Treatment process and energy analysis of hydrothermal treatment coupled with anaerobic digestion on food waste digestate management

doi:10.16085/j.issn.1000-6613.2021-1285

Abstract

Abstract:

Hydrothermal treatment (HTT) was conducted in this study to post-treat the food waste digestate (DFW). The mass flow and energy feasibility of the whole process were analyzed based on the experiment results. Results showed that the dewaterability of DFW was improved by hydrothermal treatment. The yield and moisture content of DFW cake were reduced. Temperature was the most important factor that affects the performance of HTT. At the HTT temperature of 200℃, the yield and moisture content of DFW cake decreased from 71.83kg/t DFW and 88.43% to 22.11kg/t DFW and 76.30%, respectively. The reduction in DFW cake yield and moisture content would decrease subsequent transportation and drying costs significantly. In addition, the hydrothermal process promoted the transfer of DFW organic substances from solid to liquid phase. After coupling with the anaerobic digestion treatment, methane can be produced to effectively recover the energy from liquid phase. A comprehensive calculation on material and energy balance for the DFW treatment process was carried out. The increase of the hydrothermal treatment temperature increased the input of heating energy, but reduced energy input of the subsequent thermal drying process, and increased methane production of DFW liquid products. When HTT temperature and holding time were 160℃ and 60min, the net energy input of the entire treatment process was the least (30.75MJ/t DFW), and 106.48MJ/t DFW was saved compared to the technology without hydrothermal treatment. The recovery rate of heating energy consumption in the hydrothermal process, the moisture content of DFW cake, and the methane production potential of the liquid phase were the main factors that affect the energy balance of the entire process, and were the main directions of process optimization.

Key words: hydrothermal treatment, food waste, digestate, anaerobic digestion, energy balance

摘要：

以水热与厌氧消化耦合工艺作为餐厨垃圾沼渣沼液（digestate of food waste，DFW）的处理过程，探究了DFW处理前后的脱水性能及固、液两相产物的特性，分析了工艺过程中的物质流动、能量输入/输出，并评估了能量平衡的影响因素。结果表明，水热处理改善了DFW脱水性能，降低了脱水后的泥饼产量和含水率。温度是影响水热处理效果的主要因素，处理效果随温度的升高明显提升。当水热温度为200℃时，离心后泥饼的产量和含水率降低最为显著，分别从最初的71.83kg/t DFW和88.43%减小至22.11kg/t DFW和76.30%。此外，水热过程促进了DFW有机物质从固相向液相的转移，通过耦合厌氧消化处理工艺生产甲烷，可以有效地回收液相能量。本研究对整个处理工艺进行了全面的物质和能量衡算。水热处理温度的提高增加了加热能量的输入，但减少了后续热干化过程的能量输入，并增加了DFW液相产物的产甲烷潜力。当水热温度为160℃、保温时间为60min时，水热与厌氧消化耦合工艺净能量输入最少（30.75MJ/t DFW），相比于不采用水热技术处理节省106.48MJ/t DFW。水热过程热能的回收率、脱水后泥饼的含水率、液相产物的产甲烷潜势是影响工艺过程能量净消耗的主要因素，是工艺优化的主要方向。

关键词: 水热处理, 餐厨垃圾, 沼渣沼液, 厌氧消化, 能量平衡

CLC Number:

X703

SHAO Mingshuai, ZHANG Chao, WU Huanan, WANG Ning, CHEN Qindong, XU Qiyong. Treatment process and energy analysis of hydrothermal treatment coupled with anaerobic digestion on food waste digestate management[J]. Chemical Industry and Engineering Progress, 2022, 41(5): 2733-2742.

邵明帅, 张超, 吴华南, 王宁, 陈钦冬, 徐期勇. 水热耦合厌氧消化技术处理餐厨垃圾沼渣沼液及工艺能耗分析[J]. 化工进展, 2022, 41(5): 2733-2742.

Figures/Tables 9

含水率

COD

/mg·L^-1

泥饼	固体产率^①（质量分数）/%	灰分（质量分数）/%	挥发分（质量分数）/%	C（质量分数）/%	HHV/MJ·kg^-1
DFW	100.0	26.3	68.1	36.5	15.18
H60-80	80.4	30.9	66.1	34.2	14.40
H60-100	91.0	31.5	64.0	33.8	14.67
H60-120	79.5	35.3	62.6	31.8	13.40
H60-140	64.4	40.3	56.0	31.3	12.81
H60-160	57.4	45.45	51.4	30.8	13.34
H60-180	47.7	46.3	50.4	28.9	13.23
H60-200	43.1	54.2	42.2	25.8	12.29

参数	DFW	H60-80	H60-100	H60-120	H60-140	H60-160	H60-180	H60-200	参数物理意义
M_w /kg	975	975	975	975	975	975	975	975	DFW中水的含量
M_s /kg	25	25	25	25	25	25	25	25	DFW中固体的含量
M_cw/kg	63.52	43.14	41.86	34.09	27.68	25.61	19.74	16.87	泥饼中的水含量
M_cs /kg	8.31	7.21	9.10	8.58	7.05	6.30	5.10	5.24	泥饼中固体含量
$V C H 4$ /m³	0.98	1.78	1.99	2.33	2.84	3.16	3.16	3.03	甲烷累计产量
M_rw/kg	51.05	32.33	28.21	21.23	17.10	16.16	12.08	9.01	将泥饼干燥至60%含水率所需脱水量
TS （质量分数）/%	2.49	2.00	2.72	1.98	1.60	1.43	1.19	1.07	总固体含量
c_w /kJ·kg^-1·℃^-1	4.186	4.186	4.186	4.186	4.186	4.186	4.186	4.186	水的比热容
c_s /kJ·kg^-1·℃^-1	0.971	0.971	0.971	0.971	0.971	0.971	0.971	0.971	DFW中固体的比热容
T_HTT /℃	—	80	100	120	140	160	180	200	水热处理温度
$? H w ?$ /kJ·kg^-1	2257.2	2257.2	2257.2	2257.2	2257.2	2257.2	2257.2	2257.2	水的气化潜热
q /MJ·m^-3CH₄	35.88	35.88	35.88	35.88	35.88	35.88	35.88	35.88	甲烷气体的低位热值
v/kW·h·kg^-1	0.04	0.04	0.04	0.04	0.04	0.04	0.04	0.04	单位质量样品离心脱水用电量
ξ /%	—	85	85	85	85	85	85	85	加热能耗的回收效率
k /W·m^-2·℃^-1	1	1	1	1	1	1	1	1	热转化效率
Τ/d	35	35	35	35	35	35	35	35	厌氧发酵的天数

参数	DFW	H60-80	H60-100	H60-120	H60-140	H60-160	H60-180	H60-200	参数物理意义
M_w /kg	975	975	975	975	975	975	975	975	DFW中水的含量
M_s /kg	25	25	25	25	25	25	25	25	DFW中固体的含量
M_cw/kg	63.52	43.14	41.86	34.09	27.68	25.61	19.74	16.87	泥饼中的水含量
M_cs /kg	8.31	7.21	9.10	8.58	7.05	6.30	5.10	5.24	泥饼中固体含量
$V C H 4$ /m³	0.98	1.78	1.99	2.33	2.84	3.16	3.16	3.03	甲烷累计产量
M_rw/kg	51.05	32.33	28.21	21.23	17.10	16.16	12.08	9.01	将泥饼干燥至60%含水率所需脱水量
TS （质量分数）/%	2.49	2.00	2.72	1.98	1.60	1.43	1.19	1.07	总固体含量
c_w /kJ·kg^-1·℃^-1	4.186	4.186	4.186	4.186	4.186	4.186	4.186	4.186	水的比热容
c_s /kJ·kg^-1·℃^-1	0.971	0.971	0.971	0.971	0.971	0.971	0.971	0.971	DFW中固体的比热容
T_HTT /℃	—	80	100	120	140	160	180	200	水热处理温度
$? H w ?$ /kJ·kg^-1	2257.2	2257.2	2257.2	2257.2	2257.2	2257.2	2257.2	2257.2	水的气化潜热
q /MJ·m^-3CH₄	35.88	35.88	35.88	35.88	35.88	35.88	35.88	35.88	甲烷气体的低位热值
v/kW·h·kg^-1	0.04	0.04	0.04	0.04	0.04	0.04	0.04	0.04	单位质量样品离心脱水用电量
ξ /%	—	85	85	85	85	85	85	85	加热能耗的回收效率
k /W·m^-2·℃^-1	1	1	1	1	1	1	1	1	热转化效率
Τ/d	35	35	35	35	35	35	35	35	厌氧发酵的天数

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