Transactions of the Chinese Society of Agricultural Engineering, the 1st in Agricultural Engineering, is supervised by China Association for Science and Technology, and sponsored by Chinese Society of Agricultural Engineering. It aims to introduce the latest scientific achievements and developing trends of Agricultural Engineering and provides the academic developments abroad and domestic of the discipline. The scope covers agricultural water-soil engineering, agricultural information and electrical technology, agricultural products processing engineering.
The journal is included in EI, JST, Pж(AJ), CA and CSCD.
Editor-in-Chief Zhu Ming
Deputy Editor-in-Chief Wei Xiuju Zhang Ruihong Xi Weimin Wang Liu Wang Yingkuan Li Pingping Ying Yibin Tong Jin Yun Wenju Zhao Chunjiang Kang Shaozhong
Reasonable planting pattern can increase soybean yield. At present, the soybean cultivation models in the cold region of northeast China mainly include conventional ridge planting mode, three row planting pattern on big ridge and four row planting mode on big ridge. The compact planting pattern of big ridge three-row is becoming popularizing gradually. The big ridge three-row reduces the row spacing, increases plant spacing and plant density than the traditional planting pattern. This way of planting soybean increases crop yield by reducing row spacing between soybean plants to increase planting density and to increase the number of plants protected per unit area. The three-row soybean planting pattern means that three rows of soybean are planted evenly on the ridge table of 1.1 m big ridge, and the marginal effect of the ridge platform is fully utilized. The outermost two rows of soybean are 400 mm apart and the spacing of each row of soybean is 200 mm. According to the agronomic requirement and technology for the model of compact planting soybean with three rows on 1.1 m grand ridge, the problems of compact structure and poor passing ability on planting unit are caused by the matching planter that uses single-row planting unit devices in dislocation parallel. The pneumatic cylinder precision seed-metering device for soybean matching compact planting soybean with three rows on 1.1 m grand ridge was designed, combined the features of mechanical clearing and gravitational dropping. The structural parameters of the key components of the three-row soybean seed-metering device on ridge were determined. The diameter of the cylinder is 200 mm, the length of the cylinder is 500 mm, the axial hole of the cylinder is three rows and the distance is 200 mm, and the number of single row holes is 40. The sealing problem of the pneumatic cylinder seed-metering device is solved through the innovative design of the structure. In order to effectively remove the multiple seeds adsorbed on the hole and keep only one seed in each hole, a scraper seed cleaning device was designed. In order to ensure that the seed can be planted freely in the seeding area, a pressure relief device for isolating the pressure difference inside and outside the hole was designed. In this study, the key structural parameters and the mechanical model of seed-filling process were determined through theoretical analysis. The experiment was employed through the method of quadratic orthogonal rotating center combination of three factors and five levels according to the GB6973-2005 national standard. In test, soybean seed Heinong 48 was selected as experimental material. Combining with extensive pre-experiment and theoretical analysis, the vacuum degree, forward speed and hole diameter were taken as main influencing factors, the seed qualified index, multiple index, missing index and variation coefficient of apiece row seeding mass were taken as response indexes. The results showed that: the order of the contribution rates on the effect of qualified index was vacuum degree, working speed, hole diameter, the order of the contribution rates on the effect of multiple index was vacuum degree, hole diameter, working speed, the order of the contribution rates on the effect of missing index was vacuum degree, working speed, hole diameter, the order of the contribution rates on the effect of variation coefficient of apiece row seeding mass was, working speed, vacuum degree, hole diameter. The optimal combination of parameters was as follows, the hole diameter was 4.5 mm, the vacuum degree was between 4.7 and 5.9 kPa, the working speed was lower than 9.1 km/h, and under the optimal combinations, the qualified index was not less than 95%, the multiple index was not more than 3%, the missing index was not more than 2%, and the variation coefficient of apiece row seeding mass was not more than 6.5%. The verification test was repeated 10 times on the JPS-12 seed-metering test beds, the results indicated that the actual test results were in agreement with the optimization results. The results of the research laid a foundation for the development of pneumatic cylinder grand ridge three-row seed-metering device for soybean, and provided a reference for the research of soybean narrow-row and flat-dense planter.
With the problems of high cost and low biogas yield in traditional acidification recovery method of anaerobic digestion (AD), steel slag was selected to add in the biogas production recovery system in this study, which was the by-product of steel making, and the effect of steel slag on the recovery after acidification was compared with that of alkali. The results showed that the acidification system could be restored by adding steel slag and alkali on the first day, and the cumulative biogas production rate on the 40th day was 285.33 mL/g with the steel slag adding, which was increased by 25.8% compared with the traditional method of adding alkali. At the same time, the pH values, total volatile fatty acid (TVFA), alkalinity (TA), and volatile fatty acids (VFAs) of the steel slag and alkali groups after recovering biogas production were monitored and analyzed. The TVFA was slowly decreased till exhausted and the TA was basically around 12.45 g/L in steel slag group; on the contrary, the TVFA increased in first two days and then decreased and the TA slowed down till 8.72 g/L in alkali group. And the
t test was used to analyze the data variation of biogas yield, TA, TVFA and pH value in alkali and steel slag groups (each group had 21 samples). The significant level of the biogas yield (0.005) was less than 0.05, while the significant levels of TA, TVFA and pH value were more than 0.05. Therefore, the biogas yield in the two groups was significantly different, but the difference of TA, TVFA and pH value was not significant. Meanwhile, the trend of acetic acid, propionic acid, butyric acid and lactic acid was observed. The results demonstrated that the recovery of each kind of acid in steel slag group was 3–4 days faster than that in alkali group, and the order of recovery rate was successively butyric acid, lactic acid, acetic acid and propionic acid; the significant levels of acetic acid, lactic acid, propionic acid and butyric acid were 0.064, 0.068, 0.076 and 0.098, respectively, all greater than 0.05, which indicated that the differences among the four kinds of acids were not significant in the recovery stage. The ratio of TVFA to TA and the ratio of propionic acid to acetic acid were studied, and the results indicated the two ratios in two groups were both at the best level after recovery for 15 days, and on the 8th day the two ratios in steel slag group dropped to 0.38 and 0.081, respectively, and then decreased to below 0.05; there was the same trend in alkali group. The
P values of the ratio of VFA to TA and the ratio of propionic acid to acetic acid between alkali treatment and steel slag treatment were 0.15 and 0.26, respectively, which were both more than 0.05, indicating that the changes of data in these two ratios were not significant. This showed that the two systems could be recovered quickly in the recovery stage. At last, the content of heavy metals in the digestive juice after recovery was analyzed, and the results indicated that the two kinds of biogas producing methods fully satisfied the requirements of the technical specification of NY/T 2065-2011 biogas fertilizer application. The paper provides a way to recover biogas from the traditional regeneration acidification liquid, which solves the problems of the easy acidification of the actual engineering and the high cost of the recovery of biogas production.
The content of contaminants in manure wastewater is much higher than that in urban domestic sewage, which leads to high and sophisticated biochemical treatment and high cost of wastewater treatment. The high-concentration pollutants in manure wastewater mainly come from the dissolution or decomposition of solid feces. Therefore, solid–liquid separation immediately after the production of manure wastewater can effectively separate the solids from the wastewater. Accordingly, the content of pollutants in the wastewater can be reduced. In this study, we carried out solid–liquid separation to investigate the ability of centrifugation in the removal of total solids (TS), as well as the reduction of chemical oxygen demand (COD), nitrogen (N) and phosphorus (P) from pig manure wastewater. Besides, we analyzed the economic benefits of centrifugation before anaerobic digestion (AD). The results showed that the centrifugal separation carried out at 1 000–3 000 r/min for 0.5 min effectively removed the TS, COD, and N and P from pig manure wastewater (TS = 7.3 g/L), and the removal rates were 50%–65%, 45%–55%, and 30%–50%, respectively. Moreover, the removal rates increased as the rotation speed increased from 1 000 to 3 000 r/min. In addition, the separation efficiencies for N and P compounds were lower than that for dry matters, which was similar to the previous reports. This was mainly because the N and P compounds were easier to dissolve in water or be decomposed by microorganisms than carbohydrates, the major components of solids. Biodegradable solid reduction rate (BSRR) is defined as the reduced percentage of methane potential of manure wastewater after centrifugation, which can be calculated as the difference in the ratio of waste water methane potential before and after centrifugation. BSRR can be used as a basis for the adjustment of the construction volume of anaerobic pools and the hydraulic retention time (HRT) in AD process. According to the result of biochemical methane potential (BMP) test, the content of biodegradable materials could be reduced significantly by centrifugal separation, and the maximum BSRR of 57.6% was observed in the case of 3 000 r/min. This result meant that centrifugal separation could greatly save the construction volume and HRT in AD process. For a pig farm with ten thousand pigs, the amount of wastewater produced per day was about one hundred tons, and the combined treatment of centrifugation with AD could save 45% of the wastewater treatment cost compared with that of only AD treatment. If the incomes of biogas and separated solid manure were taken into consideration, the comprehensive incomes of centrifugation before AD and only AD were positive, and the former was 50% higher than the later. However, in practice, the biogas and solid manure are hard to get a profit due to many complex factors. Therefore, the meaning of solid–liquid separation before biochemical treatment would be more important. Moreover, the costs of other treatments after AD process and energy consumption for heat preservation of pool can be greatly reduced due to the partial reduction of N and P contaminants in the centrifugation process. This study can provide new design ideas and reference for large and medium-sized farms to save the treatment cost of wastewater and construction investment.
