1. 1 hydrogen production by electrolysis of water.
Hydrogen production by electrolysis of water is one of the widely used and mature methods at present. The process of hydrogen production from water is the combustion of hydrogen and oxygen to produce water.
Inverse process, so as long as a certain form of energy is provided, water can be decomposed. The efficiency of providing electric energy to decompose water to produce hydrogen is generally in
75-85%, its process is simple and pollution-free, but it consumes a lot of electricity, so its application is limited. Hydrogen production from electrolyzed water with peak-valley difference in power grid also has characteristics as a means of energy storage. China is rich in hydropower resources, and hydrogen production by hydropower generation and electrolysis of water has its development prospects. Solar energy is inexhaustible, and the method of producing hydrogen by photoelectric is called solar hydrogen energy system, and experimental research has been carried out abroad. With the improvement of energy conversion efficiency, the reduction of cost and the extension of service life of solar cells, the prospect of hydrogen production is immeasurable. At the same time, solar energy, wind energy and ocean energy can also generate hydrogen through electricity, and use hydrogen as an intermediate energy carrier to adjust and store the converted energy, which makes the energy supply to users more flexible and convenient. The surplus electric energy of the power supply system can also be used to electrolyze water to generate hydrogen, so as to achieve the purpose of energy storage. There are hundreds of water electrolysis hydrogen production devices of various scales in China, but all of them are small electrolysis hydrogen production equipment, and their purpose is to produce hydrogen as raw materials rather than energy. With the gradual expansion of the application of hydrogen energy, the method of hydrogen production by electrolysis of water will be developed.
1.2 Hydrogen production from fossil fuels
Hydrogen production from coal, oil and natural gas is the main method of hydrogen production at present. The technology of this method is mature in China, and industrial production equipment has been built.
(1) Hydrogen production from coal
In China's energy structure, coal will be the main energy source for a long time to come. How to improve the utilization efficiency of coal
Reducing environmental pollution is a subject that needs continuous research, and converting coal into hydrogen is one of its ways.
There are two main methods to produce hydrogen-containing gas from coal: one is coking (or high temperature dry distillation) of coal, and the other is gasification of coal. Coking means that coal is made into coke at 90- 1000℃ under the condition of air isolation, and the by-product is coke oven gas. The composition of coke oven gas contains 55-60% (by volume) hydrogen, 23-27% methane and 6-8% carbon monoxide. 300-350m3 gas can be obtained per ton of coal, which can be used as city gas.
It is also a raw material for producing hydrogen. Coal gasification means that coal reacts with gasifying agent at high temperature, normal pressure or pressure and is converted into gas products. gasify
The agent is steam or oxygen (air), and the gas product contains hydrogen and other components, and its content varies with different gasification methods. There are a large number of small and medium-sized hydrogen plants in China, all of which use coal as raw material, and the hydrogen-containing gas produced after gasification is used as raw material for synthetic ammonia. This is a hydrogen source acquisition method with China characteristics. Using OGI fixed bed gasifier, water gas can be produced by intermittent operation. The device has less investment and simple operation. Its gas products are mainly composed of hydrogen and carbon monoxide, of which hydrogen can reach more than 60%, and pure hydrogen can be produced after conversion. Using coal gasification to produce hydrogen, the equipment cost accounts for the main part of the investment. Underground coal gasification method has been paid attention to in recent decades. Underground gasification technology includes coal.
High resource utilization rate, reducing or avoiding damage to the surface environment. China University of Mining and Technology has developed and improved "long passage and big interruption".
A new process of producing water gas by two-stage underground coal gasification on the ground, with hydrogen content above 50%. It has been put into industrial trial operation in Tangshan Liu Zhuang, with a daily output of 50,000 m3 of water gas. If it is purified by conversion and pressure swing adsorption, it can produce cheap hydrogen, which has certain development prospects in China. China has a good foundation in mastering the technology of hydrogen production from coal, especially a large number of hydrogen production devices in small and medium-sized synthetic ammonia plants are spread all over the country, creating conditions for providing hydrogen sources in the future. China's self-developed process of underground gasification of coal to produce water gas to obtain cheap hydrogen has been realized.
The phased results have development prospects and deserve attention.
(2) Hydrogen production from natural gas or light oil.
In this method, in the presence of a catalyst, hydrogen is generated by reaction and conversion with steam. The following reactions mainly occur:
CH4+H2O→CO+H2
Carbon monoxide +H2O→ carbon dioxide+Hz
CnH2h+2+Nh2O→nCO+(Zh+l)HZ
The reaction is carried out at 800-820℃. As can be seen from the above reaction, part of hydrogen comes from water vapor. The gas group obtained by this method
In China, the hydrogen content can reach 74% (volume ratio), and its production cost mainly depends on the price of raw materials. In China, the price of light oil is high and the cost of gas production is high, so its application is limited. Most large-scale synthetic ammonia and methanol plants use natural gas as raw material to catalyze steam conversion to produce hydrogen. China has done a lot of fruitful research work in this field and built a large number of industrial production devices. In China, an intermittent steam reforming process of natural gas was developed to produce raw materials for small ammonia plants. The method does not need to adopt a high-temperature alloy converter, and the equipment investment cost is low. The process of hydrogen production from petroleum and natural gas is very mature, but it is mainly used to prepare chemical raw materials due to the limitation of raw materials.
Materials.
(3) Using heavy oil as raw material, hydrogen is prepared by partial oxidation.
Heavy oil raw materials include atmospheric and vacuum residue and fuel oil after deep processing of petroleum. Heavy oil reacts with water vapor and oxygen to produce hydrogen.
Gas products. Partial heavy oil combustion provides heat and a certain reaction temperature for the endothermic reaction of conversion. The cost of the hydrogen product produced by this method
The cost of raw materials accounts for about one third, while the price of heavy oil is low, so people pay attention to it. China has built a large-scale hydrogen production plant by partial oxidation of heavy oil to produce hydrogen raw materials.
1.3 Hydrogen production from biomass
Biomass is rich in resources and is an important renewable energy. Biomass can produce hydrogen through gasification and microorganism.
(1) Hydrogen production from biomass gasification
Biomass raw materials such as firewood, wheat straw and rice straw. Is pressed and shaped, and then gasified or cracked in a gasifier (or cracking furnace) to produce hydrogen-containing fuel. China has made some achievements in the research of biomass gasification technology. In foreign countries, 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 also been greatly improved.
(2) Hydrogen production by microorganisms
Microbial hydrogen production technology has also attracted people's attention. Hydrogen can be produced by enzymatic reaction of microorganisms at normal temperature and pressure. biomass
Hydrogen-producing microorganisms mainly include chemotactic microorganisms and photosynthetic microorganisms. Belonging to chemotrophic microorganisms are various fermentation types.
Some strict anaerobic bacteria and facultative anaerobic bacteria ferment microorganisms, and the substrates that initially release hydrogen are various carbohydrates, protein, etc. Currently available
Patent of hydrogen production by carbohydrate fermentation, and the generated hydrogen is used as energy for power generation. Photosynthetic microorganisms such as microalgae and
The process of hydrogen production by photosynthetic bacteria is related to photosynthesis and is called photosynthetic hydrogen production.
1.4 Hydrogen production from other hydrogen-producing substances
Hydrogen production from hydrogen sulfide has been studied abroad. China is rich in H25 resources. For example, the natural gas extracted from Zhaolanzhuang oil and gas field in Hebei Province contains more than 90% H, with a reserve of tens of millions of tons, which is a valuable resource. There are many ways to produce hydrogen from hydrogen sulfide. In the 1990s, China carried out various researches, and all kinds of research results will provide valuable resources and clean energy for the future.
Lay the foundation of chemical raw materials.