Process for preparing a hydrolysed lingnocellulosic material

In the process for the production of substantially dry, hydrolyzed lignocellulosic material from a source thereof which comprises:

• providing and maintaining a primary hydrolysis reaction zone at a temperature and a pressure sufficient to cause and support the hydrolysis of lignocellulosic material therein;
• providing saturated steam at said temperature and pressure in said primary hydrolysis zone;
• feeding hydrolyzable lignocellulosic material to said primary hydrolysis zone and bringing said lignocellulosic material to said hydrolysis conditions therein;
• hydrolyzing said hydrolyzable lignocellulosic material in said primary hydrolysis zone by contact with said saturated steam at a sufficient residence time to form a stream comprising steam and hydrolysis products;
• bringing said stream to an outlet of said primary hydrolysis zone;
• separating substantially hydrolyzed products of said lignocellulose from steam at said outlet, and feeding heated hydrolysis products, substantially separated from steam, to a secondary zone:
• maintaining said secondary zone at a pressure lower than the pressure in said primary zone;
• providing superheated steam bled from said primary zone in said secondary zone in effective contact with said flashed hydrolysis products at a temperature and a pressure sufficient to substantially dry said hydrolysis products;
• allowing said heated hydrolysis products to flash upon introduction into said lower pressure secondary zone, whereby reducing the water content thereof and increasing the water content of said superheated steam;
• recovering said dried hydrolysis products of lignocellulose;
• the method of controlling the energy in the system which comprises:
• introducing heat into said primary hydrolysis zone by heat exchange with a heat transfer fluid which has been externally heated;
• preheating said primary hydrolysis zone by contact with said externally heated fluid for a time sufficient to bring said primary zone to a temperature and a pressure sufficient to support and maintain the hydrolysis of hydrolyzable solid lignocellulosic material;
• after introduction of said hydrolyzable lignocellulosic material to said primary hydrolysis zone, maintaining said primary hydrolysis zone in substantial energy steady state by at least one of the following means:
• contact with further quantities of externally heated heat transfer fluid, addition of liquid water to said primary hydrolysis zone, bleeding steam from said primary hydrolysis zone, and removing solid, hot, hydrolyzed lignocellulosic material from said primary hydrolysis zone;
• providing at least part of said superheated steam in said second drying zone by flashing steam from the product of said primary hydrolysis zone during transfer thereof from said primary to said secondary zone;
• and
• at least partially maintaining the steam in said secondary drying zone in a superheated condition by heating such with a heat exchange fluid, and bleeding superheated steam from said secondary drying zone.