Dry-grind process

Fig. 1. Schematic of corn dry grind process with fiber conversion to ethanol. DDGS, distillers dried grains with solubles.

Fig. 2. Dry-grind process with pretreatment option for production of HDG.

In a conventional dry grind process, ground com is mixed with water to produce slurry. The slurry is cooked the slurry starch liquefied, saccharified and fermented to produce ethanol. The remaining nonfermentables (germ, fiber, and protein) are recovered at the end of the dry grind process as an animal food co-product, called distiller dried grains with solubles or DDGS. 

Kwiatowski, J. R McAloon, A. J. Taylor, F. and D. B. Johnston, 2006, Modeling the Process and Costs of Fuel Ethanol Production by the Com Dry-Grind Process, Industrial Crops and Products, 23, 288-296. 

For the social criteria, two methods are applied in this study. A more detailed safety-related discussion of the bioethanol process can be found in the open Hterature [45]. In the first method, safety during operation, operability of the plant, safe startup and shutdown, and location-specific demands are selected as four soft indicators for sustainability assessment. The evaluation and justification of each indicator are provided in Table 6.13, where standard definition and scaling system can be found in Othman et al. [1]. In this approach, the process with the higher score is more desirable. Again the dry grind process is found to be superior. 

Ethanol is highly flammable. Corn dust is explosive [54]. Mechanical equipment presents serious entanglement and amputation hazards. Wet milling process involves more dust and mechanical equipment. Wet milling process also has SO2 emission problem, which the dry grind process does not have... 

In Eqs. [6.14] and [6.15] Me is the flow rate of chemical C Icj is the score of the chemical inherent safety subindex of chemical C Np is the number of equipment P and Ipi is the score of the process inherent safety subindex of equipment P. Again the dry grind process is found to be superior. In summary, it is observed that the dry grind process is superior to the wet milling process for aU three sustainability measures. 

Kwiatkowski JR, McAloon AJ, Taylor F, Johnston DB. Modehng the process and costs of fuel ethanol production by the corn dry-grind process. Ind Crops Prod 2006 23 288-96. 

Classification associated with dry grinding processes Types and operating principles ... 

The process flow diagrams of a com-to-ethanol biorefinery involving a dry grind process and a wet mill process using enzymes are shown in Figs. 24.5 and 24.6, respectively. 

Singh, V. Johnston, D.B., Naidu, K., Raush, K.D., Belyea, R.L., and Tumbleson, M.E. 2005. Comparison of modified dry grind processes for fermentation characteristics and DDGS composition. Cereal Chem. 82 187-190. 

Singh, V., Batie, C.J., Aux, G.W., Rausch, K.D., Miller, C., 2006a. Dry-grind processing of com with endogenous liquefaction enzymes. Cereal Chemistry 83 (4), 317—320. 

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