Evaluation of a Value Prior to Pulping-thermomechanical pulp business concept: Part 2

Value Prior to Pulping (VPP) is a novel biorefining concept for pulp mills that includes hydrolysis extraction of hemicellulose wood sugars and acetic acid from pulpwood prior to pulping. The concept involves conversion of wood sugars via fermentation to fuel ethanol or other chemicals and the use of remaining solid wood material in the pulping process. This paper provides an overview of the methods and results from analysis of the concept as a hypothetical business investment at a pulp and paper mill equipped for making thermomechanical pulp (TMP). Application: Traditional pulp and paper manufacturing may benefit from process synergies by integrating new biorefining concepts. 1. Block diagram of the base-case thermomechanical pulp (TMP) and paper process. BIOREFINERY – ECONOMICS 32 TAPPI JOURNAL | MAY 2011 mers is subsequently hydrolyzed, neutralized, and fermented to ethanol. Acetic acid is also produced as a byproduct of the extraction process. As shown in Fig. 2, the VPP–TMP process model also incorporates the TMP process shown in Fig. 1; however, with the introduction of VPP, operating parameters of the TMP may require adjustment. For example, VPP chip pretreatment results in reduced energy requirements in TMP refining, with a corresponding increase in TMP throughput. Pulp quality may improve, thereby reducing the quantity of purchased kraft or groundwood supplemental pulps. VPP–TMP scenarios We modeled four hypothetical scenarios to assess the feasibility of VPP–TMP in the context of a modeled lightweight coated (LWC) paper mill. Our four VPP–TMP scenarios reflect use of alternative pulpwood species in the TMP process (aspen, spruce, or pine) and also variation in OA pretreatment level for pine. Our four scenarios are labeled as follows: (1) aspen, (2) spruce, (3) pine low OA, and (4) pine high OA. Table I displays values of key process inputs and outputs per day for the base case (without VPP) and the four alternative VPP–TMP scenarios. TMP refiner electric energy input and LWC paper production were held constant in all scenarios relative to the base case, so as to isolate from our analysis the effects of variation in those parameters and focus instead 2. Block diagram of the Value Prior Pulping (VPP)–TMP process concept with hemicellulose extraction and fermentation to ethanol. Base Case Alternative VPP–TMP Scenarios Aspen Spruce Pine Low OA Pine High OA