Biomass resources are abundant and are an important renewable energy source. Hydrogen can be produced through biomass vaporization and microorganisms.
(1) Biomass vaporization to produce hydrogen. Biomass gasification to produce hydrogen is to press biomass raw materials such as firewood, sawdust, wheat straw, rice straw, etc. into a shape, and then perform a vaporization or cracking reaction in a gasification furnace or cracking furnace to produce hydrogen-containing fuel gas. my country's research in the field of biomass vaporization technology has achieved certain results. The Guangzhou Institute of Energy, Chinese Academy of Sciences has conducted research on biomass vaporization for many years. Hydrogen accounts for about 10% of its vaporization products. Although it can be used as domestic fuel in rural areas, the hydrogen content is relatively low. Abroad, due to the improvement of conversion technology, biomass gasification has been able to produce water gas on a large scale, and its hydrogen content has been greatly increased.
(2) Microbial hydrogen production. Microorganisms can also be used to produce hydrogen. Microbial hydrogen production methods have attracted people's attention. Hydrogen can be produced by using microorganisms to perform enzyme-catalyzed reactions at normal temperatures and pressures. There are two main ways of producing hydrogen from biomass: hydrogen production by chemotrophic microorganisms and hydrogen production by photosynthetic microorganisms. Belonging to chemotrophic microorganisms are some strict anaerobes and facultative anaerobes of various fermentation types. The original substrate for hydrogen production by fermentation microorganisms is various carbohydrates, proteins, etc. Currently, there are patents for using carbohydrates to ferment hydrogen, and the generated hydrogen is used as an energy source for power generation. Photosynthetic hydrogen production refers to the hydrogen production process of photosynthetic microorganisms such as microalgae and photosynthetic bacteria that is linked to photosynthesis. In the early 1990s, the Institute of Microbiology of the Chinese Academy of Sciences, Zhejiang Agricultural University and other units conducted "Research on the Isolation and Screening of Hydrogen-Producing Purple Non-Sulfur Photosynthetic Bacteria" and "Research on the Hydrogen Production of Fixed Photosynthetic Bacteria in Wastewater Treatment Processes" and achieved certain results.
At present, an optimized bioreactor using photochemical bacteria to produce hydrogen has appeared abroad, and its hydrogen production scale can reach 2,800 cubic meters of hydrogen per day. This method uses various industrial and domestic organic wastewater and agricultural and sideline product waste as the matrix to continuously cultivate photochemical bacteria. While producing hydrogen, it can purify the wastewater and obtain single-cell proteins. This method has certain development prospects.
(3) Methanol reforming to produce hydrogen. Methanol reforming to produce hydrogen uses methanol as raw material and adopts methanol reforming technology to produce hydrogen. This technology has been commercialized at home and abroad a long time ago. At present, this technology has been widely used in electronics, metallurgy, food and small petrochemical industries. Compared with large-scale hydrogen production by conversion of natural gas, light oil, water gas, etc., methanol reforming hydrogen production technology has the characteristics of short process, low investment, low energy consumption, and no environmental pollution.
The methanol water reforming reaction is a multi-component, multi-reaction gas-solid catalytic complex reaction system. After the methanol liquid and desalted water are mixed in a certain proportion, they are boosted by a metering pump and enter the raw material vaporizer for vaporization and heating.
The heat required for vaporizing raw materials and reactions is provided by a thermal oil furnace system. After the raw material steam is heated to 220°C in the vaporizer, it enters the methanol reforming reactor, where a reforming reaction occurs in the reactor to generate mixed gases such as hydrogen, carbon dioxide, and carbon monoxide. After the reaction, the mixed gas undergoes heat exchange with the raw material liquid through a heat exchanger, is washed in the purification tower, and then sent to the gas-liquid separation buffer tank to separate unreacted methanol and water, so that the methanol content in the reformed gas reaches the specified quality requirements, and the production is completed. gas.
The condensed and washed liquid is a compound of methanol and water, and all is returned to the liquid preparation tank for recycling. The qualified reformed gas passes through a pressure swing adsorption system that consists of multiple adsorption towers operating in parallel and alternately. All impurities are adsorbed and separated at one time, and hydrogen with qualified purity and impurity content is obtained.
(4) Hydrogen production from other hydrogen-containing substances. Research has been conducted abroad on producing hydrogen from hydrogen sulfide. Our country has abundant hydrogen resources. For example, the hydrogen content in the natural gas mined from the Zhaolanzhuang Oil and Gas Field in Hebei Province is as high as over 90%, and its reserves amount to tens of millions of tons. It is a precious resource. There are many methods to produce hydrogen from hydrogen sulfide. In the 1990s, my country carried out various researches. For example, China University of Petroleum conducted "research on the production of hydrogen and sulfur by indirect electrolysis dual reaction system" and made progress. Expand testing.
The Institute of Photosensitivity of the Chinese Academy of Sciences and other units have conducted "research on heterogeneous photocatalytic decomposition of hydrogen sulfide" and "research on hydrogen production by microwave plasma decomposition of hydrogen sulfide". Various research results will lay the foundation for making full and rational use of precious resources and providing clean energy and chemical raw materials in the future.
(5) Recovery of hydrogen by-products from various chemical processes.
A large amount of hydrogen is produced as a by-product in various chemical processes, such as the electrolysis of salt and alkali production, the fermentation and wine making industry, the synthetic ammonia fertilizer industry, and the petroleum refining industry. If appropriate measures can be taken to separate and recover hydrogen, hundreds of millions of cubic meters can be obtained every year. meters of hydrogen.
(6) Use glucose to produce hydrogen. Glucose can also be used to produce hydrogen. In October 1996, British and American scientists used enzymes produced by bacteria living near underground hot water outlets to convert glucose into hydrogen and water. Specifically, it decomposes glucose from cellulose, the basic component of plants including grass, and then uses enzymes to oxidize the glucose to obtain clean fuel hydrogen molecules. The advantages of this hydrogen production method are very obvious. First, the plant cellulose used is rich in sources. Second, enzymes that can multiply rapidly in hot water can be cultivated in large quantities. The method is simple and requires little investment.