Sulfuric acid based on sulfur

Combining advanced international technology with self-independent innovations, Allgreen has developed large-scaled sulfuric acid plants that are abreast with these developed home and abroad.

Major characteristics of Allgreen’s sulfuric acid production process

• Quick sulfur melting and mechanical filtration and purification of molten sulfur

• The introduction of double conversion, double absorption process, the selection of high quality catalyst to raise conversion rate and eliminate the pollution caused by tail-gas ensure the system excels in process parameters.

• Low temperature heat of acid recycling system produces low pressure steam, which increases the recovery rate of waste heat.

• Self developed a series of equipments: efficient sulfur burning furnace, stainless steel converter, efficient drying and absorption tower, alloy acid distributor, alloy acid cooler, sulfur pump, circulating acid pump. Selection of stable and reliable equipments suchas air blower, boiler system, molten sulfur filter, demister, which greatly enhanced the stability of the system.

• Using the corrosion-resistant alloy materials developed by XUANDA to fabricate drying and absorption tower as well as its internalpart, circulating acid tank, acid distributor, acid cooler, piping and valves to realize extension of life-time and easy maintenance. 

Low temperature heat recovery of sulfuric acid plant based on sulfur(DWHS)

The low temperature heat of the drying and absorption section of the majority of sulfuric acid plants in China is dissipated by circulating cooling water. An extra of 0.45~0.5ton of steam per ton of sulfuric acid could be generated using DWHS technology, raising the recovery rate from traditionally 60%~70% to more than 90%.

The 1st set of home-made DWHS system was built by Allgreen in 2006 followed by more systems featuring” one set shared by multiple main systems”, all of which turned out to be a success. After continuous improvement, DWHS technology of sulfuric acid plant has become mature with the following outstanding advantages:

• DWHS technologies of various process flows, each one with distinctive advantages, are developed to cater for differentrequirements of client and applicable to the building of new plants as well as renovation works.

• Equipments, pipes, pumps and valves made of XDS special alloy materials that are resistant to high temperature andconcentrated sulfuric acid and world class level with respect to corrosion rate and major mechanical parameters , all of whichallow long term and stable running of the system.

• By integrating process design, material development and equipment fabrication, Allgreen has managed to cut out the middleman, therefore not only quality, but also efficiency are guaranteed.

• All equipments involved in DWHS are home-made or fabricated, which is more in line with the local customs when it comes tooperation, consequently the prices are more competitive and technical services are more accessible.

• Allgreen has made various construction models to reduce construction cycle and cut down the expense.

• Allgreen has a complete after-sale service system.

Sulfuric acid based on iron pyrites

With backward technology, the sulfuric acid plants based on iron pyrites in China suffers small scale, poor environment, high energy consumption and poor economic performance. In response to this, Allgreen has introduced advanced DCS and developed technologies and large-sized equipments suitable to the sulfuric acid plant based on iron pyrites. By using technologies such as adiabatic evaporation and cooling process, enclosed pickling technology, turbulent washing and etc, flow gas is purified, therefore the volume of waste acid in need of treatment is reduced; the using of efficient catalyst and double conversion, double absorption process reduce the pollution caused by tail-gas; the low pressure steam produced by low temperature heat of acid cycling system increases the heat recovery rate and consequently improves the economic performance.

Sulfuric acid based on smelting exhaust gas

Based on domestic market, Allgreen has developed a mass of equipments and materials as well as technologies that are more economical, reliable and more adapted to the Chinese context in the field of sulfuric acid based on smelting exhaust gas. The reduction on the release of “three waste” is realized through the application of more efficient tail-gas scrubbing technology and advanced double conversion and absorption process which enhance the utilization of sulfur; the low pressure steam produced by low temperature heat of acid cycling system increases the heat recovery rate; great strides have been made in the upsizing of system, diversification of process as well as optimization of equipments, which all contribute to the stable running of the system.

Low temperature heat recovery of sulfuric acid based on smelting exhaust gas and iron pyrites

Low temperature heat recovery of sulfuric acid based on smelting exhaust gas and iron pyrites differ greatly from that based on sulfur in which the concentration of sulfur dioxide is high and water brought in by air is low, thus water can be used in dilutor for dilution that release a great amount of heat; for that based on smelting exhaust gas and iron pyrites, due to the existence of gas purification system, the gaseous sulfur dioxide entering drying tower is water saturated, the additional water input other than the DWHS system of sulfuric acid based on sulfur exceeds the capacity of water balance of the drying and absorption system.

Basing on the existing technology of DWHS of sulfuric acid based on sulfur, Allgreen has developed DWHS of sulfuric acid based on iron pyrites and smelting exhaust gas by substituting water injection with injection of 93%~96% sulfuric acid imported from drying and absorption section into dilutor so as to adjust the concentration of high temperature sulfuric acid entering the absorption tower of DWHS to be around 99%. Before the acid injection, the acid should be heated using the imported high temperature acid to raise the temperature of circulating acid in a bid to increase the heat recovery rate.

With the application of this technology, an extra of 0.4~0.5ton per ton of acid can be produced as by-product while the water consumption in drying and absorption section is reduced, the overall heat utilization ratio in sulfuric acid plants based on iron pyrites and smelting exhaust gas is increased.

Sulfuric acid based on hydrogen sulfide

Claus process is normally adopted to recover the sulfur when it comes to highly concentrated hydrogen sulfide whereas wet oxidation process is used for that with low concentration. The tail-gas from Claus process needs to be further treated while the outcome from wet oxidation process is less than satisfactory. In addition to the great amount of water brought in by combustion air, large quantity of water vapour is generated in the combustion of hydrogen sulfide amid the acidic gas with hydrocarbons. The attempt to remove the large amount of water generated in the combustion of acidic gas is closely related to acid production process. The dry process, employed by Allgreen, removes the water in the gas after combustion as much as possible using a method similar to that of sulfuric acid based on iron pyrites, which is to catalytic oxidize sulfur dioxide into sulfur trioxide following the scrubbing, dewatering, demisting and drying of gas, the sulfur trioxide is turned into sulfuric acid after absorption. This process is comprised of the following sections: the combustion of hydrogen sulfide, the cooling and dewatering of gas, the oxidization of sulfur dioxide, the drying of gaseous sulfur dioxide and the absorption of sulfur trioxide.

Refined sulfuric acid with high purity

Direct absorption process can be employed in the production of 98% refined sulfuric acid. Some converted gas can be imported from the outlet of 1st absorption tower of the main system followed by impurity removal using treater, afterwards the SO3 is absorbed by high purity sulfuric acid, the concentration of which is adjusted by high purity water, sulfur dioxide shall be removed from the end product which meets all specifications listed by chemically pure (CP) grade in GB/T625-2007. In case that EW-Ⅰgrade high purity water is used, the product quality can be expected to reach the specifications of analytically pure (AR) grade in GB/T625-2007. Sulfuric acid at analytically pure (AR) grade can be produced using Allgreen’ s proprietary technology, first to generate concentrated gaseous SO3 by evaporating oleum, then use sulfuric acid at analytically pure (AR) grade for absorption.

Others

In addition, Allgreen also possesses the following technologies: production of highly concentrated oleum, chlorosulfonic acid, molten sulfur dioxide, molten sulfur trioxide and etc as well as conversion of concentrated SO2, sulfuric acid based on cracking spent liquid, waste water treatment.

Acid based on Phosphogypsum

Make full use of the phosphogypsum by-product through wet phosphoric acid process, and after decomposition treatment, produce low-cost, high-quality sulfuric acid, so that the phosphogypsum acid-making technology reaches high level in China

The  main technical characteristics:    

• Using the most advanced sulfur, carbon reduction techniques to improve the conversion rate of the gypsum.

• Phosphogypsum using low-energy drying consumption techniques, the quality requirements of a wide range of phosphogypsum, high Production output.

• Using the most cutting-edge technology of calcination, the lowest energy consumption, improve energy recovery.

• Advanced cooling technology calcined flue gas cleaning, the flue gas to ensure that the subsequent process requirements.

• Using double-absorption process, maximize catalyst quality, improve the conversion rate, eliminating exhaust pollution.

• Using double-absorption process, maximize catalyst quality, improve the conversion rate, eliminating exhaust pollution.