Research On Hydrogen Production By Gasification Of Organic Solid Waste From Agriculture And Forestry In Calcium Looping

As is well known,the rapid development of industry and agriculture result in the continually increasing demand for energy.Producing green hydrogen from agricultural and forest organic solid waste can not only avoid greenhouse gas emissions caused by the use of fossil fuels,but also achieve the resource utilization of organic solid waste and green energy supply.At present,experimental research on hydrogen production from organic solid waste in agriculture and forestry mostly carried out by using modified calcium as the based adsorbents.However,it is difficult to perform a large scale manufacture,because of the high cost and complex process for the preparation of modified calcium.As an efficient heat and mass transfer equipment,fluidized bed,especially double fluidized bed has good adaptability to heterogeneous and high-temperature reactions,that provideovids an equipment foundation for using low price and wide access industrial limestone as a carbon adsorbent,with the advantages of stable bed layer,high reliability,and strong operational flexibility.Furthermore,the difficulty of hydrogen storage and transportation is an important constraint factor for the application of green hydrogen.Methanol is a fuel with good application prospects and an important basic chemical raw material.The use of hydrogen rich synthesis gas to prepare methanol technology,which converts hydrogen into liquid methanol,not only facilitates storage and transportation,but also expands the application prospects of green hydrogen.This article conducts experimental research on the influencing factors and laws of biomass gasification for hydrogen production using the calcium looping chemistry chain,and simulates a dual fluidized bed reactor for biomass gasification and hydrogen production using Aspen Plus software.Based on this,the feasibility of using industrial limestone as a carbon adsorbent for fluidized bed hydrogen production research is analyzed and verified.In order to expand the application of green hydrogen,this article also simulates and systematically analyzes the process flow and economic feasibility of coupling biomass gasification for hydrogen production using the calcium looping chemistry chain with electrolytic water for methanol production.The main work is as follows:At first,a bubbling fluidized bed experimental setup for calcium-based biomass gasification is designed and constructed.Using spruce wood particles as the raw material,mixed with industrial limestone at different calcium-to-carbon ratios,the experiment of calcium-based biomass gasification for hydrogen production is carried out with steam as the gasification medium.The effects of temperature,steam-to-biomass ratio（S/B）,and calcium-to-carbon molar ratio（Ca/C）on the characteristics of producing hydrogen-rich gas through gasification are studied.The results show that the volume fraction of H₂ in the gasification product increases with the increase of temperature within the range of 600℃-700℃,while the heating value of the syngas shows a trend of first increasing and then decreasing with the increase of temperature.The volume concentration of H₂in the syngas gradually increases with the increase of S/B ratio,and increasing Ca/C ratio greatly enhances the volume concentration of H₂ in the product gas.Considering all factors,the optimal reaction conditions are determined as 650℃for temperature,1for S/B ratio,and 0.4 for Ca/C ratio.Then,using Aspen Plus software to establish a simulation model for the double fluidized bed reactor used in the calcium-based biomass gasification hydrogen production process.The effects of circulating bed material amount,equivalence ratio of air（ER）,steam-to-biomass ratio（S/B）,and addition of calcium oxide on biomass gasification were studied.The results showed that increasing the biomass feeding amount and circulating bed material amount could increase the volume fraction of H₂ in the synthesis gas,as well as improve the gas heating value and gasification efficiency.Increasing the air equivalence ratio could increase the gas production rate and carbon conversion rate of biomass gasification,but the volume fraction of H₂,gas heating value,and gasification efficiency would decrease as the air equivalence ratio increased.Increasing the S/B could increase the gas heating value,carbon conversion rate,and gasification efficiency,but the volume fraction of H₂ and heating value would continuously decrease.Adding Ca O to the gasifier could increase the concentration of H₂ and improve the gas heating value.To improve the quality of the synthesis gas,it is recommended to reduce the circulating bed material amount and lower the gasifier temperature,so that the biomass could undergo gasification reaction at an appropriate temperature.Finally,based on the calcium chemical looping biomass gasification and hydrogen production dual fluidized bed reactor model,a methanol preparation system for producing hydrogen-rich synthesis gas from biomass coupled with hydrogen production from electrolyzed water was established.The effects of air equivalence ratio and S/B on methanol production were studied.The results showed that the methanol yield increased with the increase of air equivalence ratio,and the increase of S/B resulted in a higher methanol yield than that of air as gasifying agent.When water vapor was used as gasifying agent,the biomass gasification and synthesis gas production for methanol production had good development prospects when the biomass price was below 690yuan/ton.