Sep-2024

Additised solvent closed-loop cleaning package (RI 2024)

Defouling process units in the refining sector can be tedious and time-consuming. Unit and storage cleaning is crucial to ensure better feed quality, but it can be costly and pose safety risks.

Kandanelli Ramesh, K B Dhiravidaselvi AND K R Krishna
HP Green R&D Centre, Hindustan Petroleum Corporation Limited

Article Summary

This article focuses on the removal and recycling of hard hydrocarbon deposits in refinery process and storage units. We introduce a novel and highly efficient additised solvent package that aids in dissolving tough condensed asphaltenic deposits. This methodology employs a chemical formulation that reduces facility downtime, minimises manual intervention, and ensures the recovery of 100% of the hydrocarbons. The recovered liquid is then processed further to extract valuable residual oil for various applications.

Process
Processing heavy crudes can lead to problematic asphaltene deposition in downstream units and storage tanks. Over time, these deposits condense and become hard, causing issues such as poor product quality, suboptimal unit performance, and increased maintenance and downtime. Generally, to restore the performance of these units, several cleaning cycles using aromatic solvents or manual intervention is required.

However, the execution of these methods can lead to production loss, unit downtime, loss of business opportunities, and safety issues. This often results in timely maintenance being postponed or taken up only upon complete breakdown of the process units or storage facility.

The additised solvent package developed by HP Green R&D Centre is a closed-loop cleaning solution. It converts sludge and deposits into processable oil, reducing environmental impact and downtime of units and tanks. The process is also economically viable, can be used for high-temperature operation, and is easily scaled up.

Case study 1: The propane deasphalting unit at HPC’s Mumbai refinery had issues meeting the quality requirements for the finished product in terms of colour and viscosity. The presence of condensed asphaltenic deposits in the extractor was suspected to be leaching into the consequent product streams, leading to poorer product quality as crude processing limitations. The conventional cleaning procedure using aromatic-rich extract solvent was unsuccessful in meeting the specifications of the product.

The additised cleaning package could defoul the extractors by dissolving the asphaltenic foulants and help meet the desired product specifications under optimum unit operating conditions. Compared to using a non-enhanced solvent, the amount of asphaltene removed increased by 70%. The unit downtime was also halved, providing operational flexibility.

Case study 2: A bitumen storage tank was due an outage as part of a tank farm revamping plan. The tank contained approximately 73.1 kl of condensed unpumpable bituminous sludge. The usual process using a regular light vacuum gas oil stream can only remove 10% of the hard bottom material, leaving the remaining 90% to be removed through mechanical and manual intervention. This is time-consuming, involves high-end mechanical equipment, and is labour-intensive. As a result, the regular process incurs significant costs and exposes workers to solvent-hydrocarbon mixtures.

The additised solvent package was able to convert 95% of the sludge into processable oil in one to two days of continuous operation. In comparison to non-additised solvent cleaning, the tank downtime also decreased from 45 days to just six to seven days. This closed-loop cleaning process benefitted from ease of operation, reduced manpower requirements, reduced hazardous waste generation, scalability of operation, and more. Thus, it is a comprehensive solution for removing condensed asphaltenic foulants from the bitumen storage tank.

Novel solution
The newly developed additised solvent package is a novel solution for converting heavy asphaltenic streams into processable oil within a closed loop without compromising safety and operational flexibility. It significantly enhances the asphaltene dissolving capacity of the solvent, resulting in thorough defouling and reduced downtime of units and tanks.

This short article originally appeared in the 2024 Refining India Newspaper, which you can VIEW HERE