ANAEROBIC DIGESTION STABILITY TEST BY SHEWHART CONTROL CHART

ABSTRACT The anaerobic digestion (AD) operation complexity raise the importance of stability testing to verify whether the operating conditions are under control and whether the process is working as required. The current method of verifying process stability is by a range of the ratio between volatile fatty acidity and total alkalinity (VFA/ TA) within which stable conditions are brought about; these rates vary with the content of organic material. A few indicators as pH or constant biogas production are also used. Therefore, the aim of this study was to propose the use of Shewhart control chart for individual measures as a stability test for AD, as well as to demonstrate its use in poultry litter AD. The method showed to be advantageous since it standardizes a variation range for the process according to the average and verifies the stability by direct measures, such as organic material removal efficiency and biogas production.

摘要 厌氧消化（anaerobic digestion，AD）的运行复杂度日益提升，使得稳定性检测的重要性愈发凸显，其核心目标为验证运行工况是否处于可控状态、工艺是否按预期稳定运行。当前的工艺稳定性验证方法多以挥发性脂肪酸与总碱度之比（volatile fatty acidity and total alkalinity，VFA/TA）的阈值区间作为判定依据，该区间内可维持稳定的运行工况；且该比值会随有机物料的含量发生变化。此外，pH值、稳定沼气产率等少量指标也被用于稳定性评估。因此，本研究旨在提出将单值休哈特控制图（Shewhart control chart for individual measures）作为厌氧消化的稳定性检测方法，并展示其在家禽垫料厌氧消化工艺中的应用。该方法具备显著优势：它可基于工艺均值标准化出波动区间，并通过有机物料去除效率、沼气产率等直接检测指标验证工艺稳定性。