Promote liquid nitrogen fertilizer first to solve the transportation problem

At present, the energy consumption of China's nitrogen fertilizer industry is very high. In 2010, the energy consumption of the nitrogen fertilizer industry was: 85.345 million tons of coal, 11.13 billion cubic meters of natural gas, and 68.6 billion kWh of electricity, accounting for 2.6%, 11.5%, and 1.6% of the total consumption respectively. How to increase nitrogen fertilizer production and save energy? Hongchang Liquid Ammonia Manufacturer believes that promoting liquid nitrogen fertilizer is a feasible solution.

However, domestic fertilizers are all solid circulation, that is, railway transportation, mainly in bags. If liquid nitrogen fertilizer is to be used, a comprehensive tanker transportation system must be available. Industry insiders said that this is a major problem that needs to be solved in the promotion of liquid nitrogen fertilizer.

Liquid nitrogen fertilizer: energy saving and emission reduction

It is reported that using liquid nitrogen fertilizer directly as fertilizer can find a way out for companies with surplus ammonia. According to Xue Yuan, director of the production technology department of PetroChina Urumqi Petrochemical Company, at present, enterprises that use natural gas as raw materials and adopt steam reforming process to produce synthetic ammonia/urea will produce a large amount of surplus ammonia due to the imbalance between ammonia and carbon dioxide. A synthetic ammonia unit with an annual output of 300,000 tons has an annual surplus of about 15,000 tons of ammonia.

According to this estimate, the total amount of ammonia surplus of nitrogen fertilizer enterprises is about 200,000 tons per year. There are three enterprises in Xinjiang alone with surplus ammonia. Among them, the two synthetic ammonia units of Zepu Petrochemical Plant produce 40 tons of liquid ammonia every day. Since Zepu Petrochemical Plant is located in an underdeveloped area, this part of liquid ammonia has no market and can only be vented in the form of relaxation gas. Industry insiders pointed out that if this part of liquid ammonia is used as fertilizer, based on the calculation of applying 30 kilograms of liquid ammonia per mu, the annual surplus ammonia can be used for fertilizing 6.667 million mu of large-scale fields.

Another advantage of liquid nitrogen fertilizer is that it can increase fertilizer efficiency. Studies have shown that liquid ammonia is randomly applied to the soil by tilling the soil, forming a fertilization belt with a concentric circle of 150 mm centered on the ammonia spray hole. It can be quickly absorbed and fixed by the soil, and activate the phosphorus and potassium elements in the soil. The nitrogen, phosphorus and potassium absorption of the plants is higher than that of solid nitrogen fertilizers. It has been determined that the nitrogen utilization rate can be increased by 5%.

According to the Standing Committee of the Economic and Technical Committee of the former Ministry of Chemical Industry and the head of the Fertilizer Group, all the countries with developed agriculture in the world have adopted liquid nitrogen fertilizers. For example, in the past 50 years, Midea's nitrogen fertilizer varieties have been dominated by liquid nitrogen fertilizers, accounting for 60-65.63% of the total nitrogen fertilizers.

Traditional liquid ammonia: many problems in application, storage and transportation

It is understood that liquid nitrogen fertilizers are mainly divided into two categories, among which liquid ammonia is the most widely used. The so-called liquid ammonia refers to liquid ammonia obtained by pressurizing or cooling gaseous ammonia. This liquid nitrogen fertilizer eliminates the energy-consuming process of concentration and crystallization of ordinary nitrogen fertilizers. Therefore, liquid ammonia has better energy-saving effects than ordinary nitrogen fertilizers.

However, there are many shortcomings and bottlenecks in the production and use of liquid ammonia.

First, it has high technical requirements. Liang Jiajun, deputy secretary-general of the Jiangsu Fertilizer Industry Association, told reporters that liquid ammonia fertilization is common outside, but it has high technical requirements and cannot be applied too much, otherwise the seedlings will be burned. Liquid ammonia is canned from the factory into ammonia bottles and then sent to the fields, and then applied to crops. This process has high technical requirements and there is a problem of concentration control. In addition, liquid ammonia has a high pressure and cannot be loaded into normal pressure containers. It must be loaded into pressure vessels. Generally, fertilizer plants have large liquid ammonia storage tanks, filling stations at the door, and ammonia bottles filled with liquid ammonia. Ammonia bottles are then sent to various places to ensure the safe use of liquid ammonia. Liquid ammonia for agricultural use outside is transported by pipelines, but the current technical level inside is not up to the standard. Therefore, Liang Jiajun believes that I currently do not have the technical conditions for the use of liquid ammonia in agriculture, and there are many problems in management.

Second, there are safety risks. "If liquid ammonia is used for fertilization, how to transport and repack it? Liquid ammonia is toxic, belongs to hazardous chemicals, flammable and explosive, and it is not allowed to be transported without a hazardous chemical transportation certificate. In addition, how to repack liquid ammonia after it is transported by train? Train stations generally do not have repackaging equipment because it is not allowed to be built in places where people gather. This is also the reason why China cannot import synthetic ammonia."

Luoyang Hongchang Liquid Ammonia Experts believe that it is not feasible to directly use liquid ammonia for fertilization, which will burn the seedlings. In addition, liquid ammonia has pressure and certain dangers, and farmers have more problems in using it. The control of hazardous chemicals in China is very strict, and ammonia tanks will not be built everywhere, because this is equivalent to building "bombs" everywhere. Fertilizing with ammonia water has long been eliminated in China, so the practical significance of using liquid ammonia is not great.

Non-pressure nitrogen solution: There may be a future

In this case, another type of liquid nitrogen fertilizer has come to the fore. According to Li Zhijian, director of the Fertilizer Department of the Petroleum and Chemical Industry Planning Institute, in addition to liquid ammonia, another type of liquid nitrogen fertilizer that is widely used abroad, especially in the United States, is non-pressure nitrogen solution (abbreviated as UAN solution). It is an aqueous solution made by mixing unconcentrated urea and ammonium nitrate. Compared with liquid ammonia, UAN solution has its advantages.

As a type of liquid nitrogen fertilizer, the point of UAN solution is that liquid urea does not need to be evaporated and granulated, so it consumes little energy. UAN solution can be applied to the soil more evenly, and it contains nitrate nitrogen, ammonium nitrogen and amide nitrogen. The first two can be absorbed by crops more quickly, and the amide nitrogen fertilizer lags a little, making it have the functions of both fast fertilizer and delayed fertilizer, and the fertilization is uniform, so its fertilizer is higher than solid nitrogen fertilizer, and it can be injected into the irrigation system.

But he also said that there are still some obstacles to be solved in promoting UAN solution in China. For example, at present, domestic fertilizers are all solid circulation, that is, railway transportation, mainly in bags. If UAN solution is to be used, a comprehensive tanker transportation system must be used, and the cost is relatively high.