Woods to wheels - Chemrec's BioDME demonstration plant at the Smurfit Kappa mill

By Ingvar Landälv, vice president of Technology and Patrik Löwnertz, vice president of marketing and sales for Chemrec AB, Stockholm, Sweden

BRUSSELS, Feb. 28, 2010 (RISI) - With the turn of a shovel, Sweden's King Carl XVI Gustaf broke ground September 18, 2009, at the Smurfit Kappa paper mill in Piteå, Sweden, for the world's first black liquor biorefinery for the production of a renewable ultra low-carbon automotive fuel called BioDME.

At the core of this biorefinery is gasification technology from Chemrec and its US subsidiary, Chemrec USA. The project will demonstrate the production of an advanced diesel fuel, dimethyl ether (DME), from forest biomass over the black liquor route and also the use of this fuel in heavy vehicles in commercial service. The pulp mill-integrated BioDME biofuel demonstration project is scheduled to produce biofuels by mid-2010.

Figure 1 - The DME plant in Piteå: it is scheduled to be producing biofuels in 3Q 2010

For mill owners, operators and investors - as well as for the states in which they operate - the potential to be transformed into high-margin biofuels producers is gaining interest nationwide. Mills as biorefineries not only contribute to America's growing trend toward energy independence, but maintain and create mill and forestry jobs, a boost to not only mills themselves but the communities in which they operate and from which they pull their employees.

With a high cetane number and with no particle formation during combustion, DME provides the opportunity to very cost efficiently meet stringent exhaust emission targets. When DME is produced from residual forestry biomass over the black liquor route, it also offers a very high reduction of fossil carbon dioxide emissions, around 95%, compared with conventional diesel fuel and it can be produced with very high conversion efficiency at relatively moderate capital cost.

This article takes an in-depth look at the evolution of Chemrec's BioDME demonstration plant at the Smurfit Kappa mill. Phase one, Chemrec's DP-1 demonstration plant, produces syngas from renewable forestry biomass; it recently passed 11,000 hours of accumulated run time. In September 2009, Chemrec broke ground on phase two, known as the BioDME Project, which will produce biofuels BioDME and methanol as early as third quarter 2010.

The BioDME Project plant will be built by Chemrec with other aspects of the project to be built by consortium members: catalyst company Haldor Topsøe, truck manufacturer Volvo AB, Swedish oil company Preem, global oil giant Total, vehicle electronics provider Delphi and the technical firm Energy Technical Centre. The $40 million project - including the plant as well as vehicle, delivery and filling station development - is being funded by the Swedish Energy Agency and the EU's Seventh Framework Programme.

Finally, in very late September 2009, the Swedish energy R&D board granted $70 million to Chemrec to build the world's first industrial-scale BioDME plant. To be built at the Domsjö Fabriker pulp mill in Örnsködsvik, Sweden, this biorefinery will produce 40 million US gallons/yr of BioDME by 2012.

Smurfit Kappa bioDME project status

In June 2008, financing was secured for the BioDME project. After extended pre-engineering, the project was given final go-ahead in March, 2009. Throughout the spring and summer the BioDME plant detail design was completed, as was procurement of long-delivery equipment. Site activities started in September and fuel production is scheduled to start in mid-2010. Vehicle development and production was also well along, with the first trucks for fleet trials built during the summer of 2009.

BioDME production plant: Main technology providers for the DME production plant are Chemrec and Haldor Topsøe. The process steps of the pilot plant are illustrated in Fig. 2.

Figure 2 - Schematic of the Piteå DME production plant

The gasification process step combines two objectives - production of green liquor from black liquor and upgrade of the organic part of the black liquor to synthesis gas. Also primary gas cleaning and cooling takes place here. The existing Chemrec DP-1 gasifier plant is used for this service. It had in June 2009 accumulated 10,000 operating hours consistently producing green liquor and synthesis gas of high quality. Carbon conversion and sulfate reduction is near 100%. Syngas tar and methane content is very low, eliminating the common need in biomass gasification for secondary tar and methane reforming.

The capacity of the plant is 20 tonnes/day (44 000 lb) of black liquor solids and it is operated at 3.0 MPa (g)/450 psi(g) pressure. The operating principle of the gasifier is partial oxidation with oxygen in an entrained flow reactor followed by quenching in two steps to saturation and subsequently gas cooling in a counter-current condenser.

The composition of the synthesis gas that leaves the gasifier has a too low H₂/CO ratio for an efficient methanol synthesis and part of the CO is therefore reacted with steam in the Water Gas Shift (WGS) unit according to:

(A) CO + H₂O - CO₂ + H₂

The water-gas-shift reaction is taking place at very low steam/dry-gas ratios. This favors the economics by keeping the steam consumption low but also means that there is a risk for methanation; therefore, a very selective catalyst, Topsøe SSK, is used.

The reaction rate in the downstream methanol synthesis is much increased by keeping the CO₂ level fairly low, and sulfur components are poisons for the methanol catalyst. The partially shifted synthesis gas is therefore sent to an Acid Gas Removal (AGR) unit, in which not only CO₂ but also the majority of sulfur components is efficiently separated out. The acid gas removal will be done by absorption in MDEA (N-Methyl-DiEthanolAmine). The operation of the plant will provide added insight into how the sulfur slip varies with operating conditions and CO₂ rejection efficiency. This knowledge enables a more compact design of the downstream sulfur guard and gives better insight into the conditions at which an MDEA wash can be used for the AGR service.

The necessary sulfur polishing - regardless of the AGR technology used - must take place by solid absorption. This process is more efficient at increased pressure and temperature compared to the conditions that prevail at the AGR outlet. The sulfur guard is therefore installed downstream of the methanol synthesis gas compressor.

The methanol synthesis takes place in two steps. In the first reactor the bulk of the reaction takes place at conditions favoring a high reaction rate while the second reactor with its unique design ensures a sufficiently high conversion to eliminate the need for a recycle stream around the methanol synthesis. In both reactors the main reaction is

(B) CO + 2 H₂ - CH₃OH

The raw methanol is sent to the DME synthesis via an evaporator that is designed so that heavy by-products from the methanol synthesis (particularly wax) are simultaneously rejected.

In the DME reactor, DME is formed from methanol according to:

(C) 2 CH₃OH - CH₃OCH₃ + H₂O

Figure 3 - The DP-1 black liquor gasifier

Any ethanol formed as by-product in the methanol synthesis will react in a similar way and form primarily MEE (methyl ethyl ether). MEE is an excellent diesel fuel, so the formation of this product is not considered a disadvantage. On the other hand, propanol and higher alcohols preferentially form olefins. The boiling point of these components is typically similar to DME, and they have less optimal combustion characteristics in a diesel engine. The formation of these must therefore be taken into account in the DME purification process design. This comprises three columns: an olefin stripper, a DME/Methanol splitter and a wastewater column. In the latter, water that is co-produced in the DME reactor is separated from the unconverted methanol that is recycled to the DME reactor to obtain essentially 100% methanol conversion.

The process described has one distinct feature, which makes it extremely attractive compared to current state-of-the-art DME processes, and that is its single-pass nature. The only recycle stream in the process described above is that comprising unconverted methanol to the DME reactor. This is a liquid recycle requiring no loop compressor and further the flow rate is very small as more than 80% of the methanol is converted in the DME reactor. The advantages of the once-through process is reduced capital and operating cost as well as process that is easier to operate and control.

Surprisingly, these advantages come without an efficiency penalty, as the overall CO and H₂ conversion is higher than what is normally attained in methanol and DME processes based on a conventional methanol loop.

First BioDME truck for fleet trials with its modified MD 13 440 hp engine

Another advantage of this process over conventional DME processes is the flexible distillation system. The separation process in the DME pilot contains more separation columns than the commercially available DME separation schemes. This feature comes at a cost but also gives DME with a higher purity and allows the co-production of methanol if desired.

The gas treatment step of the plant rejects carbon dioxide at high concentration. The process is therefore also very suitable to combine with carbon capture and sequestration (CCS). With renewable feedstock the produced biofuel will then have a carbon footprint less than zero.

The BioDME project will not only be a technical demonstration but will also showcase the opportunity for the pulp and paper industry to play a major role in the production of high-value, high-performance biofuels from low quality forest and agricultural residues. We look forward to report on the continued progress.

Ingvar Landälv is vice president of Technology and Patrik Löwnertz is vice president of marketing and sales for Chemrec AB, Stockholm, Sweden. For more information, visit: www.chemrec.se; , or contact Richard J. LeBlanc at rick.leblanc@chemrec.se or 1-847-772-0553.

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