Countercurrent cleaning technology of residual alkali in Gracilaria agar production

doi:10.16085/j.issn.1000-6613.2020-0709

Abstract

Abstract:

Agar is a kind of seaweed polysaccharide widely used. In the process of agar extraction, the raw materials Gracilaria for agar production need to be cleaned after being treated with alkali. At present, the water consumption of the process is large, which is an important factor affecting the wastewater discharge for industrial productions of agar. In this paper, countercurrent cleaning process was investigated to reduce the wastewater in cleaning process of Gracilaria after alkali treatment. The ratio of liquid to solid was optimized and the effectiveness in reducing wastewater was measured. The optimized ratio of liquid to soild was 18.1∶1, which was 9.47% lower than that of traditional process. The water consumption in the production of high-strength agar meeting GB 1975—2010 agar quality was greatly reduced by adopting countercurrent cleaning with the optimized liquid to soild ratio. The water consumption was reduced by 77.4%, and 562t water and 1282CNY were saved for producing 1t agar. The scaled-up test showed similar water consumption and agar property to those of the bench scale experiment. The results show that the water consumption and cost can be greatly reduced by using countercurrent cleaning technology with the optimized liquid to solid ratio, indicating an practicable references for the industrial production of agar from Gracilaria.

Key words: waste water, colloid, model, prediction, countercurrent

摘要：

琼脂是一种用途广泛的海藻多糖。琼脂提取过程中，其生产原料江蓠碱处理后需要清洗残碱，目前该工序的耗水量大，是影响琼脂工业化生产排污压力的重要因素。本文采用逆流清洗技术对琼脂提取中的清洗残碱工艺进行研究，优化清洗残碱的液料比并分析逆流清洗的节水效率。通过研究，优化得到清洗残碱的液料比为18.1∶1，相比传统工艺液料比降低了9.47%。采用该液料比进行逆流清洗，琼脂质量仍然符合国家食品安全标准GB 1975—2010中高强度琼脂的相关要求，耗水量却大幅度降低，采用全程多级逆流工艺清洗残碱最高可减少77.4%的用水量，每吨琼脂节水562t，节省成本1282CNY。中试放大试验的用水量和琼脂质量与小试工艺相似。该研究表明，通过优化清洗残碱工艺的液料比及采用逆流清洗技术，可大幅度降低耗水量及工艺成本，为降低江蓠琼脂工业生产过程中的耗水量提供了重要参考。

关键词: 废水, 胶体, 模型, 预测, 逆流

CLC Number:

TQ281

LIANG Yi, NI Hui, JIANG Zedong, ZHU Yanbing, LI Qingbiao. Countercurrent cleaning technology of residual alkali in Gracilaria agar production[J]. Chemical Industry and Engineering Progress, 2021, 40(4): 2258-2269.

梁懿, 倪辉, 姜泽东, 朱艳冰, 李清彪. 江蓠琼脂生产中清洗残碱的逆流工艺[J]. 化工进展, 2021, 40(4): 2258-2269.

Figures/Tables 10

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质量指标	R²	RMSE
透明度	0.972	1.894
凝胶强度	0.895	13.003
凝固温度	0.954	0.283
溶化温度	0.977	0.383
硫酸基	0.922	0.685
3,6-内醚半乳糖	0.947	0.279

质量指标	R²	RMSE
透明度	0.972	1.894
凝胶强度	0.895	13.003
凝固温度	0.954	0.283
溶化温度	0.977	0.383
硫酸基	0.922	0.685
3,6-内醚半乳糖	0.947	0.279

液料比	透明度 /%	凝胶强度 /g·cm^-2	凝固温度 /℃	溶化温度 /℃	硫酸基含量 /%	3,6-内醚半乳糖含量 /%
16.7∶1（模型拟合）	90.1	943	39.7	96.1	1.5	26.3
13.2∶1（模型拟合）	85.6	934	39.2	95.4	2.0	25.7
15.5∶1（模型拟合）	88.9	942	39.5	96.0	1.7	26.1
14.5∶1（模型拟合）	87.7	939	39.4	95.8	1.8	26.0
16.5∶1（模型拟合）	89.9	943	39.6	96.1	1.6	26.2
18.1∶1（模型拟合）	90.9	942	39.6	96.1	1.5	26.4
20∶1（企业参数）	90.1	936	39.5	95.8	1.4	26.4
18.1∶1（验证试验）	86.3	945	39.8	95.7	0.9	27.3

液料比	透明度 /%	凝胶强度 /g·cm^-2	凝固温度 /℃	溶化温度 /℃	硫酸基含量 /%	3,6-内醚半乳糖含量 /%
16.7∶1（模型拟合）	90.1	943	39.7	96.1	1.5	26.3
13.2∶1（模型拟合）	85.6	934	39.2	95.4	2.0	25.7
15.5∶1（模型拟合）	88.9	942	39.5	96.0	1.7	26.1
14.5∶1（模型拟合）	87.7	939	39.4	95.8	1.8	26.0
16.5∶1（模型拟合）	89.9	943	39.6	96.1	1.6	26.2
18.1∶1（模型拟合）	90.9	942	39.6	96.1	1.5	26.4
20∶1（企业参数）	90.1	936	39.5	95.8	1.4	26.4
18.1∶1（验证试验）	86.3	945	39.8	95.7	0.9	27.3

样品	透明度 /%	凝胶强度 /g·cm^-2	凝固温度 /℃	溶化温度 /℃	硫酸基含量 /%	3,6-内醚半乳糖含量 /%
无逆流	91.7±0.6^a	937±5^a	39.3±0.4^a	96.0±0.1^a	1.5±0.0^c	26.5±0.1^a
第二次清洗废水单次单级逆流	90.1±0.5^b	923±7^a	39.1±0.8^a	96.1±0.1^a	1.5±0.1^b	27.0±0.8^a
第三次清洗废水单次单级逆流	90.8±0.2^ab	886±7^b	37.8±0.6^ab	96.0±0.0^a	1.5±0.1^c	26.4±0.5^a
第四次清洗废水单次单级逆流	90.9±0.6^ab	859±7^b	37.2±1.6^b	96.0±0.0^a	1.6±0.0^a	25.5±0.6^a