biomass gasification process

Biomass energy is an ideal renewable energy source. Biomass energy is getting more and more attention from countries all over the world because of its wide distribution and beneficial to the environment. Biomass gasification technology is a way to utilize biomass energy, which is a variety of organisms produced by photosynthesis, which uses carbon dioxide in the air and water in the soil to convert absorbed solar energy into carbohydrates and oxygen. Biomass usually includes several types of agricultural waste, wood and forest industrial waste, livestock manure, urban household waste, and energy crops. Biomass has the following characteristics: it is a renewable energy source, which can ensure the perpetual use of energy; it has many types and wide distribution, which is easy to be used locally and in various forms; the relevant technology has matured and can be stored well; energy saving and environmental protection are good.

What is biomass gasification?

Biomass gasification is the process of converting biomass fuels into gas through thermochemical reactions at high temperatures using air, oxygen-rich air, oxygen, air and water vapor, and oxygen and water vapor as gasification agents. Biomass gasification process can convert solid biomass fuel into easy-to-use gaseous fuel or synthetic raw gas, so that the chemical energy of the fuel can be transferred to gas with a conversion efficiency of 70%-90%, thus it is a high-efficiency conversion method. The biomass conversion process is a combination of many reactions such as pyrolysis, oxidation, reduction, and conversion with complex reaction routes.

Principle of biomass gasification

In order to provide the thermodynamic conditions for the reaction, the gasification process requires a supply of air or oxygen to allow partial combustion of the raw material, retaining as much energy as possible in the combustible gas obtained after the reaction. The product of gasification contains combustible gases such as H2, CO and low molecular CmHn.

The whole process of biomass gasification can be divided into: drying, pyrolysis, oxidation and reduction.

• The uppermost layer of the gasifier is the drying zone, where the materials added from above directly enter the drying zone, and the materials exchange heat with the hot gas products generated from the three reaction zones below, so that the moisture in the raw materials evaporates out, and the temperature of the layer is 100~300℃. The product of the drying layer is dry material and water vapor, the water vapor is discharged from the gasifier with the heat generated from the following three reaction zones, while the dry material falls into the pyrolysis zone.

• Pyrolysis layer: The dry biological material runs downward into the pyrolysis layer, while heating the biomass, and when the biomass is heated, pyrolysis reaction occurs. Through the pyrolysis reaction most of the volatile fraction in the biomass is separated from the solid, which is basically completed at 500~600℃, leaving charcoal. The main products of pyrolysis zone are charcoal, hydrogen, water vapor, carbon monoxide, carbon dioxide, Tianane, tar and other hydrocarbon substances, etc.

• Oxidation layer: The remaining charcoal of pyrolysis reacts violently with air and releases a large amount of heat. Since it is oxygen-limited combustion, the supply of oxygen is not sufficient, thus incomplete combustion reaction occurs simultaneously, generating carbon monoxide and releasing heat at the same time. In the oxidation zone, the temperature can reach 1000 ℃, in the oxidation zone are combustion reactions, and release heat, but also this part of the reaction heat for the reduction zone of the reduction reaction. Cracking and drying of materials, providing a heat source. In the oxidation zone generated in the hot gas (carbon monoxide and carbon dioxide) into the reduction zone of the gasifier, ash falls into the lower ash chamber.
  
• Reduction layer: In the reduction zone there is no longer oxygen present, and the carbon dioxide generated in the oxidation reaction reacts here with carbon and water vapor to produce carbon monoxide (CO) and hydrogen gas (H2). Since the reduction reaction is a heat-absorbing reaction, the temperature of the reduction zone is reduced accordingly. The main products of the reduction zone are carbon monoxide (CO), carbon dioxide (CO2) and hydrogen (H2) at about 600-800°C. Gasification is practically always combined with a dry cracking process of the fuel. In actual operation, there is no clear boundary between the above four zones. They are interpenetrated and interleaved. So at the exit of the gasifier, the output gas composition is mainly carbon monoxide (CO), carbon dioxide (CO2), hydrogen (H2), methane (CH4), tar and a small amount of co-other hydrocarbons, as well as water vapor and a small amount of ash.

Advantages of biomass gasification

Gasification technology has a history of 150 years and has been widely used in the chemical and petrochemical industry worldwide since its inception. Due to its unique chemical process and environmentally friendly properties, it is widely used in various industries, and Haiqi was one of the first pioneers.

What are the advantages of this biomass gasification technology compared to the traditional combustion technology? 

In fact, biomass gasification technology is a sublimation technology of people’s direct combustion technology, a manifestation of people’s refinement of energy application, because biomass gasification is a kind of multi-production technology, through biomass pyrolysis gasification reaction can get several products at the same time, such as gas, biomass carbon, wood vinegar liquid, wood tar.

• Environmental advantages.

In recent years, the state has made great efforts to control the environment, especially air pollution, and the main pollutants under control are: particulate matter, nitrogen oxides, sulfide, carbon monoxide and soot blackness.

Biomass pyrolysis gasification technology has certain advantages for the control of these pollutants, the technology belongs to the oxygen-deficient layer combustion technology, the reaction is slow, and the concentration of particulate matter in the generated gas is much less compared to direct combustion, which can reach 50mg/m³ without the addition of dust collector. The calorific value of biomass gas produced by this gasification technology is relatively low, and the combustion temperature is also lower than that of direct combustion, which plays a good inhibiting role in the control of NOx, because NOx is mainly produced under high temperature and large peroxide coefficient, and generally NOx can be controlled within 150mg/m³ without adding denitrification devices. 

As a biomass energy source, sulfide generally does not exceed the standard, because similar to wood chips, straw and other biomass fuels have very little sulfur, and the sulfide produced after combustion is naturally less, generally at 30mg/m³, which can fully meet the national control standards. As long as the combustion is sufficient, the two indicators of carbon monoxide and soot blackness are within the control of the national standard.

• Economic advantages

The economic advantage of biomass pyrolysis gasification technology is also obvious, because the products produced in the gasification process can become commodities or be further processed into commodities with higher added value.

For example, one ton of wood chips (market price 500 yuan) can produce gas with about 70% heat energy through pyrolysis gasification, with a calorific value of about 2.8 million calories, which is equivalent to the calorific value of 330m³ natural gas (market price about 1000 yuan); it can also produce charcoal with a weight ratio of about 20-25%, i.e. at least 200kg of charcoal (market price about 300 yuan); produce dilute wood vinegar liquid of about 1 5%, i.e. 150kg (market price about 90 yuan); produce wood coke (market price about 90 yuan); produce wood tar weight ratio of about 5%, that is, there are about 50 kg, (market price about 30 yuan); the direct benefit of these products will be 1420 yuan, excluding the cost of fuel, a ton of wood chips can produce 920 yuan of net benefit. 

If these products are deeply processed, the added value can also rise several times, for example, using charcoal can make activated carbon or charcoal-based fertilizer, etc. The added value can be more than doubled.

Biomass gasification process

Application areas for biomass gasification

• Wood tar: The main component of wood tar is creosote, which is usually produced by distilling tar made from non-fat filled wood, treating it with sodium hydroxide, re-acidifying it and re-distilling it to separate it from other components.

*Wood tar can be used as medicine, as expectorant, anti-infective, astringent, anesthetic and laxative, etc.

*Waterproofing of ship hull, waterproofing layer of roof, wood preservative.

*Wood tar is dehydrated and made into solid fuel.

*Converting wood tar into biomass oil by distillation.

*Wood tar can be used as boiler fuel.

*Wood tar can be used for meat preservation.

• Wood vinegar liquid: Wood vinegar liquid, also called vegetable acid, is the substance obtained from the smoke produced in the process of making charcoal after collecting, cooling and liquefying. The crude wood vinegar liquid, after being placed for a month, is divided into three layers, which are yellow, reddish-brown and with transparent wood vinegar liquid.

Biomass Gasification for Hydrogen System

Hydrogen is a widely used gas, not only as a chemical feedstock, fuel or energy carrier, but also in many applications in the industrial, transportation and power sectors. Its use does not cause any direct greenhouse gas emissions and offers the possibility of zero air pollution compared to concentrated and distributed fossil fuel combustion, making it a recognized clean energy source. In the face of today’s environmental and energy problems, hydrogen is being used in new ways in more areas, such as fuel cells, which have pushed the use of hydrogen to new heights, especially hydrogen fuel cell vehicles are the most representative. With the rapid development of new energy sources such as wind power and photovoltaic, green hydrogen technology has become the focus of attention nowadays, and its development and utilization can help solve the energy crisis and environmental pollution problems, and play an important role in the road to carbon neutrality for all countries.

• biomass gasification polygeneration system for hydrogen production can produce natural biochar, wood tar, wood vinegar liquor and other natural high value-added by-products. The biomass gas produced can be used to extract H2, CH4, CO, and the heat and electricity produced can be used for industrial or residential purposes.
• biomass gasification hydrogen system has a general payback period of about 3~4 years, which is a very economical project.
• biomass gasification polygeneration system for hydrogen production adopts 5G smart energy management system, which can remotely monitor the system usage conditions using PC or mobile terminal. The smart energy cloud system can share system data to the cloud for 20 years.
• biomass gasification polygeneration system adopts multi-point joint collection of control information and ensures the safe and stable operation of the system through smart valves and multi-point sensors.
• biomass gasification system can be operated by only 2 people on duty, which greatly saves labor operation cost.
• polygeneration system for hydrogen body adopts more than 60% alloy stainless steel corrosion resistant material to ensure the service life and high quality working condition of the system.
• Biomass gasification system adopts frame structure for the whole output, which saves more than 50% of the total EPC project volume.
• Biomass gasification system can provide personalized customization service according to the actual needs of customers.
• The energy utilization rate of biomass gasification multi-generation system reaches more than 90%, and truly achieves zero emission through the cooperation between energy sources.
• The thermal energy generated in the biomass gasification system is centrally transformed to provide the energy utilization level of the whole system and ensure the safety and reliability of the system.
• In addition to the extractable gas, the system produces other combustible gases that can be used to produce heat and electricity, ensuring high utilization rate of energy.
  

Biomass gasification cogeneration system

Biomass gasification cogeneration technology, also known as “biomass cracking gasification (heat, electricity, carbon) cogeneration technology, its core technology is biomass gasification technology. The core technology is biomass gasification technology. The main types of technology are up-suction fluidized bed technology and down-suction fixed bed gasification technology, among which the principle of down-suction fixed bed gasification technology is to convert the “volatile carbon” part of biomass into “combustible gas” through biomass pyrolysis gasification, and the “fixed carbon” part is retained. The “fixed carbon” part is retained to produce carbons, which are eventually returned to the land, thus reducing the emission of carbon in the atmosphere. Biomass pyrolysis gas will be mainly used as the power core of distributed multi-generation energy stations in the future, and has a greater potential for development, replacing natural gas, coal, oil and other non-renewable energy sources, providing heating, heating or power generation for a wider range of applications.

• Biomass gasification multi-generation can be left unattended for 20 hours.
• System interconnection and interlock, high security, one key start/stop, strong stability.
• 5G remote intelligent energy management system, which can remotely manage the energy system and facilitate supervision.
• The normal operation of biomass gasification multi-generation system requires only one person to be on duty, which is a small workload and suitable for long-term use.
• High security, in case of emergency, it will automatically shut down, eliminate hidden dangers and wait for engineers to rescue.
• Biomass gasification multi-generation is made of about 30% more stainless steel material, with a design life of 20 years.
• The brands of electrical appliances used in the biomass gasification system are all well-known European brands, and the motors are all first-line Chinese brands.
• The gasification multi-generation system is all built with modular steel structure, which reduces the civil construction cost and increases the service life.
• The generator sets are all first-line brands in China, which can achieve 8000 hours/year of power generation.
• The cooling water heat energy of gasification system is used for raw material drying.
• The thermal energy of the generator set is used to produce hot water or steam.
• No excess energy is wasted in the whole system, all of it is recycled and used, which improves the overall efficiency of the system.
• Biochar, wood tar and wood vinegar liquor can be used for secondary purification to improve the added value of products.
• The modular design of the system makes the installation of equipment easier.
• The system space utilization is bigger, which improves the use space of the site.
• The use site is clean and tidy, with no pollutants and odor on the ground.
• Reduce redundant supporting equipment, reduce the overall energy consumption and investment of the system