In kraft softwood mills, tall oil soap is a valuable by-product as well as a toxin in the wastewater treatment system. Thus it is necessary to properly manage foam and soap within the mill.

A.H. Lundberg ’s soap recovery system was developed for use in the kraft pulping process where immiscible liquids separate.

Soap Recovery System

Managing soap issue requires a number of steps including the handling and deaeration of foam, separation of soap from liquor, and the separation of liquor from soap. Once the soap is separated from the system, it should be kept separate and not remixed with the liquor. The A.H. Lundberg scope of supply for efficient soap recovery includes:

  • Foam breakers to break down problematic foam in black liquor tanks.
  • Soap interface level detection system for efficient hydraulic decanting of soap on black liquor.
  • Skimmer-launder vessels to separate and return any incidental liquor carry-over in the soap decanting process.

System benefits include:

  • Reduce operator attention of tank levels
  • Reduce environmental spill hazards
  • Improved tank product quality control
  • Low installed capital costs
  • Low maintenance costs

New technologies emerging from the by-product recovery of black liquor soap include conversion of the soap to bio-diesel fuel (SDRF process) and the extraction of other valuable by products such as sterols.

Bluekey Energy – SDRF Biodiesel Process

An innovative biodiesel process tailored for the kraft pulp & paper industry

Converting black liquor soap to biodiesel using Bluekey energy’s patented Soap Derived Refinery Feedstock (SDRF) process and A.H. Lundberg’s methanol purification technology adds new mill revenue to the already significant benefits of soap removal.

Soap removal provides the following benefits to the pulping process:

  • Decreased black liquor solids loading to the recovery boiler, resulting in increased production for mills that are recovery boiler limited.
  • Improved brown stock washing and reduced foaming.
  • Decreased evaporator tube fouling and blockage.
  • Lower volumes of soap accumulation in the black liquor storage tanks allow greater effective use of tanks for liquor storage.
  • Improved black liquor pumping and in general, improved house-keeping. Controlled removal of soap would reduce foam spillage to sewers and outfall.

Now, the soap can be converted into high value biodiesel and biofuel providing significant new revenue streams for the mill.

  • Revenue of up to $35 per ADT from the sale of biodiesel.
  • Displacement of natural gas or fuel oil with renewable biofuel.

The SDRF process is designed to be 100% compatible with existing Kraft mill processes:

  • Capital costs are optimal to a simple ROI of 24-30 months.
  • Operating costs are minimal. The SDRF process extensively accesses existing plant energy, chemical and environmental systems.
  • Environment impact is negligible. Chemical by-products from the SDRF process are compatible with black liquor and their return to the process decreases soda make up requirements.