Natural gas is a high-quality fuel and chemical raw material that is used in large quantities and for a wide range of purposes. Natural gas can be made into ammonia, methanol and its processed products (formaldehyde, acetic acid, etc.), ethylene, acetylene, methylene chloride, carbon tetrachloride, carbon disulfide, nitromethane, etc. by purifying and separating it from cracking, steam reforming, oxidizing, chlorinating, sulphurizing, nitrifying, dehydrogenating and other reactions. The total world production reaches 4014 billion m3 in 2020.Hydrogen production from natural gas is one of the main sources of hydrogen. The global annual production of about 70 million tons of hydrogen, about 48% from natural gas to hydrogen, most of the European and American countries to natural gas to hydrogen. Natural gas hydrogen production technology includes natural gas steam reforming hydrogen production, methane partial oxidation hydrogen production, natural gas catalytic cracking hydrogen production and CH4/CO2 dry reforming hydrogen production and other technology routes. First, natural gas steam reforming hydrogen production principle and process flow

Principle:

The main component of natural gas is methane, the technology is to let methane and water vapor in the high temperature and catalyst under the action of heat-absorbing reaction to generate hydrogen and carbon monoxide.

Process Flow:

1. Raw material pretreatment: natural gas is first pressurized and then passed through a desulfurization reactor, where processes such as hydrodesulfurization are used to remove sulfides from the natural gas to a very low level and prevent catalyst poisoning.

2. Reforming reaction: The pretreated natural gas is mixed with water vapor in a certain proportion, and enters the preheating coil of the reforming furnace for preheating, and then enters the reforming tube of the reforming furnace, where the reforming reaction takes place under the action of nickel catalyst and so on, generating the reforming gas containing hydrogen, carbon monoxide, carbon dioxide and so on, and the temperature of the reaction is usually more than 800℃.

3. Heat Recovery and Transformation Reaction: The temperature of the reformed gas is higher after it leaves the reformer, and it first enters the steam generator to by-produce steam to recover heat, and after the temperature is lowered, the reformed gas enters the intermediate reformer, and under the action of the catalyst, the reaction between carbon monoxide and water vapor generates hydrogen and carbon dioxide, which further improves the production of hydrogen.

4. Gas Cooling and Separation: After the conversion reaction, the gas then passes through steam superheater, boiler feed water preheater, demineralized water preheater, etc. for heat recovery and cooling, and then enters into the water cooler of the conversion gas and cools down to a lower temperature, and then separates the condensate through the gas separator of the conversion gas.

5. Hydrogen purification: the cooled and separated gas enters the transformer pressure adsorption device, utilizing the difference of adsorption characteristics of different gases on the adsorbent to purify hydrogen to a higher purity, such as 99.999%, to get the product hydrogen, while the resolved gas can be further processed or recycled.

Second, the advantages and disadvantages of natural gas steam reforming hydrogen production

Advantages:

1, high technical maturity: the technology has been applied since 1926, it is the most widely used method of hydrogen production from natural gas in the current industrial application, the process is mature, stable and reliable operation.

2, large hydrogen production: the conversion rate of methane can reach 85%, which is the highest conversion rate among the natural gas reforming methods of hydrogen production, and it can produce hydrogen in large quantities, which can meet the demand for large-scale industrial hydrogen.

3, stable supply of raw materials: natural gas is one of the three major fossil energy sources on earth, with abundant reserves, relatively low price and wide distribution, providing sufficient and stable raw materials for hydrogen production.

4, relatively simple operation: the process is relatively simple, easy to control the operation, after years of development, the relevant technology and equipment has been more perfect, easy to realize industrialized production.

Disadvantages:

1, high energy cost: the reaction is a strong heat absorption reaction, requires a large number of external heat supply, usually natural gas itself as a fuel to provide heat, resulting in higher overall energy consumption, increasing the cost of hydrogen production.

2, large investment in equipment: because the reaction needs to be carried out under high temperature conditions, the high temperature and high pressure resistance of the equipment is required, so the equipment investment is large and the construction cost is high.

3、Greenhouse gases: the process of hydrogen production will produce a large amount of carbon dioxide, which has a certain impact on the environment, and needs to be supported by the corresponding carbon dioxide capture and treatment devices to reduce greenhouse gas emissions.

4、High requirements on catalyst: catalyst is needed to promote the reaction, and the catalyst is easy to be poisoned and deactivated, and needs to be replaced or regenerated periodically, which increases the operation cost and complexity of operation.

Third, natural gas steam reforming hydrogen cost analysis

1. Raw material cost:

Natural gas is the main cost components, accounting for about 70% of the total cost. If the price of natural gas for industrial and commercial use is 2.5 yuan/m³, the cost of hydrogen production is 12.57 yuan/kg; when the price is 3.5 yuan/m³, the cost of hydrogen production increases to 16.32 yuan/kg.

2, equipment investment costs:

The technology requires a variety of equipment such as conversion furnace, steam conversion device, variable pressure adsorption device, etc., and the construction investment is large. If the capacity of 90,000 m3/h of equipment, the construction investment is about 600 million yuan.

3, energy consumption costs:

The reaction is a strong heat absorption reaction, often using natural gas itself as a fuel for heating, in addition to consuming electricity for equipment operation, etc., which increases the energy cost.

4, catalyst costs:

Nickel catalysts need to be replaced or regenerated on a regular basis, which increases the operating costs and complexity, but relative to the cost of raw materials and energy, the proportion is relatively small.

5, operation and maintenance costs:

Equipment requires professional operation and maintenance, and regular maintenance, which brings a certain amount of labor costs and maintenance costs, including equipment repair, maintenance, replacement parts and other costs.

6, environmental costs:

Hydrogen production process will produce a large amount of carbon dioxide, to meet environmental requirements, carbon dioxide capture, utilization and storage technology, which will significantly increase costs.

Fourth, natural gas steam reforming hydrogen influencing factors

1, reaction temperature:

Temperature has a significant impact on the hydrogen reaction. Generally speaking, increasing the temperature can accelerate the reaction rate, methane conversion rate will also increase. For example, in the traditional steam reforming reaction, the temperature is increased from 700 ℃ to 900 ℃, the methane conversion rate may be increased from 60% to more than 90%. However, too high a temperature will increase energy consumption and may also lead to catalyst sintering and deactivation.

2. Reaction pressure:

Pressure increase is not conducive to the positive natural gas steam reforming reaction, because the reaction is a volume increase reaction. However, from the industrial production point of view, an appropriate increase in pressure is conducive to reducing the volume of equipment and reducing costs, so the relationship between the conversion rate and the cost of equipment needs to be balanced.

3, water-carbon ratio:

Water-carbon ratio is the ratio of water vapor to the amount of carbon in natural gas. Higher water to carbon ratio can inhibit the occurrence of carbon reaction, so that the methane conversion rate increased. For example, when the water-carbon ratio is increased from 2 to 4, the methane conversion rate can be significantly increased, but the water-carbon ratio is too high, which will increase energy consumption and subsequent separation costs.

4, raw gas composition:

In addition to methane, natural gas contains hydrocarbons such as ethane, propane and a small number of impurities. These impurities may lead to poisoning and deactivation of the catalyst, while the presence of other hydrocarbons will complicate the reaction process and affect the yield and purity of hydrogen.

5、Catalyst performance:

Catalyst is one of the key factors affecting the effect of hydrogen production. A catalyst with good performance can reduce the reaction activation energy and improve the reaction rate and selectivity. For example, nickel-based catalyst with high activity and low cost is widely used in natural gas steam reforming hydrogen production, but it is easy to be deactivated by sulfur poisoning.

V. Development trend of natural gas steam reforming to hydrogen

1、Technological innovation and upgrading

(1) Research and development of new catalysts: We are committed to developing catalysts with higher activity, better selectivity, better stability and better anti-poisoning ability, such as new nickel-based alloy catalysts, etc., in order to improve the reaction efficiency, reduce the reaction temperature and pressure, and reduce the energy consumption and cost.

(2) Process optimization: Improve the process of reforming reaction, such as adopting more efficient reactor design, optimizing the heat recovery system, etc., to improve energy utilization and reduce production costs.

2、Low carbonization development

(1) Coupled with carbon capture and storage technology: Combine carbon capture, utilization and storage technology to reduce carbon dioxide emissions, to achieve low-carbon or even near-zero emissions from natural gas to hydrogen production, and to produce blue hydrogen to meet the needs of low-carbon economy.

(2) Combination with renewable energy: Explore the coupling with renewable energy sources such as solar and wind, such as the use of renewable energy to generate electricity for electrolysis of water to produce hydrogen, and then combined with natural gas reforming to produce hydrogen, to improve the sustainability of the hydrogen production process and environmental friendliness.

3, miniaturization and distributed applications

(1) Research and development of small-scale hydrogen production devices: develop natural gas steam reforming hydrogen production devices suitable for small-scale and distributed applications, to meet the needs of hydrogen refueling stations, distributed energy systems and other on-site preparation of hydrogen, reduce the cost of transportation and storage risk of hydrogen.

(2) Comprehensive utilization of energy: to realize the integration of hydrogen production with heat supply, power generation and other energy services, improve the efficiency of energy utilization, and enhance the flexibility and reliability of energy supply, such as the construction of a joint system of natural gas reforming hydrogen production and fuel cell power generation.

4、Intelligent and automation control

(1) Intelligent production process: With the help of big data, Internet of Things, artificial intelligence and other technologies, real-time monitoring, optimization control and fault diagnosis of the hydrogen production process can be realized, so as to improve the production efficiency, product quality and operational safety, and to reduce the labor cost and operational risk.

(2) Energy management system integration: establish a comprehensive energy management system to collaboratively manage and optimize the scheduling of hydrogen production devices and other energy equipment, and achieve efficient allocation and utilization of energy.

5、Industry chain integration and synergistic development

(1) Strengthen upstream cooperation: establish long-term and stable cooperation with natural gas suppliers to ensure the stability and economy of raw material supply, and jointly explore the efficient development and utilization of natural gas resources.

(2) Expand downstream market: Cooperate closely with downstream users such as hydrogen fuel cell vehicle manufacturers, chemical companies, energy service providers, etc., optimize the product structure and service mode according to the market demand, and expand the application fields and market space of hydrogen.