Water and conventional biodiesel production don’t mix. It reacts with the feedstock and catalyst to make unwanted soaps through saponification. But the two-stage biodiesel conversion process known as hydrolysis/esterification, or hydroesterification, “laughs at water content,” says Peter Brown, cofounder of Nevada-based biodiesel equipment provider International Procurement Tools LLC.

The idea behind the process, which isn’t new but still rather obscure, is converting 100 percent of any low-grade feedstock to free fatty acids (FFA) first, prior to biodiesel conversion, with a hydrolysis step involving heat and pressure (subcritical water) at 60-65 kgf/cm2, 270 degrees Celsius in a high-pressure tower, inducing a chemical reaction between the water and feedstock without an added catalyst. The fatty material is preheated and fed on the bottom of the tower while demineralized water is preheated and fed on the top of the tower. For this, independent piston pumps with a flow rate of 1:1 (fatty material: water; w:w) are used. The denser water flows to the bottom of the tower and the fatty material flows of the top, creating a countercurrent flow where the hydrolysis reaction happens. The FFAs are discharged from the top of the tower and dehumidified in an expansion tank by adiabatic vaporization, Brown says. The glycerin-laden "sweet water" is released from the bottom to a flash tank and sent to the evaporator.

The glycerin, according to Brown, is 99.8 percent pure since there is no methanol or catalyst present in the hydrolysis step.

The heat required for the system is generated by a closed system with circulation of dowtherm oil from a vaporizer, Brown says. The water and fatty acids are heated with a set of highly efficient heat exchangers and the heat output currents are recovered in recovery exchangers. 

The second step is esterification of the FFAs to biodiesel with methanol and no acid catalyst. 

The FFAs from hydrolysis are preheated and deaerated to remove air and moisture, then purified by vacuum distillation. In this process, the unsaponifiable matter and some corants are removed. The distillator is operated at medium temperature 220 degrees C and under high vacuum.

The distilled FFAs are condensed and transferred to storage. The residue, consisting of nonvolatile contaminants, are withdrawn at the bottom of the distillator and sent to the waste tank.

The esterification is performed in a stainless column at temperature of 210-220 degrees C and pressures of 20 kgf/cm². The distilled FFAs and methanol are preheated and pumped into the column in a countercurrent flow. The biodiesel is discharged from the bottom of the column and a mixture of water and methanol are discharged from the top, and sent to recovery.

The H/E process was pioneered by Ubaldino Soares, owner of Brazil-based company USDA. Soares holds a patent on the process in Brazil.

“Most existing solutions for producing biodiesel in Brazil rely on transesterification technology,” says Soares. “The few esterification solutions require immense amounts of energy, ion acid beds that deteriorate under the production process and need constant ion replenishment. I discovered that maintaining a delicate balance in the pressure/temperature equation during production dramatically alters the energy consumption and allows for almost no additional inputs. One of my units has been producing pure biodiesel and glycerin for five years now.”

“The process is hardly new, since it has been in operation in three locations in Brazil for at least three years,” Brown says. “It has just not been commercially available until today and we intend to bring it to market worldwide.”

IPT just recently signed an exclusive technology license agreement with Soares to become the global distributor of hydrolysis/esterification biodiesel production units. IPT is in talks with a number of fabricators in third-world countries to build the units, and it is working with an engineering firm to do the P&IDs and other detailed design engineering work.

“This could be the Holy Grail of biodiesel production since it allows biodiesel producers access to a vast source of feedstock that are not presently considered suitable for production of EN or ASTM biodiesel,” Brown says.

Two key elements of selecting a traditional biodiesel process are the feedstock’s FFA content and the presence of water in that feedstock. The higher the FFA number, the more complex the remediation process; and as vegetable oils and animal fats sit in transit, the FFA levels increase. Water content of the oil and as a process requirement also influences the quality of the fuel and the feedstock selection. Brown says the H/E process converts all oils and fats regardless of their FFA levels and water content. 

Brown says the new technology is available for quotes now and can be designed to process from 3 to 60 MMgy of either EN or ASTM biodiesel. He says pricing will remain competitive with his other IPT processing units.

“We expect that at the very least, using this technology will allow biodiesel producers to become competitive,” Brown says.