When the vice-chancellor of our university declared that they had come up with their own anthem “Rasayan Devike” (Goddess of Chemistry), I thought he was crazy. Who does that, I said to myself. Until now.
It has been five years since I graduated from this university. Today, I found out that the concept took birth to spread awareness about green chemistry – how old chemistry could help clean up its act with newer greener chemistry.
There’s actually a statue of the goddess near the vice-chancellor’s office. Makes me wonder the length to which the university must have gone to engage people in environmental protection. What were the odds of being ridiculed? 100%? Probably, because I heard no one talk about it the way I’m doing it now. I have a newfound respect for this.
Chances are students barely knew what it was all about. It may have been nothing but a stunt for them. Not to me anymore. History is filled with mythological characters. People have devised ways to celebrate these characters and what they symbolize.
Which takes me to another train of thought. Have you ever heard of the God of Climate? There are many weather gods – wind, thunder, rain, lightning. None for Climate. As NASA defines, “The difference between weather and climate is a measure of time. Weather is what conditions of the atmosphere are over a short period of time, and climate is how the atmosphere “behaves” over relatively long periods of time.”
So, what am I proposing, you ask? I’m proposing a God of Climate, wait, no – a Goddess of Climate (it’s just more fun that way). I don’t know how this is going to help, but hey everything begins with an idea, right?
The word ‘chemical’ has always gained negative attention in the eyes of the public even when it enhances their lives. This is because of the side-effects it causes on the environment due to pollution and toxicity.
Kinds of chemicals:
The chemical industry basically produces 4 kinds of chemicals:
Commodity chemicals: Chemicals that are used by other chemical industries before becoming a consumer product. These are produced at huge scale. For example, petrochemicals produced in a refinery such as olefins and aromatics go on to become polymers.
Fine chemicals: Starting materials for speciality chemicals. These are of very high purity and are produced in limited quantities. Hence these are low-volume, high-value products.
Speciality chemicals: Pharmaceuticals, Dyestuff and pigments, flavours and fragrances, speciality polymers, catalysts and enzymes, food additives. These are consumer products.
Renewable energy: Biofuels such as ethanol, biogas.
These chemicals are produced using some basic unit operations and unit processes such as:
Unit process + unit operation = an entire chemical process
Unit operations involve physical separation of products that are obtained from unit processes. While unit processes involve chemical conversion of substances.
Some examples of unit processes are:
Fluid flow operations: e.g. fluid mixing
Heat transfer operations: e.g. evaporation
Mass transfer operations: e.g. distillation, extraction
Thermodynamic operations: e.g. refrigeration
Mechanical operations: e.g. crushing of solids, sedimentation
Note that these processes overlap i.e. they are interrelated. For example: Evaporation is both a heat transfer as well as a mass transfer operation as it involves the transfer of both heat and mass.
Chemical processes are capable of eliminating the pollution and toxicity that is caused by it. But how? Paul Anastas and Julie Zimmerman developed 12 principles of green engineering. These can be found in Env. Sci. and Tech., 37, 5, 94A-101A, 2003 or at ACS. These are similar to the 12 principles of green engineering because Chemistry and Chemical Engineering are interdependent on each other. Both of them can be viewed side-by-side here.
Green chemistry is the design of chemical products and processes that reduce or eliminate the use and generation of hazardous substances. Whereas, green engineering is the development and commercialization of industrial processes that are economically feasible and reduce the risk to human health and the environment.
A chemical engineer needs the following things:
Efficiency of the process: It should be efficient in all respects – energy or water efficient for example.
Safety of the process: It should be safe to carry out throughout its production line.
Financial feasibility of the process: If it is not profitable, it won’t work out.
Green engineering knowledge that helps achieve above points
Examples of green engineering:
Integrate Material and Energy Flows: Design of products, processes, and systems must include integration and interconnectivity with available energy and materials flows.
Optimization of heat is crucial for energy savings. Energy savings mean fuel savings. Fuel savings mean less greenhouse gas emissions. Pinch Technology provides such a thermodynamically based optimization methodology for energy saving in processes.
Renewable Rather Than Depleting: Material and energy inputs should be renewable rather than depleting.
Some unit processes/operations require heating. But what if energy comes from a green source? Energy required to heat a process is called as ‘Process heat’. It is often sourced from fossil fuels. A greener option in this case would then be a solar collector that can collect heat to be supplied to the process, termed as solar process heat.
Cogeneration or combined heat and power (CHP) is another technique to save energy. In this, the heat engine or power station simultaneously generate electricity and useful heat.
Some unit processes/operations require cooling. A major coolant in the chemical industry is water. It is used in large cooling towers. It has to be treated and reused since it can be contaminated with chemicals it comes in contact with. These chemicals could also be entrained by surrounded air and cause airborne emission problems. For this purpose, drift eliminators are used – an air pollution control measure.
Inherent Rather Than Circumstantial: Designers need to strive to ensure that all materials and energy inputs and outputs are as inherently nonhazardous as possible.
A part of my Masters thesis involved catalytic transfer hydrogenation. It is the transfer of hydrogen atoms from a donor reagent to a substrate under catalysis. It is supposedly the safest way to carry out a hydrogenation reaction. Hydrogenation reaction is one of the deadliest of all reactions since it involves hydrogen gas. Hydrogen gas is very light and diffuses into the air very quickly. It is highly flammable too. Not a nice combination. It not only catches fire but spreads wildly. Transfer hydrogenation on the other hand doesn’t require hydrogen gas, it just needs the donor reagent. I think the reason it is not so good to scale-up is because it would need change in existing infrastructure and that comes at a cost.
Another example of safer engineering is eco-friendly coolants. Transformers made it possible for electricity to reach long distances without huge losses. Polychlorinated biphenyls is a banned coolant fluid that was used to cool these transformers. Efforts have been made to produce greener coolants. In 2013, Cargill won the Presidential Green Chemistry Challenge Award from the U.S. Environmental Protection Agency (EPA) for developing Envirotemp™ FR3™, a eco-friendly coolant. It can be used in high voltage electrical transformers.
Meet Need, Minimize Excess: Design for unnecessary capacity or capability (e.g., “one size fits all”) solutions should be considered a design flaw.
Effluent treatment plants (ETP) often are of the ‘one size fits all’ kind. We call them Common Effluent Treatment plants (CETP). Instead, each plant can have its own ETP. Individual ETPs are more efficient than CETPs.
Design for Separation: Separation and purification operations should be designed to minimize energy consumption and materials use.
Separation and purification operations allow us to recycle materials. To make these operations as energy efficient as possible is therefore necessary. As we know that Pharmaceuticals industry produces highly pure products. Moving bed bioreactor (MBBR) systems are a type of biological treatment that may be utilized in pharmaceutical wastewater applications.
Prevention Instead of Treatment: It is better to prevent waste than to treat or clean up waste after it is formed.
Ultrasonication is another part of my Masters thesis. I basically bombarded a flask of chemicals by ultrasound. In this way, I was able to carry out the reaction without a solvent and at room temperature. This was opposed to previous attempts to carry out the same experiments that used solvents and higher temperature and pressure. As far as industrial applications of ultrasonication are concerned, a company called Industrial Sonomechanics has created industrial scale ultrasonic reactors.
Maximize Efficiency: Products, processes, and systems should be designed to maximize mass, energy, space, and time efficiency.
Microreactors, reactors with dimensions of about 5-100 ml, can run reactions that are not possible to run at large scale. These reactions are often explosive or hazardous in nature. Such a technology when scaled up can lead to material-efficient, energy-efficient as well as safe way to carry out reactions.
Viscosity/Solubility (e.g. separation of N2 and O2 can be done by absorption of N2 in a liquid as O2 leaves)
States of material (e.g. again – separation of N2 and O2 can be done by absorption of N2 in a liquid as O2 leaves)
Applications in water purification
With increase in the number of water-stressed regions such as India, the need for water purification is more than ever. Equally important are small scale and the large scale water purification systems. Small scale systems include the portable water purification systems such as SODIS that uses solar energy to disinfect disease causing biological agents or a homemade waterfilter. Disinfection is one of the many steps involved in the purification process. Large scale systems includes an array of processes such as pre-treatment, sedimentation, filtration, disinfection, desalination and many more that require bigger assemblies.
Recently, DOW Technology helped the Largest Desalination Plant in Spain operating with pressurized ultrafiltration to deliver freshwater for municipal use. Ultrafiltration is one of the advanced separation processes, which is a type of membrane filtration. Apart from water purification, such systems are used in industry was various reasons. Ultrafiltration is used for concentrating target molecules, clarification needed in wastewater treatment processes, desalination such as that used in the plant in Spain or for fractionation of peptides in dilute samples.
In a chemical industry or a chemical laboratory, separation processes are required before and after each stages. For example, before entering the system, the raw materials are purified. After reaction, the process may give out materials in different phases -gas/liquid/solid. These have to be separated so as to reach the recycle stream and the effluent stream. The effluent stream again has to undergo recovery of certain substances before it reaches the environment.
Treatment of industrial waste is growing evidently stringent as time passes by. This requires such separation processes which aid pollution prevention. In fact, the entire waste water treatment mechanism is based on physical separation of effluent entities.
“Utilization ratios — the proportion of solar radiation reaching a collector’s surface that can be converted to usable process energy — of over 60% can be obtained by integrating solar thermal equipment in industrial systems. By comparison, photovoltaic systems typically have an efficiency of around 15%. ” –che.com
Solar energy can not only be transformed into electricity, but process heat in a chemical industry.
“Nanoheaters generate steam at a remarkably high efficiency,” Halas said. “More than 80 percent of the energy they absorb from sunlight goes into production of steam. In the conventional production of steam, you would have to heat the entire container of water until it boils, with the bubbles rising to the top to release steam. With nanoheaters, less than 20 percent of the energy heats the neighboring liquid.”
A flow chart below shows what a typical chemical process industry looks like, in a broad sense. As you can see, every stage or every plant in the industry emits waste (effluent – whatever that flows outward, other than the product) in any of the forms viz. gaseous, liquid and solid. Effluent handling is a vast topic. Due to stringent norms on effluents emissions, a huge amount of study has been dedicated to waste treatment.
How does one manage effluents?
Make appropriate changes, innovations in the process. This is one of the 12 principles of Green Chemistry, to create such a process so that no waste is produced. Zero waste.
So much for Zero waste, it is not always possible. So what can one do? End of pipeline i.e. when changes and innovations are not possible in a process, treat the effluents. Separation and purification is one of most economically costing processes in the industry.
3R: Reduce, recycle and recover. (Recover: “Liability at one end becomes asset at the other.”, Wealth from waste)
It figures, not all are concern driven. Some can envision the long term (or short term, or local) effects of pollution, while others simply care about money, or both? Money is the incentive and is not about proving that chemistry and physics are working together. Innovation is making money. Money is the incentive, so we find ways to earn money while we try to protect the environment, such as carbon emission trading. Another example is how India gained most from destroying HFC-23.
How do green technologies help us?
green technology operates in harmoney harmony with nature, but may not always makes business sense,
helps keep a limit on the pollutants produced,
most importantly is site specific because what is green at one place won’t necessarily be green at another.
Food for thought – What could Ranbir Kapoor be possibly trying to say in the song ‘Sada Haq’ of the movie ‘Rockstar’ when he says these words: “O Eco friendly, Nature ke rakshak, Main bhi hoon nature”
This blog post introduces some common terminologies related to safety, and then moves on to the intricacies of it.
Hazard: A hazardis anything that may cause harm, such as chemicals, electricity, working from ladders, an open drawer, etc.
Risk: The risk is the chance, high or low, that somebody could be harmed by these and other hazards, together with an indication of how serious the harm could be.
Safety engineering: It is an engineering discipline which assures that engineered systems provide acceptable levels of safety.
Hazard Identification Study: It is the process of identifying hazards in order to plan for, avoid, or mitigate their impacts. Hazard identification is an important step in risk assessment and risk management.
Risk assessment: It is the determination of quantitative or qualitative value of risk related to a concrete situation and a recognized threat (also called hazard). A risk assessment is simply a careful examination of what, in your work, could cause harm to people, so that you can weigh up whether you have taken enough precautions or should do more to prevent harm.
Occupational safety and health (OSH): It is a cross-disciplinary area concerned with protecting the safety, health and welfare of people engaged in work or employment. The goals of occupational safety and health programs include to foster a safe and healthy work environment.
Hazard analysis: It is used as the first step in a process used to assess risk. The result of a hazard analysis is the identification of different type of hazards.
Now that you know some of the terms that are frequently encountered while approaching this topic, we can move on to the intricacies of it. Before anything, analysis is must, an assessment of a risk. How is it done?
Step 1: Identify the hazards
Step 2: Decide who might be harmed and how
Step 3: Evaluate the risks and decide on precautions
Step 4: Record your findings and implement them
Step 5: Review your assessment and update if necessary
HAZOP study is the assessment on adequacy of safety measures taken by industries vis-avis the hazards present and is primarily carried for chemical industries.
Any plant operation sometimes involve deviation from design parameters during the operation. HAZOP study is a structured methodology to identify all possible deviations of the process parameters namely temperature, pressure, composition, direction of flow etc, and all the consequences associated with each deviations. The deviation is also correlated to the safety interlocks, instrumentation and administrative procedure related to the operation.
The output of HAZOP is a list of possible deviations, their causes, consequences, safety measures and additional safety measures required to avoid consequences.
Because different countries take different approaches to ensuring occupational safety and health, areas of occupational safety and health’s needs and focus also vary between countries and regions. Read more here.
Everyone has the Right to Know, the chemicals they are working with, the environment they will be exposed to.
This topic stretches miles. One can go on reading about safety and the laws surrounding it. Last but not the least, we should not forget that we are humans, imperfect, we make mistakes. So, considering this, one also has to study something known as Behavior-based safety. Read more here.
Before looking at the strategies of making plants safer, lets us first see how it is traditionally done.
LOPA (Layers of protection analysis):
The various measures for prevention and mitigation of major accidents may be thought of as lines of defence’ (LODs) or ‘layers of protection’ (LOPs). These lines or layers serve to either prevent an initiating event (such as loss of cooling or overcharging of a material to a reactor, for example) from developing into an incident (typically a release of a dangerous substance), or to mitigate the consequences of an incident once it occurs. This is illustrated in figure below.
Coming to the strategies, they will be presented in order of reliability:
Inherent: Eliminating the hazard by using materials and process conditions which are non-hazardous. It is the most reliable way. How about creating an atmospheric pressure reaction using non-volatile solvents. This way there is no potential for over pressure. Instead of using a corrosive substance like AlCl3 as a regent in huge quantities, we can use catalytic quantities of say, scandium triflate. A scientist, Shu Kobayashi, has researched a lot on Lewis acid catalysts like metal triflates, which are non-corrosive in nature, unlike the usual lewis acid catalysts.
Passive: Minimizing the hazard by process equipment features which reduce either the probability or consequence of the hazard without active functioning. Designing a vessel for 4 atm when the operating condition is 1 atm or having equipment before or after the vessel to reduce the excess pressure. A reaction capable of generating 150 psig pressure in case of a runaway, in a vessel designed for 250, this way the reactor can contain the accident unless it is damaged.
Active: Using controls, safety interlocks and emergency shutdown systems to detect and correct process deviations (engineering controls). A reaction capable of generating 150 psig in case of a runaway in a 15 psig reactor with a 5 psig interlock that stops feeds and a rupture disk to reduce pressure, directing contents to effluent treatment. What could happen?
Procedural: Using operating procedures, administrative checks, emergency response, and other management approaches to prevent incidents, or to minimize the consequences (administrative controls). Consider the same 150 psig reaction, same reactor, without the interlock. The operator is instructed to monitor the pressure and shuts down feed. Mind you, there can be a human error to make it worse, hence it is the least preferred method.
Another way of looking at inherently safer process strategies is this:
Minimize: Use of smaller quantities of hazardous substances. (Intensification/Continuous processes)
Substitute: Replace a material with a less hazardous substance.
Moderate: Use less hazardous conditions, a less hazardous form of a material, or facilities which minimize the impact of a release of hazardous material or energy. (Attenuation or limitation)
Simplify: Design facilities which eliminate unnecessary complexity and make operating errors less likely, and which are forgiving of errors which are made. (Error tolerance)
Do you remember? It is the same strategy we looked up to design safer chemicals.