Phosphorous Chemical Industry Going High-End, Coupled & Clean

By Wang Di, National Chemical Energy Saving & Emission Reduction Centre

Major products in the phosphorus chemical industry

Phosphate fertilizers

China’s capacity and output of phosphate fertilizers have increased rapidly, reaching 23.70 million t/a (based on P2O5) and 17.95 million tons respectively in 2015. With injudicious capacity growth, apparent consumption has declined steadily, being 6.8% lower YoY in 2015. Oversupply is 144%, and the overall capacity is in serious surplus. There are 215 producers of phosphate compound fertilizers in China. Competition is extremely fierce, profit rates are down, the number of money-losing enterprises has peaked and outright failure, mergers and acquisitions are frequent.
With impacts from the policy for “zero growth of chemical fertilizers use”, capacity reduction in the phosphate fertilizer sector has become inevitable. Capacity growth will be slow or even negative, so enterprises should strengthen product R&D, highlight multi-element, functional and ecological compound phosphate fertilizers (including NPK and slow/controlled-release fertilizers), and develop compound phosphate fertilizers with medium or low concentration (including medium or micro-element fertilizers) and nitro-phosphate fertilizers. At the same time, efforts should be made to strength technical renovation, industrial upgrades, energy conservation and consumption reduction, raise the level of technology and equipment, improve the quality of existing ammonium phosphate products and reduce production costs. Cascade utilization of wet-process phosphoric acid should be conducted well. Phosphoric acid classified by purification degrees should be utilized to reduce the purification cost of wet-process phosphoric acid and move towards high-end and refined products with high added value. Water-soluble phosphate fertilizers such as industrial-grade mono-ammonium phosphate should be developed.

Yellow phosphorus

Yellow phosphorus capacity is in serious surplus, with capacity utilization of only 40%. Through M&As and elimination of outdated capacity, the number of yellow phosphorus producers is already much lower than before. Through technical renovation and equipment upgrades, single-furnace production scale and capacity concentration have both increased constantly. Export of yellow phosphorus has declined year by year, coming down from 36 kt in 2010 to 10 kt in 2015. The trend will continue. Owing to an increase in demand from hot-process phosphoric acid and phosphorus trichloride firms, however, demand for yellow phosphorus will be stable with some increase. The proportion of yellow phosphorus “hidden” export (in the form of downstream products) will remain around 50%.
Strict capacity control will be essential to the future success of the sector. Yellow phosphorus producers should unfold restructuring, conduct M&As, combine the wet process with the hot process, pursue technical upgrades and renovation in major facilities and equipment, use byproduct resources well and recycle waste heat and waste energy so as to reduce production costs and enhance competitiveness.

Phosphoric acid

Phosphoric acid capacity in China reached 3.80 million t/a in 2015, output was 2.70 million tons and apparent consumption was 2.15 million tons. Capacity surplus has become a problem in the sector – utilization is around 70%. Product prices are sliding in recent years, and profitability has narrowed.

Feed-grade calcium phosphate

There are numerous producers of feed-grade calcium phosphate in China. Major production units are distributed in regions rich with phosphate rock resources such as Sichuan and Yunnan. The main process used in production is wet-process phosphoric acid. Feed-grade calcium phosphate capacity is in serious surplus today and the operating rate of production units is only around 50%. Product prices are stable, and enterprises earn narrow profits.
Calcium monohydrogen phosphate is the variety of feed-grade calcium phosphate with the highest capacity and output in China. Output reached around 2.50 million tons in 2015. Capacity growth will slow down in the future. Producers in Yunnan enjoy a quite high profit margin today, owing to their advantage in phosphate rock resources. Calcium dihydrogen phosphate is used mainly in making aquatic products and livestock products. Its demand is highly seasonal (quite high during May-October). Around 30% of output is exported. Mono-calcium and di-calcium phosphate (MDCP), as a product, is still at the initial stage in China. Its biological properties are superior to those of calcium monohydrogen phosphate, so it has bright development prospects, with annual demand growth likely to exceed 10%. Production of defluorinated calcium trihydrogen phosphate requires quite a high grade of phosphate rock. Due to factors in raw materials, process technology and application development, no large-scale commercial production has yet been established in China.
The output values of the fish, poultry and livestock breeding sectors in China are increasing rapidly, so demand for feed-grade calcium phosphate will rise further.

Other basic phosphates and phosphides

Products processed from yellow phosphorus in China are still quite undifferentiated. Products are mainly large-volume and basic, and the proportion of varieties with high added value is rather low. Capacity to make phosphates and phosphides has reached 15.00 million t/a. There are around 100 product varieties, and output is around 8.00 million tons. Some large-volume varieties of phosphates are produced in large scale. Due to surplus capacity, low operating rates and saturation of the domestic market, market balance depends on export.
Most phosphorus trichloride producers have matched downstream units. Eighty percent of them are distributed in East China. China consumes over 60% the world’s phosphorus trichloride output. More than 70% of phosphorus trichloride is used in making pesticides such as glyphosate and glufosinate-ammonium. Other applications include the manufacture of flame-retarding agents such as TEP and TCPP.
Due to policies forbidding the use of phosphorus, the consumption of sodium tripolyphosphate in making detergent builders has declined gradually, so development is in recession.
The use of ammonium polyphosphate in water-soluble fertilizers is just beginning in China. The average annual growth of demand is expected to be 16.3% in the next five years. The market for ammonium polyphosphate used in making flame-retarding agents and ammonium polyphosphate used in making water-soluble fertilizers has bright development prospects.

Fine and specialty chemicals

Production of hypophosphites and phosphites has just started in China. Production is now mostly intermittent. Consumption has already built to a certain scale. The export volume is quite small.

Orientations of clean production development in the phosphorus chemical industry

Comprehensive utilization of phosphogypsum

The amount of phosphogypsum produced in China is around 65 million tons (dry base) a year, and the total stacking amount is 250-350 million tons. Phosphogypsum has the potential to pollute surface water and underground water. With growing output amount, treatment of phosphogypsum has become imperative. Comprehensive utilization of phosphogypsum is only around 10 million tons a year, and the comprehensive utilization rate is less than 20%.
The main high value-add technologies for making sulfuric acid from phosphogypsum include the technology developed by Lubei Chemical Co., Ltd., which uses coke reduction, and the technology developed by Sichuan University, which uses sulfur decomposition. Research institutions in China including Tsinghua University are researching conversion of industrial-grade phosphogypsum into gypsums with high purity and super fineness, gypsum whiskers with high length/diameter ratio and PVC composites.

Utilization of medium or low-grade phosphate rock

Phosphorus is a non-renewable resource. So availability of phosphate rock resources determines the development prospects of phosphate fertilizers and compound fertilizers. Rational utilization of medium and low-grade phosphate rock is obviously very significant. Enterprises should use phosphate rock in the wet-process production and the hot-process production according to its different categories and qualities. Also, technologies for removing impurities from phosphate rock through floatation and chemical reactions should be developed, such as the removal of magnesium through floatation, removal of magnesium through chemical reaction and removal of silicon through floatation.

Utilization of accompanying resources such as fluorine and silicon

Within phosphate rock are lots of accompanying resources, like fluorine and silicon, minerals that also have high economic value. Phosphate rock can be decomposed by acid to get fluorosilicic acid, which is then used as raw material to get products with stable excellent quality and high cost advantage (through a series of chemical processes such as hydrogen fluoride and its series of products), silica white and its series of products and a series of products intensively processed from silicon tetrafluoride.

Effective utilization of calcium resources generated in the production of feed-grade calcium phosphate

Calcium has to be added in the production of calcium dihydrogen phosphate and calcium monohydrogen phosphate. The calcium that is contained in phosphate rock, however, becomes solid waste in the form of phosphogypsum, potentially polluting the environment, and sulfur and calcium resources are wasted. The wet-process phosphoric acid production process for feed-grade phosphates should be optimized. Calcium resources contained in fluorapatite should be fully used to reduce the consumption of lime. Phosphogypsum can also be used to produce sulfuric acid to recycle sulfur and calcium.

Utilization of yellow phosphorus furnace gas

Yellow phosphorus furnace tail gas contains highly toxic gases that should not be released in the environment. Such impurities may intoxicate oxo reaction catalysts. C1 chemical products such as formic acid, potassium formate, calcium formate, dimethyl oxalate, oxalic acid and formamide can be produced by purification of yellow phosphorus furnace tail gas. In this way, furnaces solely used for yellow phosphorus production can be turned into chemical production units that mainly undertake the gas production with the co-production of yellow phosphorus. Such purposes are hoped to be attained during the Thirteenth Five-Year Plan period (2016-2020).

Utilization of high-temperature yellow phosphorus furnace slag

The temperature of furnace slag discharged in the production of yellow phosphorus can reach as high as 1 300℃. Such furnace slag is a potential raw material for making glass ceramics and insulating cotton. Technical problems needing solution today include the silicon/calcium ratio.
Shortening production process flows is a necessity in the green development of the chemical industry. Research advances related to the phosphorus chemical industry include direct production of industrial phosphates (sodium and potassium) with co-production of ammonium chloride through wet-process phosphoric acid extraction, the removal of cationic ions by wet-process phosphoric acid, direct production of multi-element compound phosphate fertilizers from medium or low-grade phosphate rock, production of special compound fertilizers from phosphate rock through mixed acid decomposition, direct production of phosphates from phosphorus pentoxide at a temperature of around 600℃ after the recovery of heat energy generated in yellow phosphorus combustion, direct production of high-purity electronic-grade phosphoric acid through yellow phosphorus combustion, efficient purification of yellow phosphorus furnace outlet gas, removal of furnace gas dust and elimination of the yellow phosphorus bleaching section. They also include optimization of production processes, reduction of the process heat energy consumption, reduction of the per-unit-product water consumption, reduction of water treatment costs and reduction of production costs.
The phosphorus chemical industry will still has a brilliant future during the Thirteenth Five-Year Plan period. Compound phosphate fertilizers will be taken as the basis and fine phosphorus chemicals will be taken as the lead to strengthen the diversified development of the phosphorus chemical industry coupled with the coal chemical industry, the chlor-alkali industry and the materials chemical industry.