that previously would have been considered impossible. I have to thank all of my colleagues who helped me in my learning experiences.

I also thank my parents, Mr. and Mrs. G. D. Malhotra, who gave me the freedom to do what I wanted to do, considering the culture and environment of growing up in India. I would also like to thank my brother and his wife, Mr. and Mrs. Umesh Malhotra, for their unending support and encouragement. Last but not least, I am thankful to my wife, Dr. Indu Malhotra, for her objectivity, simplicity, and cheering that helped in this whole process. Our children, Mrs. Malvika Paddock and Dr. Rohit Malhotra, in their own ways helped me to stay on track. I am delighted and thankful.

Chapter 1

Process Simplification: Basic Guidelines

In today’s competitive world it is necessary to have the highest-quality product at the lowest cost. In addition, products must be safe and environmentally friendly. Most manufacturing processes, even the best, can be improved to reduce cost and enhance product quality. At times process simplification/improvement may seem like a formidable task, but every step in that direction is a satisfying experience. Since we are trained to apply our knowledge and experience to achieve such objectives, these tasks should be easy.

At times, process simplification can result in the development of an innovative technology that is superior to existing processes. It could be a better batch process or an improved continuous process. Such developments are the most rewarding benefit of the exercise. Each of the above reduces product cost and improves profitability.

Cost reductions are due to improved conversion of raw materials. They are also due to lower conversion cost of a finished product. Therefore, we have to make a continuous effort in each of these areas. A process of continuous improvement allows one to determine, design, and implement the best process for the product.

Cost reductions can also be due to the use of cheaper raw materials. Replacing an existing raw material with a lower-cost raw material has to be part of improving the continuous process effort. Many of the processes, especially active pharmaceutical ingredients, use multiple solvents in a process. Reduction to a single solvent has multiple benefits. Cycle-time improvement improves profitability in two ways: It lowers the conversion cost, and it adds production capacity at minimal or no investment.

If we are able to improve the conversion yield for any product, we are implementing an environmentally sustainable process. Sustainability means “meeting the needs of the present without compromising the ability of future generations to meet their own needs.”¹ This is a good definition but I like to modify it to say “exceeding the needs of the present and giving the future generations ability to exceed their own needs.” We have to strive to meet a higher goal if we are to be able to meet the expectations of future generations.

In the early seventies when I was at the Illinois EPA working on hydrocarbon emission standards, I recall that during the public hearings the standards were considered to be tough and were challenged by the industry. As the standards became law, industry benefited not only from the savings of raw materials but also from lower conversion costs, since the new regulations led to improvements of the existing processes and the development of innovative processes.

During my tenure at the Illinois EPA I had denied an operating permit to a chemical company because its operation exceeded emission standards of a potential carcinogen. The permit was granted after a reasonable control plan was submitted. About 16 years later I met one of the executives from the same company. He was thankful for our actions, as the company realized a return on investment in a much shorter time than had been anticipated. It had also allowed the company to implement the improvements throughout the operation.

Thirty years later the hydrocarbon emission standards of the early seventies are considered too lax. They were a start. Industry and government collectively have improved the environment. We still have significant opportunities.

Since we are going through a global energy crisis, it would be prudent to figure out how to improve process efficiencies including internal combustion engines so that we can all benefit for the long term. We have to challenge the status quo and strive for better methods. We should not be thinking that it can’t be done but looking at what and how it can be done. The current global slump is the best time to rationalize and improve process efficiencies. The goal has to be “innovate, innovate, and innovate.”

My purpose in this book is to share my experiences with readers and suggest how we can apply and use our educational and industrial knowledge to simplify and improve process development and manufacturing operations. Readers should not feel that everything has to be done just as I did it but should use this book as a guide for your applications and needs. I have used a few “basic rules of thumb” in my career. This list can be augmented and/or modified to include readers’ own experiences. Some of my rules are worth reviewing:

1. There are no failures. Every experiment is a learning experience. These experiences add to our knowledge base and allow us to do a better job.

2. Every dollar we spend has to be earned. My basic rule has been that, under the standard business models, if we are able to increase revenue by $100, we should be able to spend after tax $10. If revenue increase is not the goal but we need to invest to improve the process, then we should save $2 for every $1 to be spent. I have used this benchmark. It may be considered a challenge, but it forces one to be innovative and creative in process selection. I consider this rule as my “breakeven rule.” It can be modified to suit individual business needs.

3. We should never hesitate to look outside our business comfort zone for simpler ideas, and we should cross-fertilize. Industry A might be doing the same thing that you are doing but have figured out how to do it better.

4. We should keep in mind that we are dealing with chemicals that many times are alien to our body and our environment. Anything that is alien to our body and environment can be detrimental, as we do not exactly know how it will interact. Thus, it is important that we respect our body and sustain our environment. We will leave a legacy of our deeds.

5. Patents are excellent tools that show what is possible for processes and chemistries. They provide a wealth of information especially for the chemistries and processes that have been and are being invented. Many outline how a process is being executed in the laboratory. They also suggest how the process could be commercialized. Deciphering information can be a challenge but is worth the effort. We need to capitalize on these opportunities.

6. In chemical processes, mass and heat balance are true reflections of the thinking and vision of the developer and implementer or commercializer. They are great educational tools. An actual mass balance reflects the status of the current operation and is a starting place for improvement opportunities.

7. We must document everything we do. It is hard to do, as we are in a hurry to move on to tackle other challenges. Saying “No job is complete without the paperwork” is very apropos.

The above rules are applicable to any manufacturing industry. They are especially applicable to industries that use chemicals. This would include situations where chemicals are reacted to produce a new chemical entity and/or blended for an application to facilitate our lifestyle. In process simplification and operational problem solving, developing a checklist² might be helpful. All of us have our mental checklists, but we do not call them a checklist. An organized list on paper should be created and updated with time. It will not only improve the process, but will also result in a safe process and can be used as a training tool.

We humans are the best innovators. If we can go to the moon and come back, we can do almost anything. We want to make our jobs and lives easier so that we can enjoy them. We like to bask in our laziness. After we have enjoyed a good result, we move on to a new challenge.

In order to avoid any stalemate that develops in a project, I have always used a simple methodology of dividing the project at hand into the smallest pieces/steps. A review of all the process steps, allows me to improve each. Let us take an illustration.

Let us assume that a process has five steps: A, B, C, D, and E. We need to review each step individually and collectively. They do not have to be reviewed in the processing sequence. Random order can be used for the review. If process step C can be improved before the other steps, we should implement this improvement to gain its benefit. This not only gives us confidence but also wins over our colleagues. They help us more, as we have facilitated their job. Small wins lead to big wins.

Every manufacturing company has business components that relate directly to the produced products. These include research and development and manufacturing. Process development and process engineering are part of R&D. Maintenance is a critical manufacturing function, needed to keep operations humming all the time. Every other function, such as quality control, shipping, inventory management, sales, accounting, and marketing, are complementary functions of the total business process.

My “rules of thumb” can be applicable to different functions of any manufacturing operation. I will focus on process development, process research, and manufacturing functions.

APPLICATION AREAS

My focus is on specialty and fine chemicals, active pharmaceutical ingredients, paint, paper making, electronic and electroplating chemicals, adhesives, dyes, colors and pigments, and food. These products can be classified in the following two general categories:

Classification of products in these two general categories is an oversimplification. The fundamentals of chemical engineering and chemistry are applicable, thus there are many commonalities. This not only has allowed me to give a clear and clean view to the challenge at hand but also to cross-fertilize technologies and practices. Since there are commonalities of chemistry and application of engineering principles, compliance with different regulations and safety requirements is simplified.

As we graduate from universities and gain experience in an industry, we generally get labeled as expert in the industry of our first employment and are not considered suitable for other industries. I believe cross-employment has higher value as it offers a different perspective. I would like to illustrate this by the following example.

Organic and inorganic chemicals are reacted to produce a chemical. The created chemical does not know where and how it can be applied and used. If our fundamental knowledge of chemistry and unit processes and operations is strong, we should be able to produce a variety of chemicals for different applications, whether they are a reaction product or a blended product. In certain cases specific knowledge might be needed but that should come in the way of experience of the chemist and engineers.

This is illustrated with the following example. Common salt (sodium chloride) is used in food to enhance taste or treat roads during winter, among many other applications. This does not mean that to mine salt we need personnel with training for each application. However, we do need an engineer who can safely mine and an engineer who can process salt for the different applications.

Similarly, an organic chemical could be used as a flavoring, a UV initiator, a sweetener, a herbicide, an active pharmaceutical ingredient, or an additive by reacting with different chemicals. It is the ingenuity of the chemist and chemical engineer to have an optimal process to produce these chemicals. The chemist and/or engineer should not be labeled a specialist in application/product “B or C,” but considered as an innovator who can deliver a quality product safely at the lowest cost. If we classify chemists and engineers based on their past experiences, we are depriving ourselves of their cross-creativity and innovation skills. Commonalities and cross-fertilization provide advantages as they reduce learning and process simplification time. They also bring new thinking in the development of products and processes.

We as chemists and/or chemical engineers need to learn and understand the physical properties of the raw materials and intermediates involved in a reactive and/or blending process. We also need to understand their interaction, reaction chemistry, and kinetics. This knowledge of the chemistry, components, and interactions gives us the capability to control and manipulate the processing conditions. We can be creative and imaginative in improving and developing new processes that will have the following characteristics:

Knowledge and command of the process variables eliminate any process deviations. This knowledge can allow the development and implementation of continuous processes, which we know are economical and better compared to batch processes.

Use of acronyms such as QBD (quality by design), QBA (quality by analysis), DS (design space), CMC (chemistry, manufacturing, and controls), PAT (process analytical technologies), or any other used by various regulatory agencies to encourage companies to improve their manufacturing technologies become redundant as knowledge of the physical properties and reactions becomes the fundamentals of any chemical-engineering curriculum. Use of these acronyms creates confusion due to variable interpretation.

Imagineering, blue-sky dreaming, and ideation for process and technology enhancements are of considerable value. They lead to innovations. We need to capitalize on “out-thinkers.”

Process simplification and innovation are always and will be a “selling” challenge at any company. In September 1973 during a job interview I was asked, “Are you a salesman?” My answer was that as a practicing process engineer I have no experience in sales. I was told that all of us are in sales whether we are a chemist, engineer, or manager, as we are always selling our ideas. The value of this advice has been insurmountable. Many times we are given advice by a colleague and/or in a good book but do not fully adopt it. We should.

REFERENCES

2. Gawande, Atul. The Checklist Manifesto: How To Get Things Right Metropolitan Books, 2001.

Chapter 2

Process Solutions

Solving process problems is an exhilarating experience but equally a humbling one. Many of us might recall the expression “The thrill of victory and agony of defeat.” Solving process problems is a similar challenge. Many may not equate these challenges, but to me there has always been a lesson in how overconfidence can teach you something valuable. Solving a process challenge is a gratifying experience. In solving problems there are no failures but rather learning experiences, which makes you better equipped for the next problem.

Processes, especially continuous processes that operate 24/7 can break down at any time. A solution is needed instantaneously so that production does not suffer. “Process on stream time,” whether for a batch or a continuous process, has to be maintained at the set standard; otherwise there will be a cost variance.

Early on in my career, it was suggested that I should be so familiar with the equipment and process that I could visualize each valve and turn of the pipe when called at any place and at any time to solve a problem. It seemed like a difficult task but was one of the best pieces of advice I have had in my career, as it helped me in solving many process challenges. It also assisted me in “daydreaming” process simplifications and innovations.

EXAMPLES OF PROBLEM SOLVING

Mass Balance

Mass balance is an important tool for any manufacturing operation. Its value is significant, as it can be and should be used for monitoring any process on a daily, monthly, and yearly basis. I found it extremely useful, as it allowed me to take preventive and corrective measures if the mass balance deviated from the standard. Mass balance also forms the basis for the factory cost of the product.

The value of mass balance was impressed on me early on when I was earning my undergraduate degree in India. The chemical-engineering curriculum requires practical training at manufacturing plants after the third (junior) year and the final (senior) year before graduation. Each student had to spend four weeks at the allocated sites.

I was at a fertilizer plant and the plant manager asked me to complete the mass balance of a key distillation column. The report was due at the end of my training. It seemed like an easy task until I had to do it. I understood the theory behind the distillation column, but the process operators taught me the practical nuances of various unit processes and unit operations. This showed me for the rest of my life to learn from the operating personnel, as they will teach you the practical, easy, and difficult parts of the process. If one is able to simplify the difficult part of the process, you earn your stripes and you have a friend.

During the four weeks the plant had to change the distillation column packing. I had read about the packed distillation columns but had never seen one from inside. I was asked to enter the column with the full safety paraphernalia. It was a challenge. I saw the guts of a unit operation that normally one does not get to see. Getting your hands dirty helps, as you can easily associate with the plant personnel who have to live with the engineer’s good or bad designs.

At the end of my fourth year I was at a plant producing DDT (dichlorodiphenyl-trichloroethane), an insecticide used against malaria. My task during the training was to write the process description, chemistry including chemical structures for each of the raw materials, byproducts, and the product. I also had to prepare a mass balance. It was a challenge but well worth the exercise, as I learned the value of mass balance. For the first time I understood the value of yield and effect of the operating conditions on the process. It taught me how the chemical reactions produce many molecules on a commercial scale, how unit processes differ, and how chemicals can be manipulated to produce a new chemical entity.

This plant also taught me the value and respect of conservation, environmentalism, and human health and safety. The plant was clean but, like any chemical plant, it had its unpleasant sides. On the plant site you could smell the chemicals and feel the DDT dust in the air. None of the obvious places (e.g., dryers) had major leaks, but they were there. One could taste DDT in the water in the cafeteria. It suggested that somehow the process water was getting in the plant water supply, but I was helpless. I also did not understand the ill effects of chemicals. However, they left an indelible impression on me to protect the environment and its impact on human life.

Mass balance includes understanding the materials that are used and produced in the process. This facilitates their manipulation to develop and improve processes.

Monitoring Plant Operations

During my association with the manufacturing plant, we did mass balance for each product every 24 hours. The information included storage tank inventory, in-process material, and changes in the finished-goods inventory for the product. This was a ritual and could be considered overkill, but we lived by these rules. It gave a very good picture of the last 24 hours of the process yield and accounted for all the downtime and any other issues. We tracked our downtime, and every preventive and corrective measure was understood and planned.

Mass balance allowed us to compare and track 24-hour yield against the standard yield. Yields lower than standard were investigated and corrected. This instilled the process of “continuous improvement” in us. It also allowed us to take steps to continuously improve processes to achieve higher yields and improve “on-stream time.” In my efforts to solve and/or improve any process challenge, I ask for a mass balance of the process. It is a quick study and reduces the time to address product and process challenges.

Filter Feed Pump

Early in my career in one of my assignments for a process expansion, we had decided on a strategy of stepwise expansion as the process operated 24/7, thereby minimizing downtime. The process had seven unit processes. Based on the mass balance and equipment design criterion, we decided to expand the filtration step first.

A mass balance for the expanded capacity was prepared. Analysis suggested that we would need a higher flow rate at the filter feed pump. I designed the pump, and during a downtime the new pump was installed. The filter was an inline belt filter that used a vacuum to dewater the slurry. As soon as the plant came back on line, the slurry being fed to the filter, instead of having a granular feel, looked like a fine milk shake. Slurry would run down the filter and nothing would filter through. Every effort, including throttling the pump feed valve and lowering the motor rpm, was tried in order to simulate the lower-capacity pump, but nothing worked. More than 24 hours had passed since the installation of the new pump. We checked the design calculations and flow rates and even talked with the pump vendor. The plant could not produce a single pound of the product. Ultimately we decided to reinstall the old pump, and the plant came back on line.

An analysis of the slurry indicated that that the pump impeller also acted as a homogenizer. The slurry became so fine that it would plug the Büchner funnel filter in the laboratory and nothing would filter through. Since we were discharging at atmospheric pressure, ultimately we realized that there was no need to change the pump. We quadrupled the plant capacity but never had to change the pump.

This incident of pump failure always stays in my mind and suggests that a complete problem analysis is necessary. It was a learning experience.

Ester Manufacturing Process

In my job I had moved from process and technology development to manufacturing operations. There I had to live with my process developments, designs, and commercializations and their flaws, whatever they might be. Moving from R&D to manufacturing is a culture change and is worth the challenge. It teaches us how to think and solve problems on the spot. If you get an opportunity like I had to cross-train, you should avail yourself of the opportunity, as it is an enlightening experience.

We produced an ester and used sodium bicarbonate, a mild alkali, as a catalyst for the process. The ester was used to produce a food-grade product, an herbicide intermediate, and a food flavor. Since carbon dioxide was liberated as a reaction byproduct, addition of the solid raw material even with a defoamer was a challenge. Increased amount of defoamer added to the product impurity profile, which interfered with the flavor specifications. We produced about six to eight batches per 24 hours using two existing reactors. We had been using the technology outlined in textbooks. We had tested an alkali in solution instead of sodium bicarbonate in the laboratory. It did give us good yield, but we never commercialized it.

Demand for one of the downstream products of this ester suddenly increased. We needed to double the plant capacity. We did not have the time for a plant expansion. We had to improvise using the existing plant.

We installed a metal deflector at the bottom of the solid feed chute. This minimized wet carbon dioxide to moisten the incoming solids and plug the feed chute. It allowed us to feed the solid as fast as we could feed. Gas evolution did not interfere with the feed, as the metal deflector minimized gas to the dust-collection bag house-mounted at the discharge of the solid feed screw conveyor. Reaction was exothermic. We raised the reactor temperature and controlled it such that it would evaporate some of the alcohol but condense in the reactor top dish and the condenser. Condensing alcohol acted as a scrubber and washed any solids trapped in the gas back to the reactor. This prevented any plugging manifested by lack of pressure buildup in the reactors. We also washed the condenser with the alcohol used in the next batch to clean the condenser tubes, making sure they were clean. We were able to more than double the process capacity and produce 14 to 16 batches per 24 hours to meet customers’ needs (see Figure 2.1).

Our ability to increase production using a batch process gave us a number of other ideas, and eventually we converted our batch process to a continuous process. A recent U.S. Patent 7,368,592 (process for the preparation of alkyl N-alkylanthranilate) discusses some of the ideas that we were practicing in the early seventies. Based on my experience the chemistry of this patent can be further simplified, and a yield higher than 80 to 85 percent can be achieved.

Simplification of a Product Solution Process

We produced a product in two forms, a 100 percent solid and a 50 percent version. The product was distilled and the liquid granulated to a solid for sale. To produce the 50 percent solution, the solids were drummed on the first floor and then taken to the third floor and manually dumped in a 4000-gallon tank. Hauling 200 to 220 fiber drums weighing 100 pounds each was an arduous and labor-intensive task. In this process over time we would eventually replace all of the fiber drums. The APHA (American Public Health Association) color of the product was on the high end of the spectrum. Even though the product performance was not affected by the color, high color was perceived to be of lower quality. Due to perceived low quality of the liquid solution, competitors were anxious to enter this lucrative business.

Reviewing the process, we decided to install a three-way valve to divert the distilled liquid to the solution tank. Since the tank was on the load cells, we could control the liquid feed to the dissolution tank. In addition, we were not exposing the distilled liquid to air (as is done in the granulation process); we had a tenfold drop (lack of air oxidation) in the APHA solution. This modification not only improved product color but also reduced our cost and allowed us to increase our total process capacity. We kept competitors at bay. We could simultaneously produce solution and granules if the product demand warranted.

Process “On Stream Time”

In manufacturing it is important to have a high “on stream time (OST).” In plant or process operations the actual time that a unit is operating and producing product is important. OST is a relationship between total available time for manufacturing and the time the product is actually being produced. Table 2.1 gives the generally accepted definition.

For each of our 24/7 operations, the target was to have better than 85 percent OST. This means that we allowed 1260 hours per year for maintenance, repairs, modifications, and cleaning. If we used more than 1260 hours for these chores, our OST would be lower than 85 percent. This might look like a significant number of hours, but in the manufacturing environment it passes very quickly and one has to be very diligent about downtime.

One of our processes, due to its inherent nature of the raw materials and process intermediates, would coat the piping of a continuous process as the time progressed. The pipe diameter would reduce from two inches to a lower size, and eventually flow could stop. Traditionally a planned cleaning was done after the production rate dropped by a certain percentage. Cleaning could take longer than the planned or expected time. This would result in our monthly OST dropping well below 85 percent. The average production rate would drop to about 2500 to 2800 pounds per hour, below our design capacity of 3000 pounds per hour.

Our goal was to improve the OST and production rate. I met with the operating personnel to discuss every option to improve the operation. Cleaning was our largest downtime contributor. We decide that instead of cleaning the process piping as had been done in the past, we would clean every 48 to 60 hours.

Our idea was to minimize the buildup by giving the equipment a quick clean. We documented the needed cleaning time and the subsequent operating rates. After a few weeks we reviewed our operating rates and OST data. We were delighted to see that our OST jumped to more than 85 percent, and the operating rate increased to about 3200 pounds per hour, better than the designed rate.

This improvement allowed us to produce above our budgeted rates. It was also very timely, as the demand for a downstream product increased, consuming every pound we could produce. We achieved our objective of meeting customer needs without any investment and also increased our profitability. This gave us the flexibility to shift our production from 24/7 to 24/5 if it was necessary. Since we were overabsorbed on our variances, we did not lay off anyone and used the spare personnel for other needed tasks. It was a morale booster for the site.

The concept of earlier than planned cleaning can be applied to any process where piping and/or equipment cleaning is necessary. Membrane cleaning, such as in biopharmaceuticals, ultra-filtration, and the like, are good examples.

Inventory Management and Process Repeatability

Since I had moved from process development and R&D to manufacturing and I did not know any better, I had no preconceived notion of norms for the inventory. My goal was to smooth out the monthly production so that we could minimize the end-of-the-month sales rush.

I also had the luxury of managing the raw material, in-process, and finished goods inventory to as low a level as I chose so long as I could meet my production rates and the sales demand. I considered inventories to be an “operational evil” of any process. In order to minimize this evil, my goal was to minimize the inventories.

To achieve this goal, I made every effort to understand our processes, their pitfalls, and their break points. This exercise was helpful, as we could repeat our operational mistakes and correct them. During my operation days (1979-1984) our goals were to operate with close to minimum inventory and produce quality the first time (six sigma in today’s terms).

Since we had excellent control of our processes and “on-stream time”—i.e., we could produce and supply customers as they placed orders—our orders leveled, and this gave us an opportunity to minimize the inventories of raw materials, in-process materials, and finished goods. With the help of our purchasing and other support staff we operated by maintaining inventories in the range of one to two days for any of the raw materials, one day for in-process materials, and two days of regularly scheduled finished products. We were able to achieve these goals. The cash flow of the profit centers was excellent.

Sampling and Size

In every manufacturing operation, it is necessary to test the intermediate samples at prescribed points and also check the final product sample. Sample size for any analysis used to be a quart (liter) sample. Most of the time the samples were disgarded after testing and would end up in waste. In those days environmental laws were very lax compared to today’s standards. In our operation, change from a liter sample to a 250 ml sample was met with significant internal resistance. It was like going upwind. To get around this dilemma, the plant decided to have sample accumulation drums. This encouraged recycling and waste minimization. Eventually everyone understood the value of small samples, and the plant settled on 250 ml or less.

The concept of minimum size samples has stuck with me. It is not only an effort to minimize waste but also to improve yield. Leftover samples should be recycled if possible, and/or sample size should be minimized. Samples have significant value when the products are expensive. Reduction of the sample size is an effort to green the process. In order to have a representative sample, a careful review of the sample point, method, and size is necessary. Flush valves are available, and they should be used wherever possible. They are worth the investment.

Recently a process audit at a client business indicated that four one-quart samples were being taken during the batch. The samples after testing were being discarded as waste. After discussion with the laboratory personnel of the contract manufacturing organization (CMO) it was indicated that they did not need a quart sample per test. They were just following the established procedures. It turned out that 100 ml per sample was sufficient. The reduction of sample size and recycling saved them in excess of $600,000 per year.

Sample taking is a simple exercise but a critical place where yield loss can occur with a small batch and an expensive product. Many times this is overlooked. Better sampling valves have been developed and are commercially available. They should be considered.

Antioxidant Production

An antioxidant was produced at a plant by reacting a substituted phenol with formaldehyde in presence of a catalyst. The process as defined had a simple chemistry and a reasonable stoichiometry, suggesting little more than two moles of formaldehyde should be used for the process. However, the process produced quality product randomly—i.e., we could never predict which batch would meet specifications. The batch charges to the reactor were weighed and meters were calibrated to decipher the cause of our inability to produce quality product. However, the problem persisted. If the product was not going to meet specifications, it would only show up at the filtration step, as the centrifuging would be a problem. With the provided stoichiometry it would take about five 24-hour days to produce two to three batches per week.

Since the plant was purchased from another company, there was not much information available about the chemistry and the process. Our only choice was to reinvent the chemistry in the lab and compare it to the actual chemistry being practiced in the plant. Based on mass balance, about 20 percent excess formaldehyde was being used per mole of the key raw material. Since the theoretical chemistry asked for two moles of formaldehyde, experiments using 5 to 8 percent excess formaldehyde were tested in the lab. The laboratory batch met specifications. The process in the laboratory was very easy and clean. We reconfirmed the batch in the lab with excellent results.

Since the customer orders needed to be filled and we had enough confidence in two to three lab experiments, the process was commercialized. Formaldehyde needed for the new process was less than the handed-down recipe. The process yield was about 90 percent, and the product quality was higher than the established specifications. The plant was able to produce five batches per week compared to the earlier two to three batches per week. Analysis of the product produced using the new stoichiometry suggested that the excess formaldehyde produced by-products that caused filtration problems and also resulted in off-spec product.

Mass balance and attention to stoichiometry not only solved the problem but also allowed us to produce more product in less time, adding to the profitability of the plant. As I have indicated earlier, monitoring mass balance keeps track of the process yield. In addition, it monitors the pulse of the process. Operational problems will show up and should be resolved immediately.

The acquired plant produced another antioxidant, which was one of the major products for the site. However, we were losing more money than can be imagined. Our task was to fix the technology and the operation so that we could return to profitability.

Our first task was to understand the chemistry and the process and create a mass balance. Creating a mass balance was a challenge, as the necessary systems and support were limited at this acquired facility. This was complicated by the fact that some of the residues were being sent out for recovery and disposal. Mass balance should normally close if one has control of the process and an understanding of every process stream. Closing the mass balance is accounting for the process and establishing an actual yield. With limited resources, we developed a quick analysis for each process stream. A large gap existed between the theoretical and the actual yield.

To account for the gap, information (capacity, configuration, and calibration) about every tank was compiled and chemical analysis of every major stream completed. Under the established practices, we recycled process streams to recover raw material. The distillation bottoms were being sent for disposal. An analysis of the material being sent for disposal indicated that the waste stream was 90 percent product. Since it was pitch black, not much attention was being paid to it. The company was paying money to get rid of it. Disposal was immediately stopped and measures put in place to recover the product in-house.

Available time/year, hrs.	85% OST
350 X 24 = 8400 hours	= 8400 X 0.85 = 7140 hours