State-of-the-Art PX 120

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By Dan Bolton

Every iteration in roaster design answers an internal quest to improve performance, but successful advances in engineering must also answer the external demands of the market.

Probat introduced this fall the PX120, a mid-sized gas-powered drum roaster that is significantly more energy efficient and offers roasters greater batch control and reproducibility. Roasters operating this class of machine rely on rich streams of data that enable an extensive recipe management. The best controllers are built with IT interfaces that are visual and responsive, permitting instant adjustments.

This next-generation roaster offers industrial functionality to specialty roasters. It retains the reliability of the firm’s 150 years of experience but re-imagines the roasting process from the vantage of efficiency, control, and compliance with strict air emissions regulations.

It meets the needs of the upper end of the specialty roasting segment, roasters that want both style and flexibility, said Dirk Brinker, executive vice president of sales. “To meet the needs of customers looking for stylish machines, we went back a little bit to the traditional design, away from the rectangular industrial look of the Neptune drum roaster,” he said.

The PX120 roaster is almost completely redesigned. It resembles a Probatone shop roaster but almost 80% of the machine components in the PX120 are new, according to product manager Oliver Böwing.

Recirculating 200 oC air, instead of intake at room temperature, results in up to 30% reduction in energy and therefore much less exhaust.

The goal was to optimize flow by minimizing leakage, explains Böwing. As a result, drum pressure is more easily maintained.

All driving motors are equipped with frequency converters to reduce energy consumption across a broad range of roasting times from six to 20 minutes.

The PX120, which roasts up to 480 kilos per hour in batches from 60 to 120 kilos, features an all-new recirculation scheme, according to Böwing.

A high-efficiency cyclone is part of this innovative new design. Airflow is rendered digitally in 3D using computational fluid dynamics (CFD) to minimize turbulence. The result is a system that reduces energy and prevents the return of particulates to the roasting chamber.

Precise control

A machine built with frequency converters to precisely manage flow rate and drum rotation, benefits from sophisticated digital controllers, according to Sebastian Fichthorn, head of software engineering and IT at Probat.

The PX120 offers an intuitive interface, with access to all relevant data and visualization typical of industrial-sized roasters. “This all-new easy to use web-based application permits roasters to modify airflow and temperature by touch. It makes it easy to compare and reproduce recipes,” he explains.

Data is stored in a local SQL database where it is easily accessed, but secure, making sharing recipes between identical machines easy, he said. Due to comparability between the individual recipes within the recipe management, the development of new roasting profiles and their optimization thus becomes easier. The system enables network connectivity to diagnose and service. While roasters keep their eye on the process managers can monitor activity, managing energy consumption, output, and productivity.

Showcase roasting

Brinker observes that the specialty coffee segment is growing globally but differs country by country. Specialty roasters in various important markets are expanding from several smaller machines to larger capacity. At the other end of the spectrum, larger industrial roasters are buying smaller equipment to better handle small lots. One thing specialty roasters have in common no matter where they work is the desire to showcase their machines, he said.

Specifications

Partial recirculation

Recirculating hot air is an obvious way to save energy — why waste BTUs continually heating air entering at room temperature to 500 oC?

But it is not as simple as just filtering out the chaff before blasting it back into the roasting chamber. For one thing, the basic characteristics of the air have changed. It exits the back of the drum dry, less dense and saturated in CO  (carbon monoxide). Probat’s method of partially recirculating air results in optimum between energy-saving and machine safety. During a roast the air is mainly recirculated in the system and just to prevent higher CO concentration the machines switches to open mode for a short period of time.

This results in less exhaust gases and lower heat output for the burner since the air returning to the chamber is pre-heated to about 200 oC. The volume of air supplying the roast is 1,300 Nm3/h; the exhaust is 1,550 Nm3/h. Cooling the coffee requires 4,800 Nm3/h.

Energy-saving exhaust modules are customized to meet stringent emissions requirements that vary from California to China.

The roasting system

There are seven major components: the hopper, high suction destoner, roaster, and burner, roasting air system, cooling air system, and exhaust air treatment. The temperature range is 300-500 oC.

The drum was redesigned for even bean pattern and homogenous roasting. It operates at a low flow rate, gently mixing the roasted product at high air temperatures to produce evenly colored light and dark roasts. Roasting times are flexible from 6-20 minutes and discharge is fast with even cooling.

Roaster control

PC-based HMI works with Siemens/Allen Bradley PLCs of the latest generation. Database recipe management integrates into Probat plant control system with a detailed overview of all batch protocols.

Exhaust air treatment

Several options are available. The exhaust can be directed through an afterburner to reduce odor and exhaust gases. The afterburner operates at temperatures up to 450 oC. Configuring an Afterburner with catalytic converter (precleaner) results in a significant reduction of unburned hydrocarbons and monoxide. Total carbon emissions are below 50 mg/m3.

Proforte operates without an additional burner at a much higher temperature range of 990-1100 oC that almost completely eliminates odors.Tests demonstrate carbon monoxide emissions below 100 mg/m3; nitrogen emissions below 350 mg/m3 and total carbon emissions below 25 mg/m3. Energy savings are up to 85%.