Pilot-plant test of ultrafiltration-reverse osmosis membrane separation coupling with vacuum concentration technology of chicken bone extract

Abstract: In this study, the concentration technologies of chicken bone extract (Brix=4%), involving vacuum concentration technology and other two membrane combination concentration technologies, were investigated with the pilot scale production. Firstly, the conventional vacuum concentration (VC) technology was studied by determining the concentration rate and the water removed rate, and then the properties of different single osmotic membrane were analyzed by detecting the changes of membrane flux and the loss rates of material, dry matter and protein. After that, we also studied the membrane combination separation technologies that included the microfiltration-reverse osmosis combination (MF-RO) technology and ultrafiltration-reverse osmosis combination (UF-RO) technology. Ultimately, we developed a new concentration technology of chicken bone extract that was, a kind of gradient membrane combination coupling with the vacuum concentration technology, and ultrafiltration-reverse osmosis-vacuum concentration (UF-RO-VC) technology. Simultaneously, the advantages and disadvantages of the traditional VC technology were compared with the reverse osmosis-vacuum concentration (RO-VC) technology and UF-RO-VC technology. Results suggested that, as for the conventional VC technology, the Brix increased very slowly prior to 60 min of the concentration, which resulted in decreasing the rate of concentration and much more energy consumption. And the results of single membrane concentration indicated that the membrane fluxes of microfiltration (MF), ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO) were all decreased with the proceeding of concentration, and the membrane flux showed the negative correlation with the membrane diameter. Besides that, these four different membrane separation technologies could contribute to some losses of the chicken bone extract, which included the materials loss (the loss rates were 0.5%, 6.25%, 4% and 7.1%, respectively), the dry matter loss (the loss rates were 1.6%, 19.4%, 22.4% and 20%, respectively) and the protein loss (the loss rates were 35.8%, 25.7%, 22% and 16%, respectively). For the membrane combination separation technologies, results indicated UF-RO technology was able to decrease dramatically the materials and dry matter loss (P<0.01), and meanwhile the membrane flux of the reverse osmosis membrane was increased 2 - 3 times, which was compared with the MF-RO technology. The chicken bone extract of 360 kg, as the pilot-plant test, was concentrated through the technologies that included the VC technology, RO-VC technology and UF-RO-VC technology. As for these three concentration technologies, the results suggested that the time-consuming was 120, 105 and 110 min, respectively; power consumption was 1.62, 2.81and 3.57 kW·h, which was concerted into standard coal consumption being 0.199 1 kg, 0.345 3 kg and 0.438 8 kg, respectively; standard burning coal converting from steam consumption was 63.46 kg, 23.8 kg and 10.58 kg, respectively; emission of pollution gas SO2 was 0.057 6 kg, 0.021 9 kg and 0.010 1 kg, and NOx was 0.068 2, 0.0279 and 0.014 6 kg, respectively. Eventually, the total cost was 33.03, 50.78 and 27.85 yuan, and total standard coal consumption was 63.659 1 kg, 24.145 3 kg and 11.018 8 kg. Taken together, the UF-RO-VC technology can be considered as an optimal concentration technology to obtain the chicken bone extract. Comparing with the conventional VC technology, this new kind of concentration technology could be recognized to be much more friendly to environment as it is capable of concentrating the chicken bone extract with decreasing the cost, saving concentration time, reducing the consumption of standard coal and emission of pollution gases significantly (P<0.01).