JOLTE Phenol Plant

Executive Summary

Phenol is a desirable product, annually drawing $11.5 billion globally. Presently, most phenol on a global scale is produced by a multi-step cumene process that also produces equimolar amounts of acetone. This reaction is dangerous, energy intensive, and leaves phenol prices closely tied to those of acetone. The process proposed in this report utilizes one step oxidation of benzene by nitrous oxide over a zeolite catalyst to produce phenol.

Due to the extremely low boiling point of nitrous oxide and resulting bulk transport issues, nitrous oxide synthesis via ammonium nitrate was incorporated into the proposed process. By initial estimates, using feedstocks of ammonium nitrate and benzene to produce phenol is economically feasible. The proposed plant is designed to take approximately 0.4% of the global market for phenol, equating to 30,000 tonnes of phenol per year with a gross profit of $37.7 million per year.

In the proposed process, aqueous ammonium nitrate is heated to produce nitrous oxide, which is then mixed with benzene and fed to the phenol reactor. To achieve maximum production rates and selectivity, the ammonium nitrate reactor will use a mixture of nitric acid and ammonium chloride catalysts. The ratio of catalysts and the operating conditions of these reactions were chosen using experimental data to produce the highest possible yields while also considering process safety measures. The phenol reactor will use a zeolite catalyst and will operate at a phenol selectivity of 98% from benzene.

Catalytic and kinetic experimental data were compiled and used to construct a process diagram including all major and minor pieces of equipment required. The operating parameters were set based on desired product purity, reaction chemistry, and safety measures. Physical properties of the expected stream components dictated the operating conditions of the flash tanks and distillation columns, which are all within reasonable limits and can be viewed in Table 0.1.

Using the desired phenol purity of 99% and the established operating parameters, mass and energy balances were written and evaluated. These stream energies and total mass flow values were used to size and design all major pieces of equipment within the process. Detailed equipment data sheets were compiled for the phenol reactor, ammonium nitrate mixer, second distillation column, flash tank, and heat exchanger using Aspen and hand calculations, and the remaining pieces of equipment were sized and cost using the heat duties found from the energy balances. The total capital investment for the plant based on calculated equipment costs is $2,787,676.

Next, pinch analysis was conducted on four heat exchangers within the plant to help minimize the quantity of utilities required, thus reducing costs. Capital cost savings from implementing the heat integrated system are $29,182 and utility savings per year total $276,990, reducing the total utility costs for all heat exchangers in the plant by 40% and allowing for increased profit margins.

In order to further the capability of the plant outlined in this report, a process control structure was built for the phenol distillation column (T-102). This control structure is designed to control phenol purity by measuring distillate composition via an analyzer and temperature in the top of the column via a thermocouple and using this data to manipulate the reflux flowrate via a cascade control structure. In parallel with this, a liquid level controller for the bottom of the column and the reboiler responds to changes in liquid level caused by manipulations in the reflux flow rate by increasing or decreasing the flowrate of the bottoms product accordingly.

Relevant public health, safety, and welfare concerns were researched and addressed for both the proposed Mexico location and the secondary location in Australia. Due to environmental hazards and regulations regarding the release of carbon dioxide, carbon capture and storage technology will be implemented in the plant. This will help minimize the release of greenhouse gases and mitigate global warming and climate change. This also reduces JOLTE Chemical process wastes, and the removal of carbon dioxide from the nitrogen stream allows for nitrogen recycle into the regeneration reactor.

Many of the components in this process are fire and explosion hazards when exposed to high heat or ignition sources. Due to these concerns, workers will be required to wear fire resistant or retardant clothing to help protect themselves in the event of a fire or steam release. Control systems monitoring temperatures throughout the process will be utilized to ensure components and their mixtures stay under their flammability and explosive limits. To mitigate the explosive danger of ammonium nitrate, the thermal decomposition is facilitated in an aqueous solution with the assistance of catalysts. Inherently safer design is implemented by minimizing the quantities of ammonium nitrate that need to be stored on site.

Plots of suitably zoned land were also selected for each of the proposed locations. The selected Mexico location is 533 acres in Agua Prieta, Sonora, Mexico that costs $600,000. It is 11 miles from the US-Mexico border, making it easier to transport to the American market, and is also next to an electricity generation plant. The location is also relatively close to a large ammonium nitrate producer which will reduce raw material transportation costs. The plot of land found for the alternate phenol plant site location in Australia is a 90-acre plot zoned for general industry in Moama, Victoria and costs $665,566 USD.

Storage tanks were sized and costed for each raw material and product, and a scale plant layout was drafted using industry standards for equipment spacing and safety as well as determined equipment sizes. Ammonium nitrate storage tanks are 70 m from the plan boundary for the safety of the community, and the office and other populated spaces are the furthest from the ammonium nitrate hazards. Office and control buildings were sized based on calculated operator requirements of four per shift. On the basis that employees would work 49 weeks of the year, with five shifts per operator a week, an estimated total of 14 operators and 6 office employees was determined.

Economic analysis was conducted for this process, and it was determined that the plant is not profitable in its 30-year lifespan using discounted cumulative cash flow analysis. With any discount rate of over 3.423%, the economics do not break even within the lifespan of the plant