In all, the present situation of steel industry develops well, but institutes and experts in China hold different opinions on steel's futures for this industry is under many factors, such as raw material price, policy, environment, international trade barrier, down-stream product, macroeconomy. No matter what the situation is, many companies want to grasp this chance to control the capacity, equivalent substitution and close down the outdated production, so quite a lot companies focus their attention on the technology that could enlarge the production capacity, among which increasing oxygen enrichment rate is an efficient way. In 2017, many steel company enlarged their oxygen capacity and invest to build large oxygen plants. One of the efficient and popular oxygen generating methods is VPSA oxygen technology.
According to Beijing Peking University Pioneer Technology Company (Professional supplier of VPSA equipment in China), VPSA oxygen technology separates oxygen from nitrogen by the adsorbent, and there is no by-product except oxygen, and the oxygen enriched will be used before blower. Compared with cryogenic method, VPSA has many advantages, such as oxygen production cost is lower, plant construction period is shorter, flexible turn down, easy operation, which meets the needs of enlarging capacity.
Firstly, the operation cost of VPSA is low. The power consumption rate is 0.32kwh to 0.35kwh producing one cubic pure oxygen. If the power cost 0.5rmb per kwh, the operation cost of VPSA is 0.15rmb. Considering the depreciation cost, labor cost and maintenance cost, the cost of producing one cubic oxygen is under 0.3 rmb.
Secondly, the construction period is short. From civil construction to installation, and then to test run, it cost 6 months to get oxygen. In recent years, steel company prefers such short construction period, which can bring benefit quickly. The earning will be very sizable if the oxygen plant starts to , based on the price of steel now.
Thirdly, flexible turn down. VPSA oxygen plant can enlarge the steel plant’s oxygen capacity, the redundant oxygen can be fed to steel making system if oxygen is enough for blast furnace. Additionally, if the steel situation goes down in future, VPSA plant could adjust its turn down ration to save more cost.
Fourthly, easy operation. VPSA plant works under automatic control system, which only needs 6-8 workers, also professionalism is not required. So it is easy to add them into human resource system and don’t cause trouble to the company.
The following data are collected from a VPSA oxygen plant in a steel company as a reference.
There are three blast furnaces in this steel company, 3200m3, 2500m3 and 1080m3. The oxygen enrichment rate goes up by 1%, the capacity goes up 4.76% by theory, 3-4% in reality. Also the coal is also increased by 12-13kg/t, and coke ration decreased by 0.5%. The oxygen enrichment rate goes by 1%, the heat value increases by 3.4%, and off gas of blast furnace is easier for combustion. Upon the current situation of this company, it is to increase the oxygen enrichment ratio to 4.4% from 3.5%, relatively the oxygen flow to 49000Nm3/h from 39000Nm3/h, namely the pure oxygen increases by 10000Nm3/h.
If iron producing ratio is increased to 3%, the total iron capacity is increased by 475t/d. Considering 350 working days a year and 700rmb benefit added per ton iron, the total benefit added will be 116.42 million rmb per year.
At the same time, cost added per year is around 20 million, so the net benefit will be 96 million rmb per year.
Compared with the cryogenic plant of the same capacity, considering the construction periods difference and oxygen producing cost difference(take 0.1rmb/m3 cost as an example), what VPSA brings to the company is 4 months shorter period and 32 million one-time benefit. That is 8.4 million rmb is saved per year.
Above all, oxygen enriched coal spray is one of the efficient way for energy saving, coke saving and capacity enlarging. enriched oxygen can also promote the use of blast furnace gas, and rich oxygen combustion technology can make up for the shortcomings of the low calorific value of blast furnace gas and increase efficiency. If the steel company take oxygen enrichment as a key point, and equipment company with VPSA oxygen system, by oxygen enriched coal spray, the iron production capacity will be enlarged and sizeable benefits will be earned.