Issue 40/2015 - Continuous catalytic oxidative dephosphorization process solves the technical problem of yellow phosphorus tail gas purification

The successful model of calcium carbide tail gas to ethylene glycol process route has rich reference significance for yellow phosphorus enterprises, but the problem of yellow phosphorus tail gas purification makes it impossible for the two to marry
.
The continuous catalytic oxidative dephosphorization process developed by Beijing Peking University Pioneer Technology Co.
, Ltd.
is expected to solve the technical problems
of yellow phosphorus tail gas purification.

The utilization of yellow phosphorus tail gas needs to remove impurities
such as fluorine, arsenic, phosphorus and sulfur.
Among them, the removal of fluorine, arsenic and sulfur has a relatively mature process, so the technical difficulty of yellow phosphorus tail gas purification is phosphorus
removal.
At present, enterprises generally use three methods
to purify yellow phosphorus tail gas: water washing and alkali washing, variable temperature adsorption method and discontinuous catalytic oxidation method.
However, these three methods have problems in industrial operation: the water washing and alkali washing method will react with alkali to generate phosphine during the alkali washing process, so the purpose of effective phosphorus removal cannot be achieved, and a large amount of waste lye will be discharged; The variable temperature adsorption process is more complicated, and improper treatment of impurities such as phosphorus desorption may cause secondary pollution; Dephosphorization by discontinuous catalytic oxidation is an intermittent operation, which requires multi-tower switching operation, and the adsorption saturated catalyst needs to be regenerated
.

In view of the fact that the current methods cannot be effectively operated, Peking University Pioneer is committed to overcoming the problem
of yellow phosphorus tail gas dephosphorization.
If this research is successful, it is likely to push the high value-added utilization of yellow phosphorus tail gas to a new stage
.

The principle of the continuous catalytic oxidative dephosphorization process developed by Peking University Pioneer is to carry out a catalytic reaction of yellow phosphorus tail gas after filtration and pressurization, and the phosphorus oxides generated are transferred out of the bed in gaseous form after desorption from the catalyst surface, and the catalyst does not need to be regenerated, so that the yellow phosphorus tail gas purification reaction can be carried out
continuously.
The process has few operating units and simple processes, which reduces the complexity of equipment and operation, so it can greatly reduce investment and energy consumption, which is conducive to reducing the long-term operating cost
of equipment for yellow phosphorus enterprises.

The key to continuous catalytic oxidation of this process lies in the catalyst
.
Compared with the traditional dephosphorization method, the catalyst developed by Peking University Pioneer has three outstanding innovation advantages
.

First, ordinary phosphorus removal catalysts need to be regenerated repeatedly, and after a period of time, the catalyst will fail, and the new catalyst must be refilled before the device can continue to operate
.
The new catalyst developed by Peking University Pioneer does not need to be regenerated during the continuous dephosphorization reaction, which effectively solves many problems
existing in the traditional discontinuous dephosphorization technology.

Second, unlike any previous purification process of yellow phosphorus tail gas, the new catalyst developed by Peking University Pioneer has good sulfur resistance, and the total sulfur content in yellow phosphorus tail gas does not change significantly before and after removing phosphorus impurities, and does not affect the continuous phosphorus removal performance
of the catalyst.
Therefore, the continuous phosphorus removal process of Peking University Pioneer can first remove total phosphorus in the purification of yellow phosphorus
tail gas.
In the next step, enterprises can flexibly choose the desulfurization method and the depth
of desulfurization according to the utilization of yellow phosphorus tail gas.
For example, when using yellow phosphorus tail gas for power generation, coal is required as an auxiliary fuel
.
The total sulfur in the yellow phosphorus tail gas and the sulfur in the coal are burned to generate sulfur dioxide, and for the boiler, there is no need to remove hydrogen sulfide, so the sulfur in the tail gas can be removed simultaneously with the sulfur in the coal, cleverly simplifying a process
.

Third, the new catalyst has stable performance, which can ensure the long-term operation of the equipment, and it is conservatively estimated that it can be used continuously for 3 to 5 years, ensuring that yellow phosphorus enterprises can supply purified tail gas
to downstream processes for a long time and stably.

In October 2014, the process completed a pilot test
in a phosphorus power company in Yunnan.
The continuous operation time of the device is one and a half years, and the total amount of exhaust gas purified is 1.
2 million cubic meters
.
The total phosphorus content of the purified exhaust gas is reduced from 1200~1500mg/m3 before purification to below 1mg/m3 (about 0.
7×10-6), that is, the goal of "controlling the total phosphorus below 1×10-6" is achieved, which can meet the requirements of raw gas for power generation and chemical synthesis, and there is no other form of "three wastes" discharge
in the whole process.

According to the operation data of the pilot plant, if the scale of yellow phosphorus tail gas volume is 20,000 cubic meters per hour as the standard, the initial investment of continuous catalytic oxidation and phosphorus removal process is about 20 million yuan, and the operating cost per cubic meter of tail gas treatment is about 0.
08 yuan (including depreciation), and the investment and operation cost of the device are lower than the cost
of discontinuous oxidation adsorption phosphorus removal and variable temperature adsorption phosphorus removal.

At present, yellow phosphorus enterprises have paid great attention to this purification process, and Peking University Pioneer is expected to start construction of the first industrial plant
in the near future.

(The author is Jiang Hua, director of the R&D Center of Beijing Peking University Pioneer Technology Co.
, Ltd.
, Ph.
D.
in physical chemistry of Peking University, engaged in the research and development of gas separation and purification technology for more than ten years, and has rich experience
in the field of gas separation technology.
) (towards)