Dry Ice Blasting Solves Ethanol Plant Maintenance Headache

Faster cleaning with fewer workers is possible when dry ice is used instead of water
By Kellie Grob | May 13, 2011

Prior to the introduction of dry ice blasting for cleaning, many in the ethanol industry faced significant challenges with maintenance. Distillers dried grains (DDGS) and corn dust coats the walls of buildings, tunnels and grain pits, working its way throughout the plant.

The dry ice method of cleaning has had excellent results, particularly in the energy centers at ethanol plants, which include thermal oxidizers, stack economizers, coils and induced draft (ID) fans. Hardened corn dust gathers on these pieces of equipment and greatly reduces thermal efficiency and their ability to generate steam.

According to guidance from the U.S. EPA, ethanol producers cannot have more than one-sixteenth of an inch of dust on building or equipment surfaces. For many ethanol producers, the commonly available method for cleaning their plants and removing dust is water blasting. When it comes time for a plant’s semiannual cleaning, a maintenance crew brings in tanker trucks of water—enough to fill a pond outside the facility three feet deep when the project is done. The cleaning process typically takes 36 to 48 hours and requires 15 to18 workers to clean the equipment and handle the secondary waste, which consists of water, dirt, grease and dust.

The Problem
Cleaning with water can create problems, explained Shawn Easterly, an ethanol energy center expert. He coordinates maintenance for four facilities in the Midwest, and previously managed 16 ethanol plants for another ethanol producer. “The biggest challenge when it comes to cleaning with water is the chance of damaging the ceramic block refractory that is used to insulate the interiors of several of the pieces of equipment. If this refractory becomes wet, the damaged blocks have to be replaced—an added expense that many plants simply cannot afford. In addition, there are also certain areas of the facility and pieces of equipment and electronics that simply cannot get wet.” Rather than clean the economizers with water, Easterly commented that some in the industry simply avoided cleaning the equipment, which ultimately impacts production. 

“Even in the plants that I began overseeing,” Easterly added, “they had avoided cleaning the economizers, either because they feared damaging the refractory or simply because they didn’t understand the impact that the blocked economizer tubes had on their bottom line. Once I started to calculate the lost efficiency due to the clogged stacks, however, we realized that we needed to find an alternative to water.”
“Many of our customers have decided that they simply cannot afford to use water in their plants,” said Brad Potts, owner of New Age Cryo, a service offered by Stoc Products Inc. “Water does not mix with the grease on the machines, and equipment with electronics and computer chips have to be covered or avoided. Despite efforts to remove the water, it can be weeks before it is completely gone, and if not removed, the plant could develop a mold problem.”

A Solution

Dry ice blast cleaning provides all the benefits of high pressure water without the negative impacts. Dry ice blasting uses reclaimed CO2 in the form of dry ice pellets to remove the layers of DDGS and dust from various surfaces within an ethanol plant. Blasted by controlled, pressurized air, the dry ice pellets sublimate upon contact with equipment without damaging the surface being cleaned and without producing any secondary waste.

Using Cold Jet Aero series dry ice blast cleaning systems, New Age Cryo can clean the economizer and boiler tubes, ID fans, grain tunnels, DDGS tunnels and pits, gas stations, lime slurry stations, wet cake areas and offload buildings. In addition, since dry ice blasting is a dry cleaning process, New Age Cryo can also clean electronic components without worrying about damaging the equipment.

“The process works extremely well in ethanol plants,” stated Easterly. “We are able to clean these areas in the plants with fewer people and without the mess left behind by high-pressure water blasting.  It is safe to say that dry ice blasting will likely become the standard cleaning practice in these areas of the ethanol plants.”

The Benefits
As a result of being able to more effectively clean the equipment and areas of the plant, ethanol producers are finding significant costs and energy savings by adopting dry ice blasting. According to Easterly, it was not uncommon for his plants’ energy centers to see a 20 to 30 degree drop in stack temperatures after each cleaning. This results in increased production, significant savings in natural gas and fewer emissions. “By cleaning our stack economizers every six months, we saved $100,000 per plant in natural gas savings alone,” Easterly said. “With four plants, the annual savings totaled roughly $400,000 for the company. The economizer coils preheat the water for the ethanol production process, but when the coils are covered by the refractory, they are less efficient at heating the water and producing steam, so we have to use more natural gas. Dry ice blasting has allowed us to reduce the amount of gas that we use, while also helping us to run at higher rates.”

Potts emphasized that these savings and benefits are not unique to Easterly’s plants. “A reliable, durable cleaning system that cleans faster, with zero secondary waste and less mess is clearly something that can help the industry. Many ethanol plants across the country are identical in design and struggle with the same cleaning challenges. That said, many ethanol plants can also realize similar savings and benefits as described above by implementing dry ice blast cleaning into their maintenance process.”

Author: Kellie A. Grob
Senior Vice President, Cold Jet, LLC
(800) 337-9423