Monitoring Environmentally  Responsible Cleaning

Introduction

Remaining complaint with regulatory agencies and reducing Greenhouse Gas Emissions is now part of nearly all rubber product manufacturers. Finding efficient, economical, environmentally responsible ways to clean without cleaning products contributing to the global warming concerns and having cleaning supplies ending up in landfills is a reality. 

A previous article from the December 2019 issue of RubberWorld (Volume 261, Number 3) discussed how the dry ice cleaning process works and supported its claims of being non-abrasive, improving productivity and quality, and lowering costs. Our focus here will be on the environmentally friendly nature of cleaning with dry ice and how both the equipment and cleaning process can be remotely monitored. 

Regulatory agencies such as the Environmental Protection Agency (EPA) and California Air Resource Board (CARB) have commented on dry ice cleaning. Both agencies, the California Air Resource Board (CARG) and the Environmental Protection Agency (EPS) note that cleaning with dry ice does not contribute to your greenhouse gas emissions score. The foundation for that is the fact that dry ice is made from recycled C02. Taking a by-product (waste C02) from numerous industrial processes and giving it a second, useful life.

Cleaning with dry ice often replaces other traditional cleaning methods, usually involving solvents, which give off a variety of man-made GHG emissions. Carbon dioxide (C02) is found naturally in our environment, and using dry ice eliminates the emissions of several harmful man-made gases, see Figure 1.

Figure 1: Traditional Solvent Based Cleaning

 Common cleaning solvents often contain the following man-made gases:

• fluorinated (F) gasses
• Hydrofluorocarbons (HFC’s)
• Chlorofluorocarbons (CFC’s)
• Perfluorocarbons (PFC’s)
• Sulfur Hexafluoride (SF6)
• Tetrafluoromethane (CF4)

Such man-made gases in cleaning solvents remain in the environment longer than C02 and often include the use of rags and brushes, which can end up in landfills. When used, dry ice simply sublimates and returns to its natural state of gas. 

Below is a graph of the Global Greenhouse Gas Emissions by Gas currently in our atmosphere; see Figure 2.

Figure 2: Global Greenhouse Gas Emissions by Gas

For reference, methane (CH4) is 80 times more potent than C02 in causing global warming and is now 1,875ppm, up 2.5X from 1850’s. Nitrous Oxide (N20) is 280 times more potent than C02 in causing global warming. 

Definitions

What is dry ice anyway? Dry ice is the generic name for the solid phase of carbon dioxide (CO₂). It receives its name “dry” because when it heats up, it sublimates and returns to a gas without going through a liquid phase, i.e., evaporation. 

Carbon dioxide is one carbon atom plus two oxygen. It is the gas we and all animals, even humans, breathe out, about 2 lbs. of it every day. It is the gas that gives fizz to our fizzy drinks and is very soluble in water, as we can see from watching a soda stream machine. In fact, all dry ice is food-grade, meets the provisions of FDA 21 CRF 110, and is made to Compressed Gas Association (CGA) standards.

Yes, dry ice is carbon dioxide, and it is the gas that is widely in the news with regard to global warming. But understand, don’t be misled. It is the gas that matters, not the carbon element, as commonly reported. Contrary to public opinion, C02 isn’t the enemy. It is a gas naturally found in our environment, and without it, our planet would be very, very cold. It is part of our planet’s natural greenhouse effect that helps trap heat on our planet. With no C02 in our atmosphere, our planet is -20 degrees C (-4 degrees F).

Here are some other interesting facts about C02:

• It is essential for the survival of most living organisms.
• It is essential in cycling our ecosystem through respiration.
• It is essential for natural photosynthesis.
• It is essential for plants to manufacture sugar, the basis for the food supply.
• Without C02 it is impossible to have any kind of food on the surface of this earth.
• Provides the carbon that is the building block of all life. Plants consume it, and humans and animals consume plants.
• C02 might be the end point in the fuel cycle, but it is the beginning of the life cycle.

Interesting facts about C02 in the form of dry ice.

Some facts about dry ice in 2021…

• Been used to ship 3 billion lifesaving vaccines to more than 165 countries all around the world.
• Billions of gallons of water previously used for industrial cleaning were rerouted to drinking water.
• Millions of pounds of food were preserved during shipment using dry ice.
• Factory workers are safer, fewer being exposed to hazardous, ozone depleting cleaning solvents.
• Industrial waste from cleaning supplies heading to landfills is being reduced.
• People are more productive and make better quality products.
• The world is safer, cleaner, and healthier because of dry ice.

If cleaning with dry ice isn’t the issue, where does the excess C02 in our environment come from?  Animal respiration is believed to add 28 million tons of CO₂ per day into the atmosphere. By contrast, the entire U.S. CO2 industry can supply only 25,000 tons of dry ice per day, and 95% of this amount is from by-product sources or less than 0.04% of the other sources combined.

Doing the math on the bigger picture, currently, there are around 42 billion tons/year of C02 emissions. That represents 0.04% of our atmosphere; see Figure 4.

Figure 4: The Gases That Comprise Earth’s Atmosphere

 Commercial C02 emissions, those industrial processes that provide the feedstock C02 to manufacture dry ice, are around 22 million tons/year or around 0.05% of the total emissions. That means the commercial c02 market represents 0.0000021% of the C02 in our atmosphere. That noted, the commercial C02 market (the source for dry ice) is not the big problem with overall global C02 emission issues. The emissions from dry ice blasting are negligible.

 So where does the commercial  C02 come from that is used to manufacture dry ice? Commercial C02 is captured as a by-product from man industrial processes, see figure 5.

• Ammonia production is the main source (25% in North America, 50% in the EU)
• Hydrocarbon process (gas refining) (25% globally)
• Bioethanol (20% globally)
• Natural gas refining (20% globally)
• Biological (fermentation, anaerobic digestion)
• Other (natural wells, etc.  (5% globally)

      These by-product C02 gases become the feedstock for making dry ice. Transforming wasted industrial C02 into a value-added product with commercially useful applications, i.e. cleaning. The C02 gases are separated from other flue gases and scrubbed to purify, and then phased under pressure through a series of compression and cooling cycles to a liquid.

Applications

So why is dry ice good for cleaning?

First, as noted from its name, dry ice is dry. Keeping many processes dry during cleaning is a good generally a good thing. It does not promote rust or corrosion.

Carbon dioxide is a linear molecule, not a bent molecule like H20 (water), see Figures below.

Figure 6: Linear Carbon Dioxide Molecule

Figure 7: Bent Water Molecule

C02 is non-polar in that it does not have a positive or negative charge like H20. Therefore, it does not react with substrates like water can during cleaning, which can cause problems. 

Beside the fact that dry ice is “dry”, there are many other adjectives and descriptors for C02:

• It is a stable molecule
• No reactivity
• Inert
• Non-flammable
• Colorless
• Tasteless
• Odorless
• Non-polar
• Not inherently harmful
• Primary sources of life
• Primary source of carbon on earth
• Required for photosynthesis to produce oxygen

All these traits lend a positive attribute toward cleaning tooling. These are just some of the reasons C02 is a great molecule for cleaning our stuff. 

It is easy to surmise that this program was written around the large industrial C02 emitters, not dry ice blasters. To reach reporting limits, you will need to emit 25,000 metric tons or more of carbon dioxide equivalent per year in the United States. They note that ‘most small businesses fall below the 25,000 metric ton threshold and are not required to report GHG emissions to EPA. In fact, the words “dry ice “do not even appear in the standard. But could I hit that number if I use dry ice for cleaning? To achieve that limit, you need to blast through a quantity of 274 totes, each containing 550 pounds of dry ice per day!

As noted earlier, the gas C02 feedstock to manufacture dry ice comes from a variety of sources. Regardless of the source, the manufacture of dry ice comes from a Carbon Capture and Utilization process (CCU), as illustrated in Figure 9.

Figure 9: Carbon Capture & Utilization Process for Dry Ice Manufacturing

Because of the attributes noted in the December 2019 Rubber World article and the environmentally friendly nature of dry ice cleaning noted in this article, many in rubber processing/molding have chosen to clean with dry ice.

The most common application is the cleaning of tooling, as shown in Figure 10 below:

Figure 10: Dry Ice Rubber Mold Cleaning

Let us unwrap another reason why rubber molders clean tooling with dry ice. It is faster. Since cars incorporate a variety of rubber components, consider racing cars as an example. You are running a competitive race against all your competitors. You look great out on the track - your processes are competitive -but how are your pit stops, your downtimes for cleaning? At some point, all processes must be interrupted, and time set aside for cleaning. 

There is a great YouTube video which shows a pit stop from the 1950 Indianapolis 500. They were excited about a 67 second pit stop. Today, Formula 1 pit stops are often achieved in under 2 seconds. So how are your downtimes, your Availability 0EE score with traditional cleaning methods? Are you still cleaning molds today with the same methodology you did when you began your business? How many races are won and lost in the pits? Henry Ford once said, “If you always do what you always did, you’ll always get what you always got.” Change is often the price of success.

 Traditional cleaning methods for hot tooling often include a multiple step process that consumes too much time. Letting the mold cool, sometimes removing the tool, cleaning, reinstalling, reheating, and starting again, see Figure 11. Dry ice allows rubber molders the ability to clean molds in -situ and at operating temperatures. You may recall the in-depth studies examined in the December 2019 issue of Rubber World about the speed and non-abrasive nature, including no thermal stress, to hot tooling during dry ice cleaning.

Figure 11: Total Potential Downtime with Multi-Step Cleaning

Monitoring Machine & Process

  Today, the entire cleaning process can be remotely monitored. Using the Industrial Internet of Things (IIOT) technology, Cold Jet CONNECT brings Industry 4.0 practices into our maintenance functions. We are now able to remotely monitor both the machine and cleaning process, bringing intelligence to maintenance management. Manufacturing has become increasingly more organized and automated over the years, and this new age of digitization has become the new standard, and only the innovative will survive.

     Industry 4.0 was all about connecting the factory floor with management. And we have done a really good job on the production floor. But what about maintenance functions? What about our tool cleaning processes? ToolingDocs reports that 60-70% of all mold maintenance is done by mold cleaning. Think about that, 60-70% of the time we touch our tooling, it is for cleaning. Let’s utilize ways to better manage the mold cleaning process.

      Cold Jet CONNECT goes beyond just data – individual observations and information – the useful collection of data. It brings intelligence that combines information for a narrative that enables better decision-making that will accelerate your return on investment through increased machine efficiency and uptime, see Figure 12.

Figure 12: Remote Monitoring of Machine & Process with Cold Jet CONNECT

Many rubber processors will testify that cleaning with dry ice is a proven, effective, quick, non-abrasive, and environmentally friendly method to clean molds. Cleaning with dry ice is not part of the global warming discussion. So, let us celebrate mold cleaning instead of postponing it. Let us manage the mold cleaning process instead of letting it manage us. If you want to lower your carbon footprint, bring C02 (dry ice) into your production processes, and you will discover what many rubber processors have discovered:

1. Extended asset life with non-abrasive cleaning.
2. Improve quality with a better clean and no residues left behind.
3. Improve productivity by cleaning in place at operating temperatures.
4. Reduce costs by cleaning faster and minimizing downtime.
5. Improve environmental quality by eliminating cleaning solvents.

 Figures and tables are provided for general information and are not for the purpose of warranty or specification. 

Read the full article with a case study here!