Environmental Solutions in Solvent Recycling

Authors Name: Mike Robbins

Distillation is the simple process of heating a mixture of ingredients until a solvent or other selected material evaporates-then cooling and condensing that vapor into a pure liquid. Alcohol has been produced this way since time immemorial and today the process is being used by large and small companies to reduce their waste streams and recover reusable products, thus saving significant cost.

The ability to easily recycle solvents “in-house” has developed over the past 20 odd years with the advent of “batch” solvent recyclers (stills). Solvent recycling equipment ranging in size from 2 gallons per batch up to equipment handling one hundred gallons per batch have made it cost effective for companies to consider replacing expensive service companies. In recent times even larger solvent recyclers have been developed which can work either stand alone or built into a process system to reduce or eliminate the needs for full time personnel to over see the operation.

These solvent recyclers save money in two ways: by recycling used solvents for reuse and eliminating most (and sometimes all) of the expense of disposing of the hazardous waste. Although even the smallest solvent recyclers cost several thousand dollars, they can easily pay for themselves in a year or two. In the case of large scale continuous operation solvent recyclers, it may be surprising to learn that the payback can easily be justified in less than one year.

In fact in certain process industries the equipment vendors recommend the purchase of a solvent recyclers to defray the cost of the exceedingly expensive solvents required in their equipment.

When one examines the amount of waste generated in industry, and the costs associated with its handling, it becomes evident that waste has a major economic impact on the performance of most businesses. If you consider all the waste as product, then what value would that waste have to the average business.

Clearly, the best solution to hazardous waste is to NOT make as much of it! Given that a business is a successful entity, that success will create more hazardous waste problems. Just as the quality of your work and throughput affect your business’s competitive edge, so too can hazardous waste and its disposition. Thus, in-house solvent recycling must be considered as a relevant solution to the hazardous waste problem.

It also must be said that solvent recyclers are good for the environment: They make it possible to use the same material over and over radically reducing disposal and saving money by eliminating or reducing purchase of new material.

What are the considerations? Do you take on liability with EPA if you recycle? The answer is: yes, but it is the same liability you have with a service company. When a company buys potentially hazardous materials, they acquire cradle to grave liability. This is also acquired when using a service company. That being the case, there is no reason not to look at in-house recycling as an alternative to service company costs.

There are two types of solvent recyclers: continuous and batch.

Continuous solvent recyclers use in-line or auto-fill technology-that is, dirty solvent flows into one end and clean solvent comes out the other. This solution, available in varying volume capabilities, is used in industrial applications by large generators of solvent. By contrast, batch solvent recyclers distill one load of solvent at a time over a period of several hours.

The principal components in any solvent recycler are a tank in which the waste is deposited, a heating system for turning the liquid part of the waste into vapor and a condenser to cool the vapor back into a liquid.

The size of the tank determines the size of the solvent recycler. Methods of heating include steam, direct heat (using an electric heating element or heat plate) and indirect heat (where an oil bath surrounding the tank is heated by direct electric heat). Indirect heat is usually the preferred approach because the heating is more uniform.

The condenser is most often a series of looped copper or stainless steel coils (resembling a car radiator) that are cooled by a built-in fan or surrounded by water or coolant to chill the vapor back into a liquid. Cooling by air is less expensive than cooling by water or coolant and is adequate for small, batch type solvent recyclers. Water cooled condensers may be necessary for applications where the condensing temperature is particularly low or the environment of the facility is unusually hot. The water cooled condenser will then be more efficient.

Solvent recyclers are fairly unique among tools in industry in that they do almost all the work on their own. About the only thing you need to do is fill the tank (either manually for small machines or automatically for large), turn on the machine and remove the solid material that is left after the process. In the case of large automated machines, even the waste is removed without manual intervention.

Any organization using solvents on a continual basis is a potential candidate for a solvent recyclers. In addition, any organization using a waste hauling service would be well advised to do a payback analysis on the purchase of a solvent recyclers.

Here is the way to determine the degree to which you will benefit from owning a solvent recyclers:

First, figure what you are paying per year to have your dirty solvent or waste hauled off (generally from $100 to $400 per drum, depending upon the content and where you reside). Add this number to the cost of purchasing replacement solvent for about 80% of the volume of the sludge-or 95% of the volume of the solvent waste you are recycling with a service company. The exact percentages will vary depending on how much of the material is solid waste). Then, weigh this figure against the price of a solvent recycler and determine how long it will take for your savings to pay for it.

As an example, let’s say you generate one drum of waste every month; let’s say that it costs $300 to have the drum hauled away and that you pay $800 once a month for two new drums of solvent. Let’s estimate that you only have 50% of the solvent to recover after use before recycling.

The following calculation indicates your potential yearly savings: Add $3,600 (the cost of having twelve drums of waste solvent hauled off) to $3,840 (80% of $4,800, which represents the cost of replacing the half of the solvent that remains after use). That works out to a savings of $7,440 in one year, which comes close to the cost of a small recyclers. Multiply this by the large volumes generated by industry in manufacturing, painting, printing, etc. The potential for savings is enormous.

If a solvent recyclers is of interest to your organization, the next step in the process is finding one that suits your needs.

Here are some questions to consider:

1. Is the capacity of the solvent recyclers adequate to handle the volume produced?
2. Is the tank heated by steam, hot oil or by a direct electric element? (Hot surround oil is widely regarded as the best option).
3. Is the solvent vapor cooled and condensed by coolant, water or fan? (A fan is generally adequate for small units and is considerably cheaper. For large units the conditions must be considered to determine which solution is sufficient.)
4. Is the supplier capable of supporting maintenance issues if they occur? Are parts readily available?
5. Check references for reliability of the equipment in general and in your industry in specific. What is the vendor’s track record?

Once you determine the features of the equipment that will do the job for your organization, go out and solicit quotations from several vendors as with any capital purchase. At this point it will take some intuitive judgment to determine which vendor can provide the “right” solution. More times than not, price should not be the determining factor in the acquisition. Do the homework and you will make the correct choice. Remember, as with all capital purchases, once you purchase a solution you will have to live with it for a long time.

On the good side, the organization who chooses to recycle gains several benefits. The reduction of the waste stream is obvious as is the cost savings. The “green” image that accrues to the company is valuable to its position as a good neighbor in the community. It is hard to put a value on this aspect, yet its’ benefit is great.

With society’s increasing concern for protecting the environment, it only makes sense (both for the sake of the environment and for the cost savings) to recycle your used solvents. Regardless of the size of the equipment needed, the decision to recycle in-house almost always shows a positive return on investment. With ever more difficult conditions to earn a profit, more and more organizations are turning to solvent recyclers to reduce cost and save money.