Research On Dissolving Phosphate Process And System Integration Of Steam Exploded Corn Stalk

Phosphorus is an essential element in human life,which obtained through the dissolution of phosphate.Nowadays,wet-process phosphoric acid is a common phosphorus-dissolving process,but there are problems of high energy consumption,high pollution,and wasting resources,so it is urgent to develop a clean and efficient novel phosphorus dissolving process.The acid-alkali regeneration cycle theory is based on the wet-process phosphoric acid process of the phosphorus chemical industry,and derives the concepts of "recessive acid" and "recessive alkali",which aims to achieve cleaner production when applying to agricultural and industrial production processes.The steam exploded corn stalk(SECS)can produce low molecular organic acids and expose more inherent acid functional groups,which identifies SECS as a typical recessive acid.If SECS can be used as a raw material for phosphorus dissolution,it will be of great significance.In order to achieve this goal,the process of dissolving phosphate by SECS was firstly explored,then humic acid was prepared,finally explored and compared the process of dissolving phosphate with solid-fermentation and liquid fermentation.A novel alkali recovery process with acid-alkali regeneration cycle was explored,lignin was extracted by phosphorus acid and recyclable sodium hydroxide was obtained with calcium hydroxide causticizing.Finally,based on two key technologies,the process system integration of biomass refining was carried out,the energy and material flows were analyzed and the product integration system was planned.The main results were listed as follows:(1)After the corn stalks were steam exploded,hemicellulose was degraded,lignin was softened,and the cell wall surface was ruptured to expose a large number of active groups.The active groups such as hydroxyl and carboxyl groups showed organic acid properties in the autoclave.Adding inorganic salts such as calcium chloride and calcium sulfate can accelerate the degradation of SECS,thereby dissolving the phosphate rock powder.It was found that adding 20%calcium chloride had the best effect on dissolving phosphate.When adding sodium bisulfate at 180? for 5 hours,the dissolving rate was the largest.The humic acid formed from the phosphorus-dissolved straw was used in wheat pot experiments,and the results showed that the plant height,root length,soluble sugar content,chlorophyll content,and relative electrical conductivity of wheat with 0.2%humic acid solution reached the maximum.(2)With the SECS solid-state fermentation medium for culturing Bacillus megaterium,the organic acid content of the medium reaches its maximum at 8th day with 0.1%phosphorus dissolution rate,which is five times greater than liquid fermentation.With the extension of the fermentation time,the surface of phosphate rock had uneven dissolving holes and particle size gradually decreased from 375.43 ?m to 49.73 ?m,which indicated that the phosphate could be effectively dissolved during solid-state fermentation of SECS by Bacillus megaterium.(3)The concept of acid-base regeneration cycle is used in the papermaking alkali recovery process,and the extraction rate of lignin reached 90%,the concentration of recycling sodium hydroxide reached 10 g/L.With adding a certain amount of sodium hydroxide for re-circulation cooking,it was found that the fiber's Kappa value was almost unchanged in five cycles,but the yield of cellulose decreased(4)In the integration of biomass refining systems based on acid-base regeneration cycle,the selected best technical route saves about 42%of energy consumption,and the novel alkali recovery process saves 60%of energy consumption.80%water consumption can be saved through material flow analysis.At the same time,five product systems including papermaking,lignin carbon nanotubes,lignin composite film,xylooligosaccharides and humic acid were formed,which greatly improved the economic utilization value of corn stalk.The results show that the SECS can effectively dissolve phosphate rock.Although its phosphorus dissolution rate is limited,the stalk can be used as soil fertilizer with humic acid prepared.This is a water-saving and energy-saving solid-state fermentation.The phosphoric acid acidification process recovered lignin efficiently at the same time obtaining a circulation of alkali.Process System integration of the biomass refining improved the utilization rate of raw materials with industrial chain extended,which provides new ideas for the clean production of phosphorus chemicals and the utilization of agricultural waste.