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| 1 | Development of Novel Products from Agro-Wastes(Rice Husks)and Characterization in Kenya显示文摘Rice growing is a popular agricultural activity in some areas in Kenya.The challenge is in the disposal of RH(Rice Husks).Rice production results in 20%RH as byproduct.Simple incineration of RH results in RH ash which is a source of valuable chemical products.The ash is 87-97%silica,highly porous and light weight,with a very high external surface area.The end product of RHA(Rice Husk Ash)after chemical treatment,sodium silicate,is a precious commodity that has myriad applications especially in detergent manufacture and soap production.The objective was to determine the best conditions to synthesize silica from agro-wastes(RH)in Kenya.The yield(%SiO2)of the HCl(Hydrochloric Acid)leached RH at 500°C was the highest at 99.2%.Overall these conditions were the best in producing silicate.Percentage(%)removal of each metal is different due to its chemical form in RH.The removal percentage of K is especially remarkable.And 0.5 M HCl leaching followed by thermal treatment of 600°C gave the best increase in%silica dioxide.The same process removed the most metallic impurities(P2O5,K2O,CaO,Mn and Zn).Leaching with 0.5 M HCl followed with thermal treatment of 500°C gave the best overall yield in%silica dioxide.An increase in temperature from 600°C slightly reduced the%silica dioxide content.The 0.5 M HCl used in these trials was able to produce 99.17%silica content from the Mwea RH.The SiO2 obtained with the water washed RH sample is 97.37%as compared 99.17%(HCl-washed)and 99.02%(H2SO4(Sulphuric Acid)-leached).The FTIR(Fourier Transform Infrared Spectroscopy)spectra indicates HCl leaching avails more silica content than H2SO4 leaching. | Raphael Kungu Paul Njogu Robert Kinyua | 2019 | Journal of Environmental Science and Engineering(A)2019，8，1： | 0 |
| 2 | Performance Assessment of Heat Exchangers for Process Heat Integration显示文摘Pinch Analysis is an attractive solution for reduction of thermal energy costs in thermo-chemical industries.In this approach,maximum internally recoverable heat is determined and a heat exchange network is designed to meet the recovery targets.The thermal performance of a heat exchanger over its lifetime is however a concern to industries.Thermal performance of a heat exchanger is affected by many factors which include the physical prop-erties of the shell and tube materials,and the chemical properties of the heat transferfluid.In this study,thermal performance of shell and tube heat exchangers designed to meet heat recovery targets in a Pinch Analysis study is simulated.The aim of this paper is to present predictions of thermal performances of shell and tube heat exchan-gers with different heat transferfluids and geometries as they undergo fouling degradation.Engineering approaches based on thermodynamic analysis,heat balance and Kern Design equations,as well as what-if simu-lation modeling are used in this work.Shell and tube heat exchangers were designed to meet internal heat recov-ery targets for three process plants,A,B and C.These targets were published in a separate paper.The effects of degradation of the tubes-due to incremental growth of fouling resistance-on thermal performance of the exchan-ger were simulated using Visual Basic Analysis(VBA).Overall,it was found that growth in fouling reduces ther-mal efficiency of shell and tube heat exchangers with an exponential relationship.An increase of 100%of fouling resistance leads to an average reduction of 0.37%heat transfer.Higher values of logarithmic mean temperature difference(LMTD)and higher ratios of external diameter to internal diameter of the exchanger tubes amplify the effect of fouling growth on thermal performance of the exchangers.The results of this work can be applied in pinch analysis,during design of heat exchangers to meet the internal heat recovery targets,especially in predicting how fouling growth can affect these targets.This can also be useful in helping operators of shell and tube heat exchangers to determine cleaning intervals of the exchangers to avoid heat transfer loss. | Fenwicks Shombe Musonye Hiram Ndiritu Robert Kinyua | 2021 | Energy Engineering2021，118，2： | 0 |
| 3 | Green Chemistry Preparation and Characterization of Rice Husk Derived Silica Gel in Kenya显示文摘Rice is a grass seed from Oryza glaberrima species also known as the African rice.In Kenya,rice is mostly grown in Central(Mwea)and Nyanza(Ahero,West Kano,Migori and Kuria)areas.Milling rice produces rice husks as by-products which can be sources of valuable chemical products(silica gel,sodium silicate).In trials to produce silica gel from rice husks,rice husks were charred in a combustion chamber(30 min)then ashed in a Muffle furnace(Advantec KL-420)at different temperatures.The ashes were then leached with distilled water/acids to remove metal oxides.Sixty grams(60 g)of the leached RHA(Rice Husk Ash)was mixed with 300 mL of 3 M NaOH solution in a Pyrex 500 mL beaker and boiled at 100℃(1 h).The silica gel samples were characterized using several methods.Elemental analysis was done using TXRF(Total X-Ray Fluorescence),while FTIR(Fourier-Transform Infrared Spectroscopy)was used to obtain an infrared spectrum of absorption of the silica sample.Results of the analysis conform to local and international quality standards.The rice husks had an average moisture content of 7.07%and 1.00-2.00 mm diameter.And 1.74%of the rice husk had pore sizes of about 0.710 mm.The average ash content was 22.65%.At 600℃,leaching with water yielded 98.2%silica compared with 99.1%(H2SO4)and 96.9%(HCl).At 500℃,leaching with HCl/H2SO4 causes a decrease.At 500℃,the availability of SiO2 is more for water leached samples.At 400℃,water leaching gave 98.49%silica while HCl leaching was 97.85%silica and H2SO4 was 99.41%.Silica is a precursor of silica gel.Statistical analyses imply water leaching RHA instead of acid leaching at 500℃ will produce a significant amount of silica gel.The open burn samples produced equal or better SiO2(silica gel precursor)yields compared with the incineration samples.FTIR analysis of the silica gel sample compared well with adsorption peaks of silica gel in literature.XRD(X-Ray Diffraction)analysis produced a pattern consistent with other XRD patterns of silica gel published by other researchers. | Raphael Kungu Paul Njogu Robert Kinyua Jackton Kiptoo | 2019 | Journal of Environmental Science and Engineering(A)2019，8，6： | 0 |
| 4 | An Analysis of Solid Waste Generation and Characterization in Thika Municipality of Kiambu County, Kenya显示文摘 | Mugo Ephantus Kinyua Robert Njogu Paul | 2015 | Journal of Environmental Science and Engineering(B)2015，4，4： | 0 |
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